Indium-Gallium-Zinc-Oxide (IGZO) Nanowire Transistors

We report high-performance amorphous Indium-Gallium-Zinc-Oxide nanowire field-effect transistors (α -IGZO NW-FETs) featuring an ultrascaled nanowire width ( $W_{NW}$ ) down to ~20 nm. The device with 100 nm channel length ( $L_{CH}$ ) and ~25 nm $W_{NW}$ achieves a decent subthreshold swing (SS) of 80 mV/dec as well as high peak extrinsic transconductance ( $G_{m,ext}$ ) of 612 μ S/μ m at a drain-source voltage ( $V_{DS}$ ) = 2 V (456 μ S/μ m at $V_{DS}$ = 1 V). The good electrical properties are enabled by using an ultrascaled 5 nm high-k HfO₂ as the gate dielectric, a water-free ozone-based atomic layer deposition (ALD) process, and a novel digital etch (DE) technique developed for indium-gallium-zinc-oxide (IGZO) material. By using low-power BCl₃-based plasma treatment and isopropyl alcohol (IPA) rinse in an alternating way, the DE process is able to realize a cycle-by-cycle etch with an etching rate of ~1.5 nm/cycle. The scaling effects on device performance have been analyzed as well. It shows that the downscaling of $W_{NW}$ improves the SS notably without sacrificing on-state performance, and the shrinking of $L_{CH}$ boosts the $G_{m,ext}$ . The ultrascaled α -IGZO NW-FETs could play an important role in applications where high performance and high density are highly desired.