Effect of ${\hbox{SiO}}_{2}$ and/or ${\hbox{SiN}}_{x}$ Passivation Layer on Thermal Stability of Self-Aligned Coplanar Amorphous Indium–Gallium–Zinc–Oxide Thin-Film Transistors

Abstract

We report the post-annealing effect on the performance of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) with self-aligned coplanar structure. The a-IZGO layer was passivated with SiO2 or SiNx by plasma enhanced chemical vapor deposition (PECVD). The field-effect mobility of a-IGZO TFT with SiNx is almost unchanged by extending the post-annealing time at 250 °C, but that of SiO2 passivated TFT significantly degrades by increasing annealing time. It is found that the resistivity of the a-IGZO under SiNx is low enough and thus can be good conduction path, leading to the high performance TFT. It is also found that the interface trap density (Nit) between a-IGZO TFT with SiNx passivation decreases from 3.0×1011 to 1.54×1011 cm-2 eV-1, and the stability of the a-IGZO TFT with SiNx passivation is significantly improved by long post-annealing.