Pre-deposition growth of interfacial SiO2 layer by low-oxygen-partial-pressure oxidation in the Al2O3/4H-SiC MOS structure

A novel thermal oxidation method for growing a thin SiO2 layer is proposed for improving the Al2O3/4H-SiC-based MOS structure characteristics. The method combines low oxygen partial pressure and high temperature oxidation during the SiO2 layer growth process. Compared with the conventional thermal oxidation method, the experimental results show that the proposed method can effectively reduce the density of trapped charges in the oxide and at the gate dielectric/4H-SiC epilayer interface, and improve the breakdown characteristic of the MOS structure. The interface trap density (D-it) at energy level of 0.2 eV below the conduction band edge (EC) of 4H-SiC in the sample by our proposed method is reduced to 6.6 x 10(12) cm(-2) eV(-1), which is about 4 times lower than the as deposited Al2O3/4H-SiC sample. The core reason underlying the improvement is the reduced SiO2 layer thickness and lower SiCxOy component concentration, as shown by X-ray photoelectron spectroscopy measurements.