Characteristics of top-gate thin-film transistors fabricated on nitrogen-implanted polysilicon films

The electrical characteristics of top-gate thin-film transistors (TFT's) fabricated on the nitrogen-implanted polysilicon of the doses ranging from 2/spl times/10/sup 12/-2/spl times/10/sup 14/ ions/cm/sup 2/ were investigated in this work. The experimental results showed that nitrogen implanted into polysilicon followed by an 850/spl deg/C 1 h annealing step had some passivation effect and this effect was much enhanced by a following H/sub 2/-plasma treatment. The threshold voltages, subthreshold swings, ON-OFF current ratios, and field effect mobilities of both n-channel and p-channel TFT's were all improved. Moreover, the hot-carrier reliability was also improved. A donor effect of the nitrogen in polysilicon was also found which affected the overall passivation effect on the p-channel TFT's.