Methods of processing semiconductor wafer backsides having light emitting devices (LEDS) thereon and leds so formed

• US 20050151138A1
• Filed: 11/12/2004
• Published: 07/14/2005
• Est. Priority Date: 11/12/2003
• Status: Active Grant

• Current Assignee: CREE Led Incorporated (Smart Global Holdings Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Donofrio, Matthew, Slater, David B. Jr.
• Granted Patent: US 7,291,529 B2
• Time in Patent Office: Days
• US Class Current: 257/79
• CPC Class Codes: H01L 21/78 with subsequent division of the substrate into plural individual devices cutting to change the surface-physical characteristics or shape of semiconductor bodies H01L21/304
• CPC Class Codes: H01L 33/0095 Post-treatment of devices, e.g. annealing, recrystallisation or short-circuit elimination
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate

Abstract

Processing a semiconductor wafer can include forming a plurality of Light Emitting Devices (LED) on a semiconductor wafer having a first thickness. The plurality of LEDs on the wafer are brought into contact with a surface of a carrier to couple the wafer to the carrier. The first thickness of the wafer is reduced to a second thickness that is less than the first thickness by processing the backside of the wafer. The carrier is separated from the plurality of LEDs on the wafer and the wafer is cut to separate the plurality of LEDs from one another. Related devices are also disclosed.

Claims

1. A method of processing a semiconductor wafer to form a light emitting device, comprising:

forming a plurality of Light Emitting Devices (LED) on a semiconductor wafer having a first thickness;

contacting the plurality of LEDs on the wafer to a surface of a carrier to couple the wafer to the carrier;

reducing the first thickness of the wafer to a second thickness that is less than the first thickness by processing a backside of the wafer;

separating the carrier from the plurality of LEDs on the wafer; and

cutting the wafer to separate the plurality of LEDs.

2. A method according to claim 1 wherein the first thickness comprises a thickness from about 250 μ

m to about 400 μ

m.

3. A method according to claim 1 wherein reducing the first thickness of the wafer comprises grinding, lapping, and/or etching the backside of the wafer to reduce the first thickness of the wafer to the second thickness of less than about 150 μ

m.

4. A method according to claim 1 wherein reducing the first thickness of the wafer comprises grinding, lapping, and/or etching the backside of the wafer to reduce the first thickness of the wafer to the second thickness of less than about 120 μ

m.

5. A method according to claim 4 wherein grinding the backside of the wafer comprises grinding the backside of the wafer using an in-feed grinder or a creep feed grinder.

6. A method according to claim 1 wherein cutting the wafer comprises cutting the wafer using a saw blade to form straight edges on the separated plurality of LEDs.

7. A method according to claim 1 wherein cutting the wafer comprises:

cutting score lines on the wafer to form beveled grooves between the plurality of LEDs on the wafer; and

separating the plurality of LEDs on the wafer from one another along the score lines.

8. A method according to claim 1 wherein cutting the wafer comprises cutting the wafer with a saw blade to depth beneath a surface of the wafer of less than about a length of a beveled tip of the saw blade.

9. A method according to claim 8 wherein the depth comprises less than about 120 μ

m.

10. A method according to claim 1 wherein reducing the first thickness of the wafer to a second thickness is followed by:

processing the backside surface of the wafer opposite the plurality of LEDs to improve light extraction; and

forming a plurality of respective contacts on the backside surface opposite where respective bonding pads are to be formed on the plurality of LEDs.

11. A method according to claim 10 wherein processing comprises etching the backside surface.

12. A method according to claim 10 wherein processing comprises laser patterning the backside surface.

13. A method according to claim 10 wherein forming a plurality of respective contacts comprises forming a plurality of ohmic contacts using laser annealing.

14. A method according to claim 1 wherein separating the carrier from the plurality of LEDs on the wafer comprises heating, melting or dissolving an adhesive layer sufficient to cause separation of the plurality of LEDs from the carrier.

15. A method according to claim 1 wherein the wafer comprises a Silicon Carbide or sapphire wafer.

16. A method of processing a semiconductor wafer to form a light emitting device, comprising:

forming a plurality of Light Emitting Devices (LED) on a semiconductor wafer having a thickness;

contacting the plurality of LEDs on the wafer to a surface of a carrier to couple the plurality of LEDs to the carrier;

reducing the thickness of the wafer to less than about 150 μ

m;

separating the carrier from the plurality of LEDs on the wafer; and

cutting the wafer with a saw blade to depth beneath a surface of the wafer of less than about a length of a beveled tip of the saw blade to separate the plurality of LEDs on the wafer from one another.

17. A method according to claim 16 wherein reducing the thickness of the wafer further comprises further reducing the thickness of the wafer to less than about 120 μ

m.

18. A method according to claim 16 wherein reducing the thickness of the wafer is followed by:

processing a backside surface of the wafer opposite the plurality of LEDs to improve light extraction.

19. A method according to claim 18 further comprising:

forming a plurality of respective contacts on the backside surface opposite where respective bonding pads are to be formed on the plurality of LEDs.

20. A method according to claim 16 wherein the wafer comprises a Silicon Carbide or sapphire wafer.

21. A light emitting device (LED) on a Silicon Carbide (SiC) substrate, comprising an LED on a SiC substrate, the SiC substrate having a first thickness of less than about 150 μ

m.

22. An LED according to claim 21 wherein a forward voltage associated with the SiC substrate is less than about 3.4 volts.

23. An LED according to claim 21 wherein the SiC substrate comprises 4H—

SiC or 6H—

SiC.