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

• US 7,534,633 B2
• Filed: 03/17/2005
• Issued: 05/19/2009
• Est. Priority Date: 07/02/2004
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Ibbetson, James, Li, Ting, Batres, Max
• Primary Examiner(s): Huynh; Andy
• Application Number:
  US11/083,460
• Publication Number:
  US 20060001046A1
• Time in Patent Office: 1,524 Days
• Field of Search: 438/4, 438/22, 438/46, 438/712, 257/77, 257/79, 257/103, 257/190, 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 light emitting diode (LED) formed by a process comprising:

growing a light emission region on a first-side surface of a substrate, the light emission region comprising a p-type layer of material, an n-type layer of material and an active layer between the p-type layer and the n-type layer;

applying a subtractive process to a second-side surface of the substrate opposite the first-side surface to create nonplanar features on the second-side surface; and

applying a reactive ion etch (RIE) process to at least a portion of the second-side surface for a time duration sufficient to texturize the second-side surface and remove damaged portions of the nonplanar features, the textured second-side surface comprising a light extraction surface.

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

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

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

5. The process of claim 1 wherein the RIE process is applied for a time period ranging from between approximately 15 and 180 minutes.

6. The process of claim 1 further comprising cutting a plurality of bevels into the second-side surface to form a plurality of etched features having associated surface areas that form at least part of the second-side surface.

7. The process of claim 6 wherein the cutting is performed prior to applying the RIE process.

8. The process of claim 1 further comprising forming a plurality of sidewall cuts forming sidewall surfaces that form at least part of the second-side surface.

9. The process of claim 8 wherein the cutting is performed prior to applying the RIE process.

10. The process of claim 1 further comprising forming p-type and n-type contacts on the first-side surface of the substrate such that the p-type and n-type contacts contact the p-type and n-type material of the light emission region, respectively.

11. The process of claim 1 further comprising forming a p-type contact on one side of the first and second side surface of the substrate and forming an n-type contact on the other side of the first and second side surface such that the p-type and n-type contacts contact the p-type and n-type material of the light emission region, respectively.

12. The LED of claim 1, wherein the subtractive process comprises cutting.

13. A light emitting diode (LED) formed by a process comprising:

growing a light emission region on a first-side surface of a substrate, the light emission region comprising a p-type layer of material, an n-type layer of material and an active layer between the p-type layer and the n-type layer;

creating cuts in a second-side surface of the substrate opposite the first-side surface to form at least one cut surface having a light absorbing damaged layer of material; and

applying a reactive ion etch (RIE) process to at least a portion of the cut surface for a time duration sufficient to form a texturized portion and to remove at least a portion of the damaged layer of material so that the LED exhibits increased light extraction compared to a similar LED without the RIE process applied to its cut surface.

14. The process of claim 13 wherein the RIE etching process is an inductively coupled plasma reactive ion etch (ICP-RIE) etching process.

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

16. The process of claim 13 wherein the RIE process is applied after growing the light emission region.

17. A light emitting diode (LED) formed by a process comprising:

growing a light emission region on a first-side surface of a substrate, the light emission region comprising a p-type layer of material, an n-type layer of material and an active layer between the p-type layer and the n-type layer; and

applying a reactive ion etch (RIE) process to at least a portion of the second-side surface of the substrate opposite the first-side surface for a time duration sufficient to change the morphology of the surface, the portion of the second-side surface having the change in morphology comprising a nonporous light extraction surface.

18. A light emitting diode (LED) formed by a process comprising:

growing a light emission region on a first-side surface of a substrate, the light emission region comprising a p-type layer of material, an n-type layer of material and an active layer between the p-type layer and the n-type layer;

creating cuts in a second-side surface of the substrate opposite the first-side surface to form at least one nonporous cut surface having a light absorbing damaged layer of material; and

applying a reactive ion etch (RIE) process to at least a portion of the nonporous cut surface for a time duration sufficient to remove at least a portion of the damaged layer of material so that the LED exhibits increased light extraction compared to a similar LED without the RIE process applied to its cut surface.

19. A light emitting diode (LED) formed by a process comprising:

growing a light emission region on a first-side surface of a substrate, the light emission region comprising a p-type layer of material, an n-type layer of material and an active layer between the p-type layer and the n-type layer;

applying a substractive process to a second-side surface of the substrate opposite the first-side surface to create nonplanar features on said second-side surface;

applying a reactive ion etch (RIE) process to at least a portion of the second-side surface for a time duration sufficient to texturize the second-side surface and remove damaged portions of the nonplanar features, the textured second-side surface comprising a light extraction surface; and

adding a transparent current spreading layer on at least a portion of the second-side surface.

20. The LED of claim 19, wherein the transparent current spreading layer comprises Indium Tin Oxide (ITO).

21. The LED of claim 19, wherein the subtractive process comprises cutting.