High-Performance Self-Aligned Top-Gate Amorphous InGaZnO TFTs With 4 nm-Thick Atomic-Layer-Deposited AlO_x Insulator

Abstract

Electrical characteristics of self-aligned top-gate (SATG) amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) with 4 nm-thick atomic-layer-deposited (ALD) AlO_x gate insulator (GI) are investigated. It is demonstrated that the SATG a-IGZO TFTs present high-performance metrics including a near-ideal subthreshold swing (<i>SS</i>) of 60.9 mV/dec, a low off-state current below 10^&#x2212;12 A, a positive <inline-formula> <tex-math notation="LaTeX">${V}_{\text{th}}$ </tex-math></inline-formula> of 0.1 V, and a decent mobility of 14.1 cm²/<inline-formula> <tex-math notation="LaTeX">$\text{V}\,\cdot $ </tex-math></inline-formula>s. In addition, the TFTs exhibit negligible <inline-formula> <tex-math notation="LaTeX">${V}_{\text{th}}$ </tex-math></inline-formula> shifts less than 0.02 V against electrical bias stresses. Both high performance and excellent stability are thus simultaneously achieved for the ultrathin GI of amorphous oxide semiconductor (AOS) TFTs.