AIST Stories No1
19/36

Impact in the following fields! Community lifeIndustry◦Home◦Environment◦Infrastructure◦Transport◦Electronics◦Motor vehiclesInto the future AIST!17at a glanceTerminologyThe goal of the development was higher-performance power devices using SiC, and higher-performance electrical equipment incorporating these power devices.Hajime Okumura, Director of the Advanced Power Electronics Research Center, reflects on those times: “Development in which the semiconductor material was simply replaced with silicon carbide was very difficult. There were many defects in the early silicon carbide wafers and we did not have the technology to produce large-diameter substrates.”The road to industrial-scale application did not open up until costs were reduced by improved yields of larger wafers. To make the required technologies that had been developed through NEDO projects suitable for mass production, AIST used its own funds to set up an organization for collaborative research with businesses, specifically Fuji Electric Co., Ltd. and ULVAC, Inc.The goal is efficient use of electricity and strengthening international competitivenessEstablishing production technologies that do not result in defects is critical for mass production. As well as R&D of devices for practical use as power devices, R&D for related technologies at the same time is necessary. Development has been pursued to raise the technical maturity of all aspects.The key to improving the quality of SiC power devices was in the production of MOSFETs*2 (metal oxide semiconductor field effect transistors) in 2002, when we developed a device structure, with an ion implantation epitaxial structure*3 on the carbon surface of silicon carbide wafers; these provided good electron transport characteristics. Using this structure, we managed to produce samples of low-loss power devices with world-beating performance in 2006. Now, being shipped are general-purpose inverters and power conditioners for solar power that are equipped with power semiconductor transistors and diodes for the 1 kV range; this range of devices has the highest sales volumes. We have also achieved a great reduction in the sizes of the inverters.“As well as replacing previous devices, silicon carbide power devices will be suitable for fields in which power electronics has not previously been used; so, we can expect even more efficient use of electricity and more energy savings. The result will be that Japan’s semiconductor industry will become more competitive.”Our research and development is now focused, from the wafer level to the system level, on power devices in the multiple kV range, to be used in railways and other heavy electric equipment.“In the long term, we aim to develop devices with ultra-high breakdown voltages, of 10 kV and above, to be used in smart grids and the like. To grow the market, high-reliability power transistors to be used in the next generation of cars will be the key target. Energy supplies are a very big issue for Japan in particular. We are working to establish a portfolio of technologies for the new energy electronics.”*1 Silicon carbide (SiC): A compound of equal numbers of carbon and silicon atoms. Also known as carborundum. It has properties between those of diamond and silicon: very hard with excellent chemical stability and thermal conductivity. As well as being used as a semiconductor material, its uses include polishing and grinding, and emergency brakes for mountain railways.*2 MOSFET: Short for “metal oxide semiconductor field effect transistor”, a fundamental element of integrated circuits. On a substrate of a semiconductor such as silicon, a gate electrode is formed on an oxide layer and source and drain electrodes are formed at two sides of the gate electrode, thus forming the field effect transistor.*3 Epitaxial structure: A technology for growing thin films of crystal. A number of crystalline films of semiconductor are layered on a semiconductor substrate.Comparing the efficiency of Si and SiC power devicesCompared to Si power devices, SiC power devices are less wasteful and can utilize power even when generation levels are low. The graph to the right shows that SiC power devices exhibit higher power conversion efficiency than Si power devices in a low load region (the region in which generation levels are low).SiC power deviceSiC power deviceWorking at rated outputCurrent (A)100500012325%50%Voltage (V)75%100%Si power deviceSi power deviceEfficiencyLoad factorBreakdown voltage: 1200 VImproved efficiency inpractical operationsThe SiC power device has a much better efficiency than the Si power device at low loads.Mass production samples of SiC components formed on 3-inch wafersSource: Focus NEDO No. 48 (March 2013, NEDO)Impact in the following fields! Community lifeIndustry◦Home◦Environment◦Infrastructure◦Transport◦Electronics◦Motor vehiclesInto the future AIST!17at a glanceTerminologyThe goal of the development was higher-performance power devices using SiC, and higher-performance electrical equipment incorporating these power devices.Hajime Okumura, Director of the Advanced Power Electronics Research Center, reflects on those times: “Development in which the semiconductor material was simply replaced with silicon carbide was very difficult. There were many defects in the early silicon carbide wafers and we did not have the technology to produce large-diameter substrates.”The road to industrial-scale application did not open up until costs were reduced by improved yields of larger wafers. To make the required technologies that had been developed through NEDO projects suitable for mass production, AIST used its own funds to set up an organization for collaborative research with businesses, specifically Fuji Electric Co., Ltd. and ULVAC, Inc.The goal is efficient use of electricity and strengthening international competitivenessEstablishing production technologies that do not result in defects is critical for mass production. As well as R&D of devices for practical use as power devices, R&D for related technologies at the same time is necessary. Development has been pursued to raise the technical maturity of all aspects.The key to improving the quality of SiC power devices was in the production of MOSFETs*2 (metal oxide semiconductor field effect transistors) in 2002, when we developed a device structure, with an ion implantation epitaxial structure*3 on the carbon surface of silicon carbide wafers; these provided good electron transport characteristics. Using this structure, we managed to produce samples of low-loss power devices with world-beating performance in 2006. Now, being shipped are general-purpose inverters and power conditioners for solar power that are equipped with power semiconductor transistors and diodes for the 1 kV range; this range of devices has the highest sales volumes. We have also achieved a great reduction in the sizes of the inverters.“As well as replacing previous devices, silicon carbide power devices will be suitable for fields in which power electronics has not previously been used; so, we can expect even more efficient use of electricity and more energy savings. The result will be that Japan’s semiconductor industry will become more competitive.”Our research and development is now focused, from the wafer level to the system level, on power devices in the multiple kV range, to be used in railways and other heavy electric equipment.“In the long term, we aim to develop devices with ultra-high breakdown voltages, of 10 kV and above, to be used in smart grids and the like. To grow the market, high-reliability power transistors to be used in the next generation of cars will be the key target. Energy supplies are a very big issue for Japan in particular. We are working to establish a portfolio of technologies for the new energy electronics.”*1 Silicon carbide (SiC): A compound of equal numbers of carbon and silicon atoms. Also known as carborundum. It has properties between those of diamond and silicon: very hard with excellent chemical stability and thermal conductivity. As well as being used as a semiconductor material, its uses include polishing and grinding, and emergency brakes for mountain railways.*2 MOSFET: Short for “metal oxide semiconductor field effect transistor”, a fundamental element of integrated circuits. On a substrate of a semiconductor such as silicon, a gate electrode is formed on an oxide layer and source and drain electrodes are formed at two sides of the gate electrode, thus forming the field effect transistor.*3 Epitaxial structure: A technology for growing thin films of crystal. A number of crystalline films of semiconductor are layered on a semiconductor substrate.Comparing the efficiency of Si and SiC power devicesCompared to Si power devices, SiC power devices are less wasteful and can utilize power even when generation levels are low. The graph to the right shows that SiC power devices exhibit higher power conversion efficiency than Si power devices in a low load region (the region in which generation levels are low).SiC power deviceSiC power deviceWorking at rated outputCurrent (A)100500012325%50%Voltage (V)75%100%Si power deviceSi power deviceEfficiencyLoad factorBreakdown voltage: 1200 VImproved efficiency inpractical operationsThe SiC power device has a much better efficiency than the Si power device at low loads.Mass production samples of SiC components formed on 3-inch wafersSource: Focus NEDO No. 48 (March 2013, NEDO)

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