Effect of Double-Layered Al[sub 2]O[sub 3] Gate Insulator on the Bias Stability of ZnO Thin Film Transistors

To improve the bias stress stability of ZnO thin film transistors (TFTs), a double-layered gate insulator (GI) prepared by atomic layer deposition was proposed for forming high quality interface and suppressing interdiffusion. The protection layer deposited using water vapor, which also acts as a first GI, plays an important role in improving the bias stability. We obtained excellent characteristics of the ZnO TFT, in which the threshold voltage of 0.65 V and the mobility of did not show any changes at the stress field of 1.7 MV/cm even after 51,000 s.