Method of forming polycrystalline semiconductor layer and thin film transistor using the same

1. A method of forming a polycrystalline semiconductor layer, comprising:

forming a semiconductor layer of amorphous silicon on a substrate;

forming a plurality of spot seeds in the semiconductor layer by irradiating a first laser beam through a crystallization mask, each of the plurality of spot seeds being equally spaced from one another and each having equal area, wherein each of the plurality of spot seeds includes polycrystalline silicon; and

forming a polycrystalline silicon layer along an entire surface of the substrate by irradiating a second laser beam onto the semiconductor layer, wherein an area between adjacent spot seeds is entirely exposed to the second laser beam,

wherein the first laser beam has an energy density to completely melt the entire semiconductor layer and the second laser beam has an energy density to melt most of the semiconductor layer, wherein the energy density of the first laser beam is larger than the energy density of the second laser beam.

2. The method according to claim 1 , further comprising forming a buffer layer between the substrate and the semiconductor layer.

3. The method according to claim 1 , wherein irradiating the second laser beam is repeated more than twice.

4. The method according to claim 1 , wherein the crystallization mask includes a plurality of transmissive areas and a blocking area surrounding the plurality of transmissive areas.

5. The method according to claim 4 , wherein the plurality of transmissive areas correspond to the plurality of spot seeds.

6. The method according to claim 1 , wherein a distance between adjacent spot seeds is within a range of about 0.5 μm to about 0.5 μm.

7. The method according to claim 1 , wherein each of the spot seeds has a rectangular shape, and one side of the rectangular shape is within a range of about 0.5 μm to about 2 μm.