Characterization of SiO2/SiC Near-Interface Oxide Traps with Constant-Capacitance Deep-Level Transient Spectroscopy

Abstract

A quantitative analysis method was proposed for near-interface oxide traps (NITs) at the SiC-MOS interface. Based on the tunneling capture model for electrons to the traps, characteristic parameters of NITs were clearly extracted from the pulse width dependence of the constant-capacitance deep-level transient spectroscopy (CC-DLTS) signal amplitude measured under isothermal conditions. To exclude capture processes other than direct tunneling, the pulse voltage was set to the flat-band voltage. The validity of the assumed model, in which the majority of the traps are localized at the interface and not distributed through the whole depth of the oxide, was demonstrated through comparison of the experimental results for two samples with different oxide thickness. The density of NITs at the MOS interface fabricated on 4H-SiC oxidized in a N2O atmosphere slowly decreases with the energy depth. The capture cross-section at the interface has no energy dependence, and has a value of 10-19 cm2.