Annealing influence on stoichiometry and band alignment of 4H-SiC/SiO₂ interface evaluated by x-ray photoelectron spectroscopy

Abstract Post oxidation annealing (POA) is a crucial technique for enhancing the performance of SiC metal-oxide-semiconductor field effect transistors (MOSFETs). This study investigates the impact of nitrogen-based POA on the 4H–SiC/SiO 2 interface, utilizing x-ray photoelectron spectroscopy to assess changes in stoichiometry and band alignment. We discovered that high-temperature nitrogen POA significantly refines the interface quality, shifting the SiO x C y binding energy from 101.3 eV (at 400 °C) to 102.1 eV (at 1150 °C) and reducing the C:Si ratio from 1.120 (at 400 °C) to 0.972 (at 1150 °C), indicating reoxidation and transition from C-rich interface to Si-rich interface. Despite improvements, the conduction band offset at the interface, decreases from 2.59 eV to 1.62 eV with increasing annealing temperature, suggesting a higher likelihood of electron tunneling. This finding underscores the necessity of evaluating band offsets introduced by POA to ensure the reliability of SiC MOSFETs. Additionally, excessive Ar ion etching introduces residual Ar and surface charges, causing band bending and an increased density of states in the valence band of the 4H–SiC substrate.