(Invited) Impact of Stacked AlON/SiO2Gate Dielectrics for SiC Power Devices

We propose the use of an aluminum oxynitride (AlON) gate insulator for SiC-based MOS power devices. Although direct deposition of AlON on 4H-SiC substrate causes electrical degradation, the fabricated MOS capacitor with AlON/SiO2 stacked gate dielectric shows no flatband voltage (VFB) shift and negligible capacitance-voltage (C-V) hysteresis. Owing to the high dielectric constant of AlON, as compared to single SiO2 insulator, significant gate leakage reduction was achieved even at high-temperatures, especially in high electric field condition. Moreover, in order to improve electrical properties of thermally grown SiO2/SiC interfaces, the impact of a combination treatment of nitrogen plasma exposure and forming gas annealing (FGA) was investigated. We found that channel mobility enhancement of SiC-MOSFETs was consistent with the reduction in interface state density (Dit) depending on the process conditions of the combination treatment, and obtained 50% mobility enhancement, while maintaining low gate leakage current.