SEMICONDUCTOR LIGHT EMITTING DEVICES WITH SEPARATED WAVELENGTH CONVERSION MATERIALS AND METHODS OF FORMING THE SAME

• US 20090039375A1
• Filed: 10/15/2008
• Published: 02/12/2009
• Est. Priority Date: 08/07/2007
• Status: Abandoned Application

• Current Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: LeToquin, Ronan P., Andrews, Peter Scott
• Application Number:
  US12/251,993
• Publication Number:
  US 20090039375A1
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: H01L 2224/32245 the item being metallic
• CPC Class Codes: H01L 2224/32257 the layer connector connecting to a bonding area disposed in a recess of the surface of the item
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/181 Encapsulation
• CPC Class Codes: H01L 33/504 Elements with two or more wavelength conversion materials
• 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 semiconductor device includes a semiconductor light emitting device (LED) that emits light having a first peak wavelength upon the application of a voltage thereto, and first and second phosphor-containing regions on the LED that receive the light and convert at least a portion of the light to light having a longer wavelength. The first phosphor-containing region is between the second phosphor-containing region and the LED so that a light ray emitted by the LED passes through the first phosphor-containing region before passing through the second phosphor-containing region. The first phosphor-containing region is configured to convert light emitted by the LED to light having a second peak wavelength and the second phosphor-containing region is configured to convert light emitted by the LED to light having a third peak wavelength, shorter than the second peak wavelength.

Claims

1. A semiconductor device, comprising:

a semiconductor light emitting device (LED) configured to emit light having a first peak wavelength upon the application of a voltage thereto; and

first and second phosphor-containing regions on the LED that are configured to receive light emitted by the LED and to convert at least a portion of the received light to light having a longer wavelength than the first peak wavelength;

wherein the first phosphor-containing region is between the second phosphor-containing region and the LED so that a light ray emitted by the LED passes through the first phosphor-containing region before passing through the second phosphor-containing region; and

wherein the first phosphor-containing region is configured to convert light emitted by the LED to light having a second peak wavelength and the second phosphor-containing region is configured to convert light emitted by the LED to light having a third peak wavelength, shorter than the second peak wavelength.

2. The semiconductor device of claim 1, wherein the first phosphor-containing region includes a first phosphor having a first excitation region and the second phosphor-containing region includes a second phosphor having a second excitation region, wherein the first peak wavelength is within the first and second excitation regions and wherein the second peak wavelength is outside the second excitation region.

3. The semiconductor device of claim 2, wherein an emission spectrum of the second phosphor-containing region is at least partially within the first excitation region.

4. The semiconductor device of claim 2, wherein the first peak wavelength comprises a blue or UV wavelength, the first phosphor comprises a red phosphor and the second phosphor comprises a green/yellow phosphor.

5. The semiconductor device of claim 1, further comprising a third phosphor-containing region on the second phosphor-containing region and remote from the first phosphor-containing region, wherein the third phosphor-containing region is configured to convert light emitted by the LED to light having a fourth peak wavelength that is shorter than the second peak wavelength and shorter than the third peak wavelength.

6. The semiconductor device of claim 5, wherein the first peak wavelength comprises a UV wavelength, the first phosphor comprises a red phosphor, the second phosphor comprises a green/yellow phosphor, and the third phosphor comprises a blue phosphor.

7. The semiconductor device of claim 1, further comprising an intermediate layer between the first phosphor-containing region and the second phosphor-containing region.

8. The semiconductor device of claim 7, wherein the intermediate layer comprises light scattering particles.

9. The semiconductor device of claim 7, wherein the intermediate layer comprises a transflective layer.

10. The semiconductor device of claim 1, wherein the first peak wavelength is between 400 and 500 nm, the second peak wavelength is between 580 and 670 nm, and the third peak wavelength is between 500 and 580 nm.

11. The semiconductor device of claim 1, wherein a surface of the second phosphor-containing region opposite the first phosphor-containing region is textured for light extraction.

12. The semiconductor device of claim 1, wherein the first phosphor-containing region comprises a plurality of discrete phosphor-containing regions on the LED structure, and wherein the second phosphor-containing region comprises a layer of phosphor-containing matrix material extending across the LED structure and on the plurality of discrete phosphor-containing regions remote from the LED.

13. The semiconductor device of claim 12, wherein the phosphor-containing regions comprise islands of phosphor-containing matrix material on the LED structure.

14. The semiconductor device of claim 12, wherein the phosphor-containing regions comprise recesses in the LED structure.

15. A semiconductor device, comprising:

a semiconductor light emitting device (LED) configured to emit light having a first peak wavelength upon the application of a voltage thereto; and

a plurality of first and second phosphor-containing regions on the LED that are configured to receive light emitted by the LED and to convert at least a portion of the received light to light having a longer wavelength than the first peak wavelength;

wherein the first and second phosphor-containing regions comprise discrete phosphor containing regions on a surface of the LED structure; and

wherein the first phosphor-containing region is configured to convert light emitted by the LED to light having a second peak wavelength and the second phosphor-containing region is configured to convert light emitted by the LED to light having a third peak wavelength, shorter than the second peak wavelength.

16. The semiconductor device of claim 15, wherein the first and second discrete phosphor containing regions are spaced apart from one another on the surface of the LED structure.

17. The semiconductor device of claim 16, further comprising an intermediate material between adjacent ones of the spaced apart first and second discrete phosphor containing regions.

18. The semiconductor device of claim 17, wherein the intermediate material has a lower index of refraction than the first discrete phosphor containing regions.

19. The semiconductor device of claim 18, wherein the intermediate material has a higher index of refraction than the second discrete phosphor containing regions.

20. The semiconductor device of claim 19, wherein the first discrete phosphor containing regions comprise a green/yellow phosphor and the second discrete phosphor containing regions comprise a red phosphor.

21. A method of forming a semiconductor device including an active region configured to emit light and a window layer configured to transmit the emitted light, comprising:

forming a plurality of discrete phosphor-containing regions on an LED structure that is configured to emit light having a first peak wavelength in response to an electrical current; and

forming an overlayer on the LED structure including the discrete phosphor-containing regions, wherein the overlayer comprises a phosphor that is different than phosphor in the discrete phosphor-containing regions;

wherein the discrete phosphor-containing regions are configured to convert light emitted by the LED to light having a second peak wavelength and the overlayer is configured to convert light emitted by the LED to light having a third peak wavelength that is shorter than the second peak wavelength.

22. The method of claim 21, wherein the discrete phosphor-containing regions include a first phosphor having a first excitation region and the overlayer includes a second phosphor having a second excitation region, wherein the first peak wavelength is within the first and second excitation regions and wherein the second peak wavelength is outside the first excitation region.

23. The method of claim 22, wherein an emission spectrum of the second phosphor is at least partially within the first excitation region.

25. The method of claim 21, wherein forming the plurality of discrete phosphor-containing regions comprises affixing a preformed silicone layer onto a semiconductor wafer, the preformed silicone layer including a plurality of recesses therein, and forming the discrete regions in the recesses.

26. The method of claim 21, wherein forming the plurality of discrete phosphor-containing regions comprises:

depositing a layer of matrix material on the LED structure;

selectively curing a portion of the matrix material; and

removing an uncured portion of the matrix material to form islands of matrix material on the LED structure.

27. The method of claim 26, wherein selectively curing the matrix material comprises:

forming a mask layer on the deposited layer of matrix material;

patterning the mask layer to expose a portion of the matrix material; and

curing the exposed portion of the matrix material.

28. The method of claim 26, wherein selectively curing the matrix material comprises bringing a heated plate with ridges into proximity with the matrix material, thereby causing selected portions of the matrix material adjacent the heated ridges to cure.

29. The method of claim 27, further comprising:

forming a metal contact on the LED structure;

wherein depositing the layer of matrix material comprises depositing the layer of matrix material on the LED structure and the metal contact; and

wherein the mask layer covers at least a portion of the metal contact.

30. The method of claim 26, further comprising:

depositing a second matrix material on the LED structure including the islands of matrix material;

forming a second mask on the second matrix material;

patterning the second mask to expose at least a portion of the substrate other than a portion of the LED structure on which the islands of matrix material are formed;

illuminating the exposed portion of the second matrix material with radiation having a wavelength sufficient to cure the exposed portion of the second matrix material; and

removing an unexposed portion of the second matrix material to form second islands of matrix material on the LED structure.

31. The method of claim 26, further comprising:

forming an overlayer on the LED structure including the islands of matrix material.

32. The method of claim 31, wherein the overlayer is formed on the LED structure before forming the first islands.

33. The method of claim 31, wherein the overlayer is formed on the LED structure after forming the first islands.

34. The method of claim 27, wherein the LED structure further comprises a semiconductor wafer including a plurality of dicing streets, and wherein the mask layer is formed at least over the plurality of dicing streets on the semiconductor wafer.

24. The method of claim 46, further comprising texturing the overlayer to increase light extraction from the semiconductor device.