(Invited) Gate Stack Technologies for SiC Power MOSFETs

Abstract

Silicon carbide has gained considerable attention for future power electronics. However, it's well known that SiC-based MOS devices have suffered from degraded electrical properties of thermally grown SiO2/SiC interfaces, such as low inversion carrier mobility and deteriorated gate oxide reliability. This paper overviews the fundamental aspects of SiC-MOS devices and indicates intrinsic obstacles connected with an accumulation of both negative fixed charges and interface defects and with a small conduction band offset of the SiO2/SiC interface which leading to the increased gate leakage current of MOS devices. To overcome these problems, we proposed using aluminum oxynitride (AlON) insulators stacked on thin SiO2 underlayers for SiC-MOS devices. Superior flatband voltage stability of AlON/SiO2/SiC gate stacks was achieved by optimizing the thickness of the underlayer and nitrogen concentration in the high-k dielectrics. Moreover, we demonstrated reduced gate leakage current and improved current drivability of SiC-MOSFETs with AlON/SiO2 gate stacks.