Light-assisted investigation of the role of oxygen flow during IGZO deposition on deep subgap states and their evolution under PBTI

Abstract

We study the role of oxygen flow during IGZO PVD process on the high temperature PBTI mechanisms in back-gated TFTs by combining light-assisted with electrical stress measurements. The oxygen flow is observed to affect the magnitude of the charge trapping component (positive Delta V-th) and hydrogen related progressive channel doping mechanism (negative Delta V-th) during PBTI stress. By exploiting light-induced de-trapping from IGZO deep states we show a direct correlation between deep sub-gap DOS and the oxygen flow during IGZO deposition: the larger the oxygen flow, the smaller the light response at time-zero and its increase during PBTI stress, despite a larger negative Delta V-th. We ascribe the light-response to metalmetal complexes which can be passivated by oxygen.