DOI： 10.2494/photopolymer.34.495

DOI： 10.2494/photopolymer.34.491

DOI： 10.2494/photopolymer.34.485

DOI： 10.2494/PHOTOPOLYMER.34.401

Publishing type：Research paper (scientific journal)  

<p>Composite materials with polymers and inorganic fillers enable the preparation of a variety of functional polymer materials. In particular, composites with crystalline polymers and Ni microparticles (NiMPs) can be applied to thermoresponsive conductive materials which are called PTC (positive temperature coeffcient) materials. These materials are conductive around room temperature, and turn to insulators at high temperature. This phenomenon is induced by the volume expansion of the crystalline domains, therefore, the design of matrix polymers has been limited. Herein, we showed PTC phenomena by using polyacrylamide-based (co)polymers in lieu of crystalline polymers. Those materials showed PTC phenomena regarding conductivity probably owing to the hydrogen bonding, yet polyacrylamides are amorphous polymers.</p>

DOI： 10.1246/cl.200342

CiNii Article

Publishing type：Research paper (scientific journal)  

DOI： 10.1063/5.0027509

Publishing type：Research paper (scientific journal)  

© 2020 Author(s). Atomic hydrogen dry etching was used for microstructure fabrication. Photolithography was proposed and achieved by a dry development process using atomic hydrogen irradiation. The reaction system of poly(methyl methacrylate) mixed with molecular benzophenone was examined as a model system for a proof-of-concept study. Optical patterning was experimentally made on a thin layer of poly(methyl methacrylate) with benzophenone by UV light exposure with a photomask. The reaction system acted as a negative tone resist in the proposed process. Thus, a model system for a new atomic hydrogen dry development process was proposed and successfully demonstrated.

DOI： 10.1063/5.0027509

Publishing type：Research paper (scientific journal)  

<p>Composite materials with polymers and inorganic fillers enable the preparation of a variety of functional polymer materials. In particular, composites with crystalline polymers and Ni microparticles (NiMPs) can be applied to thermoresponsive conductive materials which are called PTC (positive temperature coeffcient) materials. These materials are conductive around room temperature, and turn to insulators at high temperature. This phenomenon is induced by the volume expansion of the crystalline domains, therefore, the design of matrix polymers has been limited. Herein, we showed PTC phenomena by using polyacrylamide-based (co)polymers in lieu of crystalline polymers. Those materials showed PTC phenomena regarding conductivity probably owing to the hydrogen bonding, yet polyacrylamides are amorphous polymers.</p>

DOI： 10.1246/cl.200342

CiNii Article

Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acs.jpcb.0c06932

Publishing type：Research paper (scientific journal)  

© 2020 American Chemical Society. Thermoresponsive phase separation mechanisms of aqueous poly(N-isopropylacrylamide) (PNIPAM) solutions were investigated using an optical tweezer combined with a Raman microspectroscope. A near-infrared laser beam (λ = 1064 nm) was focused into the solution to produce and trap a single polymer microdroplet under an optical microscope. The laser beam played two important roles: The first role is to locally heat the solution to induce phase separation in which numerous polymer microdroplets are generated around the focus, while the second one is to collect these microdroplets. Eventually, a single polymer droplet was stably produced and trapped at the focus. Our method enabled us to perform two types of microanalysis for the droplet. Analysis I is real-time monitoring the growth of the polymer droplets by which we can determine the growth rate of droplets. Analysis II is Raman microspectroscopy to reveal chemical components of the droplets. By means of these two analyses, we revealed important phase separation mechanisms in terms of stereoregularity (isotacticity) dependence. From analysis I, we show that droplet growth is governed by the Ostwald ripening mechanism and the growth is accelerated by increasing the isotacticity. From analysis II, we show that the gelation is promoted in the droplet (physical gel formation) with increasing isotacticity. Our technique should be a versatile tool to explore liquid-liquid phase separation mechanisms for various binary solution systems.

DOI： 10.1021/acs.jpcb.0c06932

PubMed

Publishing type：Research paper (scientific journal)  

<p>We have previously demonstrated that photoresist removal rate comparable to oxygen plasma is accomplished by optimizing the removal conditions with H radicals produced on hot metal filament surfaces from H₂/N₂ mixtures (H₂:N₂ = 10:90 vol%). N₂ gas was used to dilute the concentration of the H₂ gas and to reduce the risk of explosion. However, it is not clear how the dilution of H₂ by N₂ affects the removal rate. In this paper, we examined the relationship between the removal rate and the H₂ content; the flow rate ratio of H₂ to H₂+N₂. The removal rate increased with increasing the H₂ content. In addition, the removal rate increased with increasing the substrate temperature according to an Arrhenius equation, when the H₂ content was over 90%. However, below 60%, the removal rate decreased with increasing the temperature over 230 ± 5 ℃. Denaturation of photoresist, e.g. hardening and/or crosslinking, may be induced by substrate heating when the H-radical density is low. The removal rate decreases not only by the deficiency of H radicals but also by the denaturation of films in H₂/N₂ mixed systems.</p>

DOI： 10.2494/photopolymer.33.427

CiNii Article

Publishing type：Research paper (scientific journal)  

<p>We have previously demonstrated that photoresist removal rate is enhanced by adding a trace amount of O₂ to the atmosphere in which H radicals are produced from H₂ on a hot metal filament. In this case, not only H radicals but also O and OH radicals are produced. The populations of O and OH radicals are a few hundredth parts of that of H radicals, but these radicals must play important roles. It is not clear which radicals contribute more to the enhancement of the removal rate. We used He/O₂ mixtures in this study, instead of H₂/O₂, to produce O radicals without co-producing H and OH to make clear the contribution of O radicals on the removal rate. The removal rate increased slightly with increasing the O₂ additive amount when the filament was unheated. This may be caused by thermal oxidation. On the other hand, the removal rate with a hot filament decreased by the addition of O₂. In short, the removal rate is not enhanced by O radicals. The enhancement in H₂/O₂ mixtures must only be ascribed to OH radicals.</p>

DOI： 10.2494/photopolymer.33.433

CiNii Article

Publishing type：Research paper (scientific journal)  

<p>We have previously demonstrated that photoresist removal rate comparable to oxygen plasma is accomplished by optimizing the removal conditions with H radicals produced on hot metal filament surfaces from H₂/N₂ mixtures (H₂:N₂ = 10:90 vol%). N₂ gas was used to dilute the concentration of the H₂ gas and to reduce the risk of explosion. However, it is not clear how the dilution of H₂ by N₂ affects the removal rate. In this paper, we examined the relationship between the removal rate and the H₂ content; the flow rate ratio of H₂ to H₂+N₂. The removal rate increased with increasing the H₂ content. In addition, the removal rate increased with increasing the substrate temperature according to an Arrhenius equation, when the H₂ content was over 90%. However, below 60%, the removal rate decreased with increasing the temperature over 230 ± 5 ℃. Denaturation of photoresist, e.g. hardening and/or crosslinking, may be induced by substrate heating when the H-radical density is low. The removal rate decreases not only by the deficiency of H radicals but also by the denaturation of films in H₂/N₂ mixed systems.</p>

DOI： 10.2494/photopolymer.33.427

CiNii Article

Publishing type：Research paper (scientific journal)  

<p>Thermosetting hyperbranched polymers were synthesized by radical copolymerization of dodecyl methacrylate and ethyleneglycol dimethacrylate in the presence of an addition-fragmentation chain transfer agent, methyl 2-(bromomethyl) acrylate. The resulting polymers had a branched structure containing multiple end groups per one polymer chain. By changing the comonomer compositions and the stoichiometric ratio of the total comonomer to the addition-fragmentation chain transfer agent, the glass transition temperatures of the resulting hyperbranched polymers can be controlled in a wide range from -80 ℃ to 13 ℃. The hyperbranched polymer contains multiple vinyl groups, i.e., side-chain vinyl groups (methacryloyl group) derived from ethyleneglycol dimethacrylate unit and ω-end vinyl groups (2-methoxycarbonyl-2- propenyl group) generated by addition-fragmentation chain transfer. Therefore, the hyperbranched polymers underwent spontaneous polymerization above ca. 100 ℃, and exhibited thermosetting properties even in the absence of a radical curing agent. The glass transition temperatures of the hyperbranched polymers were significantly increased to 130 ℃ or higher by thermal curing at 180 ℃for 1 h.</p>

DOI： 10.11364/networkedpolymer.41.3_113

CiNii Article

Publishing type：Research paper (scientific journal)  

<p>We have previously demonstrated that photoresist removal rate is enhanced by adding a trace amount of O₂ to the atmosphere in which H radicals are produced from H₂ on a hot metal filament. In this case, not only H radicals but also O and OH radicals are produced. The populations of O and OH radicals are a few hundredth parts of that of H radicals, but these radicals must play important roles. It is not clear which radicals contribute more to the enhancement of the removal rate. We used He/O₂ mixtures in this study, instead of H₂/O₂, to produce O radicals without co-producing H and OH to make clear the contribution of O radicals on the removal rate. The removal rate increased slightly with increasing the O₂ additive amount when the filament was unheated. This may be caused by thermal oxidation. On the other hand, the removal rate with a hot filament decreased by the addition of O₂. In short, the removal rate is not enhanced by O radicals. The enhancement in H₂/O₂ mixtures must only be ascribed to OH radicals.</p>

DOI： 10.2494/photopolymer.33.433

CiNii Article

Publishing type：Research paper (scientific journal)  

© 2019 Wiley Periodicals, Inc. Graft copolymers show microphase separated structure as seen in block copolymers and have lower intrinsic viscosity than block copolymers because of a branching structure. Therefore, considering molding processability, especially for polymers containing rigid segments, graft copolymers are useful architectures. In this work, graft copolymers containing rigid poly(diisopropyl fumarate) (PDiPF) branches were synthesized by full free-radical polymerization process. First, synthesis of PDiPF macromonomers by addition-fragmentation chain transfer (AFCT) was investigated. 2,2-Dimethyl-4-methylene-pentanedioic acid dimethyl ester was found to be an efficient AFCT agent for diisopropyl fumarate (DiPF) polymerization because of the suppression of undesired primary radical termination, which significantly took place when common AFCT agent, methyl 2-(bromomethyl)acrylate, was used. Copolymerization of PDiPF macromonomer with ethyl acrylate accomplished the generation of the graft copolymer having flexible poly(ethyl acrylate) backbone and rigid PDiPF branches. The graft copolymer showed a microphase separated structure, high transparency, and characteristic thermal properties to PDiPF and poly(ethyl acrylate). © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2474–2480.

DOI： 10.1002/pola.29499

Publishing type：Research paper (scientific journal)  

DOI： 10.1002/pola.29499

Publishing type：Research paper (international conference proceedings)  

© 2019 Author(s). Photoresist removal method using hydrogen radicals produced by decomposing hydrogen on a hot-wire catalyst is one of an environmentally friendly methods. We examined the relationship between photoresist removal rate and its surface temperature and the surface element analysis for a tantalum catalyst. In this study, we considered an adaptability of the catalyst to the removal.

DOI： 10.1063/1.5124640

Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acsapm.9b00422

Publishing type：Research paper (scientific journal)  

1-Phenyl-3-pyrazolidone (PhP) having an active hydrogen was blocked by phenyl isocyanate derivatives to reduce its nucleophilicity, and the potential of the blocked PhP as a thermal latent reductant generating the organic reducing agent, PhP, was revealed for the first time. The degree of dissociation of the blocked PhP during heating in solution can be controlled by the steric hindrance of the isocyanate-blocking agents. The thermal latency of the blocked PhP for the sorbic ester-based polyperoxides, which undergo a serious reductive decomposition by PhP even at 30 degrees C, was investigated to accelerate the decomposition of the polyperoxides only at elevated temperatures. It was revealed that the stability of the polyperoxides was not significantly affected at 30 degrees C, and marked reductive decomposition of the polyperoxides together with thermal decomposition took place at elevated temperatures. For the block PhPs, which are highly compatible with the polyperoxides, the decomposition promotion effect increased with increasing the steric hindrance of the blocking agents, and the controlled decomposition of the polyperoxides was successfully achieved. Moreover, the addition of the blocked PhP resulted in the complete solubilization of sorbic ester-based cross-linked polyperoxides by heating, which was not able to be achieved without the blocked PhP. The performance of the debondable adhesive by using the sorbic ester-based cross-linked polyperoxides was improved by the addition of the blocked PhP, although hazardous isocyanate formation during the activation process may limit the practical application. Specifically, a faster decrease in the lap-shear adhesion strength by heating was accomplished. Furthermore, the same level of dismantlability was achieved in the wide range of heating temperatures and time, which is an important requirement for polyperoxides undergoing significant exothermic decomposition bringing about undesired temperature rise.

DOI： 10.1021/acsapm.9b00422

Publishing type：Research paper (scientific journal)  

<p>Resist removal phenomena using laser irradiation were compared in the novolak resist and the PVP. Thresholds for stripping from the Si wafer and damaged at the Si wafer were evaluated for the laser irradiating condition in the normal atmosphere and in the water. The PVP was found to be easy to be stripped as compared with the novolak resist. Only in the water, the photoresist material was completely stripped from the Si wafer surface. The size of the changed area by the laser irradiation for the PVP was approximately 2 times larger than that of the novolak resist. Time-resolved images were also acquired in 400 ns and 7500 ns after the laser irradiation. The scattering condition of the PVP in the removal process was completely different from that of the novolak resist.</p>

DOI： 10.2494/photopolymer.32.603

CiNii Article

Publishing type：Research paper (scientific journal)  

<p>We examined an environmentally friendly photoresist removal method using radicals produced by decomposing mixtures of hydrogen and oxygen on a hot iridium catalyst. We earlier reported that the decomposition of photoresists was hastened by adding oxygen gas to a hydrogen flow using a tungsten hot-wire catalyst. The rate increased with the oxygen additive amount up to about 1.0% and then decreased gradually. The decrease is caused by the catalytic poisoning of O atoms on the catalyst surface because of its poor oxidation resistance. In present study, we show that oxygen addition without catalytic poisoning is effective to increase the decomposition rate. The poisoning can be avoided by using an Ir catalyst. The decomposition rate increased with the substrate temperature. The rate also increased rapidly with increasing amounts of added oxygen to 1.0% and then the increase became more gradual. OH radicals must play an important role to hasten the decomposition reactions.</p>

DOI： 10.2494/photopolymer.32.609

CiNii Article

Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.tsf.2019.03.035

Publishing type：Research paper (scientific journal)  

© 2019 Elsevier B.V. For fabricating semiconductor devices and for microelectromechanical systems, photoresists are important materials supporting photolithography processes. However, photoresists must be removed for subsequent processes. An earlier study demonstrated that adding a small amount of oxygen gas to the atmosphere in which hydrogen radicals are produced increased the decomposition rate of a positive-tone novolac photoresist. For this study, we prepared polymers with different side chain structures based on poly(vinyl phenol) (PVP). We examined the effects of added oxygen and the oxygen-added hydrogen radicals on the decomposition rates of PVP-based polymers. Hydroxyl groups of PVP are partly substituted with tert-butoxycarbonyl groups in order to use for base polymer of KrF photoresist. Results show that oxygen addition can be useful for KrF photoresist removal.

DOI： 10.1016/j.tsf.2019.03.035

Publishing type：Research paper (international conference proceedings)  

© Published under licence by IOP Publishing Ltd. Poly(N-isopropylacrylamide) (PNIPAM) exhibits phase separation with lower critical solution temperature (LCST). In the 1990s, Masuhara and co-workers reported the first demonstration of optical trapping of PNIPAM forming a micrometer-sized polymer droplet. Since then, this technique has attracted much attention to create a molecular assembly in a microspace. In the present study, we targeted poly(N,N-diethylacrylamide) (PDEA), which has an analogous chemical structure to PNIPAM. We demonstrated that optical tweezers formed the unique micro-morphologies of a phase separated PDEA droplet. Fluorescence microscopic images and Raman spectra of the PDEA droplet showed that a lot of smaller-sized water-rich micro-domains were inhomogeneously formed in the droplet. Such unique phase separation behavior was never observed in steady-state heating of an aqueous PDEA solution above its LCST. Our results indicate that a novel micro-structure can be formed by coupling of an optical gradient force and a local temperature elevation.

DOI： 10.1088/1742-6596/1220/1/012034

Publishing type：Research paper (scientific journal)  

<p>Alternating radical copolymerization of cyclic conjugated diene monomers, i.e., cyclopentadiene and furan, with oxygen were carried out to generate degradable polyperoxides. The cyclopentadiene and furan based-polyperoxides consisted of different regiospecific structures. The regiospecificity of the alternating copolymerization was rationalized by the bond dissociation energies of the carbon-to-oxygen bond of the peroxy radicals based on density functional theory calculations. The thermal degradation behavior of the resulting cyclic conjugated diene-based polyperoxides was also investigated.</p>

DOI： 10.1246/cl.181047

CiNii Article

Publishing type：Research paper (scientific journal)  

DOI： 10.1246/cl.181047

CiNii Article

Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.polymdegradstab.2019.01.030

Publishing type：Research paper (scientific journal)  

© 2019 Elsevier Ltd The alternating copolymer of a conjugated diene monomer and oxygen, i.e., polyperoxide, is a main-chain degradable polymer and undergoes radical chain degradation by heating. During the degradation process, oxygen-centered radicals are formed and thus side reactions such as hydrogen abstraction from the polymer by the oxygen-centered radicals and subsequent coupling, which prevent the degradation, sometimes take place. In this study, in order to promote the degradation of polyperoxides only at elevated temperatures while maintaining their stability at ambient temperature, appropriate organic reductants, which do not significantly react with the polyperoxides at 30 °C but react at 100 °C, were explored. N,N-Dimethylaniline, which is a conventional reductant for redox initiation systems, initiated the redox degradation of cyclopentadiene-based polyperoxides even at 30 °C due to the very high nucleophilicity. The introduction of an electron donating group at the para position, i.e., 4-dimethylaminoacetophenone, 4-dimethylaminobenzaldehyde, and 4-dimethylaminobenzonitrile, successfully maintained the stability of the polyperoxide at 30 °C and accelerated the degradation at 100 °C due to the reduced nucleophilicity. Similar results were obtained by using 1-acetyl-2-phenylhydrazine and 1-phenyl-3-pyrazolidone (PhP) as a reductant, and PhP resulted in the most significant acceleration effect at 100 °C. The activation energy for the overall degradation of the polyperoxide in the presence of PhP was much lower than that of the polyperoxide in the absence of a reductant. In the case of sorbic ester-based polyperoxides, their stabilities at 30 °C were not maintained in the presence of the reductants and the stability was improved by increasing the 2,5 structure regarding the diene moiety in the main-chain.

DOI： 10.1016/j.polymdegradstab.2019.01.030

Publishing type：Research paper (scientific journal)  

<p>We examined an environmentally friendly photoresist removal method using radicals produced by decomposing mixtures of hydrogen and oxygen on a hot iridium catalyst. We earlier reported that the decomposition of photoresists was hastened by adding oxygen gas to a hydrogen flow using a tungsten hot-wire catalyst. The rate increased with the oxygen additive amount up to about 1.0% and then decreased gradually. The decrease is caused by the catalytic poisoning of O atoms on the catalyst surface because of its poor oxidation resistance. In present study, we show that oxygen addition without catalytic poisoning is effective to increase the decomposition rate. The poisoning can be avoided by using an Ir catalyst. The decomposition rate increased with the substrate temperature. The rate also increased rapidly with increasing amounts of added oxygen to 1.0% and then the increase became more gradual. OH radicals must play an important role to hasten the decomposition reactions.</p>

DOI： 10.2494/photopolymer.32.609

CiNii Article

Publishing type：Research paper (scientific journal)  

<p>Oxidative degradation of poly(ethylene glycol) (PEG) by ozone microbubbles (O₃MBs) was investigated in water. Ozone water are generally effective in oxidation reaction with a variety of organic compounds. O₃MBs have promise to improve the efficiency because it seems that O₃MBs generates hydroxy radicals, resulting in the higher active oxidative degradation. Herein, oxidative decomposition of PEG by O₃MBs in water was carried out and the products were characterized by ¹H nuclear magnetic resonance (NMR) and matrix assisted laser desorption/ionization fourier transform ion cyclotron resonance mass spectrometry (MALDI-FT-ICR-MS). Through the continuous struggles, decomposition of PEG was promoted by O₃MBs. It was found that O₃MBs with hydrogen peroxide added had the largest decomposition effect. The reason has been veiled yet, however, the author reasons that O₃MBs have promise as the novel degradation system.</p>

DOI： 10.2494/photopolymer.32.615

CiNii Article

Publishing type：Research paper (scientific journal)  

<p>Resist removal phenomena using laser irradiation were compared in the novolak resist and the PVP. Thresholds for stripping from the Si wafer and damaged at the Si wafer were evaluated for the laser irradiating condition in the normal atmosphere and in the water. The PVP was found to be easy to be stripped as compared with the novolak resist. Only in the water, the photoresist material was completely stripped from the Si wafer surface. The size of the changed area by the laser irradiation for the PVP was approximately 2 times larger than that of the novolak resist. Time-resolved images were also acquired in 400 ns and 7500 ns after the laser irradiation. The scattering condition of the PVP in the removal process was completely different from that of the novolak resist.</p>

DOI： 10.2494/photopolymer.32.603

CiNii Article

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

DOI： 10.1088/1742-6596/1220/1/012034

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acs.langmuir.8b02848

Publishing type：Research paper (scientific journal)  

© 2018 American Chemical Society. We studied the dependence on tacticity of the dynamic phase separation behavior of thermoresponsive poly(N,N-diethylacrylamide) (PDEA) in an aqueous solution. Using a laser temperature-jump technique combined with transient photometry, we determined the time constants of the phase separation and found that both atactic and isotactic-rich PDEAs had fast and slow phase separation processes (τfast and τslow). The fast process (τfast) was independent of the tacticity, irrespective of the concentration. On the other hand, the slow process had a strong dependence on the tacticity. We found the slow phase separation process got considerably faster with increasing isotacticity in dilute solutions. This effect due to the tacticity of the PDEA is totally different from that of poly(N-isopropylacrylamide) and can be explained on the basis of the difference between the hydrophobicity of atactic PDEA and that of isotactic-rich PDEA.

DOI： 10.1021/acs.langmuir.8b02848

PubMed

Publishing type：Research paper (scientific journal)  

Photoremovability of cross-linked polyperoxides was investigated considering the application to dismantlable adhesives. Applying lap-shear stress on the glass joints bonded by the cross-linked polyperoxides, i.e., the alternating copolymer of 2-hydroxyethyl sorbate and oxygen cross-linked by tolylene 2,4-diisocyanate, resulted in the failure of the glass adherend. UV irradiation on the bonded glass joints more than 19 J/cm² resulted in a significant decrease in the lap-shear adhesion strength due to the photodegradation of the cross-linked polyperoxides, and the bonded glass joints were successfully debonded without breaking the glass adherends. The failure mode was the cohesive failure of the adhesive and the residue of the cross-linked polyperoxides heavily adhered on the both debonded glass adherends. The additional photoirradiation on the debonded glass adherends in tetrahydrofuran resulted in the significant removal of the adhered cross-linked polyperoxide due to the further photodegradation. After 150 J/cm² irradiation, the adhesive residues were completely wiped off from the glass adherends.

DOI： 10.2494/photopolymer.31.511

CiNii Article

Publishing type：Research paper (scientific journal)  

Resist stripping phenomenon with laser irradiation was observed by using a time-resolved analysis. The time change of the resist stripping phenomenon by a probe laser irradiation was observed from the viewpoint of the intensity change of the probe laser. As for the laser irradiation in the water, the probe laser intensity arrived at the maximum after around 40 μs. During the pump laser irradiation of 8 ns, a large compressive stress of -10 MPa was confirmed inside the resist from the FE analysis results. The generation of this compression stress is important for starting the resist stripping process, and is thought to improve the resist removal efficiency.

DOI： 10.2494/photopolymer.31.413

CiNii Article

Publishing type：Research paper (scientific journal)  

Photoresist removal method using hydrogen radicals, which are produced on a tungsten hot-wire catalyst, is effective to resolve some environmental and industrial problems in conventional methods for the fabrication of electronic devices. However, its removal rate is not as good as that of the conventional ones. We have previously described that the removal rate of a positive-tone novolac photoresist is enhanced by the addition of a small amount of oxygen gas to the atmosphere, in which hydrogen radicals are produced. Oxidizing radicals, such as OH and O radicals, can be produced together with H radicals. In present study, we examined the effects of oxygen addition on base polymers of KrF and ArF photoresists: the former is poly(vinyl phenol) (PVP), and the latter is poly(methyl methacrylate) (PMMA). Effects of oxygen addition on PVP was confirmed, as was found for the novolac photoresist. On the other hand, the effects on PMMA were different from the cases of the novolac photoresist and PVP. Results were ascribed to the presence or absence of benzene rings, the properties of polymers and the reactivity of oxidizing radicals.

DOI： 10.2494/photopolymer.31.419

CiNii Article

Publishing type：Research paper (scientific journal)  

Surface properties of polymers such as wettability and adhesiveness play an important role in industrial applications. The properties can be enhanced by fabricating a mesoscopic structure to the surface. In this study, we examined a chemical etching which is a simple and direct technique for the surface profile control, using atomic hydrogen generated by hot-wire catalytic method. Several tens of nanoscale structures were fabricated on poly(methyl methacrylate) (PMMA) surface by atomic hydrogen irradiation, and the size and pitch of the structure could be controlled by reaction temperature and time. The wettability of PMMA film surface changed from hydrophilicity to hydrophobicity by formation of mesoscopic structures.

DOI： 10.2494/photopolymer.31.369

CiNii Article

Publishing type：Research paper (scientific journal)  

Thick film resist is applied to a template for microelectrode used in semiconductor device integration. Utilization of positive type resist in chemically amplified system for thick film is expected to improve production efficiency of semiconductor device integration, but improvement of resolution is required. In order to improve the resolution of chemically amplified positive tone thick film resist, chemical structure of the dissolution inhibitor (DI) was designed for the control of solubility in resist polymer. The increase of molecular size in DI improved the dissolution inhibiting ability for the resist polymer in the unexposed area and the high acidity of the deprotected DI having carboxyl group improved dissolution promoting ability for the resist polymer in the exposed area. The resist containing DI possessing a large molecular size and high acidity improved its sensitivity and resolution.

DOI： 10.2494/photopolymer.31.399

CiNii Article

Publishing type：Research paper (scientific journal)  

Polyacrylic acid (PAA) aqueous solution was treated with O₃ microbubbles and O₃ water, there was no difference in decrease in molecular weight of PAA due to the presence or absence of microbubbles. Regardless of dissolved O₃ concentration, O₃ microbubbles alone did not cause reduction in TOC and mineralization did not proceed. In the advanced oxidation proses with hydrogen peroxide added, the molecular weight and TOC decreased. It is considered that active oxygen is generated from hydrogen peroxide by advanced oxidation and PAA is decomposed. From these results, it is no considered generation of reactive oxygen species by microbubbles in the decomposition of PAA.

DOI： 10.2494/photopolymer.31.409

CiNii Article

DOI： 10.4325/seikeikakou.30.191

CiNii Article

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

DOI： 10.4325/seikeikakou.30.191

CiNii Article

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

DOI： 10.1117/12.2319560

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (international conference proceedings)  

© 2018 SPIE. Poly(N-isopropylacrylamide) solution, which is a representative thermoresponsive polymer, exhibits a phase separation with a formation of polymer-rich microparticles due to dehydration and aggregation of the polymer chains above a lower critical solution temperature (LCST). However, little is known about the details of polymer concentration in the particle. We have developed optical tweezers combined with confocal Raman microspectroscopy to analyze a hydration structure in a single polymer rich particle. A focused near-infrared laser beam produced the microparticle at the focal point due to an optical force and a photothermal effect. In this study, we investigated that molecular weight dependence of the polymer concentration in the polymer-rich particle by means of Raman microspectroscopy.

DOI： 10.1117/12.2319560

Publishing type：Research paper (scientific journal)  

© 2017 Taylor & Francis. The acrylic copolymers involving 2-hydroxyethyl acrylate (HEA) and tert-butyl acrylate (tBA) units as reactive units behave as pressure-sensitive adhesive type dismantlable adhesive materials. In order to clarify the individual role of HEA and tBA units on dismantlability, the 180° peel behavior after the dismantling treatment, i.e., heating in the presence of given amount of acid catalysts, was systematically investigated using the acrylic copolymers involving different amounts of the reactive units. It was revealed that transesterification of HEA units resulted in an increase in the cohesive force and modulus due to an increase in the molecular weight and cross-linking. Deprotection of tBA units, i.e., transformation of tBA to acrylic acid (AA) unit with isobutene evolution, promoted cross-linking by the esterification of AA units and tended to reduce a cohesive force by forming voids in the adhesive layer due to the evolution of isobutene gas. Interfacial failure in the peel tests corresponded with a high degree of cross-linking and increased modulus of the adhesive. Conversely, cohesive failure was associated with reduced cohesive strength of the adhesive layer and a low peel strength.

DOI： 10.1080/00218464.2016.1209114

Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.tsf.2016.12.013

Publishing type：Research paper (scientific journal)  

© 2016 Elsevier B.V. Mass spectrometry was used to identify the decomposition products of two typical photoresist polymers, Novolak and polymethylmethacrylate, by H atoms produced on hot wire surfaces. The production of CH4 and CO was confirmed for both polymers. Other possible products are C3H8, C4H10 or C4H8, and some esters such as CH3COOC2H5. The production of CO2, C2H4, C2H6, alcohols, and aromatics are minor. The possible decomposition mechanisms are discussed on the basis of density functional calculations of the energetics.

DOI： 10.1016/j.tsf.2016.12.013

Publishing type：Research paper (scientific journal)  

© 2017 The Society of Polymer Science, Japan (SPSJ) All rights reserved. The effect of the solvent evaporation rate and solvent type on the crystal formation of poly(vinylidene fluoride) (PVDF) prepared by spin-coating was evaluated over time. In the much-solvent-remaining state, the crystalline phase of PVDF changed in the order of α, γ and β with the increasing dipole moment of the solvent. In the almost-all-solvent-evaporated state, the crystalline structure of PVDF/hexamethylphosphoramide with a higher dipole moment was dominantly dependent on the evaporation rate and varied in the order of β, γ and α with the increasing solvent evaporation rate. However, PVDF/triethyl phosphate, having a lower dipole moment, always formed the α phase, regardless of the evaporation rate. The PVDF α phase in the concentrated solution state is difficult to transform into the β and γ phases because the potential energy of each PVDF crystalline phase increases in the order of α, γ and β. The PVDF crystalline phase in the spin-coating method is strongly affected by both the polymer-solvent electrostatic interactions and the evaporation conditions. From the results of the crystal transition behavior, it was experimentally supported that the potential energy of the PVDF crystalline structure increases in the order of α, γ and β.

DOI： 10.1038/pj.2016.116

Publishing type：Research paper (scientific journal)  

DOI： 10.1038/pj.2016.116

Publishing type：Research paper (scientific journal)  

DOI： 10.1246/cl.160907

CiNii Article

Publishing type：Research paper (scientific journal)   Kind of work：Single Work  

<p>The dissolution characteristics of a chemically amplified electron beam (EB) resist composed of partially <i>tert</i>-butoxycarbonyl group (<i>t</i>BOC) protected poly(<i>p</i>-vinylphenol)(PVP), a dissolution inhibitor, and an acid generator were investigated. The resist sensitivity was improved with decreasing <i>t</i>BOC ratio of the matrix resin. As the <i>t</i>BOC ratio increased, the resolution of the resist was better. SEM observation of the pattern profile was carried out to investigate the sensitivity and the resolution of the resist. The optimum <i>t</i>BOC ratio was 23.8％. As dissolution inhibitors, hydroquinone protected by a <i>tert</i>-butoxycarbonyl group(B-HQ) and isophthalic acid protected by a <i>tert</i>-butyl group(B-IP) are used. Dissolution inhibitors (B-HQ and B-IP) become dissolution promoters (HQ and IP) after exposure. The dissolution rate of the resist consisting of B-IP was faster than that of B-HQ in the exposed area. Pka of IP is smaller than that of HQ, and the acidity of IP is higher than that of HQ. Therefore IP enhances the solubility of the matrix resin in the alkaline developer. We evaluated the dependence of sensitivity of the resist upon acid generators. Triphenylsulfonium triflate, Diphenyliodonium triflate, Triphenylsulfonium antimonate, and Diphenyliodonium antimonate were used. When iodonium ion was used as cation, the sensitivity of the resist was better. When antimonate ion as anion was used, the sensitivity of the resist was better.</p>

DOI： 10.3769/radioisotopes.66.557

CiNii Article

Publishing type：Research paper (scientific journal)  

&emsp;Polymer composites filled with conductive particles such as metal, carbon black (CB) and nanotube (CNT) exhibit electro conductivity, and their resistivity significantly increases with raising temperature. Particularly, semicrystalline polymer composites possess superior electro conductivity and positive temperature coefficient (PTC) effect, because conductive particles effectively connect by localizing in the amorphous phase and disconnect by a greater volume expansion near the melting point. In this study, we quantitatively analyzed the PTC effect of various composites consisting of semi-or non-crystalline polymers filled with metal or carbon particles by calculating their filler contents considering thermal volume expansion rate and degree of crystal, as a guideline for design of sensor and circuit protection devices. The revised filler content at room temperature, <i>φ</i> (R.T.) of poly (vinylidene fluoride) (PVDF) / nickel, CB and CNT as semicrystalline polymer composites became higher than the amount of filler loading in preparation and drastically decreased as temperature increased. In contrast, <i>φ</i> (R.T.) of poly (methyl methacrylate)(PMMA) / CB and CNT as noncrystalline polymer composites gradually decreased with temperature. The rate of the revised filler content at PTC, <i>φ</i> (PTC) and <i>φ</i> (R.T.) at various amounts of filler loading in preparation was a constant value in each composite, and <i>φ</i> (PTC) / <i>φ</i> (R.T.) values of PVDF / Ni, PVDF / CB,PVDF / CNT. PMMA / CB and PMMA / CNT were 0.93, 0.78, 0.74, 0.95 and 0.96, respectively. These values indicate the filler content necessary to occurring PTC effect. In comparison of each <i>φ</i> (PTC) / <i>φ</i> (R.T.) value, semicrystalline polymer and carbon filler systems were lower. The results well represent the effect of particle localization in the amorphous phase of semicrystalline polymer and strong interaction of carbon nanofillers for the PTC characteristics.

DOI： 10.4325/seikeikakou.29.25

CiNii Article

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

DOI： 10.1155/2017/2983042

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

DOI： 10.1080/00218464.2016.1209114

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)   Kind of work：Single Work  

<p>We investigated the chemical structure of positive-tone novolak photoresists into which B, P, and As ions were implanted with doses of 5×10¹² to 5×10¹⁵ atoms/cm². The thickness of the surface-hardened layer of ion-implanted photoresists increased in the order As–P–B. The energy supplied from the ions to the photoresist concentrated on the surface side in the increasing order of B–P–As. The photoresists are exhibitting carbonization and/or cross-linkage attributable to the decrease in OH, CH, and O_1s and the increase in C=C, C_1s, and π-conjugated systems.</p>

DOI： 10.3769/radioisotopes.66.567

CiNii Article

Publishing type：Research paper (scientific journal)  

Photoresists play a key role in lithography processes for the fabrication of electronic devices, but must be removed after processing. The removal method using hydrogen radicals, which are produced on a tungsten hot-wire catalyst, is effective to resolve some environmental and industrial problems in usual methods. However, the removal rate is not as good as that of the usual methods. We have previously described that the removal rate is enhanced just by decreasing Hydrogen pressure but the rate limitations not clarified. In present study, we examined the removal rate dependence on the pressure and revealed that the upper limitation of the enhancement is achieved at 0.50 Pa. The removal rate at 0.50 Pa was 8.3 times higher than that at 20 Pa when the surface temperature was 250 ^oC.

DOI： 10.2494/photopolymer.30.297

CiNii Article

Publishing type：Research paper (scientific journal)  

© 2017 Masashi Yamamoto et al. We examined an environmentally friendly photoresist removal method using H radicals produced by decomposing hydrogen on a hot iridium catalyst. We examined the relationship between photoresist removal rate and its surface temperature using thin film interference and the removal properties using H radicals produced by the Ir catalyst. Decomposition behavior at polymer surface by radicals may be analyzed in further detail from the aspect of kinetics. Additionally, we investigated the oxygen addition effects on the removal rate. The photoresist removal rate increased with the oxygen additive amount and then decreased more gradually than in the case of using W filament. The increasing behavior was similar but there was a large difference between W and Ir catalyst in the decreasing behavior.

DOI： 10.1155/2017/2983042

Publishing type：Research paper (scientific journal)  

Hyperbranched polymers having a number of reductive disulfide bonds and radically reactive vinyl groups were synthesized by the bulk radical homopolymerization of bis(2-methacryloyloxyethyl)disulfide (disulfide based dimethacrylate, DSDMA) as a divinyl monomer in the presence of methyl 2-(bromomethyl)acrylate as an addition-fragmentation chain transfer agent. The resulting hyperbranched polymers (HB-DSDMAs) were photocured by irradiated at 365 nm in the presence of 2,2-dimethoxy-2-phenylacetophenone as a photo radical initiator. The photocured HB-DSDMA exhibited high transparency in the visible region and good solvent resistance for various organic solvents. Reduction of the disulfide groups smoothly proceeded in the presence of tributylphosphine as a reductant, and the cured HB-DSDMAs were completely solubilized. HB-DSDMAs were also photocured by irradiation at 254 nm due to the homolysis of the disulfide groups with subsequent initiation of the radical polymerization.

DOI： 10.2494/photopolymer.30.241

CiNii Article

Publishing type：Research paper (scientific journal)  

Three-component chemically amplified photoresists which are consisted of a base resin, a photo acid generator and a dissolution inhibitor are promising because the high sensitivity and the high resolution can be satisfied at the same time. We studied about the dissolution promotion effect of hydroquinone (HQ) in the exposed area. HQ is a model compound of the photo induced product of the dissolution inhibitor. We disclosed that HQ depressed a glass transition temperature (<i>T</i>g) of the base resin and the sensitivity was improved by enhancing the dissolution rate in the exposed area. It is expected that the dissolution rate was promoted when the post exposure bake temperature exceeded <i>T</i>g because the acid diffuse more easily.

DOI： 10.2494/photopolymer.30.281

CiNii Article

Publishing type：Research paper (scientific journal)  

Polyethylene glycol (PEG) in aqueous solution was decomposed by treating O₃ microbubbles and O₃ water. The molecular weight of PEG treated with O₃ microbubbles became lower, and the PEG degradation was enhanced in alkaline condition. PEG in aqueous solution was efficiently decomposed by reactive oxygen species generated by O₃ decomposition, and O₃ microbubbles promoted the O₃ decomposition in the interface of O₃ gas and surrounding water in which OH anion localized. PEG in aqueous solution was decomposed to inorganic oxygen by advanced oxidation process (AOP) of O₃ microbubbles and H₂O₂, and the reduction rate of total organic carbon (TOC) was over 70%.

DOI： 10.2494/photopolymer.30.285

CiNii Article

Publishing type：Research paper (scientific journal)  

<p>The lower critical solution temperature of thermo- and photo-responsive polymers, which involve coumarin units having functions for the dual-responsivity in chloroform, was controlled by the copolymerization. The cloud points of the copolymers of 7-methacryloyloxycoumarin with methacrylic acid and methyl methacrylate as solvophobic and solvophilic comonomers, respectively, were tuned below room temperature to nearly the boiling point of chloroform. The photodimerization of the coumarin units in the copolymer resulted in a decrease of the cloud points, i.e., photoresponsivity.</p>

DOI： 10.1246/cl.160907

CiNii Article

Publishing type：Research paper (scientific journal)  

Resist removal phenomenon with laser irradiation was analyzed by using a finite element (FE) method. Laser irradiation in the water can improve the resist removal effect as compared with that of normal atmosphere irradiation. A two-dimensional (2-D) micro-FE model was constructed based on the boundary surface between the Si wafer, resist and water during laser radiation. In the normal atmosphere, any effective stress did not occur along the x-axis direction in the resist. In contrast, for the laser irradiation in the water, large compressive stress was confirmed along the x-axis direction in the resist. This compressive stress in the resist is thought to improve the resist removal efficiency.

DOI： 10.2494/photopolymer.30.291

CiNii Article

Publishing type：Research paper (scientific journal)  

<p>We investigated the chemical structure of positive-tone novolak photoresists into which B, P, and As ions were implanted with doses of 5×10¹² to 5×10¹⁵ atoms/cm². The thickness of the surface-hardened layer of ion-implanted photoresists increased in the order As–P–B. The energy supplied from the ions to the photoresist concentrated on the surface side in the increasing order of B–P–As. The photoresists are exhibitting carbonization and/or cross-linkage attributable to the decrease in OH, CH, and O_1s and the increase in C=C, C_1s, and π-conjugated systems.</p>

DOI： 10.3769/radioisotopes.66.567

CiNii Article

Publishing type：Research paper (scientific journal)  

<p>The dissolution characteristics of a chemically amplified electron beam (EB) resist composed of partially <i>tert</i>-butoxycarbonyl group (<i>t</i>BOC) protected poly(<i>p</i>-vinylphenol)(PVP), a dissolution inhibitor, and an acid generator were investigated. The resist sensitivity was improved with decreasing <i>t</i>BOC ratio of the matrix resin. As the <i>t</i>BOC ratio increased, the resolution of the resist was better. SEM observation of the pattern profile was carried out to investigate the sensitivity and the resolution of the resist. The optimum <i>t</i>BOC ratio was 23.8％. As dissolution inhibitors, hydroquinone protected by a <i>tert</i>-butoxycarbonyl group(B-HQ) and isophthalic acid protected by a <i>tert</i>-butyl group(B-IP) are used. Dissolution inhibitors (B-HQ and B-IP) become dissolution promoters (HQ and IP) after exposure. The dissolution rate of the resist consisting of B-IP was faster than that of B-HQ in the exposed area. Pka of IP is smaller than that of HQ, and the acidity of IP is higher than that of HQ. Therefore IP enhances the solubility of the matrix resin in the alkaline developer. We evaluated the dependence of sensitivity of the resist upon acid generators. Triphenylsulfonium triflate, Diphenyliodonium triflate, Triphenylsulfonium antimonate, and Diphenyliodonium antimonate were used. When iodonium ion was used as cation, the sensitivity of the resist was better. When antimonate ion as anion was used, the sensitivity of the resist was better.</p>

DOI： 10.3769/radioisotopes.66.557

CiNii Article

Publishing type：Research paper (scientific journal)  

A simple method for preparing poly(vinylidene fluoride) (PVDF) films using antisolvent addition and controlling their crystalline structure was reported. PVDF was dissolved in HMPA, PC, GBL, DMAc, TEP and CHN at a concentration of 20 wt%. The dissolution process for each sample was 25-200°C for 1 day. These solutions were spin-coated on a three-inch Si wafer and the solution weight on the substrate was adjusted to 0.2?0.3 g using spincoating conditions. The samples were immersed in 500 ml of deionized water, which was used as the antisolvent for 3 min at 25°C. After immersion, the samples were removed from the deionized water and dried under atmospheric conditions. Crystalline structures of the PVDF films were evaluated by FT-IR and XRD. The weight of the PVDF film decreased with increasing evaporation time and was constant after 1 h. The slopes of the curves at the initial stage of evaporation were nearly identical, and the values of the HMPA, DMAc and TEP systems were 4.7, 4.4 and 5.7 mg min-1, respectively. The formation of porous structures presumably occurred via phase separation because of solvent exchange and diffusion of deionized water into the film. The findings indicate that the evaporation rates depended on the evaporation of deionized water diffused into the PVDF films.

DOI： 10.1038/pj.2016.62

Publishing type：Research paper (scientific journal)  

DOI： 10.1038/pj.2016.62

Publishing type：Research paper (scientific journal)  

DOI： 10.7567/JJAP.55.076503

Publishing type：Research paper (scientific journal)  

© 2016 The Japan Society of Applied Physics. We examined an environmentally friendly photoresist removal method using radicals produced by decomposing mixtures of hydrogen and oxygen on a hot tungsten catalyst. The photoresist removal rate increased with the oxygen additive amount (the flow rate ratio of oxygen to hydrogen) up to an optimal amount and then decreased gradually. When the catalyst temperature was 1600°C, the optimal oxygen additive amount was 1.0% and the removal rate was 1.7 times higher than that in the pure hydrogen system. At 2000°C, the optimal amount increased to 2.5% but the increase ratio decreased by 1.3 times. At high catalyst temperatures, the absolute removal rate as well as the optimal oxygen additive amount is high, but the increase ratio is low. At the optimal oxygen additive amount, H, O, and OH radicals may exert their effects together to decompose photosensitive polymers.

DOI： 10.7567/JJAP.55.076503

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

DOI： 10.1039/c6ra10677c

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Removal by using laser irradiation was investigated in Poly-Vinyl Phenol (PVP). The laser irradiation in the water can improve the PVP stripping effect as compared with that of normal atmosphere irradiation. The surface laser damage threshold of Si wafer was 0.13 J/cm², and the PVP stripping threshold was 0.06 J/cm². The PVP stripping threshold decreased to approximately 50 % of the surface laser damage threshold. The PVP strips from the Si wafer just as shown in a positive-tone DNQ / novolak resist. However, removal efficiency decreased at a large irradiation beam diameter. The stripped area decreases at the beam diameter of 1.5mm or more. Irradiation with multiple laser beams with a small beam diameter could improve the PVP stripping rate with high efficiency.

DOI： 10.2494/photopolymer.29.633

CiNii Article

Publishing type：Research paper (scientific journal)  

© The Royal Society of Chemistry 2015. Liquid marbles containing a sticky polyperoxide were prepared by the in situ copolymerization of the 1,3-diene monomer with oxygen. The as-prepared liquid marbles had a non-sticky nature and could move on any substrates due to the presence of hard particles on their surfaces, while the squeezed liquid marble developed adhesion force-tunable PSA properties due to the outflow of the inner materials. The 180° peel strength of the squeezed liquid marble increased by heating at 90 °C for 1 h or by UV irradiation at 0.86 J cm-2 because the cohesive force of the adhesive layer increased by the additional polymerization initiated by moderate decomposition of the polyperoxide. The increased 180° peel strengths were significantly decreased again to almost zero, i.e.; dismantling, after an additional heating at 150 °C for 1 h because of an excess increase in the cohesive force as pressure-sensitive adhesives, where cross-linking took place as a result of significant decomposition of the polyperoxide accompanied by hydrogen abstraction and coupling.

DOI： 10.1039/c6ra10677c

Publishing type：Research paper (scientific journal)  

We examined an environmentally friendly photoresist removal method using radicals produced by decomposing a mixture of hydrogen and oxygen on hot tungsten catalysts. Results show that the photoresist removal uniformity is enhanced remarkably with the optimal amount of oxygen addition. By further optimizing conditions, the removal uniformity and the inclusive removal rate might become comparable to those achieved when chemicals are used.

DOI： 10.2494/photopolymer.29.639

CiNii Article

Publishing type：Research paper (scientific journal)  

We need to enhance the removing ability of microbubbles through the clear understanding of the functional mechanisms of microbubbles for the removal of photoresist layers. The purpose of the present study is to clarify the effect of microbubble on the surface of photoresist layers.

DOI： 10.2494/photopolymer.29.643

CiNii Article

Publishing type：Research paper (scientific journal)  

We studied about an effect of temperature on degradation of polymers for photoresist using ozone microbubbles as an environmentally friendly cleaning technique. The dissolved ozone concentration of ozone microbubbles was decreased with the increasing temperature because the solubility of ozone gas was decreased and self-decomposition of ozone in water was promoted. While, the reactivity between ozone and novolak resin was increased with the increasing temperature. Consequently, novolak resin was most efficiently removed at around 23 ^oC. The activated energy for removal of novolak resin using ozone microbubbles was 23 kJ/mol determined from Arrhenius plots. Polyvinyl phenol was removed by ozone microbubbles, and its removal rate was comparable with that of novolak resin. Polymethyl methacrylate without C=C bond or benzene ring structure could not be removed by ozone microbubbles.

DOI： 10.2494/photopolymer.29.623

CiNii Article

Publishing type：Research paper (scientific journal)  

We investigated the formation of microstructure on the surface of Poly(methyl methacrylate) - based polymer (PMMA - based polymer), which is a polymer for the ArF photoresist, in decomposition process by using atomic hydrogen generated by a tungsten hot-wire catalyst.

DOI： 10.2494/photopolymer.29.629

CiNii Article

Publishing type：Research paper (scientific journal)  

DOI： 10.1039/c5cc07421e

Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.eurpolymj.2015.05.010

Publishing type：Research paper (scientific journal)  

© 2015 Elsevier Ltd. Abstract Thermoresponsive properties of poly(7-methacryloyloxycoumarin) (P1a) and its derivatives as homopolymers containing a photoreactive coumarin unit were systematically investigated. P1a showed a lower critical solution temperature (LCST)-type phase separation in dichloromethane, chloroform, and 1,1,2-trichloroethane. The temperature producing a 50% transmittance (Tc) of 0.1 wt% P1a in distilled chloroform was 26 °C, while the Tc value decreased to 21 °C in deuterated chloroform i.e., the deuterium isotope effect. The Tc values in chloroform were adjustable from 28 to 57 °C by the introduction of the ethyleneoxy spacer and the substitution of α-methyl group by hydrogen. While the polymers containing 4-substituted coumarins were soluble in chloroform and dichloromethane from 0 °C to their boiling points. In the distilled chloroform solution, the coumarin units in P1a underwent a [2 + 2] cycloaddition and the transmittance at 500 nm decreased from 98% to 29% at 25 °C by a 180-s photoirradiation (326 mJ/cm2, emission band at 365 nm).

DOI： 10.1016/j.eurpolymj.2015.05.010

Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.polymer.2015.01.057

Publishing type：Research paper (scientific journal)  

© 2015 Elsevier Ltd. Acetal-protected acrylic copolymers consisting of 1-isobutoxyethyl acrylate (iBEA), 2-ethylhexyl acrylate (2EHA), and 2-hydroxyethyl acrylate (HEA) repeating units were applied to the pressure-sensitive adhesive (PSA) types of dismantlable adhesives. The random and block copolymers with a relatively high HEA content showed good PSA properties before dismantling treatment. The deprotection of the acetal-protected group of the iBEA unit took place in response to individual external stimuli, soaking in boiling water and UV irradiation in the presence of a photoacid generator. The random copolymers containing an HEA unit of more than 10 mol% and an iBEA unit of more than 70 mol% achieved spontaneous debonding with interfacial failures at both the stainless steel and polyethylene terephthalate support film sides by soaking in boiling water within 10 min, whereas the corresponding block copolymer did not achieve interfacial failure even after a 20-min soaking. Photoirradiation of the random copolymers containing N-hydroxynaphthalimide triflate as a photoacid generator resulted in interfacial failures at both sides with a sufficiently reduced peel strength, where cross-linking arose due to the transacetalization and transesterification of a hydroxy group in the HEA unit along with deprotection.

DOI： 10.1016/j.polymer.2015.01.057

Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.tsf.2014.10.020

Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.tsf.2014.10.021

Publishing type：Research paper (international conference proceedings)  

© 2014 Elsevier B.V. All rights reserved. This paper discusses the decomposition processes of polymer thin films coated on silicon (Si) substrates by hydrogen radicals generated from H2 on hot-wire catalyst surfaces. N2 buffer was used to relax the translational motion of hydrogen radicals. It is shown that H atoms react to polymer films under thermal equilibrium conditions when the total pressure is 21.3 Pa and the distance between the catalyst and the substrate is 100 mm. Polymers with benzene ring such as phenol resin, polystyrene, poly(vinylphenol), and poly(α-methylstyrene) exhibited both low removal rate and high activation energy of decomposition compared to those polymers without benzene ring such as poly(methylmethacrylate) and poly(isobutylene). We concluded that benzene ring with CC bond and resonance structure is resistant to decomposition by hydrogen radicals.

DOI： 10.1016/j.tsf.2014.10.020

Publishing type：Research paper (international conference proceedings)  

© 2014 Elsevier B.V. All rights reserved. The relationship between the chemical structure of PMMA-type polymers and the removal rate by hydrogen radicals was examined. Hydrogen radicals are known to have superior reduction ability and can be generated by decomposing H2 on hot-wire surfaces. PMMA-type polymers, which are widely used as base polymers for ArF resist, have many variations with the difference in the substituents. The removal rate of the main chain scission type polymers was faster than that of the main chain cross-linking type polymers. In the main chain cross-linking type polymers, it is considered that reduction decomposition of polymer was inhibited apparently according to occurrence to simultaneously reduce decomposition by hydrogen radicals and main chain cross-link. The removal rate was slow in the case of the main chain scission type polymers with a benzene ring. We guessed that the polymer with a benzene ring was a stable structure by resonance stabilization of a benzene ring. We found that the removal rate was slow according to increasing bulkiness of α-side chain in the main chain scission type polymers. It is considered that etching resistance increases with increasing bulkiness of α-side chain of polymer.

DOI： 10.1016/j.tsf.2014.10.021

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

We have reported that multifunctional hyperbranched polymers are synthesized by radical homopolymerization of ethylene glycol dimethacrylate in the presence of methyl (2-bromomethyl)acrylate as an addition-fragmentation chain transfer agent. The hyperbranched polymers contain the pendant vinyl groups and the ω-end vinyl groups, and exhibit thermosetting properties in the absence of any catalyst. In this study, the initiation mechanisms for the thermal curing of the hyperbranched polymer were investigated by radical trapping using a nitroxide free radical. The hyperbranched polymer reacted with 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxy benzoate by heating at 150 °C showing that the curing proceeded by radical mechanism. The ¹H NMR analysis of the product revealed that the cleavage of Br－CH₂ bond and C －C bond adjacent to a vinyl group having relatively low bond dissociation energies has minor contribution to the radical formation and thermal curing proceeds by spontaneous polymerization of vinyl groups.

DOI： 10.11364/networkpolymer.36.186

CiNii Article

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

© The Royal Society of Chemistry 2015. Liquid marbles have been shown to be a novel micro-reactor to synthesize polyperoxides by the radical alternating copolymerization of the 1,3-diene monomer with oxygen in a good yield. Oxygen gas is effectively absorbed as a comonomer by the large and permeable gas-liquid interface of the liquid marbles.

DOI： 10.1039/c5cc07421e

Publishing type：Research paper (scientific journal)  

Instead of photoresist removal methods using chemicals, we investigated a novel, environmentally friendly removal method using atomic hydrogen generated on a tungsten hot-wire catalyst. We revealed that the photoresist removal rate is remarkably enhanced under low hydrogen pressure conditions. This enhancement may be ascribed to the high kinetic energy of H atoms. If we optimize the removal conditions, the removal rate may become comparable to that achieved when chemicals are used.

DOI： 10.2494/photopolymer.28.303

CiNii Article

Publishing type：Research paper (scientific journal)  

The existence of microbubbles in ozonized water has been shown to significantly enhance the photoresist removal rate due to an elevated dissolved ozone concentration and a direct effect of the microbubbles relating to the radical generation. Additionally, the ozone microbubble solution was able to effectively remove a high-dose ion-implanted photoresist, which is extremely resistant to removal by ozonized water and other wet chemicals because of its amorphous carbon-like layer, or “crust”. Electron spin resonance experiments were also performed without the influence of serious metal contamination and indicated the presence of hydroxyl radicals, which are thought to be formed by interaction of ozone with hydroxide ions adsorbed at the gas-water interface upon collapse of the microbubbles.

DOI： 10.2494/photopolymer.28.293

CiNii Article

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

It is numerically found that the atomization of LN₂ droplet is induced by shear flow between LN₂ and gaseous nitrogen (GN₂) flow. Sequentially, liquid to solid phase change is enhanced and solid nitrogen (SN₂) particle is continuously created by LN₂ droplet freezing. By using ToF-SIMS and XPS analysis for resist removal experiment, the obtained C film thickness of resist removal section is 0.2 nm. Therefore, the photo resist can be successfully removed by using cryogenic solid particulate spray method.

DOI： 10.2494/photopolymer.28.285

CiNii Article

Publishing type：Research paper (scientific journal)  

Dependence on the stripping efficiency to irradiating beam size was investigated in an advanced laser resist stripping method. The beam size on the resist surface was changed from 0.3 mm to 3.0 mm. An intensity shape of the laser beam was Gaussian shape. At a beam diameter of 0.3mm, the stripped resist area in a beam was 15 % of 0.01 mm². In the case of beam diameter of 3.0 mm, the stripped resist area in a beam was 5 % of 0.38 mm². The stripped area improves 38 times for scale-up of the beam area of 100 times. The resist stripping efficiency was thought to depend on the heat stress due to a temperature gradient between the beam center and the regions without laser irradiation. Irradiation with multiple laser beams by small beam diameter was confirmed as one of the methods for improvement of a resist stripping rate with high efficiency.

DOI： 10.2494/photopolymer.28.307

CiNii Article

Publishing type：Research paper (scientific journal)  

A significant effect of microbubbles on degradation of novolak resin could not be confirmed. Microbubbles efficiently dissolved ozone in solution, enhancing dissolved ozone concentration. By using ozone microbubbles, removal rate of novolak resin was enhanced. We expect that the effect of polymer degradation by microbubbles would be made more obvious by setting suitable conditions such as pH, ionic strength, and removal process.

DOI： 10.2494/photopolymer.28.299

CiNii Article

We have reported that multifunctional hyperbranched polymers are synthesized by radical homopolymerization of ethylene glycol dimethacrylate in the presence of methyl (2-bromomethyl)acrylate as an addition-fragmentation chain transfer agent. The hyperbranched polymers contain the pendant vinyl groups and the ω-end vinyl groups, and exhibit thermosetting properties in the absence of any catalyst. In this study, the initiation mechanisms for the thermal curing of the hyperbranched polymer were investigated by radical trapping using a nitroxide free radical. The hyperbranched polymer reacted with 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxy benzoate by heating at 150 °C showing that the curing proceeded by radical mechanism. The ¹H NMR analysis of the product revealed that the cleavage of Br－CH₂ bond and C －C bond adjacent to a vinyl group having relatively low bond dissociation energies has minor contribution to the radical formation and thermal curing proceeds by spontaneous polymerization of vinyl groups.

DOI： 10.11364/networkpolymer.36.186

CiNii Article

Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.polymer.2014.10.031

Publishing type：Research paper (scientific journal)  

© 2014 Elsevier Ltd. All rights reserved. The effect of the high order structure of an isotactic polypropylene (PP) composite on the resistivity of composites containing magnetically aligned Ni particles was studied. Only a small amount of particles needed to be added for the composite material to become conducting after heating while in a magnetic field. The Ni columns formed on applying the field were distorted by the formation of large PP spherulites. Changes to the crystallization process due to the addition of a nucleating agent gave rise to changes in the columnar structure, resulting in large changes in the resistivity of the composite material. Controlling the high order structure of the polymer matrix including its morphology is very important in order to be able to control the magnetically aligned Ni structure.

DOI： 10.1016/j.polymer.2014.10.031

Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.tsf.2014.04.062

Publishing type：Research paper (scientific journal)  

This paper discusses the removal of chemically amplified negative-tone i-line resist SU-8 using hydrogen radicals generated by the catalytic decomposition of H2 molecules in H2/N2 mixed gas (H2:N2 = 10:90 vol.%) using a tungsten hot-wire catalyzer. SU-8 resists with exposure doses from 7 to 280 mJ/cm2 were removed by hydrogen radicals, although the SU-8 removal rate was independent of the exposure dose. The SU-8 removal rate increased with both substrate and catalyzer temperature, in addition to a decrease in the distance between the catalyzer and substrate. A high removal rate for cross-linked SU-8 with an exposure dose of 14 mJ/cm2 of approximately 4 μm/min was achieved with a catalyzer to substrate distance of 20 mm, and catalyzer and initial substrate temperatures of 2400 and 165 °C, respectively. © 2014 Elsevier B.V.

DOI： 10.1016/j.tsf.2014.04.062

Publishing type：Research paper (scientific journal)  

DOI： 10.1038/pj.2013.95

Publishing type：Research paper (scientific journal)  

A chemically amplified three-component resist was prepared by adding a dissolution inhibitor as the third component in an X-ray resist, and its sensitivity and resolution were evaluated for the application in extreme ultraviolet (EUV) lithography. The chemically amplified three-component resist, which consists of a base resin, a photo-acid generator (PAG) and a dissolution inhibitor, achieved high sensitivity with an exposure dose below 10 mJ cm -2. Furthermore, the chemically amplified three-component resist exhibited higher resolution and sensitivity than a resist without a dissolution inhibitor. The dissolution inhibitor was converted to a dissolution promoter containing carboxylic groups by exposure to EUV light, and it acted as a plasticizer in the resist, resulting in facile diffusion of the protons generated from the PAG. Thus, novel EUV resists with high sensitivity and resolution could be designed utilizing chemically amplified three-component resist containing a dissolution inhibitor. © 2014 The Society of Polymer Science, Japan (SPSJ) All rights reserved 0032-3896/14.

DOI： 10.1038/pj.2013.95

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

DOI： 10.1021/ma402300z

Publishing type：Research paper (scientific journal)  

Free radical bulk and solution polymerizations of a divinyl monomer, ethylene glycol dimethacrylate (EGDMA), in the presence of methyl 2-(bromomethyl)acrylate as an addition-fragmentation chain transfer agent were investigated to synthesize thermally curable hyperbranched polymers by a one-step reaction. Soluble polymers were obtained up to high conversion of EGDMA, and the molecular weight and molecular weight distribution of the polymers increased with increasing EGDMA conversion. 1H NMR and MALDI-MS analyses revealed that the soluble polymers were obtained after the consumption of a considerable amount of the pendant methacryloyl groups, and one polymer chain contained a number of end groups indicating the formation of hyperbranched polymers. The isolated hyperbranched polymers underwent thermal curing above 110 C without curing agents, and the polymers having a large number of pendant methacryloyl groups resulted in a significant increase in glass transition temperature, i.e., from around room temperature to above 210 C. © 2014 American Chemical Society.

DOI： 10.1021/ma402300z

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

DOI： 10.7567/JJAP.53.02BB04

Publishing type：Research paper (scientific journal)  

DOI： 10.1038/pj.2013.75

Publishing type：Research paper (scientific journal)  

In this study, we quantified the solvent evaporation rate in the production of three poly(vinylidene fluoride) (PVDF) crystalline structures using the solvent casting method, the first known report on such quantification. The evaporation conditions of drying temperature and pressure for the solvent species during solvent casting were varied. The results indicated that the crystalline structures of forms I, II and III of PVDF were obtained when the solvent evaporation rates were <0.0001, >0.2 and between 0.03 and 0.00058 g min -1, respectively. From the above quantitative analysis, it was established that the crystalline structure of PVDF from solvent casting is predominantly determined by the solvent evaporation rate. © 2014 The Society of Polymer Science, Japan (SPSJ) All rights reserved.

DOI： 10.1038/pj.2013.75

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

DOI： 10.1117/12.2073477

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Laser resist stripping for the ion-implanted novolak resist was successfully performed without occurring laser damage to the Si wafer. In order for the advanced　laser resist stripping method to be successful, it is important for the pulsed laser beam to pass though the ion-implanted resist and absorb into the Si wafer surface. The novolak resists which are implanted with B, P, and As ions, respectively, were irradiated with a pulsed 532nm laser. Regardless of the implanted ion species and density, more than 74 % of the laser power was found to absorb into the Si wafer surface. For the laser irradiation of 1 pulse, the ion-implanted resist with a density of 5.0 X 10¹³ atoms/cm² was completely stripped in the same way as that of a non-implanted resist. The optical absorption of the resist surface increased as the density of the ion-implantation increased. In case of the ion-implanted resist with a density of 5.0 X 10¹⁵ atoms/cm², the resist was stripped by 20 pulses irradiation without occurring laser-induced surface damage. A scanning removal of the highly ion-implanted resist was also successfully stripped by using an optimized irradiation condition. A highly ion-implanted resist was continuously stripped by the scanning laser irradiation with 20 pulses.

DOI： 10.2494/photopolymer.27.237

CiNii Article

Publishing type：Research paper (international conference proceedings)  

© 2014 SPIE. Novolak resists which are implanted with B, P, and As ions, respectively, were irradiated with a pulsed 532nm laser. Regardless of the implanted ion species and density, more than 74 % of the laser power was found to absorb into the Si wafer surface. For the laser irradiation of 1 pulse, the ion-implanted resist with a density of 5.0×1013 atoms/cm2 was completely stripped in the same way as that of a nonimplanted resist. The optical absorption of the resist surface increased as the density of the ionimplantation increased. In case of the ion-implanted resist with a density of 5.0×1015 atoms/cm2, the resist was stripped by 20 pulses irradiation without occurring laser-induced surface damage. A scanning removal of the highly ion-implanted resist was also successfully stripped by using an optimized irradiation condition. A highly ion-implanted resist was continuously stripped by the scanning laser irradiation with 20 pulses.

DOI： 10.1117/12.2073477

Publishing type：Research paper (scientific journal)  

We evaluated the removal of polymers with various chemical structures using wet ozone, and investigated the reaction mechanism between wet ozone and polymers using fourier-transform infrared (FT-IR) and in situ FT-IR. The removal rate of poly(vinyl phenol) (PVP), which has a carbon-carbon double bond (C=C) in the side chain was lower than that of the novolak resin, which has C=C in the main chain. Poly(methyl methacrylate) (PMMA), which has no C=C, was not removed. It was considered that the ozone reaction is an electrophilic reaction, and the wet ozone should react with C=C with ease. The removal rate of PVP with rinsing was higher than that without rinsing. This result indicates that the reaction products remain on the Si wafer. However, in the novolak resin, there was no difference between with and without rinsing. It was considered that the main chain of the novolak resin was decomposed to gas by the reaction with wet ozone. In the FT-IR measurement of PVP, the peak intensity of C=O stretching of carboxylic acid increased with increasing wet ozone processing time. However, in the novolak resin, there was no difference between with and without rinsing. Moreover, the peak intensity of the C=O stretching of carboxylic acid did not increase with increasing wet ozone processing time after 10 s of wet ozone processing time. From the result of in situ FT-IR, in the removal of the novolak resin using wet ozone, the main chain of the novolak resin was decomposed, and the reaction products of the wet ozone and novolak resin (low-molecular-weight carboxylic acid) should change to CO2. © 2014 The Japan Society of Applied Physics.

DOI： 10.7567/JJAP.53.02BB04

Publishing type：Research paper (scientific journal)  

The formation of void between a PET support film and an adhesive layer is one of the reasons for the PET interfacial failure of B1 (PtBA_w-b-(tBA_x-co-2EHA_y-co-HEA_z)) after the dismantling. However, a major part of B1 specimens was occupied by pillar-like structures, even where PET interfacial failure was observed. It seems that the macroscopic morphology of adhesive layers is not only factors to determine failure modes. Although both R1 (P(tBA_x-co-2EHA_y-co-HEA_z) and the soft segment of B1 have much lower T_g than room temperature, their mechanical properties seems to be different after the dismantling treatment as being indicated by ΔC_p values. The fact that B2 is resulted in cohesive failure in spite of very low peel strength after the dismantling suggests the important role of cross-linking on cohesive force.

DOI： 10.2494/photopolymer.27.531

CiNii Article

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

DOI： 10.1038/pj.2013.53

Publishing type：Research paper (scientific journal)  

We analyzed control of the crystalline structure of poly(vinilydene fluoride) (PVDF) in a PVDF/poly(methylmethacrylate) (PMMA) blend by varying the polymer blend ratio (PVDF/PMMA=60/40, 70/30 and 80/20 wt%) and the heat-treatment temperature (160-210 °C) just after the polymer melt. We obtained PVDF (form I) limitedly by heat treatment at 185 and 190 °C after blending PVDF/PMMA 70/30 wt%. The samples produced under other conditions indicated PVDF (form II). Results of differential scanning calorimetry (DSC), polarized light micrography and light transmittance indicated that samples of PVDF/PMMA 70/30 wt% heat-treated at 185 and 190 °C exhibited high compatibility between PVDF and PMMA, respectively. In contrast, PVDF (form II) samples obtained in other conditions indicated lower compatibility. We assumed that PVDF crystalline structure became the structure of the PVDF (form I) according to decrease of the crystallization rate by the highest compatibility between PVDF and PMMA. Pure PVDF crystallized very fast, so PVDF (form I) cannot be developed from pure PVDF by simply controlling the heat-treatment temperature. © 2013 The Society of Polymer Science, Japan (SPSJ).

DOI： 10.1038/pj.2013.53

Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.cardfail.2013.08.046

DOI： 10.1016/j.cardfail.2013.08.046

Publishing type：Research paper (scientific journal)  

DOI： 10.1063/1.4823530

Publishing type：Research paper (scientific journal)  

This paper proposes a photoresist removal process that uses multibubble microwave plasma produced in ultrapure water. A non-implanted photoresist and various kinds of ion-implanted photoresists such as B, P, and As were treated with a high ion dose of 5 × 1015 atoms/cm2 at an acceleration energy of 70 keV; this resulted in fast removal rates of more than 1 μm/min. When the distance between multibubble microwave plasma and the photoresist film was increased by a few millimeters, the photoresist removal rates drastically decreased; this suggests that short-lived radicals such as OH affect high-speed photoresist removal. © 2013 AIP Publishing LLC.

DOI： 10.1063/1.4823530

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

The electrical properties of Ni particle dispersed high-density polyethylene (HDPE) or Poly(methyl methacrylate) (PMMA) composites depend both on its Ni content and the weight-average molecular weight (Mw) of its base polymer. Moreover, we suspect a different conduction mechanism for polymers with a different Mw. As expected, the resistivity at room temperature (ρl) decreases with increasing Ni content in HDPE/Ni and PMMA/Ni, because many conductive paths are formed with increasing Ni content. For equal Ni content in HDPE/Ni, ρL decreases, while the temperature of PTC effect increases with decreasing Mw. On the other hand, in PMMA/Ni composites, ρL decreased and the temperature of PTC effect increased with increasing Mw This tendency is opposite in HDPE/Ni composites. This can be explained with the different distribution of Ni particles in the polymer. SEM images show that Ni particles are unevenly distributed in HDPE/Ni, while it was uniformly distributed PMMA/Ni. Therefore, we think that in HDPE/Ni the change of the degree of crystallinity of polymers with different Mw influences the conductivity strongly. In amorphous PMMA/Ni, the difference in the viscosity after polymer melt strongly influences the conductivity. © 2013, The Society of Polymer Science, Japan.

DOI： 10.1295/koron.70.483

Publishing type：Research paper (scientific journal)  

TiO2 doped poly vinylidene fluoride (PVDF) sheets were prepared by a solvent casting process. Both PVDF and TiO2 powders were dissolved in N-N dimethylformamide (DMF) solution and then spin-coated onto the Si or glass substrate. The flexible TiO2 doped PVDF sheets are transparent and have PVDF II-type crystallinity. The TiO2 particles distribute in the PVDF sheet with cohesion. Photocatalytic pigment degradation was observed when the sheet was irradiated by UV-light. After 840 hours UV-light irradiation, a significant change in XRD patterns and FT-IR spectra of the TiO2 doped PVDF sheets was not observed, however, the sheets became cloudy because a sub-micrometer surface roughness was formed due to local photocatalytic decomposition of the PVDF structure. As a result, the photocatalytic rate of the pigment decreased because of UV-light scattering. © 2013, The Society of Polymer Science, Japan.

DOI： 10.1295/koron.70.496

Publishing type：Research paper (scientific journal)  

Conductive polymer composites filled with carbon or metal particles exhibit a positive-temperature-coefficient (PTC) of resistivity. In our previous studies, we speculated that only the volume expansion of polymers upon heating cause the PTC effect and we conducted quantitative analyses focusing on the decrease of the apparent filler content of the composites during volume expansion of polymers. Later, we found that PTC effect occurs when the conductive path is cut off due to crystal melting and volume expansion of the base polymer along with rising temperature. In this study, we analyzed the PTC effect of polyvinylidene fluoride (PVDF)/Ni composite quantitatively and found that the apparent Ni content (Cni(T)) decreases along with rising temperature. When CNi(T) becomes about 98% of the Ni content at room temperature (Cni-r.T.), the resistivity is 10 times of that at room temperature. When CNi(T) becomes about 96% of Cni-r.t., the resistivity exceeds 108 Ω·cm and the composites serve as insulators. In conclusion, we proved that, the Ni content is not constant when the PTC effect occurs. © 2013, The Society of Polymer Science, Japan.

DOI： 10.1295/koron.70.476

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

DOI： 10.1038/pj.2012.223

Publishing type：Research paper (scientific journal)  

Development of Ni particle dispersed poly(methylmethacrylate) composites exhibiting conductor/insulator transition by the positive temperature coefficient effect of electrical resistivity is described. The PTC effect of composites was explained by the above models, and so it was assumed that composites composed of amorphous polymer, which do not exhibit the melting phenomenon, do not exhibit the PTC effect. In fact, it was reported that poly(methylmethacrylate) (PMMA)/carbon black composites do not demonstrate the PTC effect, because, unlike crystalline polymers, amorphous polymers do not exhibit drastic volume expansion. In addition, the shape of the PTC curve is affected by the glass transition point, that is, the temperature at the maximum of the PTC curve might change. These results indicate that if the kinds of polymer, filler and filler content are optimized, composites composed of amorphous polymer, which do not have the melting phenomenon, can be expected to exhibit a PTC effect comparable to that of composites composed of crystalline polymer.

DOI： 10.1038/pj.2012.223

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.jbiosc.2012.11.017

Publishing type：Research paper (scientific journal)  

In a liquid-liquid interface bioreactor, fungal cells locate in a hydrophilic polyacrylonitrile microsphere layer on an aqueous-organic interface. In this article, effects of hydrophobicity of the interface on n-decane hydroxylation activity of Monilliera sp. NAP 00702 was examined. (-)-4-Decanol production was significantly enhanced to 132% by addition of polytetrafluoroethylene. © 2012 The Society for Biotechnology, Japan.

DOI： 10.1016/j.jbiosc.2012.11.017

Publishing type：Research paper (bulletin of university, research institution)  

Publishing type：Research paper (bulletin of university, research institution)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Poly(vinylidene fluoride) (PVDF) has three crystal structures: form I, II, and III. The relationship between the PVDF crystal structure and physical properties had not been investigated. We have previously reported that three crystal structures were made from a single solvent. In this study we evaluated the thermal, optical, and electrical properties of all three PVDF crystal structures which can be made by solvent casting using a single solvent. Light transmittance (wavelength: 800 nm, 33 mu m film thickness) was 93% (form II), 95% (form IQ), and 97% (form I). Melting point was 165 degrees C (form I), 174 degrees C (form II), and 173 degrees C (form III). The relative permittivity was 13 (form I), 6 (form III), and 11 (form III). From these results, we confirmed that the physical properties of PVDF depended on the difference in the crystal structure.

DOI： 10.1295/koron.70.489

Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.polymer.2012.10.046

Publishing type：Research paper (scientific journal)  

Composites containing carbon nano tube (CNT) or carbon black (CB) conductive particle filler have the special characteristics of positive-temperature-coefficient (PTC) effects of resistivity. We quantitatively studied the relationship between poly(vinylidene fluoride) (PVDF) polymer's thermal volume expansion and the PTC effects of PVDF/CNT and PVDF/CB. The equation to revise filler content at each temperature due to the considerable thermal volume expansion rate of PVDF polymer indicates that filler content decreased with rising temperature. The graphs of filler content at room temperature plotted against apparent filler content with PTC effect were linear and their slopes were constant. From these graphs, we can determine the filler content necessary to occurring PTC effects. For example, the CNT content was 89% at room temperature, and the CB content was 93%. To our knowledge, this study is the first to report such phenomena. © 2012 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.polymer.2012.10.046

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.procbio.2012.10.013

Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.jbiosc.2012.07.008

Publishing type：Research paper (scientific journal)  

The addition of anion-exchange resin microparticles into a polyacrylonitrile (PAN) ballooned microsphere layer drastically enhanced the fermentative activity of Trichoderma atroviride AG2755-5NM398 in an extractive liquid-surface immobilization (Ext-LSI) system. The production of 6-pentyl-α-pyrone (6PP), a fungicidal secondary metabolite, was 1.92-fold higher than the control (PAN alone). © 2012 The Society for Biotechnology, Japan.

DOI： 10.1016/j.jbiosc.2012.07.008

PubMed

Publishing type：Research paper (scientific journal)  

Fungal cells immobilized with ballooned polyacrylonitrile (PAN) microsphere (MS) on an interface between a liquid medium and a hydrophobic organic solvent efficiently catalyze various microbial transformations such as hydrolysis, reduction, hydroxylation, and epoxidation of lipophilic substrates dissolved in the organic phase (liquid-liquid interface bioreactor; L-L IBR). In this study, the electric charge of MS layer in the L-L IBR was modified by mixing 4 kinds of anion-exchange, 2 kinds of cation-exchange or a chelating resin microparticles, and applied to regio- and stereoselective subterminal hydroxylation of n-decane to (-)-4-decanol by Monilliera sp. NAP 00702. In general, the addition of cation-exchange and chelating resin microparticles into a PAN-MS layer led to the strong inhibition of fungal growth and hydroxylation activity. On the other hand, the addition of anion-exchange resin microparticles having moderate total capacity (≤1.00 meq/g) significantly increased hyphal growth and hydroxylation activity. Especially, the addition of IRA910CT microparticles (total capacity ≥ 1.00 meq/g) into a PAN-MS layer led to 1.6-fold increase of 4-decanol production. Thus, it was concluded that the moderate addition of anion-exchange resin microparticles into an MS layer in the L-L IBR system was effective to enhancement of fungal growth and hydroxylation activity. © 2012 Elsevier Ltd.

DOI： 10.1016/j.procbio.2012.10.013

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

DOI： 10.1143/JJAP.51.067101

Publishing type：Research paper (scientific journal)  

We performed experiments to elucidate the physical action of a steam-water mixture jet, which we have proposed as a promising, environmentally friendly tool for cleaning surfaces. Photoresist-coated silicon wafers were adopted as the target and the jet performance of resist removal was evaluated, with several parameters being varied. We found that the resist-removal performance improves as the thickness or the mechanical strength of the resist film decreases, resist-wafer adhesivity decreases, or jet duration increases. The results imply that the essential part of the resist removal by the jet is a physical process including peel-off, in contrast to the established techniques such as the batch cleaning method utilizing chemical reactions. The results also indicate that the physical impact of the jet can be controlled, which will be a significant advantage in applying the jet as a cleaning technique. © 2012 The Japan Society of Applied Physics.

DOI： 10.1143/JJAP.51.067101

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

This paper discusses the fabrication method of Poly(vinylidene fluoride) (I) crystal having excellent dielectric properties. We tried to control the crystal structure of PVDF in the blend films of PVDF and Poly(methyl methacrylate) (PMMA) prepared by solvent casting. PVDF/PMMA = 60/40wt.% blend was dissolved in DMF solvent at 120°C. After casting, the PVDF/PMMA blend films were baked at 150°C (B). Each film was quenched (Q) from melting state and then was annealed at 120°C (QA). As a result, we demonstrated that PVDF (I) crystal grows preferentially under the existence of PMMA. That the crystallization speed of the quenched and annealed PVDF/PMMA blend films (QA) with the blend ratio of PVDF/PMMA = 60/40 wt.% is comparatively slow and forms the PVDF (I) crystal. © 2012, The Society of Polymer Science.

DOI： 10.1295/koron.69.135

Publishing type：Research paper (scientific journal)  

This paper discusses the positive-temperature-coefficient effects of resistivity in Ni particle-dispersed poly(vinylidene fluoride) (PVDF) composites based on experiment results from SEM, DSC, and pressure-volume-temperature (PVT) measurements. The melting points of composites with Ni content of 20, 30, 40, and 50vol.% were equal to that of pure PVDF. The PTC effects in composites with Ni content of 40 and 50vol.% occurred at temperatures near the melting point of the PVDF matrix, whereas those in composites with Ni content of 20 and 30vol.% occurred at temperatures below the melting point of the PVDF matrix. We found that the PTC effect occurs even without melting of the matrix polymer. Moreover, we determined that a slight increase in specific volume at temperatures below the melting point of the matrix polymer acts fully as a driving force for forming a gap between fillers. This suggestion was backed up by theoretical analyses using percolation theory and a thermal-fluctuation- induced tunneling model. © 2012 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.polymer.2012.02.048

Publishing type：Research paper (scientific journal)  

We discuss the effect of prebake temperature on the development characteristics of the positive-tone novolak resin/diazonaphthoquinone (i.e., Photoactivecompound = PAC) resists. Relationships between initial film thickness and sensitivity (E th) of resists with various prebake temperatures were investigated, and multiplex interference and bulk effect were estimated from results of Swing curves of resists. When the prebake temperature is from 80 to 130°C, the sensitivity of resists became lower with rising prebake temperature. Peculiarly, it was observed that the sensitivity of resists degrades remarkably when the prebake temperature is higher than 120°C. On the other hand, the multiplex interference and the bulk effect were independent of prebake temperature. Results of photosensitive parameters (A, B, C) for resists with difference prebake temperatures show that PAC absorption of exposure light (A), resist absorption after exposure (B), and photodegradative rate of PAC (C) were all constant even with differences of prebake temperature. FT-IR and DSC measurements showed no changes in chemical structures of novorlak resin and PAC. The amount of residual solvent in resist film decreased with rising prebake temperature. Peculiarly, the amount of residual solvent at prebake temperatures over 120°C was less than that at prebake temperatures under 120°C. Therefore, we concluded that the sensitivity of the resists becomes lower with rising prebake temperature because the hardness of the resist film increases due to decreases of residual solvent amount because of the rise of prebake temperature. © 2012, The Society of Polymer Science, Japan.

DOI： 10.1295/koron.69.77

Publishing type：Research paper (scientific journal)  

DOI： 10.1155/2012/937928

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DOI： 10.1117/12.916037

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DOI： 10.2494/photopolymer.25.741

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DOI： 10.1117/12.916033

Publishing type：Research paper (scientific journal)  

DOI： 10.4028/www.scientific.net/SSP.187.85

Publishing type：Research paper (scientific journal)  

DOI： 10.1117/12.977338

Publishing type：Research paper (international conference proceedings)  

In a recent study, we measured the exposure and development characteristics of five types of novolak resists with varying photoactive compound (PAC) concentrations. This report presents measurement results, as well as results of comparisons of patterns and process margins, obtained using the PROLITH lithography simulator. We also used PROLITH to investigate the effects of PAC concentrations on the swing ratio. Both experiment and simulation confirm that increasing PAC loading results in improved exposure latitude and reduced feature size swing ratio. © 2012 SPIE.

DOI： 10.1117/12.916037

Publishing type：Research paper (scientific journal)  

Laser resist stripping (1) for the positive-tone diazonaphthoquinone (2)/novolak resist (3) was successful without an occurring the laser damage (5) to a Si wafer (6). The fundamental (1064 nm) of pulsed Nd:YAG laser irradiation (4) in the water can improve the resist stripping effect as compared with that of atmosphere irradiation. In the case of the laser irradiation in water, the heat that occurred at Si wafer surface reaches the water on the resist surface across a thin resist layer. The effect of this heat occurs at the interface between resist surface and the water. By momentary cubical expansion of the water at the resist surface, the resist catches the pressure from water. The water on the resist surface will be worked like a wall rejecting a pressure. The resist stripping effect in the water condition was thought to improve by both thermal expansion of the Si wafer and pressure from the water. And also, a laser irradiation of 532 nm having large photon energy was found to be higher resist stripping efficiency than that of the wavelength 1064 nm. © 2012CPST.

DOI： 10.2494/photopolymer.25.741

Publishing type：Research paper (international conference proceedings)  

We investigated removal of chemically amplified negative-tone i-line resist SU-8 using hydrogen radicals, which was generated by the catalytic decomposition of H2/N2 mixed gas (H2:N2 = 10:90vol.%) using tungsten hot-wire catalyzer. SU-8 with exposure dose from 7 (Dg100×0.5) to 280mJ/cm2 (Dg100×20) were removed by hydrogen radicals without a residual layer. When the distance between the catalyzer and the substrate was 100mm, the catalyzer temperature was 2400°C, and the initial substrate temperature was 50°C, removal rate of SU-8 was 0.17μm/min independent of exposure dose to the SU-8. Finally, we obtained high removal rate for SU-8 (exposure dose = 14mJ/cm2 (Dg 100)) of approximately 4μm/min when the distance between the catalyzer and the substrate was 20mm, the catalyzer temperature was 2400°C, and the initial substrate temperature was 165°C. © 2012 SPIE.

DOI： 10.1117/12.916033

Publishing type：Research paper (international conference proceedings)  

We performed two experiments on resist-coated wafers. In the measurement of the resist-wafer adhesivity, we confirmed that it is significantly increased by an HMDS layer in between. In the resist-removal experiment using steam-water mixed spray, we found that the area of resist removal is limited within the area of spray application if HMDS is used, otherwise the former can be larger than the latter. These results suggest that the resist removal from a wafer surface by steam-water mixed spray is essentially a peel-off process. © (2012) Trans Tech Publications.

DOI： 10.4028/www.scientific.net/SSP.187.85

Publishing type：Research paper (international conference proceedings)  

Positive-tone diazonaphthoquinone/novolak (DNQ/novolak) resist was stripped from Si wafer by using a pulsed laser beam from visible to near infrared. Silicon wafer with resist was sunk in water to utilize irradiated laser energy effectively. When the resist was irradiated with the fundamental wavelength of the Nd:YAG laser, the resist was stripped from the Si wafer. No damage could be detected from the processed silicon wafer surface. The resist stripping effect in water condition was improved due to both the thermal expansion of the Si wafer and pressure from water. And also, laser irradiation of wavelength 532 nm, having large photon energy, was found to have a higher resist stripping effect than that of wavelength 1064 nm. © 2012 SPIE.

DOI： 10.1117/12.977338

We investigated the removal of polymers with various chemical structures and the removal of ion-implanted resists using wet ozone. The removal rates of polymers that have carbon-carbon (C-C) double bonds in the main chain were high. The main chain of these polymers may be decomposed. The removal rates of polymers that have C-C double bonds in the side chain were low. The benzene ring in the side chain changes into carboxylic acid, so their ability to dissolve in water increased. The polymers without C-C double bonds were not removed. Removal of B and P ion-implanted resists became difficult with increasing acceleration energy of ions at implantation. The resist with plastic-deformation hardness that was twice as hard as that of nonimplanted resist should be removed similarly to nonimplanted resist. Using TOF-SIMS, we clarified that the molecule of cresol novolak resin was destroyed and carbonized by ion implantation. © 2012 Hideo Horibe and Yousuke Goto.

DOI： 10.1155/2012/937928

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (international conference proceedings)  

The crystallinity, electrical, and optical properties of the ferroelectric/fluorescent oxide structures using sol-gel-derived (Ba 0.6Sr0.4)TiO3 (BST) and (Sr 0.8Eu0.2)Bi2.2Ta2O9 (Eu-SBT) grown on STO(110) single crystal substrates were introduced for the first time. In the present structures, the SBT films partly included a (116)-oriented Eu-SBT crystallite. The polarization vs. voltage characteristics of the BST/Eu-SBT structures showed the hysteresis loop caused by spontaneous polarization reversal, and then several emission peaks from Eu3+ ion were observed in a photoluminescence spectrum of a present BST/Eu-SBT structure. © 2012 Materials Research Society.

DOI： 10.1557/opl.2012.260

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

DOI： 10.1295/polymj.PJ2008171

Publishing type：Research paper (scientific journal)  

Poly(vinylidene fluoride) (PVDF)/poly(methylmethacrylate) (PMMA) blend nanofibers were prepared by electrospray deposition (ESD). To control the diameter, morphology, and crystalline structure of nanofiber, the effects of the blending ratio and the humidity during ESD were investigated. The increase in the PVDF blending ratio reduced the average fiber diameter and enhanced formation of crystalline structure. In particular, ESD process enhanced crystal formation of PVDF in high-PVDF blending ratio. High humidity reduced the formation of beaded fiber and increased the average fiber diameter. These results provide fundamental information for preparation of the smooth and crystalline PVDF/PMMA blend nanofiber by ESD. © 2009 The Society of Polymer Science.

DOI： 10.1295/polymj.PJ2008171

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

Publishing type：Research paper (scientific journal)  

We studied the association of six common polymorphisms of four genes related to lipid metabolism with serum lipid levels. We selected single-nucleotide polymorphisms (SNPs) in the genes for cholesteryl ester transfer protein (CETP), lipoprotein lipase (LPL), hepatic lipase (LIPC), and apolipoprotein CIII (APOC3), and studied 2267 individuals randomly selected from the participants of Serum Lipid Survey 2000. There was a significant association of CETP polymorphism (D442G, lnt14 +1 G -&gt; A, and TaqIB), LPL polymorphism (S447X), and LIPC polymorphism (-514 -&gt; CT) with HDL-cholesterol levels. We also found a significant association of LPL polymorphism (S447X) and APOC3 polymorphism (Sstl) with triglyceride levels. This is the largest database showing the association of common genetic variants in lipid metabolism with serum lipid levels in the general Japanese population. Further study is necessary to elucidate the role of these gene polymorphisms in cardiovascular events.

Publishing type：Research paper (international conference proceedings)  

The halftone mask is used in the lithography process to reduce the number of LCD manufacturing. Since the resist is exposed in the part in which the sensitivity curve rises, the problem is that the resist film thickness drastically fluctuated when the exposure dose to the resist slightly fluctuated. We used the low sensitivity resist as a lower layer, and high sensitivity resist as an upper layer. However it was not possible to produce the film thickness stably only by optimizing the bake condition of the two-layered resist, because the two resists blended at the interface. Therefore we added a water-soluble intermediate layer film (poly (acrlylic) acid 8wt% / dodesylbenzensulfonic acid 0.48wt% water solution) between the two resists, and the fluctuation problem of the resist film thickness due to the slight variation of the exposure dose was eliminated.

Publishing type：Research paper (international conference proceedings)  

The halftone mask is used in the lithography process in LCD manufacturing, and the manufacturing process number is reduced. By the use of the halftone mask, the exposure dose to the resist is adjusted, and three kinds of resist film thickness are produced. However the resist is exposed in the part in which the sensitivity curve rose by the halftone mask. When the exposure dose to the resist slightly fluctuated, the resist film thickness drastically fluctuated. This time, we used two kinds of the resist having different sensitivities. The lower layer resist has low sensitivity and the upper layer resist has high sensitivity. As a result, the sensitivity curve had the horizontal part. Though we applied two resists which optimized the bake condition, the horizontal part was not obtained. We thought that two resists mixed. We added a water-soluble intermediate layer film between two resists, and it became possible that the variation of the resist film thickness by the slight variation of the exposure dose was eliminated.

Publishing type：Research paper (scientific journal)  

Book type：Scholarly book

Book type：Scholarly book

Book type：Scholarly book

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We have investigated the removal of poly vinyl phenol (PVP) into which was B, P and As ions implanted with a dose of 5×1013~5×1015 atoms/cm2 at 70keV, using wet ozone. Also, we investigated the thickness of altered layer of ion-implanted PVP using Secondary Ion Mass Spectrometry (SIMS). We investigated the chemical reactivity of wet ozone and ion-implanted PVP by FT-IR. The removability of ion-implanted PVP using wet ozone decreased with increasing dose because the degrees of alteration of benzene ring and O-H group increase with increasing dose. From the results of SIMS, the thickness of altered layer of B-ion-implanted PVP was 387nm, that of P-ion-implanted PVP was 232nm, and that of As-ion-implanted PVP was 142nm. However, the degree of alteration should increase in order of B, P and As, because any samples were implanted at same acceleration energy (70keV). FT-IR indicated that benzene ring content percentage was almost same at removed and not removed. On the other hand, in O-H group, there is a clear difference at removed and not removed, O-H group content percentage decreased drastically at implanted PVP with a dose of 5×1014 atoms/cm2 over. Therefore, the removability of ion-implanted PVP using wet ozone depends on O-H group content than that of benzene ring. © 2013 SPST.

DOI： 10.2494/photopolymer.26.467

Publishing type：Article, review, commentary, editorial, etc. (scientific journal)  

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We examined the relationship between the development temperature and the resist properties of the positive-tone novolak resist. The resolution of the resist became higher with increasing development temperature, because the dissolution rate in exposure area was promoted by an acid-base neutralization reaction, and the dissolution rate in unexposed area was suppressed by an azo-coupling reaction with the photosensitive agent. When the development temperature was 22.5°C, the resist showed the best sensitivity. If the development temperature was lower, the dissolution rate of resist becomes lower by suppressing the acid-base neutralization reaction. If the development temperature was higher, the dissolution rate of resist becomes lower because an azo-coupling reaction which is caused the remaining photosensitive agent in exposed area. The resolution of resist becomes higher with increasing the development temperature, but Eth, becomes higher along with it, and the sensitivity of resist becomes lower. Thus, we concluded that the best suitable resist development temperature (17.3°C∼40.0°C) is 22.5 °C, taking into account the trade off of resolution and sensitivity. ©2012, The Society of Polymer Science, Japan.

DOI： 10.1295/koron.69.639

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We have investigated the removal of base polymers of resist using hydrogen radicals with excellent reduction ability by hot-wire method. Hydrogen radicals were generated by decomposition of H₂ gas on tungsten catalyzer heated at 2400&deg;C. Removal rates of polymers with benzene rings or with cross-linking main chains were slow. It was considered that such cross-linking type polymers have resistance to decomposition to low-molecular compounds because the main chain decomposition and cross-linking reaction proceed simultaneously during hydrogen radical irradiation. Additionally, in the polymers with benzene rings, the reactivity between hydrogen radical and polymer is reduced by resonance stabilization of the benzene ring. Therefore, we clarified that removal rates of the main chain scission type polymers without benzene rings are fast. Furthermore, removal rate was independent of the molecular weight of each polymer. It was considered that the concentrations of monomer units on the surface of polymer film which are the attack sites of hydrogen radicals were constant even with different molecular weights.

DOI： 10.1295/koron.69.266

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In this paper, we describe the use of ozone microbubbles in photoresist removal from silicon wafers. Ozonized water has attracted much attention as an environmental friendly cleaning method in semiconductor manufacturing. However, it would be desirable to enhance the oxidative ability of ozonized water for practical application. The existence of microbubbles in ozonized water has been shown to significantly enhance the photoresist removal rate due to an elevated dissolved ozone concentration (approximately 2.5 times that of ordinary ozone bubbling) and a direct effect of the microbubbles (removal rate is approximately 1.3 times faster than water with the same concentration of dissolved ozone without microbubbles). Additionally, the ozone microbubble solution was able to effectively remove a high-dose ion-implanted photoresist, which is extremely resistant to removal by ozonized water and other wet chemicals because of its amorphous carbon-like layer, or "crust". Electron spin resonance experiments were also performed without the influence of serious metal contamination and indicated the presence of hydroxyl radicals, which are thought to be formed by interaction of ozone with hydroxide ions adsorbed at the gas-water interface upon collapse of the microbubbles. The hydroxyl radicals play an important role in photoresist removal by the ozone microbubble treatment. © 2012 American Chemical Society.

DOI： 10.1021/jp301746g

We have investigated the removal of base polymers of resist using hydrogen radicals with excellent reduction ability by hot-wire method. Hydrogen radicals were generated by decomposition of H2gas on tungsten catalyzer heated at 24000C. Removal rates of polymers with benzene rings or with cross-linking main chains were slow. It was considered that such cross-linking type polymers have resistance to decomposition to lowmolecular compounds because the main chain decomposition and cross-linking reaction proceed simultaneously during hydrogen radical irradiation. Additionally, in the polymers with benzene rings, the reactivity between hydrogen radical and polymer is reduced by resonance stabilization of the benzene ring. Therefore, we clarified that removal rates of the main chain scission type polymers without benzene rings are fast. Furthermore, removal rate was independent of the molecular weight of each polymer. It was considered that the concentrations of monomer units on the surface of polymer film which are the attack sites of hydrogen radicals were constant even with different molecular weights. ©2012, The Society of Polymer Science, Japan.

DOI： 10.1295/koron.69.266

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This paper discusses the fabrication method of Poly(vinylidene fluoride) (I) crystal having excellent dielectric properties. We tried to control the crystal structure of PVDF in the blend films of PVDF and Poly(methyl methacrylate) (PMMA) prepared by solvent casting. PVDF/PMMA = 60/40 wt.% blend was dissolved in DMF solvent at 120&deg;C. After casting, the PVDF/PMMA blend films were baked at 150&deg;C (B). Each film was quenched (Q) from melting state and then was annealed at 120&deg;C (QA). As a result, we demonstrated that PVDF (I) crystal grows preferentially under the existence of PMMA. That the crystallization speed of the quenched and annealed PVDF/PMMA blend films (QA) with the blend ratio of PVDF/PMMA = 60/40 wt.% is comparatively slow and forms the PVDF (I) crystal.

DOI： 10.1295/koron.69.135

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We discuss the effect of prebake temperature on the development characteristics of the positive-tone novolak resin/diazonaphthoquinone (i.e., Photoactivecompound = PAC) resists. Relationships between initial film thickness and sensitivity (E th) of resists with various prebake temperatures were investigated, and multiplex interference and bulk effect were estimated from results of Swing curves of resists. When the prebake temperature is from 80 to 130°C, the sensitivity of resists became lower with rising prebake temperature. Peculiarly, it was observed that the sensitivity of resists degrades remarkably when the prebake temperature is higher than 120°C. On the other hand, the multiplex interference and the bulk effect were independent of prebake temperature. Results of photosensitive parameters (A, B, C) for resists with difference prebake temperatures show that PAC absorption of exposure light (A), resist absorption after exposure (B), and photodegradative rate of PAC (C) were all constant even with differences of prebake temperature. FT-IR and DSC measurements showed no changes in chemical structures of novorlak resin and PAC. The amount of residual solvent in resist film decreased with rising prebake temperature. Peculiarly, the amount of residual solvent at prebake temperatures over 120°C was less than that at prebake temperatures under 120°C. Therefore, we concluded that the sensitivity of the resists becomes lower with rising prebake temperature because the hardness of the resist film increases due to decreases of residual solvent amount because of the rise of prebake temperature. © 2012, The Society of Polymer Science, Japan.

DOI： 10.1295/koron.69.77

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We have investigated the removal of novolac resists into which B and P ions had been implanted with a dose of 5 × 10 14 atoms/cm 2 at acceleration energies of 10, 70, and 150 keV (ion-implanted resists), using wet ozone. Also, we confirmed the presence of the surface hardened layer of ion-implanted resists by cross-sectional observation using scanning electron microscopy (SEM), the stripping of the hardened layer using chemicals, and the measurement of the plastic-deformation hardness of the resists by nanoindentation. The removal rate for a resist using wet ozone decreased with increasing acceleration energy because the hardness of the resist increased with increasing acceleration energy. Moreover, we clarified by time-of-flight secondary ion mass spectrometry (TOF-SIMS), that the ion intensity of C 10H - (m=z 121.01) for the hydrocarbon component, which has the unsaturated bonds as a component of the surface hardened layer increased with increasing acceleration energy. Cresol novolac resin was destroyed and carbonized by ion implantation. Therefore, the removal of ion-implanted resists became difficult with increasing acceleration energy. © 2012 The Japan Society of Applied Physics.

DOI： 10.1143/JJAP.51.026504

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This paper discusses the relationship between ozone concentration and photoresist removal rate, and the removal of ion-implanted photoresists using high concentration wet ozone. The photoresist removal rates increased linearly with increasing ozone concentration. We achieved 3.84 μm/min in ozone concentration of 30vol%. This value is four times as fast as the photoresist removal rate which is expected in a semiconductor manufacturing process. In ozone concentrations of 10vol% and 30vol%, the photoresist into which B ions were implanted with a dose of 5×10 14 atoms/cm 2 at acceleration energy of 70keV was removed. In ozone concentration of 30vol%, the ion-implanted photoresist removal rate was twice as fast as that of ozone concentration of 10vol%. © 2012CPST.

DOI： 10.2494/photopolymer.25.445

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We report on the surface modification of poly(tetrafluoroethylene) (PTFE) as an example of soft materials and biomaterials that occur under plasma discharge by kinetics analysis of radical formation using in situ real-time electron spin resonance (ESR) measurements. During irradiation with hydrogen plasma, simultaneous measurements of the gas-phase ESR signals of atomic hydrogen and the carbon dangling bond (C-DB) on PTFE were performed. Dynamic changes of the C-DB density were observed in real time, where the rate of density change was accelerated during initial irradiation and then became constant over time. It is noteworthy that C-DBs were formed synergistically by irradiation with both vacuum ultraviolet (VUV) and atomic hydrogen. The in situ real-time ESR technique is useful to elucidate synergistic roles during plasma surface modification. © 2011 American Chemical Society.

DOI： 10.1021/jz2002937

We report on the surface modification of poly(tetrafluoroethylene) (PTFE) as an example of soft materials and biomaterials that occur under plasma discharge by kinetics analysis of radical formation using in situ real-time electron spin resonance (ESR) measurements. During irradiation with hydrogen plasma, simultaneous measurements of the gas-phase ESR signals of atomic hydrogen and the carbon dangling bond (C-DB) on PTFE were performed. Dynamic changes of the C-DB density were observed in real time, where the rate of density change was accelerated during initial irradiation and then became constant over time. It is noteworthy that C-DBs were formed synergistically by irradiation with both vacuum ultraviolet (VUV) and atomic hydrogen. The in situ real-time ESR technique is useful to elucidate synergistic roles during plasma surface modification.

DOI： 10.1021/jz2002937

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We removed B-, P-, and As-ion-implanted positive-tone novolak resists with an implantation dose of 5 × 1012 to 5 × 1015 atoms/cm2 at 70 keV, using atomic hydrogen. Though the removal rate decreased with increase in the implantation dose, all of the ion-implanted resists were removed. The rates of thickness of the surface-hardened layer/all resist layer of B, P, and As implanted resists were 0.38, 0.26, and 0.16, respectively, by SEM observation. The removal rate decreased with increasing the rate of the surface-hardened layer. The energy supplied from the ions to the resist concentrated on the surface side in the increasing order of B-P-As. © 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.tsf.2011.01.287

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As part of the effort to elucidate the potential of steam-water mixed spray, a high-speed multi-phase thermal fluid, we conducted a series of experiments with resist-coated silicon wafers as the target of the spray. We measured the amount of the resist removed by the spray, and found that it depends on several parameters such as the thickness and mechanical strength of the resist. The results suggest that the resist removal by the spray is essentially a physical process, and the impact of the spray can be controlled, implying the application potentiality of the spray.

DOI： 10.1299/jsmeted.2011.213

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In the manufacturing process of semiconductor device, MEMS, and so on, lithography which uses photo-resist is a key process to fabricate micro or nano-scale structures, and unnecessary resist should be removed after the process. Typically SPM is used for the resist removal. In this study, we apply the method of steam-water mixed spray that can remove resist without chemicals. In order to clarify the detail mechanism of resist removal, we performed resist removal experiment. In the experiment, spray is traversed over a resist-coated wafer and the removal area is evaluated. The resist-coated conditions such as bake temperature, rotating speed are changed to evaluate the effects of mechanical properties of resist. In addition, removal force is measured to estimate the mechanical properties of resist by using SAICAS. As a result, it is shown that thicker or harder resist tends to be difficult to remove and the results suggest that this method mainly utilizes the physical force of high-speed droplets impact.

DOI： 10.1299/jsmemecj.2011._S054102-1

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We investigated the removal of positive-tone novolak resist, ArF resist, and positive-tone novolak resists into which B, P, and As ions were implanted with a dose of 5x1014atoms/cm2 at an acceleration energy of 70keV (forming ion-implanted resists) using Xe2 excimer UV light. There was an optimum UV irradiation distance with respect to the removal rate since oxygen could not penetrate into the UV irradiation space when the UV irradiation distance was Omm, and the intensity of the UV light decayed when the UV irradiation distance was too great. It was confirmed that the resist was not removed in a nitrogen environment because ozone and oxygen radicals were not generated. There is an optimum substrate temperature for the removal rate the same as for the UV irradiation distance. It was considered that the reactivity between resist and the ozone and oxygen radical was enhanced but ozone concentration decreased by decomposition of the ozone to oxygen molecules with a rise in substrate temperature. Under the optimum UV irradiation conditions, the UV irradiation time for complete removal of ArF resist (0.15μm thick) was 4min. Although the ion-implanted resists were difficult to remove by conventional methods, B- and P-ion-implanted resists were removed by Xe2 excimer UV light. © 2011 CPST.

DOI： 10.2494/photopolymer.24.389

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We investigated the removal characteristics of an ultraviolet (UV) curable polymer for UV nano-imprint lithography (NIL) using atomic hydrogen, which was generated by the catalytic decomposition of H(2) molecules in H(2)/N(2) mixed gas (H(2):N(2)=10:90vol.%) using a tungsten hot-wire catalyzer. The cured polymers were removed by atomic hydrogen without a residual layer. The removal rate of the polymer increased with rising catalyzer temperature. It was assumed that both enhanced reactivity between atomic hydrogen and polymer by the substrate temperature increase due to radiation heat of the catalyzer and increased atomic hydrogen concentration occurred as a result of the rise in catalyzer temperature. When the distance between the catalyzer and the substrate was 100mm, the catalyzer temperature was 2400 degrees C, and the initial substrate temperature was room temperature, the removal rate of polymers was 0.17 mu m/min independent of exposure dose to the polymer. The removal rate of polymers was comparable to the removal rate of general i-line positive-tone novolak resist. The polymer adhering to the micro-asperity portion of the mold was removed without leaving a residual layer by grazing-incidence atomic hydrogen.

DOI： 10.2494/photopolymer.24.383

We investigated the removal characteristics of an ultraviolet (UV) curable polymer for UV nano-imprint lithography (NIL) using atomic hydrogen, which was generated by the catalytic decomposition of H2 molecules in H2/N2 mixed gas (H2:N2=10:90vol.%) using a tungsten hot-wire catalyzer. The cured polymers were removed by atomic hydrogen without a residual layer. The removal rate of the polymer increased with rising catalyzer temperature. It was assumed that both enhanced reactivity between atomic hydrogen and polymer by the substrate temperature increase due to radiation heat of the catalyzer and increased atomic hydrogen concentration occurred as a result of the rise in catalyzer temperature. When the distance between the catalyzer and the substrate was 100mm, the catalyzer temperature was 2400°C, and the initial substrate temperature was room temperature, the removal rate of polymers was 0.17μ.m/min independent of exposure dose to the polymer. The removal rate of polymers was comparable to the removal rate of general /-line positive-tone novolak resist. The polymer adhering to the micro-asperity portion of the mold was removed without leaving a residual layer by grazing-incidence atomic hydrogen. © 2011 CPST.

DOI： 10.2494/photopolymer.24.383

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A halftone mask was used in a lithography process to reduce the number of steps required in semiconductor device manufacturing. Resist patterns with different film thicknesses were produced at same time using the halftone mask. When the halftone mask is used, the resist is exposed in the area where the sensitivity curve rises. Therefore, it is difficult to make the resist films with thicknesses of several tens of percent. Previously, we fabricated the three layer structure by inserting an intermediate layer composed of a water-soluble polymer between the two resist layers with different sensitivity. We realized that the film thickness of several tens of percent was obtained stably with only the lower layer resist remaining. However, three layer structure is not expected to much reduce the number of steps in lithography process because the coating repeated for three times is needed for fabrication of three layer structure. In this study, we demonstrated a twolayer coating without mixing using two kinds of i-line resist (hydrophilic negative-tone water-soluble resist and hydrophobic negative-tone chemical amplification resist) with different solubility values. Both were dissolvable into an alkaline developer. We thus accomplished a novel two-layer resist technology for the halftone mask. © 2010, The Society of Polymer Science,.

DOI： 10.1295/koron.67.506

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We investigated the effects of cooling rate after polymer melting on the room temperature resistivity (PL) and on the positive temperature coefficient (PTC) effect of resistivity of high-density polyethylene (HDPE)/Ni conductive polymer composites. The L of slowly cooled samples was lower than that of quenched samples. It was hypothesized that slow cooling increases the crystallinity of HDPE, forming conductive paths as Ni particles localize in the amorphous matrix of HDPE. In the PTC effect, the inflection-point temperature of the PTC curve rose to the melting point of the HDPE with increasing Ni content. We speculated that the PTC effect of HDPE/Ni composites might occur by two mechanisms: cubical expansion of HDPE, and the diffusion of localized Ni particles into the amorphous matrix of HDPE as a result of the change from a crystalline matrix to an amorphous matrix on melting of HDPE. © 2010 The Society of Polymer Science, Japan (SPSJ) All rights reserved.

DOI： 10.1038/pj.2010.39

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This paper clarifies the reaction order of photoresist removal using atomic hydrogen by investigating the relationship between atomic hydrogen density (nH) and photoresist removal rate (vrmv). Atomic hydrogen was generated by decomposing hydrogen molecules with a tungsten hot-wire catalyst. In the reaction between atomic hydrogen and photoresist, we found that vrmv increases in direct proportion to nH and revealed that the reaction exhibited a first-order kinetics with respect to n H. © 2010 The Japan Society of Applied Physics.

DOI： 10.1143/APEX.3.026501

In this paper, we investigated the removal characteristic of positive-tone novolak photoresists into which B, and As ions were implanted with doses of 5× 1012 -5× 1015 atoms/ cm2 at an acceleration energy of 70 keV using atomic hydrogen, and the hardening mechanisms for the photoresists. All of the ion-implanted photoresists with doses up to 5× 1015 atoms/ cm2 were removed without regard for ion species. The removal rates of the photoresists decreased with increasing ion-implantation dose due to hardening of the photoresist surfaces with implantation. The thickness of the surface-hardened layer of the photoresists decreased in the order of B→P→As, and the removal rate increased with decreasing thickness. The energy supplied from the ions to the photoresist concentrated on the surface side in the order of B→P→As, and the impact of the heavier ion on the photoresist was greater than that of the lighter ion. We deduced that the photoresists exhibited carbonization and cross-linkage attributable to the decrease in OH, CH, and O 1s and the increase in CC, C 1s, and π -conjugated systems. © 2010 The Electrochemical Society.

DOI： 10.1149/1.3288697

Instead of photoresist removal methods using chemicals, we investigated an environmentally friendly removal method using atomic hydrogen generated by decomposing hydrogen molecules by contact with a hot-wire tungsten catalyst. We set the distance between the catalyst and the photoresist substrate (D CS) at 20, 60, 100 and 120 mm and evaluated the apparent activation energy (EAP) for the reaction between photoresist and atomic hydrogen at each DCS. The EAP was determined from Arrhenius plots of the photoresist removal rate against the average substrate temperature. When D CS was 20 and 60 mm, EAP decreased with increasing catalyst temperature (WT = 2040-2420°C) and was not constant. However, when DCS was 100 and 120 mm, EAP was nearly constant at 19 ± 1 kJ/mol without depending on WT. We might obtain the activation energy of about 19kJ/mol in the reaction of photoresist with atomic hydrogen. © The Japan Society of Applied Physics.

DOI： 10.1143/JJAP.49.016701

We evaluated the chemical reactivity of wet ozone and polymers by estimating removal of polymers with various chemical structures using wet ozone. The removal rates of polymers that have the carbon-carbon double bond (C-C double bond) in the main chain (novolak resin, cis-l,4-polyisoprene) were the fastest. The removal rates of polymers that have a C-C double bond in the side chain (PVP, PS) were slower than those of novolak resin and cis-l,4-polyisoprene. Polymers with no C-C double bond (PMMA, PVC) were not removed. We believe that wet ozone should react easily with C-C double bonds. The main chain of novolak resin and that of cis-l,4-polyisoprene should be decomposed by reaction with wet ozone. In PVP and PS, the benzene ring in the side chain changes into carboxylic acid by reaction with wet ozone. Therefore, the dissolution ability of PVP and PS to water should increase. © 2010 CPST.

DOI： 10.2494/photopolymer.23.417

The crystallization of poly(vinylidene fluoride) (PVDF) was observed after the poly(methyl methac-rylate) (PMMA) component was extracted from the PVDF/PMMA (50/50) composite nanofiber fabricated by electrospray deposition, even though the original composite showed a completely amorphous pattern in the wide-angle X-ray diffraction. The content of the β-crystal form in the crystalline region depended on the PVDF/PMMA composite ratios and the type of solvents used for the extraction of the PMMA component, e.g., chloroform and toluene. Thus, the content of the β-crystal form can be controlled by selecting the original PVDF/PMMA composition and the solvent used to extract the PMMA component. © 2009 Wiley Periodicals, Inc.

DOI： 10.1002/app.29644

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We investigated an environmentally friendly method using atomic hydrogen generated by contact catalysis on a tungsten hot-wire catalyzer to remove photoresist instead of using chemicals and its effects on a Si-wafer surface. We eventually obtained a photoresist removal rate of 2.5 mu m/min attributable to a hydrogen irradiation because the photoresist shrank only under the influence of substrate heating by the catalyzer. The effects of atomic hydrogen irradiation on the substrate surfaces cannot be confirmed. (C) 2009 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.48.026503

We investigated an environmentally friendly resist removal method using ozone and water (wet ozone). The resist removal rate was optimum when the temperature of the wet ozone was 83 °C and that of the substrate was 78 °C, Novolak resin of a positive type of novolak resist base polymer has a carbon-carbon double bond in the main chain, so Novolak resin reacted easily with ozone. The resulting removal rate of the novolak resist was about 1.1 μ/min, which was the highest removal rate among novolak, KrF and ArF resists. For all implanted ion species (B, P, and As), all the resist with ions of 5 × 1013 atoms/cm2 could be removed. Resist with 5 × 1014 atoms/cm2 As and P ions could not be removed at al, but resist with B ion could be removed. The energy to harden the resist of B ion was less than that to harden P and As ions, because B ion is lighter than the other ions. All the resist with ions of 5 × 1015 atoms/cm2 could not be removed. © 2009 The Japan Society of Applied Physics.

DOI： 10.1143/JJAP.48.026505

We investigated an environmentally friendly method using atomic hydrogen generated by contact catalysis on a tungsten hot-wire catalyzer to remove photoresist instead of using chemicals and its effects on a Si-wafer surface. We eventually obtained a photoresist removal rate of 2.5 mu m/min attributable to a hydrogen irradiation because the photoresist shrank only under the influence of substrate heating by the catalyzer. The effects of atomic hydrogen irradiation on the substrate surfaces cannot be confirmed. (C) 2009 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.48.026503

We investigated an environmentally friendly method using atomic hydrogen generated by contact catalysis on a tungsten hot-wire catalyzer to remove photoresist instead of using chemicals and its effects on a Si-wafer surface. We eventually obtained a photoresist removal rate of 2.5 μm/min attributable to a reaction of atomic hydrogen with a positive-tone novolak photoresist, without thermal shrinkage of the photoresist film during atomic hydrogen irradiation because the photoresist shrank only under the influence of substrate heating by the catalyzer. The effects of atomic hydrogen irradiation on the substrate surfaces cannot be confirmed. © 2009 The Japan Society of Applied Physics.

DOI： 10.1143/JJAP.48.026503

Novel plasmaless photoresist removal method in gas phase at room temperature has been developed using pure ozone gas which has nearly 100% of concentration. This method has enabled the removal of high dose ion implanted photoresist that had been difficult to remove so far. Conventionally, the temperature rise of 200°C or more was necessary in the photoresist removal with the ozone gas to achieve an enough effect. Because the strong reactiveness is due to the oxygen radical generated when the ozone molecules decomposed. However, Popping by the temperature rise becomes a problem in the removal of high dose ion implanted photoresist. Then, in this experiment, ethylene gas was used to control the decomposition of ozone molecule at the room temperature. As a result, it was confirmed that the ashing using ethylene gas and ozone gas was effective to remove the high dose ion implanted photoresist under unheating condition. © The Electrochemical Society.

DOI： 10.1149/1.3120722

Using environmentally friendly wet ozone instead of chemicals, we removed B-, P-, and As-ion-implanted positive-tone novolak photoresists with an implantation dose of 5× 1012 -1× 1016 atoms/ cm2 at an acceleration energy of 70 keV. Ion-implanted photoresists with an implantation dose exceeding 5× 1015 atoms/ cm2 could not be removed, but photoresists implanted at doses below 5× 1013 atoms/ cm2 could be removed. Photoresist implanted with B ions at 5× 1014 atoms/ cm2 was removed slowly, but photoresists implanted with P and As ions were not removed at all. The hardness of the photoresist with B ions implanted at 5× 1014 atoms/ cm2 was 1.8 times greater than that of the nonimplanted photoresist (AZ6112), that of the P-ion-implanted photoresist was eight times greater, and that of the As-ion-implanted photoresist was five times greater. The B-ion-implanted photoresist was softer than the P- and As-ion-implanted photoresists. We also obtained the calculation results in which the energy supplied from the B ions to the photoresist was lower than that from P and As ions. We assumed that the ion-implanted photoresists were hardened by cross-linkage due to the energies supplied to the photoresists from the ions. Therefore, we determined that the hardness threshold of the photoresist that could be removed by using wet ozone was twice the hardness of AZ6112. © 2009 The Electrochemical Society.

DOI： 10.1149/1.3121583

We investlgated the removal of ion-implanted resists with various acceleration energy using wet ozone. The resist removal rate decreased with increaslng acceleration energy ln B- and P-ion-implanted resists. The hardness of ion-implanted resists increased with increaslng aCCeleration energy as a result of nanoindentation, and was simulated by Stopping and Range f Ions in Matter software (SRIM2008). © 2009 CPST.

DOI： 10.2494/photopolymer.22.321

Using atomic hydrogen for its excellent reduction ability, we demonstrated the removal rates and the hardness of ion-implanted resists. Removal rates of B-ion implanted resists uslng atOmic hydrogen decreased with increaslng implantation dose. According to the hardness of the resists, the indentation depth at l00mgf shifted toward the surface of the resists with increaslng implantation doses. In contrast, removal rates of thermally hardened resists decreased with increaslng baking temperatures. The indentation depth at l00mgf shifted toward the surface of the resists with increaslng baking temperature. Ion-implanted resist removal rate uslng atOmic hydrogen decreased compared with non-ion-implanted resist. We believe that this is because the resists were thermally hardened, attributable to the supplied energy from implanted B-ions. © 2009 CPST.

DOI： 10.2494/photopolymer.22.325

Using atomic hydrogen for its excellent reduction ability, we demonstrated the removal rates and the hardness of ion-implanted resists. Removal rates of B-ion implanted resists using atomic hydrogen decreased with increasing implantation dose. According to the hardness of the resists, the indentation depth at 100mgf shifted toward the surface of the resists with increasing implantation doses. In contrast, removal rates of thermally hardened resists decreased with increasing baking temperatures. The indentation depth at 100mgf shifted toward the surface of the resists with increasing baking temperature. Ion-implanted resist removal rate using atomic hydrogen decreased compared with non-ion-implanted resist. We believe that this is because the resists were thermally hardened, attributable to the supplied energy from implanted B-ions.

DOI： 10.2494/photopolymer.22.325

Using atomic hydrogen for its excellent reduction ability, we demonstrated the removal rates and the hardness of ion-implanted resists. Removal rates of B-ion implanted resists using atomic hydrogen decreased with increasing implantation dose. According to the hardness of the resists, the indentation depth at 100mgf shifted toward the surface of the resists with increasing implantation doses. In contrast, removal rates of thermally hardened resists decreased with increasing baking temperatures. The indentation depth at 100mgf shifted toward the surface of the resists with increasing baking temperature. Ion-implanted resist removal rate using atomic hydrogen decreased compared with non-ion-implanted resist. We believe that this is because the resists were thermally hardened, attributable to the supplied energy from implanted B-ions.

DOI： 10.2494/photopolymer.22.325

CiNii Article

We demonstrated the relationship between the weight-average molecular weight (M(W)) of novolak resin for the positive-tone novolak resist and the dissolution properties of resists obtained by discrimination curves. We subsequently used PROLITH to evaluate the effects of MW of the resin on the resolution of resists while changing the M(W) from 2940 to 13100 as the fixed number-average molecular weight (M(N)) of the resin (M(N)=605 +/- 35). Dissolution contrast (no: the ratio of the dissolution rate of the resist in the exposed area to the dissolution rate of the resist in the unexposed area) of the resist was improved with an increase in M(W) when M(W) was 6370 or less and was saturated (n(D) is approximately equal to 2.9) when M(W) exceeded 6370. Resist development contrast (delta: gradient of change of the dissolution rate from unexposed area to exposed area) improved with an increase in M(W). Using PROLITH, we demonstrated that the resist pattern profile and the process window improved as M(W) increased. However, resist sensitivity degraded with an increase in M(W). Therefore, from the perspectives of resist sensitivity, process window, and contrast, a resist pattern with a better profile may be made stably using the positive-tone novolak resist with novolak resin of M(W) is approximately equal to M(W) = 6370.

DOI： 10.2494/photopolymer.22.357

We demonstrated the relationship between the weight-average molecular weight (Mw) of novolak resin for the positive-tone novolak resist and the dissolution properties of resists obtained by discrimination curves. We subsequently used PROLITH to evaluate the effects of Mw of the resin on the resolution of resists while changing the Mw from 2940 to 13100 as the fixed number-average molecular weight (MN) of the resin (MN=605±35). Dissolution contrast (nD: the ratio of the dissolution rate of the resist in the exposed area to the dissolution rate of the resist in the unexposed area) of the resist was improved with an increase in Mw when Mw was 6370 or less and was saturated (nD≒2.9) when Mw exceeded 6370. Resist development contrast (δ: gradient of change of the dissolution rate from unexposed area to exposed area) improved with an increase in Mw. Using PROLITH, we demonstrated that the resist pattern profile and the process window improved as Mw increased. However, resist sensitivity degraded with an increase in Mw. Therefore, from the perspectives of resist sensitivity, process window, and contrast, a resist pattern with a better profile may be made stably using the positive-tone novolak resist with novolak resin of Mw≒6370. © 2009 CPST.

DOI： 10.2494/photopolymer.22.357

CiNii Article

J-GLOBAL

J-GLOBAL

CiNii Article

J-GLOBAL

The fine structure of poly(vinylidene fluoride) (PVDF) nanofiber prepared by electrospray deposition (ESD) has been investigated by wide angle X-ray diffraction (WAXD) and infrared spectroscopy (IR). The β-phase crystal was dominant in the crystalline region. The degree of crystallinity of 0.54 for the nanofiber, determined by Ruland's method, was almost identical to that for a melt pressed sheet of PVDF. The disorder parameter k was 4, which is significantly smaller than the value of 6 for the melt pressed sheet of PVDF. Molecular orientation along the fiber axis was observed by the polarized infrared spectra of the uniaxially aligned nanofiber. These results suggest that the PVDF nanofiber possesses a fiber structure which is by no means inferior to that of practical fibers. © 2008 Wiley Periodicals, Inc.

DOI： 10.1002/polb.21391

CiNii Article

We evaluated standing-wave effects in photoresists with and without hexamethyldisilazane (HMDS), which improves adhesion of a photoresist to a Si-wafer substrate, using a resist development analyzer (RDA). The amplitude of a swing curve with HMDS was reduced around 9% compared to that without HMDS. Perhaps, this is considered a reduction of standing-wave effect in the photoresist attributable to an antireflection effect of an HMDS-photoresist mixed layer. The antireflection effect of the layer was evaluated by calculation using PROLITH. We demonstrated that the thickness, a refractive index and an extinction coefficient of the layer were, respectively, 10 nm, 1.60 and 0.5. Using HMDS can expect to improve dimensional stability by 1.17 times on the calculations. ©2008CPST.

DOI： 10.2494/photopolymer.21.299

Resist removal technology by using atomic hydrogen generated by tungsten (W) catalyzer was evaluated. This removal method is the dry process which does not use chemicals, so it was expected that the environmental burden and the cost can decrease. The resist removal rate has increased by raising W current and the substrate temperature. The removal rate of the positive type of novolak resist was over 1 μm/min at the current of 30A (W catalyzer was 2000°C) and at the substrate temperature of 230°C. Polyvinyl phenol (PVP) and poly methylmethacrylate (PMMA) which were used as the shorter wavelength resist were able to be removed as well as the positive type of novolak resist. In these three polymers, PMMA removal rate was about three times as fast as those of others. It is thought that polymer with high removal rate has no benzene ring and is main chain scission type polymer. ©2008CPST.

DOI： 10.2494/photopolymer.21.293

Resist removal technology by using atomic hydrogen generated by tungsten (W) catalyzer was evaluated. This removal method is the dry process which does not use chemicals, so it was expected that the environmental burden and the cost can decrease. The resist removal rate has increased by raising W current and the substrate temperature. The removal rate of the positive type of novolak resist was over 1 mu m/min at the current of 30A (W catalyzer was 2000 degrees C) and at the substrate temperature of 230 degrees C. Polyvinyl phenol (PVP) and poly methylmethacry late (PMMA) which were used as the shorter wavelength resist were able to be removed as well as the positive type of novolak resist. In these three polymers, PMMA removal rate was about three times as fast as those of others. It is thought that polymer with high removal rate has no benzene ring and is main chain scission type polymer.

DOI： 10.2494/photopolymer.21.293

J-GLOBAL

New processing technologies are demanded which produce hyperfine structures for electronic devices and which do not exacerbate environmental problems. We specifically examined photoresist removal technology for this study. Ozone gas of nearly 100% concentration was applied to various photoresists and ion-implanted-photoresists. Results showed that reactivity with ozone gas differs between a novolac resist, which has a benzene ring structure on a main chain, a KrF resist with this structure on a side chain, and an ArF resist which has no such structure. The activation energy of the KrF resist indicates a value close to that of the novolac resist; the value for the ArF resist was larger than these. Irrespective of the ionic species, the ion-implanted- photoresist of amount Ie 16 cm-2 of the dose can be removed with 0.7 μm/min or less in the ashing of 400°C in processing temperature. Additionally, results showed that the removal speed slows in order of B, As, and P. ©2008 CPST.

DOI： 10.2494/photopolymer.21.311

J-GLOBAL

A novel strain controlled, free standing tensile fatigue system was developed by using the combined PZT and micromachining technologies in order to conduct in-situ observation and assessment of high cycle fatigue behavior in LP-CVD poly Silicon thin films within a scanning electron microscope (SEM).

DOI： 10.1299/jsmemm.2007.350

CiNii Article

J-GLOBAL

We have investigated the resist removal by using wet ozone. Removal rate of the resist was optimum when both of the wet ozone and substrate temperature was at around 60°C. In that condition, the resist removal was better as decreasing the ozone irradiation interval time. Furthermore, in the better conditions the removal rate of resist was accomplished up to 3.4 μm/min by means of being 1.30mm of gap length between the substrate and the ozone irradiation nozzle. In spite of the implanted ion species, the resist with ions of 5×1012 atoms/cm2 could be removed. It was found that the resist removal rate by using wet ozone was corresponded to the removing with chemicals. ©2007TAPJ.

DOI： 10.2494/photopolymer.20.315

Nanofiber with porous structures were prepared by electrospray deposition (ESD) from poly(vinylidene fluoride) (PVDF)/poly(vinylpyrrolidone) (PVP) blend and subsequent selective removal of PVP. In the present work, the effect of blending ratio of PVDF/PVP on formation of the pore and crystal structure of residual PVDF fiber was investigated. The residual PVDF nanofiber showed a higher specific surface area (the highest specific surface area was 28.54 m 2/g from PVDF/PVP = 67/33 w/w). The Fourier transform infrared spectroscopy and wide angle X-ray diffraction measurement also showed that selective removal of PVP enhanced the formation of β-phase crystal structure in PVDF nanofiber (ff-phase content > 90%). © 2007 The Society of Polymer Science.

DOI： 10.1295/polymj.PJ2007037

CiNii Article

Poly(vinylidene fluoride) (PVDF) nanofibers were prepared by electrospray deposition (ESD). In the present work, the additive effect of ionic fluorinated surfactants-anionic and cationic surfactants - on the diameter, morphology, and crystalline structure of PVDF nanofiber was investigated. The addition of ionic fluorinated surfactants is useful for the formation of bead-free homogeneous fiber. At a higher concentration of the ionic surfactants, thicker fiber was formed. In addition, the Fourier transform infrared spectroscopy and the wide angle X-ray diffraction measurements showed that the addition of both ionic fluorinated surfactants causes a complete change in conformation from the initial α-phase of to the β-phase of PVDF during ESD. A possible mechanism based on the interaction between the polymer and surfactant molecules during ESD is discussed. © 2007 The Society of Polymer Science.

DOI： 10.1295/polymj.PJ2006233

CiNii Article

CiNii Article

J-GLOBAL

A halftone mask was used in a lithography process to reduce the number of steps required in liquid crystal display (LCD) manufacturing. Three thicknesses of resist films were produced using the halftone mask. Since the resist is exposed in the area where the sensitivity curve rises, a problem arises in that the thickness of the resist film fluctuates drastically when the exposure dose to the resist fluctuates slightly. We tried to stabilize the film thickness using two kinds of resists having different sensitivities. We used a low-sensitivity resist as a lower layer and a high-sensitivity resist as an upper layer. However, it was not possible to produce a stable film thickness because the two resists blended at the interface. Therefore, we added an aqueous polymer solution as an intermediate layer between the resists which were dissolved in a solvent. This solved the blending problem and a stable film thickness was obtained. © 2006 The Japan Society of Applied Physics.

DOI： 10.1143/JJAP.45.7949

CiNii Article

J-GLOBAL

J-GLOBAL

We have developed a resist removal process that uses a laser. Laser irradiation far below the ablation threshold was useful to remove a resist that was strongly adhered to the substrate. We used the second harmonics of Nd:YAG (Y3 Al5 O12) laser pulses (532 nm) to irradiate the polyacrylic-type resist for manufacturing printed circuit boards. At appropriate laser fluence, the resist, which transmits the laser light 80% at 532 nm, was detached from the substrate while retaining its original shape. This technique is not based on laser ablation. Therefore, no damage occurred to the substrate. It was a dry process: it used neither water nor chemicals. Compared to conventional chemical processing, environmental pollution is prevented. Power consumption and running costs can be reduced. © 2006 The Electrochemical Society. All rights reserved.

DOI： 10.1149/1.2197767

We evaluated the resolution and sensitivity of a resist with and without hexamethyldisilazane (HMDS), which improves resist adhesion to substrates, by using profilometry. HMDS was spin-coated onto a Si wafer by using a spin coater. The resist with HMDS was always thicker than that without HMDS for the same exposure dose. The resist pattern profile (resolution) with HMDS was better than that without HMDS. We found that UV absorbance of the resist with HMDS was greater than without HMDS. The resist was mixed with HMDS, and the phenolic hydroxyl groups of the resist were silylated by HMDS. The light through the resist was absorbed in the mixed layer. Also, the mixed layer weakened the reflected light from the Si substrate. We demonstrated that the mixed layer generated by resist with HMDS works as an antireflection coating for the resist. ©2006TAPJ.

DOI： 10.2494/photopolymer.19.75

A diazonaphthoquinone/novolak resist on a 42-alloy substrate was irradiated by the second harmonic wave (532 nm) of a pulsed Nd3+YAG laser. The resist was removed, despite the existence of hexamethyldisilane (HMDS). There was no apparent damage to the substrate. In contrast, the resist on a Si wafer could not perfectly be removed. In some cases, there was damage to the substrate. The peeling strength of the resist with HMDS was about three times than that without HMDS. The width of the resist removed by laser irradiation without HMDS was 1.02-1.03 times larger than that with HMDS. The use of this process will benefit the environment, since expensive and toxic chemicals are not used. © 2005 The Japan Society of Applied Physics.

DOI： 10.1143/JJAP.44.8673

Conductive polymer composites filled with conductive filler particles exhibit a positive temperature coefficient (PTC) effect. It is desirable to develop these composites with a low resistivity at room temperature and a high resistivity after polymer melting. We evaluated the relationships between the PTC properties of the composites and the type of the metal, the particle size of the metal, and the metal content. Among metals containing composites evaluated in this study, the composite consisting of tungsten (W) showed the best PTC properties. Then we compared the PTC properties between the composites consisting of W and of CB. The composite consisting of W has a lower resistivity at room temperature and a higher resistivity after polymer melting than that consisting of CB. Generally, the composite which has a low resistivity at room temperature has a low resistivity after polymer melting. We developed the composite consisting of high-density polyethylene (HDPE)/W = 59/ 41 vol% (7/93 wt%), which showed a 0.01 Ω cm resistivity at room temperature, and a 105 Ω cm resistivity after polymer melting. This composite has no negative temperature coefficient effect after polymer melting. © 2005 The Japan Society of Applied Physics.

DOI： 10.1143/JJAP.44.4171

When the halftone mask is used in the lithography process in LCD manufacturing, the manufacturing process number is reduced. By the use of the halftone mask, the exposure dose to the resist is adjusted, and three kinds of resist film thickness are produced. However, the resist is exposed in the part in which the sensitivity curve rises. When the exposure dose to the resist fluctuated slightly, the resist film thickness dRastically fluctuated. This time, we used two kinds of the resist that have different sensitivities. The lower layer resist has low sensitivity and the upper layer resist has high sensitivity. Though we applied two resists which optimized the bake condition, the horizontal part was not obtained. We thought that the two resists may have mixed. We added a water-soluble intermediate layer film between two resists, and then it became possible to eliminate the variation of the resist film thickness due to the slight variation of the exposure dose.

DOI： 10.1295/koron.62.221

Conducting polymer composites filled with carbon black (CB) exhibit a positive temperature coefficient (PTC) effect. It is desirable to develop these composites with a low resistivity at room temperature and with a high PTC intensity. We evaluated the dependence of the PTC properties of the composites on the type and crystallinity of the component polymers, and the content and particle size of CB. Among the crystalline polymers investigated, we found that high-density polyethylene (HDPE) has the lowest resistivity at room temperature and the highest resistivity after polymer melting. The higher the crystallinity of HDPE, the lower the resistivity of the composites. The resistivity of the composites decreased with increasing CB content. The smaller the CB particle size, the lower the resistivity of the composites. We developed composites with a low resistivity at room temperature and a high resistivity after polymer melting. The resistivities of the composite consisting of 45wt% HDPE and 55wt% CB were 0.17Ωcm at room temperature and 930 Ωcm cm after polymer melting. © 2005 The Japan Society of Applied Physics.

DOI： 10.1143/JJAP.44.2025

CiNii Article

Two-photon absorption of CsLiB6O10 (CLBO) related to the enhanced bulk damage resistance was investigated by using transmittance measurements. Pulsed laser beams at wavelengths of 532 and 266 nm were irradiated to CLBO crystals having several bulk damage resistances while the pulsed laser energy is varied from low enough to be negligible nonlinear absorption up to just below the laser-induced damage threshold. At a wavelength of 532 nm, the nonlinear absorption did not occur even at the laser fluence just below the damage threshold. In contrast, two-photon absorption depending on the bulk damage resistance was clearly observed at a wavelength of 266 nm. A high-quality CLBO having a high-damage resistance shows a 2 times lower two-photon absorption coefficient than that of a conventional CLBO. © 2005 The Japan Society of Applied Physics.

DOI： 10.1143/JJAP.44.L665

This study developed a new method for removing positive-tone diazonaphthoquinone/novolak resist. The fourth harmonic wave (λ=266nm) of a pulse Nd3+:YAG laser was used. Ablation occurred at the resist surface when it was irradiated with over 35mJ/cm2. The amounr of removed resist increased with an increase in the laser energy, and it was possible to remove a 250nm thick resist layer by one pulse irradiation with 94mJ/cm2. Resist with an initial thickness of 1100nm and could be completely removed with no damage to the Si wafer after being irradiated seven times with 94mJ/cm2. The XPS measurement indicated that the residual amount of carbon from the Si surface irradiated by a laser under the vacuum was almost same to that from a Si wafer without resist coating. Resist removal method by laser is environmentally sound and will contribute to energy reduction. © 2005TAPJ.

DOI： 10.2494/photopolymer.18.181

This study revealed a promising method for removing positive-tone diazonaphthoquinone/novolak resist. The fourth harmonic of an Nd 3+:YAG (Y3Al5O12) pulsed laser (266nm) was irradiated onto the resist. Resist was removed when laser power exceeded 35mJ/cm2, and a 250nm-thick resist was removed with a laser power of 94mJ/cm2. X-ray Photoelectron Spectroscopy (XPS) proved that 1100 nm-thick resist could be completely removed from a Si surface when it was irradiated almost 700mJ/cm2. The resist onto three inch Si wafer (45.58mm2) was removed in two minutes by laser. No damage to the processed Si wafer could be detected by optical microscopic observation. This method is good for environment.

DOI： 10.1295/polymj.37.813

The compatibility of Poly (vinylidene fluoride) / Poly (methyl methacrylate) (PVDF/PMMA) blend and the crystal structure of PVDF were examined according to the blend ratio, the cooling speed from the melt state and annealing. Different crystal structures of PVDF (form I) and PVDF (form II) could be produced from PVDF/PMMA blend. Generally, it is said that the crystal structure of PVDF (form I) is very difficult to obtain. When PVDF/PMMA (70/30 wt%) blend was melted, quenching and annealing over 60°C, we revealed that the crystal of PVDF (form I) was dominantly grown. It is considered that the crystallization speed of PVDF depends upon the compatibility of PVDF/PMMA blend. The crystallization speed of PVDF (form I) is slow when the compatibility of the blend is very high, resulting the formation of PVDF (form I).

DOI： 10.1149/1.2137651

CiNii Article

Positive-tone diazonaphthoquinone/novolak resist on a 42-alloy (Fe : Ni=42:58wt%) substrate was irradiated by the second harmonic of Nd:YAG (Y 3Al5O12) laser (532nm). The resist was removed (stripped) completely, despite the presence of hexamethyldisilane (HMDS) and the pre-bake condition of the resist. There was no apparent damage to the substrate by the laser. In contrast, this resist on a Si wafer could not be removed completely, and the substrate was occasionally damaged as well. The fourth harmonic of Nd:YAG laser (266nm) was used to irradiate the resist on the Si wafer, ablation was effective. There was no apparent damage to the substrate. This resist does not absorb the energy of the laser at 532nm because ft is optically transparent (over 90%) above 500nm. However, its transmittance was very low (under 5%) below 300nm. The resist therefore absorbed the energy of the 266nm laser, and was removed (ablated). This development addresses environmental concerns because expensive and toxic chemicals are not used. ©2005TAPJ.

DOI： 10.2494/photopolymer.18.665

The laser-induced damage threshold of polished fused silica surfaces is much lower than the damage threshold of its bulk. It is well known that contaminations of polished surface are one of the causes of low threshold of laserinduced surface damage. Particularly, polishing contamination such as cerium dioxide (CeO2) compound used in optical polishing process is embedded inside the surface layer, and cannot be removed by conventional cleaning. For the enhancement of surface damage resistance, various surface treatments have been applied to the removal of embedded polishing compound. In this paper, we propose a new method using selective chemical removal with high-temperature sulfunc acid (H2SO4). Sulfuric acid could dissolve only CeO2 from the fused silica surface. The surface roughness of fused silica treated H2SO4 was kept through the treatment process. At the wavelength of 355 nm, the surface damage threshold was drastically improved to the nearly same as bulk quality. However, the effect of our treatment was not observed at the wavelength of 1064 nm. The comparison with our previous results obtained from other surface treatments will be discussed.

DOI： 10.1117/12.585219

When the halftone mask is used in the lithography process in LCD manufacturing, the manufacturing process number is reduced. By the use of the halftone mask, the exposure dose to the resist is adjusted, and three kinds of resist film thickness are produced. However, the resist is exposed in the part in which the sensitivity curve rises. When the exposure dose to the resist fluctuated slightly, the resist film thickness drastically fluctuated. This time, we used two kinds of the resist that have different sensitivities. The lower layer resist has low sensitivity and the upper layer resist has high sensitivity. Though we applied two resists which optimized the bake condition, the horizontal part was not obtained. We thought that the two resists may have mixed. We added a water-soluble intermediate layer film between two resists, and then it became possible to eliminate the variation of the resist film thickness due to the slight variation of the exposure dose.

A method of removing the photoresist using ozone gas with acetic acid vapor has been developed. Glass substrates (size 100 × 100 mm2) coated with I-line resist were treated under the conditions of substrate temperature, (Ts) 27-50°C; acetic acid vapor, 2-18 vol %; ozone, 0-9.3 vol % (0-200 g/m3); total gas flow rate, 2 L/min; and gas pressure, 100 kPa. A previous ozone treatment with oversaturated water vapor or sprayed water overcame the limitation of ozone diffusion into the resist by the control of the water film on the resist. In this study, pure acetic acid vapor has been first applied for the resist removal by ozone in order to improve the oxidation rate of the resist, because acetic acid is an inactive solvent in the ozonization, and the solubility of ozone is much higher than water. It was observed that the resist removal rate increased with acetic acid and ozone concentration, and reached at 6 μm/min at Ts = 50°C, which was about six times greater than that of the previous ozone treatment. Metal corrosion of molybdenum and aluminum electrodes was found negligible during the ozone treatment with acetic acid vapor. The mechanism of resist removal without the metal corrosion by ozone with acetic acid vapor is also discussed, based on the solubility of ozone in acetic acid and the corrosion current in ozonized solutions. © 2004 The Electrochemical Society. All rights reserved.

DOI： 10.1149/1.1833311

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