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 ( R C) with thermally grown SiO 2 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 R C 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 ( μ sat), the on/off current ratio ( I ON/OFF), and the drain current ( I D) all increase, and the R C and the threshold voltage ( V T) both decrease. As-fabricated TFTs have the following electrical characteristics; a saturation mobility ( μ sat) as large as 0.027 cm 2/V s, I ON/OFF of 10 3, sub-threshold swing (SS) of 0.49 V/decade, V T of 32.51 V, and R C of 969 MΩ, and the annealed TFTs have improved electrical characteristics as follows; a μ sat of 3.51 cm 2/V s, I ON/OFF of 10 5, SS of 0.57 V/decade, V T of 27.2 V, and R C of 847 kΩ.