Effect of excimer laser annealing on the structural and electrical properties of polycrystalline silicon thin-film transistors

Abstract

The structural and electrical properties of excimer laser annealed polycrystalline silicon thin-film transistors (polysilicon TFTs) are investigated in relation to the laser energy density. The devices were fabricated on 50 nm thick polysilicon films prepared by excimer laser crystallization (ELA) of amorphous silicon or by a combined solid phase crystallization (SPC) and ELA process. The structural properties of the polysilicon films have been investigated by transmission electron microscopy analysis. The effective density of states distributions in the polysilicon films and in the oxide traps near the oxide/polysilicon interface have been determined from low frequency noise measurements. The TFT performance parameters are compared with respect to their correlation with the structural properties of the polysilicon films and their electrically active defects, the basic variables being the starting material (amorphous silicon or SPC polysilicon) and the laser energy density.