SiC is promising for power semiconductor devices, but SiO₂/SiC interface properties limit SiC MOSFET performance. We have reported that direct NO thermal treatment at 1100C on 4H-SiC(0001) achieves nitrogen incorporation comparable to conventional NO-POA (1250C) together with SiO₂ formation [1]. Given reports that low-temperature oxidation [2] and thinner oxide films [3] contribute to Dit reduction, this study explored NO oxynitridation at 900–1100C and evaluated the resulting interface properties.

4H-SiC(0001) substrates were subjected to oxynitridation in a 10% NO/N₂ atmosphere at 900–1100C for 60 min, and MOS capacitors were fabricated by Al deposition. Bidirectional C-V curves showed a clear depletion-to-accumulation transition even at 900C, confirming about 2-nm-thick oxide formation at this low temperature (Fig.1). N 1s XPS spectra showed nearly identical peak intensities regardless of NO oxidation temperature, indicating that nitrogen incorporation was independent of temperature in this temperature range (Fig.2). The interface state density (Dit) evaluated by the high-low method after PECVD-SiO₂ (50–60 nm) deposition was found to be smaller than that of the untreated sample (Fig.3). These results show that low-temperature NO oxynitridation improves the SiO₂/SiC interface.

1. T. Hosoi, ICSCRM 2025.
2. L.A. Lipkin and J.W. Palmour, J. Electron. Mater. 25, 909 (1996). DOI: 10.1007/BF02666657
3. R. Okuhira et al., ICSCRM 2024.