Patent ID: 8450159

Claim:
A method for manufacturing a thin film transistor including a semiconductor layer made of polysilicon, the method comprising: forming a metal pattern on a substrate; forming a first insulating layer on the metal pattern; forming an amorphous silicon layer on the first insulating layer; crystallizing the amorphous silicon layer into a polysilicon layer by using a directional lateral solidification process; and patterning the polysilicon layer to form the semiconductor layer, wherein the directional lateral solidification process includes a repetitive crystallization process including: performing a first irradiation to one predetermined region of the amorphous silicon layer with a line-shaped laser beam having a predetermined length, width and energy density to completely melt amorphous silicon in the one predetermined region, thereby providing melted silicon in the one predetermined region, allowing the melted silicon in the one predetermined region of the amorphous silicon layer to cool and crystallize into polysilicon, moving the laser beam by less than half of the width of the laser beam in a first direction to another predetermined region, such that the other predetermined region includes a portion of the polysilicon crystallized in the one predetermined region, and performing a secondary irradiation to the other predetermined region to completely melt the polysilicon and amorphous silicon in the other predetermined region, thereby providing melted silicon in the other predetermined region.