A Study on the Fabrication of a Multigate/Multichannel Polysilicon Thin Film Transistor

In this study, the new polysilicon thin film transistors (TFTs) incorporating a multigate and a multichannel were fabricated and their electrical characteristics were estimated. An average field-effect mobility as high as 30 cm2/Vs was achieved for multigate/multichannel polysilicon TFTs. A subthreshold slope of 3 V/dec and a threshold voltage of 3 V were obtained. The switching ratio was about 105. Through the experimental results, it was found that multigate/multichannel TFTs can overcome the limitation of the multigate TFT whose on-current is smaller than that of a single-gate TFT with the same aspect ratio. Moreover, the bias-dependence of their off-current was not apparent even when the multichannel structure was employed. This is thought to be caused by the increase of the total channel resistance by the division of the channel. Compared with that of the conventional TFT employing the large gate width, the off-current flow in the new multigate/multichannel polysilicon TFT was greatly reduced without much loss of the on-current, in spite of the small total gate width.