Influence of low temperature oxidation and nitrogen passivation on the MOS interface of C-face 4H-SiC

•Wet oxidation at 950°C followed by NO anneal at 1175°C reduces the interface trap density to 4–6×1011cm−2eV−1.•The positive flat band voltage shift caused by low temperature wet oxidation can be suppressed by the following NO anneal.•The oxide breakdown fields for Al- and N-implanted C-face 4H-SiC samples are about 1.5 and 5MVcm−1, respectively.•The oxide breakdown field of dry oxidation at 950°C is the same as that of wet oxidation at 950°C. Wet and dry thermal oxidations on carbon (C)-face 4H-SiC samples were carried out at temperatures of 850°C, 900°C, 950°C, and 1000°C at different durations, followed by Ar anneals at the same temperature as the oxidations and NO anneals at 1175°C for different durations. The Fowler–Nordheim tunneling exhibits between 2 and 4MVcm−1, respectively, and then the breakdown occurs at around 6–8MVcm−1. The wet oxidation at 950°C provides the lowest interface trap density of 4–6×1011cm−2eV−1 at 0.24eV below the conduction band. Experiments also demonstrate that the oxide breakdown field for an N-implanted sample is lower than that of the non-implanted samples. However, the oxide breakdown field for an Al-implanted sample is even lower than that of the N-implanted sample, only 1.5MVcm−1, mainly due to damage caused by ion implantation.