Role of oxygen in surface kinetics of SiO2 growth on single crystal SiC at elevated temperatures

Abstract

Understanding surface kinetics of SiO2 growth on single crystal SiC at elevated temperatures is crucial to fabricate high-performance SiC-based devices. However, the role of oxygen in the evolution mechanism of SiC surface at atomic scale has not been comprehensively elaborated. Here, we reveal the manipulation effect of oxygen on the competitive growth of thermal oxidation SiO2 (TO-SiO2) and thermal chemical vapor deposition SiO2 (TCVD-SiO2) on the 4H-SiC substrate at 1500 °C. TO-SiO2 is formed by the thermal oxidation of SiC, in which the substrate undergoes layer-by-layer oxidation, resulting in an atomically flat SiC/TO-SiO2 interface. TCVD-SiO2 growth includes the sublimation of Si atoms, the reaction between sublimated Si atoms and reactive oxygen, and the adsorption of gaseous SixOy species. A relatively high sublimation rate of Si atoms at SiC atomic steps causes the transverse evolution of the nucleation sites, leading to the formation of nonuniform micron-sized pits at the SiC/TCVD-SiO2 interface. The low oxygen concentration favors TCVD-SiO2 growth, whose crystal quality is much better than that of TO-SiO2 due to the high surface mobility in the thermal CVD process. We further achieve the epitaxial growth of graphene on 4H-SiC in an almost oxygen-free reaction atmosphere. Additionally, ReaxFF reactive molecular dynamic simulation results illustrate that the decrease in oxygen concentration can promote the growth kinetics of SiO2 on single crystal SiC from being dominated by thermal oxidation to being dominated by thermal CVD.