# US 2013/0152852 A1 · Large aluminum nitride crystals with reduced defects and methods of making them

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- Number: US 2013/0152852 A1
- Document ID: US20130152852A1
- Status: Published application
- Kind: A1
- Application number: 13/706,966
- Filed: 2012-12-06
- Published: 2013-06-20
- Earliest claimed: 2005-11-28
- Assignees: Crystal IS, Inc.
- Inventors: Robert T. Bondokov; Kenneth E. Morgan; Glen A. Slack; Leo Schowalter
- Web page: https://patentgrep.com/patent/US20130152852A1

## CPC

- C30B 33/02: Heat treatment (C30B33/04, C30B33/06 take precedence)
- B28D 5/00: Fine working of gems, jewels, crystals, e.g. of semiconductor material; apparatus or devices therefor (working by grinding or polishing B24; for artistic purposes B44B)
- C23C 16/34: Nitrides {(C23C16/303 takes precedence)}
- C30B 23/00: Single-crystal growth by condensing evaporated or sublimed materials
- C30B 23/02: Epitaxial-layer growth
- C30B 25/02: Epitaxial-layer growth
- C30B 25/08: Reaction chambers; Selection of materials therefor
- C30B 25/10: Heating of the reaction chamber or the substrate
- C30B 25/18: characterised by the substrate
- C30B 29/403: {AIII-nitrides}
- H10P 14/2908: {Nitrides}
- H10P 14/3416: {Nitrides}
- H10P 52/402: {of semiconductor materials}
- H10P 90/12: {Preparing bulk and homogeneous wafers}
- Y10T 428/21: Circular sheet or circular blank
- C30B: SINGLE-CRYSTAL GROWTH (by using ultra-high pressure, e.g. for the formation of diamonds, B01J3/06); UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL (zone-refining of metals or alloys C22B); PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (casting of metals, casting of other substances by the same processes or devices B22D; working of plastics B29; modifying the physical structure of metals or alloys C21D, C22F); SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (for producing semiconductor devices or parts thereof H10); APPARATUS THEREFOR
- B28D: WORKING STONE OR STONE-LIKE MATERIALS
- C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04)
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

Reducing the microvoid (MV) density in AlN ameliorates numerous problems related to cracking during crystal growth, etch pit generation during the polishing, reduction of the optical transparency in an AlN wafer, and, possibly, growth pit formation during epitaxial growth of AlN and/or AlGaN. This facilitates practical crystal production strategies and the formation of large, bulk AlN crystals with low defect densities—e.g., a dislocation density below 104 cm−2 and an inclusion density below 104 cm−3 and/or a MV density below 104 cm−3.

## Claims

### Claim at position 1

1-38. (canceled)

### Claim 39

A method of growing single-crystal AlN, the method comprising:
providing in a crystal growth enclosure a vapor comprising Al and N2; and
depositing the vapor as single-crystalline AlN while pushing the crystal growth enclosure at a rate less than an intrinsic growth rate of the single-crystalline AlN, the single-crystalline AlN having at least one of (i) an optical absorption coefficient of less than 5 cm−1 at all wavelengths in a range spanning 500 nm to 3,000 nm or (ii) an optical absorption coefficient of less than 1 cm−1 at any wavelength in a range spanning 210 nm to 4,500 nm.

### Claim 40 (depends on 39)

The method of claim 39, wherein the single-crystalline AlN has an optical absorption coefficient of less than 5 cm−1 at all wavelengths in a range spanning 500 nm to 3,000 nm.

### Claim 41 (depends on 40)

The method of claim 40, wherein the single-crystalline AlN has an optical absorption coefficient of less than 1 cm−1 at any wavelength in a range spanning 210 nm to 4,500 nm.

### Claim 42 (depends on 39)

The method of claim 39, wherein the single-crystalline AlN has an optical absorption coefficient of less than 1 cm−1 at any wavelength in a range spanning 210 nm to 4,500 nm.

### Claim 43 (depends on 39)

The method of claim 39, wherein the single-crystalline AlN has a microvoid density less than approximately 104 cm−3.

### Claim 44 (depends on 39)

The method of claim 39, further comprising, following deposition, the step of slicing a AlN wafer from the single-crystalline AlN.

### Claim 45 (depends on 44)

The method of claim 44, wherein a cross-sectional area of the AlN wafer is approximately equal to a cross-sectional area of the single-crystalline AlN.

### Claim 46 (depends on 45)

The method of claim 45, wherein the cross-sectional area of the AlN wafer is approximately circular with a diameter of greater than approximately 2 cm.

### Claim 47 (depends on 44)

The method of claim 44, further comprising the step of annealing the AlN wafer at a temperature greater than approximately 2000° C. and a pressure greater than approximately 35 bar.

### Claim 48 (depends on 39)

The method of claim 39, wherein a partial pressure of N2 is greater than a stoichiometric pressure relative to the Al in the crystal growth enclosure while depositing the vapor.

### Claim 49 (depends on 39)

The method of claim 39, wherein a concentration of oxygen in the vapor is less than 300 ppm and a concentration of hydrogen is less than 0.5%.

### Claim 50 (depends on 39)

The method of claim 39, wherein the crystal growth enclosure comprises tungsten and a growth temperature is less than approximately 2350° C.

### Claim 51 (depends on 1)

The method of claim 1, wherein the crystal growth enclosure comprises at least one of tantalum and carbon, and a growth temperature is less than approximately 2750° C.

### Claim 52 (depends on 1)

The method of claim 1, wherein a temperature gradient of greater than approximately 5° C./cm and less than approximately 100° C./cm is maintained along a length of the crystal growth enclosure while depositing the vapor.