LED bonding structures and methods of fabricating LED bonding structures

• US 7,642,121 B2
• Filed: 11/11/2008
• Issued: 01/05/2010
• Est. Priority Date: 04/28/2004
• Status: Active Grant

• Current Assignee: CREE Led Incorporated (Smart Global Holdings Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Edmond, John Adam, Slater, David Beardsley Jr.
• Primary Examiner(s): Pham; Long
• Assistant Examiner(s): Rao; Steven H
• Application Number:
  US12/268,466
• Publication Number:
  US 20090068774A1
• Time in Patent Office: 420 Days
• Field of Search: 438/26, 438/28, 438/35, 438/108
• US Class Current: 438/85
• 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 2924/01079 Gold [Au]
• 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 33/40 Materials therefor
• 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

A method is disclosed for fabricating an LED The method includes providing an LED chip having an epitaxial region comprising at least a p-type layer and an n-type layer, an ohmic contact formed on at least one of the p-type layer or the n-type layer, and a bond pad formed on the ohmic contact. The bond pad has a total volume less than about 3×10⁻⁵ mm³. The LED chip is bonded to a submount via thermocompression or thermosonic bonding.

Claims

1. A method of fabricating an LED comprising:

providing an LED chip having an epitaxial region comprising at least a p-type layer and an n-type layer, an ohmic contact formed on at least one of the p-type layer or the n-type layer, and a bond pad formed on the ohmic contact, the bond pad having a total volume less than about 3×

10<sup>−

5</sup> mm³;

conductively joining the LED chip to a submount.

2. A method as recited in claim 1, wherein the step of bonding the LED chip to a submount comprises applying a force of about 30 to 70 g to the LED chip.

3. A method as recited in claim 2, wherein the applied force is about 50 g.

4. A method as recited in claim 1, wherein the LED chip includes a substrate, and the ohmic contact is formed on a surface of the epitaxial region opposite the substrate.

5. A method as recited in claim 1, wherein the bond pad has a total volume less than about 2.5×

10<sup>−

5</sup> mm³.

6. A method as recited in claim 1, wherein the bond pad is formed in the shape of a parallelepiped having a generally square periphery.

7. A method as recited in claim 6, wherein the epitaxial region has a width of about 250 μ

m or more, and wherein the bond pad has a height of about 1.2 μ

m or less and a width of about 150 μ

m or less.

8. A method as recited in claim 1, wherein the bond pad is formed in the shape of a cylinder having a generally circular periphery.

9. A method as recited in claim 8, wherein the epitaxial region has a width of about 250 μ

m or more, and wherein the bond pad has a height of about 2 μ

m or less and a diameter less than one half the width of the epitaxial region.

10. A method as recited in claim 9, wherein the bond pad has a diameter of about 120 μ

m or less.

11. A method as recited in claim 1, wherein the bond pad is formed in the shape of a polyhedron having opposing parallel faces and a star-shaped or cross-shaped periphery.

12. A method as recited in claim 11, wherein the distance from an edge of the bond pad to an edge of the epitaxial region is at least about 20 μ

m.