The effect of annealing on amorphous indium gallium zinc oxide thin film transistors

This paper presents the post-annealing effects, caused by rapid thermal annealing (RTA), on amorphous indium gallium zinc oxide (a-IGZO) thin film transistor's (TFT) electrical characteristics, and its contact resistance (RC) with thermally grown SiO2 gate dielectric on silicon wafer substrates. The electrical characteristics of two types of TFTs, one post-annealed and the other not, are compared, and a simple model of the source and drain contacts is applied to estimate the RC by a transmission line method (TLM). Consequently, it has been found that the post-annealing does improve the TFT performances; in other words, the saturation mobility (μsat), the on/off current ratio (ION/OFF), and the drain current (ID) all increase, and the RC and the threshold voltage (VT) both decrease. As-fabricated TFTs have the following electrical characteristics; a saturation mobility (μsat) as large as 0.027 cm2/V s, ION/OFF of 103, sub-threshold swing (SS) of 0.49 V/decade, VT of 32.51 V, and RC of 969 MΩ, and the annealed TFTs have improved electrical characteristics as follows; a μsat of 3.51 cm2/V s, ION/OFF of 105, SS of 0.57 V/decade, VT of 27.2 V, and RC of 847 kΩ.