Laser-irradiated thin films having variable thickness

• US 20050059223A1
• Filed: 01/09/2004
• Published: 03/17/2005
• Est. Priority Date: 09/16/2003
• Status: Active Grant

• Current Assignee: Trustees Of Columbia University In The City Of New York (Columbia University)
• Original Assignee: Trustees Of Columbia University In The City Of New York (Columbia University)
• Inventors: Im, James
• Granted Patent: US 7,164,152 B2
• Time in Patent Office: Days
• US Class Current: 438/487
• CPC Class Codes: C30B 1/00 Single-crystal growth directly from the solid state unidirectional demixing of eutectoid materials C30B3/00; under a protective fluid C30B27/00
• CPC Class Codes: H01L 21/02532 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/02678 Beam shaping, e.g. using a mask
• CPC Class Codes: H01L 21/02683 Continuous wave laser beam
• CPC Class Codes: H01L 21/02686 Pulsed laser beam
• CPC Class Codes: H01L 21/268 using electromagnetic radiation, e.g. laser radiation
• CPC Class Codes: H01L 21/84 the substrate being other than a semiconductor body, e.g. being an insulating body
• CPC Class Codes: H01L 29/04 characterised by their crystalline structure, e.g. polycrystalline, cubic or particular orientation of crystalline planes characterised by physical imperfections H01L29/30

Abstract

A crystalline film includes a first crystalline region having a first film thickness and a first crystalline grain structure; and a second crystalline region having a second film thickness and a second crystalline grain structure. The first film thickness is greater than the second film thickness and the first and second film thicknesses are selected to provide a crystalline region having the degree and orientation of crystallization that is desired for a device component.

Claims

1. A method for processing a film, comprising:

(a) generating a first laser beam pattern from a pulsed laser beam, the first laser beam pattern having an intensity that is sufficient to at least partially melt at least a portion of a first region of a film to be crystallized;

(b) generating a second laser beam pattern from a pulsed laser beam, the second laser beam pattern having an intensity that is sufficient to at least partially melt at least a portion of a second region of the film to be crystallized, wherein the first region of the film comprises a first thickness and the second region of the film comprises a second thickness, and the first and second thicknesses are different;

(c) irradiating the first region of the film with the first laser beam pattern to form a first crystalline region having a first grain structure; and

(d) irradiating the second region of the film with the second laser beam pattern to form a second crystalline region having a second grain structure.

2. The method of claim 1, wherein the film comprises a semiconductor material.

3. The method of claim 1, wherein the film comprises a metal.

4. The method of claim 1, wherein the first and second laser beam patterns are generated using a single laser beam source.

5. The method of claim 1, wherein the first and second laser beam patterns are generated using a plurality of laser beam sources.

6. The method of claim 1, wherein the first laser beam pattern comprises a set of patterned beamlets.

7. The method of claim 1, wherein the second laser beam pattern comprises a set of patterned beamlets.

8. The method of claim 1, wherein the steps of irradiating of the first and second regions of the film occur substantially at the same time.

9. The method of claim 1, wherein the steps of irradiating of the first and second regions of the film occur sequentially.

10. The method of claim 1, further comprising:

after step (c), repositioning the first laser beam pattern on the film to illuminate a second portion of the first region of the film, and irradiating the first region of the film as in step (c), said steps of repositioning and irradiating occurring at least once; and

after step (d), repositioning the second laser beam pattern on the film to illuminate a second portion of the second region of the film, and irradiating the second region of the film as in step (d), said steps of repositioning and irradiating occurring at least once.

11. The method of claim 10, wherein repositioning occurs by movement of the mask, the film, or both.

12. The method of claim 10, wherein the repositioned laser beams irradiate a portion of the film that overlaps with a previously irradiated portion of the film.

13. The method of claim 12, wherein the repositioned laser beams are a distance less than the lateral crystal growth of the crystallized material from a previously positioned laser beam.

14. The method of claim 1, wherein the laser irradiation of the first and second regions comprises a sequential lateral solidification process (SLS).

15. The method of claim 1, wherein the first region film thickness is greater than the second region film thickness.

16. The method of claim 1, wherein the first laser beam pattern is generated using a laser beam shaped according to a first mask and a first set of laser features, and wherein the second laser beam pattern is generated using a laser beam shaped according to a second mask and second set of laser features.

17. The method of claim 16, wherein a single laser beam source is used and the laser beam is directed through the first set of laser optics to irradiate the first film region, and the second set of laser optics to irradiate the second film region.

18. The method of claim 16, wherein a plurality of laser beam sources are used and a laser beam from a first laser beam source is directed through the first set of laser optics to irradiate the first film region, and a laser beam from a second laser beam source is directed through the second set of laser optics to irradiate the second film region.

19. The method of claim 16, wherein the masks for the first and second laser beam patterns are different.

20. The method of claim 16, wherein the intensities of the shaped laser beams of the first and second laser beam patterns are different.

21. The method of claim 4, wherein the laser beam source is selected from the group consisting of continuous wave laser, solid state laser and excimer laser.

22. The method of claim 5, wherein the laser beam source is selected from the group consisting of continuous wave laser, solid state laser and excimer laser.

23. The method of claim 1, wherein conditions for irradiation of the first and second regions of the film are selected from those suitable for sequential laser solidification, excimer laser anneal and uniform grain structure crystallization.

24. The method of claim 23, wherein the first irradiation conditions are suitable for sequential laser solidification and the second irradiation conditions are suitable for uniform grain structure crystallization.

25. A film on a substrate, comprising:

a first crystalline region having a first film thickness and a first crystalline grain structure; and

a second crystalline region having a second film thickness and a second crystalline grain structure, wherein the first film thickness is greater than the second film thickness and the first and second film thicknesses are selected to provide crystalline regions having a selected degree and orientation of crystallization, and wherein the first region possesses fewer grain boundaries or other defects per unit area than the second region.

26. The film of claim 25, wherein the first and/or second crystalline region comprises a component of an electronic device.

27. The film of claim 25, wherein said device component is an active channel for a diode or thin film transistor.

28. The crystalline film of claim 25, wherein the mobility of the first polycrystalline region of the film is greater than the mobility of the second crystalline region of the film.

29. The crystalline film of claim 25, wherein the first crystalline region of the film comprises an active channel for a high mobility thin film transistor.

30. The film of claim 29, wherein the second crystalline region of the film comprises an active channel for a low mobility thin film transistor.

31. The film of claim 25, wherein at least one of the first and second crystalline grain structures comprises an elongated, grain-boundary location controlled grain structure.

32. The film of claim 25, wherein the film comprises a semiconductor material.

33. The film of claim 25, wherein the film comprises a metal.

34. The film of claim 25, wherein the first film thickness is in the range of about 50 nm to about 500 nm.

35. The polycrystalline film of claim 25, wherein the second film thickness is in the range of about 20 nm to about 200 nm.

36. The film of claim 25, wherein the first and/or second crystalline regions comprise a single crystal subregion having a dimension large enough to accommodate an active channel of a thin film transistor.

37. A device comprising:

a plurality of thin film transistors (TFT), each TFT having a thin film active channel;

wherein at least a first TFT active channel has a first thickness and at least a second TFT active channel has a second thickness that is greater than the first thickness and the mobility of the first active channel is greater than the mobility of the second active channel.

38. A device of claim 37, wherein the first TFT active channel comprises an active channel for an integration area TFT.

39. A device of claim 37, wherein the second TFT active channel comprises an active channel for a pixel area TFT.

40. A device of claim 37, wherein the film comprises a semiconductor material.

41. A device of claim 37, wherein the first and/or second crystalline regions comprise a single crystal subregion having a dimension large enough to accommodate an active channel of a TFT.