Effects of Heat-Treatment on the Population of Intrinsic Defects in and the Stability of an Amorphous Metal-Oxide Thin-Film Transistor

Though thin-film transistors (TFTs) based on amorphous metal-oxide semiconductors (AOS) subjected to different heat-treatments could exhibit nearly identical transfer characteristics, their instability against non-oxidizing heat-treatment and against electrical stress could differ significantly. Improved stability has been observed for TFTs subjected to heat-treatments at elevated temperatures or for extended durations. The dependence on such heat-treatments of the total population of intrinsic structural defects in the channel region of a TFT has been studied with the aid of a defect kinetics model. It is proposed that the meta-stable AOS undergoes a cumulative and stability-enhancing re-structuring during a heat-treatment process, leading to a decrease in the total population of intrinsic defects and an improvement in the stability of a TFT against thermal and bias stress.