Method of fabricating GaN substrate

• US 8,349,076 B2
• Filed: 10/11/2006
• Issued: 01/08/2013
• Est. Priority Date: 10/12/2005
• Status: Expired due to Fees

• Current Assignee: Samsung Corning Precision Materials Company Limited (Corning Incorporated)
• Original Assignee: Samsung Corning Precision Materials Company Limited (Corning Incorporated)
• Inventors: Song, In-Jae, Han, Jai-yong
• Primary Examiner(s): SONG, MATTHEW J
• Application Number:
  US11/545,518
• Publication Number:
  US 20070082465A1
• Time in Patent Office: 2,281 Days
• Field of Search: 117/88, 117/89, 117/94, 117/95, 117/90, 117/97, 117/106, 117 81- 87, 117/71, 117/93, 117/99, 117/102, 117/105, 117/952, 257/E21.119, 257/E21.131, 257/E21.132, 438/604
• US Class Current: 117/90
• CPC Class Codes: C30B 25/183 being provided with a buffer layer, e.g. a lattice matching layer
• CPC Class Codes: C30B 25/186 being specially pre-treated by, e.g. chemical or physical means
• CPC Class Codes: C30B 29/406 Gallium nitride
• CPC Class Codes: C30B 33/06 Joining of crystals
• CPC Class Codes: H01L 21/0237 Materials
• CPC Class Codes: H01L 21/0242 Crystalline insulating materials
• CPC Class Codes: H01L 21/02458 Nitrides
• 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 21/02658 Pretreatments cleaning in general H01L21/02041
• CPC Class Codes: H01L 21/02664 Aftertreatments planarisation in general H01L21/304

Abstract

A method of fabricating a freestanding gallium nitride (GaN) substrate includes: preparing a GaN substrate within a reactor; supplying HCl and NH₃ gases into the reactor to treat the surface of the GaN substrate and forming a porous GaN layer; forming a GaN crystal growth layer on the porous GaN layer; and cooling the GaN substrate on which the GaN crystal growth layer has been formed and separating the GaN crystal growth layer from the substrate. According to the fabrication method, the entire process including forming a porous GaN layer and a thick GaN layer is performed in-situ within a single reactor. The method is significantly simplified compared to a conventional fabrication method. The fabrication method enables the entire process to be performed in one chamber while allowing GaN surface treatment and growth to be performed using HVPE process gases, thus resulting in a significant reduction in manufacturing costs. The fabrication method also allows self-separation of thick GaN without cracking, thus achieving a short process time and a high manufacturing yield.

Claims

1. A method of fabricating a freestanding gallium nitride (GaN) substrate, the method comprising:

preparing a GaN substrate layer within a reactor;

supplying HCl and NH₃ gases and N₂ carrier gas into the reactor and using the HCl and NH₃ gases to treat a surface of the GaN substrate layer and to form a porous GaN layer in the GaN substrate layer;

forming a GaN crystal growth layer directly on the porous GaN layer; and

naturally in the reactor, cooling to room temperature the GaN substrate layer on which the porous GaN layer and the GaN crystal growth layer are formed, thereby separating the GaN crystal growth layer from the GaN substrate layer and GaN porous layer to provide the freestanding GaN substrate,

wherein the preparing of the GaN substrate layer comprises loading a semiconductor substrate into the reactor and forming the GaN substrate layer on the semiconductor substrate.

2. The method of claim 1, wherein the semiconductor substrate is one of sapphire, SiC, and GaN substrates.

3. The method of claim 2, wherein the HCl, NH₃ and N₂ gases are supplied into the reactor at 50 to 150 sccm, 500 to 1,500 sccm, and 8,000 sccm, respectively, at atmospheric pressure.

4. The method of claim 1, wherein the forming of the porous GaN layer is performed at a temperature of 900°

C. to 1,200°

C.

5. The method of claim 4, wherein the HCl, NH₃ and N₂ gases are supplied into the reactor at 50 to 150 sccm, 500 to 1,500 sccm, and 8,000 sccm, respectively, at atmospheric pressure.

6. The method of claim 1, wherein the forming of the porous GaN layer and the forming of the GaN crystal growth layer are carried out at an elevated temperature and wherein the cooling is carried out by allowing the GaN substrate layer on which the porous GaN layer and the GaN crystal growth layer are formed to cool naturally to room temperature.

7. The method of claim 6, wherein the HCl, NH₃ and N₂ gases are supplied at 50 to 150 sccm, 500 to 1,500 sccm, and 8,000 sccm, respectively, at atmospheric pressure.

8. The method of claim 1, wherein the reactor is a reactor of an HVPE (Hydride Vapor Phase Epitaxy) system.

9. The method of claim 1, wherein the HCl, NH₃ and N₂ gases are supplied into the reactor at 50 to 150 sccm, 500 to 1,500 sccm, and 8,000 sccm, respectively, at atmospheric pressure.

10. The method of claim 1, wherein the porous GaN layer is formed by supplying HCl and NH₃ gases such that GaN at the surface of the GaN substrate layer decomposes to generate and discharge GaCl and H₂ gases to create voids on the surface of the GaN substrate layer.

11. The method of claim 10, wherein the voids are created in the GaN substrate layer to have a pre-determined depth, thereby providing the porous GaN layer with a pre-determined thickness.

12. The method of claim 1, wherein the preparing of a GaN substrate layer;

the supplying to HCl and NH₃ gases to treat the surface of the GaN substrate layer, the forming of the porous GaN layer in the GaN substrate layer;

the forming of the GaN crystal growth layer on the porous GaN layer;

the cooling of the GaN substrate layer on which the porous GaN layer and the GaN crystal growth layer are formed and the separating of the GaN crystal growth layer from the GaN substrate layer and GaN porous layer to provide the freestanding GaN substrate are carried out in a single reactor.

13. The method of claim 1, wherein the cooling of the GaN substrate layer on which the porous GaN layer and the GaN crystal growth layer are formed is carried out such that the porous GaN layer fractures to allow the GaN crystal growth layer to be separated.

14. The method of claim 1, further including polishing the freestanding GaN substrate.

15. A method of fabricating a freestanding gallium nitride (GaN) substrate, the method comprising:

loading a starting GaN wafer into a reactor;

supplying HCl and NH₃ gases and N₂ carrier gas into the reactor and using the HCl and NH₃ gases to treat a surface of the GaN wafer and to form a porous GaN layer to a predetermined thickness at the surface of the GaN wafer;

forming a GaN crystal growth layer directly on the porous GaN layer; and

in the reactor, cooling to room temperature the GaN wafer on which the porous GaN layer and GaN crystal growth layer are formed such that the GaN crystal growth layer separates from the GaN wafer and GaN porous layer to provide the freestanding GaN substrate.

16. The method of claim 15, wherein the forming of the porous GaN layer is performed at a temperature of 900°

C. to 1,200°

C.

17. The method of claim 15, wherein the reactor is a reactor of an HVPE (Hydride Vapor Phase Epitaxy) system.

18. The method of claim 15, wherein the forming of the porous GaN layer and the forming of the GaN crystal growth layer are carried out at an elevated temperature and wherein the cooling is carried out by allowing the GaN wafer on which the porous GaN layer and the GaN crystal growth layer are formed to cool naturally to room temperature.

19. The method of claim 15, wherein the HCl, NH₃ and N₂ gases are supplied into the reactor at 50 to 150 sccm, 500 to 1,500 sccm, and 8,000 sccm, respectively, at atmospheric pressure.

20. The method of claim 15, wherein the porous GaN layer is formed by supplying HCl and NH₃ gases such that GaN at the surface of the GaN substrate layer decomposes to generate and discharge GaCl and H₂ gases to create voids on the surface of the GaN substrate layer.

21. The method of claim 20, wherein the voids are created in the GaN substrate layer to have a pre-determined depth, thereby providing the porous GaN layer with the pre-determined thickness.

22. The method of claim 15, wherein the preparing of a GaN substrate layer;

the supplying to HCl and NH₃ gases to treat the surface of the GaN substrate layer, the forming of the porous GaN layer in the GaN substrate layer;

the forming of the GaN crystal growth layer on the porous GaN layer;

the cooling of the GaN substrate layer on which the porous GaN layer and the GaN crystal growth layer are formed and the separating of the GaN crystal growth layer from the GaN substrate layer and GaN porous layer to provide the freestanding GaN substrate are carried out in a single reactor.

23. The method of claim 15, wherein the cooling of the GaN wafer on which the porous GaN layer and the GaN crystal growth layer are formed is carried out such that the porous GaN layer fractures to allow the GaN crystal growth layer to be separated.

24. The method of claim 15, further comprising polishing the freestanding GaN substrate.