Investigation of 4H-SiC MOS capacitors annealed in diluted N2O at different temperatures

Thermally grown oxide on 4H-SiC has been post-annealed in diluted N2O (10% N2O in N2) at different temperatures from 900 to 1100 deg C. The quality of the nitrided oxide and the SiO2/4H-SiC interface was investigated by AC conductance and high frequency C-V measurements based on Al/SiO2/4H-SiC metal-insulator-semiconductor (MOS) structure. It is found that N2O annealing at 1000 deg C produces the lowest interface state density, though the difference is not so significant when compared to the other samples annealed at 900 and 1100 deg C. These results can be explained by the high temperature dynamic decomposition process of N2O. By fitting the AC conductance data, it is found that higher temperature nitridation increases the capture cross-section of the interface traps.