Investigation of SiO2 film growth on 4H-SiC by direct thermal oxidation and postoxidation annealing techniques in HNO3 & H2O vapor at varied process durations

Abstract

This study has revealed that HNO3 and H2O vapors can be utilized as direct thermal oxidation or postoxidation annealing agents at a temperature above 1000°C; as they play a major role in simultaneous oxidation/nitridation/hydrogenation processes at the bulk oxide and SiO2/SiC interface. The varied process durations of the above-mentioned techniques contribute to the development of thicker gate oxides for high power device applications with improved electrical properties, lower interface-state density and higher breakdown voltage as compared to oxides grown through a more conventional wet (H2O vapor only) oxidation technique. The study highlights the effects of hydrogen and nitrogen species on the passivation of structural defects at the bulk oxide and the SiO2/SiC interface, which are revealed through the use of Time-of-Flight Secondary Ion Mass Spectroscopy and X-ray Photoelectron Spectroscopy. The physical properties of the substrate after oxide removal show that the surface roughness decreases as the process durations increase with longer hours of H2O and HNO3 vapor exposures on the samples, which is mainly due to the significant reduction of carbon content at the SiO2/SiC interface.