10-nm Channel Length Indium-Tin-Oxide transistors with I<sub>on</sub> = 1860 μA/μm, G<sub>m</sub> = 1050 μS/μm at V<sub>ds</sub> = 1 V with BEOL Compatibility
Shengman Li, Chengru Gu, Xuefei Li, Ru Huang, Yanqing Wu
Abstract
In this paper, we successfully realized a shortest 10-nm channel length transistor based on ultrathin 3.5-nm indium tin oxide channel. Using 5-nm lanthanum-doped hafnium oxide (HfLaO) high- κ dielectric, the 10- nm channel ultrathin device architecture with wide bandgap exhibits excellent switching behavior with on/off ratio exceeding 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> and ultra-low leakage current of 40 fA/μm. Record-high on-state current of 1860 μA/μm and transconductance (g <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> ) of more than 1000 μS/μm have been achieved, benefited from a rather small contact resistance of 162 Ω·μm. R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> of the 10-nm ITO transistor was smaller than 500 Ω·μm. Adopting the MIT Virtual Source (MVS) model, we extracted the saturation injection velocity ν <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x0</sub> up to 8.8 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> cm/s and the resulting mean free path λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mfp</sub> of ITO transistor is 21.6 nm. Radio frequency transistor with 30-nm-long channel exhibited record high radio-frequency (RF) performance with small-signal current gain (f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> ) of 20 GHz and maximum oscillation frequency (f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> ) of 13 GHz. These two metrics contribute to √(f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> × f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> ) exceeding 15 GHz, confirming overwhelming superiority compared to RF transistors based on other ultrathin novel channel materials such as MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , BP and metal-oxides. Finally, we employed bootstrapped mode (BST) inverters to fabricate a 5-stage ring oscillator, and achieved the record-low propagation delay of 0.4 ns/stage among metal-oxides.