Low-Temperature Fully Photolithographic In-Si-O Thin-Film Transistors

This paper analyses the reliability of In-Si-O (ISO) thin-film transistors (TFT) via bias-stress and photo-stress measurements. The ISO TFTs used in the measurements were developed with a fully photolithographic process, with a maximum temperature of 200 □. Typical performance of ISO TFTs included a mobility of 5.03 cm2/(V·s), a threshold voltage (Vth) of-0.16 V, and a subthreshold swing of 312 mV/dec. In this work, ISO TFTs were biased up to four hours at different temperatures and illumination. Threshold voltage shifts were observed and modeled. Threshold voltage shifted towards the negative, and off-current and subthreshold swings increased when the TFT was exposed to light with wavelengths less than 660 nm. Further investigation indicated that these phenomena were caused by persistent photo-conductivity. This could be compensated for by using a positive gate pulse to remove the light-induced shallow doubly-ionized donor states