Search

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. [ABSTRACT FROM AUTHOR]

The effects of hydrogen incorporation in the active layer of amorphous InGaZnO (a‐IGZO) thin‐film transistors (TFTs) on device characteristics and instability under positive bias stress (PBS) and positive bias temperature stress (PBTS) are studied. To control the amount of incorporated hydrogen, rapid thermal annealing (RTA) treatment is conducted on the gate insulator layer before active layer deposition. It is confirmed that the amount of residual hydrogen in the gate insulator layer decreases with increasing RTA treatment time. Device stability is examined with RTA treatment times of 1 and 3 min under PBS. The device fabricated with a shorter RTA treatment time shows relatively better stability. This result is attributed to defect passivation by hydrogen that diffuses to the active layer from the gate insulator during the post‐annealing process. Additionally, TFT shows the negative shift of Vth under a high‐temperature PBTS condition. This result is due to the additional diffusion of residual hydrogen from the gate insulator into the active layer and hydrogen‐related deep state transition in the active layer by external thermal energy and a PBS condition. [ABSTRACT FROM AUTHOR]