Producing self-aligned and self-exposed photoresist patterns on light emitting devices

• US 20030181122A1
• Filed: 03/22/2002
• Published: 09/25/2003
• Est. Priority Date: 03/22/2002
• Status: Active Grant

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Lumileds Lighting US LLC (Apollo Global Management, Inc.)
• Inventors: Steigerwald, Daniel A., Snyder, Wayne L., Collins, William D. III
• Granted Patent: US 6,756,186 B2
• Time in Patent Office: Days
• US Class Current: 445/24
• 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 33/44 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: Y10S 430/146 Laser beam

Abstract

A method of forming a photoresist mask on a light emitting device is disclosed. A portion of the light emitting device is coated with photoresist. A portion of the photoresist is exposed by light impinging on the interface of the light emitting device and the photoresist from inside the light emitting device. The photoresist is developed, removing either the exposed photoresist or the unexposed photoresist. In one embodiment, the photoresist mask may be used to form a phosphor coating. After the photoresist is developed to remove the exposed photoresist, a phosphor layer is deposited overlying the light emitting device. The unexposed portion of photoresist is stripped. In some embodiments, the light exposing the photoresist is produced by electrically biasing the light emitting device, or by shining light into the light emitting device through an aperture or by a focussed laser.

Claims

1. A method comprising:

coating at least a portion of a light emitting device with photoresist;

exposing a portion of the photoresist, wherein the portion of the photoresist is exposed with light impinging on the interface of the light emitting device and the photoresist from inside the light emitting device; and

developing the photoresist, wherein developing removes one of the exposed portion and an unexposed portion of the photoresist.

2. The method of claim 1 further comprising producing light inside the light emitting device by electrically biasing the light emitting device.

3. The method of claim 2 wherein the biasing is accomplished by a plurality of bias pulses.

4. The method of claim 1 further comprising producing light inside the light emitting device by placing the light emitting device near an RF source, wherein the RF source causes the light emitting device to emit light from an active region of the light emitting device.

5. The method of claim 1 further comprising producing light inside the light emitting device by:

placing an aperture over a portion of the light emitting device;

shining light through the aperture.

6. The method of claim 5 wherein the aperture is smaller than a dimension of the light emitting device.

7. The method of claim 5 wherein shining light through the aperture comprises shining a substantially collimated light beam through the aperture.

8. The method of claim 1 further comprising producing light inside the light emitting device by exposure by a focussed laser beam.

9. The method of claim 8 wherein the focussed laser beam is steered to expose a portion of the photoresist coating the light emitting device and a portion of photoresist coating a second light emitting device.

10. The method of claim 1 further comprising producing light inside the light emitting device by exposing the light emitting device to a light source which excites light emission from a layer of the light emitting device.

11. The method of claim 10 wherein the light source comprises a UV light source.

12. The method of claim 1 wherein developing removes the exposed portion of the photoresist, the method further comprising depositing a photoluminescent material in a gap in the photoresist left by developing.

13. The method of claim 1 wherein:

developing removes the unexposed portion of the photoresist; and

the photoresist comprises a photoluminescent material.

14. A method of coating a light emitting device with phosphor, the method comprising:

attaching the light emitting device to a submount;

coating at least a portion of the light emitting device and at least a portion of the submount with photoresist;

producing light impinging on an interface between the light emitting device and the photoresist from inside the light emitting device, wherein the light exposes a portion of the photoresist;

developing the photoresist, wherein the developing removes the exposed portion of photoresist;

depositing a phosphor layer overlying the light emitting device; and

stripping an unexposed portion of the photoresist.

15. The method of claim 14 wherein the light emitting device is a III-nitride device.

16. The method of claim 14 wherein producing light comprises electrically biasing the light emitting device.

17. The method of claim 14 wherein producing light comprises producing enough light exposure to expose a portion of the photoresist overlying the light emitting device and an annulus of photoresist on the submount.

18. The method of claim 14 wherein producing light:

placing an aperture over a portion of the light emitting device;

shining light through the aperture.

19. The method of claim 15 wherein the aperture has a dimension smaller than 100 microns.

20. The method of claim 14 wherein producing light comprises exposing the light emitting device to a light source which excites light emission from an active region of the light emitting device.

21. The method of claim 14 wherein depositing a phosphor layer comprises depositing a phosphor layer by electrophoretic deposition.

22. The method of claim 14 wherein the phosphor layer is deposited in a region where the photoresist has been removed by exposure and development.