Flip-chip phosphor coating method and devices fabricated utilizing method

• US 8,878,219 B2
• Filed: 01/11/2008
• Issued: 11/04/2014
• Est. Priority Date: 01/11/2008
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Chitnis, Ashay, Ibbetson, James, Keller, Bernd
• Primary Examiner(s): Trinh, Hoa B
• Application Number:
  US12/008,477
• Publication Number:
  US 20090179207A1
• Time in Patent Office: 2,489 Days
• Field of Search: 257/79, 257 81- 82, 257/84, 257/86, 257/94, 257/E51.018, 257/706
• US Class Current: 257/99
• CPC Class Codes: H01L 2224/13 of an individual bump connector
• CPC Class Codes: H01L 27/15 including semiconductor components having potential barriers, specially adapted for light emission
• CPC Class Codes: H01L 2933/0041 relating to wavelength conversion elements
• CPC Class Codes: H01L 2933/0066 relating to arrangements for conducting electric current to or from the semiconductor body
• CPC Class Codes: H01L 33/08 with a plurality of light emitting regions, e.g. laterally discontinuous light emitting layer or photoluminescent region integrated within the semiconductor body H01L27/15 takes precedence
• CPC Class Codes: H01L 33/10 with a light reflecting structure, e.g. semiconductor Bragg reflector
• CPC Class Codes: H01L 33/44 characterised by the coatings, e.g. passivation layer or anti-reflective coating
• 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 33/62 Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls
• CPC Class Codes: H01L 33/64 Heat extraction or cooling elements

Abstract

Methods for fabricating light emitting diode (LED) chips one of which comprises flip-chip mounting a plurality of LEDs on a surface of a submount wafer and forming a coating over said LEDs. The coating comprising a conversion material at least partially covering the LEDs. The coating is planarized to the desired thickness with the coating being continuous and unobstructed on the top surface of the LEDs. The LEDs chips are then singulated from the submount wafer. An LED chip comprising a lateral geometry LED having first and second contacts, with the LED flip-chip mounted to a submount by a conductive bonding material. A phosphor loaded binder coats and at least partially covers the LED. The binder provides a substantially continuous and unobstructed coating over the LED. The phosphor within the coating absorbs and converts the wavelength of at least some of the LED light with the coating planarized to achieve the desired emission color point of the LED chip.

Claims

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

a submount wafer;

a plurality of LEDs having contacts accessible at one side and mounted to said submount wafer so that said contacts are accessible at said submount wafer;

a phosphor loaded binder coating at least partially covering said LEDs and having substantially the same thickness over each of said LEDs and being continuous and unobstructed over each of said LEDs such that the light emitted from each of said LEDs is substantially uniform, at least some of the light emitted from said LEDs passing through said coating where at least some of said LED light is converted by the phosphor in said coating;

conductive vias through said submount wafer, wherein each of said conductive vias is in electrical contact with one of said contacts; and

a dielectric material insulating said conductive vias from said submount wafer.

2. The LED chip wafer of claim 1, wherein at least some of said plurality of LEDs has lateral geometry.

3. The LED chip wafer of claim 2, wherein said at least some of said plurality of LED comprises oppositely doped layers with a mesa formed on one of said oppositely doped layers.

4. The LED chip wafer of claim 3, wherein said contacts comprise first and second contacts, the first being on said mesa of one of said oppositely doped layers and the second being on the other of said oppositely doped layers.

5. The LED chip wafer of claim 1, wherein at least some of said LEDs have a textured surface that comprises texture features larger than 10% of the thickness of said LED.

6. The LED chip wafer of claim 1, wherein said submount wafer is capable of being separated into LED chips.

7. The LED chip wafer of claim 1, wherein said coating has a uniform thickness above said LEDs.

8. The LED chip wafer of claim 1, wherein said coating has a textured surface.

9. The LED chip wafer of claim 1, wherein said coating comprises multiple phosphors.

10. The LED chip wafer of claim 1, wherein said coating comprises scattering particles.

11. The LED chip wafer of claim 1, wherein said LEDs are made of materials from the Group-III nitride material system.

12. The LED chip wafer of claim 1, wherein said submount wafer comprises a lead frame.

13. The LED chip wafer of claim 1, wherein said submount wafer comprises a temporary carrier.

14. The LED chip wafer of claim 1, wherein said LEDs are interconnected in an LED array.

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

16. The LED chip wafer of claim 1, wherein said coating comprises multiple layers with different compositions.

17. The LED chip wafer of claim 1, capable of emitting white light from said LEDs and coating.

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

a lateral geometry LED comprising first and second contacts, said LED flip-chip mounted to a submount by a conductive bonding material, an electrical signal applied to said LED through said submount;

a uniform phosphor loaded binder coating on and covering the top surface of said LED such that light emitted from said LED is substantially uniform, said phosphor within said coating absorbing and converting the wavelength of at least some of said LED light, said coating planarized to achieve the desired emission color point of said LED chip,

wherein said first and second contacts are accessible from a surface opposite said top surface;

wherein said submount comprises electrically conductive vias electrically coupled to said contacts; and

a dielectric material insulating said conductive vias from said submount.

19. The LED chip of claim 18, wherein said phosphor coating is continuous over the top surface of said LED and has a substantially uniform thickness.

20. The LED chip of claim 18, wherein said LED chip is adapted to emit a white light combination of LED light and light from said phosphor.

21. The LED chip of claim 18, wherein said conductive vias permit an electrical signal to be applied to said LED through said submount.

22. The LED chip of claim 18, wherein said submount comprises surface mount leads.

23. The LED chip of claim 18, wherein said submount comprises a lead frame.

24. The LED chip of claim 18, wherein said submount comprises a temporary carrier.

25. A light emitting diode (LED) package comprising:

an LED chip comprising an LED flip chip mounted on a submount, said submount comprising surface mount leads and conductive vias through said submount and in electrical contact with said LED, said submount comprising a dielectric material insulating said conductive vias from said submount, said LED chip further comprising a uniform and continuous phosphor loaded binder coating on and covering at least all of the top surface of said LED such that light emitted from said LED is substantially uniform, said phosphor within said coating absorbing and converting the wavelength of at least some of said LED light, said coating planarized to achieve the desired emission color of said LED chip; and

a second submount having a plurality of package leads, said LED chip mounted to said second submount in electrical connection with at least one of said package leads.

26. The package of claim 25, further comprising an encapsulation at least partially surrounding said LED.

27. The package of claim 25, further comprising secondary optics directly on said LED.

28. The package of claim 25, wherein said LED chip is adapted to emit white light.