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 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\mathrm{V}_{\text{FB}})$</tex> hysteresis (0.03 V), illustrating that the defects near <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SiO}_{2}/\text{SiC}$</tex> interface are suppressed. The result is also compared with the sample oxidized by atmospheric oxidation under 10% <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{N}_{2}\mathrm{O}$</tex> annealing. Although <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{N}_{2}\mathrm{O}$</tex> 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 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{V}_{\text{FB}}$</tex> 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.