Formation of atomically smooth SiO 2/SiC interfaces at ∼120 °C by use of nitric acid oxidation method

Abstract

Conventional thermal oxidation of SiC requires heating at ∼1100 °C. In the present study, we have developed a method of oxidizing SiC at low temperatures (i.e., ∼120 °C) to form relatively thick silicon dioxide (SiO 2) layers by use of nitric acid. When 4H-SiC(0 0 0 1) wafers are immersed in 40 wt% HNO 3 at the boiling temperature of 108 °C and the boiling is kept for 5 h after reaching the azeotropic point (i.e., 68 wt% HNO 3 at 121 °C), 8.1 nm thick SiO 2 layers are formed on the SiC substrates. High resolution transmission electron microscopy measurements show that the SiO 2/SiC interface is atomically flat and the SiO 2 layer is uniform without bunching. When SiC is immersed in an azeotropic mixture of HNO 3 with water from the first, the SiO 2 thickness is less than 0.3 nm. The metal–oxide–semiconductor (MOS) diodes with the SiO 2 layer formed by the nitric acid oxidation method possess a considerably low leakage current density.