Oxygen atom ordering on SiO₂/4H-SiC {0001} polar interfaces formed by wet oxidation

In the processing of 4H-SiC MOSFET devices, it is crucial to optimize the condition of wet oxidation based on the wafer surface orientation to obtain excellent electronic properties. However, the mechanism of surface oxidation and the effect of surface polarity remain unclear. The atomic structures of SiO₂/4H-SiC (0001) [Si-face] and (0001¯) [C-face] interfaces can be analyzed by aberration-corrected STEM and first-principles MD calculations. On the Si-face, interfacial O atoms on the amorphous SiO₂ layer show clear atomic ordering with a rigid O-Si bridge structure across the SiO₂/4H-SiC interface, involving a slow oxidation rate. The C-face can be rapidly oxidized, resulting in dangling bonds, bond bending, rough interface, and residual carbon in the SiO₂. A key feature is the formation of a stable and flat oxidation front by O atom ordering and then the suppression of interface defects or residual C, which provides an approach for designing high-performance 4H-SiC MOSFET devices.