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

A damage-free back channel wet etch process is developed for inverted staggered amorphous-InGaZn0 4 (a-IGZO) thin-film transistors (TFTs). The key ingredient is a less acidic etchant such as hydrogen peroxide (H 2 O 2 )-based etchants rather than the commonly used nitric acid (HNO 3 )-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 H 2 O 2 -based etchant (H 2 O + H 2 O 2 + additive) compared to the conventionally used HNO 3 -based etchant (HNO 3 + H 3 PO 4 + CH 3 COOH). Highly acidic etchants induce the formation of defects such as oxygen vacancies in the a-IGZO, thereby degrading TFT performance.