INTRODUCTION

The Institute of Space and Astronautical Science (ISAS) belongs to the Ministry of Education. Its members perform many research projects related to space exploration. Its mission is similar to that of the NASA Jet Propulsion Laboratory of the United States.

The panelists met Prof. Tajima of ISAS in the Ministry of Education. Professor Tajima mentioned a national project on low-loss power devices organized by ETL under Dr. Arai. Its focus is mainly SiC, and many power device manufacturers support it. Since this project will be overseen by ETL, which the TTEC panel would visit the next day, Prof. Tajima told the panel to seek the details while it was meeting Dr. Arai and his colleagues at ETL. Prof. Tajima has organized many national conferences on high temperature electronics, and he gave the panel the proceedings of all but one. He mentioned several Japanese companies working on SiC that the panel was not visiting. These include Hoya, which makes 3C-SiC epi layers on Si substrates, Hitachi, Fuji Electric, and Toshiba.

Prof. Tajima has given invited lectures on high temperature electronics applications. These include geothermal probing and exploration of the inner planets and the sun. He introduced to us the background of his laboratory by showing a 30-min video on space phenomena. Some of the highlights were the northern lights and X-ray astronomy.

Prof. Tajima's background is in semiconductor physics, particularly impurity and defect analysis, large-diameter wafers, SOI wafers, GaAs, InP, and Si/Ge. His previous material studies include photoluminescence (PL) mapping of production-grade 6H- and 4H-SiC bulk and epitaxial wafers. By using a microcomputer-controlled PL system, he and his colleagues have characterized p-type bulk and epitaxial wafers and found a nonuniform distribution of unidentified deep levels on the wafer. Prof. Hirose, his colleague present at the meeting, is an interfacial specialist on the SiO₂/Si system. There is no packaging expert at ISAS. Prof. Tajima's interests in high temperature electronics generally concern space exploration. In particular, high temperature devices are needed for a Venus probe that will be dropped from an orbiting satellite. Venus is covered with clouds of sulfuric acid, and the surface temperature is about 450° C. The temperature below the clouds, at an altitude of 20 km, is about 350°C. A balloon floating below the clouds can explore the mystery of the 4-day rotation of Venus. A 5-kg probe will be used, and 1 kg would be saved without the cooling system. The electronics need to be operating for 1-2 weeks.

The mission was one of the strongest potential project candidates planned for 1999, which would have been an appropriate window for Venus. Unfortunately, the project was not accepted by ISAS, and the next target launch has not been decided. Nevertheless, interest in the Venus mission is still very high, and feasibility studies are underway.

Prof. Tajima indicated that due to budgetary uncertainties, he was not sure about the exact scope and nature of the high temperature device activities that will take place at ISAS. The power level at which high temperature devices will be considered is > 100 W. Characterizations of wide bandgap materials and silicon-on-insulator are the main emphases. Besides the active devices, Prof. Tajima expressed concern about the temperature limitations (<200° C) of passive components, such as capacitors. He mentioned Kyocera, a company which develops high temperature ceramic packages in Japan. Also, he believes that the basic parameters of the wide bandgap semiconductors are not known well enough, but ISAS will not determine them. Prof. Tajima's group will continue to collaborate with universities and industrial companies. He has also proposed to perform device and material research in SiC.

The Japanese space market is much smaller than the U.S. market. A large number (>10) of Japanese companies will participate in the National Project on Low-Loss Power Devices, but the expected SiC market may be a small though important niche.

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