Analysis of Nitrogen State on MOS Interface of 4H-SiC m-Face after Nitric Oxide Post Oxidation Annealing (NO-POA)

It is known that the interface nitrogen density of the 4H-SiC Si-face, C-face, and a-face increases as a result of the NO-POA process, that the electron mobility increases as the nitrogen density increases, and that each face has a different interface nitrogen saturation density. In contrast, the anisotropy of the nitridation characteristics of the m-face, which is regarded as a promising channel for high-performance trench MOSFETs, is not well known. To identify the nitridation status of the m-face after NO-POA, the MOS interface structures with a SiO2 formed on m-face by CVD and treated by NO-POA was investigated by SIMS, HAXPES, XPS, and XAFS. In the same way as the other faces, it was found that the nitrogen segregates on the SiO2/SiC MOS interface, that most of the nitrogen combines with Si, and that the interface nitrogen density has a unique saturation value. The nitrogen density saturation value on the m-face measured by SIMS was 9.8 × 1014 cm−2. This value is approximately 1.5 times the exposed carbon density on the top surface of the m-face. [DOI: 10.1380/ejssnt.2017.109]