CONTROLLING EDGE EMISSION IN PACKAGE-FREE LED DIE

• US 20100279437A1
• Filed: 05/01/2009
• Published: 11/04/2010
• Est. Priority Date: 05/01/2009
• Status: Abandoned Application

• Current Assignee: Philips Lumileds Lighting Company LLC (Apollo Global Management, Inc.), Koninklijke Philips N.V.
• Original Assignee: Philips Lumileds Lighting Company LLC (Apollo Global Management, Inc.), Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Neff, James G., Bierhuizen, Serge J.
• Application Number:
  US12/433,972
• Publication Number:
  US 20100279437A1
• Time in Patent Office: Days
• US Class Current: 438/14
• 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 33/0095 Post-treatment of devices, e.g. annealing, recrystallisation or short-circuit elimination
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector

Abstract

Light emitting diode (LED) structures are fabricated in wafer scale by mounting singulated LED dies on a carrier wafer or a stretch film, separating the LED dies to create spaces between the LED dies, applying a reflective coating over the LED dies and in the spaces between the LED dies, and separating or breaking the reflective coating in the spaces between the LED dies such that some reflective coating remains on the lateral sides of the LED die. Portions of the reflective coating on the lateral sides of the LED dies may help to control edge emission.

Claims

1. A method for wafer scale fabrication of light emitting diode (LED) structures, comprising:

singulating LED dies in a device wafer;

separating the LED dies to create spaces between the LED dies;

applying a reflective coating in the spaces between the LED dies; and

breaking or separating the reflective coating in the spaces between the LED dies, wherein portions of the reflective coating remain on the lateral sides of the LED dies to control edge emission.

2. The method of claim 1, wherein the reflective coating is a polymer or a resin with reflective particles.

3. The method of claim 2, wherein the reflective coating is silicone, epoxy, or acrylic, and the reflective particles are TiO₂.

4. The method of claim 2, wherein applying the reflective coating over the LED dies and in spaces between the LED dies comprises applying the reflective coating in a sol-gel process or a spin-on process.

5. The method of claim 1, wherein the reflective coating is a thin metal film.

6. The method of claim 5, wherein the reflective coating is Al, Ag, Cr, Au, Ni, V, Pt, Pd, or a combination thereof.

7. The method of claim 5, wherein applying the reflective coating over the LED dies and in the spaces between the LED dies comprises applying the reflective coating by evaporation or sputtering.

8. The method of claim 1, further comprising:

prior to singulating the LED dies, mounting the LED dies in the device wafer to a stretch film;

wherein separating the LED dies comprises transferring the LED dies from the stretch film to a carrier wafer to create the spaces between the LED dies.

9. The method of claim 1, further comprising:

prior to singulating the LED dies, mounting the LED dies in the device wafer to a stretch film;

wherein separating the LED dies comprises expanding the stretch film to laterally separate the LED dies prior to applying the reflective coating over the LED dies and in the spaces between the LED dies.

10. The method of claim 9, wherein the breaking or separating the reflective coating in the spaces between the LED dies comprises:

weakening or breaking the reflective coating in the spaces between the LED dies; and

again expanding the stretch film to further separate the LED dies.

11. The method of claim 9, further comprising:

removing any reflective coating from the top of the LED dies.

12. The method of claim 11, wherein removing the reflective coating from the top of the LED dies comprises a lift-off process, etching, laser ablation, or grit-blasting.

13. The method of claim 11, further comprising:

mounting the LED dies to another stretch film from the other side of the LED dies; and

removing the stretch film from the LED dies.

14. The method of claim 13, further comprising:

testing the LED dies after mounting the LED dies to the other stretch film from the other side of the LED dies.