Color correction for wafer level white LEDs

• US 8,193,544 B2
• Filed: 01/31/2011
• Issued: 06/05/2012
• Est. Priority Date: 12/23/2008
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Donofrio, Matthew
• Primary Examiner(s): Picardat, Kevin M
• Application Number:
  US13/018,254
• Publication Number:
  US 20110121344A1
• Time in Patent Office: 491 Days
• Field of Search: 438/22, 438/26, 438/27, 438/28, 438/29, 438/39, 257/79, 257/88, 257/89, 257/98, 257/99, 257/100
• US Class Current: 257/88
• CPC Class Codes: H01L 2933/0041 relating to wavelength conversion elements
• CPC Class Codes: H01L 33/005 Processes
• CPC Class Codes: H01L 33/44 characterised by the coatings, e.g. passivation layer or anti-reflective coating
• CPC Class Codes: H01L 33/508 having a non-uniform spatial arrangement or non-uniform concentration, e.g. patterned wavelength conversion layer, wavelength conversion layer with a concentration gradient of the wavelength conversion material

Abstract

A method for fabricating a plurality of LED chips comprises providing a plurality of LEDs and forming a plurality of spacers each of which is on at least one of the LEDs. Coating the LEDs with a conversion material, each of the spacers reducing the amount of conversion material over its one of the LEDs. This reduction causes the plurality of LED chips to emit a wavelength of light in response to an electrical signal that is within a standard deviation of a target wavelength. LEDs, LED chips and LED chip wafers are fabricated using the method according to the present invention. One embodiment of an LED chip wafer according to the present invention comprises a plurality of LEDs on a wafer and a plurality of a spacers, each of which is on a respective one of the LEDs. A conversion material at least partially covers the LEDs and spacers, with at least some light from the LEDs passing through the conversion material and is converted. The spacers cause the LED chips to emit light having a wavelength within a standard deviation compared to the similar LED chips without the spacers where at least some of the LED chips emit light a wavelength of light outside the standard deviation.

Claims

1. A light emitting device, comprising:

an emitter structure emitting light of a first color when biased with an electric signal, said emitter associated with a nominal color;

a spacer layer on said emitter structure; and

a conversion layer on said spacer layer configured to emit light of a second color in response to excitation by light from said emitter structure, such that said light emitting device emits a combination of said first and second colors;

wherein said conversion layer has a volume related to the difference between said first color and said nominal color associated with said emitter structure.

2. The light emitting device of claim 1, wherein said spacer layer reduces the amount of said second color of light emitted from said light emitting device when compared to a similar light emitting device without said spacer layer.

3. The light emitting device of claim 1, wherein said first and second colors of light combine to produce light within an acceptable deviation range from a target output color.

4. The light emitting device of claim 3, wherein said acceptable deviation range is defined by a 4-step MacAdam ellipse.

5. The light emitting device of claim 1, further comprising a conductive pedestal extending from said emitter structure though said spacer and conversion layers such that a portion of said pedestal is exposed for outside electrical connection.

6. The light emitting device of claim 1, wherein said spacer layer comprises a material that is transparent to said first color of light.

7. A light emitting device, comprising:

an emitter structure configured to emit a first color of light;

a spacer material on said emitter structure; and

a conversion material on said spacer material configured to emit a second color of light when excited by light from said emitter structure;

wherein said light emitting device emits a combination of said first and second colors, said combination having a smaller percentage of said second color than a similar emitter structure without said spacer material.

8. The light emitting device of claim 7, said combination adjusted to produce light within an acceptable deviation range from a target output color.

9. The light emitting device of claim 8, wherein said acceptable deviation range is defined by a 4-step MacAdam ellipse.

10. The light emitting device of claim 7, wherein said combination yields light having a white color.

11. The light emitting device of claim 7, further comprising a conductive pedestal extending from said emitter structure though said spacer and conversion materials such that a portion of said pedestal is exposed for outside electrical connection.

12. The light emitting device of claim 7, wherein said spacer material is transparent to said first color of light.

13. A light emitting device, comprising:

an emitter structure; and

an encapsulant, said encapsulant comprising;

a spacer material having a first volume; and

a conversion material having a second volume;

wherein said first volume and said second volume are inversely related.

14. The light emitting device of claim 13, said emitter structure configured to emit light having a first color, said conversion material configured to emit light having a second color when excited by said first color of light, said first and second colors combining to produce an output color.

15. The light emitter of claim 14, wherein said output color may be changed by adjusting the ratio of the first volume of said spacer material to the second volume of said conversion material.

16. The light emitting device of claim 14, wherein said output color is within a 4-step MacAdam ellipse of a target color.

17. A light emitter package, comprising:

a submount;

an emitter structure on said submount configured to emit light at a first wavelength;

a spacer material on said emitter structure; and

a conversion material on said spacer material configured to emit light at a second wavelength in response to light of said first wavelength;

wherein the volume of said conversion material is selected to provide a color correction based on difference between said first wavelength and a nominal wavelength associated with said emitter structure.

18. The light emitter package of claim 17, wherein said emitter structure is flip-chip mounted to said submount.

19. The light emitter package of claim 17, further comprising two electrodes electrically connected to said emitter structure such that it may be biased with an electrical signal, wherein said electrodes electrically contact said emitter structure from a side opposite said spacer material.

20. A light emitting device wafer, comprising:

a plurality of light emitters on a semiconductor wafer;

a plurality of encapsulants, each of said encapsulants on one of said light emitters, each of said encapsulants having approximately the same total volume, each of said encapsulants comprising;

at least one spacer element on a respective one of said light emitters;

a conversion material at least partially covering a respective one of said emitters and said spacer elements;

wherein at least two of said light emitters have encapsulants with different volumes of conversion material, said at least two emitters configured to emit light at approximately the same color point.

21. At least two light emitting devices, comprising:

at least two light emitter structures, at least two of said structures fabricated such that said structures emit at different wavelengths;

an encapsulant on each of said structures, said encapsulants having substantially the same volume, each of said encapsulants comprising an amount of spacer material and an amount of conversion material, said amount of spacer material inversely related to said amount of conversion material;

wherein said at least two light emitting devices are configured to have substantially similar physical dimensions and to emit light at approximately the same color point.

22. A method of manufacturing a light emitting device designed to emit light at a target output color point, comprising:

disposing a volume of spacer material on a light emitter structure;

disposing a volume of conversion material on said emitter structure, wherein said volume of spacer material is inversely related to said volume of conversion material, such that said light emitting device produces an output emission within an acceptable deviation range of said target output color point.