Top-Gate Short Channel Amorphous Indium-Gallium-Zinc-Oxide Thin Film Transistors with Sub-1.2 nm Equivalent Oxide Thickness

Abstract

We report high performance top-gate amorphous Indium-Gallium-Zinc-Oxide thin film transistors ( ${\alpha }$ -IGZO TFTs) featuring the ultra-scaled equivalent oxide thickness (EOT) of sub-1.2 nm, achieving a decent peak transconductance ( ${\text{G}}_{m}$ ) of 62 $\mu \text{S}/\mu \text{m}$ at a drain to source voltage ( $\text{V}_{DS}$ ) of 2 V (33.4 $\mu \text{S}/\mu \text{m}$ at $\text{V}_{DS}$ of 1 V) and an excellent drain induced barrier lowering (DIBL) of 17.6 mV/V, for a device with a channel length ( $\text{L}_{CH}$ ) of 160 nm. The best long channel device has a subthreshold swing (SS) of 67.5 mV/decade. This is enabled by using an aggressively scaled 5 nm high-k HfO2 as the gate dielectric. In addition, temperature study has been performed on ${\alpha }$ -IGZO TFTs. The key performance figure-of-merits, like field effect mobility ( $\mu{eff}$ ), show negligible degradation at high temperature, indicating the great potential of ${\alpha }$ -IGZO TFTs for various emerging applications.