Methods of coating semiconductor light emitting elements by evaporating solvent from a suspension

• US 20070224716A1
• Filed: 05/01/2007
• Published: 09/27/2007
• Est. Priority Date: 09/21/2004
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Negley, Gerald, Leung, Michael
• Granted Patent: US 7,569,407 B2
• Time in Patent Office: Days
• US Class Current: 438/29
• CPC Class Codes: H01L 2933/0041 relating to wavelength conversion elements
• CPC Class Codes: H01L 33/501 characterised by the materials, e.g. binder

Abstract

Semiconductor light emitting devices are fabricated by placing a suspension including phosphor particles suspended in solvent on at least a portion of a light emitting surface of a semiconductor light emitting element, and evaporating at least some of the solvent to cause the phosphor particles to deposit on at least a portion of the light emitting surface. A coating including phosphor particles is thereby formed on at least a portion of the light emitting surface. Particles other than phosphor also may be coated and solutions wherein particles are dissolved in solvent also may be used.

Claims

1. A method of fabricating a semiconductor light emitting device comprising:

placing a suspension comprising particles suspended in solvent on at least a portion of a light emitting surface of a semiconductor light emitting element;

confining the suspension for controlled evaporation on at least a portion of the light emitting surface; and

evaporating at least some of the solvent to cause the particles to deposit on the at least a portion of the light emitting surface and form a coating thereon comprising the particles.

2. A method according to claim 1, wherein said particles comprise phosphor particles.

3. A method according to claim 1 wherein said suspension is confined in a cavity on the light emitting surface, and wherein placing comprises placing the suspension comprising phosphor particles suspended in solvent in the cavity.

4. A method according to claim 1 further comprising:

agitating the suspension comprising phosphor particles suspended in solvent while performing the placing and/or the evaporating.

5. A method according to claim 1 wherein evaporating comprises evaporating at least some of the solvent to cause the particles to uniformly deposit on the at least a portion of the light emitting surface and form a uniform coating thereon comprising the particles.

6. A method according to claim 1 wherein evaporating comprises evaporating substantially all of the solvent to cause the phosphor particles to deposit on the at least a portion of the light emitting surface and form a coating thereon comprising the phosphor particles.

7. A method according to claim 1:

wherein placing comprises placing a suspension comprising particles suspended in solvent and binder on at least a portion of a light emitting surface of a semiconductor light emitting element; and

wherein evaporating comprises evaporating at least some of the solvent to cause the particles and the binder to deposit on the at least a portion of the light emitting surface and form a coating thereon comprising the particles and the binder.

8. A method according to claim 1:

wherein placing comprises placing a suspension comprising phosphor particles and light scattering particles suspended in solvent on at least a portion of a light emitting surface of a semiconductor light emitting surface; and

wherein evaporating comprises evaporating at least some of the solvent to cause the phosphor particles and the light scattering particles to deposit on the at least a portion of the light emitting element and form a coating thereon comprising the phosphor particles and the light scattering particles.

9. A method according to claim 3 wherein placing is preceded by:

providing a mounting substrate for a semiconductor light emitting device including the cavity therein; and

mounting the semiconductor light emitting element in the cavity.

10. A method according to claim 3 wherein the cavity includes a cavity floor, wherein the light emitting element is on the cavity floor, wherein the light emitting surface protrudes away from the cavity floor and wherein evaporating comprises:

evaporating at least some of the solvent to cause the phosphor particles to deposit on at least a portion of the light emitting surface that protrudes away from the cavity floor and on at least a portion of the cavity floor and form a coating thereon comprising the phosphor particles.

11. A method according to claim 3 wherein the cavity includes a cavity floor, wherein the light emitting element is on the cavity floor, wherein the light emitting surface protrudes away from the cavity floor and wherein evaporating comprises:

evaporating at least some of the solvent to cause the phosphor particles to uniformly deposit on at least a portion of the light emitting surface that protrudes away from the cavity floor and on at least a portion of the cavity floor and thereby form a coating thereon comprising the phosphor particles.

12. A method according to claim 1 wherein evaporating comprises:

evaporating substantially all of the solvent to cause the phosphor particles to uniformly deposit on all the light emitting surface and form a coating thereon comprising the phosphor particles.

13. A method according to claim 1 wherein the solvent comprises Methyl Ethyl Ketone (MEK), alcohol, toluene and/or Amyl Acetate.

14. A method according to claim 7 wherein the binder comprises cellulose.

15. A method according to claim 8 wherein the light scattering particles comprise SiO₂ particles.

16. A method according to claim 1 wherein the light emitting surface includes a face and a sidewall that extends from the face, and wherein evaporating comprises evaporating substantially all of the solvent to cause the phosphor particles to uniformly deposit on all the light emitting surface, including on all the face and on all the sidewall and form a coating thereon comprising the phosphor particles.

17. A method according to claim 3 wherein the cavity includes a cavity floor, wherein the light emitting surface includes a face remote from the cavity floor and a sidewall that extends from the face to the cavity floor, and wherein evaporating comprises evaporating substantially all of the solvent to cause the phosphor particles to uniformly deposit on all the light emitting surface, including on all the face and on all the sidewall and form a coating thereon comprising the phosphor particles.

18. A method according to claim 1 wherein the phosphor is configured to convert at least some light that is emitted from the light emitting surface such that light that emerges from the semiconductor light emitting device appears as white light.

19. A solid state emitter chip comprising:

a solid state emitter;

a coating over said solid state emitter, wherein said coating is formed by placing a suspension comprising particles suspended in a solvent on a least a portion of the light emitting surface of said solid state emitter and where at least some of the solvent is evaporated to cause the particles to deposit on and form said coating on said at least a portion of the light emitting surface.

20. The emitter chip of claim 19, wherein said solid state emitter comprises a light emitting diode (LED).

21. The emitter chip of claim 19, wherein said suspension is confined for controlled evaporation on at least a portion of said light emitting surface.

22. The emitter chip of claim 19, wherein said particles comprise phosphor particles.

23. The emitter chip of claim 19, said coating further comprising a binder

24. The emitter chip of claim 23, wherein said binder is in said suspension with said particles, wherein evaporating said at least some solvent causes the particles and binder to deposit on and form said coating.

25. The emitter chip of claim 24, wherein said binder comprises cellulose.

26. The emitter chip of claim 19, wherein said coating comprises light scattering particles.

27. The emitter chip of claim 19, further comprising a mounting substrate including a cavity therein, said emitter within said cavity.

28. The emitter chip of claim 20, wherein said phosphor is configured to convert at least some light that is emitted from said light emitting surface such that light that is emitted from said chip appears as white light.

29. The emitter chip of claim 19, wherein said coating has a substantially uniform thickness.

30. The emitter chip of claim 19, wherein said coating has a substantially uniform particle concentration.