LEDs using single crystalline phosphor and methods of fabricating same

• US 8,101,443 B2
• Filed: 12/07/2010
• Issued: 01/24/2012
• Est. Priority Date: 04/10/2008
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Chakraborty, Arpan
• Primary Examiner(s): Mandala, Victor A
• Application Number:
  US12/961,789
• Publication Number:
  US 20110073881A1
• Time in Patent Office: 413 Days
• Field of Search: 438/22, 438/29, 438/47, 438/41, 438/45, 438/46, 257/79, 257/94, 257/98, 257/E33.06, 257/E33.061
• US Class Current: 438/29
• CPC Class Codes: H01L 2933/0041 relating to wavelength conversion elements
• CPC Class Codes: H01L 33/0093 Wafer bonding; Removal of the growth substrate
• CPC Class Codes: H01L 33/502 Wavelength conversion materials

Abstract

Methods for fabricating LED chips from a wafer and devices fabricated using the methods with one method comprising depositing LED epitaxial layers on an LED growth wafer to form a plurality of LEDs on the growth wafer. A single crystalline phosphor is bonded over at least some the plurality of LEDs so that at least some light from the covered LEDs passes through the single crystalline phosphor and is converted. The LED chips can then be singulated from the wafer to provide LED chips each having a portion of said single crystalline phosphor to convert LED light.

Claims

1. A method for fabricating light emitting diode (LED) chips from a wafer, comprising:

depositing LED epitaxial layers on an LED growth wafer to form a plurality of LEDs on said growth wafer; and

bonding a single crystalline phosphor over at least some said plurality of LEDs so that at least some light from the covered ones of said LEDs passes through said single crystalline phosphor and is converted.

2. The method of claim 1, further comprising planarizing said single crystalline phosphor.

3. The method of claim 1, further comprising removing said growth wafer from said plurality of LEDs.

4. The method of claim 1, wherein said single crystalline phosphor provides mechanical support for said LED epitaxial layers.

5. The method of claim 1, wherein a surface of said single crystalline phosphor is textured.

6. The method of claim 1, further comprising etching said LEDs to form lateral geometry devices, and depositing first and second contacts on said LEDs, wherein said single crystalline phosphor is bonded to a surface opposite said first and second contacts.

7. The method of claim 1, further comprising forming openings in said single crystalline phosphor to access contacts on said LEDs.

8. The method of claim 3, further comprising mounting said LED wafer to a carrier wafer.

9. The method of claim 8, further comprising removing said carrier wafer following said bonding of said single crystalline phosphor.

10. The method of claim 1, wherein said LED chips emit white light.

11. The method of claim 1, wherein said single crystalline phosphor comprises a yttrium aluminum garnet (YAG) host lattice.

12. The method of claim 11, wherein said single crystalline substrate further comprises a phosphor.

13. The method of claim 12, wherein the concentration of said phosphor is graded in said single crystalline substrate.

14. The method of claim 1, wherein said single crystalline substrate further comprises scattering particles.

15. The method of claim 1, further comprising singulating said LEDs from said wafer as individual LED chips or groups of LED chips.

16. A light emitting diode (LED) chip wafer, comprising:

a plurality of LEDs on a wafer;

a first single crystalline phosphor at least partially covering at least some of said LEDs such that during operation of the covered ones of said LEDs at least some light from said LEDs passes through said single crystalline phosphor and is converted.

17. The LED chip wafer of claim 16, wherein said first single crystalline phosphor provides mechanical support for at least some of said LEDs.

18. The LED chip wafer of claim 16, wherein said LEDs covered by said first single crystalline phosphor emit a white light combination of light from said LED and converted light from said first single crystalline phosphor.

19. The LED chip wafer of claim 16, wherein said first single crystalline phosphor comprises yttrium aluminum garnet (YAG).

20. The LED chip wafer of claim 19, wherein said first single crystalline phosphor further comprises a phosphor.

21. The LED chip wafer of claim 20, wherein the concentration of said phosphor is graded in said first single crystalline phosphor.

22. The LED chip wafer of claim 16, wherein said first single crystalline phosphor further comprises light scattering materials.

23. The LED chip wafer of claim 16, wherein said first single crystalline substrate further comprises a phosphor to absorb light from said LED and emit yellow light.

24. The LED chip wafer of claim 16, capable of being separated into LED chips.

25. The LED chip wafer of claim 16, wherein said LED covered by said first single crystalline phosphor emits a white light combination of LED light and down-converted light from said single crystalline phosphor.

26. The LED chip wafer of claim 16, wherein said LEDs further comprise contacts and said first single crystalline phosphor comprises openings to at least some of said contacts.

27. The LEDs chip wafer of claim 16, wherein said LEDs have lateral geometry and contacts.

28. The LED chip wafer of claim 27, wherein said first single crystalline phosphor covers said LEDs on a surface opposite the surface from which said contacts are accessed.

29. The LED chip wafer of claim 16, further comprising covering a least some of said LED with a second single crystalline phosphor.

30. The LED chip wafer of claim 16, wherein said LED wafer is sandwiched between said first and second single crystalline phosphors.

31. The LED chip wafer of claim 16, wherein said single crystalline phosphor is textured.

32. A method for fabricating light emitting diode (LED) chips from a wafer, comprising:

depositing LED epitaxial layers on an LED growth substrate to form an LED wafer with a plurality of LEDs;

bonding said LED wafer to a carrier wafer;

removing said LED growth substrate;

bonding a single crystalline phosphor over at least some of said plurality of LEDs so that light from at least some of said LEDs passes through said single crystalline phosphor and is converted; and

removing said carrier wafer.

33. The method of claim 32, further comprising planarizing said single crystalline phosphor.

34. The method of claim 32, wherein said single crystalline phosphor provides mechanical support for said LED epitaxial layers.

35. The method of claim 32, wherein a surface of said single crystalline phosphor is textured.

36. The method of claim 32, wherein said LED chips emit white light.

37. The method of claim 32, wherein said single crystalline phosphor comprises a yttrium aluminum garnet (YAG).

38. The method of claim 32, wherein said single crystalline substrate further comprises a phosphor.

39. The method of claim 32, further comprising singulating said LEDs from said wafer as individual LED chips or groups of LED chips.

40. The method of claim 32, further comprising forming a high reflectivity mirror on said LED epitaxial layers opposite to the said single crystalline.