Polysilicon thin-film transistors using self-aligned cobalt and nickel silicide source and drain contacts

Polysilicon thin-film transistors (TFT's) with island thickness of 20 and 7 0 nm were fabricated with self-aligned cobalt and nickel silicide contacts to the source and drain. The silicide contacts are shown to reduce the seri es resistance, which limits the on-current of the device, thus significantl y increasing the effective mobility in the 20-nm island devices. The mobili ties of 20-nm cobalt and nickel silicided devices are similar to those with 70-nm islands, 31 versus 33 cm(2)/V-s, whereas the nonsilicided 20-nm devi ces have a mobility of only 13 cm(2)/V-s, The island thickness is shown to influence other device parameters affecting active matrix display driver ci rcuit design, such as threshold voltage, leakage current, and subthreshold swing; all these parameters are improved when the island thickness is decre ased.