Theoretical and Empirical Insight into Dopant, Mobility and Defect States in W Doped Amorphous In<sub>2</sub> O<sub>3</sub> for High-Performance Enhancement Mode BEOL Transistors
Yaoqiao Hu, Huacheng Ye, Khandker Akif Aabrar, Sharadindu Gopal Kirtania, Wriddhi Chakraborty, Suman Datta, Kyeongjae Cho
Abstract
Tungsten (W) doped amorphous In <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> (IWO) enable BEOL-compatible enhancement mode (E-mode) nFETs with record performance such as I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</inf> ~500μA/μm, I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</inf> /I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OFF</inf> ratio~10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9</sup> and ideal SS ~60mV/dec. The critical role of tungsten (W) doping in amorphous In <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> (a-In <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> ) for IWO FET is explored and revealed here for the first time using first-principles simulation and experimentation. We show that 1% W is the optimal doping for controlling carrier concentration and achieving the highest mobility for high-performance E-mode IWO FETs. Higher W-O bond dissociation energy suppresses oxygen vacancy (V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">O</inf> ), leading to improved thermal and threshold voltage (V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</inf> ) stability. A defect gap states model is proposed and their influence on FET operation is investigated. This work provides guidance on mitigation of defects and further improvement in FET performance and V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</inf> stability.