Optoelectronic substrate and methods of making same

• US 8,541,290 B2
• Filed: 06/07/2011
• Issued: 09/24/2013
• Est. Priority Date: 01/13/2005
• Status: Active Grant

• Current Assignee: Soitec S.A.
• Original Assignee: Soitec S.A.
• Inventors: Letertre, Fabrice, Faure, Bruce
• Primary Examiner(s): Reames, Matthew
• Assistant Examiner(s): LIU, BENJAMIN T
• Application Number:
  US13/154,510
• Publication Number:
  US 20110237008A1
• Time in Patent Office: 840 Days
• Field of Search: 438/459, 438/464, 438/460, 438/29, 438/33, 438/455, 438/458, 257/98, 257/E21.568
• US Class Current: 438/464
• CPC Class Codes: H01L 21/2007 Bonding of semiconductor wafers to insulating substrates or to semiconducting substrates using an intermediate insulating layer H01L21/2011 takes precedence; bonding of semiconductor wafers to semiconductor wafers for junction formation H01L21/187
• CPC Class Codes: H01L 21/76254 with separation/delamination along an ion implanted layer, e.g. Smart-cut, Unibond
• CPC Class Codes: H01L 31/1892 methods involving the use of temporary, removable substrates
• CPC Class Codes: H01L 33/0093 Wafer bonding; Removal of the growth substrate
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy

Abstract

A method of fabricating a device by providing an auxiliary substrate having a metal nitride layer disposed thereon where the nitride layer has a nitrogen face and an opposite face and a dislocation density that is less than about 10⁶, with the nitrogen face of the nitride layer facing the auxiliary substrate; depositing at least one epitaxial nitride layer on the exposed opposite face of the nitride layer of the structure; depositing a further metal layer over at least a portion of the epitaxial nitride layer(s); bonding a final substrate on the deposited metal layer; and removing the auxiliary substrate to form the device from the final substrate and deposited layers. Preferably, the device that is formed includes a LED or laser.

Claims

1. An improved method of fabricating a device having a Group III nitride layer, in which method an auxiliary substrate is provided having a first Group III nitride layer disposed thereon, and then at least one epitaxial Group III nitride layer is deposited on an exposed face of the first Group III nitride layer, and then a further metal layer is deposited over at least a portion of the epitaxial Group III nitride layer(s), and then a final substrate is bonded on the deposited metal layer, and finally the auxiliary substrate is removed to form the device from the final substrate and deposited layers, wherein the improvement comprises providing the auxiliary substrate by the steps comprising:

preparing a bonding surface of a free-standing Group III nitride substrate by polishing the N-face of such substrate and then by depositing a dielectric layer onto the polished N-face, wherein the free-standing Group III nitride substrate has a dislocation density that is less than about 10⁶ and an exposed Ga-face opposite to the N-face;

implanting one or more atomic species through the dielectric layer into the Group III nitride substrate in order to form a splitting area below the N-face of Group III nitride substrate;

bonding the bonding surface of the dielectric layer of the free-standing Group III nitride substrate to the auxiliary substrate; and

splitting the free-standing Group III nitride substrate at the splitting area to leave the auxiliary substrate with the first Group III nitride layer disposed thereon, the first Group III nitride layer having a nitrogen face that faces the auxiliary substrate and an opposite Ga-face that is exposed.

2. The improved method of claim 1 wherein the improvement further comprises polishing the exposed Ga-face of the split surface of the first Group III nitride layer.

3. The improved method of claim 2, wherein the exposed Ga-face of the metal nitride layer has a roughness on the order of a few Angstroms RMS as measured with an atomic force microscope over a field of 1×

1 μ

m².

4. The method of claim 3, which further comprises depositing one or more epitaxial layers upon the exposed Ga-face of the metal nitride layer.

5. The method of claim 4, wherein each deposited epitaxial layer has a dislocation density that is less than about 10⁶.

6. The method of claim 4, wherein each deposited epitaxial layers comprises n type GaN, AlGaN, or InGaN.

7. The method of claim 4, wherein each epitaxial layer is deposited to a thickness of between 0.1 to 1 micron.

8. The method of claim 4, wherein each deposited epitaxial layer has a thickness of about 0.5 micron.

9. The method of claim 4, which further comprises providing an electrical contact on the deposited epitaxial layer(s).

10. The improved method of claim 1 wherein the fabricated device is structured to function as a high-efficiency, long-lived optoelectronic device.

11. The improved method of claim 1, wherein the device that is formed includes a LED or laser.

12. The improved method of claim 1, wherein the nitrogen face of the Group III nitride substrate is polished to have a surface roughness of less than 0.3 nm RMS as measured with an atomic force microscope over a field of 1×

1 μ

m².

13. The method of claim 1, wherein the auxiliary substrate has a coefficient of thermal expansion that is higher than that of the metal nitride layer.

14. The method of claim 1, which further comprises removing the Group III nitride layer after removing the auxiliary substrate.

15. The method of claim 1, wherein the Group III nitride layer is GaN or AlN.

16. The method of claim 1, wherein the auxiliary substrate comprises at least one of silicon, GaAs, or ZnO.

17. The method of claim 1, which further comprises providing a reflection layer disposed upon the Ga-face of metal nitride layer of the auxiliary substrate.