Positive charge trapping in thin gate oxides of MOS capacitors during constant current and voltage fowler-nordheim stress

Abstract

A theoretical model is developed to understand positive charge generation in thin (22 to 33 nm) SiO2 gate oxides of n+-polycrystalline silicon gate MOS capacitors with n-Si substrate during Fowler-Nordheim (FN) injection with constant current and voltage at a low electron injection fluence (<0.01 C/cm2). The proposed model is based on tunneling electron initiated band-to-band impact ionization in SiO2 as the possible mechanism of positive charge generation. The experimental results of Fazan et al. of FN threshold voltage shift as a function of electron injection fluence, are analyzed using this model. The theoretical results obtained from the model are in good agreement with the experimental data.