Effects of hydrogenation on the performance and stability of p-channel polycrystalline silicon thin-film transistors

Abstract

The effects of hydrogenation on the performance and stability under electrical stress of p-channel polycrystalline silicon thin-film transistors (polysilicon TFTs) are investigated. The hydrogenation is performed in pure H 2 plasma or in plasma of 4% H 2 diluted in He gas. Devices hydrogenated in plasma of H 2/He exhibit lower subthreshold swing with better uniformity and lower leakage current, which indicate passivation of mid-gap trap states arising from dangling bonds at the grain boundaries. Hot-carrier experiments demonstrate that the stability of p-channel TFTs is improved as the hydrogenation becomes more efficient due to the effective removal of donor-type trap states at the grain boundaries.