Hydrogenation in laser annealed polysilicon thin-film transistors (TFTs)

Hydrogenation effects in excimer laser annealed polysilicon thin-film trans istors (TFTs) were studied. Hydrogen plasma formed from hydrogen diluted wi th Ar or He was used in order to passivate defects at the polysilicon/silic on oxide interface, as well as in the polysilicon material. It was found th at, after hydrogenation, no more than a 10% increase in the carrier mobilit y is attained, accompanied by a threshold-voltage decrease, due to passivat ion of deep states at the polysilicon/silicon oxide interface and at the gr ain boundaries. However, the most important feature of hydrogenated devices is the improvement in the dispersion of their transfer characteristics. In addition, hot-carrier stress experiments showed that optimization of the t ype of dilution gas (Ar or He) and the relative concentration of hydrogen c an be carried out in order to improve the device reliability. (C) 2001 Else vier Science B.V. All rights reserved.