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

• US 20060267029A1
• Filed: 08/02/2006
• Published: 11/30/2006
• Est. Priority Date: 07/02/2004
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Li, Ting
• Granted Patent: US 7,932,106 B2
• Time in Patent Office: Days
• US Class Current: 257/79
• 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 the light emitting surface, wherein the mask is attached to a nano-patterned template and the submicron patterns were formed using the template;

removing the template from the mask; and

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

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

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

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

5. The method of claim 1 wherein the dry 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 at least one of a sacrificial layer and a mold release layer to the template.

8. The method of claim 6, further comprising removing the template after transferring the 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 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 metal hard-mask comprising submicron patterns, the method comprising:

providing a nano-patterned template comprising at least one porous material, wherein the nano-pattern is an inherent property of the at least one material; and

depositing a thin layer of metal on the template.

16. The method of claim 15, wherein the thickness of the metal layer is less than about 200 nm.

17. The method of claim 15, wherein the template comprises at least one of an inorganic polymer and an organic polymer.

18. The method of claim 17, wherein the template comprises anodic aluminum oxide.

19. The method of claim 15, wherein the template further comprises at least one of a sacrificial layer and a mold release layer.

20. A light emitting diode, comprising:

a plurality of semiconductor layers at least one of which has a light emitting surface;

at least a portion of said light emitting surface having a high aspect ratio submicron roughness to enhance light extraction.

21. A semiconductor device, comprising:

a plurality of semiconductor layers at least one of which has an exposed surface;

at least a portion of said exposed surface having a high aspect ratio submicron roughness.

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

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

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

23. The method of claim 22, wherein said mask is attached to a nano-patterned template and the submicron patterns were formed using said template.

24. The method of claim 22, further comprising removing the template from the mask.