Patent ID: 7687334

Claim:
A method for forming a polycrystalline silicon film, comprising the steps of: a) providing a substrate having a thermally-grown silicon dioxide layer adapted for preventing the crystal orientation of the substrate from affecting the crystallization of the amorphous silicon film, wherein the thermally-grown silicon dioxide layer has a thickness in a range of about 1-3 μm; b) forming an amorphous silicon film on the thermally-grown silicon dioxide layer of the substrate; c) forming an aluminum layer having a thickness in a range of about 5-100 nm on the amorphous silicon film to form a structure having the substrate, the amorphous silicon film and the aluminum layer; and d) annealing the structure at an annealing temperature effective for a period of time in a nitrogen environment with an annealing temperature ramp-up time of at least about 10 minutes to crystallize the amorphous silicon film to form a polycrystalline silicon film comprising a plurality of crystallites, wherein the average crystallite size of the plurality of crystallites increases with the annealing temperature ramp-up time.