Method for preparing SiC MOSFET (Metal-Oxide -Semiconductor Field Effect Transistor) grid oxide layer

The invention relates to a method for preparing a SiC MOSFET (Metal-Oxide -Semiconductor Field Effect Transistor) grid oxide layer and belongs to the field of a SiC MOSFET device. The method comprises the following steps: generating a SiO2 grid oxide layer on a SiC epitaxial layer; annealing the grid oxide layer in a C12 environment at a temperature ranging from 500-1000 DEG C, preferably 700-800 DEG C; introducing mixed gas of C12 and inert gas at a preferable rate of 0.5-2 slm, wherein the annealing pressure is 100-1000mbar, and the retention time is 30-180 min. According to the method, C12 is used for annealing a SiO2 grid medium layer, so that oxygen vacancy tapped charges in the grid medium SiO2 layer can be removed, and the critical breakdown electric field and the voltage endurance capability of the SiO2 grid medium layer in the SiC MOSFET device can be improved.