Investigation into electrochemical oxidation behavior of 4H-SiC with varying anodizing conditions

Electrochemical-assisted hybrid machining has been widely utilized for processing of single crystal SiC, which is a very promising next-generation semiconductor material for high power, high frequency and high temperature applications. With the aim of optimizing the machining process to achieve both high efficiency and high surface integrity, the electrochemical oxidation behaviors of 4H-SiC were experimentally investigated with varying the anodizing conditions from the aspects of electrolyte types, ionic concentration, potentials etc. in this study. Experimental results demonstrated that neutral solutions showed higher oxidation ability of 4H-SiC in comparison to acidic and alkaline electrolytes. 4H-SiC could be electrochemically oxidized in an extremely low concentration electrolyte, and mass concentration 1-2% could achieve highest film thickness of 197 nm and initial oxidation rate of 4.9 nm/s. The oxidation rate increased exponentially at the initial stage of anodization before reaching saturation. Meanwhile, the oxidation process exhibited significant anisotropy, with the oxidation rate of C-face 5-15 times higher that of Si-face. On the other hand, the hardness of the electrochemicallyoxidized 4H-SiC surface was reduced by more than 90%. It was also noticed that the micro morphology of oxidized surface was significantly influenced by the ion types in the electrolytes. Furthermore, the electrochemical oxidation mechanism of 4H-SiC were discussed based on the experimental findings. The OH. radical was considered the main factor determining the oxidation process of SiC. The research results deepen the understanding of the electrochemical oxidation of SiC and provide insights for optimizing the electrochemical-assisted hybrid machining process.