Effects of wet N2O oxidation on interface properties of 6H-SiC MOS capacitors

Oxynitrides were grown on n- and p-type 6H-SiC by wet N2O oxidation (bubbling N2O gas through deionized water at 95degreesC) or dry N2O oxidation followed by wet N2O oxidation. Their oxide/SiC interfaces were investigated for fresh and stressed devices. It was found that both processes improve p-SiC/oxide but deteriorate n-SiC/oxide interface properties when compared to dry N2O oxidation alone. The involved mechanism could be enhanced removal of unwanted carbon compounds near the interface due to the wet ambient, and hence a reduction of donor-like interface states for the p-type devices. As for the n-type devices, incorporation of hydrogen-related species near the interface under the wet ambient increases acceptor-like interface states. In summary, the wet N2O oxidation can be used for providing comparable reliability for n- and p-SiC MOS devices, and especially obtaining high-quality oxide-SiC interface in p-type MOS devices.