4H-Silicon carbide (4H-SiC) is a promising material for power and harsh environment devices owing to its superior material properties, including wide bandgap, high critical electric field, and high thermal conductivity. However, despite the advantages of 4H-SiC, its channel mobility is reduced due to the high interface defect density between SiC and the oxide film, leading to increased device switching loss. Therefore, it is necessary to develop new fabrication methods to improve the quality of the SiO2/4H-SiC interface. According to recent research, the effect of high-temperature (1,250~1,300℃) nitric oxide (NO) annealing on the interface states of SiO2/4H-SiC and the channel mobility of 4H-SiC metal-oxide-semiconductor-field-effect transistors (MOSFETs) were investigated. Previous studies have optimized the NO post-oxidation annealing (POA) process, using N2 diluted NO at 1,300℃ to reduce the high SiO2/4H-SiC interface trap density (Dit). This paper focuses on high-temperature (1,250℃) 10% NO annealing to reduce interface defects by integrating nitrogen atoms into the oxide layer near the SiC interface, potentially increasing the channel mobility. Electrical properties such as Dit, threshold voltage (Vth), field-effect mobility (μFE), and specific on-resistance (Ron,sp) were assessed through capacitance-voltage (C-V) and current-voltage (I-V) measurements. It has been confirmed that the interface defect density of the gate oxide film was effectively improved under the POA conditions of 10% NO for 1 hour at 1,250℃.
