Teruhiko Yamazaki

Superconductivity of Screen-Printed YBa2Cu3Oy Thick Films on Y2BaCuO5 Substrates

YBa2Cu3Oy superconducting thick films have been prepared on Y2BaCuO5 substrate by the screen printing and sintering method. The critical temperature Tc and current density Jc at 77 K in an absence of magnetic fields were extremely high as compared with the films printed on the other ceramic substrates such as MgO, SrTiO3 and YSZ, and were 86 K and 3000 A/cm2, respectively.

Gas Plasma Etching of Chromium Films

The etching of Cr film was investigated employing mixtures of CCl4 with CO, CO2, or O2. The highest etch rate ratio of the Cr film to the photoresist was given by the combination of CCl4 with CO2, and the Cr film could be etched successfully without serious loss in the pattern width using this CCl4/CO2 mixture. It is speculated that O(3P) contributes to the etching reactions of chromium films. Spectrometry revealed that singlet oxygen radicals contribute to the decomposition reactions of the resist films in the plasmas. Using this novel gas plasma etching technique, photomasks for MOS LSI were made with good pattern width control.

The Application of Hydrogenation to Amorphous Silicon Thin Film Transistors for the Decrease of the off Current

The influence of hydrogenation on OFF current of TFTs with a bottom gate staggered structure has been investigated. The hydrogenation is done by exposing the surface of the a-Si:H channel layer to H2 plasma. The hydrogenation decreases the OFF current by more than one order of magnitude. The decrease in the OFF current is attributed to the increase in the density of states at the interface between the a-Si:H channel layer and the SiN passivating layer.

The Role of a Photoresist Film on Reverse Gas Plasma Etching of Chromium Films

The role of a photoresist film on reverse gas plasma etching of chromium photomask plates has been studied. The variation of etching profiles has been observed using SEM techniques. It is speculated that a WO3 layer on the chromium film forms a masking layer to the etching and that the WO3 layer can be removed by decomposition of the photoresist film in the plasma. A study of the relation between photoresist thickness and etching time has shown that there is an optimum photoresist thickness for each WO3 concentration in the chromium film.

An analysis of source bus-line to common-electrode coupling effect in large-area TFT-LCDs

— The source (or data) bus-line to common (or backplane) electrode coupling effect in TFT-LCDs has been investigated through experiment and simulation using a new model. The important feature of this simulated model is that the common electrode consists of a network of discrete resistors. The horizontal crosstalk is caused by this coupling effect, and the mechanism of the crosstalk has become clear by the simulation of 5-in. TFT-LCDs. By adopting this simulation, useful information for large-area TFT-LCD designs can be obtained. As an example, this simulation has been performed for 10- and 15-in. TFT-LCDs and the requirement for a common resistance has been illustrated.

Fabrication of 10-in.-diagonal 16-gray-level TFT-LCDs by novel processing technologies

— New processing technologies for large-area high-resolution TFT-LCDs have been developed. A taper-etching technology for Cr gate electrodes with a resistivity of 18 μΩ/cm was realized. The technology allows control of the taper angle down to as low as 2°. The breakdown voltage between the gate electrodes and the source-drain electrodes was improved from 140 V to over 400 V. A new end-point-detection method using N2 plasma emission for the photoresist stripping process has been developed. The method decreases the contact resistance and improves the transfer characteristics of TFTs. These processing technologies make possible the realization of 10-in.-diagonal TFT-LCDs with 16 gray levels.

A High Performance Negative X-Ray Resist : CPMS-X(Pd)

The characteristics of CPMS (chlorinated polymethylstyrene) to Pd Loc were investigated to obtain the high performance negative x-ray resist. From the results, the high sensitive x-ray negative resist (Dg0.5=17mJ/cm2), CPMS-X(Pd), were obtained by determining both the optimum molecular weight and the optimum chlorine content to Pd Loc. It was found that this resist also has both high contrast and high dry etching resistivity. This resist can be believed to be a milestone for practical use of x-ray lithography for future VLSI devices.

Negative resist profiles in x‐ray lithography

The processing characteristics of a negative resist (CPMS) exposed with a x‐ray exposure system are studied by a comparison between developed profiles and calculated results of absorbed energy in the resist. In fine lines, reduction in volume is caused by vertical and horizontal shrinkage. In patterns which cover large areas, where the resist is fixed to the substrate by the adhesion between the resist and the substrate, the reduction in volume is mainly caused by the vertical shrinkage, while the horizontal shrinkage causes deformation of the profile at the pattern edge. This fact means that the normalized thickness for the large patterns agrees with the volume reduction ratio for the fine lines. These results are applied to a simulation program to estimate the profiles of the negative resist exposed with a x‐ray exposure system. The program is based on the sensitivity curve of the resist. The theoretical results calculated with the program agree well with the experimental results in the case where penum...

Numerical Analysis of the Optical Response Characteristics of Thin Film Transistor Addressed Liquid Crystal Displays

A simulation method is proposed to analyze the optical response characteristics of TFT-LCDs. Our method using an equivalent circuit takes into account the time and voltage dependence of the dielectric constant of the TN-LC cell. We obtain good agreement between simulations of the optical response characteristics of the TN-LC cell and experimental results. The 30 Hz flicker, which appears in the optical rise state of the TFT-LCD, is analyzed by using our method. Our method enables a large amount of calculation of the optical response characteristics of TFT-LCDs at high speed.

An All Dry Mask Making Process by Gas Plasma

An all dry mask making process is demonstrated in which gas plasmas are used. A photoresist film was exposed to an electron beam with dose range of 2.5×10-4C/cm2 to 5×10-4C/cm, and the resist film was dry developed using a wet air gas plasma. Dry developed resist patterns were obtained with good edge quality. The dry developed patterns were very thin films. A chromium photomask film was successfully etched using a mixed gas plasma of CCl4 and air. From the data obtained by an FT-IR analysis, it is speculated that the phenolic hydroxy group which has a high resistivity to the gas plasma environment was formed in the resist film by electron beam radiation.