Effects of wet N/sub 2/O oxidation on interface properties of 6H-SiC MOS capacitors

Oxynitrides were grown on n- and p-type 6H-SiC by wet N/sub 2/O oxidation (bubbling N/sub 2/O gas through deionized water at 95/spl deg/C) or dry N/sub 2/O oxidation followed by wet N/sub 2/O 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 N/sub 2/O 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, wet N/sub 2/O oxidation can be used for providing comparable reliability for nand p-SiC MOS devices, and especially for obtaining high-quality oxide-SiC interfaces in p-type MOS devices.