Patent ID: 7767558
Filing Date: 2010-08-03
Classification: C30B,H01L

Abstract:
1. A method of crystallizing amorphous silicon, comprising: forming an amorphous silicon film over a substrate; crystallizing the amorphous silicon film to form a polycrystalline silicon film using a sequential lateral solidification crystallization method, wherein the sequential lateral solidification crystallization method includes at least a first application of a first laser beam having a first energy density that completely melts a first uncrystallized portion of the amorphous silicon film and melts a first crystallized portion of the amorphous silicon film, wherein the first application of the first laser beam forms a plurality of seeds along first border regions between solid and liquid phases of the amorphous silicon film, wherein the first uncrystallized portion of the amorphous silicon film is crystallized within a second region along a direction from the first border regions toward a center portion of the first uncrystallized portion using the plurality of seeds as nucleation cites during the first application of the first laser beam, wherein the second region includes a plurality of first sub-grains having a first size and a plurality of first sub-grain boundaries, wherein the sequential lateral solidification crystallization method includes at least a second application of the first laser beam that grows the first sub-grains to form a plurality of second sub-grains having a second size greater than the first size, wherein a first group of the second sub-grains grow along a first direction to contact a second group of the second sub-grains that grow along a second direction substantially opposite to the first direction, and wherein the first and second groups of second sub-grains form a second sub-grain boundary, wherein the plurality of first sub-grain boundaries are disposed among the plurality of first sub-grains and among the plurality of second sub-grains, and wherein the plurality of first sub-grain boundaries and the second sub-grain boundary include a plurality of microscopic defect particles; and performing a surface treatment to the polycrystalline silicon film, wherein the surface treatment includes application of a second laser beam having a second energy density that has a partial melting energy density to melt defect sites in the polycrystalline silicon film, wherein the application of the second laser beam partially melts and re-crystallizes the polycrystalline silicon film and removes the plurality of microscopic defect particles to smoothen the surface of the polycrystalline silicon film.