Negative bias illumination stress stability of dual-active layer amorphous indium-gallium-zinc-oxide thin-film transistor

In the current study, dual‐active layer amorphous indium‐gallium‐zinc‐oxide (a‐IGZO) TFT has been fabricated by sequential deposition of oxygen‐rich layer on a top of oxygen‐poor layer in the active layer through oxygen partial pressure control in order to improve reliability under negative bias illumination stress (NBIS) condition. The method is very simple as it is performed in situ without any post treatment. Reliability of a TFT that had a thickness of oxygen‐poor layer and oxygen‐rich active layer in the ratio of 6:4, quite improved with the threshold voltage shift Δ of a‐IGZO TFT at around 3.2 V under NBIS condition of 1000 s in comparison with a TFT (8.5 V) that comprised only oxygen‐poor active layer. The increased reliability is attributed to decrease interaction with ambient and the reduction in the total neutral oxygen vacancy concentration due to the oxygen rich layer at the back‐channel region, which was confirmed by X‐ray photoelectron spectroscopy (XPS) analysis.