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)

In this work, we report bottom-gate amorphous indium-gallium-zinc-oxide (a-IGZO) transistors with extremely scaled channel length (L <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CH</inf> ) down to 12.3 nm enabled by a novel Al <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> /HSQ dual-layer lift-off technique. Thanks to the smallest L <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CH</inf> of 12.3 nm among all bottom-gate IGZO transistors, a record high peak extrinsic transconductance (G <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m,ext</inf> ) of 479.5 μS/μm at V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DS</inf> = 1 V was realized among all IGZO-based transistors. In addition to the capability of realizing ultra-scaled feature sizes, the Al <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> /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 (f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</inf> ) of 18.3 GHz at V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DS</inf> of 3 V was also achieved with a L <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CH</inf> of 38 nm among all a-IGZO transistors.