Improvement of 4H-SiC MOS capacitor reliability under high positive-bias stress by low-pressure oxidation

In this paper, low-pressure oxidized SiC MOS devices with high breakdown voltage and reliability are investigated. Compared with conventional gate oxidation in normal pressure, low-pressure oxidation greatly enhanced the hard breakdown voltage and the onset field of the Fowler–Nordheim current by about 1.5 MV/cm. The capacitance-voltage (C-V) characteristic of the low-pressure oxidized device had a minimal flat-band voltage (VFB) hysteresis (0.03 V), illustrating that the defects near SiO2/SiC interface are suppressed. The result is also compared with the sample oxidized by atmospheric oxidation under 10% N2O annealing. Although N2O nitridation can effectively improve the interface properties, it has caused greater instability in the positive bias instability (PBI) measurement, especially under high-stress_electric fields. However, low-pressure oxidation could significantly reduce the VFB hysteresis, even under high electric fields. This indicates that low-pressure oxidation suppresses the generation of deep-level traps at the interface, which improves the reliability of SiC MOS devices.