Method and apparatus for producing large, single-crystals of aluminum nitride

• US 9,447,521 B2
• Filed: 10/22/2014
• Issued: 09/20/2016
• Est. Priority Date: 12/24/2001
• Status: Expired due to Term

• Current Assignee: Crystal IS, Inc. (Asahi Kasei Corporation)
• Original Assignee: Crystal IS, Inc. (Asahi Kasei Corporation)
• Inventors: Schowalter, Leo, Slack, Glen A., Rojo, Juan Carlos, Bondokov, Robert T., Morgan, Kenneth E., Smart, Joseph A.
• Primary Examiner(s): MULVANEY, ELIZABETH EVANS
• Application Number:
  US14/520,615
• Publication Number:
  US 20150079329A1
• Time in Patent Office: 699 Days
• US Class Current: 1/1
• CPC Class Codes: C30B 11/003 Heating or cooling of the melt or the crystallised material
• CPC Class Codes: C30B 23/00 Single-crystal growth by condensing evaporated or sublimed materials
• CPC Class Codes: C30B 23/025 characterised by the substrate
• CPC Class Codes: C30B 25/10 Heating of the reaction chamber or the substrate
• CPC Class Codes: C30B 25/14 Feed and outlet means for the gases; Modifying the flow of the reactive gases
• CPC Class Codes: C30B 25/16 Controlling or regulating controlling or regulating in general G05
• CPC Class Codes: C30B 25/20 the substrate being of the same materials as the epitaxial layer
• CPC Class Codes: C30B 29/403 AIII-nitrides
• CPC Class Codes: H01L 21/02389 Nitrides
• CPC Class Codes: H01L 21/02458 Nitrides
• CPC Class Codes: H01L 21/0254 Nitrides
• CPC Class Codes: H01L 21/02634 Homoepitaxy
• CPC Class Codes: H01L 29/04 characterised by their crystalline structure, e.g. polycrystalline, cubic or particular orientation of crystalline planes characterised by physical imperfections H01L29/30
• CPC Class Codes: H01L 29/0657 characterised by the shape of the body
• CPC Class Codes: H01L 29/2003 Nitride compounds
• CPC Class Codes: H01L 29/205 in different semiconductor regions , e.g. heterojunctions
• CPC Class Codes: H01L 29/32 the imperfections being within the semiconductor body
• CPC Class Codes: H01L 29/66462 with a heterojunction interface channel or gate, e.g. HFET, HIGFET, SISFET, HJFET, HEMT
• CPC Class Codes: H01L 29/7787 with wide bandgap charge-carrier supplying layer, e.g. direct single heterostructure MODFET
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 : Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 33/0075 : comprising nitride compounds
• CPC Class Codes: H01L 33/025 : Physical imperfections, e.g. particular concentration or distribution of impurities
• CPC Class Codes: H01L 33/12 : with a stress relaxation structure, e.g. buffer layer
• CPC Class Codes: H01L 33/325 : characterised by the doping materials
• CPC Class Codes: Y10T 428/21 : Circular sheet or circular blank

Abstract

Bulk single crystals of AlN having a diameter greater than about 25 mm and dislocation densities of about 10,000 cm⁻² or less and high-quality AlN substrates having surfaces of any desired crystallographic orientation fabricated from these bulk crystals.

Claims

1. An aluminum nitride single-crystal boule having a diameter greater than about 25 mm, a surface substantially all of which has a single crystalline orientation, and an average dislocation density less than about 10,000 cm⁻

2.

2. The single-crystal boule of claim 1 wherein the average dislocation density is less than about 5,000 cm⁻

2.

3. The single-crystal boule of claim 2 wherein the average dislocation density is less than about 1,000 cm⁻

2.

4. The single-crystal boule of claim 3 wherein the average dislocation density is less than about 500 cm⁻

2.

5. The single-crystal boule of claim 4 wherein the average dislocation density is less than about 100 cm⁻

2.

6. The single-crystal boule of claim 5 having at least one region substantially devoid of dislocation defects.

7. The single-crystal boule of claim 1 wherein the diameter is about 50 mm.

8. The single-crystal boule of claim 1 having a length exceeding 5 mm.

9. The single-crystal boule of claim 1 having a length less than approximately 35 mm.

10. A method of producing single-crystal AlN, the method comprising:

providing Al and N₂ vapor in a crystal growth enclosure;

providing a nucleation site in the crystal growth enclosure;

maintaining in the crystal growth enclosure (i) an N₂ partial pressure greater than stoichiometric pressure relative to the Al, (ii) a total vapor pressure at super-atmospheric pressure, (iii) an axial thermal gradient along a growth direction, and (iv) a lateral thermal gradient (a) along a direction substantially perpendicular to the growth direction and (b) in which a temperature at the nucleation site is lower than that in a region laterally displaced therefrom; and

depositing the Al and N₂ vapor under conditions capable of growing single crystalline AlN originating at the nucleation site.

11. The method of claim 10, wherein the axial thermal gradient and the lateral thermal gradient are maintained at least in part by a plurality of baffles disposed outside of the crystal growth enclosure and at least at one of (i) a proximal end of the crystal growth enclosure or (ii) a distal end of the crystal growth enclosure opposite the proximal end, growth of the single crystalline AlN extending from the distal end toward the proximal end.

12. The method of claim 11, wherein one or more of the baffles comprise tungsten.

13. The method of claim 11, wherein one or more of the baffles each defines a hole therethrough.

14. The method of claim 11, wherein one or more baffles are disposed at each of the distal end and the proximal end.

15. The method of claim 10, wherein the lateral thermal gradient is convex in the growth direction.

16. The method of claim 10, wherein the axial thermal gradient is greater than 100°

C./cm.

17. The method of claim 10, wherein the crystal growth enclosure comprises a selective barrier configured to substantially prevent passage of Al vapor and permit passage of N₂ vapor therethrough.

18. The method of claim 10, further comprising disposing a seed crystal at the nucleation site.

19. The method of claim 10, wherein providing the Al and N₂ vapor comprises subliming solid source material.

20. The method of claim 10, wherein providing the Al and N₂ vapor comprises injecting a source gas.