Nitric acid oxidation method to form SiO2/3C–SiC structure at 120 °C

Abstract 3C–SiC(0 0 1) surfaces are considerably rough with the roughness root mean square value ( R ms ) of 1.3 nm, but the surfaces become considerably smooth (i.e., R ms of 0.5 nm) by heat treatment in pure hydrogen at 400 °C. Two-step nitric acid (HNO 3 ) oxidation (i.e., immersion in ∼40 wt% HNO 3 followed by that in 68 wt% HNO 3 ) performed after the hydrogen treatment can oxidize 3C–SiC at extremely low temperature of ∼120 °C, forming thick SiO 2 (e.g., 21 nm) layers. With no hydrogen treatment, the leakage current density of the 〈Al/SiO 2 /3C–SiC〉 metal-oxide-semiconductor (MOS) diodes is high, while that for the MOS diodes with the hydrogen treatment is considerably low (e.g., ∼10 −6  A/cm 2 at the forward gate bias of 1 V) due to the formation of uniform thickness SiO 2 layers. The MOS diodes with the hydrogen treatment show capacitance–voltage curves with accumulation, depletion, and deep-depletion characteristics.