Fluorine Anion-Doped Ultra-Thin InGaO Transistors Overcoming Mobility-Stability Trade-off
Jianyue Zhang, Z. Zhang, Hongyi Dou, Zehao Lin, Kun Xu, Wen Yang, X. Zhang, Haiyan Wang, P. D. Ye
Abstract
In this work, we report on the first demonstration of back-end-of-line (BEOL)-compatible ultra-thin (~3 nm) fluorine-doped InGaO thin film transistors (TFTs) with 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 60 nm, achieving E-mode operation with highest 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> of ~1011, high I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</inf> of 418 μA/μm, low subthreshold swing (SS) of 85 mV/dec and remarkably high degree of thermal and bias stability among recently reported oxide TFTs. It is found that F-doping delivers better mobility-stability trade-off compared to that of Ga-doping, providing higher mobility and significantly enhanced stability performance simultaneously, which is attributed to the fact that F-doping could effectively reduce oxygen vacancy (V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">O</inf> ) donor traps and introduce metal-metal (M-M) bond acceptor traps without altering the conduction band edge (E <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</inf> ). This study for the first time shows that anion doping has more advantages than commonly studied cation doping, thus points to a new research direction of studying the critical role of anion dopants in mobility-stability trade-off in oxide semiconductor TFTs.