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

• US 8,034,647 B2
• Filed: 06/22/2010
• Issued: 10/11/2011
• Est. Priority Date: 07/02/2004
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Saxler, Adam W., Batres, Max, Ibbetson, James, Li, Ting
• Primary Examiner(s): NGUYEN, NIKI HOANG
• Assistant Examiner(s): Nguyen; Tram H
• Application Number:
  US12/821,069
• Publication Number:
  US 20100273280A1
• Time in Patent Office: 476 Days
• Field of Search: 257/257, 257 93-103, 257/E31.001, 257/E31.005, 257/E31.099, 257/E31.105, 257/E25.019, 257/E31.13, 257/E21.216, 257/13, 257 79- 92, 257/918, 257E51018-E51022, 257E33001-E33077, 257/E25.028, 257/E25.032, 257/E31.058, 257/E31.063, 257/E31.115, 257/E21.032, 257E27133- 27139, 438 22- 47, 438/69, 438/493, 438/503, 438/507, 438/956
• US Class Current: 438/29
• 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 processes, such as a reactive ion etch (RIE) process to the light emitting surface. In one embodiment, the changed surface morphology takes the form of a moth-eye surface. The surface morphology created by the RIE process may be emulated using different 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) comprising:

growing a light emission region on a first surface of a substrate, the light emission region including an active layer between first and second oppositely doped layers;

creating a moth-eye morphology in at least a portion of a second surface of the substrate;

forming a first contact on the second surface of the substrate and in electrical contact with one of the first or second doped layers; and

forming a second contact in electrical contact with the other of the first or second doped layers.

2. The method of claim 1 wherein the moth-eye morphology is created by reactive ion etching the second surface.

3. The method of claim 1 wherein the moth-eye morphology is created by:

forming a layer on the second surface having a surface morphology; and

etching the layer and underlying second surface to create the moth-eye morphology.

4. The method of claim 3 wherein the layer is formed by:

depositing a substantially uniform layer of material on the second surface; and

forming the surface morphology in the uniform layer.

5. The method of claim 4 wherein the surface morphology is formed in the uniform layer by annealing the uniform layer at a temperature and for a time duration sufficient to form the surface morphology.

6. The method of claim 4 wherein the surface morphology is formed in the uniform layer by:

depositing a mask layer over the uniform layer; and

etching the uniform layer through the mask layer to form the surface morphology.

7. The method of claim 4 wherein the surface morphology is formed in the uniform layer by:

depositing nano-particles over the uniform layer; and

etching the particles and underlying layer to form the surface morphology.

8. The method of claim 3 wherein the layer is formed by depositing a layer of nano-particles on the second surface.

9. The method of claim 3 wherein the layer and second surface are etched using a dry etching process.

10. The method of claim 9 further comprising applying a chemical etch to the second surface after the second surface has been dry etched.

11. The method of claim 9 further comprising annealing the second surface after the second surface has been dry etched.

12. The method of claim 1 wherein the morphology is created using a grit polishing process.

13. A method of fabricating a light emitting diode (LED) comprising:

growing a light emission region on a first surface of a substrate, the light emission region including an active layer between first and second oppositely doped layers;

forming a layer on a second surface of the substrate, the layer having a refractive index substantially the same as the substrate and a moth-eye surface morphology;

forming a first contact on the layer and in electrical contact with one of the first or second doped layers; and

forming a second contact in electrical contact with the other of the first or second doped layers.

14. The method of claim 13 wherein the layer is formed by:

depositing material on the second surface under growth conditions that form the moth-eye surface morphology.

15. The method of claim 13 wherein the layer is formed by:

depositing nano-particles on the second surface, the particles having size, shape and density that form the moth-eye surface; and

mechanically fixing the nano-particles to the second surface.