Amorphous-InGaZnO4 Thin-Film Transistors with Damage-Free Back Channel Wet-Etch Process

Abstract

A damage-free back channel wet etch process is developed for inverted staggered amorphous-InGaZn04 (a-IGZO) thin-film transistors (TFTs). The key ingredient is a less acidic etchant such as hydrogen peroxide (H2O2)-based etchants rather than the commonly used nitric acid (HNO3)-based etchants for the back channel etch. Scanning electron microscope images and X-ray photoelectron spectroscopy (XPS) data are used to monitor the damage on the a-IGZO and the etch profiles of the source and drain electrodes. Better etch profile and fewer residues on the channel along with superior TFT performance are achieved by using a H2O2-based etchant (H2O + H2O2 + additive) compared to the conventionally used HNO3-based etchant (HNO3 + H3PO4 + CH3COOH). Highly acidic etchants induce the formation of defects such as oxygen vacancies in the a-IGZO, thereby degrading TFT performance.