# US 8,147,991 B2 · One hundred millimeter single crystal silicon carbide wafer

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- Number: US 8,147,991 B2
- Document ID: US8147991B2
- Status: Granted
- Kind: B2
- Application number: 12/772,254
- Filed: 2010-05-03
- Published: 2011-02-03
- Granted: 2012-04-03
- Earliest claimed: 2002-06-24
- Assignees: Cree, Inc.
- Inventors: Jason Ronald Jenny; David Phillip Malta; Hudson McDonald Hobgood; Stephan Georg Mueller; Mark Brady; Robert Tyler Leonard; Adrian Powell; Valeri F. Tsvetkov
- Web page: https://patentgrep.com/patent/US8147991B2

## CPC

- C30B 29/36: Carbides
- C30B 23/00: Single-crystal growth by condensing evaporated or sublimed materials
- C30B 23/025: {characterised by the substrate}
- C30B 33/00: After-treatment of single crystals or homogeneous polycrystalline material with defined structure (C30B31/00 takes precedence)
- H10P 95/90: Thermal treatments, e.g. annealing or sintering
- Y10T 117/10: Apparatus
- Y10T 117/1004: with means for measuring, testing, or sensing
- Y10T 117/1016: with means for treating single-crystal [e.g., heat treating]
- Y10T 428/21: Circular sheet or circular blank
- Y10T 428/31: Surface property or characteristic of web, sheet or block
- 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
- 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

A method is disclosed for producing a high quality bulk single crystal of silicon carbide in a seeded growth system by reducing the separation between a silicon carbide seed crystal and a seed holder until the conductive heat transfer between the seed crystal and the seed holder dominates the radiative heat transfer between the seed crystal and the seed holder over substantially the entire seed crystal surface that is adjacent the seed holder.

## Claims

### Claim 1

A silicon carbide wafer comprising:
a single polytype single crystal;
a diameter greater than three inches;
a resistivity greater than 10,000 ohm-cm;
a micropipe density less than 200 cm−2; and
a combined concentration of shallow level dopants less than 5E16 cm−3.

### Claim 2 (depends on 1)

A wafer according to claim 1 having a diameter of about 100 mm.

### Claim 3 (depends on 1)

A wafer according to claim 1 having less than 100 micropipes per square centimeter.

### Claim 4 (depends on 1)

A wafer according to claim 1 having less than 30 micropipes per square centimeter.

### Claim 5 (depends on 1)

A wafer according to claim 1 having less than 15 micropipes per square centimeter.

### Claim 6 (depends on 1)

A wafer according to claim 1 having less than five micropipes per square centimeter.

### Claim 7 (depends on 1)

An on-axis silicon carbide wafer according to claim 1.

### Claim 8 (depends on 1)

An off-axis silicon carbide wafer according to claim 1.

### Claim 9 (depends on 8)

A silicon carbide wafer according to claim 8 wherein the amount of off-axis orientation is selected from the group consisting of 8°, 4°, and 3.5°.

### Claim 10 (depends on 1)

A wafer according to claim 1 wherein said polytype is selected from the group consisting of the 3C, 4H, 6H and 15R polytypes of silicon carbide.

### Claim 11 (depends on 1)

A wafer according to claim 1 further comprising an epitaxial layer.

### Claim 12 (depends on 11)

A wafer and epitaxial layer according to claim 11 wherein the epitaxial layer is selected from the group consisting of silicon carbide and Group III nitrides.

### Claim 13 (depends on 12)

A device that incorporates the wafer and epitaxial layer according to claim 12.

### Claim 14 (depends on 13)

A device according to claim 13 selected from the group consisting of FET's, MOSFET's, JFET's, MESFET's, HFET's, HEMT's, extended drain MOSFET's, and lateral DMOS transistors.

### Claim 15 (depends on 1)

A wafer according to claim 1 having a concentration of nitrogen atoms less than about 2×1015 cm−3.

### Claim 16 (depends on 1)

A wafer according to claim 1 wherein the concentration of vanadium is less than 1×1014 cm−3.

### Claim 17 (depends on 1)

A wafer according to claim 1 having a resistivity of at least 50,000 ohm-cm at room temperature.

### Claim 18 (depends on 1)

A wafer according to claim 1 having a concentration of point defects that does not exceed 5×1017 cm−3.

### Claim 19 (depends on 1)

A wafer according to claim 1 comprising:
donor dopants, acceptor dopants, and intrinsic point defects in said silicon carbide single crystal;
wherein the number of dopants of a first conductivity type is greater than the number of dopants of a second conductivity type;
the number of intrinsic point defects in said silicon carbide crystal that act to compensate the predominating first type dopant is greater than the numerical difference by which said first type of dopant predominates over said second type of dopant; and
the concentration of transition elements is less than 1×1016 cm−3.

### Claim 20 (depends on 19)

A wafer according to claim 19 wherein said first type dopants are donors, said second type dopants are acceptors and said intrinsic point defects act as acceptors.

### Claim 21 (depends on 20)

A wafer according to claim 20 wherein said acceptors include boron.

### Claim 22 (depends on 19)

A wafer according to claim 19 wherein the concentration of vanadium is less than 1×1014 cm−3.

### Claim 23 (depends on 1)

A wafer according to claim 1 comprising:
nitrogen; and
at least one acceptor element having an electronic energy level of between 0.3 and 1.4 eV relative to the valence band of mono-crystalline silicon carbide;
said at least one acceptor element being present in an amount that over compensates the nitrogen and pins the Fermi level of said silicon carbide substrate to the electronic energy level of said at least one acceptor element.

### Claim 24 (depends on 1)

A wafer according to claim 1 comprising:
an amount of electrically active nitrogen;
an amount of electrically active point defects that act as acceptors; and
an amount at least one acceptor element having an electronic energy level of between 0.3 and 1.4 eV relative to the valence band of mono-crystalline silicon carbide;
wherein the combined amount of said acceptor element and said point defects is greater than said amount of electrically active nitrogen and pins the Fermi level of said silicon carbide single crystal to the electronic energy level of said at least one acceptor element.

### Claim 25 (depends on 1)

A wafer according to claim 1 comprising:
non-intentionally introduced nitrogen;
scandium; and
boron; and wherein
the concentration of nitrogen is greater than the concentration of scandium; and
the concentration of boron is sufficient for the sum concentration of boron and scandium to overcompensate the nitrogen, and pin the Fermi level of said silicon carbide to the level of said scandium.