Silicone tubing is used in small-diameter long-sized tubes for medical applications, such as urinary catheters. However, bacteria in urine adhere to the catheters, forming colonies and biofilms and resulting in blockages and urinary tract infections. Therefore, we have reported a method of AC high-voltage plasma chemical vapor deposition to prevent bacterial adhesion by depositing diamond-like carbon (DLC) on a lumen of a silicone catheter and smoothing the surface. However, the sp3/sp2 structure of DLC on the lumen surface is unresolved, and biomimetic DLC with a functionalized surface has not been investigated. Therefore, we analyzed a flexible membrane structure that can deform as the resin tube deforms. In addition, we developed a lumen surface-modification method using an AC high-voltage burst oxygen plasma processing to bring the DLC surface closer to the in vivo environment. We succeeded in creating biomimetic DLC and introducing carboxyl groups. Using this technology, the surface functionalization of medical tube materials is biocompatible with various protein-adsorption properties.
The adhesive strength of polytetrafluoroethylene (PTFE) film increased drastically by heat-assisted plasma treatment and PTFE indicated cohesive failure inside the PTFE. By increasing the temperature, defluorination progressed. The PTFE treated with H2/He had significantly lower adhesive strength than the PTFE treated with only He. The peak assigned to stretching vibration of -CH2- could be observed only in the film treated with H2/He plasma. From above, we concluded the improvement of the adhesive strength requires the formation of dangling bonds and a crosslinked structure on the PTFE surface.
Biocompatible polymer brushes were successfully synthesized on diamond-like carbon (DLC) films via surface-initiated atom transfer radical polymerization (SI-ATRP) of 2-mtharyloyloxyethyl phosphorylcholine (MPC). The DLC film with a water contact angle (WCA) of approximately 71.9° was modified into a highly hydrophilic surface with a WCA of approximately 15.0° after MPC polymer brush modification. Protein adsorption tests using a quartz crystal microbalance showed that the MPC polymer brush modification dramatically decreased the physical adsorption of bovine albumin and fibrinogen when compared with the DLC film. This indicated an improvement in the surface biocompatibility. Considering that DLC coatings can be applied to various materials such as metals, polymers, and ceramics, MPC polymer brush modification of DLC films would be a versatile technology for improving the surface biocompatibility of a variety of biomedical devices.
We had immobilized cytochrome P450 (CYP) 1A2 and CYP reductase (CPR) onto a self-assembled phospholipid layer containing stearic acid (LDPE-StA-PC-SA) to confirm the functional interaction between CYP 1A2 and CPR. The formation of resorufin from 7-ethoxy resorufin was observed by use of the film immobilizing CYP 1A2 and CPR onto LDPE-StA-PC-SA. It was clarified that the fluidity of LDPE-StA-PC-SA was very important. The actual activity of CYP 1A2 did not depend on the density of CYP 1A2 on LDPE-StA-PC-SA, although its specific activity was affected on its density. The activity of immobilized CYP 1A2 depended on a temperature. It was assumed that the optimal temperature was about 45 ℃.
We have previously developed a photosensitive adhesive material that enables microfluidic channel structure formation and subsequent bonding to a cover with the aim of simplifying the process of wafer-scale microfluidic device fabrication. However, the bonding process and a subsequent curing process required heat treatment at 200 ℃ and 180 ℃, respectively, resulting in the generation of relatively high residual thermal stress. This may lead to delamination, warping, and cracking depending on the application environment. Therefore, in the present study, we designed a new material platform in which the patterning, bonding, and curing processes are based on ultraviolet (UV) reaction of polyfunctional acrylate, tackiness of epoxy resin, and UV/thermal reaction of epoxy resin in order to achieve low residual stress through low-temperature processing. Proof of concept was conducted through the evaluation of various physical properties of the system and found that the new type of photosensitive adhesive material, which bonded to a cover and cured at lower temperatures of 100 ℃ and 120 ℃, respectively, had a low residual stress of 10 MPa and good insulation reliability. This is a promising material for applications such as cooling devices for semiconductor chips, where long-term reliability is required.
In this report, we successfully fabricated the temperature-responsive porous gel film by templating the colloidal crystal (CC) film of silica microparticles embedded in a hydrogel matrix of poly(N-isopropylacrylamide) (NIPA). As elevating the temperature from 25 ℃, this porous gel film showed the color changes of Bragg reflection from red to blue, arising from the geometric decrease in the lattice spacing of pores caused by the shrinkage of NIPA gel matrix upon heating process. Such reflection color changes of the porous gel film were found to be fully reversible in the temperature range between 26 ℃ and 33 ℃. Moreover, Fourier transform infrared (FT-IR) spectroscopy and thermal gravimetric analysis (TGA) measurements suggested that the silica microparticles of CC film are thoroughly removed after treatment with hydrofluoric acid, thereby resulting in the formation of porous NIPA gel film without the silica component. This report provides a promising protocol to check the residual silica microparticles in porous gel films by both FT-IR and TGA measurements.
Semiconductors have continued to grow smaller alongside the development of shorter wavelength exposure sources and the development of photoresists optimized for such exposure wavelengths. For the g-line (436 nm) and i-line (365 nm) exposure wavelengths, novolak resists made of novolak resin have been used for patterning at pattern sizes of 0.5 μm-1 μm. For the exposure wavelength of 248 nm (KrF excimer laser), polyhydroxystyrene (PHS) has been used for patterning at pattern sizes of 0.2 μm-0.35 μm. For the exposure wavelength of 193 nm (ArF excimer laser), acrylic-based resin has been used for patterning at pattern sizes of 30 nm-0.2 μm. With the most advanced current lithography technologies, patterning at pattern sizes finer than 20 nm can be performed using exposure wavelengths of 13.5 nm (EUV). Apparently, then, lithography using novolak resists made of novolak resins is an outdated technology. However, it continues to be employed in LCD processes that involve TFT technology, where the development of higher definition LCDs continues to drive miniaturization. We studied the novolak resist, from synthesis to formulation and to evaluation of its resolution, to reexamine which factors are key to achieving high resolution in novolak resists.
Photo-adhesion of dissimilar materials was performed by using a diacrylate cross-linking reagent containing a 2,2'-dipyridyl disulfide moiety. Cross-linking reagent designed in this work was purified by recrystallization. UV-cured films were fabricated with the cross-linking reagent, 4-hydroxybutyl acrylate and a radical photo-initiator. Hydrophilicity of the film surface seemed to be changed larger than that of control samples. In photo-adhesion experiments, 0.3-2.5 MPa of shear stress was recorded after 1 J/cm2 of UV irradiation at a wavelength of 365 nm. Remarkable improvement of adhesive strength was observed when copper adherends were used, suggesting interaction between copper surface and sulfur atoms of the dipyridyl disulfide moieties in the adhesive layer.
Emission color changes of 4-[bis(4-methylphenyl)amino]benzylideneaniline (BMBZA) and 4-[bis(9,9-dimethylfluoren-2-yl)amino]benzylideneaniline (BFBZA) in response to hydrochloric acid (HCl) vapor and solid organic acids, pentafluorobenzoic acid (PFBA) and benzoic acid (BA), have been investigated in their different solid states. Emission color of BMBZA crystals changed from greenish blue to reddish orange by exposure to HCl vapor, whereas the emission color of BFBZA crystals did not. However, powder sample obtained by grinding the BFBZA crystal exhibited emission color change by exposure to HCl vapor. Similar results of emission color changes of BMBZA and BFBZA crystals in response to PFBA were obtained. In the case of BMBZA–BA and BFBZA–BA systems, grinding of the crystalline mixtures allowed their emission color changes without change in their object colors.
We prepared polysilane–methacrylate copolymers using polysilane as the photoradical initiator. As polymerization is a radical reaction, the chemical structures of the arrangement of the polysilane block and methacrylate have not yet been clarified using various analytical methods. In this study, polysilane–(1-pyrene)methyl methacrylate copolymers were prepared to examine their chemical structure by photoluminescence measurements because the polysilane block and pyrene methacrylate units exhibit fluorescence. The fluorescence analysis revealed the formation of an excimer by the pyrene dimer. From the results, it was found that the pyrene methacrylate units were close to each other.
To suppress degradation of the electrical property of field-effect transistors, the removal of C contamination without damaging oxide films is important in the semiconductor industry. In addition, to reduce bonding failure, it is necessary to remove native oxide films from metal films. To achieve this, atomic hydrogen was generated by the decomposition of H2 gas on a heated tungsten mesh. This surface treatment is referred to as atomic hydrogen annealing (AHA). The reaction of atomic hydrogen with various oxide films, such as AlOx, TiOx, CrOx, NiOx, CuOx, and SiOx, was investigated. The O concentrations in Al, Ti, and Cr slightly decreased by AHA. The thermal oxide films prepared at 400 ℃ were not changed by AHA, except for CuOx. The reduction in the reactivity of the oxide film due to atomic hydrogen depends on the metal–oxygen bond strength. In addition, although the thermal oxide film of the Si substrate prepared at 1000 ℃ was not etched, AHA resulted in the etching of the Si-rich SiOx. These findings are useful for the removal of C contamination and native oxide films and for controlling the surface properties of oxide films.
In a single wafer processing, it is crucial to predict and control liquid film flow flowing over the rotating disk and the chemical solution concentration distribution to achieve efficient cleaning. This study numerically obtained the distribution of liquid film and cleaning solution concentration on a rotating disk using the open-source program, OpenFOAM. We prevented numerical diffusion from liquid to gas by incorporating a conservative scheme into the mass transport equation. The obtained liquid film distribution and surface etching amount agreed with the literature.
This study examined a substrate bias voltage introduced into a microwave excited water vapor plasma to enable fast ashing of photoresist implanted with high-dose ions without occurring popping. The ashing rate at the center of the ashing distribution for the photoresist implanted with boron with an implantation dose of 1×1016 atoms/cm2 was estimated as 1.0 μm/min. Results of plasma emission diagnostics suggest that rf bias application effects generated a plasma rich in excited hydrogen and oxygen atom near the substrate surface. This plasma is presumed to assist the removal of the hardened layer of ion implanted photoresist and to affect hydrogen gas addition. A self-bias voltage during bias application was sufficiently low, approximately －30 V, at a peak-to-peak voltage of 1 kV at 1 MHz.
Microwave-excited water plasma asher (WPA) is our laboratory's new technology for the photoresist (PR) ashing process in semiconductor manufacturing which uses water vapor as process gas. It has the potential to solve many problems of conventional PR ashing technologies including high temperature, oxidation of metal structure, low ashing rate for ion-implanted PR, and high costs of chemicals. In this study, the pressure dependence of various aspects of plasma in water plasma asher, including light emission area, emission intensity, and substrate temperature was investigated. The ashing rate of the novolak PR film on the silicon wafer at the various condition of process pressure was also investigated. Average emission intensity and emission area of plasma significantly increased as process pressure in the chamber were decreased, and they were the highest when the process pressure was 0.3 kPa. The average ashing rate of PR film was only 0.42 μm/min when process pressure was 2.14 kPa, and it gradually increased as process pressure was decreased. It is also found that the ashing rate was improved after reducing the temperature of the water. The ashing rate when using air-rich condition of plasma was observed to be higher than when only water vapor is used as process gas.