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

Abstract

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 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 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 (mu(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 (p,a) as large as 0.027 cm(2)/V s, I-ON/OFF Of 103, sub-threshold swing (SS) of 0.49 V/decade, V-T of 32.51 V, and R-C of 969 M Omega, and the annealed TFTs have improved electrical characteristics as follows; a mu(sat), of 3.51 cm(2)N 5, I-ON/OFF of 105, SS of 0.57 V/decade, V-T of 27.2 V, and R-C of 847 k Omega. (c) 2010 Elsevier B.V. All rights reserved.