Wafer level phosphor coating method and devices fabricated utilizing method

• US 9,024,349 B2
• Filed: 01/22/2007
• Issued: 05/05/2015
• Est. Priority Date: 01/22/2007
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Chitnis, Ashay, Ibbetson, James, Chakraborty, Arpan, Tarsa, Eric J., Keller, Bernd, Seruto, James, Fu, Yankun
• Primary Examiner(s): Rizkallah, Kimberly
• Assistant Examiner(s): Ligai, Maria
• Application Number:
  US11/656,759
• Publication Number:
  US 20080173884A1
• Time in Patent Office: 3,025 Days
• Field of Search: 257/88, 257/98, 257/E25.032, 257E33001-E33043, 257E33044-E33077, 257/81, 257/82, 257/99, 257/100, 438/26, 438/28, 438/29
• US Class Current: 257/99
• CPC Class Codes: H01L 23/3114 the device being a chip scale package, e.g. CSP
• 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 2933/0041 relating to wavelength conversion elements
• CPC Class Codes: H01L 33/38 with a particular shape
• 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 33/501 characterised by the materials, e.g. binder
• CPC Class Codes: H01L 33/507 the elements being in intimate contact with parts other than the semiconductor body or integrated with parts other than the semiconductor body
• 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 33/62 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 wafer, comprising:

a plurality of vertical geometry LEDs formed at the wafer level on a substrate wafer, each LED in said plurality of LEDs comprising a plurality of semiconductor layers;

a plurality of pedestals, each of which is in electrical contact with one of said LEDs, said plurality of pedestals disposed such that at least two pedestals are on one side of each of said LEDs; and

a coating at least partially covering said LEDs and directly on the top surface of said LEDs, at least some of said pedestals extending through and to the surface of said coating with the top surface of said pedestals exposed at the same level as the top surface of said coating, said coating having substantially the same index of refraction from the top surface of said semiconductor layers to the top surface of said coating;

wherein said coating comprises a phosphor loaded binder.

2. The LED chip wafer of claim 1, wherein said substrate wafer comprises a growth substrate wafer.

3. The LED chip wafer of claim 2, wherein said substrate comprises a phosphor loaded binder layer.

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

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

6. The LED chip wafer of claim 1, wherein said coating has a total thickness variation of <

50% of the average coating thickness.

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

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

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

10. The LED chip wafer of claim 1, wherein said binder comprises one of the materials from the group consisting of silicone, epoxy, glass, spin-on glass, BCB, polymides and polymers.

11. The LED chip wafer of claim 1, wherein said phosphor comprises YAG:

Ce.

12. The LED chip wafer of claim 1, wherein said pedestals comprise one or more stud bumps.

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

14. The LED chip wafer of claim 1, wherein said substrate wafer comprises a carrier substrate.

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

16. The LED chip wafer of claim 1, a metal pad on the surface of said coating interconnecting at least some of said exposed pedestals to form an LED array.

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

18. The LED chip wafer of claim 1, wherein said LEDs comprise at least a portion of a growth substrate.

19. The LED chip wafer of claim 1, wherein said LEDs are provided on a substrate, further comprising trenches in said substrate and a second coating filling said trenches.

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

21. The LED chip wafer of claim 1, further comprising the step of forming a second coating around at least part of said LEDs.

22. The LED chip wafer of claim 21, wherein said second coating has a different composition than said coating.

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

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

a plurality of vertical geometry LEDs formed at the wafer level on a substrate wafer, each LED in said plurality of LEDs comprising a plurality of semiconductor layers;

a plurality of pedestals, each of which is in electrical contact with one of said LEDs, said plurality of pedestals disposed such that at least two pedestals are on one side of each of said LEDs; and

a coating at least partially covering said LEDs and directly on the top surface of said LEDs, at least some of said pedestals extending through and to the surface of said coating with the top surface of said pedestals exposed at the same level as the top surface of said coating, said coating having substantially the same index of refraction from the top surface of said semiconductor layers to the top surface of said coating;

wherein said coating comprises scattering particles.