Comparative study of amorphous indium gallium zinc oxide thin film transistors passivated by sputtered non-stoichiometric aluminum and titanium oxide layers

The amorphous indium gallium zinc oxide thin film transistors (a-IGZO TFTs) passivated by sputtered non-stoichiometric aluminum oxide (AlOx) and titanium oxide (TiOx) layers were comparatively investigated in this letter. The devices with TiOx passivation layers exhibited better long-time storage stability compared with those passivated by AlOx films. Although both a-IGZO TFTs with AlOx and TiOx showed quite stable properties for negative bias-stress tests, the device passivated by TiOx film exhibited abnormal Vth shift during positive bias-stress tests. A novel passivation-layer structure consisting of both AlOx (~15 nm, bottom side) and TiOx film (~85 nm, top side) was proposed, which could perform better than either sing layers and might be preferred in mass production of a-IGZO TFTs.