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Research paper : R&D of SiC semiconductor power devices and strategy towards their practical utilization (K. Arai)−248−Synthesiology - English edition Vol.3 No.4 (2011) introducing the SiC power device, and a new device industry using the SiC semiconductor would rise (Fig. 3).In the “Development of Ultralow Loss Power Device Technology” project, it was necessary to quickly build the wafer technology and the device process technology that would serve as the foundation of the power device development in Japan, which at the time was mostly basic research. Therefore, the Schottky diode for which practical devices have been developed was not set as the main subject, but the development was narrowed to the basic technology for the switching device that might bring about innovation in power electronics. In this project, the three device manufacturers that were capable of fabricating the FET device -- Hitachi, Ltd., Mitsubishi Electric Corporation, and New Japan Radio Co., Ltd. -- developed the prototypes for different types of FET (MOSFET, JFET, and MESFET) in their laboratories. Concurrently, this was a project in which the integrated basic R&D of material, process, and device was conducted by the industry-government-academia at AIST. This was a concentrated research method where the participating researchers would convene in one place, as a joint R&D with the R&D Association for Future Electronic Devices (Fig. 4). The mixed groups of industry-academia-government were formed for each main elemental technology to engage in the technological development of the SiC semiconductor, since it required different elemental technologies from those for Si semiconductors. This project helped build the foundation of the SiC power device R&D in Japan, along with the NEDO Important Regional Technology Development “Development of Control System Technology for Combustion to Rationalize Energy Use” (FY 1994~1999) that was conducted in the Kansai region for six years from 1994, led by Professor Hiroyuki Matsunami of the Kyoto University (currently director of Campus Plaza Kyoto). In May 2000, an international workshop was held to announce the national SiC R&D to the worldNote 2. This was effective in obtaining international cooperation in the field where there were very few researchers. The development approaches and results that were unique to this project will be described in the next section.3.1.2 Results of the “R&D of Ultralow Loss Power Device Technology” projectAt the time, the SiC wafer was supplied almost exclusively by Cree, Inc. of the United States. When a device manufacturer wishes to invest safety in the product realization of a device, it is necessary to have a second source that can provide a stable supply of the wafers. With the exclusivity of supply, there was concern for the stability of the supply, and as the price and the quality of the wafer depended on one company only, the device company will have less say in the wafers that are linked directly to the cost reduction and performance increase of the device. Therefore, under the concentrated Fig. 3 Effect on energy saving when the SiC device is implemented in JapanThe original figure was published in Kogyo Gijutsu (H. Ishii, Aug 1997) (Fig. 3-a). After several revisions, it was used in the Strategy for Energy Saving Technology (Fig. 3-b).By replacing the Si device to SiC device, the power conversion loss can be reduced to one-third. By 2030, 5.8 million kW of energy can be saved.5.8 million kW203020202010200019900510Power conversion loss (× million kW)Total loss incase ofSi deviceLoss in case of SiC deviceLoss in main power system・ DC transmission・ Power compensation (SVC etc.)Loss in dispersed power supply・ Solar cell・ Fuel cell・ Superconductive power storageLoss in peripheral circuit of power systemLoss in small-medium power systems・ Protecting circuit・ Utility poleLoss in industrial power equipment・ Inverter・ Electric vehicleReduction of conversion loss in main power systemReduction of conversion loss in dispersed power supply of small-medium power systemsReduction of conversion loss in industrial power equipmentSiCbasictechnologyR&D phaseDiffusion of the ultralow loss power device development to power conversionFig. 3-aSiCdevicetechnologyBasic technology for power conversionPower systemtechnologyイメーイメージを Projection by device development planAdvancement of diffusion by supplying high-quality low-cost waferRolling mill26342634Increased use of inverter in motor drive4466Increase build-up by establishing by wafer supply (increase diffusion mainly for motor drive)Computer power supplyDispersed power supplyUninterruptible power supplyElectric vehicle, fuel cell vehicleMotor drive80080048948917661766901901200520102015202020252030Year10002000300040005000Fig. 3-bAmount of energy saved in crude oil equivalent 10,000 kl/y Integrated R&D is necessary ・ Substrate crystal technology ・ Process technology ・ Basic device fabricationIt is difficult to establish the basic technology for the new semiconductor materials SiC and GaN devices, using only the extended Si technology.Substrate crystal growthMaterial scienceDevice scienceDefectDefectDefectElectrode resistanceChannel resistanceChannel resistanceElectrodeActualTheoretical valueTheoretical value for SiSiCVoltage resistanceFabrication and evaluation of basic deviceElemental process technologyOn-resistanceRemoval of causeFig. 4 Development concept of the NEDO project “Development of Basic Technology for Ultralow Loss Power Device”

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