SELECTIVE WET ETCHING AND TEXTURED SURFACE PLANARIZATION PROCESSES

• US 20110263128A1
• Filed: 04/22/2011
• Published: 10/27/2011
• Est. Priority Date: 04/22/2010
• Status: Active Grant

• Current Assignee: Luminus Devices Incorporated (Sanan Optoelectronics Company Limited)
• Original Assignee: Luminus Devices Incorporated (Sanan Optoelectronics Company Limited)
• Inventors: Lu, Hong, Duncan, Scott W.
• Granted Patent: US 9,558,954 B2
• Time in Patent Office: Days
• US Class Current: 438/745
• CPC Class Codes: H01L 21/30612 Etching of AIIIBV compounds
• CPC Class Codes: H01L 33/0093 Wafer bonding; Removal of the growth substrate
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers

Abstract

The present invention relates to systems and methods associated with selective wet etching and textured surface planarization. The systems and methods described herein can be used to etch a component of a multi-layer stack, such as a GaN layer. In some embodiments, the multi-layer stack can include a substrate having a patterned surface and a light generating region. The substrate can be removed from the first multi-layer stack to form a second multi-layer stack. In some embodiments, the pattern on the surface of the substrate can leave behind a pattern on a surface of the second multi-layer stack. Accordingly, in some cases, the surface of the second multi-layer stack can be wet etched, for example, to smoothen the surface. In some embodiments, removing the substrate can expose an N-face of a GaN layer, and the wet etch can be performed such that the N-face of the GaN layer is etched. In some embodiments, the multi-layer stack includes a light generating region and can be part of a light emitting device.

Claims

1. A method, comprising:

providing a first multi-layer stack, comprising;

a substrate including a patterned surface; and

a light generating region;

removing the substrate from the first multi-layer stack to form a second multi-layer stack; and

wet etching a surface of the second multi-layer stack.

2. The method of claim 1, wherein the substrate comprises sapphire, silicon, and/or silicon carbide.

3. The method of claim 1, wherein wet etching the surface of the second multi-layer stack is performed in the substantial absence of mechanical polishing and/or in the substantial absence of dry etching.

4. The method of claim 1, wherein the first multi-layer stack comprises a sacrificial layer.

5. The method of claim 4, wherein removing the substrate from the first multi-layer stack comprises decomposing at least a portion of the sacrificial layer.

6. The method of claim 1, wherein wet etching the surface of the second multi-layer stack comprises wet etching a surface of the second multi-layer stack that is exposed upon removal of the substrate.

7. The method of claim 1, wherein, after wet etching the surface of the second multi-layer stack, the surface has an RMS roughness of at most about 50 nanometers.

8. The method of claim 1, wherein the surface of the second multi-layer stack is etched, in a direction perpendicular to the surface, at a rate of at least about 0.01 micrometers/hour.

9. The method of claim 1, wherein wet etching comprises exposing the surface of the second multi-layer stack to an etchant comprising an acid and/or an oxidizing agent.

10. The method of claim 9, wherein the acid comprises phosphoric acid and/or nitric acid.

11. The method of claim 9, wherein the oxidizing agent comprises hydrogen peroxide and/or nitric acid.

12. A method, comprising:

providing a multi-layer stack comprising a GaN layer and an underlying material;

removing at least a portion of the underlying material to expose an N-face of the GaN layer; and

wet etching the N-face of the GaN layer.

13. The method of claim 12, wherein the underlying material comprises sapphire, silicon, and/or silicon carbide.

14. The method of claim 12, wherein wet etching the N-face of the GaN layer is performed in the substantial absence of mechanical polishing and/or in the substantial absence of dry etching.

15. The method of claim 12, wherein the N-face of the GaN layer is etched, in a direction perpendicular to the surface of the N-face, at a rate of at least about 0.01 micrometers/hour.

16. The method of claim 12, wherein the multi-layer stack comprises a light generating region.

17. The method of claim 12, wherein the wet etching is performed using an etchant at a temperature of less than about 100°

C.

18. The method of claim 12, wherein the wet etching is performed using an etchant comprising an acid and/or an oxidizing agent.

19. The method of claim 18, wherein the acid comprises phosphoric acid and/or nitric acid.

20. The method of claim 18, wherein the oxidizing agent comprises hydrogen peroxide and/or nitric acid.

21. The method of claim 18, wherein the etchant comprises phosphoric acid and hydrogen peroxide.

22. The method of claim 21, wherein the ratio of phosphoric acid to hydrogen peroxide, by volume, is between about 3:

1 and about 60;

1.