LED with substrate modifications for enhanced light extraction and method of making same

• US 8,617,909 B2
• Filed: 04/01/2009
• Issued: 12/31/2013
• Est. Priority Date: 07/02/2004
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Batres, Max, Ibbetson, James, Li, Ting, Saxler, Adam W.
• Primary Examiner(s): Huynh, Andy
• Application Number:
  US12/384,277
• Publication Number:
  US 20090233394A1
• Time in Patent Office: 1,735 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. Etched features, such as truncated pyramids, may be formed on the emitting surface, prior to the RIE process, by cutting into the surface using a saw blade or a masked etching technique. Sidewall cuts may also be made in the emitting surface prior to the RIE process. A light absorbing damaged layer of material associated with saw cutting is removed by the RIE process. The surface morphology created by the RIE process may be emulated using different, various combinations of non-RIE processes such as grit sanding and deposition of a roughened layer of material or particles followed by dry etching.

Claims

1. A method of fabricating a light emitting diode (LED) including a growth substrate having a light emitting surface, said method comprising:

growing an epitaxial light emission region on a surface of the growth substrate opposite the light emitting surface, wherein said light emission region includes an active layer configured to generate light;

applying a reactive ion etch (RIE) process to at least a portion of the light emitting surface of said growth substrate for a time duration sufficient to change the morphology of the light emitting surface of said growth substrate; and

forming a plurality of etched features associated with said light emitting surface prior to applying the RIE process.

2. The method of claim 1 wherein the RIE process is an inductively coupled plasma reactive ion etch (ICP-RIE) process.

3. The method of claim 1 wherein the RIE process is applied prior to growing the light emission region.

4. The method of claim 1 wherein the RIE process is applied after growing the light emission region.

5. The method of claim 1 wherein the etched features are formed by cutting a plurality of bevels into the light emitting surface.

6. The method of claim 5 wherein the cutting is done using an angled saw blade.

7. The method of claim 5 wherein the cutting is done using a masked etching technique.

8. The method of claim 1 further comprising forming a plurality of sidewall cuts associated with the light emitting surface prior to applying the RIE process.

9. The method of claim 1 further comprising:

forming at least one contact on the light emission region.

10. A method of fabricating an LED including a growth substrate and an epitaxial light emitting region, said growth substrate comprising a primary light emitting surface having at least one cut surface to increase light extraction with a light absorbing damaged layer of material and a light emission region on a surface of the substrate opposite the light emitting surface, said method comprising:

applying a reactive ion etch (RIE) process to the cut surface of said growth substrate for a time duration sufficient to remove at least a portion of the damaged layer of material.

11. The method of claim 10 wherein the RIE process is an inductively coupled plasma reactive ion etch (ICP-RIE) process.

12. The method of claim 10, wherein said light emission region includes an active layer configured to generate light.

13. The method of claim 10 wherein the RIE process is applied prior to growing the light emission region.

14. The method of claim 10 wherein the RIE process is applied after growing the light emission region.

15. The method of claim 10 wherein the at least one cut surface is formed by cutting a plurality of bevels into the light emitting surface.

16. The method of claim 15 wherein the cutting is performed using an angled saw blade.

17. The method of claim 15 wherein the cutting is performed using a masked etching technique.

18. The method of claim 10 further comprising:

Forming a plurality of sidewall cuts associated with the light emitting surface prior to applying the RIE process.

19. The method of claim 10 further comprising:

forming at least one contact on the light emission region.