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

• US 8,507,924 B2
• Filed: 03/10/2011
• Issued: 08/13/2013
• 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:
  US13/045,246
• Publication Number:
  US 20110169030A1
• Time in Patent Office: 887 Days
• Field of Search: 257/79, 257/98, 257/E33.067, 257/E33.068, 257/E33.074
• 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 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, such that the submicron roughness comprises structures with submicron height and width.

2. The light emitting diode of claim 1, wherein at least a portion of said submicron roughness comprises non-symmetrical surface structures on said light emitting surface.

3. The light emitting diode of claim 1, wherein at least some of the submicron roughness comprises multifaceted projections on said light emitting surface.

4. The light emitting diode of claim 1, wherein at least a portion of the submicron roughness comprises submicron projections comprising edges.

5. The light emitting diode of claim 1, wherein at least a portion of the submicron roughness comprises submicron projections comprising angles.

6. The light emitting diode of claim 1, wherein at least a portion of the submicron roughness comprises projections with an etch depth of approximately 500 nm.

7. The light emitting diode of claim 1, wherein at least a portion of the submicron roughness comprises projections with an etch depth of 1000 nm or less.

8. The light emitting diode of claim 1, wherein at least a portion of said submicron roughness comprises submicron projections with an average diameter of least about 100 nm.

9. The light emitting diode of claim 1, wherein at least a portion of said submicron roughness comprises submicron projections with an average diameter of up to about 200 nm.

10. The light emitting diode of claim 1, wherein a least a portion of said submicron roughness comprises submicron projections with an aspect ratio up to about 10.

11. The light emitting diode of claim 1, wherein a least a portion of said submicron roughness comprises submicron projections with an aspect ratio of approximately 5.

12. The light emitting diode of claim 1, wherein said submicron roughness is formed by an etch process.

13. The light emitting diode of claim 1, wherein said submicron roughness is formed by a dry etch process.

14. The light emitting diode of claim 1, wherein said submicron roughness is formed by a reactive ion etch (RIE) process.

15. 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, such that the submicron roughness comprises structures with submicron height and width.