Improvement of Stress Stability in Back Channel Etch-Type Thin Film Transistors with Post Process Annealing

Abstract

The chemical states and electronic structures near the back channel surfaces of amorphous In-Ga-Zn-O (a-IGZO) thin films were investigated by means of x-ray photoelectron spectroscopy (XPS) and photoinduced transient spectroscopy (PITS). The XPS analysis revealed that, due to source/drain (S/D) wet-etching, sub-gap states formed continuously near the valence band, which induced the degradation of the TFT characteristics. According to the PITS analysis, an increase in the hydrogen-related traps in a-IGZO thin films was clearly observed after the S/D wet-etching. The XPS spectra suggested that an increase in OH bonds at the back channel surface resulted in an improvement of stress stabilities such as negative bias, thermal and illumination stress environment.