US Patent 7481880 Mask and method for crystallizing amorphous silicon

A method of crystallizing amorphous silicon includes forming an amorphous silicon layer on a substrate, placing a mask over the substrate including the amorphous silicon layer, and applying a laser beam onto the amorphous silicon layer through the mask to form a first crystallized region, the laser beam having an energy intensity high enough to completely melt the amorphous silicon layer, wherein the mask comprises a base substrate, a phase shift layer on the base substrate, having a plurality of first stripes having a first width separated by slits, and a blocking layer overlapping the phase shift layer, having a plurality of second stripes having a second width narrower than the first width, the second stripes being parallel to the first stripes.