Mask for laser crystallization and crystallization method using the same

1. A mask comprising:

a transmissive portion defining a crystallization pattern and an alignment pattern, the alignment pattern including a first pattern group having substantially the same size as the crystallization pattern and a second pattern group having a plurality of sub-patterns surrounding the first pattern group; and

a shielding portion surrounding the transmissive portion.

2. The mask according to claim 1 , wherein each sub-pattern comprises a radial bar.

3. The mask according to claim 2 , wherein each radial bar includes a single slit.

4. The mask according to claim 2 , wherein each radial bar includes a plurality of sub-bars spaced apart from each other.

5. The mask according to claim 4 , wherein the plurality of sub-bars are aligned along a line.

6. The mask according to claim 4 , wherein the plurality of sub-bars are aligned along a plurality of lines.

7. The mask according to claim 6 , wherein the sub-bars in one line overlap the sub-bars in another line.

8. The mask according to claim 7 , wherein a distance between the adjacent sub-bars in the one line is longer than an overlap distance between the sub-bars in the one line and the sub-bars in the other line.

9. The mask according to claim 1 , wherein the crystallization pattern includes at least one sub-crystallization pattern.

10. The mask according to claim 9 , wherein the at least one sub-crystallization pattern comprises a plurality of different sub-crystallization patterns.

11. The mask according to claim 1 , wherein the crystallization pattern includes a plurality of slits spaced apart from each other.

12. The mask according to claim 1 , wherein each sub-pattern consists of a radial bar.

13. A method comprising:

providing a mask that includes a transmissive portion and a shielding portion surrounding the transmissive portion, the transmissive portion defining a crystallization pattern and an alignment pattern, the alignment pattern including a first pattern group having substantially the same size as the crystallization pattern and a second pattern group having a plurality of sub-patterns surrounding the first pattern group;

irradiating an amorphous silicon layer using a first laser beam that passes through the alignment pattern, the irradiated amorphous silicon forming a polycrystalline silicon pattern;

aligning the first laser beam with the mask by measuring symmetry of the polycrystalline silicon pattern; and

irradiating the amorphous silicon layer using a second laser beam that passes through the crystallization pattern.

14. The method according to claim 13 , wherein each sub-pattern comprises a radial bar.

15. The method according to claim 13 , wherein aligning the first laser beam includes aligning a center of the first laser beam with a center of the alignment pattern.

16. The method according to claim 13 , wherein aligning the first laser beam comprises:

measuring the polycrystalline silicon pattern; and

moving one of the first laser beam and the mask.

17. The method according to claim 14 , wherein each radial bar includes a plurality of sub-bars spaced apart from each other and the polycrystalline silicon pattern includes a plurality of sub-polycrystalline silicon patterns corresponding to the plurality of sub-bars.

18. The method according to claim 17 , wherein aligning the first laser beam includes counting a number of the sub-polycrystalline silicon patterns.

19. The method according to claim 18 , wherein the number of the sub-polycrystalline silicon patterns is counted by using one of image sensing means, an optical microscope and a scanning electron microscope.

20. The method according to claim 19 , wherein the image sensing means is a charge-coupled device.

21. The method according to claim 13 , wherein the second laser beam has an energy density corresponding to a complete melting regime for the amorphous silicon layer and the amorphous silicon layer is crystallized by sequential lateral solidification.

22. A mask comprising:

a transmissive portion defining a crystallization pattern and an alignment pattern, the alignment pattern including a first pattern group and a second pattern group disposed around the first pattern group such that the second pattern group is substantially symmetrical around a line passing through a center of the second pattern group; and

a shielding portion surrounding the transmissive portion.

23. The mask according to claim 22 , wherein the first pattern group is substantially the same size as the crystallization pattern.

24. The mask according to claim 22 , wherein the second pattern group contains a plurality of radial bars.

25. The mask according to claim 22 , wherein the second pattern group contains a plurality of sub-patterns that extend substantially radially from a center of the first pattern group.

26. The mask according to claim 25 , wherein at least one of the sub-patterns contains multiple elements radially separated from each other.

27. The mask according to claim 26 , wherein the elements of one of the sub-patterns overlap with the elements of another of the sub-patterns.

28. The mask according to claim 27 , wherein the overlapping elements of the sub-patterns overlap in a non-radial direction.

29. The mask according to claim 28 , wherein an amount of overlap between the overlapping elements in adjacent sub-patterns is less than a distance between adjacent elements in one of sub-patterns of the adjacent sub-patterns.

30. The mask according to claim 22 , wherein the first pattern group is substantially symmetrical along a line passing through a center of the first pattern group.

31. The mask according to claim 22 , wherein the first and second pattern groups have the same center.

32. The mask according to claim 22 , wherein the first pattern group contains a plurality of sub-patterns.

33. The mask according to claim 32 , wherein the sub-patterns comprise a ring having substantially the same size as the crystallization pattern and elements disposed within the ring.

34. The mask according to claim 33 , wherein the elements are disposed substantially uniformly inside the ring.

35. The mask according to claim 22 , wherein the crystallization pattern includes a plurality of sub-crystallization patterns.

36. The mask according to claim 35 , wherein the sub-crystallization patterns are different.