IGZO thin film transistors with Al2O3 gate insulators fabricated at different temperatures

Thin film transistors (TFTs) with bottom gate and staggered electrodes using atomic layer deposited Al2O3 as gate insulator and radio frequency sputtered In–Ga–Zn Oxide (IGZO) as channel layer are fabricated in this work. The performances of IGZO TFTs with different deposition temperature of Al2O3 are investigated and compared. The experiment results show that the Al2O3 deposition temperature play an important role in the field effect mobility, Ion/Ioff ratio, sub-threshold swing and bias stability of the devices. The TFT with a 250 °C Al2O3 gate insulator shows the best performance; specifically, field effect mobility of 6.3 cm2/Vs, threshold voltage of 5.1 V, Ion/Ioff ratio of 4×107, and sub-threshold swing of 0.56 V/dec. The 250 °C Al2O3 insulator based device also shows a substantially smaller threshold voltage shift of 1.5 V after a 10 V gate voltage is stressed for 1 h, while the value for the 200, 300 and 350 °C Al2O3 insulator based devices are 2.3, 2.6, and 1.64 V, respectively.