Emission tuning methods and devices fabricated utilizing methods

• US 8,877,524 B2
• Filed: 03/30/2009
• Issued: 11/04/2014
• Est. Priority Date: 03/31/2008
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Chitnis, Ashay, Edmond, John, Britt, Jeffrey Carl, Keller, Bernd P., Emerson, David Todd, Bergmann, Michael John, Cabalu, Jasper S.
• Primary Examiner(s): CHEN, JACK S J
• Application Number:
  US12/414,457
• Publication Number:
  US 20090261358A1
• Time in Patent Office: 2,045 Days
• Field of Search: 438/14, 438/16, 438/20, 438/22, 438/62
• US Class Current: 438/14
• CPC Class Codes: H01L 2224/13 of an individual bump connector
• CPC Class Codes: H01L 2933/0041 relating to wavelength conversion elements
• CPC Class Codes: H01L 33/0095 Post-treatment of devices, e.g. annealing, recrystallisation or short-circuit elimination
• 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: Y10T 408/47 with work-infeed means

Abstract

A method for fabricating light emitting diode (LED) chips comprising providing a plurality of LEDs, typically on a wafer, and coating the LEDs with a conversion material so that at least some light from the LEDs passes through the conversion material and is converted. The light emission from the LED chips comprises light from the conversion material, typically in combination with LED light. The emission characteristics of at least some of the LED chips is measured and at least some of the conversion material over the LEDs is removed to alter the emission characteristics of the LED chips. The invention is particularly applicable to fabricating LED chips on a wafer where the LED chips have light emission characteristics that are within a range of target emission characteristics. This target range can fall within an emission region on a CIE curve to reduce the need for binning of the LEDs from the wafer. The emission characteristics of the LED chips in the wafer can be tuned to the desired range by micro-machining the conversion material over the LEDs.

Claims

1. A method for fabricating light emitting diode (LED) chips, comprising:

fabricating a plurality of LEDs on a growth wafer;

forming a plurality of LED chips by coating said LEDs on said growth wafer with a conversion material so that at least some light from said LEDs passes through said conversion material and is converted, wherein each of said LED chips comprises an LED and a portion of said conversion material;

measuring the emission characteristics of at least some of said LED chips; and

removing at least some of said conversion material from each of a group of LED chips emitting outside a target range of emission characteristics to alter the emission characteristics of each of said group of LED chips such that each of said LED chips emits within said range of target emission characteristics.

2. The method of claim 1, further comprising generating a surface variation profile of said LEDs.

3. The method of claim 2, further comprising compensating for said surface variation profile when determining how much conversion material is to be removed over said LEDs.

4. The method of claim 1, further comprising determining the amount of conversion material to be removed based on the emission characteristics of said LED chips relative to a range of target emission characteristics.

5. The method of claim 1, wherein the output of said LED chips is altered by said removal of said conversion material to change the emission characteristics of said LED chips such that the emission characteristics of said LED chips are within a range of target emission characteristics.

6. The method of claim 1, further comprising measuring the emission characteristics of at least some of said LEDs a second time following said conversion material removal.

7. The method of claim 6, further comprising removing of at least some of said conversion material a second time over at least some of said LEDs to alter the emission characteristics of said LED chips.

8. The method of claim 1, further comprising generating a map of the emission characteristics of said plurality of LEDs.

9. The method of claim 8, wherein the amount of said conversion material to be removed over the respective ones of said LEDs is determined from said emission characteristic map compared to a target emission characteristic for said LED chips.

10. The method of claim 1, wherein said removal of said conversion material comprises macro-machining.

11. The method of claim 1, wherein said removal of said conversion material comprises micro-machining.

12. The method of claim 1, wherein said removal of said conversion material comprises micro-drilling.

13. The method of claim 1, wherein said removal of said conversion material comprises micro-drilling to a sub-micron depth.

14. The method of claim 13, further comprising measuring a surface variation of said conversion material and compensating for said surface variation when micro-drilling.

15. The method of claim 13, wherein said micro drilling comprises moving said wafer at sub-micron increments in relation to a micro drill.

16. The method of claim 13, where said wafer is moved at sub-micron increments by a nano-stage.

17. The method of claim 1, further comprising generating a map of regions with similar emission characteristics follows said measuring of the emission characteristics, further comprising macro level removal of conversion material over said regions prior to said removal of conversion material over at least some of said LEDs.

18. The method of claim 1, where said measuring of said emission characteristics is performed at the same time as said removal of at least some of said conversion material.

19. The method of claim 1, further comprising planarizing said coating over said LEDs before said measuring of said emission characteristics.

20. A method for fabricating light emitting diode (LED) chips, comprising:

providing a plurality of LEDs on a wafer;

coating said LEDs with a conversion material so that at least some light from said LEDs passes through said conversion material and is converted;

measuring the emission characteristics of at least some of said LED chips;

measuring the surface variations for the conversion material coating on said wafer;

calculating the amount of conversion material that needs to be removed over at least some of said LEDs based on the measured emission characteristics and surface variation profile, to alter the emission characteristics of said LED chips such that said LED chips emit within a range of target emission characteristics; and

removing the calculated amount of conversion material.