2012 年 33 巻 11 号 p. 639-644
Fundamental aspects of SiC oxidation and SiO2/SiC interfaces have been investigated to gain knowledge for improving performance and reliability of SiC-based MOS devices. High-resolution synchrotron x-ray photoelectron spectroscopy analysis revealed that a near-perfect interface dominated by Si-O bonds is formed by thermal oxidation of 4H-SiC(0001) substrates, but atomic scale roughness and imperfection causing electrical degradation of SiC-MOS devices are introduced as oxide thickness increases. We have also pointed out that the negative fixed charges originating from the interface defects modulate band offset at SiO2/SiC interface and that small conduction band offset leading toincreased gate leakage of MOS devices is an intrinsic problem, especially for the SiC(000-1) C-face substrates. On the basis of the results from the physical and electrical characterizations, this paper discusses the advantage of deposited insulating films on thin SiO2 underlayers in order to overcome these obstacles.