Microwave plasma oxidation under a relatively high pressure (6 kPa) region is developed to rapidly grow a high-quality SiO2 layer on 4H-SiC, based on a thermodynamic analysis of SiC oxidation. By optimizing the plasma power, an atomically flat interface is achieved, and the interface trap density is lower than that of standard 1300 °C thermal-oxidized and 1350 °C NO-annealed samples measured by various methods under multiple temperature conditions. Moreover, the oxide breakdown field is higher than 9.3 MV/cm, which is comparable to that of a sample produced by high-temperature thermal oxidation. Particularly, the results of electron energy loss spectroscopy show that the transition layer between 4H-SiC and SiO2 is lower than 2 nm, indicating that microwave plasma oxidation can greatly suppress the formation of interface defects. The results strongly demonstrate the effectiveness of high-pressure plasma oxidation for SiC.

The microwave plasma oxidation under the relatively high pressure (6 kPa) region is introduced into the fabrication process of SiO2/4H-SiC stack. By controlling the oxidation pressure, species, and temperature, the record low density of interface traps (∼ 4 × 1010 cm−2⋅eV−1@Ec − 0.2 eV) is demonstrated on SiO2/SiC stack formed by microwave plasma oxidation. And high quality SiO2 with very flat interface (0.27-nm root-mean-square roughness) is obtained. High performance SiC metal–oxide–semiconductor field-effect transistors (MOSFETs) with peak field effect mobility of 44 cm−2 ⋅eV−1 is realized without additional treatment. These results show the potential of a high-pressure plasma oxidation step for improving the channel mobility in SiC MOSFETs.

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