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

Polysilicon thin-film transistors (TFTs) with island thickness of 20 and 70 nm were fabricated with self-aligned cobalt and nickel silicide contacts to the source and drain. The silicide contacts are shown to reduce the series resistance, which limits the on-current of the device, thus significantly increasing the effective mobility in the 20-nm island devices. The mobilities of 20-nm cobalt and nickel silicided devices are similar to those with 70-nm islands, 31 versus 33 cm/sup 2//V-s, whereas the nonsilicided 20-nm devices have a mobility of only 13 cm/sup 2//V-s. The island thickness is shown to influence other device parameters affecting active matrix display driver circuit design, such as threshold voltage, leakage current, and subthreshold swing; all these parameters are improved when the island thickness is decreased.