A novel photo-adhesive material containing 2-hydroxypyridyl groups was prepared with a radical photo-initiator and a methacryl monomer having a 2-hydroxypyridyl group. The methacryl monomer was obtained as a stable colorless liquid. It seemed that 2-hydroxypyridyl group of the methacryl monomer took mainly the ractim-type structure in solution, resulting from its tautomerization reaction. Photo-adhesion was achieved between a glass substrate and another one (glass or dissimilar materials), after 1 J/cm² of UV irradiation at a wavelength of 365 nm. Shear stress up to 6.2 MPa was recorded, and thermal dismantlement of the sample was also observed. Furthermore, using residue of the adhesive layer on each substrate, re-adhesion was performed with gentle heating.

Laser induced resist stripping technique in water is interesting for both fast and environment-friendly resist removal. However, small pieces of the deposited resist still remain or reattach on the silicon (Si) wafer after laser irradiation. In order to eliminate the remaining resist on the Si wafer surface in environment-friendly way, the effects of ozone water and ozone microbubble water treatments were investigated. The laser induced resist stripping area was effectively expanded by 1.27 times in 600 sec by the immersion treatment in ozone water. Furthermore, combination of ozone microbubbles and flowing water treatment enhanced the resist removal rate by about 20% each. These results demonstrated that the synergy of the laser induced effect, the ozone microbubble and flowing water treatment has a great potential for fast and environment-friendly resist removal technique.

Our research aimed to develop a bioabsorbable material, a mixed compound of polyglycolic acid and polylactic acid, by surface nanopatterning using thermal imprinting technology and utilize it for life science and medical applications. Bioabsorbable materials such as polyglycolic acid and polylactic acid are one of the most difficult materials to surface nanofabricate in terms of melting point and flowability. Therefore, gas generated during processing was allowed to permeate through a porous cyclodextrin-based gas-permeable mold, and surface nanopatterning with a projection height of 1–2 μm and a pitch of 1.24 μm was successfully performed. Surface nanopatterning at a thermal imprint firing temperature of 50°C is expected to enhance the surface modification of bioabsorbable materials, which may be used in a wide range of applications.

We earlier reported that the removal rate of positive-tone novolac photoresist was enhanced compared to that of a pure hydrogen system when a H₂/O₂ gas mixture is activated by a hot tungsten filament. However, when the added oxygen amount was increased to more than 1.0%, the removal rate decreased considerably. We specifically examined cross-linking between novolac resin and photoactive compound (PAC), which are the main photoresist components, as one cause of this decrease in the removal rate. For examination in this study, the “PAC-mediated cross-linking model” was proposed to identify the cross-linking site on novolac resin. To investigate functional group interaction with PAC, we examined the removability of polystyrene-based polymers with various PAC contents. For poly(vinyl phenol), which has an OH group at the terminal end on side chain, a markedly decreased removal rate was confirmed with increased added oxygen when the PAC content was 18.7 wt%. This decrease was never observed in others. For the commercial positive-tone novolac photoresist, the decreased removal rate under excessive oxygen addition might be ascribed to cross-linking, which can be formed by mediating PACs near OH groups on the main chain of novolac resin.

Frictional property is one of the most important physical factors in designing artificial hair. Using a sinusoidal motion friction evaluation system, the frictions of eight commercial artificial hairs and natural human hair were evaluated when they were rubbed with an artificial finger. The friction profiles of all artificial hairs exhibited very general stable patterns: the outward and homeward frictional behaviors were similar and no significant oscillations were observed. The frictional forces of human hair and artificial hair derived from human hair were smaller than that of hair fabricated from synthetic fibers. In addition, the shape of the artificial hairs, particularly whether they were straight or wavy, significantly affected the friction parameters. These findings will be useful for understanding the characteristics of artificial hair to control its tactile texture.

Polyimide-TiO₂ hybrid films, PICOOH-TiO₂s, were prepared by the synthesis of polyamic acid having carboxylic acid group sidechains in the presence of TiO₂. TiO₂ and benzophenonetetracarboxylic dianhydride (BTDA) were added to a solution of 3,5-diaminobenzoic acid and 4,4’-oxydianiline(ODA) in NMP and stirred at room temperature for 24 h, 220 h, and 410 h. The NMP solutions were cast onto a glass plate and dried at 70 ℃, and thermal cyclodehydration of the polyamic acid was performed by successive heating at 100 ℃ for 1 h, 200℃ for 1 h, and 300 ℃ for 1 h. T_g values of polyimides in the polyimide-TiO₂ hybrid films, PICOOH-TiO₂-24, prepared by stirring for 24 h after the addition of TiO₂ and BTDA, PICOOH-TiO₂-220 prepared by stirring for 220 h, and PICOOH-TiO₂-410 prepared by stirring for 410 h, were 284 ℃, 361 ℃, and 377 ℃, respectively. The T_g values became higher with increased stirring time after the addition of TiO₂ and BTDA, exhibiting stirring time dependence.

In this study, poly(methyl methacrylate) (PMMA) microcapsules containing photochromic spiro-pyran dyes were prepared by the solvent volatilization method. The effects of different core-to-shell ratios, emulsifier dosage and temperature on the yield, size and morphology of PMMA microcapsules were investigated. The results showed that the highest yield was achieved when the core-to-shell ratio was 2:1, the amount of emulsifier was about 2% of the aqueous phase, and the volatilization temperature should be controlled at about 35 ℃. Scanning electron microscopy (SEM) images and particle size analysis showed that spherical microcapsules were formed with an average particle size of about 2 μm. The photochromic microcapsules have excellent thermal stability and can withstand a temperature of 300 ℃; the color change response performance is excellent and the color can reach saturation within 14 s. The prepared photochromic microcapsules were screen printed on cotton fabric, and scanning electron microscope (SEM) images showed that there was an attachment between the photochromic microcapsules and the fibers. The K/S values of the printed cotton fabrics were almost unchanged by UV light cyclic irradiation for 30 consecutive times, indicating that the printed cotton fabrics have excellent color change and fatigue resistance. The photochromic fabric responds quickly to color change under UV light irradiation and reaches saturation color depth after 30 s.

We have developed a three-component novolac resist incorporating a chemical amplification mechanism. The three components are a novolac resin, a dissolution inhibitor, and a photoacid generator. In this study, we investigated the change in dissolution rate and resist characteristic by reducing the number of protecting groups on the dissolution inhibitor. The dissolution inhibitor is a compound obtained by protecting some of the three hydroxyl groups of the dissolution accelerator (DA), which is a phenol derivative, with tBoc groups. From the dissolution rate of the polymer film, tBoc-DI-1(33%) in which one of the three hydroxyl groups was protected with tBoc group and DA showed dissolution promoting ability. tBoc-DI-2(67%) in which two of the three hydroxyl groups were protected with tBoc groups and tBoc-DI(100%) in which the three hydroxyl groups were completely protected exhibited dissolution inhibition ability. Mixtures of fully protected tBoc-DI(100%) and DA and tBoc-DI(X%) with randomly protected hydroxyl groups on DA have the same sensitivity, but the resolution of tBoc-DI(X%) was better. This is probably because tBoc-DI(100%) has a very large ability to suppress dissolution.

Microbubbles (MBs) are tiny bubbles with a particle size of 1 - 100 μm. It has been reported that MBs have excellent gas dissolving ability, and hydroxyl radicals are generated when microbubbles collapse in water. Therefore, we aimed to decompose persistent organic compounds using hydroxyl radicals generated by MBs collapse. In this study, we evaluated the degradation of the aromatic compounds methylene blue and salicylic acid by oxygen MBs water. Methylene blue was used as a hydroxyl radical detector, and we investigated the conditions under which hydroxyl radicals were generated most frequently. We confirmed that hydroxyl radicals were generated most frequently when oxygen MBs water generated by the gas-liquid revolving system was circulated under acidic conditions. The presence of cations such as copper and hydrogen ions affects the stability of MBs, and the shear stress caused by the swirling liquid flow is thought to promote MB crushing. Treatment of salicylic acid under these conditions reduced the Total Organic Carbon (TOC) of salicylic acid by about 40%. In addition, From the intermediate products, we confirmed that salicylic acid and hydroxyl radicals undergo substitution reactions according to the orientation of the functional group.

Photo-decomposable bases (PDBs) are basic materials that turn into neutral ones photochemically. TWE calculate the slope of the latent acid gradient after base neutralization and before diffusion and show that this gradient is generally larger when PDB is used instead of traditional non-photosensitive quencher. The gradient generally improves as more PDB is added. Two different limiting cases are calculated; one where the PDB and PAG do not compete for photons or secondary electrons but instead photolyze independently and one where the do compete. The first case may be encountered in chemically amplified resists where the overall optical absorbance is low and photons react directly with the PAG and PDB. The second case is likely to encountered in EUV lithography where replacing conventional base with PDB does not change the EUV absorbance of the resist. The calculations show that the PDB will probably give a large improvement in latent acid gradient in the second case.

A two-layer polymeric stack is designed to be converted to a three-layer stack using sequential bakes. The three-layer stack is composed of layers that are (bottom to top): insoluble, soluble, and insoluble in 0.26 N TMAH developer. The two-layer stack is composed of a bottom layer that is a 193-nm positive tone resist containing a thermal acid generator (TAG) and, optionally, a crosslinker. The top layer contains a t-butyl acrylate monomer that can be deprotected by catalytic acid. During the sequential bakes, the TAG is designed to decompose to generate an acid that diffuses into the top layer. Diffusion lengths of 20-30 nm have been demonstrated. Additionally, the Arrhenius activation parameters are described for the acid-catalyzed deprotection of two esters in combination with strong and weak sulfonic acids. Surprisingly, the rates of these reactions are dictated more by their entropy than by their enthalpy.

A two-layer polymeric stack is designed to be converted to a three-layer stack via the diffusion of small molecules between layers. The three-layer stack is composed of a bottom layer carboxylic acid (CA-polymer) that is soluble in aqueous TMAH developer; a middle layer of reacted CA-polymer that became soluble in organic developer as a result of reaction with small molecules; and a top layer of nonpolar polymer that is soluble in organic developer. Several small molecules were evaluated for their effectiveness, by combing them with the CA-polymer and evaluated in their effectiveness in decreasing the solubility of this polymer in aqueous base. High molecular weight amines, benzyl bromide combined with nonnucleophilic base, dicyclohexylcarbodiimide, and diisopropylcarbodiimide all are capable of switching the solubility of the CA-polymer. These molecules were used in two-layer stacks to study diffusion, reaction and solubility change. The Tg of the CA-polymer was lowered to promote diffusion of the small molecule from the top to the bottom layers.

Irresistible Materials (IM) is developing a photoresist based on the multi-trigger concept, which is designed to suppress roughness using a new photoresist mechanism incorporating a dose dependent quenching-like behaviour, and which is based on high EUV absorbance molecular, rather than polymeric, materials to maximise resolution. The latest results using the NXE Scanner are discussed here. The second generation (MTR Gen 2) of MTR incorporates more optimised crosslinker and photoacid generator molecules to tune the reaction rates in the multi-trigger mechanism. We have shown that the dose requirement compared to the first generation (MTR Gen1) of high opacity MTR resists previously presented can be significantly reduced without detriment to LWR or resolution. Lines and Spaces at p28 nm can be patterned at doses from 20 mJ/cm² to 50 mJ/cm² dependent on formulation ratio, with optimum LWR (3.95 nm, biased) occurring at 32 mJ/cm², CD 12.1nm, in a MTR Gen2.4 formulation. Similarly, we present p34 & p36 pillars patterned between 20 mJ/cm² and 60 mJ/cm² doses for 17 nm diameter pillars, with a minimum LCDU for 18 nm diameter p36 pillars of 3.6 nm at 45 mJ/cm² (MTR Gen2.4).

Lead halide perovskites (LHPs) have a diverse compositional range owing to various employable A- and X-site ions. However, the effect of underlying charge transport layer (CTLs) on the charge transport properties in the composition-varied LHPs remains uncertain. Herein, we employed optical spectroscopies and time-resolved microwave conductivity (TRMC) to investigate the dependence of the optical and photoconductive properties of various A-site (formamidinium: FA, methylammonium: MA, Cs) and X-site (Br, I) compositions of LHPs with different underlying CTLs. Intriguingly, it was found that tricationic FAMACs-based LHPs showed more efficient charge separation than bicationic FACs- and FAMA-based ones in a regular structure. Conversely, FACs-based LHPs showed more efficient charge separation than the others in an inverted structure, as evidenced by the prolonged lifetime of TRMC decays. In alignment with these TRMC results, FAMACs exhibited higher device performance in a regular structure than inverted structure. Whereas, FACs showed superior performance in an inverted structure. Hence, our study revealed that the optimal device structure is compositionally dependent on the charge carrier dynamics.

Charge recombination dynamics inside a Cs_0.05FA_0.80MA_0.15PbI_2.75Br_0.25 perovskite film were studied by employing picosecond-microsecond transient absorption spectroscopy. A wide range of excitation intensity from 0.18 to 127 μJ cm^-2 revealed two different charge recombination mechanisms. The charge recombination occurs in the 1^st order with the excitation intensity of <2 μJ cm^-2, while with the higher excitation intensity of >2 μJ cm^-2, the recombination occurs in the addition of the 2^nd order. The analysis of the 1^st order reactions revealed that trap states with at least 3 different potential levels exist in the Cs_0.05FA_0.80MA_0.15PbI_2.75Br_0.25 perovskite film. From the transition of the reaction order from the 1^st to the 2^nd, the trap density inside the perovskite film is evaluated to be 1 x 10¹⁷ cm^-3.

Extreme Ultraviolet Lithography photoresists undergo chemical reactions initiated by ionizing radiation. Understanding the decay pathways in the photoresist following photoionization requires knowledge about the states and species that are generated during the ultrafast primary and secondary ionization processes while the energy of the photons (92 eV) is ultimately converted to heat and chemical reaction products. Here we use Total Electron Yield spectroscopy to investigate the electron generation following excitation of the resist with photons in the energy range from 5 to 150 eV. We estimate that each EUV photon gives rise to 3 – 4 electrons. Changes in the material during irradiation lead to changes in the yield of electrons, which is qualitatively explained by considering changes in the absorption spectrum and density that are due to chemical change.

Medical tubing includes artificial vascular grafts and catheters, each has a different purpose of use, but they both need to hydrophilize the lumen surface. Diamond-like carbon (DLC) is a dry coating technology, and its surface can be easily modified with hydrophilic functional groups. AC high-voltage plasma chemical vapor deposition has been developed for DLC deposition on the inner surface of small-diameter long tubes. In addition, oxygen plasma treatment of the DLC-deposited surface has been performed to enhance the hydrophilicity of the tube lumen and to inhibit biofilm adhesion in urinary catheters. However, the oxygen plasma treatment using silicone as the base material had only a slight inhibitory effect on biofilm adhesion, with a water contact angle of 104.4° for the DLC film and 90.6° for the DLC film, compared with oxygen plasma treatment, with an average value of 119.5° for the blank film. Recently, a new ammonia plasma treatment method has been developed, and an ultra-hydrophilic water contact angle of nearly 10° has been achieved with polyurethan (PU) as the base material. Furthermore, the zeta potential was found to be negative in oxygen plasma treatment and positive in ammonia plasma treatment, indicating that the hydrophilicity, and surface potential can be arbitrarily controlled by combining these plasmas, thereby achieving surface properties suitable for various applications.

Polycondensation of 2-amino-4,6-dichloro-1,3,5-triazine (ADCT) with various aromatic diamines such as m-phenylenediamine (mPDA), 2,4,6-trimethyl-m-phenylenediamine (TMPDA), 4,4’-oxydianiline (ODA), 9,9-bis(4-aminophenyl)fluorene (BAFL), 4,4’-hexafluoroisopropylidenedianiline (BisAF) was investigated. High-molecular weight perfectly linear polyguanamines (PG)s, (M_n ～ 46,000) were successfully obtained for the polycondensation of ADCT with BisAF, while the polycondensation of ADCT with BAFL produced the branched PGs with the degree of branching of from 2.2 to 16.9%. The glass transition temperature and the 5% weight-loss temperature of PGs were in the range of 121 to 325 °C, and 419 to 490 °C, respectively. The optical transmittance of the polymers is higher than 90% at 400 nm wavelength, indicating the high transparency of the materials. The refractive indices of the resulting PGs were from 1.635 to 1.779 at D-line.

Thermosetting bisphenol A-carbonate resins with ethynyl and phenylethynyl terminals were successfully developed via an activated transcarbonate reaction. The terminal transformation efficiency from OH into ethynyl function was 74 to 87% determined by ¹H NMR spectroscopy, and the resin was sufficiently crosslinked with annealing treatment over 240℃. The glass transition temperature increased from 109 to 162℃ with the char yield of 26% at 800℃.

A new method without using a projection lens for easily and inexpensively forming random micro-patterns on large area surfaces and three-dimensional shapes such as steps and curved surfaces was developed in the past research. In the method named “Speckle lithography”, speckle light was used for forming scattered random patterns on surfaces coated with a resist film. In this paper, further miniaturization of patterns was investigated. In a renovated handmade exposure system, the beam diameter of laser beam irradiated to the diffusion plate was expanded from 4 mm to 17 mm using a beam expander. And, the distance between the diffusion plate and the wafer was shortened from 45 mm to 1 mm. As a result, random dot resist patterns with a minimum size of 1 μm or less were successfully formed on entire exposed areas limited to 10×10 mm.

Metal impurities in lithography chemicals is critical to wafer fabrication processes. Since these trace amount of metal impurities is difficult to detect by existing in-line inspection systems, they should be removed as much as possible before wafer processing begins. Metal reduction media implemented as a filter is one strong candidate to remove metals. Ion-exchange type media is typical for metal reduction with the metal reduction mechanism of ion-exchange type media utilizing a strong acid function group such as a sulfonic group. However, lithography chemicals are very sensitive to acidic conditions. For instance, the reaction mechanism of chemically amplified resists utilizes acid catalysis and ester solvent such as PGMEA, which is very widely used as casting solvent for photo resists and underlayer coating materials may be decomposed under acid coexistence. The potential impact of acid presence in ion-exchange type media is a concern. For this reason, we have developed a new metal purifier called “Nylonpolar” to process lithography chemicals in advanced semiconductor applications. Nylonpolar consists of a nylon based membrane and carboxylic group for metal reduction. We were able to confirm that Nylonpolar doesn’t decompose PGMEA solvent, while ion-exchange type media did. Also it was confirmed that Nylonpolar can remove a wide range of metal impurities. This data indicates that Nylonpolar is better metal purifier, especially for lithography process chemicals. Additionally, we have developed another different kind of metal purifier called “MGS2M”. The membrane structure of this metal purifier consists of an ion-exchange type media and acid capture membrane. The acid that was released from the ion-exchange media can be captured by the second acid capture membrane. It was confirmed that MGS2M doesn’t leach the acid, while a more typical ion-exchange type media did. And also, this MGS2M can remove more kinds of metal impurities than typical ion-exchange type media.