Effect of Al2O3 passivation layer on the stability of aluminum-indium-zinc oxide thin film transistors

Abstract

This study investigated the effect of an Al2O3 passivation layer on the stability of radio-frequency magnetron cosputtered aluminum-indium-zinc oxide (Al-IZO) thin-film transistors (TFTs) under positive bias stress, positive bias illumination stress, negative bias illumination stress, and constant current stress. In current devices, threshold-voltage (Vth) instability is dominated by the photo-generated hole/electron trapping at a back-channel surface and/or interface between an insulator and a channel, and the deep defects (subgap states) located near the valence band can easily cause a subgap photoexcitation, resulting in a large Vth shift. In this study, experimental results show that Al2O3-passivated Al-IZO TFTs exhibit stable electrical behaviors under each stress condition (ΔVth < 1.7 V), whereas the unpassivated Al-IZO TFTs exhibit obvious shifts in threshold voltage (ΔVth < 10.50 V). In this study, the authors demonstrated that Al2O3 could be an effective passivation layer to suppress O2 absorption/desorption on the Al-IZO back-channel and decrease photo-excitation on Al-IZO films.