An Investigation of the Different Charge Trapping Mechanisms for SiNx and SiO2 Gate Insulator in a-IGZO TFTs

We investigated the threshold voltage (V-TH) shifts of a-IGZO thin-film transistors (TFTs) in which the gate-insulator was either SiO2 or SiNx. The V-TH shift of the TFT using a SiO2 obeyed the stretched-exponential time model, and increased sharply according to temperature increase, whereas the SiNx device obeyed the logarithmic time model, and exhibited weak temperature dependence. We found that an inter-layer formed between the IGZO and the SiNx, whose existence can be the origin of poor bias stability and the different V-TH shift behavior in a-IGZO TFTs because the inter-layer accelerates the direct charge injection from the channel. (C) 2012 The Electrochemical Society. [DOI:10.1149/2.003204esl] All rights reserved.