Substrate removal process for high light extraction LEDs

• US 20060189098A1
• Filed: 02/23/2005
• Published: 08/24/2006
• Est. Priority Date: 02/23/2005
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Edmond, John
• Granted Patent: US 7,932,111 B2
• Time in Patent Office: Days
• US Class Current: 438/460
• 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 method for fabricating semiconductor based light emitting devices, comprising:

providing a plurality of semiconductor layers on a silicon carbide (SiC) substrate wafer, said plurality of semiconductor layers for a plurality of light emitting devices, each of said emitting devices comprising epitaxial layers;

providing a carrier;

flip-chip mounting said emitting devices on said carrier such that said emitting devices are sandwiched between said carrier and substrate wafer;

removing said SiC substrate wafer from said emitting devices;

separating said carrier into portions such that each of said emitting devices is separated from the others, with each of said emitting devices mounted to a respective portion of said carrier.

2. The method of claim 1, wherein said plurality of semiconductor layers are separated into individual emitting devices on said SiC substrate before said flip-chip mounting.

3. The method of claim 1, wherein said plurality of semiconductor layers are separated into individual emitting devices on said carrier, after said flip-chip mounting and after said removal of said SiC substrate.

4. The method of claim 1, wherein each of said emitting devices is mounted to said carrier by solder.

5. The method of claim 1, comprising the further step of mounting each of said separated devices and its conductive carrier to a device package.

6. The method of claim 5, wherein each of said separated devices is mounted to a package using silver epoxy or solder.

7. The method of claim 5, wherein said device is encased in an encapsulating material.

8. The method of claim 7, wherein said encapsulating material comprises an epoxy.

9. The method of claim 1, wherein said removing said substrate wafer from said devices comprises mechanically grinding off said substrate wafer.

10. The method of claim 1, wherein said removing said substrate wafer from said devices comprises mechanically grinding off a portion of said substrate wafer and exposing the remaining of said substrate wafer to an etch to the remaining of said substrate wafer.

11. The method of claim 1, wherein said removing said substrate wafer from said devices comprises exposing the said substrate wafer to an etch.

12. The method of claim 1, wherein each of said semiconductor devices further comprises a lift-off layer between said substrate and epitaxial layers.

13. The method of claim 10, wherein said removing of said substrate from each of said devices comprises exposing said lift-off layer to a photo electrochemical etch.

14. The method of claim 12, wherein said removing of said substrate from each of said devices comprises exposing said lift-off layer to a solution and applying a light source, the combination of said solution and light source causing said lift-off layer to etch without etching the surrounding materials.

15. The method of claim 12, wherein said lift-off layer comprises a material from the group InGaN, AlInGaN and AlInGaAs, and wherein said solution comprises KOH and water and said light source has an approximate 400 nanometer (nm) wavelength.

16. The method of claim 12, wherein said removing of said substrate from each of said devices comprises applying a laser light source to said device that is transparent to said substrate and epitaxial structure, but is absorbed by said lift-off layer.

17. The method of claim 12, wherein said substrate comprises SiC, said epitaxial structure comprises GaN, and said lift-off layer comprises a material from the group InGaN, AlInGaN and AlInGaAs, wherein removing said lift-off layer comprises illuminating said device with laser light having a wavelength in the range of approximately 390 and 450 nm.

18. The method of claim 17, wherein said laser light has a wavelength of approximately 400 nm.

19. The method of claim 1, wherein said substrate is silicon carbide and said epitaxial layers are Group-III nitride, said removing of each said substrate from each of said devices comprises exposing said devices to a nitrogen tri fluoride etch.

20. The method of claim 1, wherein said separating of said carrier into portions comprises dicing said carrier.

21. The method of claim 1, wherein said separating of said carrier into portions comprises scoring said carrier and then breaking said carrier along said scores.

22. The method of claim 1, wherein each of said plurality of semiconductor light emitting devices comprises a light emitting diode (LED) comprising Group-III nitride epitaxial layers formed on a silicon carbide (SiC) substrate.

23. The method of claim 1, wherein said carrier further comprises a reflective layer to reflect light from each of said semiconductor light emitting devices emitted toward said carrier.

24. The method of claim 1, wherein each of said semiconductor light emitting devices further comprises one or more textured surfaces to enhance light extraction.

25. The method of claim 1, wherein said carrier further comprises a junction diode, each of said separated devices having a portion of said diode, each of said devices coupled to said diode portion to protect said device from damage by electrostatic discharge.

26. The method of claim 1, wherein said carrier is made of a conductive material.

27. The method of claim 1, wherein said carrier is made of a semiconductive material, said carrier further comprising one or more layers of conductive material.

28. A method for fabricating light emitting diodes (LEDs), comprising:

providing a plurality semiconductor layers on a SiC substrate wafer, said semiconductor layers forming a plurality of LEDs, each of said LEDs having an n-type layer and p-type layer, said n-type layer sandwiched between said substrate wafer and p-type layer;

providing a carrier having a lateral surface to hold said LEDs;

flip-chip mounting said LEDs on said carrier lateral surface such that said LEDs are sandwiched between said substrate wafer and said carrier;

removing said SiC substrate from said LEDs such that said n-type layer is the top-most layer;

depositing a respective contact on said n-type layer of each of said LEDs; and

separating said carrier into portions such that each of said LEDs is separated from the others, with each of said LEDs mounted to a respective portion of said carrier.

29. The method of claim 28, wherein each of said LEDs further comprises a plurality of metal layers to reflect light.

30. The method of claim 29, wherein said metal layers for each of said LEDs is between said p-type layer and said carrier.

31. The method of claim 28, wherein said removing each said substrate from each of said LEDs comprises mechanically grinding off each of said substrate.

32. The method of claim 31, further comprising exposing each of said devices to fluorine based plasma etch to remove any of each of said substrates remaining on said devices after said mechanical grinding.

33. The method of claim 28, wherein each of said LEDs further comprises a lift-off layer between said substrate and said n-type layer wherein said removing of said substrate from each of said LEDs comprises removing said lift off layer.

34. The method of claim 28, wherein said lift-off layer is removed by one of the methods from the group consisting of, exposing said lift-off layer to a photo electrochemical etch, exposing said lift-off layer to an etch solution and applying a light source, applying a laser light source to said lift-off layer.

35. The method of claim 28, wherein said removing of each said substrate from each of said LEDs comprises exposing said substrates to a nitrogen tri fluoride etch.

36. The method of claim 28, wherein said separating of said carrier into portions comprises dicing said carrier, or scoring said carrier and then breaking said carrier along said scores.

37. The method of claim 28, wherein said carrier further comprises a reflective layer to reflect light from each of said LEDs emitted toward said carrier.

38. The method of claim 28, wherein each of said LEDs further comprises one or more textured surfaces to enhance light extraction.

39. The method of claim 28, wherein said carrier further comprises a junction diode, each of said separated LEDs having a portion of said junction diode, each of said LEDs coupled to said junction diode portion to protect said device from damage by electrostatic discharge.