Microwave plasma oxidation kinetics of SiC based on fast oxygen exchange

Abstract

Gate oxide process is one of the most important issues for making high performance SiC power MOSFETs. Previously, it has been demonstrated that plasma oxidation provides a promising way for making advanced SiC power MOSFETs. To further boost the performance of SiC MOSFETs, understanding the plasma oxidation kinetics becomes inevitable. In this contribution, microwave plasma oxidation kinetics of SiC are investigated by labelling the SiO2 with 18O isotopes. Growth of SiO2 chemically comparable to that from 1300 °C thermal oxidation with flat interface is confirmed by XPS and TEM. Moreover, SiO2 with thickness over 50 nm is demonstrated to be obtainable with rapid growth rate (>2 nm/min) at relatively low temperatures (<1000 °C) by properly adjusting the power and pressure. During the plasma oxidation, fast oxygen exchange is proved by experiments, which is significantly different from the oxidation mechanism of thermal oxidation. Furthermore, several possible reasons, such as thermal effect, water vapor oxidation and atomic oxygen diffusion for the fast oxygen exchange are discussed and eliminated, while the presence of defects in SiO2 or SiO2 structural changes are left as possible reasons for the fast oxygen exchange.