Systems and methods of laser texturing and crystallization of material surfaces

• US 8,753,990 B2
• Filed: 12/21/2006
• Issued: 06/17/2014
• 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.
• Primary Examiner(s): Tornow, Mark
• Assistant Examiner(s): WARD, ERIC A
• Application Number:
  US12/158,553
• Publication Number:
  US 20100219506A1
• Time in Patent Office: 2,735 Days
• Field of Search: 216 58- 81, 977839-901, 977/963, 438/308, 438/487, 438795-799, 438/940
• US Class Current: 438/795
• 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 micro texturing a surface of a material, comprising:

providing a gaseous or vacuum environment in an area around the surface of the material;

irradiating a portion of the surface with short laser pulses;

moving at least one of the surface or a laser beam relative to each other to allow the short laser pulses to irradiate the surface;

wherein the method produces a periodic array of micro pillars, semi-periodic array of micro pillars, or a non-periodic array of micro pillars on the surface, resulting in changes in properties of the surface wherein nanospikes are produced atop the micro pillars;

wherein said material comprises a semiconductor;

wherein the laser pulses have a duration of between about one femtosecond and about 999 picoseconds; and

wherein the laser pulses have a wavelength of between about 400 and about 1,600 nm.

2. The method of claim 1, wherein said surface remains stationary and said laser beam moves.

3. The method of claim 1, wherein said laser beam remains stationary and said surface moves.

4. The method of claim 1, wherein moving comprises translating in the x-y direction or translating or rotating in the z-direction or both translating in the x-y direction and translating or rotating or moving in the z direction.

5. The method of claim 1 wherein, said laser beam moves relative to said surface by using a mirror, galvo-head, an optical element, or any combination thereof to change the path of said laser beam.

6. The method of claim 1, wherein said gaseous environment comprises air at atmospheric pressure, below atmospheric pressure, or above atmospheric pressure.

7. The method of claim 1, further comprising sharpening the nanospikes by at least one of chemical etching and ion etching after irradiating the surface.

8. The method of claim 1, wherein the laser pulses have a laser pulse energy density of between about 0.1 J/cm² and about 4.5 J/cm².

9. The method of claim 1, wherein the laser pulses have a wavelength of between 400 and 800 nm.

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

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

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

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

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

15. 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.

16. The method of claim 15, wherein said controlling further comprises controlling the spacing between adjacent pillars and/or their orientation by controlling an angle of incidence of said laser pulses or inclining the sample or combination thereof.

17. The method of claim 1, wherein gaseous environment comprises at least one of air, sulfur hexafluoride gas, hydrogen chloride gas, helium gas, argon gas, other fluoride based gasses, or other chloride based gases, or other chemical gases.

18. The method of claim 1, wherein said gaseous environment has a pressure of no more than 0.1 atmospheres.

19. The method of claim 1, wherein said gaseous environment comprises a gaseous plasma.

20. The method of claim 1, further comprising controlling of pillars by controlling said gaseous or vacuum environment.

21. The method of claim 1, further comprising controlling the formation of said pillars by post irradiation processing.

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

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

43. A method of using the textured surface of claim 1 or 24 to provide a photovoltaic device.

44. A method of using the textured surface of claim 1 or 24 to provide a photodetector.

45. A method of using the textured surface of claim 1 or 24 to provide a high-efficiency heat sink for an electronic device.

46. A method of using the textured surface of claim 1 or 24 to provide a very high electric field for electron emission.

47. A method of using the textured surface of claim 1 or 24 to generate catalytic activity.

48. A method of using the textured surface of claim 1 or 24 to perform osteointegration/osseointegration of a body implant.

49. A method of using the textured surface of claim 1 or 24 to control the flow of air or fluid over the surface.

50. A method of using the textured surface of claim 1 or 24 to create a two-dimensional array of micro or nano dimensioned ordered tips.

51. A method of using the textured surface of claim 1 or 24 in micro fluidic applications.

52. The method of claim 1 or 24, further comprising controlling a color of the surface.

53. A method of using the textured surface of claim 1 or 24 to produce a master for replication.

55. The method of using the textured surface of claim 1 or 24 to provide an element to control light reflection or transmission in an optical device.

56. The method of using the textured surface of claim 1 or 24 to provide an electrical device.

57. The method of claim 1 or 24, further comprising processing the surface with chemical etching to provide nano or micro pores on the surface.

58. The method of claim 1 or 24, further comprising controlling an emissivity of the surface.

59. The method of claim 1 or 24, further comprising writing text or images on the surface by controlling a light reflectivity.

60. A method of using the textured surface of claim 1 or 24 to provide a radiation shield which operates in a broad spectral range.

61. A method of using the textured surface of claim 1 or 24 to provide an infrared sensor.

62. A method of using the textured surface of claim 1 or 24 to prevent corrosion and provide adhesion.

24. A method for micro texturing a semiconductor surface, comprising:

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

moving at least one of the surface and a laser beam relative to each other to allow the short laser pulses to irradiate another portion of the surface;

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

wherein nanospikes are produced atop the micro pillars;

wherein the laser pulses have a duration of between about one femtosecond and about 999 picoseconds; and

wherein the laser pulses have a wavelength of between about 400 and about 1,600 nm.

25. The method of claim 24, wherein the pillars are produced in a periodic or non-periodic array.

26. The method of claim 24, wherein said surface remains stationary and said laser beam moves.

27. The method of claim 24, wherein said laser beam remains stationary and said surface moves.

28. The method of claim 24, wherein moving comprises translating in the x-y direction or translating or rotating in the z-direction or both translating in the x-y direction and translating or rotating or moving in the z direction.

29. The method of claim 24, wherein said laser beam moves relative to said surface by using a mirror, galvo-head, an optical element, or any combination thereof to change the path of said laser.

30. The method of claim 24, further comprising providing an environment of gas in an area around the surface.

31. The method of claim 30, wherein the environment of gas comprises at least one of air, sulfur hexafluoride gas, hydrogen chloride gas, helium gas, argon gas, other fluoride based gasses, or other chloride based gasses, or other chemical gasses.

32. The method of claim 30, wherein the environment of gas has a pressure of no more than 0.1 atmospheres.

33. The method of claim 30, wherein the environmet of gas comprises a gaseous plasma.

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

35. The method of claim 24, wherein the laser pulses have a laser pulse energy density of between about 0.1 J/cm² and about 4.5 J/cm².

36. The method of claim 24, wherein the laser pulses have a wavelength of between 400 and 800 nm.

37. The method of claim 24, wherein irradiating the surface further comprises scanning the surface in a plurality of directions.

38. The method of claim 24, further comprising controlling a surface texture by controlling a polarization state of the laser pulses.

39. The method of claim 24, further comprising controlling an electrical conductivity of the material by controlling texturing parameters.

40. The method of claim 24, further comprising controlling a periodicity of pillars by controlling said gaseous or vacuum environment.

41. The method of claim 24, further comprising controlling a periodicity of pillars by controlling process parameters.

42. The method of claim 24, further comprising controlling the formation of said pillars by post irradiation processing.

54. A method of using the textured surface of claim 24 to manufacture an optical beam block which absorbs substantially all light from the visible to the far-infrared.

63. The method of claim 24, wherein the changed properties are at least one of optical properties, thermal properties, and electrical properties.

64. The method claim 24, wherein the surface is in a vacuum environment.

65. A system for micro texturing a surface of a material comprising:

a chamber in an area around the surface of the material to provide a gaseous or vacuum environment;

an energy source providing a power supply for a radiation source, said radiation source for irradiating at least a portion of the surface;

a base for retaining said surface, said base or radiation source adapted to move relative to one another for irradiation wherein a periodic array of micro pillars or a non-periodic array of micro pillars on the surface, resulting in changes in properties of the surface;

wherein nanospikes are produced atop the micro pillars;

wherein said material comprises semiconductor;

wherein said irradiation has a duration of between about one femtosecond and about 999 picoseconds; and

wherein said laser pulses have a wavelength of between about 400 nanometers and about 1,600 nanometers.

66. The system of claim 65, wherein said both a periodic array of pillars and a non-periodic array of pillars on the surface are produced, resulting in changes in properties of the surface.

67. The system of claim 65, wherein said radiation source comprises a laser.

68. The system of claim 65, wherein said chamber provides a means for controlling the environment therein.

69. The system of claim 65, wherein said base is movable in the x-y direction or rotatable or movable in the z direction or both movable in the x-y direction and movable or rotatable in the z direction.

70. A system for micro texturing a surface of a material comprising:

a chamber in an area around the surface of the material to provide a gaseous or vacuum environment;

an energy source providing a power supply for a radiation source, said radiation source for irradiating at least a portion of the surface, wherein said surface is provided in a gaseous or vacuum environment;

wherein said material comprises a semiconductor;

a base for retaining said surface, said base or radiation source adapted to move relative to one another for irradiation wherein micro pillars are produced on said portion of the surface, resulting in changes in properties of the surface;

wherein nanospikes are produced atop the micro pillars;

wherein said irradiation has a duration of between about one femtosecond and 999 picoseconds; and

wherein said laser pulses have a wavelength of between about 400 and about 1,600 nanometers.

71. A method for micro texturing a surface of a material, comprising:

providing a gaseous or vacuum environment in an area around the surface of the material;

irradiating a portion of the surface with energy pulses;

moving at least one of the surface or an energy beam relative to each other to allow the energy pulses to irradiate the surface;

wherein the method produces a periodic array of micro pillars or a non-periodic array of micro pillars on the surface, resulting in changes in properties of the surface;

wherein nanospikes are produced atop the micro pillars;

wherein said material comprises semiconductor;

wherein said irradiation has a duration of between about one femtosecond and about 999 picoseconds; and

wherein said energy pulses have a wavelength of between about 400 and about 1,600 nanometers.