Present Status and Trends of Power Semiconductor Devices

The curtain has been raised on new century. Prior to discussing the present status and trends of power semiconductor devices, allow us to briefly review Fuji Electric’s history with power devices. The semiconductor device was invented and developed in the latter half of the 20th century. When Shockley, Brattain, and Bardeen invented a transistor in 1948, they did not think that this transistor could control a current large enough to turn a motor, we suppose. Transistor devices began as small signal devices and later developed into ICs, and then broadened their range of application to power devices. These new power devices gave birth to new control technology and developed into new power electronics technology. Fuji Electric has been developing power devices and their control technology ever since the early stages, including the power transistor in 1972, and has continued as a leader and developer of this industry. In the 1980s, the highly anticipated MOS (metaloxide-semiconductor) gate power device was introduced. Next, the power MOSFET (MOS field-effect transistor) was invented and was soon followed by the IGBT (insulated-gate bipolar transistor). Production of the power MOSFET utilized the cutting-edge semiconductor technology of those days. Though it was a power device, it required production in a clean room where the cleanliness level was on par with that of necessary for LSI (large-scale integrated circuit) production. Figure 1 shows the progress of device design rules over time. The design rule for LSI memories is also shown for comparison. When the design rule for LSI memories was on the level of several microns in the latter half of the 1970s, the design rule for the power devices of thyristors and bipolar transistors was on the level of several tens of microns. However, when MOS gate devices such as MOSFETs and IGBTs appeared in the latter half of the 1980s, the difference in design rules between these and LSI chips rapidly decreased. In 2000, both achieved device design with sub-micron rules. At present, power devices and LSI chips are produced using equivalent level clean rooms and production equipment. In the “Special issue on MOS gate power device technology” (Vol. 63, No. 9) of the “Fuji Electric Journal” issued in 1990, Dr. Uchida described the MOSFET and IGBT in an article entitled, “Progress of MOS-gate power device technology.” At that time, Fuji Electric was marketing 2nd generation IGBTs and was promoting the development of 3rd generation IGBTs. We predicted future development of the IGBT through improving the characteristics, adding intelligence and increasing capacity. The capacity of power devices has also undergone great changes. Figure 2 shows the progress in capacity of Fuji Electric’s power devices over time. Power devices started as discrete transistors in the 1970s, then changed to transistor modules, and then to IGBT modules in the latter half of the 1980s. In 2000, a flatpackaged IGBT device rated at 4.5kV-2kA appeared. Please refer to the separate article in this special issue for details of this flat-packaged IGBT. In the “special issue on power semiconductor devices” (Vol. 72 No. 3) of the “Fuji Electric Journal” issued in 1999, Dr. Shigekane described the year of 1998 as a historical year for the research and development of power devices in “Present status and trends of power semiconductor devices.” He cited the ISPSD (International symposium on power semiconductor devices & ICs) tenth anniversary symposium held in Kyoto as the reason for its historical importance. The