Effect of Atmosphere Dependent Annealing on the Electrical Characteristics of a-In₂O₃ Thin-film Transistors

In2O3 has been recognized as a wide-gap transparent semiconductor oxide with high mobility, in which the oxygen plays an important role in its electronic properties. Here, we investigate the effects of air, O-3 and N-2 annealing on the electrical characteristics of a-In2O3 thin film transistors (TFTs) by analyzing the behavior of weakly bonded oxygen (O-wb), excess oxygen (O-ex), and oxygen vacancy (V-O) in the channel layer. X-ray diffraction (XRD) result indicates an amorphous phase of In2O3 layer after annealing. The oxygen behavior and bonding information before and after annealing of the In2O3 films are investigated via X-ray photoelectron spectroscopy (XPS) measurements. The a-In2O3 TFTs with field-effect mobility of 50-60 cm(2)/Vs and enhanced reliability are achieved by optimizing channel thickness and annealing conditions in air. The large threshold voltage shifting, reduced mobility, and low ON/OFF ratio of O-3-annealed In2O3 TFT are attributed to the existence of O-ex. The hump-effect observed in N-2-annealed In2O3TFT is attributed to the creation of a parasitic channel with high V-O level above the main channel. The results reveal that O-wb can be removed by thermal treatment, and V-O can be partially filled and stabilized without introducing O-ex by annealing the as-deposited In2O3 TFTs in air at appropriate condition.