Extremely Scaled Bottom Gate a-IGZO Transistors Using a Novel Patterning Technique Achieving Record High Gm of 479.5 μS/μm (VDS of 1 V) and fT of 18.3 GHz (VDS of 3 V)

Abstract

In this work, we report bottom-gate amorphous indium-gallium-zinc-oxide (a-IGZO) transistors with extremely scaled channel length (LCH) down to 12.3 nm enabled by a novel Al2O3/HSQ dual-layer lift-off technique. Thanks to the smallest LCH of 12.3 nm among all bottom-gate IGZO transistors, a record high peak extrinsic transconductance (Gm,ext) of 479.5 μS/μm at VDS = 1 V was realized among all IGZO-based transistors. In addition to the capability of realizing ultra-scaled feature sizes, the Al2O3/HSQ dual-layer lift-off process can achieve a reduced patterning variation as compared with that of the conventional lift-off process due to the better line edge roughness of hydrogen silsesquioxane (HSQ) electron-beam (E-beam) resist. The highest cut-off frequency (fT) of 18.3 GHz at VDS of 3 V was also achieved with a LCH of 38 nm among all a-IGZO transistors.