Light-emitting dies incorporating wavelength-conversion materials and related methods

• US 9,190,581 B2
• Filed: 09/24/2014
• Issued: 11/17/2015
• Est. Priority Date: 01/24/2012
• Status: Active Grant

• Current Assignee: Epistar Corporation
• Original Assignee: Cooledge Lighting Inc.
• Inventors: Tischler, Michael A.
• Primary Examiner(s): GREEN, TELLY D
• Application Number:
  US14/495,313
• Publication Number:
  US 20150079709A1
• Time in Patent Office: 419 Days
• Field of Search: 257/98, 257/89, 438/27, 438/29, 438/25, 438/28, 438/31, 313/503, 313/501, 313/512, 362/231, 362/97, 362/237, 362/606
• US Class Current: 1/1
• CPC Class Codes: H01L 2224/04105 Bonding areas formed on an encapsulation of the semiconductor or solid-state body, e.g. bonding areas on chip-scale packages
• CPC Class Codes: H01L 2224/1403 Bump connectors having different sizes, e.g. different diameters, heights or widths
• CPC Class Codes: H01L 2224/73204 the bump connector being embedded into the layer connector
• CPC Class Codes: H01L 24/96 the devices being encapsulated in a common layer, e.g. neo-wafer or pseudo-wafer, said common layer being separable into individual assemblies after connecting
• CPC Class Codes: H01L 24/97 the devices being connected to a common substrate, e.g. interposer, said common substrate being separable into individual assemblies after connecting
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• 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 2924/07802 not being an ohmic electrical conductor
• CPC Class Codes: H01L 2924/07811 Extrinsic, i.e. with electrical conductive fillers
• CPC Class Codes: H01L 2924/12032 Schottky diode
• CPC Class Codes: H01L 2924/12041 LED
• CPC Class Codes: H01L 2924/12042 LASER
• CPC Class Codes: H01L 2924/12043 Photo diode
• CPC Class Codes: H01L 2924/181 Encapsulation
• CPC Class Codes: H01L 2924/1815 Shape
• CPC Class Codes: H01L 2924/18161 of a flip chip
• CPC Class Codes: H01L 2933/0033 relating to semiconductor body packages
• CPC Class Codes: H01L 2933/0083 Periodic patterns for optical field-shaping in or on the semiconductor body or semiconductor body package, e.g. photonic bandgap structures
• CPC Class Codes: H01L 31/055 where light is absorbed and re-emitted at a different wavelength by the optical element directly associated or integrated with the PV cell, e.g. by using luminescent material, fluorescent concentrators or up-conversion arrangements
• CPC Class Codes: H01L 33/486 adapted for surface mounting
• CPC Class Codes: H01L 33/502 : Wavelength conversion materials
• CPC Class Codes: H01L 33/505 : characterised by the shape, e.g. plate or foil
• CPC Class Codes: H01L 33/54 : having a particular shape
• CPC Class Codes: H01L 33/56 : Materials, e.g. epoxy or silicone resin
• CPC Class Codes: H01L 33/58 : Optical field-shaping elements
• CPC Class Codes: H01L 33/60 : Reflective elements
• 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
• CPC Class Codes: Y02E 10/52 : PV systems with concentrators

Abstract

In accordance with certain embodiments, semiconductor dies are embedded within polymeric binder to form, e.g., freestanding white light-emitting dies and/or composite wafers containing multiple light-emitting dies embedded in a single volume of binder.

Claims

1. A method of forming a composite wafer comprising a plurality of discrete semiconductor dies suspended in a cured polymeric binder, the method comprising:

disposing the plurality of discrete semiconductor dies on a mold substrate, each semiconductor die (i) having two spaced-apart contacts adjacent the mold substrate, (ii) being spaced away from one or more neighboring semiconductor dies, and (iii) being a bare-die light-emitting element;

coating the plurality of semiconductor dies with a polymeric binder,

curing the polymeric binder to form the composite wafer; and

forming one or more electrically conductive layers over at least a portion of a first face of the polymeric binder and at least a portion of each of the two spaced-apart contacts of each semiconductor die,

wherein (i) the polymeric binder is transparent to a wavelength of light emitted by the semiconductor dies, (ii) the polymeric binder contains a wavelength-conversion material for absorption of at least a portion of light emitted from the semiconductor dies and emission of converted light having a different wavelength, converted light and unconverted light emitted by the semiconductor dies combining to form mixed light, and (iii) for each semiconductor die, the two spaced-apart contacts are electrically coupled to the one or more conductive layers.

2. The method of claim 1, wherein forming the one or more electrically conductive layers comprises at least one of evaporation, sputtering, or lamination.

3. The method of claim 1, wherein the one or more electrically conductive layers comprise a plurality of electrically conductive layers, each of the two spaced-apart contacts of a semiconductor die being electrically coupled to a different electrically conductive layer.

4. The method of claim 1, wherein the one or more electrically conductive layers comprise a plurality of electrically conductive layers, each of the electrically conductive layers being electrically coupled to only one contact of a semiconductor die.

5. The method of claim 1, wherein the one or more electrically conductive layers comprise a plurality of electrically conductive layers, each of which is electrically coupled to at least one of the two spaced-apart contacts of a semiconductor die.

6. The method of claim 5, further comprising removing a portion of the one or more electrically conductive layers to form the plurality of electrically conductive layers.

7. The method of claim 6, wherein, for at least one semiconductor die, the two spaced-apart contacts are not electrically connected by an electrically conductive layer.

8. The method of claim 1, wherein forming the one or more electrically conductive layers comprises forming the one or more electrically conductive layers over at least a portion of the mold substrate before disposing the plurality of discrete semiconductor dies on the mold substrate.

9. The method of claim 8, wherein forming the one or more electrically conductive layers comprises at least one of evaporation, sputtering, or lamination.

10. The method of claim 8, wherein the one or more electrically conductive layers comprise a plurality of electrically conductive layers.

11. The method of claim 8, wherein forming the one or more electrically conductive layers comprises forming an electrically conductive layer and removing at least a portion thereof to form a plurality of electrically conductive layers.

12. The method of claim 1, wherein the one or more electrically conductive layers have a reflectance of at least 50% to a wavelength of light emitted by at least one of the semiconductor dies or the wavelength-conversion material.

13. The method of claim 1, wherein the one or more electrically conductive layers have a reflectance of at least 90% to a wavelength of light emitted by at least one of the semiconductor dies or the wavelength-conversion material.

14. The method of claim 1, further comprising separating the composite wafer into a plurality of discrete portions each comprising at least one semiconductor die coated with cured polymeric binder and at least two electrically conductive layers, each electrically conductive layer electrically coupled to at least one of the two spaced-apart contacts.

15. The method of claim 14, wherein, after separation, the two spaced apart contacts are not electrically coupled by the at least two electrically conductive layers.

16. The method of claim 14, wherein after separation a volume of polymeric binder surrounding each semiconductor die is substantially equal.

17. The method of claim 14, wherein each discrete portion of the composite wafer contains only one semiconductor die.

18. The method of claim 14, wherein each discrete portion of the composite wafer is a rectangular solid having approximately 90°

corners between adjacent faces thereof.

19. The method of claim 14, further comprising electrically coupling an electrically conductive layer of one of the discrete portions of the composite wafer to a conductive trace on a substrate.

20. The method of claim 19, wherein the electrically conductive layer is electrically coupled to the conductive trace with at least one of a conductive adhesive, anisotropic conductive adhesive, or solder.

21. The method of claim 19, further comprising electrically connecting the at least one semiconductor die of the discrete portion of the composite wafer to circuitry for powering the at least one semiconductor die.

22. The method of claim 14, further comprising, after separating the composite wafer into the plurality of discrete portions, removing additional material from each of the discrete portions, whereby each discrete portion has a desired shape thereafter.

23. The method of claim 1, further comprising separating the composite wafer from the mold substrate.

24. The method of claim 1, further comprising:

disposing a second substrate in contact with the plurality of semiconductor dies coated with polymeric binder; and

removing the mold substrate from the plurality of semiconductor dies coated with polymeric binder, the plurality of semiconductor dies coated with polymeric binder remaining attached to the second substrate.

25. The method of claim 24, further comprising separating the composite wafer from the second substrate.

26. The method of claim 1, wherein, before curing the polymeric binder, the contacts of the plurality of semiconductor dies are at least partially embedded within the mold substrate.

27. The method of claim 1, wherein, after curing the polymeric binder, at least a portion of each of the contacts of the plurality of semiconductor dies protrudes from the cured binder.

28. The method of claim 1, wherein the polymeric binder comprises at least one of silicone or epoxy.

29. The method of claim 1, wherein coating the plurality of semiconductor dies with the polymeric binder comprises:

dispensing the polymeric binder into a mold; and

disposing the mold substrate over the mold, whereby the plurality of semiconductor dies are suspended within the polymeric binder.

30. The method of claim 29, wherein curing the polymeric binder comprises:

at least partially curing the polymeric binder; and

thereafter, removing the mold substrate from the mold.

31. The method of claim 30, wherein (i) the mold comprises a plurality of discrete compartments in which the polymeric binder is disposed, and (ii) one or more semiconductor dies are suspended within or above each compartment prior to curing the polymeric binder.

32. The method of claim 31, wherein each compartment imparts a complementary shape to a portion of the polymeric binder, the complementary shapes being substantially identical to each other.

33. The method of claim 1, wherein coating the plurality of semiconductor dies with the polymeric binder comprises dispensing the polymeric binder over the mold substrate, the polymeric binder being contained over the mold substrate by one or more barriers extending above a surface of the mold substrate.

34. The method of claim 33, wherein curing the polymeric binder comprises:

at least partially curing the polymeric binder; and

thereafter, removing the mold substrate from the plurality of semiconductor dies.

35. The method of claim 33, further comprising disposing a mold cover over and in contact with at least a portion of the polymeric binder.

36. The method of claim 35, wherein (i) the mold cover comprises a plurality of discrete compartments and (ii) one or more semiconductor dies are suspended within or beneath each compartment prior to curing the polymeric binder.

37. The method of claim 36, wherein each compartment imparts a complementary shape to a portion of the polymeric binder, the complementary shapes being substantially identical to each other.

38. The method of claim 1, wherein the mixed light comprises substantially white light having a correlated color temperature in the range of 2000 K to 10,000 K.

39. The method of claim 38, wherein a variation in the color temperature of the substantially white light emitted when each semiconductor die is individually energized is less than four MacAdam ellipses across the composite wafer.

40. The method of claim 38, wherein a variation in the color temperature of the substantially white light emitted when each semiconductor die is individually energized is less than two MacAdam ellipses across the composite wafer.

41. The method of claim 38, wherein a variation in the color temperature of the substantially white light emitted when each semiconductor die is individually energized is less than 500 K across the composite wafer.

42. The method of claim 1, wherein the composite wafer has a first surface and a second surface opposite the first surface, and the variation in thickness between the first and second surfaces is less than 10%.

43. The method of claim 1, wherein a spacing between neighboring semiconductor dies is substantially constant across the composite wafer.

44. The method of claim 1, wherein a thickness of the polymeric binder above each of the semiconductor dies is the same to within 5%.

45. The method of claim 1, wherein the polymeric binder comprises a plurality of discrete regions at least one of which comprises the polymeric binder without the wavelength-conversion material.

46. The method of claim 1, wherein (i) at least one semiconductor die comprises one or more active layers over a substrate, and (ii) the substrate is partially or completely removed before coating with the polymeric binder.

47. The method of claim 46, wherein the substrate of the at least one semiconductor die is partially or completely removed after disposing the at least one semiconductor die on the mold substrate.

48. The method of claim 1, further comprising associating an optical element with one or more of the semiconductor dies.

49. The method of claim 1, further comprising disposing an array of optical elements on the binder prior to curing.

50. The method of claim 49, wherein curing the binder adheres the array of optical elements to the binder.

51. The method of claim 49, further comprising separating the composite wafer into discrete portions each comprising at least one optical element.

52. The method of claim 1, further comprising separating the composite wafer from the mold substrate before forming the one or more electrically conductive layers.

53. The method of claim 52, further comprising:

disposing a second substrate in contact with the plurality of semiconductor dies coated with polymeric binder; and

before forming the one or more electrically conductive layers, removing the mold substrate from the plurality of semiconductor dies coated with polymeric binder, the plurality of semiconductor dies coated with polymeric binder remaining attached to the second substrate.

54. The method of claim 53, further comprising separating the composite wafer from the second substrate.

55. The method of claim 30, further comprising separating the composite wafer from the mold substrate before forming the one or more electrically conductive layers.

56. The method of claim 34, wherein the mold substrate is removed from the plurality of semiconductor dies before the one or more electrically conductive layers are formed.