High temperature SiC trench gate p-IGBTs

Various design issues pertaining to SiC-based IGBTs are described. A trench gate, p-channel IGBT was considered the most appropriate structure for fabrication in SiC. The fabrication and characterization of high temperature SiC IGBTs with high current levels are presented. Using optimized emitter processing, 6H-SiC p-IGBTs show a higher current capability than 4H-SiC p-IGBTs because of their lower emitter contact resistance and higher MOS channel mobility. Since IGBTs rely on minority carrier injection, the low bulk mobility parallel to the c-axis in 6H-SiC was not found to severely affect the current carrying capability as compared with 4H-SiC IGBTs in the present design. Measured results of these devices are described from room temperature to the 350-400°C temperature range. For both polytypes, the current capability was found to be much larger when their MOS gates were fabricated in the 112~0 crystal direction compared with the 1100 crystal direction. The emitter (p-type) contact anneal was also found to significantly affect the performance of SiC IGBTs. 4H-SiC IGBTs showed a -85 V blocking capability (room temperature) and on-current of 100 mA at 350°C. 6H-SiC IGBTs were demonstrated with -400 V blocking capability (at 25°C) and 2 A at 400°C.