Enlargement of crystal grains in thin silicon films by continuous-wave laser irradiation

The cw laser recrystallization of amorphous silicon (a-Si) thin films deposited on SiO2 films with Si(100) substrates was investigated by controlling irradiation conditions. The effects of the laser spot shape and laser-irradiated region overlap were found important resulting in two dimensional crystal growth different from conventional lateral crystallization. A laser beam spot was designed to realize a gradual temperature slope in the laser-irradiated region. The crystal grain growth of the Si thin films was effectively enhanced.. Raster scanning was performed to make the crystal growth direction regular and effectively enhanced the crystallization of the recrystallized Si thin films. The laser-irradiated region overlap also effectively enhanced the crystallization of the recrystallized Si thin films. Consequently, (100) well-oriented polycrystalline Si thin films with an average grain size of 1.60 mu m, which is about 5 times larger than that obtained by conventional excimer laser recrystallization, were obtained.