DEFECT REDUCTION IN SEEDED ALUMINUM NITRIDE CRYSTAL GROWTH

• US 20080182092A1
• Filed: 01/17/2008
• Published: 07/31/2008
• Est. Priority Date: 01/17/2007
• Status: Active Grant

• Current Assignee: Crystal IS, Inc. (Asahi Kasei Corporation)
• Original Assignee: Crystal IS, Inc. (Asahi Kasei Corporation)
• Inventors: Morgan, Kenneth E., Slack, Glen A., Schowalter, Leo J., Bondokov, Robert T.
• Granted Patent: US 8,323,406 B2
• Time in Patent Office: Days
• US Class Current: 428/220
• 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 29/403 AIII-nitrides
• CPC Class Codes: H01L 21/02389 Nitrides
• CPC Class Codes: Y10T 428/2982 Particulate matter [e.g., sphere, flake, etc.]

Abstract

Bulk single crystal of aluminum nitride (AlN) having an a real planar defect density≦100 cm⁻² Methods for growing single crystal aluminum nitride include melting an aluminum foil to uniformly wet a foundation with a layer of aluminum, the foundation forming a portion of an AlN seed holder, for an AlN seed to be used for the AlN growth. The holder may consist essentially of a substantially impervious backing plate.

Claims

1. A bulk single crystal of AlN having a diameter greater than 20 mm, a thickness greater than 0.1 mm, and an areal planar defect density ≦

100 cm<sup>−

2</sup>.

2. The bulk single crystal of claim 1, wherein the areal planar defect density is measured by counting all planar defects in the bulk single crystal and dividing by a cross-sectional area of the bulk single crystal disposed in a plane perpendicular to a growth direction thereof.

3. The bulk single crystal of claim 1, wherein the bulk single crystal is in the form of a boule having a thickness greater than 5 mm.

4. The bulk single crystal of claim 3, wherein the areal planar defect density is ≦

1 cm<sup>−

2</sup>.

5. The bulk single crystal of claim 1, wherein the single crystal AlN is in the form of a wafer.

6. The bulk single crystal of claim 5, wherein the areal planar defect density is ≦

10 cm<sup>−

2</sup>.

7. The bulk single crystal of claim 5, wherein an areal planar defect density of planar defects intersecting each of a top and a bottom surface of the wafer is ≦

1 cm<sup>−

2</sup>.

8. A boule comprising a bulk single crystal of AlN, having a diameter greater than 20 mm, a thickness greater than 5 mm, and an areal density of threading dislocations ≦

10⁶ cm<sup>−

2</sup> in each cross-section of the bulk single crystal disposed in a plane perpendicular to a growth direction of the crystal.

9. The boule of claim 8, wherein the areal density of threading dislocations is ≦

4 cm<sup>−

2</sup>.

10. A boule comprising a bulk single crystal of AlN having a sufficient thickness to enable the formation of at least five wafers therefrom, each wafer having a thickness of at least 0.1 mm, a diameter of at least 20 mm, and a threading dislocation density ≦

10⁶ cm<sup>−

2</sup>.

11. The boule of claim 10, wherein each wafer has a threading dislocation density ≦

10⁴ cm<sup>−

2</sup>.

12. A boule comprising a substantially cylindrical bulk single crystal of AlN having a diameter of at least 20 mm and having a sufficient thickness to enable the formation of at least five wafers therefrom, each wafer having a thickness of at least 0.1 mm a diameter of at least 20 mm, and a triple-crystal X-ray rocking curve of less than 50 arcsec full width at half maximum (FWHM) for a (0002) reflection, wherein each wafer has substantially the same diameter as each of the other wafers.

13. A method for growing single-crystal aluminum nitride (AlN), the method comprising the steps of:

(a) providing a holder comprising a backing plate, the holder (i) being sized and shaped to receive an AlN seed therein and (ii) including an AlN foundation bonded to the backing plate;

(b) interposing an Al foil between the seed and the AlN foundation;

(c) melting the Al foil to uniformly wet the foundation with a layer of Al;

(d) disposing an AlN seed within the holder; and

(e) depositing aluminum and nitrogen onto the seed under conditions suitable for growing single-crystal AlN originating at the seed.

14. The method of claim 13 further comprising the step of conditioning the backing plate to reduce permeability of the back plate to Al.

15. The method of claim 13 where the seed crystal is a wafer having a diameter of at least 20 mm.

16. The method of claim 15 where the grown single-crystal AlN defines a boule having a diameter approximately the same as a diameter of the seed crystal.

17. A method for growing single-crystal aluminum nitride (AlN), the method comprising the steps of:

(a) providing a holder sized and shaped to receive an AlN seed therein, the holder consisting essentially of a substantially impervious backing plate;

(b) disposing an AlN seed within the holder;

(c) interposing an Al foil between the seed and the backing plate;

(d) melting the Al foil to uniformly wet the backing plate and the back of the AlN seed with a layer of Al; and

(e) depositing aluminum and nitrogen onto the seed under conditions suitable for growing single-crystal AlN originating at the seed.