Enhanced electrical stability of IGZO thin-film transistors using atomic layer deposited Al₂O₃/HfO₂ dual-layer gate insulator

This study investigates the stability of positive bias temperature stress (PBTS) in bottom-gate indium-gallium-zinc-oxide (IGZO) thin-film transistors (TFTs) incorporating atomic layer deposited Al₂O₃/HfO₂ dual-layer gate insulators (GIs). By optimizing the thicknesses of the Al₂O₃ and HfO₂, hydrogen diffusion from the GI into the IGZO layer is effectively controlled and electron traps at the IGZO/GI interface are mitigated. The optimal dual-layer GI configuration for IGZO TFTs is identified as 15 nm Al₂O₃ on 5 nm HfO₂, resulting in an exceptionally low threshold voltage shift of −0.02 V under PBTS at 125 °C for 10⁴ s. Additionally, the device exhibits excellent electrical performance, with a saturation mobility of 11.61 cm²/Vs, a subthreshold swing of 114 mV/dec, and a threshold voltage of −0.23 V. These results highlight the potential of IGZO TFTs with dual-layer GIs for advanced integrated circuit applications.