First Demonstration of Dual-Gated Indium Tin Oxide Transistors with Record Drive Current ~2.3 mA/μm at L ≈ 60 nm and V<sub>DS</sub> = 1 V
Sumaiya Wahid, Alwin Daus, Aravindh Kumar, H.‐S. Philip Wong, Eric Pop
Abstract
We report dual-gated indium tin oxide (ITO) transistors, with record-high drive current ~2.3 mA/$\mu \mathrm{m}$ at channel length $L \sim 60$ nm and $V_{DS} = 1\mathrm{V}$. We explore both Ni and Pd as source and drain contacts to ~3.9 nm thin sputtered ITO channels before and after capping with ~10 nm HfO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> , comparing back-gated transistor mobility, threshold voltage V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</inf> , and contact resistance R <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</inf> . V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</inf> shifts after capping are common for oxide transistors, but here we show how V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</inf> recovers by annealing at ≤300 °C in air. This enables us to achieve the first dual-gated ITO transistors with high-$\kappa$ HfO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> dielectrics, displaying high drive current, excellent on/off current ratio $\ge 10 ^{8}$ and minimum subthreshold swing, SS ~70 mV/dec. Pd contacts have several advantages, including a more positive and consistent V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</inf> with lower variability across all L, minimizing the V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</inf> shift vs. L found for Ni contacts. Pd contacts also enable good $R_{C} \approx 300 \Omega~\mu \mathrm{m}$ and effective mobility $\mu_{eff} \approx 41$ cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> $\mathrm{V}^{-1} \mathrm{s}^{-1}$. These results pave the way towards the back-end-of-line (BEOL) compatible integration of high performance, short-channel ITO transistors.