Improvement in Electrical Stability of a-IGZO TFTs Using Thinner Dual-Layer Dielectric Film

Abstract

This study investigates the effect of gate insulators on thin-film transistors (TFTs) using an amorphous InGaZnO4 (a-IGZO) channel layer. TFTs with single-layer Ta2O5 and dual-layer Ta2O5/SiO2 gate insulators were fabricated on a glass substrate. An evaluation of the insulating film using the MIM (Metal-Insulator-Metal) structure confirmed its electrical characteristics. Microscopic imaging showed that the dual-layer Ta2O5/SiO2 dielectric significantly improved surface characteristics. A reduction in the leakage current, better on/off ratios, and a decreased subthreshold swing (SS) compared to a single-layer Ta2O5 dielectric were reported. The dual-layer insulator composed of SiO2/Ta2O5 was highly effective in improving device characteristics.