Method of deciding focal plane and method of crystallization using thereof

1. A method of deciding a focal plane for a light beam, comprising:

placing a test mask on a mask stage;

performing a crystallization test using the test mask;

checking the test result; and

deciding conditions of a best-fit focal plane from the test result.

2. The method of claim 1 , wherein in the placing step, the test mask has a plurality of slits.

3. The method of claim 2 , wherein the slits are formed each with a size in the range of 0.5 to 2 μm.

4. The method of claim 2 , wherein the slits have a round shape.

5. The method of claim 2 , wherein the slits have a doughnut shape.

6. The method of claim 2 , wherein the slits have a polygon shape.

7. The method of claim 1 , wherein in the placing step, the test mask is slidingly loaded onto the mask stage.

8. The method of claim 1 , wherein the checking the test result comprises:

recognizing the test result of a crystallized test film;

transmitting the recognized result to a computer; and

analyzing the transmitted result through an image analyzer.

9. The method of claim 8 , wherein in the recognizing step, the test result is recognized using a CCD (Charge Coupled Device) camera.

10. The method of claim 8 , wherein the test result is image-analyzed by a method of calculating an area which a crystallized region occupies from an entire area of the thin film.

11. The method of claim 8 , wherein the analyzing step determines a best-fit focal plane by determining conditions in which an area of a crystallized region of the test film is the largest.

12. The method of claim 1 , wherein the crystallization test is carried out again by moving the mask stage in an upward or downward direction when the best-fit focal plane is not decided after checking the test result.

13. The method of claim 1 , wherein in the performing step, a pulse-type laser is used for laser crystallization.

14. The method of claim 1 , wherein the deciding step decides the conditions of the best-fit focal plane to be a focal plane which satisfies a complete melting condition according to the crystallization test by the test mask.

15. The method of claim 1 , wherein the deciding step decides the conditions of the best-fit focal plane to be a focal plane which satisfies a near-complete melting condition according to the crystallization test by the test mask.

16. The method of claim 1 , wherein the deciding step decides the conditions of the best-fit focal plane to be a focal plane of a laser beam, which results in the largest crystallized area in the crystallization test.

17. A crystallization method comprising:

loading a test mask onto a mask stage;

deciding a best-fit focal plane by performing a crystallization test using the test mask, checking the test result and deciding conditions of a best-fit focal plane from the test result;

moving the mask stage to a position corresponding to the decided best-fit focal plane;

loading a mask for crystallization process onto the moved mask stage; and

performing the crystallization process using the mask for crystallization process.

18. The method of claim 17 , further comprising:

loading a substrate having a layer to be crystallized onto a moving stage after deciding the best-fit focal plane,

wherein the performing step performs the crystallization process on the layer.

19. The method of claim 17 , wherein in the performing step, the crystallization process is carried out by irradiating a laser beam on an amorphous silicon film formed on a substrate in a best-fit focal plane state.

20. The method of claim 17 , wherein in the performing step, the crystallization process is carried out using a pulse-type laser.

21. The method of claim 17 , wherein the deciding step decides the best-fit focal plane to be a focal plane which satisfies a complete melting condition according to the crystallization test by the test mask.

22. The method of claim 21 , wherein a lateral solidification process is carried out on the complete melting condition.

23. The method of claim 17 , wherein the deciding step decides the best-fit focal plane to be a focal plane which satisfies a near-complete melting condition according to the crystallization test by the test mask.

24. The method of claim 23 , wherein an excimer laser crystallization process is carried out on the near-complete melting condition.

25. The method of claim 17 , wherein the step of deciding the best-fit focal plane comprises:

analyzing the test result though an image analyzer, and

through an image analysis by the image analyzer, determining the conditions of the best-fit focal plane to be a focal plane of a laser beam resulting in the largest crystallized area.

26. The method of claim 17 , wherein the step of deciding the best-fit focal plane is carried out by equipment identical to crystallization equipment used for performing the crystallization process.

27. The method of claim 17 , wherein the step of deciding the best-fit focal plane is carried out on laser equipment and optical system conditions identical to those for performing the crystallization process.