Excessive Oxygen Peroxide Model-Based Analysis of Positive-Bias-Stress and Negative-Bias-Illumination-Stress Instabilities in Self-Aligned Top-Gate Coplanar In-Ga-Zn-O Thin-Film Transistors

Abstract

An excess oxygen-peroxide-based model that can simultaneously analyze the positive-bias-stress (PBS) and negative-bias-illumination-stress (NBIS) instabilities in commercial self-aligned top-gate (SA-TG) coplanar indium-gallium-zinc oxide (IGZO) thin-film transistors (TFTs) is proposed herein. Existing studies have reported that the transition of oxygen vacancy (V-O) charge states from V-O(0) to V-O(2+) is the dominant physical mechanism responsible for the negative shift of threshold voltage (V-TH) under NBIS. However, in this study, it is observed that both the PBS and the NBIS stabilities of IGZO TFTs deteriorate at a faster rate as the amount of oxygen increases within the channel layer, implying that the conventional V-O-related defect model is inappropriate in elucidating the PBS and NBIS instabilities of commercial SA-TG coplanar IGZO TFTs, where the channel layers are formed under high oxygen flow rates (OFRs) to make V-TH positive. On the basis of the full-energy range subgap density of states extracted before and after each stress from IGZO TFTs with different OFRs, it is determined that the generation and annihilation of the subgap states in the excess oxygen peroxide configuration are the dominant physical mechanisms for PBS and NBIS instabilities in commercial SA-TG coplanar IGZO TFTs, respectively.