Improved reliability of a-IGZO thin-film transistor under positive gate bias stress by utilizing NH3 plasma treatment

Abstract

In this paper, the degradation mechanisms of the bottom-gate amorphous InGaZnO thin film transistors (a-IGZO TFTs) under positive gate bias stress (PBS) are investigated. The PBS-induced degradation can be attributed to the electron capture at the interface of the gate insulator and a-IGZO and the generation of oxygen interstitial defects (Oi) in a-IGZO. The oxygen interstitial defect density (NOi) can be calculated by the degradation of SS during recovery after PBS. It is found that the proportion of degradation caused by Oi increases with the increased a-IGZO thickness. By utilizing NH3 plasma treatment, the threshold voltage shift was reduced by >40 % under PBS (@VG = 5 V, t = 1000s). Further analysis shows that NH3 plasma treatment can effectively suppress the electron capture at the interface and the generation of Oi during PBS. Thus, PBS reliability of a-IGZO TFTs is improved by the proposed method.