Vol.3 No.4 2011

12/72

Research paper : R&D of SiC semiconductor power devices and strategy towards their practical utilization (K. Arai)−253−Synthesiology - English edition Vol.3 No.4 (2011) and to engage in pioneering research that may contribute to further developments in this field.With the demonstration of the 70 % loss reduction for the 14-kVA inverter by a company in the “Inverter” project and the potential for the device application at the current crystal quality through the concentrated research method, the “Basic R&D for Future Power Electronics” (FY 2008~2011) started within the framework of the Green IT project from FY 2008. There, the demonstration of power electronics device with clear application was conducted by Hitachi Ltd. and Mitsubishi Electric Corporation, as well as the basic technology development aiming for the high power density (development of the ultralow loss device and demonstration of the prototype for the high power density converter) through the third concentrated research at AIST.In the development of the wafer technology, the development of the four-inch wafer was accomplished in Japan in the end of 2007, and this accelerated the practical utilization. In the sublimation crystal, issues remain in increasing the diameter (six inch or more) to reduce the cost of the device, as well as other cost issues such as the productivity of cutting and polishing technologies. The epitaxial technology plays an important role in the formation of the device structure, and the diffusion of high-quality epitaxial technology is also important. Moreover, it is necessary to pursue the new growth technology to replace the sublimation method to increase the crystal quality, and we are starting activities to address those issues.SiC power electronics was undergoing an evolution in the wafer and device developments, and the interest in its practical utilization was rising. However, for the wafer industry, the demand projection was unclear, and industry was hesitant to make any large-scale investments. For the device industry, the market projection considering the quality and cost of the wafer was unclear, and it was difficult to make a decision for full production. Also, for the companies involved in system application, the device was not readily available. The situation was a so-called “three-party deadlock”. It was necessary to provide support so this relationship would turn into positive feedback for each other. The technological support for the wafer industry, where the expensive epitaxial growth device was the bottleneck for commercialization, came in the form of ESICAT Japan, LLP.At AIST, the “Industrial Transformation Research Initiative”, the large-scale collaborative project of industry-academia-government, was conducted for several topics. From the end of the FY 2008, the Industrial Transformation Research Initiative “Mass Production of SiC Device Prototype and System Application Demonstration” started its three-year course. Through the collaboration with a device company, Fuji Electric Holdings Co., Ltd., we aim for a practical production technology for the device chip, to quickly supply the device chips to the companies and universities that are attempting system application to the converter, and to clarify the potential of the application field.4 Evaluation of the strategy4.1 ETL Period4.1.1 Narrowing down the development target to SiC power deviceThrough the exchange with the people in charge of surveys and policymaking, the target of “Hard Electronics” was narrowed down to the SiC semiconductor, where the wafer development was already being done to create the power device. We were able to clarify the vision of creating a new industry and the contribution to energy saving. Through long-term survey, the system for a national project became possible. Flexible responses were made to accommodate industry, and the dispersed research method (involving three companies) for the device development and the concentrated research method that aimed for the construction of basic technology functioned effectively. These were extremely useful for the development of this field later.4.1.2 Space for the start-up of R&D and procurement of human resources At ETL, the project started as a group of participants and post docs within the institute mainly among the material and property researchers. In the concentrated research method, the role played by the participants of the companies was large, along with the use of the corporate facilities. The material and property researchers employed as post docs were encouraged to grow into people who could take charge of the device process, and they would eventually engage in prototype production of simple devices. Care was taken in the management, such as holding frequent meetings to raise the morale and research potential. The procurement of space needed for the facility was extremely difficult. If there were appropriate space, we would have moved, but the burden of moving was too great on the staff, and we became painfully aware of the importance of infrastructure in device development. At the beginning of the project, some thought that we could stay at crystal growth and epitaxial growth in the concentrated R&D method. However, effort was spent to fabricate the device prototype under thinking “the essence of the material could only be seen when it is made into a device”. Taking a long view, this was a good decision for the continuation of the R&D.4.2 AIST period (2001~2007)4.2.1 Establishment of the research center and proposal of the total solutionBefore the waves of free economy changed the Japanese society, the R&D for social infrastructures such as power and communication was led by the electric power company

※このページを正しく表示するにはFlashPlayer9以上が必要です