Excimer Laser Crystallization of Amorphous Silicon Film with Artificially Designed Spatial Intensity Profile Beam

Abstract

A new method to form polycrystalline silicon film with large grains at the controlled location by using a single irradiation of excimer laser beam is proposed for polycrystalline silicon thin film transistor. The excimer laser beam is modified to have a spatial intensity profile -periodic spatial variation of intensity maxima (I Max ) and minima (I Min ) -by the specially designed mask composed of the opaque and the transparent patterns where the opaque pattern size is less than the optical resolution of projection lens. Based on the melt depth of amorphous silicon at the location of I Min , one can obtain three different regimes, namely, the partial melting, the near-complete melting, and the complete melting. Polycrystalline silicon grains grow vertically and laterally from the seeds at the location of I Min to the complete molten region of I Max . The evolution of polycrystalline silicon microstructure is investigated and elucidated in each regime.