The Effect of Hydrogen on the Device Stability of Amorphous InGaZnO Thin‐Film Transistors under Positive Bias with Various Temperature Stresses

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 V-th 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.