# US 11,441,237 B2 · RAMO4 substrate and method of manufacture thereof, and group III nitride semiconductor

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- Number: US 11,441,237 B2
- Document ID: US11441237B2
- Status: Granted
- Kind: B2
- Application number: 16/691,542
- Filed: 2019-11-21
- Published: 2020-06-11
- Granted: 2022-09-13
- Earliest claimed: 2018-12-10
- Assignees: Panasonic Intellectual Property Management Co., Ltd.
- Applicants: Panasonic Intellectual Property Management Co., Ltd.
- Inventors: Naoya Ryoki; Kentaro Miyano; Masaki Nobuoka; Akihiko Ishibashi
- Web page: https://patentgrep.com/patent/US11441237B2

## CPC

- C30B 29/26: with formula BMe2O4, wherein B is Mg, Ni, Co, Al, Zn, or Cd and Me is Fe, Ga, Sc, Cr, Co, or Al
- C30B 15/203: {the relationship of pull rate (v) to axial thermal gradient (G)}
- C30B 15/22: Stabilisation or shape controlling of the molten zone near the pulled crystal; Controlling the section of the crystal
- C30B 25/18: characterised by the substrate
- C30B 25/183: {being provided with a buffer layer, e.g. a lattice matching layer}
- C30B 29/406: {Gallium nitride}
- H10D 62/824: comprising only Group III-V materials heterojunctions, e.g. GaN/AlGaN heterojunctions
- H10D 62/8503: {Nitride Group III-V materials, e.g. AlN or GaN}
- H10P 14/2921: {being crystalline insulating materials}
- H10P 14/3216: {Nitrides}
- H10P 14/24: using chemical vapour deposition [CVD]
- H10P 14/3416: {Nitrides}
- 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
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10

## Abstract

A RAMO4 substrate that does not easily crack during or after the formation of group III nitride crystal includes a single crystal represented by general formula RAMO4 (wherein R represents one or more trivalent elements selected from the group consisting of Sc, In, Y, and lanthanoid elements, A represents one or more trivalent elements selected from the group consisting of Fe(III), Ga, and Al, and M represents one or more divalent elements selected from the group consisting of Mg, Mn, Fe(II), Co, Cu, Zn, and Cd). The RAMO4 substrate has a crystal plane with a curvature radius r of 52 m or more, and a square value of correlation coefficient ρ of 0.81 or more. The curvature radius r is calculated as an absolute value from X-ray peak position ωi and measurement position Xi after the measurements of X-ray peak positions ωi at a plurality of positions Xi lying on a straight line passing through the center of the RAMO4 substrate. The correlation coefficient ρ is a measure of correlation between ω and measurement position Xi.

## Claims

### Claim 1

A RAMO4 substrate comprising a single crystal represented by general formula RAMO4, wherein R represents one or more trivalent elements selected from the group consisting of Sc, In, Y, and lanthanoid elements, A represents one or more trivalent elements selected from the group consisting of Fe(III), Ga, and Al, and M represents one or more divalent elements selected from the group consisting of Mg, Mn, Fe(II), Co, Cu, Zn, and Cd,
the RAMO4 substrate having a crystal plane with an absolute value of a curvature radius r of 52 m or more, and a square value of correlation coefficient p of 0.81 or more,
wherein the curvature radius r is calculated from a regression line obtained from a relationship between X-ray peak position wi and position Xi after the X-ray peak position wi is specified in a diffraction spectrum of an X-ray rocking curve measured at each of a plurality of positions Xi (i=1, 2, 3, . . . , n) lying on a straight line passing through a center of a surface of the RAMO4 substrate,
wherein the X-ray peak position wi is expressed as an angular position,
wherein the relationship between the X-ray peak position wi and the position Xi is determined by plotting the X-ray peak position wi versus the position Xi in a graph,
wherein each of the plurality of positions Xi lies on a different point on the straight line,
wherein the square value of correlation coefficient p is calculated from the X-ray peak position ωi, the position Xi, and the number n of the positions Xi, using the following formula,
ρ
=
1
n
⁢
∑
i
=
1
n
⁢
(
Xi
-
X
_
)
⁢
(
ω
⁢
⁢
i
-
ω
_
)
1
n
⁢
∑
i
=
1
n
⁢
(
Xi
-
X
_
)
2
⁢
1
n
⁢
∑
i
=
1
n
⁢
(
ω
⁢
⁢
i
-
ω
_
)
2
wherein ω represents a mean value of wi expressed as
ω
_
=
∑
i
=
1
n
⁢
ω
⁢
⁢
i
n
,
X represents a mean value of Xi expressed as
X
_
=
∑
i
=
1
n
⁢
Xi
n
,
and n represents a natural number larger than or equal to 2,
wherein, when the regression line is represented by ω=aX+b, a and b are represented by the following formulae,
a
=
∑
i
=
1
n
⁢
{
(
Xi
-
X
_
)
⁢
(
ω
⁢
⁢
i
-
ω
_
)
}
∑
i
=
1
n
⁢
(
Xi
-
X
_
)
2
b
=
ω
_
-
a
⁢
⁢
X
_
where ω represents the mean value of ωi, X represents the mean value of Xi, and n represents the number of the positions Xi, and
wherein the curvature radius r is represented by the following formula,
r
=
a
⁢
180
π
.

### Claim 2 (depends on 1)

The RAMO4 substrate according to claim 1, wherein R is Sc, A is Al, and M is Mg in the general formula RAMO4.

### Claim 3 (depends on 1)

The RAMO4 substrate according to claim 1, which has a thickness in a range of from 100 μm to 1,000 μm.

### Claim 4 (depends on 1)

The RAMO4 substrate according to claim 1, which has a diameter in a range of from 25 mm to 200 mm.

### Claim 5 (depends on 2)

The RAMO4 substrate according to claim 2, which has a thickness in a range of from 100 μm to 1,000 μm.

### Claim 6 (depends on 1)

A group III nitride semiconductor comprising:
the RAMO4 substrate of claim 1;
a buffer layer disposed on an epitaxial growth surface forming one surface of the RAMO4 substrate; and
a group III nitride crystal disposed on the buffer layer.

### Claim 7 (depends on 6)

The group III nitride semiconductor according to claim 6, wherein the buffer layer is an amorphous, monocrystalline, or polycrystalline layer formed of a compound represented by InAlGaN.

### Claim 8 (depends on 6)

The group III nitride semiconductor according to claim 6, wherein the group III nitride crystal is GaN or AIN.