Light emitting diode with high aspect ratio submicron roughness for light extraction and methods of forming

• US 7,932,106 B2
• Filed: 08/02/2006
• Issued: 04/26/2011
• Est. Priority Date: 07/02/2004
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Li, Ting
• Primary Examiner(s): Huynh; Andy
• Application Number:
  US11/498,418
• Publication Number:
  US 20060267029A1
• Time in Patent Office: 1,728 Days
• Field of Search: 438/22, 438/46, 438/712, 257/79, 257/E33.067, 257/E33.068, 257/E33.074
• US Class Current: 438/22
• CPC Class Codes: H01L 2224/0401 Bonding areas specifically adapted for bump connectors, e.g. under bump metallisation [UBM]
• CPC Class Codes: H01L 2224/13 of an individual bump connector
• CPC Class Codes: H01L 2924/00011 Not relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/10155 being other than a cuboid
• CPC Class Codes: H01L 2924/10158 at the passive surface
• CPC Class Codes: H01L 33/0095 Post-treatment of devices, e.g. annealing, recrystallisation or short-circuit elimination
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers

Abstract

The surface morphology of an LED light emitting surface is changed by applying a reactive ion etch (RIE) process to the light emitting surface. High aspect ratio, submicron roughness is formed on the light emitting surface by transferring a thin film metal hard-mask having submicron patterns to the surface prior to applying a reactive ion etch process. The submicron patterns in the metal hard-mask can be formed using a low cost, commercially available nano-patterned template which is transferred to the surface with the mask. After subsequently binding the mask to the surface, the template is removed and the RIE process is applied for time duration sufficient to change the morphology of the surface. The modified surface contains non-symmetric, submicron structures having high aspect ratio which increase the efficiency of the device.

Claims

1. A method of fabricating a light emitting diode having a modified light emitting surface, the method comprising:

transferring a metal hard-mask having submicron patterns to a light emitting surface, wherein the metal hard-mask is attached to a nano-patterned template by a sacrificial layer and the submicron patterns were formed using the nano-patterned template;

removing the nano-patterned template from the metal hardmask by etching away said sacrificial layer; and

applying a first etch process to at least one portion of the light emitting surface comprising the metal hard-mask, wherein the first etch process is applied for a time duration sufficient to change a morphology of the surface in the at least one portion of the light emitting surface covered by the metal hard-mask.

2. The method of claim 1, wherein the metal hard-mask is transferred to the surface using a resist bond process.

3. The method of claim 1, wherein the modified light emitting surface is a back surface.

4. The method of claim 1, wherein the morphology of the modified light emitting surface comprises high aspect ratio submicron roughness.

5. The method of claim 1 wherein said etch process is a reactive ion etch process.

6. The method of claim 1, further comprising depositing a thin metal layer on a template having an inherent nano-pattern, thereby forming the metal hard-mask having submicron patterns.

7. The method of claim 6, further comprising applying said sacrificial layer and a mold release layer to the nano-patterned template.

8. The method of claim 6, further comprising removing the nano-patterned template after transferring the metal hard-mask to the surface.

9. The method of claim 1, further comprising depositing a layer of dielectric material on the light emitting surface.

10. The method of claim 1, further comprising depositing a layer of binder material on the light emitting surface.

11. The method of claim 10, further comprising binding the metal hard-mask to the binder material on the light emitting surface.

12. The method of claim 11, wherein the metal hard-mask is bound to the surface using a resist bond process.

13. A light emitting diode fabricated by the method of claim 1.

14. The light emitting diode of claim 13, wherein the modified light emitting surface comprises high aspect ratio submicron roughness.

15. A method of fabricating a semiconductor device having a modified surface, the method comprising:

transferring a metal mask having submicron patterns to at least a portion of a surface of said semiconductor device;

applying a first etch process to at least one portion of the surface comprising the metal mask, wherein the etch process is applied for a time duration sufficient to change a morphology of the surface in the at least one portion of the surface covered by the metal mask; and

applying a second etch process after said time duration to the surface comprising the metal mask and removing the metal mask from said semiconductor device not removed by said first etch process.

16. The method of claim 15, wherein said mask is attached to a nano-patterned template and the submicron patterns were formed using said template.

17. The method of claim 15, further comprising removing the template from the mask.

18. A method of fabricating a light emitting diode (LED) having a modified light emitting surface, the method comprising:

applying an etch process to at least one portion of the light emitting surface of the LED, wherein the etch process is applied for a time duration sufficient to change a morphology of the surface in the at least one portion of the light emitting surface so that said surface comprising submicron projections with an aspect ratio of at least about 5;

wherein applying the etch process comprises texturing the at least one portion of the surface to form the submicron projections with the aspect ratio of at least about 5.

19. The method of claim 18, further comprising transferring a mask having submicron patterns to said light emitting surface, wherein said etch is applied to said mask.

20. The method of claim 18, wherein applying the etch process comprises applying a dry etch process.

21. The method of claim 18, wherein applying the etch process comprises applying a reactive ion etch (RIE) process.

22. The method of claim 18, wherein applying the etch process comprises applying an inductively coupled plasma reactive ion etch (ICP-RIE) process.

23. The method of claim 18, wherein the etch process is applied for a time duration of at least about 15 minutes.

24. The method of claim 18, wherein the etch process is applied for a time duration of up to about 180 minutes.

25. The method of claim 18, wherein at least some of the submicron projections comprises non-symmetrical surface structures on the surface.

26. The method of claim 18, wherein at least some of the submicron projections comprises multifaceted projections on the surface.

27. The method of claim 18, wherein at least some of the submicron projections comprises edges on the surface.

28. The method of claim 18, wherein at least some of the submicron projections comprises angles on the surface.

29. The method of claim 18, wherein at least some of the submicron projections comprises an etch depth of at least about 500 nm in the surface.

30. The method of claim 18, wherein at least some of the submicron projections comprises an etch depth of up to about 1000 nm in the surface.

31. The method of claim 18, wherein at least some of the submicron projections comprises an average diameter of least about 100 nm.

32. The method of claim 18, wherein at least some of the submicron projections comprises an average diameter of up to about 200 nm.

33. The method of claim 18, wherein the aspect ratio of the submicron projections is up to about 10.

39. The method of claim 24, wherein the etch process is applied for a time duration of at least about 15 minutes.

40. The method of claim 24, wherein the etch process is applied for a time duration of up to about 180 minutes.

34. A method of fabricating a light emitting diode (LED) having a modified light emitting surface, the method comprising:

applying an etch process to at least one portion of the light emitting surface of said LED, wherein the etch process is applied for a time duration sufficient to change a morphology of the surface in the at least one portion of the light emitting surface so that said surface has projections with a height that is at least twice a size of a wavelength of light emitted by said light emitting diode, said surface comprising submicron projections with an aspect ratio of at least about 5;

wherein applying the etch process comprises texturing the at least one portion of the surface to form the submicron projections with the aspect ratio of at least about 5.

35. The method of claim 34, further comprising transferring a mask having submicron patterns to said light emitting surface, wherein said etch is applied to said mask.

36. The method of claim 34, wherein applying the etch process comprises applying a dry etch process.

37. The method of claim 34, wherein applying the etch process comprises applying a reactive ion etch (RIE) process.

38. The method of claim 34, wherein applying the etch process comprises applying an inductively coupled plasma reactive ion etch (ICP-RIE) process.

41. The method of claim 34, wherein at least some of the submicron projections comprises non-symmetrical surface structures on the surface.

42. The method of claim 34, wherein at least some of the submicron projections comprises multifaceted projections on the surface.

43. The method of claim 34, wherein at least some of the submicron projections comprises edges on the surface.

44. The method of claim 34, wherein at least some of the submicron projections comprises angles on the surface.

45. The method of claim 34, wherein at least some of the submicron projections comprises an etch depth of at least about 500 nm in the surface.

46. The method of claim 34, wherein at least some of the submicron projections comprises an etch depth of up to about 1000 nm in the surface.

47. The method of claim 34, wherein at least some of the submicron projections comprises an average diameter of least about 100 nm.

48. The method of claim 34, wherein at least some of the submicron projections comprises an average diameter of up to about 200 nm.

49. The method of claim 34, wherein the aspect ratio of the submicron projections is up to about 10.