Flip-chip bonding of light emitting devices

• US 20050017256A1
• Filed: 08/17/2004
• Published: 01/27/2005
• Est. Priority Date: 07/23/2001
• Status: Active Grant

• Current Assignee: CREE Led Incorporated (Smart Global Holdings Incorporated)
• Original Assignee: CREE Microwave, LLC
• Inventors: Raffeto, Mark, Andrews, Peter S., Negley, Gerald H., Slater, David B. Jr., Edmond, John, Bharathan, Jayesh, Mohammed, Anwar
• Granted Patent: US 7,259,033 B2
• Time in Patent Office: Days
• US Class Current: 257/94
• CPC Class Codes: H01L 2224/04026 Bonding areas specifically adapted for layer connectors
• CPC Class Codes: H01L 2224/26175 Flow barriers
• CPC Class Codes: H01L 2224/291 with a principal constituent of the material being a metal or a metalloid, e.g. boron [B], silicon [Si], germanium [Ge], arsenic [As], antimony [Sb], tellurium [Te] and polonium [Po], and alloys thereof
• CPC Class Codes: H01L 2224/32245 the item being metallic
• CPC Class Codes: H01L 2224/48463 the connecting portion on the bonding area of the semiconductor or solid-state body being a ball bond
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• 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 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/01057 Lanthanum [La]
• CPC Class Codes: H01L 2924/01078 Platinum [Pt]
• CPC Class Codes: H01L 2924/01079 Gold [Au]
• CPC Class Codes: H01L 2924/014 Solder alloys
• CPC Class Codes: H01L 2924/12032 Schottky diode
• CPC Class Codes: H01L 2924/12041 LED
• CPC Class Codes: H01L 33/38 with a particular shape
• 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

Light emitting device die having a mesa configuration on a substrate and an electrode on the mesa are attached to a submount in a flip-chip configuration by forming predefined pattern of conductive die attach material on at least one of the electrode and the submount and mounting the light emitting device die to the submount. The predefined pattern of conductive die attach material is selected so as to prevent the conductive die attach material from contacting regions of having opposite conductivity types when the light emitting device die is mounted to the submount. The predefined pattern of conductive die attach material may provide a volume of die attach material that is less than a volume defined by an area of the electrode and a distance between the electrode and the submount. Light emitting device dies having predefined patterns of conductive die attach material are also provided. Light emitting devices having a gallium nitride based light emitting region on a substrate, such as a silicon carbide substrate, may also be mounted in a flip-chip configuration by mounting an electrode of the gallium nitride based light emitting region to a submount utilizing a B-stage curable die epoxy. Light emitting device dies having a B-stage curable die epoxy are also provided.

Claims

1. A method of mounting a light emitting device having a gallium nitride based light emitting region on a silicon carbide substrate in a flip-chip configuration, the method comprising:

mounting an electrode of the gallium nitride based light emitting region to a submount utilizing a B-stage curable die epoxy.

2. The method of claim 1, wherein the step of mounting comprises:

forming a predefined pattern of the B-stage curable die epoxy on at least one of the electrode and/or the submount; and

attaching the electrode of the gallium nitride based light emitting region and the submount to one another utilizing the predefined pattern of the B-stage curable die epoxy.

3. The method of claim 2, wherein forming a predefined pattern of B-stage curable die epoxy comprises applying the B-stage curable die epoxy to the electrode by screen printing.

4. The method of claim 3, wherein the screen printing provides a resolution of application of the B-stage curable die epoxy of about 4 mils.

5. The method of claim 2, wherein forming a predefined pattern of B-stage curable die epoxy comprises dispensing the B-stage epoxy onto desired locations of the electrode.

6. The method of claim 2, wherein forming a predefined pattern of B-stage curable die epoxy comprises:

coating the electrode with a B-stage epoxy; and

selectively removing B-stage epoxy from the electrode to provide the predefined pattern.

7. The method of claim 6, wherein the step of selective removing comprises laser scribing the B-stage epoxy to selectively remove epoxy to provide the predefined pattern.

8. The method of claim 6, wherein the B-stage epoxy comprises a photo-sensitive B-stage epoxy and wherein forming a predefined pattern of B-stage curable die epoxy comprises selectively removing epoxy utilizing photolithography to provide the predefined pattern.

9. The method of claim 2, wherein forming a predefined pattern of B-stage curable die epoxy comprises pin transferring the B-stage epoxy to locations on the electrode to provide the predefined pattern.

10. The method of claim 2, wherein forming a predefined pattern of B-stage curable die epoxy is followed by the step of pre-curing the B-stage epoxy.

11. The method of claim 10, wherein pre-curing the B-stage epoxy comprises pre-curing the B-stage epoxy utilizing a temperature of from about 50 to about 150°

C.

12. The method of claim 10, wherein pre-curing the B-stage epoxy comprises pre-curing the B-stage epoxy utilizing a temperature of about 85°

C.

13. The method of claim 2, wherein attaching the electrode of the gallium nitride based light emitting region and the submount to one another utilizing the predefined pattern of the B-stage curable die epoxy comprises:

placing the light emitting device on the submount; and

heating the B-stage epoxy to a final curing temperature so as to cause the B-stage epoxy to re-flow.

14. The method of claim 13, wherein the step of heating comprises heating the B-stage epoxy to a temperature of at least about 150°

C.

15. The method of claim 2, wherein the predefined pattern comprises a single nodule of B-stage epoxy on the electrode.

16. The method of claim 2, wherein the predefined pattern comprises a plurality of bumps of B-stage epoxy on the electrode.

17. The method of claim 2, wherein the predefined pattern comprises a plurality of lines of B-stage epoxy on the electrode.

18. The method of claim 2, wherein the predefined pattern comprises a criss-cross pattern of B-stage epoxy on the electrode.

19. A method for attaching a light emitting device die and a submount to one another in a flip-chip configuration, the light emitting device die having a mesa configuration on a substrate and an electrode on the mesa, the method comprising:

forming predefined pattern of conductive die attach material on at least one of the electrode and the submount;

attaching the light emitting device die and the submount to one another with the conductive die attach material therebetween; and

wherein the predefined pattern of conductive die attach material is selected so as to prevent the conductive die attach material from contacting sidewalls of the mesa and/or the substrate during the attaching.

20. The method of claim 19, wherein the predefined pattern of conductive die attach material provides a volume of die attach material that is less than a volume defined by an area of the electrode and a distance between the electrode and the submount.

21. The method of claim 19, wherein the predefined pattern comprises a single nodule of conductive die attach material on the electrode.

22. The method of claim 19, wherein the predefined pattern comprises a plurality of bumps of conductive die attach material on the electrode.

23. The method of claim 19, wherein the predefined pattern comprises a plurality of lines of conductive die attach material on the electrode.

24. The method of claim 19, wherein the predefined pattern comprises a criss-cross pattern of conductive die attach material on the electrode.

25. The method of claim 19, wherein the conductive die attach material comprises at least one of a B-stage curable die epoxy, a solder paste, a pattern of solder bumps, and/or a conductive polymer.

26. The method of claim 19, wherein the conductive die attach material comprises solder paste, and wherein forming a predefined pattern comprises forming a predefined pattern of solder paste by at least one of screen printing, dispensing and/or pin transferring.

27. The method of claim 19, wherein the conductive die attach material comprises solder bumps and wherein forming a predefined pattern comprises forming a predefined pattern of solder bumps by at least one of dispensing and reflowing, electroplating an/or dipping.

28. The method of claim 19, wherein the conductive die attach material comprises at least one of a B-stage curable die epoxy and/or a conductive polymer, and

wherein forming a predefined pattern comprises forming a predefined pattern of the at least one of a B-stage curable-die epoxy and/or a conductive polymer by at least one of screen printing, dispensing, layering and laser scribing, photolithography and/or pin transferring.

29-63. -63. (Canceled)