Study on hydrogenation of polysilicon thin film transistors by ion implantation

Hydrogenation of polysilicon (poly-Si) thin film transistors (TFT's) by ion implantation has been systematically studied. Poly-Si TFT performance was dramatically improved by hydrogen ion implantation followed by a forming gas anneal (FGA). The threshold voltage, channel mobility, subthreshold swing, leakage current, and ON/OFF current ratio have been studied as functions of ion implantation dose and FGA temperature. Under the optimized conditions (H/sup +/ dose of 5/spl times/10/sup 15/ cm/sup -2/ and FGA temperature at 375/spl deg/C), NMOS poly-Si TFT's fabricated by a low temperature 600/spl deg/C process have a mobility of /spl sim/27 cm /sup 2//V/spl middot/s, a threshold voltage of /spl sim/2 V, a subthreshold swing of /spl sim/0.9 V/decade, and an OFF-state leakage current of /spl sim/7 pA//spl mu/m at V/sub DS/=10 V. The avalanche induced kink effect was found to be reduced after hydrogenation.>