# US 12,224,172 B2 · Group III nitride substrate with oxygen gradient, method of making, and method of use

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- Number: US 12,224,172 B2
- Document ID: US12224172B2
- Status: Granted
- Kind: B2
- Application number: 18/072,684
- Filed: 2022-11-30
- Published: 2023-06-01
- Granted: 2025-02-11
- Earliest claimed: 2021-12-01
- Assignees: SLT Technologies, Inc.
- Applicants: SLT Technologies, Inc.
- Inventors: Mark P. D'Evelyn; Keiji Fukutomi; Drew W. Cardwell; David N. Italiano; Chiaki Domoto
- Web page: https://patentgrep.com/patent/US12224172B2

## CPC

- H10P 14/2908: {Nitrides}
- C30B 29/406: {Gallium nitride}
- H10P 14/2926: {Crystal orientations}
- H10P 14/3456: {Polycrystalline}
- C30B 7/105: {using ammonia as solvent, i.e. ammonothermal processes}
- H10P 14/24: using chemical vapour deposition [CVD]
- H10P 14/272: {using mask materials other than SiO2 or SiN}
- H10P 14/276: {Lateral overgrowth}
- H10P 14/3416: {Nitrides}
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- 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

## Abstract

Embodiments of the present disclosure include techniques related to techniques for processing materials for manufacture of group-III metal nitride and gallium based substrates. More specifically, embodiments of the disclosure include techniques for substrates with a controlled oxygen gradient using a combination of processing techniques. Merely by way of example, the disclosure can be applied to growing crystals of GaN, AlN, InN, InGaN, AlGaN, and AlInGaN, and others for manufacture of bulk or patterned substrates. Such bulk or patterned substrates can be used for a variety of applications including optoelectronic and electronic devices, lasers, light emitting diodes, solar cells, photo electrochemical water splitting and hydrogen generation, photodetectors, integrated circuits, and transistors, and others.

## Claims

### Claim 1

A free-standing crystal, comprising a group III metal and nitrogen, wherein the free-standing crystal comprises:
a wurtzite crystal structure;
a first surface having a maximum dimension greater than 40 millimeters in a first direction and a crystallographic orientation within 10 degrees of (0 0 0 1); and
a second surface on the opposite side of the crystal from the first surface, wherein a separation between the first surface and the second surface is between about 200 micrometers and about 2000 micrometers,
wherein an average oxygen concentration within a depth of 2 to 10 micrometers from the first surface, measured at at least four regions, is between 1×1016 cm−3 and 5×1019 cm−3 and is greater, by a factor between about 1.1 and about 10, than the average oxygen concentration within a depth of 2 to 10 micrometers from the second surface, measured at at least four regions, as quantified by calibrated secondary ion mass spectrometry.

### Claim 2 (depends on 1)

The free-standing crystal of claim 1, wherein the average oxygen concentration within a depth of 2 to 10 micrometers on the first surface is greater, by a factor between about 1.1 and about 3, than the average oxygen concentration within a depth of 2 to 10 micrometers on the second surface, as quantified by calibrated secondary ion mass spectrometry.

### Claim 3 (depends on 1)

The free-standing crystal of claim 1, wherein the crystal further comprises an impurity concentration of H greater than 1017 cm−3, and an impurity concentration of at least one of Li, Na, K, F, Cl, Br, and I greater than 1015 cm−3, as quantified by calibrated secondary ion mass spectrometry within a depth of 2 to 10 micrometers on the first surface, measured at at least four regions.

### Claim 4 (depends on 1)

The free-standing crystal of claim 1, wherein the first surface is characterized by an average impurity concentrations of:
hydrogen (H) between 1×1016 cm−3 and 8×1019 cm−3; and
at least one of fluorine (F) and chlorine (Cl) between 1×1015 cm−3 and 1×1019 cm−3.

### Claim 5 (depends on 1)

The free-standing crystal of claim 1, wherein the first surface is characterized by impurity concentrations of:
hydrogen (H) between 1×1016 cm−3 and 8×1019 cm−3; and
at least one of sodium (Na) and potassium (K) between 3×1015 cm−3 and 1×1018 cm3.

### Claim 6 (depends on 3)

The free-standing crystal of claim 3, wherein a ratio of the impurity concentration of H to an impurity concentration of O is between about 0.3 and about 10.

### Claim 7 (depends on 6)

The free-standing crystal of claim 6, wherein a ratio of the impurity concentration of H to an impurity concentration of O is between about 0.4 and about 5.

### Claim 8 (depends on 4)

The free-standing crystal of claim 4, wherein a ratio of the impurity concentration of F to an impurity concentration of O is between about 0.05% and about 10%.

### Claim 9 (depends on 4)

The free-standing crystal of claim 4, wherein a ratio of the impurity concentration of F to an impurity concentration of O is between about 0.1% and about 6%.

### Claim 10 (depends on 4)

The free-standing crystal of claim 4, wherein a ratio of the impurity concentration of F to an impurity concentration of O is between about 0.2% and about 1%.

### Claim 11 (depends on 1)

The free-standing crystal of claim 1, wherein the average oxygen concentration on the second surface is above about 1×1018 cm−3.

### Claim 12 (depends on 1)

The free-standing crystal of claim 1, wherein an oxygen gradient, defined as a difference between the average oxygen concentration within a depth of 2 to 10 micrometers on the first surface and the average oxygen concentration within a depth of 2 to 10 micrometers on the second surface divided by a separation distance of between the first surface and the second surface, is between about 1×1021 cm−4 and about 5×1016 cm−4.

### Claim 13 (depends on 12)

The free-standing crystal of claim 12, wherein the oxygen gradient is between about 5×1020 cm−4 and about 2×1017 cm−4.

### Claim 14 (depends on 12)

The free-standing crystal of claim 12, wherein the oxygen gradient is between about 2×1020 cm−4 and about 1×1018 cm−4.

### Claim 15 (depends on 1)

The free-standing crystal of claim 1, wherein the first surface and the second surface are substantially free of implantation damage or plasma damage to a depth of about 10 micrometers.

### Claim 16 (depends on 1)

The free-standing crystal of claim 1, wherein the first surface has a maximum dimension greater than 90 millimeters in the first direction.

### Claim 17 (depends on 1)

The free-standing crystal of claim 1, wherein the separation between the first surface and the second surface is between about 250 micrometers and about 1000 micrometers.

### Claim 18 (depends on 1)

The free-standing crystal of claim 1, wherein the separation between the first surface and the second surface is characterized by a total thickness variation below about 20 micrometers.

### Claim 19 (depends on 1)

The free-standing crystal of claim 1, wherein a variation in miscut angle across the first surface is less than about 0.1 degree in each of two orthogonal crystallographic directions.

### Claim 20 (depends on 1)

The free-standing crystal of claim 1, wherein a root-mean-square surface roughness of the first surface, as measured over an area of at least 10 μm×10 μm, is less than about 0.1 nanometer.