Upside-Down Annealing of Oxide Thin-Film Transistors and its Analysis Using Hydrogen-Diffusion Model

Hydrogen plays a crucial role in controlling the electrical characteristics of oxide thin-film transistors (TFTs). The conductivity of the semiconductor can be modulated by controlling the amount of hydrogen in the active layer. In this study, a thermal annealing of the sample in an inverted orientation (referred to as "upside-down annealing") is introduced. The impact of this approach on the hydrogen content within the In2O3 active layer is examined through the lens of a hydrogen diffusion model. By time-of-flight secondary ion mass spectrometry analysis, a hydrogen diffusion model for the TFT is established, and it is demonstrated that upside-down annealing is an effective method for preventing hydrogen depletion caused by out-diffusion. A bottom-gate bottom-contact TFT is fabricated to analyze electrical characteristics. By employing different post-thermal annealing methods on the device, it is discovered that the upside-down annealing enhances the device's performance significantly up to mobility of 22.3 cm2 V-1 s-1, which surpasses more than twice the mobility achieved with the traditionally oriented, "straight" annealed TFT. In this study, a thermal annealing method of oxide thin-film transistors in an inverted orientation, called "upside-down annealing," is introduced. Upside-down annealing prevents hydrogen out-diffusion from the In2O3 active layer and enhances mobility. The hydrogen content in the In2O3 active layer is examined through the lens of a hydrogen-diffusion model.image (c) 2024 WILEY-VCH GmbH