Systems and Methods of Laser Texturing and Crystallization of Material Surfaces

• US 20100219506A1
• Filed: 12/21/2006
• Published: 09/02/2010
• Est. Priority Date: 12/21/2005
• Status: Active Grant

• Current Assignee: University of Virginia Patent Foundation (University of Virginia)
• Original Assignee: University of Virginia Patent Foundation (University of Virginia)
• Inventors: Gupta, Mool C., Nayak, Barada K.
• Granted Patent: US 8,753,990 B2
• Time in Patent Office: Days
• US Class Current: 257/618
• CPC Class Codes: B23K 26/355 Texturing
• CPC Class Codes: H01L 21/02532 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/02587 Structure
• CPC Class Codes: H01L 21/02609 Crystal orientation
• 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 21/3247 for altering the shape, e.g. smoothing the surface
• CPC Class Codes: H01L 31/0236 Special surface textures
• CPC Class Codes: H01L 31/1872 Recrystallisation
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product
• CPC Class Codes: Y10T 428/12389 having variation in thickness

Abstract

The surface of a material is textured and crystallized in a single step by exposing the surface to pulses from an ultrafast laser. The laser treatment causes pillars to form on the treated surface. These pillars provide for greater light absorption. The crystallization of the material provides for higher electric conductivity and changes in optical properties of the material. The method may be performed in a gaseous environment, so that laser assisted chemical etching will aid in the texturing of the surface. This method may be used on various material surfaces, such as semiconductors, metals, ceramics, polymers, and glasses.

Claims

1. A method for texturing a surface of a semiconductor material, comprising:

providing an etching gas in an area around the surface of the material;

irradiating a portion of the surface with short laser pulses; and

translating at least one of the surface and a laser beam to allow the short laser pulses to irradiate another portion of the surface;

wherein the method produces a periodic array of pillars on the surface, resulting in changes in properties of the surface.

2. The method of claim 1, wherein the method additionally produces nanospikes atop the pillars.

3. The method of claim 2, further comprising sharpening the nanospikes by at least one of chemical etching and ion etching after irradiating the surface.

4. The method of claim 1, wherein the laser pulses have a duration of between one femtosecond and one microsecond.

5. The method of claim 4, wherein the laser pulses have a duration of between one femtosecond and hundreds of picoseconds.

6. The method of claim 1, wherein the laser pulses have a laser pulse energy density of between 0.1 J/cm² and 1.4 J/cm².

7. The method of claim 1, wherein the laser pulses have a wavelength of between 200 and 1600 nm.

8. The method of claim 1, wherein irradiating the surface further comprises scanning the surface in a plurality of directions.

9. The method of claim 1, wherein irradiating the surface further comprises scanning the surface in a single direction a plurality of times.

10. The method of claim 1, further comprising controlling a surface texture by controlling a polarization state of the laser pulses.

11. The method of claim 1, further comprising controlling an electrical conductivity of the material by controlling texturing parameters.

12. The method of claim 1, wherein irradiating the surface comprises at least partially crystallizing the irradiated surface.

13. The method of claim 1, further comprising controlling a spacing between adjacent pillars by controlling a wavelength of the laser pulses, a laser pulse energy density, and a number of laser pulses.

14. The method of claim 1, wherein the etching gas comprises at least one of sulfur hexafluoride gas, hydrogen chloride gas, helium gas, and argon gas.

15. The method of claim 1, wherein the etching gas has a pressure of no more than 0.1 atmospheres.

16. The method of claim 1, wherein the etching gas comprises a gaseous plasma.

34. A method of using the textured surface of claim 1 to provide a photovoltaic device.

35. A method of using the textured surface of claim 1 to provide a photodetector.

36. A method of using the textured surface of claim 1 or 18 to provide a high-efficiency heat sink for an electronic device.

37. A method of using the textured surface of claim 1 or 18 to provide a very high electric field for electron emission.

38. A method of using the textured surface of claim 1 or 18 to generate catalytic activity.

39. A method of using the textured surface of claim 1 or 18 to perform osteointegration of a body implant.

40. A method of using the textured surface of claim 1 or 18 to control the flow of air or fluid over the surface.

41. A method of using the textured surface of claim 1 or 18 to create a two-dimensional array of micro or nano dimensioned ordered tips.

42. A method of using the textured surface of claim 1 or 18 to manufacture an optical beam block which absorbs substantially all light from the visible to the far-infrared.

43. A method of using the textured surface of claim 1 or 18 in micro fluidic applications.

44. The method of claim 1 or 18, further comprising controlling a color of the surface.

45. A method of using the textured surface of claim 1 or 18 to produce a master for replication.

46. The method of claim 1 or 18, further comprising processing the surface with chemical etching to provide nano or micro pores on the surface.

47. The method of claim 1 or 18, further comprising controlling an emissivity of the surface.

48. The method of claim 1 or 18, further comprising writing text or images on the surface by controlling a light reflectivity.

49. A method of using the textured surface of claim 1 or 18 to provide a radiation shield which operates in a broad spectral range.

50. A method of using the textured surface of claim 1 or 18 to provide an infrared sensor.

52. The method of claim 1, wherein the changed properties are at least one of optical properties, thermal properties, and electrical properties.

17. A method for texturing a surface of a semiconductor material, comprising:

providing an etching gas in an area around the surface of the material;

irradiating a portion of the surface with short laser pulses while simultaneously crystallizing the portion of the surface; and

translating at least one of the surface and a laser beam to allow the short laser pulses to irradiate another portion of the surface while simultaneously crystallizing the other portion of the surface;

wherein the method produces pillars on the surface, resulting in changes in properties of the surface.

18. A method for texturing a metallic surface, comprising:

irradiating a portion of the metallic surface with short laser pulses; and

translating at least one of the surface and a laser beam to allow the short laser pulses to irradiate another portion of the surface;

wherein the method produces pillars on the surface, resulting in changes in properties of the surface.

19. The method of claim 18, wherein the pillars are produced in a periodic array.

20. The method of claim 18, further comprising providing an etching gas in an area around the surface.

21. The method of claim 20, wherein the etching gas comprises at least one of sulfur hexafluoride gas, hydrogen chloride gas, helium gas, and argon gas.

22. The method of claim 20, wherein the etching gas has a pressure of no more than 0.1 atmospheres.

23. The method of claim 20, wherein the etching gas comprises a gaseous plasma.

24. The method of claim 18, wherein the surface is in air at atmospheric pressure.

25. The method of claim 18, wherein the laser pulses have a duration of between one femtosecond and one microsecond.

26. The method of claim 25, wherein the laser pulses have a duration of between one femtosecond and hundreds of picoseconds.

27. The method of claim 18, wherein the laser pulses have a laser pulse energy density of between 0.1 J/cm² and 1.4 J/cm².

28. The method of claim 18, wherein the laser pulses have a wavelength of between 200 and 1600 nm.

29. The method of claim 18, wherein irradiating the surface further comprises scanning the surface in a plurality of directions.

30. The method of claim 18, further comprising controlling a surface texture by controlling a polarization state of the laser pulses.

31. The method of claim 18, further comprising controlling an electrical conductivity of the material by controlling texturing parameters.

51. A method of using the textured surface of claim 18 to prevent corrosion and provide adhesion.

53. The method of claim 18, wherein the changed properties are at least one of optical properties, thermal properties, and electrical properties.

32. A semiconductor surface, comprising a portion on which pillars are formed with nanospikes atop the pillars by irradiating the surface with short laser pulses while a substantially pure sulfur hexafluoride gas is provided around the surface.

33. A metallic surface, comprising a portion on which pillars are formed by irradiating the surface with short laser pulses.