STUDY ON HYDROGENATION OF POLYSILICON THIN-FILM TRANSISTORS BY ION-IMPLANTATION

Hydrogenation of polysilicon (poly-Si) thin film transistors (TFT's) b y ion implantation has been systematically studied, Poly-Si TFT perfor mance 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 b een studied as functions of ion implantation dose and FGA temperature. Under the optimized conditions (H+ dose of 5 x 10(15) cm(-2) and FGA temperature at 375 degrees C), NMOS poly-Si TFT's fabricated by a low temperature 600 degrees C process have a mobility of similar to 27 cm (2)/V . s, a threshold voltage of similar to 2 V, a subthreshold sitin g of similar to 0.9 V/decade, and an OFF-state leakage current of simi lar to 7 pA/mu m at V-DS = 10 V. The avalanche induced kink effect was found to be reduced after hydrogenation.