Method for producing high efficiency light-emitting diodes and resulting diode structures

• US 5,631,190 A
• Filed: 10/07/1994
• Issued: 05/20/1997
• Est. Priority Date: 10/07/1994
• Status: Expired due to Term

• Current Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Original Assignee: Cree Research, Inc. (Wolfspeed, Inc.)
• Inventors: Negley, Gerald H.
• Primary Examiner(s): KUNEMUND, ROBERT M
• Application Number:
  US08/319,803
• Time in Patent Office: 956 Days
• Field of Search: 437/127, 437/129, 437/905, 148/DIG. 95, 148/DIG. 99, 117/951
• US Class Current: 438/33
• CPC Class Codes: B23K 2101/40 Semiconductor devices
• CPC Class Codes: B23K 2103/50 Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
• CPC Class Codes: B23K 2103/52 Ceramics
• CPC Class Codes: B23K 26/16 Removal of by-products, e.g. particles or vapours produced during treatment of a workpiece by a fluid stream B23K26/142
• CPC Class Codes: B23K 26/40 taking account of the properties of the material involved
• CPC Class Codes: H01L 21/0475 Changing the shape of the semiconductor body, e.g. forming recesses, etching of the semiconductor body H01L21/302
• CPC Class Codes: H01L 33/0054 for devices with an active region comprising only group IV elements
• CPC Class Codes: H01L 33/007 comprising nitride compounds
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/34 containing only elements of Group IV of the Periodic Table
• CPC Class Codes: Y10S 438/94 Laser ablative material removal

Abstract

A method of producing light emitting diodes from silicon carbide with increased external efficiency is disclosed which includes directing a beam of laser light at one surface of a portion of silicon carbide, and in which the laser light is sufficient to vaporize the silicon carbide that it strikes to thereby define a cut in the silicon carbide portion; and then dry etching the silicon carbide portion to remove by-products generated when the laser light cuts the silicon carbide portion. The resulting wafer and diode structure are also disclosed.

Claims

1. A method of producing light emitting diodes from silicon carbide with increased external efficiency, the method comprising:

directing a beam of laser light at one surface of a portion of silicon carbide, and in which the laser light has a wavelength for which the energy equivalent is equal to or greater than the bandgap of the silicon carbide and is sufficient to vaporize the silicon carbide that it strikes to thereby define a cut in the silicon carbide portion; and

dry etching the silicon carbide portion to remove by-products generated when the laser light cuts the silicon carbide portion.

2. A method according to claim 1 wherein the step of directing the laser light comprises directing light with a wavelength of 433 nm or less at a portion of 6H silicon carbide.

3. A method according to claim 1 wherein the step of directing the laser light comprises directing laser light with a wavelength of 355 nm.

4. A method according to claim 1 wherein the step of directing the laser light comprises directing laser light with a wavelength of 266 nm.

5. A method according to claim 1 wherein the step of directing the laser light comprises directing light with a wavelength of 539 nm or less at a portion of 3C silicon carbide.

6. A method according to claim 1 wherein the step of directing the laser light comprises directing light with a wavelength of 380 nm or less at a portion of 4H silicon carbide.

7. A method according to claim 1 wherein the step of directing the laser light comprises directing light with a wavelength of 415 nm or less at a portion of 15R silicon carbide.

8. A method according to claim 1 wherein the step of dry etching the silicon carbide portion comprises reactive ion etching.

9. A method according to claim 8 wherein the step of reactive ion etching comprises reactive ion etching using a fluorine-containing gas.

10. A method according to claim 1 wherein the step of directing the laser light at a silicon carbide portion comprises directing the laser light at a single crystal silicon carbide substrate that has at least two epitaxial layers of silicon carbide thereon that define a p-n junction therebetween.

11. A method according to claim 1 and further comprising separating the cut silicon carbide portion along the cut to form two silicon carbide portions.

12. A method according to claim 1 wherein the step of directing the laser beam comprises Q-switching the laser beam.

13. A method of producing light emitting diodes from silicon carbide with increased external efficiency, the method comprising:

directing a beam of laser light at one surface of a wafer formed of a plurality of adjacent silicon carbide light emitting diode precursors, and in which the laser light has a wavelength for which the energy equivalent is equal to or greater than the bandgap of the silicon carbide and is sufficient to vaporize the silicon carbide that it strikes to thereby define a cut in the silicon carbide portion;

directing the laser light along the surface of the wafer in a pattern that forms a plurality of trenches between the adjacent light emitting diode precursors; and

dry etching the wafer to remove by-products generated when the laser beam cuts the wafer.

14. A method according to claim 13 wherein the step of directing a beam of laser light at one surface of the wafer comprises directing a beam at the rear substrate surface of the wafer.

15. A method according to claim 13 wherein the step of directing a beam of laser light at one surface of the wafer comprises directing a beam at the front device surface of the wafer.

16. A method according to claim 13 further comprising the step of separating the wafer along the trenches following the step of dry etching the wafer.

17. A method according to claim 13 further comprising the step of applying metal contacts to the diode precursors on the wafer prior to the step of directing the laser light on the wafer.

18. A method according to claim 13 wherein the step of directing the laser light comprises directing light with a wavelength of 433 nm or less at a portion of 6H silicon carbide.

19. A method according to claim 13 wherein the step of directing the laser light comprises directing light with a wavelength of 539 nm or less at a portion of 3C silicon carbide.

20. A method according to claim 13 wherein the step of directing the laser light comprises directing light with a wavelength of 380 nm or less at a portion of 4H silicon carbide.

21. A method according to claim 13 wherein the step of directing the laser light comprises directing light with a wavelength of 415 nm or less at a portion of 15R silicon carbide.

22. A method according to claim 13 wherein the step of directing the laser light comprises directing laser light with a wavelength of 355 nm.

23. A method according to claim 13 wherein the step of directing the laser light comprises directing laser light with a wavelength of 266 nm.

24. A method according to claim 13 wherein the step of directing the laser beam comprises Q-switching the laser beam.

25. A method of producing light emitting diodes from silicon carbide with increased external efficiency, the method comprising:

directing a beam of laser light at one surface of a wafer formed of a plurality of adjacent gallium nitride light emitting diode precursors, and in which the laser light has a wavelength for which the energy equivalent is equal to or greater than the bandgap of the gallium nitride and is sufficient to vaporize the gallium nitride that it strikes to thereby define a cut in the gallium nitride;

directing the laser light along the surface of the wafer in a pattern that forms a plurality of trenches between the adjacent light emitting diode precursors; and

dry etching the wafer to remove vaporized by-products generated when the laser beam cuts the wafer.

26. A method according to claim 25 further comprising the step of separating the wafer along the trenches following the step of dry etching the wafer.

27. A method according to claim 25 further comprising the step of applying metal contacts to the diode precursors on the wafer prior to the step of directing the laser light on the wafer.

28. A method according to claim 25 wherein the step of directing the laser light comprises directing light with a wavelength of 369 nm or less at a portion of gallium nitride.

29. A method according to claim 25 wherein the step of directing the laser light comprises directing laser light with a wavelength of 266 nm.

30. A method according to claim 25 wherein the step of directing the laser light further comprises q-switching the laser light.