Plasma nitridation of gate insulator on 4H-SiC

4H-SiC is an attractive wide bandgap semiconductor for power MOS devices due to its excellent physical properties and availability of SiO₂ by thermal oxidation. However, a lot of interface states at SiO₂/4H-SiC particularly near the conduction band edge are still a big problem for realization of high performance 4H-SiC MOS devices. Recently nitridation of gate SiO₂ by NO or N₂O gases at high temperatures has been reported for improvement of interface properties (Jamet et al., 2001). We have also showed improved interface properties by irradiating electrically neutral nitrogen radicals to thin SiO₂ (6nm) at 600°C (Maeyama, 2003). To enhance nitridation for thicker SiO₂, we have tried plasma nitridation, in which SiO₂ was directly exposed in RF nitrogen plasma to enhance nitrogen incorporation at the interface.