WO2016002707A1 - Gallium oxide substrate and production method therefor - Google Patents

Gallium oxide substrate and production method therefor Download PDF

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Publication number
WO2016002707A1
WO2016002707A1 PCT/JP2015/068661 JP2015068661W WO2016002707A1 WO 2016002707 A1 WO2016002707 A1 WO 2016002707A1 JP 2015068661 W JP2015068661 W JP 2015068661W WO 2016002707 A1 WO2016002707 A1 WO 2016002707A1
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gallium oxide
oxide substrate
plane
cylindrical block
main surface
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PCT/JP2015/068661
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French (fr)
Japanese (ja)
Inventor
優 山岡
建和 増井
嘉克 森島
康孝 阿部
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株式会社タムラ製作所
株式会社光波
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Publication of WO2016002707A1 publication Critical patent/WO2016002707A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
    • B23H9/00—Machining specially adapted for treating particular metal objects or for obtaining special effects or results on metal objects
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B27/00—Other grinding machines or devices
    • B24B27/06—Grinders for cutting-off
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/16—Oxides
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B33/00—After-treatment of single crystals or homogeneous polycrystalline material with defined structure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B37/00—Lapping machines or devices; Accessories

Definitions

  • the present invention relates to a gallium oxide substrate and a manufacturing method thereof.
  • Patent Document 1 it intersects at 90 ⁇ 5 degrees with respect to (100) of the gallium oxide substrate, and also intersects at 90 ⁇ 5 degrees with respect to the main surface constituted by the surface excluding (100).
  • a first orientation flat formed on the peripheral edge of the main surface 15 is formed within an error of ⁇ 5 degrees in rotation angle with a normal passing through the center point of the surface as the rotation axis, and further, the main orientation of the gallium oxide substrate is formed.
  • a second orientation flat is formed at the periphery of the other main surface with the center point of the surface as the symmetry point.
  • defects generated in the gallium oxide substrate can be removed by forming the first and second orientation flats on the gallium oxide substrate obtained by the circular punching of the gallium oxide single crystal by the core drill. Yes.
  • a defect-free gallium oxide substrate can be obtained by performing a circle punching process after performing a process for forming the first and second orientation flats on the gallium oxide single crystal.
  • An object of the present invention is to provide a gallium oxide substrate manufacturing method capable of obtaining a gallium oxide substrate from a gallium oxide single crystal ingot while suppressing the occurrence of defects, and a structure capable of suppressing the occurrence of defects during processing. It is to provide a gallium oxide substrate having the same.
  • One embodiment of the present invention provides a method for producing a gallium oxide substrate according to [1] to [5] in order to achieve the above object.
  • the main surface of the gallium oxide substrate is a surface different from the (100) surface, and the orientation flats are a first orientation flat and a second orientation flat provided at opposite positions on the side surface of the cylindrical block, respectively.
  • the first orientation flat and the second orientation flat are along a direction within ⁇ 2 ° with respect to a direction parallel to the intersection line between the main surface of the gallium oxide substrate and the (100) plane.
  • the gallium oxide substrate according to [2], wherein the gallium oxide substrate is provided with a length of 6 mm or more and at least one of peripheral grinding, beveling, polishing, and cleaning is applied to the gallium oxide substrate.
  • another aspect of the present invention provides a method for producing a gallium oxide substrate according to [6] below.
  • a manufacturing method of a gallium oxide substrate capable of obtaining a gallium oxide substrate from a gallium oxide single crystal ingot while suppressing the occurrence of defects, and a structure capable of suppressing the occurrence of defects during processing.
  • a gallium oxide substrate can be provided.
  • FIG. 1A is a perspective view schematically illustrating a state of circular punching of a gallium oxide ingot according to an embodiment.
  • FIG. 1B is a perspective view of a cylindrical block of a gallium oxide single crystal cut out by a circular punching process of a gallium oxide ingot.
  • FIG. 2A is a side view of a cylindrical block.
  • FIG. 2B is a side view of a gallium oxide substrate obtained by slicing a cylindrical block.
  • FIG. 3 is a plan view of the gallium oxide substrate.
  • FIG. 4A is a diagram schematically illustrating how a crack is generated in a gallium oxide substrate.
  • FIG. 4B is a diagram schematically illustrating how a crack is generated in the gallium oxide substrate.
  • FIG. 1A is a perspective view schematically showing a state of circular cutting of the gallium oxide ingot 2 according to the embodiment.
  • FIG. 1B is a perspective view of a cylindrical block 20 of a gallium oxide single crystal cut out by circular cutting of the gallium oxide ingot 2.
  • the circular cutting of the gallium oxide ingot 2 is performed by wire electric discharge machining using the wire electrode 1 as an electrode.
  • the wire electrode 1 In a state where a discharge is generated between the wire electrode 1 and the gallium oxide ingot 2, the wire electrode 1 is turned into the gallium oxide ingot 2 along the contour shape of the cylindrical block 20 as shown in FIGS. Move against. A portion of the gallium oxide ingot 2 adjacent to the wire electrode 1 is melted by electric discharge, and the cylindrical block 20 is cut out.
  • the wire electrode 1 is made of a conductive material such as brass or tungsten, and has a diameter of 0.02 to 0.36 mm, for example.
  • the gallium oxide ingot 2 to be processed also has conductivity, a discharge can be generated between the wire electrode 1 and the gallium oxide ingot 2.
  • the gallium oxide ingot 2 is, for example, a flat gallium oxide single crystal ingot grown by the EFG method.
  • the gallium oxide ingot 2 is separated from the seed crystal using a diamond blade, for example, after growth, after annealing for the purpose of relaxing thermal strain during growth and improving electrical characteristics.
  • the radial cross section (cross section parallel to the radial direction) of the cylindrical block 20 is a plane different from the (100) plane of the gallium oxide single crystal, for example, the ( ⁇ 201) plane, the (101) plane, or the (001) plane. Matches.
  • the gallium oxide single crystal has a high cleavage property in the (100) plane
  • the cylindrical block 20 is cut out from the gallium oxide ingot 2. , Defects such as cracks are likely to occur on the (100) plane.
  • the inventors of the present application have intensively studied to suppress the occurrence of this defect, and as a result, found that the occurrence of a defect in a cylindrical block can be suppressed by performing a circle punching process by wire electric discharge machining.
  • defects are generated in the cylindrical block when coring with a core drill or processing with a grinder. Although it is easy, generation
  • the gallium oxide ingot 2 is punched by wire electric discharge machining, the occurrence of defects such as cracks in the cylindrical block 20 can be suppressed.
  • the main surface becomes ( A gallium oxide substrate having a ⁇ 201) plane, a (101) plane, or a (001) plane can be obtained.
  • the main surface of the gallium oxide substrate is the ( ⁇ 201) surface or the (101) surface, the GaN-based semiconductor layer is easily epitaxially grown on the main surface, so that it can be used as an excellent substrate for a GaN-based semiconductor device.
  • the main surface of the gallium oxide substrate is the (001) surface, it is possible to homoepitaxially grow a high-quality Ga 2 O 3 based semiconductor layer on the main surface, so that it can be used as an excellent substrate for electronic devices. Can do.
  • the orientation flat of the cylindrical block 20 is the orientation flat of the gallium oxide substrate when the cylindrical block 20 is sliced to form a gallium oxide substrate.
  • the orientation flats 21 and 22 shown in FIG. 1B are examples of orientation flats, and there may be only one orientation flat.
  • the orientation flat can be formed on the cylindrical block 20 at the same time as the circular punching process, there is a possibility that defects are generated in the cylindrical block 20 as compared with the case where the circular punching process and the formation of the orientation flat are performed in separate processes. Can be made lower.
  • the orientation flat cannot be formed at the same time. It is necessary to form an orientation flat.
  • the orientation flat is formed using, for example, a slicing machine.
  • the single crystal has a highly cleaved surface, defects such as chipping may occur.
  • the orientation flats formed on the cylindrical block 20 are preferably the orientation flats 21 and 22 shown in FIGS. 1A and 1B. This is because by providing the orientation flats 21 and 22 on the gallium oxide substrate obtained from the cylindrical block 20, it is possible to suppress generation of defects in a process such as polishing. Details thereof will be described later. Orientation flats 21 and 22 are respectively provided at opposing positions on the side surface of the cylindrical block 20.
  • FIG. 2A is a side view of the cylindrical block 20
  • FIG. 2B is a side view of a gallium oxide substrate 30 obtained by slicing the cylindrical block 20.
  • FIG. 1A is a side view of the cylindrical block 20
  • FIG. 2B is a side view of a gallium oxide substrate 30 obtained by slicing the cylindrical block 20.
  • the gallium oxide substrate 30 is formed by slicing the cylindrical block 20 along its radial direction (direction perpendicular to the thickness direction). Therefore, the main surface 31 of the gallium oxide substrate 30 coincides with a surface other than the (100) plane, for example, the ( ⁇ 201) plane, the (101) plane, or the (001) plane.
  • the cylindrical block 20 may be sliced along a direction offset by a predetermined angle from the radial direction. Even in this case, the main surface 31 of the gallium oxide substrate 30 is sliced so as to coincide with a surface other than the (100) plane, for example, the ( ⁇ 201) plane, the (101) plane, or the (001) plane.
  • FIG. 3 is a plan view of the gallium oxide substrate 30.
  • the orientation flats 21 and 22 are provided at opposing positions, and are provided along directions within ⁇ 2 ° with respect to a direction parallel to the intersection line of the main surface 31 and the (100) plane. And has a length of 6 mm or more.
  • L2 and L3 in FIG. 3 represent the lengths of the orientation flats 21 and 22, respectively. That is, L2 and L3 are 6 mm or more.
  • L2 or L3 is 16 mm or more which is the length of a general orientation flat.
  • the surfaces of the orientation flats 21 and 22 are preferably perpendicular to the main surface 31 in the same manner as a general orientation flat surface.
  • the gallium oxide substrate 30 has the orientation flats 21 and 22, it is possible to suppress the occurrence of cracking (chipping) due to the force applied to the gallium oxide substrate 30 when performing peripheral grinding, beveling, polishing, or cleaning. The reason will be described below.
  • FIGS. 4A and 4B are diagrams schematically showing how a crack is generated in the gallium oxide substrate 30.
  • FIG. 4A and 4B are a plan view and a cross-sectional view of the gallium oxide substrate 30, respectively.
  • FIG. 4B shows a cross section of the gallium oxide substrate 30 having the main surface 31 of ( ⁇ 201) cut in a direction perpendicular to the b-axis of the gallium oxide single crystal.
  • a crack surface 40 shown in FIGS. 4A and 4B is a (100) surface where cracks are generated.
  • the length L0 of the edge on the main surface 31 is 5 mm or less due to external force applied in these steps.
  • Crack surface 40 is likely to occur.
  • the edge of the crack surface 40 on the main surface 31 is parallel to the line of intersection of the main surface 31 and the (100) surface.
  • the orientation flat 21 is provided along a direction within ⁇ 2 ° with respect to a direction parallel to the intersection line of the main surface 31 and the (100) plane, and has a length of 6 mm or more.
  • the cylindrical block 20 is sliced to a thickness of about 1 mm by, for example, a multi-wire saw, and the gallium oxide substrate 30 is obtained.
  • the wire saw is preferably a fixed abrasive type.
  • the slicing speed is preferably about 0.125 to 0.3 mm per minute.
  • annealing is performed on the gallium oxide substrate 30 for the purpose of relaxing processing strain, improving electrical characteristics, and improving permeability.
  • annealing is performed in an oxygen atmosphere when the temperature is raised, and annealing is performed in an inert atmosphere such as a nitrogen atmosphere, an argon atmosphere, or a helium atmosphere while the temperature is maintained after the temperature is raised.
  • the holding temperature is preferably 1400 to 1600 ° C.
  • the outer periphery of the gallium oxide substrate 30 is ground using a diamond grinding wheel until a desired outer size is obtained.
  • the grain size of the grindstone is preferably about # 400 to 1000 (specified by JISB4131). Since the gallium oxide substrate 30 has the orientation flats 21 and 22, the occurrence of cracks in this step is suppressed.
  • the edge of the gallium oxide substrate 30 is beveled (chamfered) at a desired angle. Since the gallium oxide substrate 30 has the orientation flats 21 and 22, the occurrence of cracks in this step is suppressed.
  • the main surface 31 of the gallium oxide substrate 30 is ground to a desired thickness using a diamond grinding wheel.
  • the grain size of the grindstone is preferably about # 800 to 1000 (specified by JISB4131). Since the gallium oxide substrate 30 has the orientation flats 21 and 22, the occurrence of cracks in this step is suppressed.
  • the main surface 31 of the gallium oxide substrate 30 is polished to a desired thickness using a polishing surface plate and diamond slurry.
  • the polishing surface plate is preferably made of a metal or glass material.
  • the particle size of the diamond abrasive grains contained in the diamond slurry is preferably about 0.5 ⁇ m. Since the gallium oxide substrate 30 has the orientation flats 21 and 22, the occurrence of cracks in this step is suppressed.
  • the main gallium oxide substrate 30 The surface 31 is polished.
  • the polishing cloth is preferably made of nylon, silk fiber, urethane or the like. It is preferable to use colloidal silica for the abrasive grains of the slurry. Since the gallium oxide substrate 30 has the orientation flats 21 and 22, the occurrence of cracks in this step is suppressed.
  • the gallium oxide substrate 30 is cleaned. Specifically, for example, ultrasonic cleaning for 3 minutes, ultrasonic cleaning for 3 minutes, ultrasonic cleaning for 3 minutes, cleaning with methanol for 5 minutes, washing with running water for 5 minutes, washing with sulfuric acid for 5 minutes, washing with running water for 5 minutes. Do it sequentially. Since the gallium oxide substrate 30 has the orientation flats 21 and 22, the occurrence of cracks in this step is suppressed.
  • the cylindrical block 20 of a gallium oxide single crystal with few defects can be obtained by performing the circular punching process of the gallium oxide ingot 2 by wire electric discharge machining.
  • a high-quality gallium oxide substrate 30 can be obtained by slicing the cylindrical block 20 of gallium oxide single crystal with few defects.
  • the orientation flat by forming the orientation flat at the same time as the circular punching process, it is possible to suppress the occurrence of defects in the cylindrical block as compared to the case where the orientation flat is formed in a separate process from the circular punching process.
  • orientation flats (orientation flats 21 and 22) satisfying predetermined conditions on the gallium oxide substrate 30
  • generation of cracks when the outer peripheral grinding, beveling, polishing, or cleaning is performed on the gallium oxide substrate 30 is suppressed. be able to.
  • a method of manufacturing a gallium oxide substrate capable of obtaining a gallium oxide substrate from a gallium oxide single crystal ingot while suppressing generation of defects, and a gallium oxide substrate having a structure capable of suppressing generation of defects during processing are provided. To do.

Abstract

Provided are: a gallium oxide substrate production method whereby the occurrence of defects can be reduced and a gallium oxide substrate can be obtained from an ingot of monocrystalline gallium oxide; and a gallium oxide substrate having a structure whereby the occurrence of defects during machining can be reduced. One embodiment of the present invention provides a gallium oxide substrate production method including: a step in which, as a result of wire electrical discharge machining, a cylindrical block (20) of monocrystalline gallium oxide having a cross-section parallel to the diameter direction that is different from the (100) plane is cut out from an ingot (2) of monocrystalline gallium oxide; and a step in which the cylindrical block (20) is sliced and a gallium oxide substrate (30) is obtained.

Description

酸化ガリウム基板及びその製造方法Gallium oxide substrate and manufacturing method thereof
　本発明は、酸化ガリウム基板及びその製造方法に関する。 The present invention relates to a gallium oxide substrate and a manufacturing method thereof.
　従来、コアドリルを用いた酸化ガリウム単結晶の円抜き加工により形成される酸化ガリウム基板のチッピング、クラック、剥離等の欠陥を除去する、又は欠陥の発生を防ぐ技術が知られている（例えば、特許文献１参照）。 Conventionally, a technique for removing defects such as chipping, cracking, and peeling of a gallium oxide substrate formed by circular punching of a gallium oxide single crystal using a core drill, or preventing the occurrence of defects is known (for example, patents). Reference 1).
　特許文献１によれば、酸化ガリウム基板の（１００）に対して９０±５度で交わり、かつ（１００）を除く面で構成される主面に対しても９０±５度で交わり、さらに主面の中心点を通る法線を回転軸として、回転角度にして±５度の誤差内で、主面１５の周縁部に形成された第１のオリエンテーションフラットを形成し、更に酸化ガリウム基板の主面の中心点を対称点にして第２のオリエンテーションフラットを他方の主面周縁に形成する。 According to Patent Document 1, it intersects at 90 ± 5 degrees with respect to (100) of the gallium oxide substrate, and also intersects at 90 ± 5 degrees with respect to the main surface constituted by the surface excluding (100). A first orientation flat formed on the peripheral edge of the main surface 15 is formed within an error of ± 5 degrees in rotation angle with a normal passing through the center point of the surface as the rotation axis, and further, the main orientation of the gallium oxide substrate is formed. A second orientation flat is formed at the periphery of the other main surface with the center point of the surface as the symmetry point.
　コアドリルによる酸化ガリウム単結晶の円抜き加工により得られた酸化ガリウム基板に、これら第１及び第２のオリエンテーションフラットを形成することにより、酸化ガリウム基板に生じた欠陥を除去することができるとされている。また、第１及び第２のオリエンテーションフラットを形成するための加工を酸化ガリウム単結晶に施した後に円抜き加工を行うことにより、欠陥の無い酸化ガリウム基板を得ることができるとされている。 It is said that defects generated in the gallium oxide substrate can be removed by forming the first and second orientation flats on the gallium oxide substrate obtained by the circular punching of the gallium oxide single crystal by the core drill. Yes. In addition, it is said that a defect-free gallium oxide substrate can be obtained by performing a circle punching process after performing a process for forming the first and second orientation flats on the gallium oxide single crystal.
特開２０１３－６７５２４号公報JP 2013-67524 A
　本発明の目的は、欠陥の発生を抑えつつ、酸化ガリウム単結晶のインゴットから酸化ガリウム基板を得ることのできる酸化ガリウム基板の製造方法、及び加工の際の欠陥の発生を抑えることのできる構造を有する酸化ガリウム基板を提供することにある。 An object of the present invention is to provide a gallium oxide substrate manufacturing method capable of obtaining a gallium oxide substrate from a gallium oxide single crystal ingot while suppressing the occurrence of defects, and a structure capable of suppressing the occurrence of defects during processing. It is to provide a gallium oxide substrate having the same.
　本発明の一態様は、上記目的を達成するために、［１］～［５］の酸化ガリウム基板の製造方法を提供する。 One embodiment of the present invention provides a method for producing a gallium oxide substrate according to [1] to [5] in order to achieve the above object.
［１］ワイヤー放電加工により、酸化ガリウム単結晶のインゴットから、径方向に平行な断面が（１００）面と異なる酸化ガリウム単結晶の円柱状ブロックを切り出す工程と、前記円柱状ブロックをスライスして酸化ガリウム基板を得る工程と、を含む、酸化ガリウム基板の製造方法。 [1] A step of cutting a cylindrical block of a gallium oxide single crystal whose cross section parallel to the radial direction is different from the (100) plane from a gallium oxide single crystal ingot by wire electric discharge machining, and slicing the cylindrical block And a step of obtaining a gallium oxide substrate.
［２］前記ワイヤー放電加工により、その側面にオリエンテーションフラットを有する前記円柱状ブロックを切り出す、前記［１］に記載の酸化ガリウム基板の製造方法。 [2] The method for producing a gallium oxide substrate according to [1], wherein the cylindrical block having an orientation flat on a side surface thereof is cut out by the wire electric discharge machining.
［３］前記円柱状ブロックの前記径方向に平行な断面が（－２０１）面、（１０１）面、又は（００１）面である、前記［１］又は［２］に記載の酸化ガリウム基板の製造方法。 [3] The gallium oxide substrate according to [1] or [2], wherein a cross section of the cylindrical block parallel to the radial direction is a (−201) plane, a (101) plane, or a (001) plane. Production method.
［４］前記酸化ガリウム基板の主面は（１００）面と異なる面であり、前記オリエンテーションフラットは、前記円柱状ブロックの側面の対向する位置にそれぞれ設けられる第１のオリエンテーションフラット及び第２のオリエンテーションフラットであり、前記第１のオリエンテーションフラット及び前記第２のオリエンテーションフラットは、前記酸化ガリウム基板の主面と（１００）面との交線に平行な方向を基準として±２°以内の方向に沿って設けられ、６ｍｍ以上の長さを有し、前記酸化ガリウム基板に外周研削、ベベル加工、研磨、洗浄のうちの少なくともいずれか１つを施す、前記［２］に記載の酸化ガリウム基板の製造方法。 [4] The main surface of the gallium oxide substrate is a surface different from the (100) surface, and the orientation flats are a first orientation flat and a second orientation flat provided at opposite positions on the side surface of the cylindrical block, respectively. The first orientation flat and the second orientation flat are along a direction within ± 2 ° with respect to a direction parallel to the intersection line between the main surface of the gallium oxide substrate and the (100) plane. The gallium oxide substrate according to [2], wherein the gallium oxide substrate is provided with a length of 6 mm or more and at least one of peripheral grinding, beveling, polishing, and cleaning is applied to the gallium oxide substrate. Method.
［５］前記酸化ガリウム基板の前記主面が（－２０１）面、（１０１）面、又は（００１）面である、前記［４］に記載の酸化ガリウム基板の製造方法。 [5] The method for manufacturing a gallium oxide substrate according to [4], wherein the main surface of the gallium oxide substrate is a (−201) plane, a (101) plane, or a (001) plane.
　また、本発明の他の態様は、上記目的を達成するために、下記［６］の酸化ガリウム基板の製造方法を提供する。 Moreover, in order to achieve the above object, another aspect of the present invention provides a method for producing a gallium oxide substrate according to [6] below.
［６］酸化ガリウム単結晶からなる酸化ガリウム基板であって、主面が（１００）面と異なる面であり、対向する位置にそれぞれ設けられた、前記主面と（１００）面との交線に平行な方向を基準として±２°以内の方向に沿って設けられ、６ｍｍ以上の長さを有する、２つのオリエンテーションフラットを有する、酸化ガリウム基板。 [6] A gallium oxide substrate made of a gallium oxide single crystal, the main surface being a surface different from the (100) surface, and an intersection line between the main surface and the (100) surface, which are respectively provided at opposing positions. A gallium oxide substrate having two orientation flats having a length of 6 mm or more provided along a direction within ± 2 ° with respect to a direction parallel to the substrate.
　本発明によれば、欠陥の発生を抑えつつ、酸化ガリウム単結晶のインゴットから酸化ガリウム基板を得ることのできる酸化ガリウム基板の製造方法、及び加工の際の欠陥の発生を抑えることのできる構造を有する酸化ガリウム基板を提供することができる。 According to the present invention, there is provided a manufacturing method of a gallium oxide substrate capable of obtaining a gallium oxide substrate from a gallium oxide single crystal ingot while suppressing the occurrence of defects, and a structure capable of suppressing the occurrence of defects during processing. A gallium oxide substrate can be provided.
図１Ａは、実施の形態に係る酸化ガリウムインゴットの円抜き加工の様子を概略的に表す斜視図である。FIG. 1A is a perspective view schematically illustrating a state of circular punching of a gallium oxide ingot according to an embodiment. 図１Ｂは、酸化ガリウムインゴットの円抜き加工により切り出された酸化ガリウム単結晶の円柱状ブロックの斜視図である。FIG. 1B is a perspective view of a cylindrical block of a gallium oxide single crystal cut out by a circular punching process of a gallium oxide ingot. 図２Ａは円柱状ブロックの側面図である。FIG. 2A is a side view of a cylindrical block. 図２Ｂは円柱状ブロックをスライスすることにより得られる酸化ガリウム基板の側面図である。FIG. 2B is a side view of a gallium oxide substrate obtained by slicing a cylindrical block. 図３は、酸化ガリウム基板の平面図である。FIG. 3 is a plan view of the gallium oxide substrate. 図４Ａは、酸化ガリウム基板にクラックが発生する様子を模式的に表す図である。FIG. 4A is a diagram schematically illustrating how a crack is generated in a gallium oxide substrate. 図４Ｂは、酸化ガリウム基板にクラックが発生する様子を模式的に表す図である。FIG. 4B is a diagram schematically illustrating how a crack is generated in the gallium oxide substrate.
〔実施の形態〕
（酸化ガリウムインゴットの円抜き加工工程）
　図１Ａは、実施の形態に係る酸化ガリウムインゴット２の円抜き加工の様子を概略的に表す斜視図である。図１Ｂは、酸化ガリウムインゴット２の円抜き加工により切り出された酸化ガリウム単結晶の円柱状ブロック２０の斜視図である。 Embodiment
(Gallium oxide ingot circle punching process)
FIG. 1A is a perspective view schematically showing a state of circular cutting of the gallium oxide ingot 2 according to the embodiment. FIG. 1B is a perspective view of a cylindrical block 20 of a gallium oxide single crystal cut out by circular cutting of the gallium oxide ingot 2.
　酸化ガリウムインゴット２の円抜き加工は、ワイヤー電極１を電極として用いるワイヤー放電加工により行われる。 The circular cutting of the gallium oxide ingot 2 is performed by wire electric discharge machining using the wire electrode 1 as an electrode.
　ワイヤー電極１と酸化ガリウムインゴット２との間で放電を発生させた状態で、図１Ａ及び図１Ｂに示されるように、円柱状ブロック２０の輪郭形状に沿ってワイヤー電極１を酸化ガリウムインゴット２に対して動かす。酸化ガリウムインゴット２のワイヤー電極１に近接する部分は放電により溶かされ、円柱状ブロック２０が切り出される。 In a state where a discharge is generated between the wire electrode 1 and the gallium oxide ingot 2, the wire electrode 1 is turned into the gallium oxide ingot 2 along the contour shape of the cylindrical block 20 as shown in FIGS. Move against. A portion of the gallium oxide ingot 2 adjacent to the wire electrode 1 is melted by electric discharge, and the cylindrical block 20 is cut out.
　ワイヤー電極１は、黄銅、タングステン等の導電性の材料からなり、例えば、０．０２～０．３６ｍｍの直径を有する。なお、加工対象である酸化ガリウムインゴット２も導電性を有するため、ワイヤー電極１との間で放電を発生させることができる。 The wire electrode 1 is made of a conductive material such as brass or tungsten, and has a diameter of 0.02 to 0.36 mm, for example. In addition, since the gallium oxide ingot 2 to be processed also has conductivity, a discharge can be generated between the wire electrode 1 and the gallium oxide ingot 2.
　酸化ガリウムインゴット２は、例えば、ＥＦＧ法により育成された平板状の酸化ガリウム単結晶のインゴットである。酸化ガリウムインゴット２は、例えば、育成後、育成時の熱歪緩和と電気特性の向上を目的とするアニールが施された後、ダイヤモンドブレードを用いて種結晶と分離される。 The gallium oxide ingot 2 is, for example, a flat gallium oxide single crystal ingot grown by the EFG method. The gallium oxide ingot 2 is separated from the seed crystal using a diamond blade, for example, after growth, after annealing for the purpose of relaxing thermal strain during growth and improving electrical characteristics.
　円柱状ブロック２０の径方向の断面（径方向に平行な断面）は、酸化ガリウム単結晶の（１００）面と異なる面、例えば、（－２０１）面、（１０１）面、又は（００１）面と一致する。 The radial cross section (cross section parallel to the radial direction) of the cylindrical block 20 is a plane different from the (100) plane of the gallium oxide single crystal, for example, the (−201) plane, the (101) plane, or the (001) plane. Matches.
　酸化ガリウムの単結晶は（１００）面において高い劈開性を有するため、円柱状ブロック２０の径方向の断面が（１００）面と異なる場合は、酸化ガリウムインゴット２から円柱状ブロック２０を切り出す際に、（１００）面においてクラック等の欠陥が発生しやすい。 Since the gallium oxide single crystal has a high cleavage property in the (100) plane, when the radial cross section of the cylindrical block 20 is different from the (100) plane, the cylindrical block 20 is cut out from the gallium oxide ingot 2. , Defects such as cracks are likely to occur on the (100) plane.
　本願発明者らは、この欠陥の発生を抑えるべく鋭意研究を重ねた結果、ワイヤー放電加工により円抜き加工を行うことにより、円柱状ブロックにおける欠陥の発生を抑制できることを見出した。具体的には、径方向の断面が（１００）面と異なる酸化ガリウム単結晶の円柱状ブロックを形成するために、コアドリルによるコアリングやグラインダーによる加工を行う場合は円柱状ブロックに欠陥が発生しやすいが、ワイヤー放電加工を行う場合は欠陥の発生を抑えることができる。 The inventors of the present application have intensively studied to suppress the occurrence of this defect, and as a result, found that the occurrence of a defect in a cylindrical block can be suppressed by performing a circle punching process by wire electric discharge machining. Specifically, in order to form a cylindrical block of gallium oxide single crystal having a radial cross-section different from the (100) plane, defects are generated in the cylindrical block when coring with a core drill or processing with a grinder. Although it is easy, generation | occurrence | production of a defect can be suppressed when performing wire electric discharge machining.
　本実施の形態においては、ワイヤー放電加工により酸化ガリウムインゴット２の円抜き加工を行うため、円柱状ブロック２０におけるクラック等の欠陥の発生を抑えることができる。 In this embodiment, since the gallium oxide ingot 2 is punched by wire electric discharge machining, the occurrence of defects such as cracks in the cylindrical block 20 can be suppressed.
　円柱状ブロック２０の径方向の断面が酸化ガリウム単結晶の（－２０１）面、（１０１）面、又は（００１）面と一致する場合、円柱状ブロック２０をスライスすることにより、主面が（－２０１）面、（１０１）面、又は（００１）面である酸化ガリウム基板を得ることができる。酸化ガリウム基板の主面が（－２０１）面又は（１０１）面である場合、主面上にＧａＮ系半導体層がエピタキシャル成長しやすいため、優れたＧａＮ系半導体デバイス用の基板として用いることができる。また、酸化ガリウム基板の主面が（００１）面である場合は、主面上に高品質なＧａ２Ｏ３系半導体層のホモエピタキシャル成長が可能なため、優れた電子デバイス用の基板として用いることができる。 When the cross section in the radial direction of the cylindrical block 20 coincides with the (−201) plane, the (101) plane, or the (001) plane of the gallium oxide single crystal, by slicing the cylindrical block 20, the main surface becomes ( A gallium oxide substrate having a −201) plane, a (101) plane, or a (001) plane can be obtained. When the main surface of the gallium oxide substrate is the (−201) surface or the (101) surface, the GaN-based semiconductor layer is easily epitaxially grown on the main surface, so that it can be used as an excellent substrate for a GaN-based semiconductor device. Further, when the main surface of the gallium oxide substrate is the (001) surface, it is possible to homoepitaxially grow a high-quality Ga 2 O 3 based semiconductor layer on the main surface, so that it can be used as an excellent substrate for electronic devices. Can do.
　また、ワイヤー放電加工により、その側面にオリエンテーションフラットを有する円柱状ブロック２０を切り出すことが好ましい。ここで、円柱状ブロック２０のオリエンテーションフラットは、円柱状ブロック２０をスライスして酸化ガリウム基板を形成したときに、酸化ガリウム基板のオリエンテーションフラットとなる。なお、図１Ｂに示されるオリエンテーションフラット２１、２２は、オリエンテーションフラットの一例であり、オリエンテーションフラットは１つであってもよい。 Moreover, it is preferable to cut out the cylindrical block 20 having an orientation flat on the side surface by wire electric discharge machining. Here, the orientation flat of the cylindrical block 20 is the orientation flat of the gallium oxide substrate when the cylindrical block 20 is sliced to form a gallium oxide substrate. Note that the orientation flats 21 and 22 shown in FIG. 1B are examples of orientation flats, and there may be only one orientation flat.
　円抜き加工と同時に円柱状ブロック２０にオリエンテーションフラットを形成することができるため、円抜き加工とオリエンテーションフラットの形成を別工程で行う場合と比較して、円柱状ブロック２０に欠陥が発生する可能性をより低くすることができる。 Since the orientation flat can be formed on the cylindrical block 20 at the same time as the circular punching process, there is a possibility that defects are generated in the cylindrical block 20 as compared with the case where the circular punching process and the formation of the orientation flat are performed in separate processes. Can be made lower.
　例えば、コアドリルを用いてコアリングする場合、円筒形の砥石を回転させてインゴットを削ることにより円筒形ブロックをくり抜くため、当然ながら、オリエンテーションフラットを同時に形成することはできず、コアリングと別工程でオリエンテーションフラットを形成する必要がある。この場合、オリエンテーションフラットは、例えば、スライシングマシンを用いて形成されるが、単結晶が劈開性の強い面を有する場合、チッピング等の欠陥が生じるおそれがある。 For example, when coring using a core drill, the cylindrical block is hollowed out by rotating a cylindrical grindstone to scrape the ingot, so of course, the orientation flat cannot be formed at the same time. It is necessary to form an orientation flat. In this case, the orientation flat is formed using, for example, a slicing machine. However, if the single crystal has a highly cleaved surface, defects such as chipping may occur.
　円柱状ブロック２０に形成されるオリエンテーションフラットは、図１Ａ及び図１Ｂに示されるオリエンテーションフラット２１、２２であることが好ましい。これは、円柱状ブロック２０から得られる酸化ガリウム基板にオリエンテーションフラット２１、２２が設けられることにより、研磨等の工程における欠陥の発生を抑えることができるからである。その詳細は後述する。オリエンテーションフラット２１、２２は、円柱状ブロック２０の側面の対向する位置にそれぞれ設けられる。 The orientation flats formed on the cylindrical block 20 are preferably the orientation flats 21 and 22 shown in FIGS. 1A and 1B. This is because by providing the orientation flats 21 and 22 on the gallium oxide substrate obtained from the cylindrical block 20, it is possible to suppress generation of defects in a process such as polishing. Details thereof will be described later. Orientation flats 21 and 22 are respectively provided at opposing positions on the side surface of the cylindrical block 20.
（円柱状ブロックからの基板の製造工程）
　図２Ａは円柱状ブロック２０の側面図であり、図２Ｂは円柱状ブロック２０をスライスすることにより得られる酸化ガリウム基板３０の側面図である。 (Manufacturing process of substrate from cylindrical block)
2A is a side view of the cylindrical block 20, and FIG. 2B is a side view of a gallium oxide substrate 30 obtained by slicing the cylindrical block 20. FIG.
　酸化ガリウム基板３０は、円柱状ブロック２０をその径方向（厚さ方向に垂直な方向）に沿ってスライスすることにより形成される。このため、酸化ガリウム基板３０の主面３１は、（１００）面以外の面、例えば（－２０１）面、（１０１）面、又は（００１）面と一致する。なお、円柱状ブロック２０をその径方向から所定の角度だけオフセットした方向に沿ってスライスしてもよい。この場合であっても、酸化ガリウム基板３０の主面３１が（１００）面以外の面、例えば（－２０１）面、（１０１）面、又は（００１）面と一致するようにスライスされる。 The gallium oxide substrate 30 is formed by slicing the cylindrical block 20 along its radial direction (direction perpendicular to the thickness direction). Therefore, the main surface 31 of the gallium oxide substrate 30 coincides with a surface other than the (100) plane, for example, the (−201) plane, the (101) plane, or the (001) plane. The cylindrical block 20 may be sliced along a direction offset by a predetermined angle from the radial direction. Even in this case, the main surface 31 of the gallium oxide substrate 30 is sliced so as to coincide with a surface other than the (100) plane, for example, the (−201) plane, the (101) plane, or the (001) plane.
　図３は、酸化ガリウム基板３０の平面図である。酸化ガリウム基板３０において、オリエンテーションフラット２１、２２は、対向する位置にそれぞれ設けられ、主面３１と（１００）面との交線に平行な方向を基準として±２°以内の方向に沿って設けられ、６ｍｍ以上の長さを有する。図３におけるＬ２、Ｌ３は、それぞれオリエンテーションフラット２１、２２の長さを表す。すなわち、Ｌ２、Ｌ３は６ｍｍ以上である。 FIG. 3 is a plan view of the gallium oxide substrate 30. In the gallium oxide substrate 30, the orientation flats 21 and 22 are provided at opposing positions, and are provided along directions within ± 2 ° with respect to a direction parallel to the intersection line of the main surface 31 and the (100) plane. And has a length of 6 mm or more. L2 and L3 in FIG. 3 represent the lengths of the orientation flats 21 and 22, respectively. That is, L2 and L3 are 6 mm or more.
　なお、Ｌ２、Ｌ３のいずれかは、一般的なオリエンテーションフラットの長さである１６ｍｍ以上であることが好ましい。また、オリエンテーションフラット２１、２２の面は、一般的なオリエンテーションフラットの面と同様に、主面３１に対して垂直であることが好ましい。 In addition, it is preferable that either L2 or L3 is 16 mm or more which is the length of a general orientation flat. In addition, the surfaces of the orientation flats 21 and 22 are preferably perpendicular to the main surface 31 in the same manner as a general orientation flat surface.
　酸化ガリウム基板３０がオリエンテーションフラット２１、２２を有することにより、外周研削、ベベル加工、研磨、又は洗浄を施す際に酸化ガリウム基板３０に加わる力による割れ（チッピング）の発生を抑えることができる。以下に、その理由を説明する。 Since the gallium oxide substrate 30 has the orientation flats 21 and 22, it is possible to suppress the occurrence of cracking (chipping) due to the force applied to the gallium oxide substrate 30 when performing peripheral grinding, beveling, polishing, or cleaning. The reason will be described below.
　図４Ａ、４Ｂは、酸化ガリウム基板３０にクラックが発生する様子を模式的に表す図である。図４Ａ、４Ｂは、それぞれ酸化ガリウム基板３０の平面図と断面図である。図４Ｂは、主面３１が（－２０１）である酸化ガリウム基板３０を酸化ガリウム単結晶のｂ軸に垂直な方向に切断したときの断面を示す。 FIGS. 4A and 4B are diagrams schematically showing how a crack is generated in the gallium oxide substrate 30. FIG. 4A and 4B are a plan view and a cross-sectional view of the gallium oxide substrate 30, respectively. FIG. 4B shows a cross section of the gallium oxide substrate 30 having the main surface 31 of (−201) cut in a direction perpendicular to the b-axis of the gallium oxide single crystal.
　上述のように、酸化ガリウムの単結晶は（１００）面において高い劈開性を有するため、（１００）面においてクラック等の欠陥が発生しやすい。このため、円形の酸化ガリウム基板３０においては、外縁に近い領域４１において、（１００）面に発生するクラックによる割れが発生しやすい。図４Ａ、Ｂに示されるクラック面４０は、クラックの発生した（１００）面である。 As described above, since the gallium oxide single crystal has high cleavage at the (100) plane, defects such as cracks are likely to occur at the (100) plane. For this reason, in the circular gallium oxide substrate 30, cracks due to cracks generated on the (100) plane are likely to occur in the region 41 near the outer edge. A crack surface 40 shown in FIGS. 4A and 4B is a (100) surface where cracks are generated.
　具体的には、酸化ガリウム基板３０に施される外周研削、ベベル加工、研磨、又は洗浄においては、これらの工程において加わる外力により、主面３１上の縁の長さＬ０が５ｍｍ以下であるようなクラック面４０が発生しやすい。ここで、クラック面４０は（１００）面であるため、クラック面４０の主面３１上の縁は、主面３１と（１００）面との交線に平行である。 Specifically, in peripheral grinding, beveling, polishing, or cleaning performed on the gallium oxide substrate 30, the length L0 of the edge on the main surface 31 is 5 mm or less due to external force applied in these steps. Crack surface 40 is likely to occur. Here, since the crack surface 40 is a (100) plane, the edge of the crack surface 40 on the main surface 31 is parallel to the line of intersection of the main surface 31 and the (100) surface.
　このため、本実施の形態では、主面３１と（１００）面との交線に平行な方向を基準として±２°以内の方向に沿って設けられ、６ｍｍ以上の長さを有するオリエンテーションフラット２１、２２を酸化ガリウム基板３０に設けることにより、長さＬ０が５ｍｍ以下であるクラック面４０が発生する領域を除去している。これにより、酸化ガリウム基板３０に外周研削、ベベル加工、研磨、又は洗浄を施す際の割れの発生を抑えることができる。 For this reason, in the present embodiment, the orientation flat 21 is provided along a direction within ± 2 ° with respect to a direction parallel to the intersection line of the main surface 31 and the (100) plane, and has a length of 6 mm or more. , 22 on the gallium oxide substrate 30, the region where the crack surface 40 having a length L0 of 5 mm or less is generated is removed. Thereby, generation | occurrence | production of the crack at the time of giving outer periphery grinding, bevel processing, grinding | polishing, or washing | cleaning to the gallium oxide substrate 30 can be suppressed.
　以下に、円柱状ブロック２０から酸化ガリウム基板３０を製造する工程の具体例について述べる。 Hereinafter, a specific example of a process for manufacturing the gallium oxide substrate 30 from the cylindrical block 20 will be described.
　円柱状ブロック２０は、例えば、マルチワイヤーソーにより、１ｍｍ程度の厚さにスライスされ、酸化ガリウム基板３０が得られる。ワイヤーソーは固定砥粒方式のものを用いることが好ましい。スライス速度は毎分０．１２５～０．３ｍｍ程度が好ましい。 The cylindrical block 20 is sliced to a thickness of about 1 mm by, for example, a multi-wire saw, and the gallium oxide substrate 30 is obtained. The wire saw is preferably a fixed abrasive type. The slicing speed is preferably about 0.125 to 0.3 mm per minute.
　次に、加工歪の緩和、及び電気特性向上、透過性向上を目的とするアニールを酸化ガリウム基板３０に施す。例えば、昇温時には酸素雰囲気下でアニールを行い、昇温後に温度を保持する間は窒素雰囲気、アルゴン雰囲気、ヘリウム雰囲気等の不活性雰囲気下でアニールを行う。保持温度は１４００～１６００℃であることが好ましい。 Next, annealing is performed on the gallium oxide substrate 30 for the purpose of relaxing processing strain, improving electrical characteristics, and improving permeability. For example, annealing is performed in an oxygen atmosphere when the temperature is raised, and annealing is performed in an inert atmosphere such as a nitrogen atmosphere, an argon atmosphere, or a helium atmosphere while the temperature is maintained after the temperature is raised. The holding temperature is preferably 1400 to 1600 ° C.
　次に、ダイヤモンドの研削砥石を用いて、所望の外形サイズになるまで酸化ガリウム基板３０の外周を研削する。砥石の粒度は＃４００～１０００（ＪＩＳＢ４１３１による規定）程度であることが好ましい。酸化ガリウム基板３０はオリエンテーションフラット２１、２２を有するため、本工程における割れの発生が抑えられる。 Next, the outer periphery of the gallium oxide substrate 30 is ground using a diamond grinding wheel until a desired outer size is obtained. The grain size of the grindstone is preferably about # 400 to 1000 (specified by JISB4131). Since the gallium oxide substrate 30 has the orientation flats 21 and 22, the occurrence of cracks in this step is suppressed.
　次に、酸化ガリウム基板３０のエッジに所望の角度でのべベル（面取り）加工を施す。酸化ガリウム基板３０はオリエンテーションフラット２１、２２を有するため、本工程における割れの発生が抑えられる。 Next, the edge of the gallium oxide substrate 30 is beveled (chamfered) at a desired angle. Since the gallium oxide substrate 30 has the orientation flats 21 and 22, the occurrence of cracks in this step is suppressed.
　次に、ダイヤモンドの研削砥石を用いて、所望の厚さになるまで酸化ガリウム基板３０の主面３１を研削する。砥石の粒度は＃８００～１０００（ＪＩＳＢ４１３１による規定）程度であることが好ましい。酸化ガリウム基板３０はオリエンテーションフラット２１、２２を有するため、本工程における割れの発生が抑えられる。 Next, the main surface 31 of the gallium oxide substrate 30 is ground to a desired thickness using a diamond grinding wheel. The grain size of the grindstone is preferably about # 800 to 1000 (specified by JISB4131). Since the gallium oxide substrate 30 has the orientation flats 21 and 22, the occurrence of cracks in this step is suppressed.
　次に、研磨定盤とダイヤモンドスラリーを用いて、所望の厚さになるまで酸化ガリウム基板３０の主面３１を研磨する。研磨定盤は金属系やガラス系の材質のものが好ましい。ダイヤモンドスラリーに含まれるダイヤモンド砥粒の粒径は０．５μｍ程度が好ましい。酸化ガリウム基板３０はオリエンテーションフラット２１、２２を有するため、本工程における割れの発生が抑えられる。 Next, the main surface 31 of the gallium oxide substrate 30 is polished to a desired thickness using a polishing surface plate and diamond slurry. The polishing surface plate is preferably made of a metal or glass material. The particle size of the diamond abrasive grains contained in the diamond slurry is preferably about 0.5 μm. Since the gallium oxide substrate 30 has the orientation flats 21 and 22, the occurrence of cracks in this step is suppressed.
　次に、ポリッシングクロスとＣＭＰ（Ｃｈｅｍｉｃａｌ Ｍｅｃｈａｎｉｃａｌ Ｐｏｌｉｓｈｉｎｇ）用のスラリーを用いて、原子レベルの平坦性（例えば、平均粗さＲａが０．０５～０．１ｎｍ）が得られるまで酸化ガリウム基板３０の主面３１を研磨する。ポリッシングクロスはナイロン、絹繊維、ウレタン等の材質のものが好ましい。スラリーの砥粒にはコロイダルシリカを用いることが好ましい。酸化ガリウム基板３０はオリエンテーションフラット２１、２２を有するため、本工程における割れの発生が抑えられる。 Next, using a polishing cloth and a CMP (Chemical Mechanical Polishing) slurry, until the flatness at the atomic level (for example, the average roughness Ra is 0.05 to 0.1 nm) is obtained, the main gallium oxide substrate 30 The surface 31 is polished. The polishing cloth is preferably made of nylon, silk fiber, urethane or the like. It is preferable to use colloidal silica for the abrasive grains of the slurry. Since the gallium oxide substrate 30 has the orientation flats 21 and 22, the occurrence of cracks in this step is suppressed.
　その後、酸化ガリウム基板３０を洗浄する。具体的には、例えば、３分間のメタノール超音波洗浄、３分間のアセトン超音波洗浄、３分間のメタノール超音波洗浄、５分間の流水洗浄、５分間の硫酸加水洗浄、５分間の流水洗浄を順次行う。酸化ガリウム基板３０はオリエンテーションフラット２１、２２を有するため、本工程における割れの発生が抑えられる。 Thereafter, the gallium oxide substrate 30 is cleaned. Specifically, for example, ultrasonic cleaning for 3 minutes, ultrasonic cleaning for 3 minutes, ultrasonic cleaning for 3 minutes, cleaning with methanol for 5 minutes, washing with running water for 5 minutes, washing with sulfuric acid for 5 minutes, washing with running water for 5 minutes. Do it sequentially. Since the gallium oxide substrate 30 has the orientation flats 21 and 22, the occurrence of cracks in this step is suppressed.
（実施の形態の効果）
　上記の実施の形態によれば、ワイヤー放電加工により酸化ガリウムインゴット２の円抜き加工を行うことにより、欠陥の少ない酸化ガリウム単結晶の円柱状ブロック２０を得ることができる。また、この欠陥の少ない酸化ガリウム単結晶の円柱状ブロック２０をスライスすることにより、高品質の酸化ガリウム基板３０を得ることができる。 (Effect of embodiment)
According to said embodiment, the cylindrical block 20 of a gallium oxide single crystal with few defects can be obtained by performing the circular punching process of the gallium oxide ingot 2 by wire electric discharge machining. In addition, a high-quality gallium oxide substrate 30 can be obtained by slicing the cylindrical block 20 of gallium oxide single crystal with few defects.
　また、円抜き加工と同時にオリエンテーションフラットを形成することにより、円抜き加工と別工程でオリエンテーションフラットを形成する場合と比較して、円柱状ブロックの欠陥の発生を抑えることができる。 In addition, by forming the orientation flat at the same time as the circular punching process, it is possible to suppress the occurrence of defects in the cylindrical block as compared to the case where the orientation flat is formed in a separate process from the circular punching process.
　また、所定の条件を満たすオリエンテーションフラット（オリエンテーションフラット２１、２２）を酸化ガリウム基板３０に設けることにより、酸化ガリウム基板３０に外周研削、ベベル加工、研磨、又は洗浄を施す際の割れの発生を抑えることができる。 In addition, by providing orientation flats (orientation flats 21 and 22) satisfying predetermined conditions on the gallium oxide substrate 30, generation of cracks when the outer peripheral grinding, beveling, polishing, or cleaning is performed on the gallium oxide substrate 30 is suppressed. be able to.
　以上、本発明の実施の形態を説明したが、本発明は、上記実施の形態に限定されず、発明の主旨を逸脱しない範囲内において種々変形実施が可能である。 Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention.
　また、上記に記載した実施の形態は請求の範囲に係る発明を限定するものではない。また、実施の形態の中で説明した特徴の組合せの全てが発明の課題を解決するための手段に必須であるとは限らない点に留意すべきである。 The embodiments described above do not limit the invention according to the claims. In addition, it should be noted that not all the combinations of features described in the embodiments are essential to the means for solving the problems of the invention.
　欠陥の発生を抑えつつ、酸化ガリウム単結晶のインゴットから酸化ガリウム基板を得ることのできる酸化ガリウム基板の製造方法、及び加工の際の欠陥の発生を抑えることのできる構造を有する酸化ガリウム基板を提供する。 A method of manufacturing a gallium oxide substrate capable of obtaining a gallium oxide substrate from a gallium oxide single crystal ingot while suppressing generation of defects, and a gallium oxide substrate having a structure capable of suppressing generation of defects during processing are provided. To do.
１…ワイヤー電極、２…酸化ガリウムインゴット、２０…円柱状ブロック、２１、２２…オリエンテーションフラット、３０…酸化ガリウム基板、３１…主面 DESCRIPTION OF SYMBOLS 1 ... Wire electrode, 2 ... Gallium oxide ingot, 20 ... Cylindrical block, 21, 22 ... Orientation flat, 30 ... Gallium oxide substrate, 31 ... Main surface

Claims (6)

  1. 　ワイヤー放電加工により、酸化ガリウム単結晶のインゴットから、径方向に平行な断面が（１００）面と異なる酸化ガリウム単結晶の円柱状ブロックを切り出す工程と、
    　前記円柱状ブロックをスライスして酸化ガリウム基板を得る工程と、
    　を含む、酸化ガリウム基板の製造方法。     A step of cutting a cylindrical block of gallium oxide single crystal having a cross section parallel to the radial direction different from the (100) plane from the ingot of gallium oxide single crystal by wire electric discharge machining;
    Slicing the cylindrical block to obtain a gallium oxide substrate;
    A method for manufacturing a gallium oxide substrate.
  2. 　前記ワイヤー放電加工により、その側面にオリエンテーションフラットを有する前記円柱状ブロックを切り出す、
    　請求項１に記載の酸化ガリウム基板の製造方法。     Cutting out the cylindrical block having an orientation flat on its side surface by the wire electric discharge machining,
    The method for producing a gallium oxide substrate according to claim 1.
  3. 　前記円柱状ブロックの前記径方向に平行な断面が（－２０１）面、（１０１）面、又は（００１）面である、
    　請求項１又は２に記載の酸化ガリウム基板の製造方法。     A cross section parallel to the radial direction of the cylindrical block is a (−201) plane, a (101) plane, or a (001) plane.
    The manufacturing method of the gallium oxide substrate of Claim 1 or 2.
  4. 　前記酸化ガリウム基板の主面は（１００）面と異なる面であり、
    　前記オリエンテーションフラットは、前記円柱状ブロックの側面の対向する位置にそれぞれ設けられる第１のオリエンテーションフラット及び第２のオリエンテーションフラットであり、
    　前記第１のオリエンテーションフラット及び前記第２のオリエンテーションフラットは、前記酸化ガリウム基板の主面と（１００）面との交線に平行な方向を基準として±２°以内の方向に沿って設けられ、６ｍｍ以上の長さを有し、
    　前記酸化ガリウム基板に外周研削、ベベル加工、研磨、洗浄のうちの少なくともいずれか１つを施す、
    　請求項２に記載の酸化ガリウム基板の製造方法。     The main surface of the gallium oxide substrate is a surface different from the (100) surface,
    The orientation flats are a first orientation flat and a second orientation flat respectively provided at opposing positions on the side surface of the cylindrical block.
    The first orientation flat and the second orientation flat are provided along a direction within ± 2 ° with reference to a direction parallel to an intersection line between the main surface of the gallium oxide substrate and the (100) plane, Having a length of 6 mm or more,
    Applying at least one of peripheral grinding, beveling, polishing, and cleaning to the gallium oxide substrate;
    A method for manufacturing a gallium oxide substrate according to claim 2.
  5. 　前記酸化ガリウム基板の前記主面が（－２０１）面、（１０１）面、又は（００１）面である、
    　請求項４に記載の酸化ガリウム基板の製造方法。     The main surface of the gallium oxide substrate is a (−201) plane, a (101) plane, or a (001) plane;
    The method for producing a gallium oxide substrate according to claim 4.
  6. 　酸化ガリウム単結晶からなる酸化ガリウム基板であって、
    　主面が（１００）面と異なる面であり、
    　対向する位置にそれぞれ設けられた、前記主面と（１００）面との交線に平行な方向を基準として±２°以内の方向に沿って設けられ、６ｍｍ以上の長さを有する、２つのオリエンテーションフラットを有する、酸化ガリウム基板。     A gallium oxide substrate made of a gallium oxide single crystal,
    The main surface is a surface different from the (100) surface,
    Two pieces each having a length of 6 mm or more are provided along a direction within ± 2 ° with respect to a direction parallel to the intersecting line of the main surface and the (100) plane, which are provided at opposite positions, respectively. A gallium oxide substrate having an orientation flat.
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