Effect of magnesium oxide passivation on the performance of amorphous indium–gallium–zinc-oxide thin film transistors

Effect of hygroscopic magnesium oxide (MgO) passivation layer on the stability of amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) under positive bias stress and positive bias temperature stress has been investigated. The effect of MgO passivation has been observed by comparing the shift of the positive threshold voltage (Vth) after constant bias temperature stress, which were 8.2 V for the unpassivated TFTs and 1.88 V for the passivated TFTs.In addition, MgO passivated a-IGZO TFTs show also excellent stability under a humidity test since MgO passivation layer can prevent the penetration of water into back channel. In order to investigate the origin of humidity test result, we have measured X-ray photoelectron spectroscopy depth profile of both unpassivated and MgO passivated TFTs with a-IGZO back channel layers after N2 wet annealing.