# US 11,078,596 B2 · Method for evaluating quality of SiC single crystal body and method for producing silicon carbide single crystal ingot using the same

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- Number: US 11,078,596 B2
- Document ID: US11078596B2
- Status: Granted
- Kind: B2
- Application number: 16/306,129
- Filed: 2018-03-29
- Published: 2020-01-09
- Granted: 2021-08-03
- Earliest claimed: 2017-03-30
- Assignees: Showa Denko K.K.
- Applicants: Showa Denko K.K.
- Inventors: Masashi Nakabayashi; Shoji Ushio
- Web page: https://patentgrep.com/patent/US11078596B2

## CPC

- C30B 23/002: {Controlling or regulating}
- G01N 23/207: Diffractometry using detectors, e.g. using a probe in a central position and one or more displaceable detectors in circumferential positions
- C30B 29/36: Carbides
- G01N 23/20: by using diffraction of the radiation by the materials, e.g. for investigating crystal structure; by using scattering of the radiation by the materials, e.g. for investigating non-crystalline materials; by using reflection of the radiation by the materials
- G01N 23/2076: {for spectrometry, i.e. using an analysing crystal, e.g. for measuring X-ray fluorescence spectrum of a sample with wavelength-dispersion, i.e. WDXFS}
- G01N 2223/60: Specific applications or type of materials
- 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
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

A method for evaluating the quality of a SiC single crystal by a non-destructive and simple method; and a method for producing a SiC single crystal ingot with less dislocation and high quality with good reproducibility utilizing the same. The method for evaluating the quality of a SiC single crystal body is based on the graph of a second polynomial equation obtained by differentiating a first polynomial equation, the first polynomial equation approximating the relation between a peak shift value and a position of the measurement point and the peak shift value being obtained by an X-ray rocking curve measurement. The method for producing a SiC single crystal ingot manufactures a SiC single crystal ingot by a sublimation recrystallization method using, as a seed crystal, the SiC single crystal body evaluated by the evaluation method.

## Claims

### Claim 1

A method for evaluating the quality of a SiC single crystal body composed of a disc-shaped silicon carbide single crystal,
which comprises
conducting an X-ray rocking curve measurement of a main surface of the SiC single crystal body on a predetermined diffraction surface;
obtaining an angle Ω at a plurality of measurement points Pn on a diameter of the main surface, wherein the Ω is an angle between an X-ray incident direction and the main surface when a diffraction peak is exhibited; and
calculating the difference (Ωn−Ω0) as a respective peak shift value, in which Ω0 is an angle at a certain reference measurement point P0 and Ωn is an angle at a measurement point Pn other than P0 among these measurement points;
obtaining a relation between the location of the measurement point Pn(X) on the diameter of the main surface and the peak shift value (Y) as a first polynomial equation;
linearly differentiating the first polynomial equation to obtain a second polynomial equation, and evaluating the quality of the SiC single crystal body based on these polynomial equations.

### Claim 2 (depends on 1)

The method for evaluating the quality of a SiC single crystal body according to claim 1, wherein, when the second polynomial equation is expressed as a graph in which the Y axis indicates the inclination of the first polynomial equation and the X axis indicates the position of the measurement point Pn on the diameter of the main surface of the SiC single crystal body, the quality is evaluated by determining whether the graph of the second polynomial equation passes Y=0 or not.

### Claim 3 (depends on 2)

The method for evaluating the quality of a SiC single crystal body according to claim 2, wherein the quality is evaluated by determining whether a graph representing the second polynomial equation passes Y=0 twice or not.

### Claim 4 (depends on 2)

The method for evaluating the quality of a SiC single crystal body according to claim 2, wherein the quality is evaluated by determining whether a function of a peak shift value (Y) in the first polynomial equation has a local maximum value or a local minimum value.

### Claim 5 (depends on 1)

The method for evaluating the quality of a SiC single crystal body according to claim 1, wherein, when the second polynomial equation is expressed as a graph in which the Y axis indicates the inclination of the first polynomial equation and the X axis indicates the position of the measurement point on the diameter of the main surface of the SiC single crystal body, the quality is evaluated by a difference between a maximum value and a minimum value of the inclination (Y).

### Claim 6 (depends on 1)

The method for evaluating the quality of a SiC single crystal body according to claim 1, wherein the degree of the first polynomial equation is 4 or more.

### Claim 7 (depends on 1)

The method for evaluating the quality of a SiC single crystal body according to claim 1, wherein the reference measurement point P0 is a center point of the main surface of the SiC single crystal body.

### Claim 8 (depends on 1)

The method for evaluating the quality of a SiC single crystal body according to claim 1, which comprises determining a basal surface dislocation density of the SiC single crystal body.

### Claim 9

A method for producing a silicon carbide single crystal ingot which comprises growing a silicon carbide single crystal on a seed crystal by a sublimation recrystallization method,
wherein
an X-ray rocking curve measurement of a main surface of a SiC single crystal body composed of a disc-shaped silicon carbide single crystal is previously conducted on a predetermined diffraction surface;
an angle Ω is obtained at a plurality of measurement points Pn on a diameter of the main surface, wherein the Ω is an angle formed between an X-ray incident direction and the main surface when a diffraction peak is exhibited;
the difference Ωn−Ω0 is calculated as a respective peak shift value, in which Ω0 is an angle at a certain reference measurement point P0 and Ωn is an angle at a measurement point Pn other than P0 among these measurement points;
a relationship between the position of the measurement point Pn (X) on the diameter of the main surface and the peak shift value (Y) is obtained as a first polynomial equation;
the first polynomial equation is linearly differentiated to obtain a second polynomial equation, and when thus obtained second polynomial equation is expressed as a graph in which the Y axis indicates the inclination of the first polynomial equation and the X axis indicates the position of the measurement point Pn on the diameter of the main surface of the SiC single crystal body, the SiC single crystal body whose graph does not pass Y=0 twice or more is used as the seed crystal.