Effect of Glass Substrate on the Film Properties of Poly Silicon by Excimer Laser Annealing

Abstract

This work studies the effect of glass substrate thermal properties on the crystallization behavior and surface topography of polycrystalline silicon (poly-Si) films formed by a XeCl excimer laser annealing of amorphous silicon. Films of 60 nm hydrogenated amorphous silicon (a-Si:H) film were deposited on different glass substrates of varying thermal properties. A 500 nm SiO2 buffer layer was in between the glass and the silicon film. The silicon was crystallized by a XeCl excimer laser. The atomic force microscopy (AFM) and in-plane X-ray diffraction (IPXRD) were used to evaluate the surface topography, the surface roughness, and crystalline in-plane orientation of poly-Si, respectively. Grazing incidence X-ray diffraction (GIXRD) was employed to quantify the residual stress in poly-Si film. The film properties of poly-Si exhibit a small relationship with the glass thermal properties. The higher thermal conductivity of glass retards the poly-Si <111> texture and reduced the residual tensile stress. The higher thermal diffusivity of the glass causes a decline in the poly-Si <111> texture, the surface asymmetry and flatness. A light shield introduced between glass and buffer layer in the low-temperature polycrystalline silicon (LTPS) thin-film transistors (TFTs) structures, further weakens the impact of the glass substrate on excimer laser annealing (ELA) poly-Si properties.