Laser mask and crystallization method using the same

1. A method for fabricating a display device comprising:

forming a plurality of gate lines and data lines on a substrate, the gate and data lines crossing each other to define pixels; and

forming a thin film transistor (TFT) near each crossing in the pixel, this step further including,

forming a semiconductor layer on the substrate;

positioning a mask over the substrate, the mask having first, second and third blocks, each block having a periodic pattern including a plurality of transmitting regions and a blocking region, the periodic pattern of the first block having a first position, the periodic pattern of the second block having a second position, the periodic pattern of the third block having a third position, the first, second and third positions being different from each other wherein when the three periodic patterns are projected in one block, the adjacent three transmitting regions form one equilateral triangle, and six of the equilateral triangles form a regular hexagon;

crystallizing the semiconductor layer by irradiating a laser beam through the mask.

2. The method according to claim 1 , wherein the transmitting regions have a shape of a circle.

3. The method according to claim 2 , wherein a distance between the centers of the transmitting regions is L, a radius of the transmitting regions having a circular shape is R, and L and R have a relationship of

L

3

≤

R

<

L

2

.

4. The method according to claim 1 , wherein the transmitting regions have a shape of a polygon, the polygon including triangle, square, hexagon and octagon.

5. The method according to claim 1 , wherein the transmitting regions in each block are arranged in an N columns×M rows matrix configuration (each of N and M is an integer).

6. The method according to claim 5 , wherein the transmitting regions in each block are arranged crisscross in odd and even rows.

7. The method according to claim 1 , wherein the mask is made of metal, the metal including chrome or aluminum.

8. The method according to claim 1 , wherein the crystallizing the semiconductor layer further includes:

irradiating a first laser beam through the mask for forming a first crystallized region, wherein a size of the first crystallized region is W;

moving the substrate by less than W;

irradiating a second laser beam through the mask for forming a second crystallized region;

moving the substrate by less than W; and

irradiating a third laser beam through the mask for forming a third crystallized region.

9. The method according to claim 8 , wherein the substrate moves by about one third of W.

10. The method according to claim 1 , wherein the crystallizing the semiconductor layer further includes:

irradiating a first laser beam through the mask for forming a first crystallized region;

moving the mask by about a distance equal to a size of one block;

irradiating a second laser beam through the mask for forming a second crystallized region;

moving the mask by about a distance equal to a size of one block; and

irradiating a third laser beam through the mask for forming a third crystallized region.

11. The method according to claim 1 , wherein the irradiated laser has an energy density of a complete melting region.

12. The method according to claim 1 , wherein the semiconductor layer is crystallized by a sequential lateral solidification (SLS) method.

13. The method according to claim 1 , wherein the display device is either a liquid crystal display or an electroluminescence display.