Stabilizing ALD Ultrathin In₂O₃ TFTs Under High Humidity Ambient by an Added IGZO Layer

Atomic-layer-deposited (ALD) ultrathin In2O3 thin-film transistors (TFTs) are highly promising for applications in state-of-the-art displays, flexible electronics, and back-end-of-line (BEOL) integration. However, these TFTs often suffer from pronounced bias-stress instability, which is further magnified under humid ambient. To address this issue, we herein propose a bilayer strategy, where an InGaZnO (IGZO) layer is directly sputtered on the ALD In2O3 channel layer to afford In2O3/IGZO TFTs. The added IGZO layer not only can prevent any direct gas adsorption on the sensitive In2O3 surface, but it also can substantially reduce the surface field strength near S/D to mitigate the risk of water electrolysis from a humid ambient. As a result, the In2O3/IGZO TFTs show one-order-of-magnitude improvement in threshold voltage (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\textit {th}}$ </tex-math></inline-formula>) shift under both PBS and NBS conditions in high-humidity ambient (85% relative humidity (RH)).