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Poly(?-glutamic acid) (PGA) is a biopolymer produced by Bacillusspp. via the ?-amide linkages of d- and/or l-glutamate. Although high-molecular-weight (HMW) PGA possesses many attractive properties, such as flocculating, wound healing, and immune-stimulating effects, no studies have reported factors useful for increasing the molecular weight of PGA during microbial production. PgsB, PgsC, and PgsA are the minimum protein sets required for PGA production in B. subtilis, and PgsE improves PGA productivity. Analysis by size-exclusion chromatography combined with multiangle laser light scattering revealed that the molecular weight of PGA was Mw?=?2,900,000?g?mol-1and predominantly Mw?=?47,000?g?mol-1in preparations derived from B. subtiliscells with and without pgsE, respectively. PgsE may be required to increase the molecular weight of PGA.

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.Theremoresponsive conductive materials were produced from polyacrylamide-based polymers and Ni microparticles. The materials exhibited PTC (positive temperature coeffcient) phenomenon regarding electric resistivity, yet such PTC phenomena had been observed only in crystalline polymer-based composite materials. Our strategy of using polyacrylamides will contribute to the development of PTC materials by diversifying the material design.

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.

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.Alternating radical copolymerization of cyclic conjugated diene monomers with oxygen were carried out to generate degradable polyperoxides. The cyclopentadiene and furan based-polyperoxides consisted of the different regiospecific structures, and 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.

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 (τfastand 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.

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.

This paper demonstrates a simple method for the preparation of poly(vinylidene fluoride) (PVDF) films using the antisolvent addition method. The antisolvent addition method was performed by immersing PVDF solution-casted substrates into the antisolvent for PVDF at room temperature for a few minutes. After immersing and drying for a few hours, a PVDF film was easily obtained. Then, the crystalline structure of the resulting PVDF film was changed in the order of a, ?and ßphases with increasing dipole moment of the solvent.

It is well known that electron beam lithography is one of the potential candidates to fulfill of the demand of the miniaturization of the design rule of semiconductor integrated circuits beyond sub 100nm size with high reproducibility. It is also a fact that the resolution is recognized to depend on the various factors which are oriented to the machine and process conditions, for example, electron beam diameter, the intensity distribution of the beam itself, the resistance properties polymers, the development conditions, etc. Therefore, it is thought that it is impossible to be derivable directly and unambiguously from the resist material itself. In this study, the intrinsic resolution of the resist polymer was discussed based on the hypothesis that the resolution itself may be able to improve to the same size as the size of an electron beam profile, or less. The bi-layer structure ZEP520A/poly methyl glutar imide (PMGI) was proposed and tested. As for the results achieved, the contrast γ was improved constantly with a reduction in the development time and a decrease in the development temperature. The highest γ value, approximately 18, was obtained during development at the-20°C condition. An approximately 70nm with high aspect ratio pattern which is almost the same size of the beam pattern was obtained. This result provides an understanding how the intrinsic resolution of the resist material should be, and can be applied to other lithography methods. This process was applied to the actual electrode pattern making process. An approximately 100nm width of Copper nanowire as the gate electrode for the AlGaN/GaN HFET was successfully demonstrated. In addition, AlGaN/GaN HFET operated at about 73.5GHz, successfully.

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.The lower critical solution temperature of the thermo- and photo-responsive polymers, which involve the coumarin units having functions for the dual-responsivity in chloroform, were controlled by copolymerization with solvophilic and solvophobic comonomers. The photodimerization of the coumarin units in the copolymer resulted in a decrease in the cloud points.

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.

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.

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.

The decomposition of phenol and 4-chlorophenol by underwater pulsed discharge has been examined. The addition of hydrogen peroxide improved the decomposition rate of phenol by about 2.5 times and that of 4-chlorophenol by about 1.5 times. Analysis using a fluorescent probe suggested that the addition of hydrogen peroxide enhanced the production of hydroxyl radicals by about 3 times. We have also examined the effect of using microbubbles on the decomposition of phenol. The use of only microbubbles resulted in a slight increase of the decomposition rate, while the use of both microbubbles and hydrogen peroxide led to a remarkable enhancement of the decomposition rate by about 3.5 times with the conversion of phenol reaching 70% at discharge time of 3 h, which corresponded to the energy yield of 4.39 × 10–9mol J-1.

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.

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.

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.

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.

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 0.17m/min independent of exposure dose to the SU-8. Finally, we obtained high removal rate for SU-8 (exposure dose = 14mJ/cm2(Dg100)) of approximately 4m/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.

We investigated the effects of cooling rate after polymer melting on the room temperature resistivity (?L) and on the positive temperature coefficient (PTC) effect of resistivity of high-density polyethylene (HDPE)/Ni conductive polymer composites. The ?Lof 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.

In this paper, we investigated the removal characteristic of positive-tone novolak photoresists into which B, P, and As ions were implanted with doses of 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 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 , 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 , 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 , C 1s, and p-conjugated systems.

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 ($D_{\text{CS}}$) at 20, 60, 100 and 120 mm and evaluated the apparent activation energy ($E_{\text{AP}}$) for the reaction between photoresist and atomic hydrogen at each $D_{\text{CS}}$. The $E_{\text{AP}}$ was determined from Arrhenius plots of the photoresist removal rate against the average substrate temperature. When $D_{\text{CS}}$ was 20 and 60 mm, $E_{\text{AP}}$ decreased with increasing catalyst temperature ($\mathit{WT}=2040{\mbox{--}}2420$ \mbox{\circC}) and was not constant. However, when $D_{\text{CS}}$ was 100 and 120 mm, $E_{\text{AP}}$ was nearly constant at $19 \pm 1$ kJ/mol without depending on $\mathit{WT}$. We might obtain the activation energy of about 19 kJ/mol in the reaction of photoresist with atomic hydrogen.

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 at an acceleration energy of 70 keV. Ion-implanted photoresists with an implantation dose exceeding could not be removed, but photoresists implanted at doses below could be removed. Photoresist implanted with B ions at 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 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.

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{degree sign}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.

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.

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 m2/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 ß-phase crystal structure in PVDF nanofiber (ß-phase content > 90%).

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 a-phase of to the ß-phase of PVDF during ESD. A possible mechanism based on the interaction between the polymer and surfactant molecules during ESD is discussed.

This study revealed a promising method for removing positive-tone diazonaphthoquinone/novolak resist. The fourth harmonic of an Nd3+:YAG (Y3Al5O12) pulsed laser (266 nm) was irradiated onto the resist. Resist was removed when laser power exceeded 35 mJ/cm2, and a 250 nm-thick resist was removed with a laser power of 94 mJ/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 700 mJ/cm2. The resist onto three inch Si wafer (45.58 mm2) 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.

A novel chiral ligand mimicking N-Ar axial chirality, (S)-N-[2-(diphenylphosphanyl)naphthalen-1-yl]-2-(piperidinyl­meth­yl)piperidine, was found to exhibit good enantioselectivity (up to 80% ee) in the asymmetric cross-coupling reaction of 1-phenyl­ethylmagnesium chloride with β-bromostyrene derivatives. Additionall­y, this type ligand is appealing, because it allows the synthesis of a wide variety of analogues.

A photo-resist removal process, using highly-concentrated ozone gas and water vapor, has been investigated in the presence of ammonia. Test substrates (size 520 mm × 410 mm) coated with I-line resist and with pretreatment (140°C baking in 3000 sec and SF6/O2dry etching) are chosen from a real manufacturing process for TFT-LCD (Thin film transistor Liquid Crystal Display) panel fabrication. The resist removal rate was measured under the conditions of substrate temperature (Ts) 59-83°C, ammonia 0-6.4vol%, ozone 10.7 vol%, total gas flow rate 12.5 slm, and gas pressure 100 kPa. It was found that the removal rate increased with ammonia concentration and reached at 2.1μm/min at Ts= 74°C. It is suggested that ammonia neutralizes acids to form ammonium salts, improving the dissolving rate of the decomposed resist into water. The corrosion of Al electrode on a substrate was also evaluated, when the resist was completely removed by the moist ozone treatment. Ammonia addition was found to maintain pH value of water on the substrate around neutrality and prevent the Al corrosion.

We have investigated the removal of novolac resists into which B and P ions had been implanted with a dose of $5\times 10^{14}$ atoms/cm2at 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 C10H-($m/z$ 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.

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 degC, 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 degC, 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.

In this paper, we investigated the removal characteristic of positive-tone novolak photoresists into which B, P, and As ions were implanted with doses of 5×1012–5×1015atoms/cm2at 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 5×1015atoms/cm2were 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 C=C, C 1s, and π-conjugated systems.

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 vrmvincreases in direct proportion to nHand revealed that the reaction exhibited a first-order kinetics with respect to nH.

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 5×1012–1×1016atoms/cm2at an acceleration energy of 70 keV. Ion-implanted photoresists with an implantation dose exceeding 5×1015atoms/cm2could not be removed, but photoresists implanted at doses below 5×1013atoms/cm2could be removed. Photoresist implanted with B ions at 5×1014atoms/cm2was 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 5×1014atoms/cm2was 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.

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{degree sign}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.

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 (Y3Al5O12)laser pulses (532nm)to irradiate the polyacrylic-type resist for manufacturing printed circuit boards. At appropriate laser fluence, the resist, which transmits the laser light 80% at 532nm, 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.

For Abstract see ChemInform Abstract in Full Text.

For Abstract see ChemInform Abstract in Full Text.

For Abstract see ChemInform Abstract in Full Text.

The newly synthesized polymers containing organotin indicate higher sensitivities (2500 mJ/cm2) to synchrotron radiation X-ray (SR X-ray). The sensitivities and the imaging types depend on the amount of tin atoms incorporated in the polymers. Their resistance of the O2gas reactive ion etching is 50 times higher in comparison with poly(methyl methacrylate) (PMMA). The results for electron beam (EB) are also reported.

Novel techniques for electron beam (EB) direct writing are established for the development of sub-quarter micron devices. These techniques include 1) use of highly stable processes for positive and negative chemical amplification resists, 2) precise pattern size control by way of proximity effect correction using the pattern-area-density method, 3) a practical improvement technique for pattern size error at the exposure-field boundary, and 4) a novel alignment technique for a substrate covered with a heavy metal film. Successful fabrication of sub-quarter-micron test devices indicates that variable-shaped EB direct writing using these techniques is the best tool for research and development of advanced devices.

For chemically amplified electron beam (EB) resist composed of partially tert-butoxycarbonyl (tBOC) protected poly(p- vinylphenol) (PVP), a dissolution inhibitor, and an acid generator, the effect of the dissolution inhibitors on the dissolution characteristics of resist are investigated. As dissolution inhibitors, hydroquinone protected by a tert-butoxycarbonyl group (B-HQ) and isophthalic acid protected by a tert-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. A 0.14 µ m line and space pattern is fabricated at 17.5 µ C/cm2using 50 keV EB in the resist consisting of B-IP.