Method of fabricating multi-freestanding GaN wafer

• US 20070141813A1
• Filed: 11/14/2006
• Published: 06/21/2007
• Est. Priority Date: 12/27/2005
• Status: Active Grant

• Current Assignee: Corning Precision Materials Company Limited (Corning Incorporated)
• Original Assignee: Samsung Corning Company Limited (Corning Incorporated)
• Inventors: Song, In-Jae
• Granted Patent: US 7,998,272 B2
• Time in Patent Office: Days
• US Class Current: 438/483
• CPC Class Codes: C30B 25/02 Epitaxial-layer growth
• CPC Class Codes: C30B 29/406 Gallium nitride
• CPC Class Codes: H01L 21/0203 Making porous regions on the surface
• CPC Class Codes: H01L 21/02389 Nitrides
• CPC Class Codes: H01L 21/0242 Crystalline insulating materials
• CPC Class Codes: H01L 21/02458 Nitrides
• CPC Class Codes: H01L 21/02507 Alternating layers, e.g. superlattice
• CPC Class Codes: H01L 21/02513 Microstructure
• CPC Class Codes: H01L 21/0254 Nitrides
• CPC Class Codes: H01L 21/0262 Reduction or decomposition of gaseous compounds, e.g. CVD
• CPC Class Codes: H01L 21/02661 In-situ cleaning

Abstract

A method of fabricating a plurality of freestanding GaN wafers includes mounting a GaN substrate in a reactor, forming a GaN crystal growth layer on the GaN substrate through crystal growth, performing surface processing of the GaN crystal growth layer to form a GaN porous layer having a predetermined thickness on the GaN crystal growth layer, repeating the forming of the GaN crystal growth layer and the forming of the GaN porous layer a plurality of times to form a stack of alternating GaN crystal growth layers and GaN porous layers on the GaN substrate, and cooling the stack such that the GaN layers self-separate to form the freestanding GaN wafers. The entire process of forming a GaN porous layer and a thick GaN layer is performed in-situ in a single reactor. The method is very simplified compared to the prior art. In this way, the entire process is performed in one chamber, and in particular, GaN surface processing and growth proceed using an HVPE process gas such that costs are greatly reduced. In particular, since GaN is self-separated from the substrate through cooling, a GaN wafer of good quality without the occurrence of cracks can be produced on a large scale with a high yield.

Claims

1. A method of fabricating a plurality of freestanding gallium nitride (GaN) wafers comprising:

mounting a GaN substrate in a reactor;

forming a GaN crystal growth layer on the GaN substrate through crystal growth;

performing surface processing of the GaN crystal growth layer to form a GaN porous layer having a predetermined thickness on the GaN crystal growth layer;

repeating the forming of a GaN crystal growth layer and the surface processing of the formed GaN crystal growth layer a plurality of times to form a stack of alternating GaN crystal growth layers and GaN porous layers on the GaN substrate; and

cooling the stack such that the GaN crystal growth layers self-separate into the plurality of freestanding GaN wafers.

2. The method of claim 1, wherein the surface processing is performed by supplying an HCl gas and an NH₃ gas into the reactor.

3. The method of claim 2, wherein 50-150 sccm of HCl gas and 500-1500 sccm of NH₃ gas are supplied into the reactor at a room pressure.

4. The method of claim 3, wherein each forming of a GaN porous layer proceeds at a temperature of 900-1200°

C.

5. The method of claim 1, wherein the forming of the stack of alternating GaN crystal growth layers and GaN porous layers is carried out at an elevated temperature and wherein the cooling of the stack is carried out by allowing the stack to cool naturally to room temperature.

6. The method of claim 1, wherein the reactor is a hydride vapor phase epitaxy (HVPE) system reactor.

7. The method of claim 6, further comprising performing surface processing of the GaN substrate before forming the GaN growth layer on the GaN substrate to form a GaN porous layer on the surface of the GaN substrate.

8. The method of claim 1, further comprising performing surface processing of the GaN substrate before forming the GaN growth layer on the GaN substrate to form a GaN porous layer on the surface of the GaN substrate.

9. The method of claim 1, wherein the forming of the GaN crystal growth layer on the GaN substrate through crystal growth, performing of the surface processing of the GaN crystal growth layer to form the GaN porous layer having a predetermined thickness on the GaN crystal growth layer, and repeating the forming of a GaN crystal growth layer and the surface processing of the formed GaN crystal growth layer a plurality of times to form the stack of alternating GaN crystal growth layers and GaN porous layers on the GaN substrate are carried out in situ in a single reactor.

10. The method of claim 1, wherein the cooling of the stack is carried out such that the porous GaN layers fracture to allow the GaN growth layers to be separated into the plurality of freestanding GaN wafers.

11. The method of claim 1, further including polishing at least one of the plurality of freestanding GaN wafers.

12. A method of fabricating a plurality of freestanding GaN wafers comprising:

mounting a semiconductor substrate in a reactor;

forming a GaN crystal growth layer on the semiconductor substrate through crystal growth;

performing surface processing of the GaN crystal growth layer to form a GaN porous layer having a predetermined thickness on the GaN crystal growth layer;

repeating the forming a GaN crystal growth layer and the surface processing of the formed GaN crystal growth layer a plurality of times to form a stack of alternating GaN crystal growth layers and GaN porous layers on the semiconductor substrate; and

cooling the stack such that the GaN crystal growth layers self-separate into the plurality of freestanding GaN wafers.

13. The method of claim 12, wherein the semiconductor substrate is a sapphire substrate, a GaN substrate, an SiC substrate, or a GaAs substrate.

14. The method of claim 13, wherein the surface processing is performed by supplying an HCl gas and an NH₃ gas into the reactor.

15. The method of claim 12, wherein the surface processing is performed by supplying an HCl gas and an NH₃ gas into the reactor.

16. The method of claim 15, wherein 50-150 sccm of HCl gas and 500-1500 sccm of NH₃ gas are supplied into the reactor at a room pressure.

17. The method of claim 16, wherein the forming of the GaN porous layer proceeds at a temperature of 900-1200°

C.

18. The method of claim 15, wherein the forming of the GaN porous layer proceeds at a temperature of 900-1200°

C.

19. The method of claim 12, wherein the forming of the stack of alternating GaN crystal growth layers and GaN porous layers is carried out at an elevated temperature and wherein the cooling of the stack is carried out by allowing the stack to cool naturally to room temperature.

20. The method of claim 12, wherein the reactor is a reactor for a hydride vapor phase epitaxy (HVPE) system.

21. The method of claim 17, wherein the reactor is a reactor for an HVPE system.

22. The method of claim 18, wherein the reactor is a reactor for an HVPE system.

23. The method of claim 12, wherein the forming a GaN crystal growth layer on the semiconductor substrate through crystal growth, performing surface processing of the GaN crystal growth layer to form the GaN porous layer having a predetermined thickness on the GaN crystal growth layer, and repeating the forming of a GaN crystal growth layer and the surface processing of the formed GaN crystal growth layer a plurality of times to form the stack of alternating GaN crystal growth layers and GaN porous layers on the GaN substrate are carried out in situ in a single reactor.

24. The method of claim 12, wherein the cooling of the stack is carried out such that the porous GaN layers fracture to allow the GaN growth layers to be separated into the plurality of freestanding GaN wafers.

25. The method of claim 12, further including polishing at least one of the plurality of freestanding GaN wafers.