Fluorine Anion-Doped Ultra-Thin InGaO Transistors Overcoming Mobility-Stability Trade-off

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 ch ) down to 60 nm, achieving E-mode operation with highest I on /I off of ~1011, high I on 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 O ) donor traps and introduce metal-metal (M-M) bond acceptor traps without altering the conduction band edge (E C ). 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.