Correlation between electrical characteristics and Oxide/Polysilicon interface morphology for excimer-laser-annealed poly-Si TFTs

Abstract

This work investigates the correlation between electrical characteristics and gate-oxide/polysilicon interface morphology for excimer-laser-annealed (ELA) poly-Si thin-film transistors (TFTs). The main feature of ELA poly-Si films is protrusion at grain boundaries that makes the film surface appear very rough. The surface roughness increases with increasing laser energy density and causes degradation of off-current and reliability for the ELA poly-Si TFTs. This degradation of the off-current is attributed to the lower channel resistance due to the increase in crystallinity of the poly-Si layer and the enhancement of localized electric field arising from the protrusions at the grain boundaries. In addition, the increase of localized electric field also degrades device reliability. Passivation of gate oxide/poly-Si channel by NH3-plasma treatment was found to be favorable in improving the performance and reliability of the ELA poly-Si TFTs. (C) 2002 The Electrochemical Society.