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Research paper : R&D of SiC semiconductor power devices and strategy towards their practical utilization (K. Arai)−247−Synthesiology - English edition Vol.3 No.4 (2011) band gap semiconductors in practical application”.2.3 Goals during the AIST period (2001~2007)The ETL was reorganized as AIST, just when ETL was playing its role in the concentrated research for the “Development of Ultralow Loss Power Device Technology” (FY 1998~2002), a project of the New Energy and Industrial Technology Development Organization (NEDO). Through the discussions with the researchers of the power electronics application in the “Next-Generation Power Semiconductor Realization Commission” conducted under the project, we became aware that “although the power device may be the key to power electronics, collaborative development along with the development of converters and system application is mandatory in order to realize the power device”. Proposal was made to establish the Power Electronics Research Center (PERC) that engaged in the integrated R&D from material and device development to converter and system application. This was approved. The goal of this research center was “to clarify the contribution to the ubiquitous power electronics (that is the innovation in power electronics) by increasing the performance of the SiC power device and to gain prospect for its system application”.2.4 Goals of the AIST period (2008~)As the activities at PERC was recognized and the decision was made “to act in unison as a R&D group to take the next step” at AIST, the Energy Semiconductor Electronics Research Laboratory (ESERL) was established to follow PERC in 2008. The next goal was “to continue the integrated effort of wafer and material technology, device technology, and systemization technology, and to generate innovations in power electronics by accelerating the practical utilization and diffusion of the SiC power devices”.3 Issues extracted, strategies to solve the issues, and the results during each period3.1 Strategies and results of the ETL period- Construction of the foundation of the SiC power device development in Japan -At ETL, a pioneering R&D was conducted where the 3C-SiC (cubic crystal), which was the low-temperature polymorphism of the SiC crystal, was hetero-epitaxially grown on the silicon wafer and the prototype diodes and transistors were fabricated to demonstrate the device property[2]. The SiC device R&D projects supported by the government in the 1980s were started together with the “superlattice device” project and “3D circuit device” project under the “R&D Program on Basic Technologies for Future Industries”. However, as the main goal was the environment (heat and radiation) resistant devices (mainly GaAS devices), the industries felt very little attraction and the projects were continued with minor effort. In the beginning of the 1990s, the 30 mm diameter SiC monocrystal (hexagonal crystal) became commercially available in the United States, and the expectations for SiC in the power device began to rise.3.1.1 Narrowing down to SiC for use in power device and concentrated research methodIn the United States, the R&Ds for SiC and diamond as the electronic devices for military application became active under the support of the US Defense Advanced Research Projects Agency (DARPA). In Japan, it was necessary to clarify the positioning of the wide-bandgap semiconductor R&D for the purpose of industrial application. In 1994, the survey of the necessary fields and the available technology was started under the Japan Electronics Industry Development Association (JEIDA). It was proposed that the wide-gap semiconductor SiC, GaN, and diamond would be the semiconductor materials that may enable a device that was resistant to extreme conditions such as high-power, high frequency, and extremely severe environments. It may pioneer a new electronic field called “hard electronics”[3] (Fig. 1). After two years of NEDO leading research “Hard Electronics” (FY 1996~1997), the goal was narrowed down to the development of the basic technology for the low-loss power device that might have great impact on industry, focusing on SiC for which the commercial sale of two-inch wafers was started. The five-year NEDO project “Development of Ultralow Loss Power Device Technology” (FY 1998~2002) was started in 1998 (NEDO and Research and Development Association for Future Electron Devices (FED)). The project was powered not only by the statement, “Although this R&D is conducted for military application in the United States, the basic research that has potential of blooming as an industry should be supported by the Ministry of International Trade and Industry (the present Ministry of Economy Trade and Industry (METI))”, but also by emphasizing that a great energy saving can be expected by Fig. 2 Roadmap of power converter seen in terms of power densityThere has been a double-digit increase in the last 30 years. While the efficiency of the converter is becoming saturated, the increase of power density will lower the cost of the converter, and this will be a major point for the diffusion. The demonstration of R&D sample is necessary 10 years ahead of the product realization (R&D line).YearH. Ohashi, Ceramics, 40 [1], 29-33 (2005)H. Ohashi, IEEJ, 122 (3), 168-171 (2002)R&D Product realizationInverter for HEVSiC inverterGeneral-purposeinverterInverter for air conditionerPackage power sourceUnit powersourceThyristor valveBoard powersourcePower density (W/cm3)0.011001010.1197019801990200020202010

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