White LEDs with emission wavelength correction

• US 8,558,252 B2
• Filed: 08/26/2011
• Issued: 10/15/2013
• Est. Priority Date: 08/26/2011
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Ibbetson, James, Keller, Bernd, Letoquin, Ronan, Donofrio, Matthew, Bergmann, Michael
• Primary Examiner(s): Tran, Long K
• Assistant Examiner(s): Tran, Dzung
• Application Number:
  US13/219,486
• Publication Number:
  US 20130049021A1
• Time in Patent Office: 781 Days
• Field of Search: 257/79, 257/88, 257/98, 438/27, 438/29
• US Class Current: 257/88
• CPC Class Codes: H01L 2933/0041 relating to wavelength conversion elements
• CPC Class Codes: H01L 33/0095 Post-treatment of devices, e.g. annealing, recrystallisation or short-circuit elimination
• CPC Class Codes: H01L 33/504 Elements with two or more wavelength conversion materials

Abstract

Methods for fabricating semiconductor devices such as LED chips with emission wavelength correction and devices fabricated using these methods. Different embodiments include sequential coating methods that provide two or more coatings or layers of conversion material over LEDs, which can be done at the wafer level. The methods are particularly applicable to fabricating LED chips that emit a warm white light, which typically requires covering LEDs with one or more wavelength conversion materials such as phosphors. In one embodiment, a base wavelength conversion material is applied to the semiconductor devices. A portion of the base conversion material is removed. At least two different tuning wavelength conversion materials are also applied to the semiconductor devices, either before or after the application of the base conversion material.

Claims

1. A method for fabricating light emitting devices, comprising:

coating a plurality of semiconductor devices with a base wavelength conversion material, said semiconductor devices emitting over a range of wavelengths;

removing a portion of said base wavelength conversion material; and

disposing a tuning wavelength conversion material on said plurality of semiconductor devices, said tuning wavelength material comprising at least two tuning phosphors each having a different emission spectrum, such that said emission spectrums are also different from an emission spectrum of said base wavelength conversion material;

wherein the volume of said tuning wavelength conversion material is calculated based on the output lighting characteristics of said semiconductor devices and said base wavelength conversion material.

2. The method of claim 1, where said tuning wavelength conversion material comprises at least first and second phosphors.

3. The method of claim 2, said tuning wavelength conversion material comprising said first and second phosphors in an approximate volumetric ratio.

4. The method of claim 2, wherein said semiconductor devices are fabricated to emit blue light, said base wavelength conversion material comprises a yellow phosphor, said first tuning phosphor comprises a red tuning phosphor, and said second tuning phosphor comprises a green tuning phosphor.

5. The method of claim 1, wherein said tuning wavelength conversion material is disposed onto each of said semiconductor devices individually.

6. The method of claim 1, wherein said tuning wavelength conversion material is disposed onto multiple semiconductor devices at the same time.

7. The method of claim 1, further comprising probing said semiconductor devices prior to disposing said tuning wavelength conversion material to determine the properties and quantity of said tuning wavelength conversion material necessary to achieve a desired color point.

8. The method of claim 1, further comprising calculating the volume of said at least one tuning phosphors to be disposed over each of said semiconductor devices.

9. The method of claim 1, further comprising heating said semiconductor devices prior to disposing said tuning wavelength conversion material thereon.

10. The method of claim 1, further comprising removing a portion of said base wavelength conversion material.

11. The method of claim 10, wherein said removing a portion of said base wavelength conversion material comprises removing more of said base wavelength conversion material than is necessary to achieve light emission at a desired color point.

12. The method of claim 10, wherein said removing a portion of said base wavelength conversion material comprises grinding said base wavelength conversion material down to a desired thickness.

13. The method of claim 10, wherein said removing a portion of said base wavelength conversion material comprises etching said base wavelength conversion material down to a desired thickness.

14. The method of claim 1, wherein disposing said tuning wavelength conversion material on said plurality of semiconductor devices comprises spraying said tuning wavelength conversion material onto each of said semiconductor devices.

15. The method of claim 14, wherein said tuning conversion material is sprayed onto said semiconductor devices using a single nozzle.

16. The method of claim 14, wherein said tuning conversion material is sprayed onto said semiconductor devices using multiple nozzles.

17. The method of claim 1, wherein said base wavelength conversion layer is applied to said semiconductor devices first, and the tuning wavelength conversion material is applied to said semiconductor device thereafter.

18. The method of claim 1, wherein said tuning wavelength material is applied to said semiconductor devices first, and said base wavelength material is applied to said semiconductor devices thereafter.

19. The method of claim 1, wherein said light emitting devices emit within a color point region defined by a 3-step MacAdam ellipse.

20. The method of claim 1, wherein said light emitting devices emit within a color point region defined by a 2-step MacAdam ellipse.

21. The method of claim 1, wherein said light emitting devices emit within a color point region defined by a 1-step MacAdam ellipse.

22. A light emitting device comprising:

an emitter structure;

a base conversion layer comprising a first wavelength conversion material on said emitter structure; and

a tuning conversion layer comprising at least second and third wavelength conversion materials on said emitter structure, said second and third wavelength conversion materials each having a different emission spectrum, such that said emission spectrums are also different from an emission spectrum of said base conversion layer;

wherein the volume of said tuning conversion layer is calculated based on the output lighting characteristics of said emitter structure and said base conversion layer.

23. The light emitting device of claim 22, said tuning conversion layer comprising said second and third wavelength conversion materials in an approximate volumetric ratio.

24. The light emitting device of claim 22, said second wavelength conversion material comprising a red phosphor and said third wavelength conversion material comprising a green phosphor.

25. The light emitting device of claim 22, wherein said emitter structure is fabricated to emit light in the blue wavelength range.

26. The light emitting device of claim 22, said light emitting structure comprising a plurality of light emitters.

27. The light emitting device of claim 22, wherein said light emitting device emits within a color point region defined by a 3-step MacAdam ellipse.

28. The light emitting device of claim 22, wherein said light emitting device emits within a color point region defined by a 2-step MacAdam ellipse.

29. The light emitting device of claim 22, wherein said light emitting device emits within a color point region defined by a 1-step MacAdam ellipse.

30. A light emitter package, comprising:

at least one light emitter on a surface;

first and second electrodes electrically connected to said at least one emitter;

a base conversion layer comprising a first wavelength conversion material; and

a tuning conversion layer comprising at least second and third wavelength conversion materials, said second and third wavelength conversion materials each having a different emission spectrum, such that said emission spectrums are also different from an emission spectrum of said base conversion layer;

wherein the volume of said tuning conversion layer is calculated based on the output lighting characteristics of said at least one emitter and said base conversion layer.

31. The light emitter package of claim 30, said tuning conversion layer further comprising a binder material, said second and third wavelength conversion materials intermixed in said binder.

32. The light emitter package of claim 30, said at least one light emitter fabricated to emit blue light, said first wavelength conversion material comprising a yellow phosphor, said second wavelength conversion material comprising a green phosphor, and said third wavelength conversion material comprising a red phosphor.

33. The light emitter package of claim 30, wherein said second and third wavelength conversion materials are disposed in said tuning conversion layer in an approximate volumetric ratio.

34. The light emitter package of claim 30, said light emitter package designed to output white light.

35. The light emitter package of claim 30, wherein said at least one light emitter device emits within a color point region defined by a 3-step MacAdam ellipse.

36. The light emitter package of claim 30, wherein said at least one light emitter device emits within a color point region defined by a 1-step MacAdam ellipse.

37. The light emitter package of claim 30, wherein said at least one light emitter device emits within a color point region defined by a 2-step MacAdam ellipse.