LED chips having fluorescent substrates with microholes and methods for fabricating

• US 9,196,799 B2
• Filed: 08/22/2008
• Issued: 11/24/2015
• Est. Priority Date: 01/22/2007
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Chitnis, Ashay, Keller, Bernd
• Primary Examiner(s): Toledo, Fernando L
• Assistant Examiner(s): Newton, Valerie N
• Application Number:
  US12/229,366
• Publication Number:
  US 20090065790A1
• Time in Patent Office: 2,650 Days
• US Class Current: 1/1
• 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 33/38 with a particular shape
• 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 33/62 Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls

Abstract

Methods for fabricating semiconductor devices such as LED chips at the wafer level, and LED chips and LED chip wafers fabricated using the methods. An LED chip wafer according to the present invention comprises a plurality of LEDs on a wafer and a plurality of pedestals, each of which is on one of the LEDs. A fluorescent substrate or preform (“preform”) is provided covering at least some of the LEDs, the preform comprising holes with the pedestals arranged within the holes. During operation of the covered ones of said LEDs at least some light from the LEDs passes through the preform and is converted. LED chips are provided that are singulated from this LED chip wafer. One embodiment of a method for fabricating LED chips from a wafer comprises depositing LED epitaxial layers on an LED growth wafer to form a plurality of LEDs on the growth wafer. Pedestals are formed on the LEDs and a fluorescent preform is formed with holes. The fluorescent preform is bonded over at least some of the plurality of LEDs so that at least some light from the covered ones of said LEDs passes through the preform and is converted. The pedestals are arranged in the holes so that an electrical signal is applied to the LEDs through the pedestals.

Claims

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

a plurality of LEDs on a wafer, said wafer comprising a first alignment element;

a fluorescent preform covering at least some of said LEDs and contacting at least two of said plurality of LEDs, said preform comprising a second alignment element, said first and second alignment elements cooperating to provide the desired alignment of said preform over said LEDs; and

wherein said wafer is capable of being separated into LED chips.

2. The LED chip wafer of claim 1, wherein said second alignment element comprises a hole and said first alignment element comprises a pedestal.

3. The LED chip wafer of claim 1, wherein said first alignment element comprises a pattern on said wafer and said second alignment element comprises a pattern on said preform.

4. The LED chip wafer of claim 1, wherein said second alignment element comprises a hole and said first alignment element comprises a contact.

5. The LED chip wafer of claim 1, wherein light from the covered ones of said LEDs passes through said preform and is converted.

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

a plurality of LEDs on a wafer;

a plurality of pedestals, each of which is on one of said LEDs;

a fluorescent preform covering at least some of said LEDs and contacting at least two of said plurality of LEDs, said preform comprising holes with said pedestals within said holes such that during operation of the covered ones of said LEDs at least some light from said LEDs passes through said preform and is converted; and

wherein said wafer is capable of being separated into LED chips.

7. The LED chip wafer of claim 6, wherein said LEDs covered by said preform emit a white light comprising light from said LED and converted light from said preform.

8. The LED chip wafer of claim 6, further comprising a plurality of contacts each of which is on one of said LEDs, wherein each of said pedestals is on a contact.

9. The LED chip wafer of claim 6, wherein said preform comprises a phosphor and a binder.

10. The LED chip wafer of claim 9, wherein said preform comprises a phosphor to absorb light from said LED and emit yellow light.

11. The LED chip wafer of claim 9, wherein the concentration of said phosphor is substantially uniform throughout said preform.

12. The LED chip wafer of claim 9, wherein the concentration of said phosphor is non-uniform.

13. The LED chip wafer of claim 6, wherein said preform is textured.

14. The LED chip wafer of claim 6, wherein said preform comprises lenses.

15. The LED chip wafer of claim 6, further comprising covering at least some of said LEDs with a second fluorescent preform.

16. The LED chip wafer of claim 6, further comprising a reflective layer.

17. The LED chip wafer of claim 6, wherein said preform provides mechanical support for at least some of said LEDs.

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

a laterally configured LED;

at least one pedestal in electrical contact with said LED; and

a fluorescent preform bonded to and at least partially covering said LED, said preform comprising at least one hole with said at least one pedestal therein, at least some of the light emitted by said LED passing through and converted by said preform.

19. The LED chip of claim 18, wherein said LED chip emits a combination of light from said LED and from said fluorescent preform.

20. The LED chip of claim 18, wherein said preform provides mechanical support for said LED.

21. The LED chip of claim 18, wherein said preform comprises a phosphor and a binder.

22. The LED chip of claim 21, wherein the concentration of said phosphor is substantially uniform throughout said preform.

23. The LED chip of claim 21, wherein the concentration of said phosphor is non-uniform throughout said preform.

24. The LED chip of claim 18, wherein said preform is textured.

25. The LED chip of claim 18, wherein said preform comprises lenses.

26. The LED chip of claim 18, further comprising a second fluorescent preform covering at least some of said LEDs and converting light from said LEDs.

28. The light emitting diode (LED) chip of claim 18, wherein said at least one pedestal comprises multiple pedestals and said at least one hole comprises multiple holes, said chip configured such that respective ones of said pedestals are in respective ones of said holes.

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

a plurality of LEDs on a wafer, further comprising a plurality of pedestals, at least two of which are on each of said LEDs;

a plurality of contacts, at least two of which are on one of said LEDs; and

a fluorescent preform covering at least some of said LEDs, said preform comprising holes configured to allow electrical contact to said LEDs through said holes, each of said pedestals in one of said holes.