SEMICONDUCTOR LIGHT EMITTING DEVICES WITH APPLIED WAVELENGTH CONVERSION MATERIALS AND METHODS FOR FORMING THE SAME

• US 20110089456A1
• Filed: 12/22/2010
• Published: 04/21/2011
• Est. Priority Date: 08/07/2007
• Status: Active Grant

• Current Assignee: CREE Led Incorporated (Smart Global Holdings Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Le Toquin, Ronan P., Andrews, Peter S., Ibbetson, James
• Granted Patent: US 9,054,282 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• 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 2924/00012 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 2933/0091 Scattering means in or on the semiconductor body or semiconductor body package H01L33/22 takes precedence
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• 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 structure includes an active region configured to emit light upon the application of a voltage thereto, a window layer configured to receive the light emitted by the active region, and a plurality of discrete phosphor-containing regions on the window layer and configured to receive light emitted by the active region and to convert at least a portion of the received light to a different wavelength than a wavelength of light emitted by the active region. Methods of forming a semiconductor structure including an active region configured to emit light and a window layer include forming a plurality of discrete phosphor-containing regions on the window layer.

Claims

1. A semiconductor device, comprising:

an active region configured to emit light upon the application of a voltage thereto;

a window layer configured to receive the light emitted by the active region; and

a plurality of discrete phosphor-containing regions on the window layer and configured to receive light emitted by the active region and to convert at least a portion of the received light to a different wavelength than a wavelength of light emitted by the active region.

2. The semiconductor device of claim 1, wherein the window layer comprises a substrate or an epitaxial layer.

3. The semiconductor device of claim 1, wherein the window layer comprises a layer of silicone.

4. The semiconductor device of claim 1, wherein the phosphor-containing regions comprise recesses that extend into and/or through the window layer.

5. The semiconductor device of claim 4, wherein a first plurality of the recesses have a first diameter smaller than or about equal to an average diameter of a first type of phosphor particle in the discrete phosphor-containing regions so that the first plurality of recesses are configured to trap the first type of phosphor particle.

6. The semiconductor device of claim 5, wherein a second plurality of the recesses have a second diameter larger than the first diameter.

7. The semiconductor device of claim 6, wherein the second diameter is smaller than or about equal to an average diameter of a second type of phosphor particle in the discrete phosphor-containing regions so that the second plurality of recesses are configured to trap the second type of phosphor particle.

8. The semiconductor device of claim 4, wherein the recesses have a diameter substantially larger than a diameter of a phosphor particle, The semiconductor device further comprising a phosphor-loaded matrix material in the recesses.

9. The semiconductor device of claim 8, wherein the phosphor-loaded matrix material comprises silicone.

10. The semiconductor device of claim 1, wherein the phosphor-containing regions comprise islands of phosphor-loaded matrix material on the window layer.

11. The semiconductor device of claim 10, wherein the phosphor-containing regions comprise a first plurality of phosphor-containing regions comprising a first type of phosphor configured to convert light emitted by the active region to a first wavelength and a second plurality of phosphor-containing regions comprising a second type of phosphor configured to convert light emitted by the active region to a second wavelength.

12. The semiconductor device of claim 11, wherein the first wavelength comprises a wavelength in the yellow portion of the spectrum, the second wavelength comprises a wavelength in the red portion of the spectrum, and the active region is configured to emit light in the blue or UV portions of the spectrum.

13. The semiconductor device of claim 11, wherein the first wavelength comprises a wavelength in the red portion of the spectrum, the second wavelength comprises a wavelength in the green portion of the spectrum, and the active region is configured to emit light in the blue or UV portions of the spectrum.

14. The semiconductor device of claim 13, further comprising a third plurality of phosphor-containing regions comprising a phosphor configured to convert light emitted by the active region to a third wavelength, wherein the third wavelength comprises a wavelength in the blue portion of the spectrum.

15. The semiconductor device of claim 1, further comprising an overlayer on the window layer.

16. The semiconductor device of claim 15, wherein the overlayer comprises a light scattering layer.

17. The semiconductor device of claim 15, wherein the overlayer comprises a phosphor that is different from phosphor in the discrete phosphor-containing regions.

18. The semiconductor device of claim 15, wherein the overlayer is patterned to increase light extraction from the LED structure.

19. The semiconductor device of claim 1, further comprising a light scattering layer, wherein the plurality of discrete phosphor-containing regions are on the light scattering layer.

20. The semiconductor device of claim 1, wherein the window layer comprises a preformed layer on the active region.

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 the window layer.

22. The method of claim 21, wherein forming the plurality of discrete phosphor-containing regions comprises etching recesses in the window layer.

23. The method of claim 22, wherein forming the plurality of discrete phosphor-containing regions comprises:

dispensing a phosphor-loaded matrix material into the recesses in the window layer.

24. The method of claim 22, wherein the recesses are spaced apart by a distance that is about equal to an average diameter of a phosphor particle in the discrete phosphor-containing region and wherein the recesses have a diameter that is about the same as the average diameter of a phosphor particle, wherein forming the plurality of discrete phosphor-containing regions comprises passing a phosphor dust including discrete phosphor particles across the window layer such that at least some of the phosphor particles are trapped by the recesses.

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.

26. The method of claim 21, wherein the active region is part of a light emitting diode (LED) structure, and 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 26, wherein the matrix material comprises a phosphor-loaded matrix material.

30. The method of claim 26, wherein the matrix material comprises silicone embedded with phosphor particles.

31. The method of claim 26, further comprising applying phosphor particles to the deposited layer of matrix material.

32. The method of claim 31, further comprising applying phosphor particles to the islands of matrix material.

33. The method of claim 26, wherein curing the exposed portion of the matrix material comprises illuminating the exposed portion of the matrix material with light.

34. The method of claim 26, further comprising:

forming a metal contact on the LED structure;

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

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

35. The method of claim 26, further comprising:

heat curing the deposited layer of phosphor-loaded matrix material.

36. 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 a light 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.

37. The method of claim 26, further comprising:

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

38. The method of claim 37, wherein the overlayer is formed on the LED structure before forming the first islands.

39. The method of claim 37, wherein the overlayer is formed on the LED structure after forming the first islands.

40. The method of claim 26, wherein the LED structure further comprises a semiconductor wafer, and wherein the mask layer is formed at least over a plurality of dicing streets on the semiconductor wafer.

41. The method of claim 26, wherein the LED structure further comprises a semiconductor wafer, the method further comprising:

dicing the semiconductor wafer after forming the islands of material.

42. The method of claim 26, wherein depositing the layer of matrix material on the LED structure comprises spin-coating a matrix material onto the LED structure.

43. The method of claim 21, wherein forming the plurality of discrete phosphor-containing regions on the window layer comprises:

forming a screen on the window layer, the screen including a plurality of openings therein exposing the window layer;

depositing phosphor particles in the openings; and

removing the screen.

44. The method of claim 43, wherein the phosphor particles comprise first phosphor particles, the method further comprising depositing second phosphor particles in regions of the window layer from which the screen was removed, wherein the second phosphor particles have at least one optical property that is different from the first phosphor particles.

45. The method of claim 21, wherein forming the plurality of discrete phosphor-containing regions on the window layer comprises:

depositing first phosphor particles having a first diameter on the window layer, wherein the first phosphor particles are deposited so that spaces exist between the first phosphor particles; and

depositing second phosphor particles in the spaces between the first phosphor particles;

wherein the second phosphor particles have at least one optical property that is different from the first phosphor particles.

46. The method of claim 21, further comprising:

forming an overlayer on the window layer including the discrete phosphor-containing regions.

47. The method of claim 46, wherein the overlayer comprises a phosphor that is different than phosphor in the discrete phosphor-containing regions.

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