Close loop electrophoretic deposition of semiconductor devices

• US 20070158668A1
• Filed: 06/21/2006
• Published: 07/12/2007
• Est. Priority Date: 08/25/2005
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Keller, Bernd, Leung, Michael, Tarsa, Eric, Youmans, Mark, Underwood, Robert
• Granted Patent: US 8,563,339 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: C25D 13/02 with inorganic material
• CPC Class Codes: C25D 13/12 characterised by the article coated
• CPC Class Codes: C25D 13/22 Servicing or operating apparatus or multistep processes
• CPC Class Codes: C25D 15/00 Electrolytic or electrophoretic production of coatings containing embedded materials, e.g. particles, whiskers, wires
• CPC Class Codes: C25D 17/02 Tanks; Installations therefor
• CPC Class Codes: C25D 21/00 Processes for servicing or operating cells for electrolytic coating
• CPC Class Codes: C25D 5/003 Electroplating using gases, e.g. pressure influence
• CPC Class Codes: C25D 7/123 Semiconductors first coated with a seed layer or a conductive layer
• CPC Class Codes: H01L 2933/0041 relating to wavelength conversion elements

Abstract

One close loop system and method for electrophoretic deposition (EPD) of phosphor material on light emitting diodes (LEDs). The system comprises a deposition chamber sealed from ambient air. A mixture of phosphor material and solution is provided to the chamber with the mixture also being sealed from ambient air. A carrier holds a batch of LEDs in the chamber with the mixture contacting the areas of the LEDs for phosphor deposition. A voltage supply applies a voltage to the LEDs and the mixture to cause the phosphor material to deposit on the LEDs at the mixture contacting areas.

Claims

1. A system for depositing a material on a semiconductor device, comprising:

a chamber holding a semiconductor device, said chamber sealed from ambient air;

a liquid mixture of deposition material in said chamber, said mixture being sealed from ambient air; and

a voltage supply to apply a voltage to said semiconductor device and said mixture to cause said material to deposit on said semiconductor device.

2. The system of claim 1, wherein said semiconductor device comprises a light emitting diode (LED).

3. The system of claim 1, wherein said deposition material comprises one or more phosphors.

4. The system of claim 1, wherein said deposition material comprises light scattering particles.

5. The system of claim 1, further comprising a first bath sealed from ambient air and holding said mixture, said first bath connected to said chamber to supply said mixture to said chamber and sealing said mixture from ambient air.

6. The system of claim 5, wherein said first bath further comprises a stirrer to stir said mixture.

7. The system of claim 5, wherein said chamber further comprises an outlet, said mixture exiting said chamber through said outlet after being supplied to said outlet, and returned to said first bath while sealing said mixture from ambient air.

8. The system of claim 5, further comprising a second bath sealed from ambient air and holding a rinsing liquid, said second bath connected to said chamber to supply said rinsing liquid to said chamber while sealing said rinsing liquid from ambient air.

9. The system of claim 8, wherein said chamber further comprises an outlet, said rinsing liquid exiting said chamber through said outlet and returned to said first bath while sealing said rinsing liquid from ambient air.

10. The system of claim 9, further comprising a filtering system for filtering said rinsing liquid after it is supplied to said chamber.

11. The system of claim 1, further comprising a purging gas source sealed from ambient air, said purging gas source connected to said chamber to supply said gas to said chamber while sealing said gas from ambient air.

12. The system of claim 1, further comprising a vent for exhausting said gas after being supplied to said chamber.

13. A method for depositing a material on a semiconductor device, comprising:

providing a chamber for holding a semiconductor device, said chamber sealed from ambient air;

providing a mixture of material and solution, said mixture placed in said chamber while being sealed from ambient air; and

applying a voltage to said semiconductor device and said mixture to cause said material to deposit on said semiconductor device.

14. The method of claim 13, wherein said semiconductor device comprises a light emitting diode (LED).

15. The method of claim 13, wherein said material comprises at least one layer of one or more phosphors.

16. The method of claim 13, wherein said material comprises at least one layer of one or more substances having light scattering particles.

17. The method of claim 13, wherein said material has at least one layer of one or more phosphors and at least one layer of one or more substances having light scattering particles.

18. The method of claim 13, further comprising stirring said mixture prior to placing it in said chamber.

19. The method of claim 13, further comprising returning said mixture to said first bath without exposing said mixture to ambient air.

20. The method of claim 13, further comprising providing a rinsing liquid without exposing without exposing said rinsing liquid to ambient air.

21. The method of claim 20, further comprising allowing said rinsing liquid to exit from said chamber.

22. The method of claim 21, wherein said rinsing liquid exits said chamber without exposure to ambient air.

23. The method of claim 21, further comprising filtering said rinsing liquid after exiting said chamber.

24. The method of claim 13, further comprising providing a gas to said chamber to purge moisture and contaminants from said chamber.

25. The method of claim 24, further comprising venting said gas from said chamber.

26. A light emitting diode, comprising:

active semiconductor layers emitting light in response to an electric bias;

a layer of conversion material covering at least a portion of said active semiconductor layers, said conversion material converting at least some of said light emitting by said semiconductor layers, said conversion material deposited on said active layers using close loop electrophoretic deposition (EPD).

27. The LED of claim 26, wherein said conversion material comprises one or more phosphors.

28. The LED of claim 27, wherein said conversion material contains light scattering particles.

29. The LED of claim 26, further comprising a layer of material containing light scattering particles.

30. A system for depositing a material on a plurality of semiconductor devices, comprising:

a deposition chamber sealed from ambient air;

a mixture of deposition material and solution supplied to said chamber, said mixture being sealed from ambient air;

a carrier for holding a batch of semiconductor devices in said chamber with said mixture contacting the areas of said semiconductor devices for material deposition; and

a voltage supply to apply a voltage to said semiconductor devices and said mixture to cause said material to deposit on said semiconductor devices at said mixture contacting areas.

31. The system of claim 30, further comprising:

a mask, said mask limiting phosphor deposition to specific areas on said semiconductor devices.

32. The system of claim 31, wherein said mask further comprises:

a top plate having holes, said top plate mounted to said bottom plate with each of said holes aligned with a corresponding projection, each of said semiconductor devices contacting a respective one of said projections and arranged in a respective one of said holes, said holes defining said mixture contacting area, said cathode electric signal transmitted to said semiconductor devices through said contacts.

33. The system of claim 31, wherein said mask is patterned onto said semiconductor devices.

34. The system of claim 30, wherein said batch of semiconductor devices comprises light emitting diodes (LEDs).

35. The system of claim 34, wherein said voltage supply comprises an anode and cathode, said anode applying an electrical signal to said mixture and said cathode applying an electrical signal to said LEDs.

36. The system of claim 34, wherein said carrier comprises a plurality of holes, each of said LEDs arranged in a respective one of said holes with said holes defining said mixture contacting area.

37. The system of claim 35, wherein said carrier comprises a plurality of contacts, each of which makes electrical contact with a respective one of said LEDs, said cathode electric signal transmitted to said LEDs through said contacts.

38. The system of claim 34, wherein said carrier further comprises:

a bottom plate having projections to make electrical contact with said LEDs.

39. The system of claim 32, wherein said projections comprise posts or springs.

40. The system of claim 32, wherein said carrier further comprises a seal around each of said holes to confine said mixture to said mixture contacting area.

41. The system of claim 36, wherein each of said LEDs is mounted to a respective one of a plurality of submounts, said LEDs held in its respective one of said holes by its submount.

42. The system of claim 32, further comprising a field plate on said top plate around said holes, said field plate reducing the electric field edge effect between said anode and cathode.

43. The system of claim 30, wherein said carrier is arranged to hold more than one batch of semiconductor devices.