Substrate removal process for high light extraction LEDs

• US 9,559,252 B2
• Filed: 04/25/2011
• Issued: 01/31/2017
• Est. Priority Date: 02/23/2005
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Edmond, John
• Primary Examiner(s): TORNOW, MARK W
• Application Number:
  US13/093,622
• Publication Number:
  US 20110198626A1
• Time in Patent Office: 2,108 Days
• Field of Search: 257/98
• US Class Current: 1/1
• CPC Class Codes: H01L 33/007 comprising nitride compounds
• CPC Class Codes: H01L 33/0093 Wafer bonding; Removal of the growth substrate

Abstract

A method for fabricating light emitting diode (LEDs) comprises providing a plurality of LEDs on a substrate wafer, each of which has an n-type and p-type layer of Group-III nitride material formed on a SiC substrate with the n-type layer sandwiched between the substrate and p-type layer. A conductive carrier is provided having a lateral surface to hold the LEDs. The LEDs are flip-chip mounted on the lateral surface of the conductive carrier. The SiC substrate is removed from the LEDs such that the n-type layer is the top-most layer. A respective contact is deposited on the n-type layer of each of the LEDs and the carrier is separated into portions such that each of the LEDs is separated from the others, with each of the LEDs mounted to a respective portion of said carrier.

Claims

1. A light emitting diode (LED) device, comprising:

a carrier;

a plurality of semiconductor layers comprising at least an n-type layer and a p-type layer and arranged in a flip-chip orientation on said carrier with said n-type layer being exposed as a topmost of said semiconductor layers; and

a metal layer structure between said carrier and said p-type layer of said semiconductor layers, said metal layer structure comprising;

an ohmic contact layer having a first surface and a second surface, in which the first surface of the ohmic contact layer is coupled to said p-type layer of said plurality of semiconductor layers, wherein the ohmic contact layer is transparent,

a mirror layer having a first surface and a second surface in which the entire first surface of the mirror layer is coupled to the second surface of the ohmic contact layer, and

a barrier layer, coupled to said p-type layer, said ohmic contact layer, and said mirror layer, wherein said barrier layer is coupled closer to said carrier than said p-type layer, said ohmic contact layer, and said mirror layer, in which said barrier layer covers and surrounds, in conjunction with said p-type layer, said ohmic contact layer and said mirror layer;

wherein said metal layer structure provides light reflection.

2. The LED of claim 1, wherein said carrier is conductive.

3. The LED of claim 1, further comprising a contact on said n-type layer.

4. The LED of claim 3, further comprising a bondpad on said contact.

5. The LED of claim 1, wherein said semiconductor layers are capable of emitting light, and where said ohmic contact layer is transparent to light from said semiconductor layers.

6. The LED of claim 1, wherein said semiconductor layers are capable of emitting light, and wherein said ohmic contact layer is at least 50% transparent to light from said semiconductor layers.

7. The LED of claim 1, wherein said ohmic contact layer comprises platinum.

8. The LED of claim 1, wherein said semiconductor layers are capable of emitting light and wherein said mirror layer reflects light from said semiconductor layers.

9. The LED of claim 1, wherein said mirror layer comprises silver.

10. The LED of claim 1, wherein said barrier layer is arranged to at least partially prevent the mirror layer material from migrating to surrounding metals and semiconductor materials.

11. The LED of claim 1, further comprising a metal layer on said metal layer structure, said barrier layer at least partially preventing said metal layer from reacting with said mirror layer.

12. The LED of claim 1, wherein said barrier layer at least partially covers and surrounds said mirror layer and said ohmic contact layer.

13. The LED of claim 1, wherein said barrier layer can be formed of titanium, tungsten, platinum, or combinations thereof.

14. The LED of claim 1, further comprising a carrier layer, said semiconductor layers on said carrier layer, said metal layer structure between said carrier layer and said semiconductor layers.

15. The LED of claim 1, wherein said ohmic contact layer is directly on said mirror layer and directly on one of said plurality of semiconductor layers.

16. A semiconductor device, comprising:

a plurality of semiconductor layers mounted on a conductive carrier, with an n-type layer of said plurality of semiconductor layers being exposed; and

a metal layer structure coupled to a p-type layer of said plurality of semiconductor layers and arranged between said plurality of semiconductor layers and said conductive carrier, said metal layer structure comprising;

an ohmic contact layer having a first surface and a second surface, in which the first surface of the ohmic contact layer is coupled to said p-type layer of said plurality of semiconductor layers, wherein the ohmic contact layer is transparent,

a mirror layer having a first surface and a second surface, in which the entire first surface of the mirror layer is coupled to the second surface of the ohmic contact layer, and

a barrier layer, coupled to said p-type layer, said ohmic contact layer, said mirror layer, and said conductive carrier, in which said barrier layer covers and surrounds, in conjunction with said p-type layer, said ohmic contact and mirror layers;

wherein the barrier layer is between the mirror layer and the conductive carrier;

wherein said metal layer structure provides light reflection.

17. The device of claim 16, wherein said semiconductor layers comprise a plurality of light emitting diodes (LEDs).

18. The device of claim 16, further comprising a contact on said topmost of said semiconductor layers.

19. The device of claim 18, further comprising a bondpad on said contact.

20. The device claim 16, wherein said semiconductor layers are capable of emitting light, and where said ohmic contact layer is transparent to light from said semiconductor layers.

21. The device of claim 16, wherein said semiconductor layers are capable of emitting light, and wherein said ohmic contact layer is at least 50% transparent to light from said semiconductor layers.

22. The device of claim 16, wherein said semiconductor layers are capable of emitting light and wherein said mirror layer reflects light from said semiconductor layers.

23. The device of claim 16, wherein said barrier layer is arranged to at least partially prevent the mirror layer material from migrating to surrounding metals and semiconductor materials.

24. The device of claim 16, further comprising a metal layer on said metal layer structure, said barrier layer at least partially preventing said metal layer from reacting with said mirror layer.

25. The device of claim 16, wherein said barrier layer at least partially covers and surrounds said mirror layer and said ohmic contact layer.

26. The device of claim 16, wherein a surface of said semiconductor layers is textured.

27. The semiconductor device of claim 16, wherein said ohmic contact layer is directly on said mirror layer and directly on one of said plurality of semiconductor layers.

28. A semiconductor device, comprising:

a plurality of semiconductor layers mounted on a conductive carrier, with an n-type layer of said plurality of semiconductor layers being exposed; and

a metal layer structure coupled to a p-type layer of said plurality of semiconductor layers and arranged between said semiconductor layers and said conductive carrier, said metal layer structure comprising;

an ohmic contact layer having a first surface and a second surface, in which the first surface of the ohmic contact layer is coupled to a p-type layer of said plurality of semiconductor layers, wherein the ohmic contact layer is transparent,

a mirror layer having a first surface and a second surface, in which the entire first surface of the mirror layer is coupled to the second surface of the ohmic contact layer, and

a barrier layer, coupled to said p-type layer, said ohmic contact layer, said mirror layer, and said conductive carrier;

wherein said barrier layer covers at least two side surfaces of said mirror layer and said ohmic contact layer, said barrier layer comprising titanium or platinum, or a combination or alloy of two or more of titanium, tungsten, and platinum;

wherein the barrier layer is between the mirror layer and the conductive carrier;

wherein said metal layer structure provides light reflection.

29. The device of claim 28, further comprising an ohmic contact layer between said mirror layers and said semiconductor layers, wherein said barrier layer covers at least two side surfaces of said ohmic contact layer.

30. The semiconductor device of claim 28, wherein said ohmic contact layer is directly on said mirror layer and directly on one of said plurality of semiconductor layers.

31. A semiconductor device, comprising:

a plurality of semiconductor layers coupled to a conductive carrier, with an n-type layer of said plurality of semiconductor layers being exposed, and wherein a surface of said plurality of semiconductor layers is textured; and

a metal layer structure coupled to a p-type layer of said plurality of semiconductor layers and arranged between said plurality of semiconductor layers and said conductive carrier, wherein said metal layer structure comprises;

an ohmic contact layer having a first surface and a second surface, in which the first surface of the ohmic contact layer is coupled to said p-type layer of said plurality of semiconductor layers, wherein the ohmic contact layer is transparent,

a mirror layer having a first surface and a second surface, in which the entire first surface of the mirror layer is coupled to the second surface of the ohmic contact layer, and

a barrier layer, coupled to said p-type layer, said ohmic contact layer, said mirror layer, and said conductive carrier, in which said barrier layer covers and surrounds, in conjunction with said p-type layer, said mirror layer and said ohmic contact layer, wherein said barrier layer comprises titanium or platinum, or a combination or alloy of two or more of titanium, tungsten, and platinum;

wherein the barrier layer is between the mirror layer and the carrier;

wherein said metal layer structure comprising said three layer structure provides light reflection.

32. The semiconductor device of claim 31, wherein said ohmic contact layer is directly on said mirror layer and directly on one of said plurality of semiconductor layers.