Wafer level phosphor coating method and devices fabricated utilizing method

• US 9,159,888 B2
• Filed: 09/07/2007
• Issued: 10/13/2015
• Est. Priority Date: 01/22/2007
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Chitnis, Ashay, Ibbetson, James, Keller, Bernd, Emerson, David T., Edmond, John, Bergmann, Michael J., Cabalu, Jasper S., Britt, Jeffrey C., Chakraborty, Arpan, Tarsa, Eric, Seruto, James, Fu, Yankun
• Primary Examiner(s): Rizkallah, Kimberly
• Assistant Examiner(s): Ligai, Maria
• Application Number:
  US11/899,790
• Publication Number:
  US 20080179611A1
• Time in Patent Office: 2,958 Days
• Field of Search: 257/98, 257/100, 257/95, 257/E33.06, 257/E33.061, 257/E33.062
• US Class Current: 1/1
• 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 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• 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 33/0095 Post-treatment of devices, e.g. annealing, recrystallisation or short-circuit elimination
• CPC Class Codes: H01L 33/36 characterised by the electrodes
• CPC Class Codes: H01L 33/387 with a plurality of electrode regions in direct contact with the semiconductor body and being electrically interconnected by another electrode layer
• CPC Class Codes: H01L 33/44 characterised by the coatings, e.g. passivation layer or anti-reflective coating
• CPC Class Codes: H01L 33/505 characterised by the shape, e.g. plate or foil
• 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
• CPC Class Codes: H01L 33/54 having a particular shape
• CPC Class Codes: H01L 33/62 Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls

Abstract

Methods for fabricating light emitting diode (LED) chips comprising providing a plurality of LEDs typically on a substrate. Pedestals are deposited on the LEDs with each of the pedestals in electrical contact with one of the LEDs. A coating is formed over the LEDs with the coating burying at least some of the pedestals. The coating is then planarized to expose at least some of the buried pedestals while leaving at least some of said coating on said LEDs. The exposed pedestals can then be contacted such as by wire bonds. The present invention discloses similar methods used for fabricating LED chips having LEDs that are flip-chip bonded on a carrier substrate and for fabricating other semiconductor devices. LED chip wafers and LED chips are also disclosed that are fabricated using the disclosed methods.

Claims

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

an LED comprising a textured surface, said LED comprising semiconductor layers;

a contact on said semiconductor layers;

a pedestal in electrical contact with and formed on said contact; and

a coating at least partially covering said LED, said coating comprising a light emitting surface, said pedestal extending through to the light emitting surface of said coating and exposed at the surface of said coating for electrical contact, wherein said coating is conformal such that said coating comprises a substantially uniform thickness over said textured surface.

2. The LED chip of claim 1, wherein said LED emits white light.

3. The LED chip of claim 1, wherein said coating is on the top surface of said LED.

4. The LED chip of claim 1, wherein said coating is on the top and side surfaces of said LED.

5. The LED chip of claim 1, wherein said LED is on a substrate.

6. The LED chip of claim 5, wherein said coating is also on the side surfaces of said substrate.

7. The LED chip of claim 1, further comprising a current spreading structure.

8. The LED chip of claim 7, wherein said coating comprises portions having different concentrations of phosphors.

9. The LED chip of claim 1, further comprising a current spreading layer.

10. The LED chip of claim 1, wherein the surface of said coating is textured.

11. The LED chip of claim 1, wherein said coating is shaped.

12. The LED chip of claim 1, wherein said coating comprises one or more phosphors.

13. The LED chip of claim 1, wherein said pedestal comprises one or more stud bumps.

14. The LED chip of claim 1, wherein said pedestal comprises a microwire.

15. The LED chip of claim 1, further comprising a reflective layer formed integral to said substrate.

16. The LED chip of claim 1, wherein said pedestal is exposed for external connection.

17. The LED chip of claim 1, wherein said coating is planarized to expose a top surface of said pedestal.

18. The LED chip of claim 1, wherein said pedestal covers less than all of a top surface of said contact.

19. The LED chip of claim 1, wherein said contact is directly on one of said semiconductor layers.

20. The LED chip of claim 1, wherein said pedestal comprises a single layer.

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

an LED mounted on a substrate, wherein a surface of said LED is textured for light extraction;

an integral coating at least partially covering said LEDs and comprising a light emitting surface, said integral coating formed by at least partially covering said LED with said coating at the wafer level and curing said coating at the wafer level such that said integral coating completely covers the sides of said substrate;

a contact on said LED; and

a pedestal in electrical contact with said contact, said pedestal further extending through and to the light emitting surface of said coating and exposed at the light emitting surface of said coating.

22. The LED chip of claim 21, wherein said coating is on the top surface of said LED.

23. The LED chip of claim 21, wherein said coating is on the top and side surfaces of the LED.

24. The LED chip of claim 21, wherein said coating is on the top and side surfaces of said LED and on the side surfaces of said substrate.

25. The LED chip of claim 21, further comprising a reflective layer.

26. The LED chip of claim 21, wherein the top surface of said LED is textured.

27. The LED chip of claim 21, wherein said substrate is at least partially transparent.

28. The LED chip of claim 21, wherein said substrate is opaque.

29. The LED chip of claim 21, further comprising a current spreading structure.

30. The LED chip of claim 21, further comprising a current spreading layer.

31. The LED chip of claim 21, wherein the surface of said coating is textured.

32. The LED chip of claim 21, wherein said coating is shaped.

33. The LED chip of claim 21, wherein said coating comprises one or more phosphors.

34. The LED chip of claim 33, wherein said coating comprises portions having different concentrations of phosphors.

35. The LED chip of claim 21, wherein said pedestal is exposed for external connection.

36. The LED chip of claim 21, wherein said coating is planarized to expose a top surface of said pedestal.

37. The LED chip of claim 21, wherein said contact is directly on one of said LED.

38. The LED chip of claim 21, wherein said pedestal comprises a single layer.

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

a plurality of LEDs comprising semiconductor layers, each of said LEDs comprising at least one textured surface to enhance light extraction, wherein said semiconductor layers are continuous between at least two of said plurality of LEDs;

a plurality of contacts, each of said contacts being on one of said textured surfaces;

a plurality of pedestals, each of which in electrical contact with and formed on one of said contacts; and

a coating at least partially covering said LEDs and comprising a light emitting surface, at least some of said pedestals extending through said light emitting surface and exposed at the surface of said coating for electrical contact, wherein said coating is conformal such that said coating comprises a substantially uniform thickness over said at least one textured surface.

40. The LED chip wafer of claim 39, wherein at least one of said pedestals comprises stud bumps.

41. The LED chip wafer of claim 39, wherein at least one of said pedestals comprises a microwire.

42. The LED chip wafer of claim 39, further comprising at least one current spreading structure on one of said LEDs, said current spreading structure in electrical contact with at least one of said contacts.

43. The LED chip wafer of claim 39, further comprising at least one current spreading layer.

44. The LED chip wafer of claim 39, wherein said textured LED surface comprises texture features that are larger than 10% of the thickness of said LED.

45. The LED chip wafer of claim 39, said coating comprises a textured surface.

46. The LED chip wafer of claim 45, wherein said coating textured surface comprises features larger than 10% of the thickness of said coating.

47. The LED chip wafer of claim 39, further comprising a groove between two adjacent LEDs, said coating at least partially filling said groove.

48. The LED chip wafer of claim 39, wherein said coating comprises multiple phosphors.

49. The LED chip wafer of claim 39, wherein said coating comprises scattering particles.

50. The LED chip wafer of claim 39, wherein said coating comprises a phosphor loaded binder.

51. The LED chip wafer of claim 39, wherein said LEDs are interconnected in an LED array.

52. The LED chip wafer of claim 39, further comprising a reflective layer formed integral to said substrate wafer.

53. The LED chip wafer of claim 39, wherein said coating comprises multiple portions with different concentrations of phosphors.

54. The LED chip wafer of claim 39, capable of emitting white light from said LEDs and coating.

55. The LED chip wafer of claim 39, wherein said pedestal is exposed for external connection.

56. The LED chip wafer of claim 39, wherein said coating is planarized to expose a top surface of said pedestal.

57. The LED chip wafer of claim 39, wherein said contact is directly on one of said textured surfaces.

58. The LED chip wafer of claim 39, wherein at least one of said plurality of pedestals comprises a single layer.