JPS6425515A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form a polycrystalline silicon layer having the large diametered crystal grain on the surface without changing the width of a pulse, by using one ultraviolet pulse laser device, and projecting ultraviolet ray pulse laser beams having different energy densities on a part of the polycrystalline silicon layer without changing a wavelength. CONSTITUTION:A polycrystalline silicon layer 2 is formed on the entire surface of a glass substrate 1 with SiH4 as a raw material. Then, SiH4 is used as a raw material, and a silicon oxide layer 3 is formed so as to cover the polycrystalline silicon layer. Thereafter, first ultraviolet ray pulse laser 4 is projected thereon, e.g., at a wavelength of 308nm and at energy density of 300mJ/cm<2>. Thus, a surface part 2' in the polycrystalline silicon layer 2 is recrystallized. Then ultraviolet ray pulse laser, which has the lower energy density than the first laser and has the same wavelength, is projected, e.g., at energy density of 150mJ/cm<2>. Of the recrystallized polycrystalline silicon layer, the surface part 2' is further recrystallized. At this time, the remaining crystal part of the layer of the surface part 2' acts as a core for crystal growing of the part of 2'. Therefore, the polycrystalline silicon film having the large diameter of a crystal grain is formed.