Effects of proton beam irradiation on the physical and chemical properties of IGTO thin films with different thicknesses for thin-film transistor applications

Abstract

In this study, we investigated the effects of film thickness (tch) on the radiation damage of indium-gallium-tin oxide (IGTO) thin films and radiation tolerance of high-mobility IGTO thin-film transistors (TFTs). The radiation tolerance of the TFTs was evaluated using a 5-MeV proton beam at a fixed dose of 1013 cm−2. Using tch values of 12, 27, and 42 nm, the IGTO TFT with the 12-nm-thick channel layer exhibited the best electrical performance and radiation tolerance. The radiation tolerance significantly decreased as tch increased. To elucidate the mechanism responsible for the observed phenomena, the physical and chemical properties of the IGTO thin films with different values of tch were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and atomic force microscopy before and after the proton beam irradiation. The characterization results revealed that the decreased radiation tolerance of the thicker-channel IGTO TFTs were mainly attributed to the further enhanced oxygen vacancy generation due to the atomic displacement cascades within the IGTO channel layer after the proton irradiation. To the best of our knowledge, this is the first report studying the tch effects on the radiation hardness of oxide TFTs. The results of this study demonstrate that tch is a key parameter determining the radiation tolerance of oxide TFTs and a thin channel layer is advantageous in improving the radiation tolerance of oxide TFTs.