Effect of SiO₂ and/or SiNₓ Passivation Layer on Thermal Stability of Self-Aligned Coplanar Amorphous Indium–Gallium–Zinc–Oxide Thin-Film Transistors

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 SiO2or SiNxby plasma enhanced chemical vapor deposition (PECVD). The field-effect mobility of a-IGZO TFT with SiNxis almost unchanged by extending the post-annealing time at 250 °C, but that of SiO2passivated TFT significantly degrades by increasing annealing time. It is found that the resistivity of the a-IGZO under SiNxis 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 SiNxpassivation decreases from 3.0×1011to 1.54×1011cm-2eV-1, and the stability of the a-IGZO TFT with SiNxpassivation is significantly improved by long post-annealing.