A research team led by Shinichi Shikada of the Diamond Research Laboratory of Advanced Industrial Scienceand Technology built a substrate made of artificial diamond. It is 4 cm deep, 2 cm wide, and 0.5 mm thick. The research team enlarged the area of microscopic crystals using methane gas. It plans to build a disc-shaped substrate 5 cm in diameter toward next March. Because it will be put on the production line of LSIs, it will allow for continuous production of power semiconductors. The diamond substrate can resist more than 30 times higher voltage than the silicon substrate and about four times higher voltage than the silicon carbide substrate. In addition, the diamond substrate can reduce the power loss in operation by up to one tenth.
Silicon carbide and gallium nitride are expected to replace silicon as the material of substrate. Mitsubishi Electric is testing subway cars that incorporate silicone carbide power semiconductors in Tokyo, and it successfully reduced the power loss of the inverter by 30%. Because diamond has a higher ability to resist high voltage, it is expected to contribute to energy saving. In addition, should it be used for the power conversion equipment of an electric vehicle, the cooling system will be downsized to make an electric vehicle smaller.
It was generally believed that the practical application of a diamond power semiconductor will be after 2025, but the technology to have built a larger than 5 cm disc-shaped substrate will accelerate the development. A research firm predicts that the world power semiconductor market will increase from 1,860 billion yen in 2011 to about 3,000 billion yen in 2020. Some estimate that replacing silicone by silicon carbide as the material of all power semiconductors will save power equivalent to 8 nuclear power plants with one million kW each in 2020. Diamond and gallium nitride will save power greater than silicon carbide.
A silicon carbide substrate developed by Denso