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From the view point of safety and maintenance simplicity, the development of high performance gas cooled gas insulated transformer has been desirable. In this type of transformer, the coolant gas is circulated in the gap between the coils to cool it. The flow pattern of coolant in the flow path strongly depend on its configuration formed by the coil. Therefore, in order to achieve high cooling efficiency of coils and at the same time to reduce the pressure loss, it is important to have sufficient knowledge about the flow behavior in the coil flow path. In the present work, in order to decide appropriate flow path configuration formed by the coil foi its efficient cooling, flow visualization study based on numerical simulation was performed. This study led to the understanding that for the standard coil flow path configuration there occurred recirculating flow covering a region of stagnation which caused increase in coil surface temperature and in efficient for cooling. In order to prevent the occu ?? ence of recirculating flow, a modified flow path configuration is proposed to have efficient cooling.

The nonuniform distribution of fillers in a composite is studied both experimentally and analytically. A set of three parameters are proposed to characterize the distribution patterns of fillers: homogeneity distribution parameter ξ, anisotropy parameter of the first kind η and that of the second king Φ. These parameters are used to examine the distribution patterns of 10% and 20% SiC particulate/6061 Al (SiCp/Al) composite. The distribution pattern is also examined from the viewpoint of fractal analysis

A Device mask of 180nm generation was fabricated by Photomask Repeater system and the performance of it proved to be high by the results of fabricated mask. Great margins between the results of the fabricated mask and specifications suggest that lower graded masks can be used as master masks. From this point of view, error budgets were estimated about CD uniformity and pattern placement. The required specifications for master mask were estimated for 180nm and 130nm lithography. In CD uniformity the specification is 50nm(3?) for 180nm and 30nm(3?) for 130nm lithography. In pattern placement the specification is 75nm(3?) for 180nm and 50nm(3?) for 130nm lithography. In defect size the specification is lOOOnm for 180nm and 900nm for 130nm lithography. The requirements of master mask are rather rough even for 130nm lithography and enough realistic.

We have developed a new reticle exposure system, which can fabricate 150nm generation masks by means of a stitching exposure technique. We call this exposure system the Photomask Repeater, or high accuracy repeater (HR). HR is a modified i-line stepper for mask manufacturing with a field size of 22 by 22 mm in a single exposure. However, the device size on a 4x mask is larger than 22 by 22 mm. Furthermore the improvement in mask CD uniformity is required. For this purpose the exposure field size was extended with the use of 'seamless stitching technology'. This is the key to obtaining a feasible exposure system with the use of this method. Results have been achieved with this system showing CD variation of less than +/- 5 nm across a 1D seam band by means of a 'gradation filter'. Moreover, overall Cd uniformity is less than 13nm, while image placement accuracy is less than 24nm. HR is an attractive system for SoC mask manufacturing, and is also effective in reducing TAT.

New pattern generation system, Photomask Repeater, based on i-line stepper has been developed. This system can transfer device patterns from master masks onto a photomask plate with 22mm field size. To print a chip larger than the 22mm field, stitching technology has been developed. Critical dimension error in the region where fields are stitched is the key issue of this technology. Quantification of critical dimension deviation induced by field misplacement was carried out by calculation. Introducing exposure dose gradation, it was reduced less than 1.5nm. From measurements of a real exposed mask this technique proved to be able to stitch fields seamlessly. Major two specifications, pattern placement accuracy and critical dimension uniformity, were evaluated. Both specifications required for 150nm photomasks were fully satisfied. Availability of the photomask repeater to memory device and system on chip is discussed.

New pattern generation system, Photomask Repeater, based on i-line stepper has been developed. This system can transfer device patterns from master masks onto a photomask plate with 22mm field size. To print a chip larger than the 22mm field, stitching technology has been developed. Critical dimension error in the region where shots are stitched is the key issue of this technology. Quantification of critical dimension deviation induced by shot misplacement was carried out by calculation. Introducing exposure dose gradation, it was reduced less than 1.5nm. Form measurements of real exposed mask this technique proved to be able to stitch shots seamlessly. Major two specifications, pattern placement accuracy and critical dimension uniformity, were evaluated. Both specifications required for 150nm photomask were fully satisfied. Availability of the photomask repeater to memory device and system on chip is discussed.

Cluster approximation for the antiferromagnets is improved by extending the effective Hamiltonian method so that there appears no anti-Neel point. It is applied to the S =1/2 antiferromagnet on a square lattice with anisotropic exchange interaction which includes the anisotropy parameter η. This system is reduced to the Heisenberg model or to the Ising model according as η goes to 1 or 0. The variations of the Neel point T N and the specific heat with η are calculated. The results of the specific heat curves for \(\eta{\gtrsim}0.9\) exhibit a broad maximum above T N where a small spike appears.

Vacuum fusion gas extraction techniques using platinum-nickel bath at 1800°C and platinum baths at various temperatures from 1900°C to 2050°C were examined to determine microgases in molybdenum and the maximum permissible molybdenum content in fluid platinum for effective gas extraction. And microscopic examination was also carried out in order to see the graphite precipitated from bath alloys.Gases were extracted out of electrolytically polished one-gram samples cut off from a sintered, swaged molybdenum rod used in the previously described nickel bath technique and others, in which gaseous impurities might be distributed homogeneously. And, in the 2050°C platinum bath technique, two- or four-gram samples from arc-melted molybdenum ingots were also used to determine the maximum permissible molybdenum content in platinum bath at this temperature. Extracted gases were analyzed by means of the fractional freezing under low pressure, and the sensitivity of measurement was, in these experiments too, O.5 micron-liter for both oxygen (as carbon monoxide) and hydrogen analyses, and 0.05 micron-liter for nitrogen.The allawance for reproducibility of analysis of experimental one-gram samples was +1 part per million by weight for both oxygen and nitrogen below about 30 ppm. and 10 ppm. respectively and ± 0.1 ppm. for hydrogen below about 1.0 ppm., same as the experiments described in the paper I. And the following results were found : (1) Oxygen analyses by using the platinum bath technique gave the results which were by about 10 ppm. (about 11 micron liters of carbon monoxide evolved from one gram sample) greater than about 18 ppm. obtained by using the platinum-nickel, nickel, and nickel-tin baths, these facts suggesting the sorption of evolved carbon monoxide on the film or vapor of nickel evaporated from baths ; (2) Each result of nitrogen and hydrogen analyses by using the platinum bath technique agreed with that by the solid extraction technique mentioned before, within errors of 1 ppm. and 0.1 ppm. respectively ; (3) The maximum permissible molybdenum contents in a fluid platinum bath for extracting gases were about 70 per cent by weight at 2050°C, about 20 per cent at 2000 °C, and about 10 per cent at 1950°C ; (4) Accordiding to the microscopic examination of bath alloys, graphite flakes precipitated from fluid platinum-carbon or platinum-molybdenum-carbon alloy were so much less than those from fluid nickel-carbon or nickel-molybdenum-carbon alloy, that the control of carbon content in platinum bath by addition of pure platinum was unnecessary, in contrast with the case of nickel or iron bath.From these experiments following the previous ones, it can be concluded that the vacuum fusion gas extraction technique by platinum bath at 2050°C is the most reliable and useful one for micro-gas analysis of molybdenum.