Substrate with gallium oxide film and method for manufacturing same

Abstract

The present invention pertains to a substrate with a gallium oxide film, the substrate having: an Si single crystal substrate; a gallium oxide layer provided on the Si single crystal substrate; and a gallium oxide film provided on the gallium oxide layer. The gallium oxide layer has an atomic arrangement that matches the Si single crystal substrate.

Description

Substrate with gallium oxide film and method for manufacturing same

[0001] The present invention relates to a substrate with a gallium oxide film and a method for producing the same.

[0002] Although silicon semiconductors using SiC have been put to practical use, gallium oxide is attracting attention as a next-generation power semiconductor device. This is because the band gap of gallium oxide is larger than that of 4H—SiC substrates, which is 3.26 eV. In particular, the band gap of β-type gallium oxide is very large, at approximately 4.5 to 4.9 eV.

[0003] For example, Patent Document 1 discloses a technique for growing a β-type gallium oxide single crystal film by supplying gallium element from a first cell 13a inside a vacuum chamber 10 to a β-type gallium oxide substrate 2 and supplying oxygen gas containing ozone to the β-type gallium oxide substrate 2. Furthermore, Non-Patent Document 1 discloses a technique for using a molecular beam epitaxy (MBE) device to grow β-type gallium oxide, and treating the oxygen gas with rf-plasma during the growth.

[0004] In contrast to the above, it is difficult to grow gallium oxide on a heterogeneous substrate. For example, Non-Patent Document 2 describes a SiC buffer layer between a Si substrate and gallium oxide, and Non-Patent Document 3 describes an Al ２ O ３ Research has been conducted into growing gallium oxide on a Si substrate by inserting a buffer layer. In addition, in Non-Patent Document 4, gallium oxide was grown without inserting a buffer layer, and an amorphous layer of gallium oxide was formed.

[0005] Japanese Patent Application Publication No. 2013-56802

[0006] Rf-plasma-assisted molecular-beam epitaxy of β-Ga2O3,E. G. Villora, et al. , Appl. Phys. Lett. 88, 031105 (2006) Study of the Anisotropic Elastoplastic Properties of β-Ga2O3 Films Synthesized on SiC / Si Substrates, A. S. Grashenko et al. , Phys. Solid State, 60, 852-857 (2018) β-Ga2O3 on Si (001) grown by plasma-assisted MBE with γ-Al2O3 (111) buffer layer: Structural characterization, T. Hadamek et al. , AIP Advances, 11, 045209 (2021) β-Ga2O3 MOSFETs on the Si substrate fabricated by the ion-cutting process, Y. B. Wang et al. , Sci. China: Phys. , Mech. Astron. , 63, 277311 (2020)

[0007] Gallium oxide power semiconductors are expected to reduce device power consumption and provide higher voltage resistance compared to conventional silicon semiconductors.

[0008] However, as in Patent Document 1 and Non-Patent Document 1, when attempting to form a gallium oxide film on a gallium oxide substrate, the maximum diameter is currently limited, and the growth temperature of the gallium oxide film is high at 700 ° C or higher, and the growth rate is slow at about 0.1 μm / h. Furthermore, gallium oxide substrates are quite expensive compared to other semiconductor substrates. Therefore, it is difficult to manufacture devices that can be industrialized. In addition, improvements in the crystallinity and flatness of gallium oxide are also desired.

[0009] On the other hand, when gallium oxide is heteroepitaxially grown on a single crystal substrate made of a different material, as in Non-Patent Documents 2 and 3, a SiC buffer layer and an Al ２ O ３The gallium oxide film is grown via a buffer layer. However, the growth temperature of the gallium oxide film is high, at 600°C or higher, and the growth rate is slow. Furthermore, the resulting gallium oxide film is not flat and has a domain structure, resulting in low orientation. In addition, the gallium oxide film obtained by the method disclosed in Non-Patent Document 4 is an amorphous layer, and no crystalline layer is obtained.

[0010] As such, heteroepitaxial growth of gallium oxide on a single-crystal substrate made of a different material is extremely difficult, and even if a gallium oxide film is obtained, its crystallinity and other factors do not allow it to achieve sufficient pressure resistance when used in a semiconductor, indicating that there is room for improvement.

[0011] Therefore, an object of the present invention is to provide a gallium oxide film-coated substrate having a gallium oxide film that has excellent pressure resistance when used in a semiconductor, and a novel method for producing the gallium oxide film-coated substrate.

[0012] As a result of intensive research into the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by selecting a Si single crystal substrate as a single crystal substrate made of a different material and forming a gallium oxide film on the Si single crystal substrate via a gallium oxide layer whose atomic arrangement matches that of the Si single crystal substrate, and have thus completed the present invention.

[0013] That is, the gist of the present invention is as follows. [1] A gallium oxide film-coated substrate comprising a Si single crystal substrate, a gallium oxide layer provided on the Si single crystal substrate, and a gallium oxide film provided on the gallium oxide layer, wherein the gallium oxide layer has an atomic arrangement that matches that of the Si single crystal substrate. [2] The gallium oxide film-coated substrate according to [1] above, wherein the gallium oxide film has an arithmetic mean surface roughness Ra of 4.5 nm or less. [3] The gallium oxide film-coated substrate according to [1] or [2] above, wherein the gallium oxide layer has a thickness of 0.1 to 1000 nm. [4] The gallium oxide film-coated substrate according to any one of [1] to [3] above, wherein the breakdown voltage exceeds 120 V / μm. [5] The gallium oxide film-coated substrate according to any one of [1] to [4] above, wherein the gallium oxide film is a β-type gallium oxide film. [6] The substrate with a gallium oxide film according to any one of [1] to [5], wherein the gallium oxide layer is provided on the Si single crystal substrate having a (100) plane orientation. [7] The substrate with a gallium oxide film according to any one of [1] to [6], wherein the plane orientation of the gallium oxide film is (100). [8] The substrate with a gallium oxide film according to any one of [1] to [7], wherein the plane orientation of the gallium oxide layer is (100).

[0014] [9] A method for producing a gallium oxide film-coated substrate, the method comprising the steps of: placing a Si single crystal substrate inside a reaction chamber; and supplying elemental gallium and oxygen radicals, in this order, into the reaction chamber at least once each to grow a gallium oxide layer on the surface of the Si single crystal substrate; and generating plasma from a mixed gas containing oxygen and ozone to dissociate the ozone into oxygen constituent particles, which are supplied to the reaction chamber under reduced pressure, while simultaneously supplying elemental gallium to the reaction chamber, to epitaxially grow a gallium oxide film on the surface of the gallium oxide layer.

[10] A method for producing a gallium oxide film-coated substrate according to [9], wherein the Si single crystal substrate is cleaned and then placed inside the reaction chamber.

[11] A method for producing a gallium oxide film-coated substrate according to [9] or

[10] , wherein the reflection high-energy electron diffraction pattern obtained when the gallium oxide layer is grown is streaky.

[12] The method for producing a gallium oxide film-coated substrate according to any one of [9] to

[11] above, wherein the growth temperature for growing the gallium oxide layer is 200 to 600°C.

[13] The method for producing a gallium oxide film-coated substrate according to any one of

[12] above, wherein the growth time for growing the gallium oxide layer is 10 to 50 seconds.

[14] The method for producing a gallium oxide film-coated substrate according to any one of [9] to

[13] above, wherein the film formation temperature for epitaxially growing the gallium oxide film is 200 to 600°C.

[15] The method for producing a gallium oxide film-coated substrate according to any one of [9] to

[14] above, wherein the arithmetic mean surface roughness Ra of the gallium oxide film is 4.5 nm or less.

[16] The method for producing a gallium oxide film-coated substrate according to any one of [9] to

[15] above, wherein the gallium oxide layer is grown to a thickness of 0.1 to 1000 nm.

[17] The method for producing a gallium oxide film-coated substrate according to any one of [9] to

[16] above, wherein the resulting gallium oxide film-coated substrate has a breakdown voltage of more than 120 V / μm.

[18] The method for producing a gallium oxide film-coated substrate according to any one of [9] to

[17] above, wherein the gallium oxide film is a β-type gallium oxide film.

[19] The method for producing a gallium oxide film-coated substrate according to any one of [9] to

[18] above, wherein the gallium oxide layer is provided on the Si single crystal substrate having a (100) plane orientation.

[20] The method for producing a gallium oxide film-coated substrate according to any one of [9] to

[19] above, wherein the gallium oxide film has a plane orientation of (100).

[21] The method for producing a gallium oxide film-coated substrate according to any one of [9] to

[20] above, wherein the gallium oxide layer has a plane orientation of (100).

[0015] The gallium oxide film in the gallium oxide film-coated substrate according to the present invention has excellent pressure resistance when used in semiconductors. Furthermore, the manufacturing method according to the present invention not only provides the above-mentioned gallium oxide film-coated substrate, but also enables a high growth rate and a low growth temperature in the heteroepitaxial growth of gallium oxide. Therefore, industrialization is expected at a lower cost than conventional methods.

[0016] FIG. 1 is a schematic cross-sectional view showing the structure of a gallium oxide film-coated substrate according to this embodiment. FIG. 2 is a schematic configuration diagram of a manufacturing apparatus used to manufacture a gallium oxide film-coated substrate according to this embodiment. FIG. 3 is an SEM image of the gallium oxide film-coated substrate obtained in Example 1, where (a) of FIG. 3 is an SEM image of the surface of the gallium oxide film-coated substrate observed at a magnification of 20,000 times, and (b) of FIG. 3 is an SEM image of the cross section of the gallium oxide film-coated substrate observed at a magnification of 20,000 times. FIG. 4 is an AFM image of the gallium oxide film-coated substrate obtained in Example 1, where (a) of FIG. 4 is an AFM image of the surface of the gallium oxide film-coated substrate in a scanning range of 5 × 5 μm, and (b) of FIG. 4 is a bird's-eye view of the surface of the gallium oxide film-coated substrate in a scanning range of 5 × 5 μm by AFM. FIG. 5 is a RHEED pattern obtained in situ by MBE while a gallium oxide layer was grown on a Si single crystal substrate in Example 1.

[0017] The present invention will be described in detail below, but the present invention is not limited to the following embodiments and can be modified as desired within the scope of the present invention. In this specification, a single-crystal substrate refers to a substrate in which the entire substrate is single crystal. In this specification, uniaxial orientation refers to the presence of a large number of crystal grains in which the direction of at least one of the crystal axes is aligned, and refers to a state in which a large number of crystal grains rotated around this single axis are present. The uniaxial orientation of a gallium oxide film can be confirmed, for example, by symmetric X-ray diffraction (symmetric XRD). In this specification, oxygen-component particles refer to oxygen atoms containing singlet oxygen atoms and triplet oxygen atoms, oxygen molecules, ozone, or particles containing these in an excited state. In this specification, the symbol "to" indicating a numerical range is used to mean that the numerical values ​​before and after it are included as the lower and upper limits.

[0018] 1, the gallium oxide film-coated substrate 100 according to this embodiment includes a Si single crystal substrate 110, a gallium oxide layer 120 provided on the Si single crystal substrate 110, and a gallium oxide film 130 provided on the gallium oxide layer 120. The atomic arrangement of the gallium oxide layer is matched with that of the Si single crystal substrate.

[0019] The gallium oxide layer 120 and the gallium oxide film 130 may be provided on at least one of the main surfaces of the Si single crystal substrate 110, i.e., the first main surface 110a, or may be provided on both main surfaces. However, from the viewpoint of epitaxial growth of the gallium oxide film 130, it is preferable that the gallium oxide layer 120 and the gallium oxide film 130 be provided only on the first main surface 110a.

[0020] <Si Single Crystal Substrate> A conventionally known Si single crystal substrate can be used as the Si single crystal substrate 110 in this embodiment. For example, a substrate obtained by growing a crystal by the Czochralski method or the FZ (Floating Zone) method, cutting, and polishing can be used.

[0021] The Si single crystal substrate 110 is preferably a substrate oriented in the (100) plane, and the main surface on the (100) oriented side is preferably used as the first main surface 110a, on which the gallium oxide layer 120 is preferably provided.

[0022] <Gallium Oxide Layer> The gallium oxide layer 120 in this embodiment is a layer made of gallium oxide that is epitaxially grown on the Si single crystal substrate 110, preferably on the (100) plane of the Si single crystal substrate.

[0023] However, the gallium oxide layer may contain inevitable impurities. Examples of inevitable impurities include Si, B, C, Mg, Fe, Ni, and Cr. The content of each element that constitutes the inevitable impurity is 1×10 １７ atoms / cm ３ Preferably less than 5 x 10 １６ atoms / cm ３ More preferably, 1×10 １６ atoms / cm ３ The following is more preferable, and the smaller the amount, the better. The above content can be measured by secondary ion mass spectrometry (SIMS).

[0024] The atomic arrangement of the gallium oxide layer is matched with that of the Si single crystal substrate. Here, "matched atomic arrangement" means that the rate of lattice constant mismatch between the Si single crystal substrate and the gallium oxide layer is very small. Since the rate of mismatch is smaller than the rate of lattice constant mismatch between the Si single crystal substrate and the gallium oxide film, growing a gallium oxide film via a gallium oxide layer can result in a gallium oxide film with better crystallinity. The lower the rate of mismatch, the more preferable it is, but it is usually greater than 0%. Here, the lattice constant mismatch is the ratio of the difference in lattice constant of the gallium oxide layer relative to the lattice constant of the Si single crystal substrate in the same direction. The rate of lattice constant mismatch can be determined by analyzing the epitaxial relationship between the Si single crystal substrate and the gallium oxide layer from the results of symmetric X-ray diffraction measurement and in-plane X-ray diffraction measurement. For example, it can be calculated from the ratio between the lattice constant of the Si single crystal substrate and the lattice constant of the gallium oxide layer projected in a certain direction of the Si single crystal substrate.

[0025] The gallium oxide layer is more preferably uniaxially oriented, and even more preferably single crystal. The crystallinity of the gallium oxide layer can be determined by X-ray diffraction, transmission electron diffraction, reflection high-energy electron diffraction (RHEED), or the like.

[0026] When the gallium oxide layer is single crystal, the plane orientation of the gallium oxide layer is preferably (100), and more preferably, the gallium oxide layer having a (100) plane orientation is provided on a Si single crystal substrate having a (100) plane orientation. The gallium oxide layer here is more preferably a β-type gallium oxide layer.

[0027] In this embodiment, it was found that providing the gallium oxide layer 120 between the Si single crystal substrate 110 and the gallium oxide film 130 improves the crystallinity and flatness of the gallium oxide film 130 formed thereon. As a result, it was found that the resulting gallium oxide film has very good pressure resistance when applied to a semiconductor.

[0028] The reason why the above effect is obtained by using the gallium oxide layer 120 is not clear, but it is thought to be as follows. Compared to when a gallium oxide film is directly formed on a Si single crystal substrate, when a gallium oxide layer whose atomic arrangement matches that of the Si single crystal substrate is used, the gallium oxide film is more likely to grow in a state of closer lattice matching than when crystals are grown directly on the Si substrate. As a result, it is thought that the arrangement of Ga atoms and O atoms that make up gallium oxide is more likely to be regularly arranged, thereby increasing the crystallinity of the gallium oxide film. It is thought that the high crystallinity of this gallium oxide film contributes to the realization of high breakdown voltage when used in semiconductors.

[0029] In this embodiment, the thickness of the gallium oxide layer 120 is preferably 0.1 to 1000 nm. Here, from the viewpoint of improving the crystallinity of the gallium oxide film 130 provided on the gallium oxide layer 120, the thickness is preferably 0.1 nm or more, more preferably 0.5 nm or more, and even more preferably 1 nm or more. On the other hand, from the viewpoint of the overall growth rate, the thickness is preferably 1000 nm or less, more preferably 500 nm or less, and even more preferably 100 nm or less. The thickness of the gallium oxide layer 120 can be measured by observing a cross section of the gallium oxide film-coated substrate using a field emission scanning electron microscope (FE-SEM; Field Emission-Scanning Electron Microscope)-energy dispersive X-ray spectroscopy (EDX; Energy dispersive X-ray spectroscopy) method or a transmission electron microscope (TEM).

[0030] <Gallium Oxide Film> The gallium oxide film 130 in this embodiment is provided on the Si single crystal substrate 110, preferably on the (100) oriented main surface of the Si single crystal substrate, via the gallium oxide layer 120.

[0031] Gallium oxide is a crystalline polymorph, and has at least five crystalline structures called α-type, β-type, γ-type, δ-type, and ε-type. Of these, β-type gallium oxide film is preferred from the viewpoint that it is the most stable phase and is expected to be useful in industrial applications. However, the gallium oxide film in this embodiment is not limited to β-type gallium oxide film. For example, α-type gallium oxide film, which is a metastable phase and has a corundum crystal structure, is preferred because it has the largest band gap. In addition, γ-type gallium oxide film, which is a metastable phase and has a cubic defect spinel structure, δ-type gallium oxide film, which has a cubic bixbyite structure, and ε-type gallium oxide film, which is an orthorhombic polar crystal, each have their own reasons for being preferable according to their respective characteristics. Note that the crystal form of the gallium oxide film 130 is easily affected by the crystal form of the gallium oxide layer 120. In other words, the crystal form of the gallium oxide film 130 is likely to be the same as the crystal form of the gallium oxide layer 120. Therefore, when it is desired to make the gallium oxide film 130 a β-type gallium oxide film, it is preferable that the gallium oxide layer 120 also be a β-type gallium oxide layer.

[0032] From the viewpoint of crystallinity, the gallium oxide film 130 is preferably uniaxially oriented.

[0033] The gallium oxide film may be single crystal or polycrystalline. However, from the viewpoint of the yield and characteristics of semiconductor devices, a single crystal or a crystal close to a single crystal is preferred, and a single crystal is more preferred. Furthermore, when a small amount of impurities is mixed to grow an n-type or p-type gallium oxide semiconductor, the gallium oxide film may contain these impurities. In this specification, the crystal structure of a gallium oxide film and whether it is a single crystal film or not can be measured, for example, by a crystal X-ray diffraction (XRD) device using CuKα radiation as a radiation source. The crystal structure of each of the α-type to ε-type films has a unique XRD pattern. Furthermore, if they are single crystals, an XRD pattern specific to the single crystal can be obtained.

[0034] When the gallium oxide film is single crystal, the plane orientation of the gallium oxide film is preferably (100), and more preferably, a (100) plane-oriented gallium oxide film is provided on a (100) plane-oriented Si single crystal substrate via a gallium layer, and even more preferably, a (100) plane-oriented gallium oxide film is provided on a (100) plane-oriented Si single crystal substrate via a (100) plane-oriented gallium oxide layer. The gallium oxide film here is more preferably a β-type gallium oxide film, and it is particularly preferred that both the gallium oxide layer and the gallium oxide film are β-type gallium oxide.

[0035] For the gallium oxide film of this embodiment, the presence or absence of a peak by symmetrical X-ray diffraction can be used as an index of the crystallinity of a single crystal film. For example, for a β-type gallium oxide film, the presence or absence of a peak of β-type gallium oxide attributed to the (100) plane can be used. The observation of this peak can confirm that heteroepitaxial growth has occurred. Examples of the peak of β-type gallium oxide attributed to the (100) plane include peaks of the (400) plane, the (600) plane, and the (800) plane.

[0036] Symmetric X-ray diffraction measurement is performed, for example, by using CuKα radiation as a radiation source, irradiating the surface of the Si single crystal substrate with the Bragg diffraction angle θ as the incident angle of the X-ray, and rotating the detector at θ-2θ to measure the diffracted X-ray. ２ O ３ The (400) plane has a Bragg diffraction angle 2θ = 30.07° ± 0.5°, and Ga ２ O ３ The (600) plane has a diffraction peak at a Bragg diffraction angle 2θ=44.7°±0.5°. Therefore, if a diffraction peak is obtained at the above Bragg diffraction angle, it can be attributed to the peak of the (100) plane of β-type gallium oxide.

[0037] The arithmetic mean surface roughness Ra of the gallium oxide film in this embodiment is preferably 4.5 nm or less. Here, from the viewpoint of improving the flatness of the gallium oxide film and realizing higher pressure resistance, the arithmetic mean surface roughness Ra is preferably 4.5 nm or less, more preferably 4.0 nm or less, and even more preferably 3.0 nm or less. The smaller the better, but it is usually 0.1 nm or more. The arithmetic mean surface roughness Ra of the gallium oxide film in this specification can be measured using an atomic force microscope (AFM).

[0038] The thickness of the gallium oxide film in this embodiment is preferably 0.1 to 50 μm, more preferably 0.5 to 50 μm, even more preferably 0.8 to 30 μm, and particularly preferably 1 to 20 μm. Here, from the viewpoint of application to power devices and the like, the thickness is preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 0.8 μm or more, and particularly preferably 1 μm or more. In addition, although there are no particular upper limits, from the viewpoint of film formation rate and film quality, the thickness is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less. The thickness can be measured using a scanning electron microscope (SEM) or the like on a cross section of the substrate with a gallium oxide film.

[0039] <Gallium Oxide Film-Coated Substrate> The gallium oxide film-coated substrate according to this embodiment exhibits the effects of the present invention only with the Si single crystal substrate, the gallium oxide layer, and the gallium oxide film, but does not exclude embodiments in which other optional layers are included. Examples of other optional layers include a buffer layer, a nucleation layer, a surface modification layer, etc.

[0040] The buffer layer is a layer inserted mainly for the purpose of alleviating lattice constant mismatch, and is, for example, a single crystal film of the material of interest with a predetermined thickness, a layer formed by gradually changing the composition of a mixed crystal of the material and a different material, or a layer grown with a superlattice structure of the material of interest and a different material, etc. The buffer layer usually has a thickness of 20 nm or more.

[0041] The nucleation layer and the surface modification layer are layers provided for the purpose of promoting the crystallization of gallium oxide, and differ from the buffer layer in terms of crystallinity.

[0042] The nucleation layer refers to a thin film having a lattice constant different from that of the adsorption layer or the material. The thickness of the nucleation layer is, for example, less than 20 nm, preferably less than 10 nm, and more preferably less than 5 nm. The nucleation layer may be a continuous layer or a discontinuous layer. The presence of the nucleation layer can be determined from the difference in atomic arrangement observed by cross-sectional TEM (transmission electron microscope). If no change in atomic arrangement is observed, it can be determined that the Si single crystal substrate and the gallium oxide film are in direct contact via the gallium oxide layer.

[0043] Examples of the surface-modified layer include a layer containing an element different from that of the substrate, or a layer formed by modifying the surface of a substrate, etc. In other words, the surface-modified layer is a layer formed by modifying the surface of a substrate such as a single crystal substrate, and has a lattice constant different from that of the substrate material.

[0044] The breakdown voltage of the gallium oxide film-attached substrate according to this embodiment is preferably more than 120 V / μm, more preferably 125 V / μm or more, and even more preferably 130 V / μm or more, with the higher the better. In this specification, the breakdown voltage is a value measured by the method described in the examples below.

[0045] The lattice constant mismatch ratio between the Si single crystal substrate and the gallium oxide film formed via the gallium oxide layer is preferably 15% or less, more preferably 12% or less, even more preferably 8% or less, and particularly preferably 5% or less. The lower the ratio, the more preferable, but it is greater than the lattice constant mismatch ratio between the Si single crystal substrate and the gallium oxide layer. The lattice constant mismatch ratio between the Si single crystal substrate and the gallium oxide film formed via the gallium oxide layer may be, for example, 3% or more, or 4% or more. The lattice constant mismatch ratio is determined by analyzing the epitaxial relationship between the gallium oxide layer and the gallium oxide film on the Si single crystal substrate from the results of symmetric X-ray diffraction measurement and in-plane X-ray diffraction measurement. The lattice constant mismatch ratio is the ratio of the lattice constant difference of the gallium oxide film in the same direction to the lattice constant of the Si single crystal substrate, and can be calculated, for example, from the ratio between the lattice constant of the Si single crystal substrate and the lattice constant of the gallium oxide single crystal film projected in a certain direction onto the Si single crystal substrate.

[0046] <<Method for Producing a Gallium Oxide Film-Coated Substrate>> The method for producing the <<Gallium Oxide Film-Coated Substrate>> is not particularly limited as long as it can produce a gallium oxide film-coated substrate having a Si single crystal substrate, a gallium oxide layer provided on the Si single crystal substrate, and a gallium oxide film provided on the gallium oxide layer. Here, the atomic arrangement of the gallium oxide layer matches that of the Si single crystal substrate.

[0047] One embodiment of the manufacturing method includes a method for manufacturing a substrate with a gallium oxide film, which includes the following steps 1 and 2: Step 1: placing a Si single crystal substrate inside a reaction chamber, and supplying elemental gallium and oxygen radicals into the reaction chamber in this order at least once each to grow a gallium oxide layer on the surface of the Si single crystal substrate; Step 2: generating plasma from a mixed gas containing oxygen and ozone, dissociating the ozone into oxygen constituent particles, and supplying the ozone into the reaction chamber under reduced pressure, while also supplying elemental gallium into the reaction chamber, to epitaxially grow a gallium oxide film on the surface of the gallium oxide layer.

[0048] Furthermore, it is preferable to include the following step 0 before the above step 1. Step 0: Step of cleaning the Si single crystal substrate However, if the Si single crystal substrate is very clean to begin with and cleaning it may lead to contamination, it is preferable to use the Si single crystal substrate as is without cleaning it.

[0049] Prior to describing each step, one embodiment of the manufacturing apparatus to be used will be described with reference to Fig. 2. Note that the manufacturing apparatus to be used in the manufacturing method according to this embodiment is not limited to the one described below.

[0050] <Manufacturing Apparatus> The manufacturing method according to this embodiment can use, for example, a manufacturing apparatus 1000 shown in the schematic configuration diagram of Fig. 2. The manufacturing apparatus 1000 includes a reaction chamber 1100, a substrate placement unit 1200, a gallium element supply device 1300, an oxygen element supply device 1400, and a heating device 1220.

[0051] The reaction chamber 1100 is a place where a gallium oxide layer 120 and a gallium oxide film 130 are epitaxially grown on a Si single crystal substrate 110. The reaction chamber 1100 is provided with a substrate placement section 1200 and a susceptor 1210 inside. The Si single crystal substrate 110 is placed in the substrate placement section 1200 and supported by the susceptor 1210.

[0052] The substrate placement section 1200 in the reaction chamber 1100 can be heated by a heating device 1220, allowing the Si single crystal substrate 110 to be set to a desired temperature. The heating device can preferably set the temperature of the substrate placement section 1200 to 0°C or higher, and preferably to room temperature or higher. There is no particular upper limit to the heating temperature, but it is sufficient if the substrate placement section 1200 can be heated to, for example, 700°C.

[0053] Gallium element (Ga) is supplied to the placed Si single crystal substrate 110 by a gallium element supply device 1300, and then oxygen radicals are supplied by an oxygen element supply device 1400. This allows a gallium oxide layer 120 to grow on the surface of the Si single crystal substrate 110. The oxygen radicals will be described later.

[0054] The gallium element supply device 1300 is not particularly limited as long as it can supply elemental gallium, and an example thereof is a Knudsen cell. In the case of a Knudsen cell, the gallium element supply device 1300 has a shutter 1310, which allows or blocks communication between the gallium element supply device 1300 and the reaction chamber 1100. The gallium element supply device 1300 may have a heating device or a cooling device.

[0055] Gallium elements are supplied to the Si single crystal substrate 110 on which the gallium layer formed as described above in the same manner as above, and oxygen radicals are supplied by an oxygen element supply device 1400. This oxygen element supply device 1400 has a plasma generation unit 1450 and, if necessary, a shutter 1410. The shutter 1410 connects or disconnects the oxygen element supply device 1400 and the reaction chamber 1100. The oxygen element supply device 1400 may have a heating device or a cooling device.

[0056] The oxygen constituent particles supplied by the oxygen element supply device 1400 to the Si single crystal substrate on which the gallium oxide layer has been formed are ozone dissociated when a mixed gas containing oxygen and ozone is converted into plasma by the plasma generation unit 1450. This allows oxygen radicals to be supplied. In this way, the gallium oxide film 130 can be grown on the surface of the gallium oxide layer.

[0057] Specifically, oxygen gas is supplied from an oxygen gas supply unit 1500 toward the oxygen element supply device 1400. The oxygen gas passes through an oxygen gas supply pipe 1810 and flows into the ozonizer 1700 while the flow rate is adjusted by a mass flow controller 1820.

[0058] A portion of the oxygen gas flowing into the ozonizer 1700 is ozonized to form a mixed gas containing oxygen and ozone. An example of such an ozonizer 1700 is a first plasma generator that converts oxygen gas into plasma. Whether growing a gallium oxide layer or a gallium oxide film, the ozonizer 1700 preferably has the ability to adjust the ozone concentration relative to the total of oxygen and ozone to 10% by volume or more, more preferably 20% by volume or more, and even more preferably 25% by volume or more. The upper limit of the ozone concentration is not particularly limited, but is typically 50% by volume or less.

[0059] The mixed gas containing oxygen and ozone generated by the ozonizer 1700 flows into the oxygen element supply device 1400 through an ozone-oxygen mixed gas supply pipe 1830 while the flow rate is adjusted by a mass flow controller 1840. The ozonizer 1700 and the oxygen element supply device 1400 may be directly connected, in which case the ozone-oxygen mixed gas supply pipe 1830 and the mass flow controller 1840 are not necessary.

[0060] In addition to the mixed gas containing oxygen and ozone, an inert gas is supplied to the oxygen element supply device 1400 from an inert gas supply unit 1600. Examples of the inert gas include rare gases such as Ar gas and He gas. However, as long as there is a mixed gas containing oxygen and ozone, the plasma generation described below is possible even without the inert gas, and therefore the supply of the inert gas is optional.

[0061] The inert gas flows from the inert gas supply unit 1600 through the inert gas supply pipe 1850 and into the oxygen element supply device 1400 while the flow rate is adjusted by the mass flow controller 1860 .

[0062] The mixed gas containing oxygen and ozone and the inert gas may flow separately into the oxygen element supply device 1400, or as shown in Fig. 2, both gases may flow into a mixed gas supply pipe 1870 and be supplied in a mixed state to the oxygen element supply device 1400. In other words, the mixed gas supply pipe 1870 is a pipe for supplying a gas in which the mixed gas containing oxygen and ozone and the inert gas are mixed to the oxygen element supply device 1400 for generating plasma.

[0063] If the mixed gas for generating plasma does not contain an inert gas, the inert gas supply unit 1600, the inert gas supply pipe 1850, and the mass flow controller 1860 are not necessary.

[0064] In addition to the above, the manufacturing apparatus 1000 may also include an impurity element supply unit (not shown) that supplies impurities. The impurity element supply unit supplies impurity elements to grow n-type gallium oxide or p-type gallium oxide.

[0065] <Step 0> Step 0 is a step of cleaning the Si single crystal substrate. Conventional cleaning methods can be used, including, for example, a method of cleaning the Si single crystal substrate with a solution and then drying. The solution used for cleaning can be water, an organic solvent, an acid, or the like, and two or more of these may be used in sequence for cleaning. For example, the Si single crystal substrate may be cleaned with an organic solvent and then with an acid. After cleaning, the substrate may be dried as appropriate.

[0066] Examples of organic solvents used for cleaning include acetone, isopropyl alcohol, ethanol, and methanol. Examples of acids used for cleaning include SiO on a Si single crystal substrate. ２ From the viewpoint of removing the above, hydrofluoric acid and the like can be mentioned.

[0067] In addition to the above, cleaning may be performed by, for example, plasma irradiation, which is preferably performed by irradiating a mixed gas containing nitrogen gas and hydrogen gas in the form of plasma.

[0068] <Step 1> In step 1, a Si single crystal substrate is placed inside a reaction chamber, and gallium elemental gas and oxygen radicals are supplied to the reaction chamber in this order at least once each to grow a gallium oxide layer on the surface of the Si single crystal substrate.

[0069] Specifically, in step 1, first, a Si single crystal substrate 110 is placed inside a reaction chamber 1100. That is, the Si single crystal substrate 110 is placed on a substrate placement part 1200 and supported by a susceptor 1210. Then, the substrate placement part 1200 is heated using a heating device 1220 to heat the Si single crystal substrate 110 to a desired temperature, and the pressure in the reaction chamber 1100 is reduced in preparation for the subsequent step 2.

[0070] Before forming the gallium oxide layer 120, any of the other layers described above may be provided on the surface of the Si single crystal substrate 110, or the gallium oxide layer 120 may be formed directly on the surface of the Si single crystal substrate 110.

[0071] After placing the Si single crystal substrate inside the reaction chamber 1100, elemental gallium is supplied to the reaction chamber 1100 under reduced pressure. That is, elemental gallium (Ga) is supplied from a gallium element supply device 1300 to the reaction chamber 1100 under reduced pressure. Next, oxygen radicals are supplied from an oxygen element supply device 1400 to the reaction chamber 1100. As a result, a gallium oxide layer grows on the surface of the Si single crystal substrate 110 due to the supplied Ga and oxygen radicals. The supply of elemental gallium and oxygen radicals may be carried out once each, but may also be carried out repeatedly multiple times.

[0072] In this case, it is preferable to provide a gallium oxide layer on the Si single crystal substrate 110 oriented in the (100) plane.

[0073] When growing the gallium oxide layer, the Ga gas pressure supplied from the gallium element supply device 1300 is 1.0×10 －６ ~5.0 x 10 －３ Pa is preferred, 5.0 × 10 －６ ~1.0 x 10 －３ Pa is more preferable, and 1.0 × 10 －５ ~1.0 x 10 －４ From the viewpoint of supplying a sufficient amount of Ga element, the gas pressure is more preferably 1.0×10 Pa. －６ Pa or more is preferable, and 5.0 × 10 －６ Pa or more is more preferable, and 1.0 × 10 －５ The gas pressure is more preferably 5.0×10 Pa or more. －３ Pa or less, and 1.0 × 10 －３ Pa or less, and 1.0 × 10 －４ Pa or less is more preferable.

[0074] The substrate temperature when supplying gallium element is preferably 600°C or less, more preferably 200 to 600°C, even more preferably 200 to 500°C, even more preferably 200 to 400°C, may be 200 to 350°C, or may be 200 to 300°C. Here, from the viewpoint of growing crystals, the film formation temperature is preferably 0°C or more, may be 10°C or more, or may be about room temperature or higher, i.e., 20°C or more, and preferably 200°C or more. Furthermore, from the viewpoint of growth rate, the film formation temperature is preferably 600°C or less, more preferably 500°C or less, even more preferably 400°C or less, particularly preferably 350°C or less, and may be 300°C or less.

[0075] The rate of temperature increase when raising the temperature to the growth temperature is preferably 1 to 20°C / min. From the viewpoint of process throughput, the rate of temperature increase is preferably 1°C / min or more, more preferably 8°C / min or more. From the viewpoint of uniform heating, the heating rate is preferably 20°C / min or less, more preferably 18°C / min or less, even more preferably 15°C / min or less, and still more preferably 12°C / min or less.

[0076] The time for supplying the gallium element varies depending on the growth temperature, but is preferably 10 to 60 seconds when the substrate temperature is 300°C. Here, the time is preferably 10 seconds or more, more preferably 15 seconds or more, even more preferably 20 seconds or more, and even more preferably 25 seconds or more. The time is preferably 60 seconds or less, more preferably 50 seconds or less, even more preferably 40 seconds or less, and even more preferably 35 seconds or less.

[0077] Next, the supply of Ga from the gallium element supply device 1300 is stopped, and oxygen radicals are supplied from the oxygen element supply device 1400 to the reaction chamber 1100. Here, a mixed gas containing oxygen and ozone is turned into plasma, and the ozone is dissociated into oxygen constituent particles, which are supplied to the reaction chamber under reduced pressure, thereby growing a gallium oxide layer.

[0078] Specifically, as described above, a portion of the oxygen gas supplied from the oxygen gas supply unit 1500 to the ozonizer 1700 is plasma-treated by the first plasma generated by the ozonizer 1700 to become ozone, thereby obtaining a mixed gas containing oxygen and ozone. This mixed gas is then supplied to the oxygen element supply device 1400 via the mixed gas supply pipe 1870.

[0079] Then, the second plasma generated by the plasma generating unit 1450 in the oxygen element supply device 1400 mainly decomposes ozone into oxygen molecules and singlet oxygen atoms O( １ It is believed that oxygen radicals with strong oxidizing power containing a large amount of singlet oxygen atoms O( １ D) and triplet oxygen atom O( ３ P) and singlet oxygen atom O( １ D) converts triplet oxygen atoms O( ３ P).

[0080] Ozone dissociated into oxygen molecules and oxygen radicals in this way is called oxygen-constituting particles, and is supplied to the reduced pressure reaction chamber 1100. Note that this does not exclude the possibility of supplying not only oxygen-constituting particles but also a mixed gas containing non-plasmaized oxygen and ozone to the reduced pressure reaction chamber 1100.

[0081] In this way, a gallium oxide layer that is aligned with the atomic arrangement of the Si single crystal substrate is formed by supplying elemental gallium and then oxygen radicals. The alignment can be adjusted by controlling the supply rate of elemental gallium (gallium partial pressure, supply time) and the supply conditions of oxygen radicals (radical energy, supply rate, etc.).

[0082] An inert gas such as Ar gas is supplied from the inert gas supply unit 1600 to the oxygen element supply device 1400 via a mixed gas supply pipe 1870. In this case, the mixed gas containing oxygen and ozone and the inert gas are mixed inside the mixed gas supply pipe 1870 to become a mixed gas containing oxygen, ozone, and the inert gas.

[0083] The ratio of the mixed gas containing oxygen and ozone to the inert gas is preferably 230 to 1900 parts by volume, more preferably 230 to 1500 parts by volume, even more preferably 350 to 1000 parts by volume, and even more preferably 350 to 460 parts by volume, when the mixed gas containing oxygen and ozone is taken as 100 parts by volume. Here, from the viewpoint of plasma ignition, the ratio of the inert gas is preferably 230 parts by volume or more, and more preferably 350 parts by volume or more. Furthermore, from the viewpoint of oxygen radical density, the ratio of the inert gas is preferably 1900 parts by volume or less, more preferably 1500 parts by volume or less, even more preferably 1000 parts by volume or less, and even more preferably 460 parts by volume or less.

[0084] The temperature when supplying oxygen radicals, i.e., the growth temperature at which the gallium oxide layer is grown, is preferably the same as the temperature at which the oxygen radicals are subsequently grown. That is, 600°C or less is preferable, 200 to 600°C is more preferable, 200 to 500°C is even more preferable, 200 to 400°C is even more preferable, 200 to 350°C may be, or 200 to 300°C may be. Here, from the viewpoint of growing crystals, the film formation temperature is preferably 0°C or higher, 10°C or higher, or about room temperature or higher, i.e., 20°C or higher, preferably 200°C or higher. Furthermore, from the viewpoint of growth rate, the film formation temperature is preferably 600°C or lower, more preferably 500°C or lower, more preferably 400°C or lower, particularly preferably 350°C or lower, and may be 300°C or lower.

[0085] The growth temperature is preferably the same as the temperature at which elemental gallium is supplied, from the viewpoint of preventing decomposition of the produced gallium oxide and impurity contamination, which may occur when the temperature is changed.

[0086] The time for supplying the oxygen radicals, i.e., the growth time for growing the gallium oxide layer, is preferably 10 to 60 seconds, more preferably 10 to 50 seconds. Here, from the viewpoint of converting all Ga to gallium oxide, the growth time is preferably 10 seconds or more, more preferably 15 seconds or more, even more preferably 20 seconds or more, and even more preferably 30 seconds or more. Furthermore, from the viewpoint of preventing the generated gallium oxide from becoming oxygen-rich, the growth time is preferably 60 seconds or less, more preferably 55 seconds or less, even more preferably 50 seconds or less, and even more preferably 45 seconds or less. The combination of the growth temperature and growth time for growing the gallium oxide layer is preferably 200 to 600°C and 10 to 50 seconds.

[0087] After oxygen radicals are supplied from the oxygen element supply device 1400, the supply of oxygen radicals may be stopped, Ga may be supplied again from the gallium element supply device 1300, and then oxygen radicals may be supplied from the oxygen element supply device 1400, thereby forming a further gallium oxide layer. By repeating this supply of gallium elements and oxygen radicals, the thickness of the gallium oxide layer can be adjusted.

[0088] For example, when the thickness of the gallium oxide layer is about 2 to 4 nm, it is sufficient to supply elemental gallium and oxygen radicals once each, and when the thickness of the gallium oxide layer is about 4500 nm, it is preferable to supply elemental gallium and oxygen radicals twice or more each.

[0089] When the gallium oxide layer is grown, the state of the crystal surface, specifically, the crystallinity and surface flatness, can be examined by reflection high energy electron diffraction (RHEED). Specifically, the surface structure during growth of the gallium oxide layer can be observed in situ by molecular beam epitaxy (MBE).

[0090] In the manufacturing method according to this embodiment, it is preferable that the reflection high-energy electron diffraction pattern (RHEED pattern) of the gallium oxide layer when observed in situ using the MBE method is streaky, which means that the crystal surface of the grown gallium oxide layer is flat and made up of small domains including antiphase boundaries.

[0091] In the subsequent step 2, a mixed gas containing oxygen and ozone is converted into plasma to dissociate the ozone into oxygen-containing particles, which are then supplied to the reaction chamber under reduced pressure, and elemental gallium is also supplied to the reaction chamber, thereby epitaxially growing a gallium oxide film on the surface of the gallium oxide layer.

[0092] Specifically, as described above, a portion of the oxygen gas supplied from the oxygen gas supply unit 1500 to the ozonizer 1700 is plasma-treated by the first plasma generated by the ozonizer 1700 to become ozone, thereby obtaining a mixed gas containing oxygen and ozone. This mixed gas is then supplied to the oxygen element supply device 1400 via the mixed gas supply pipe 1870.

[0093] The concentration of ozone relative to the total of oxygen and ozone is preferably 10% by volume or more, more preferably 20% by volume or more, and even more preferably 25% by volume or more, using the Ozonizer 1700. The upper limit of the volume is not particularly limited, but is usually 50% by volume or less.

[0094] The mixed gas supplied to the oxygen element supply device 1400 via the mixed gas supply pipe 1870 is mainly decomposed into ozone by the second plasma generated by the plasma generation unit 1450 in the oxygen element supply device 1400, and the decomposition is converted into oxygen molecules and singlet oxygen atoms O( １ It is believed that oxygen radicals with strong oxidizing power containing a large amount of singlet oxygen atoms O( １ D) and triplet oxygen atom O( ３ P) and singlet oxygen atom O( １ D) converts triplet oxygen atoms O( ３ P).

[0095] Ozone dissociated into oxygen molecules and oxygen radicals in this way is called oxygen-constituting particles, and is supplied to the reduced pressure reaction chamber 1100. Note that this does not exclude the possibility of supplying not only oxygen-constituting particles but also a mixed gas containing non-plasmaized oxygen and ozone to the reduced pressure reaction chamber 1100.

[0096] In step 2, in addition to the above, elemental gallium is supplied to the reduced pressure reaction chamber 1100. That is, elemental gallium (Ga) is supplied from a gallium element supply device 1300 to the reduced pressure reaction chamber 1100. As a result, the supplied Ga reacts with the oxygen radicals and the like provided above on the surface of the gallium oxide layer grown in step 1, and a flat gallium oxide film is epitaxially grown on the surface of the gallium oxide layer.

[0097] Specifically, Ga and singlet oxygen atoms or singlet oxygen atoms O( １ D) transitioned to triplet oxygen atom O( ３ P) reacts with the gallium oxide film to grow. Many singlet oxygen atoms or singlet oxygen atoms O( １ D) transitioned to triplet oxygen atom O( ３ When the P reaches the gallium oxide film, a gallium oxide film having excellent crystallinity and flatness is grown.

[0098] Here, compared to the case where a gallium oxide film is directly formed on a Si single crystal substrate, when a gallium oxide layer whose atomic arrangement is consistent with that of the Si single crystal substrate is used, the crystallinity of the gallium oxide film is increased, and extremely high pressure resistance can be achieved when used in a semiconductor. As mentioned above, this is presumed to be due to the fact that, when a gallium oxide film is formed, the oxygen atoms constituting the gallium oxide are likely to be stacked on the gallium oxide layer first. As a result, it is thought that the arrangement of the Ga atoms and O atoms constituting the gallium oxide is likely to be regularly arranged, and the crystallinity of the gallium oxide film is enhanced.

[0099] In addition to the above, the deposition rate of the gallium oxide film is faster than the deposition rate of the gallium oxide film when using conventional manufacturing equipment.

[0100] In step 2, the gas pressure of O supplied from the oxygen element supply device 1400 containing oxygen constituent particles is 1.0×10 －５ ~1.0 x 10 －１ Pa is preferred, and 1.0 x 10 －４ ~1.0 x 10 －１ Pa is more preferable, and 1.0 × 10 －３ ~1.0 x 10 －２ From the viewpoint of supplying a sufficient amount of oxygen radicals, the gas pressure is preferably 1.0×10 Pa. －５ Pa or more is preferable, and 1.0 × 10 －４ Pa or more is more preferable, and 1.0 × 10 －３ From the viewpoint of generating sufficient oxygen radicals, the gas pressure is more preferably 1.0×10 Pa or more. －１ Pa or less, and 1.0 × 10 －２ Pa or less is more preferable.

[0101] In step 2, the gas pressure of Ga supplied from the gallium element supply device 1300 is 1.0×10 －５ ~1.0 x 10 －２ Pa is preferred, 5.0 × 10 －５ ~1.0 x 10 －２ Pa is more preferable, and 1.0 × 10 －４ ~1.0 x 10 －３ From the viewpoint of supplying a sufficient amount of Ga element, the gas pressure is more preferably 1.0×10 Pa. －５Pa or more is preferable, and 5.0 × 10 －５ Pa or more is more preferable, and 1.0 × 10 －４ In order to prevent the Ga deposition rate from becoming too high and becoming uncontrollable, the gas pressure is preferably 1.0×10 Pa or more. －２ Pa or less, and 1.0 × 10 －３ Pa or less is more preferable.

[0102] In step 2, the internal pressure of the reaction chamber 1100 is preferably 0.001 to 0.01 Pa, and more preferably 0.006 to 0.009 Pa. From the viewpoint of the exhaust capacity of the apparatus, the internal pressure is preferably 0.001 Pa or more, and more preferably 0.006 Pa or more. Furthermore, from the viewpoint of the mean free path of oxygen radicals and gallium, the internal pressure is preferably 0.01 Pa or less, and more preferably 0.009 Pa or less.

[0103] The temperature of the Si single crystal substrate 110 on which the gallium oxide layer is formed, i.e., the film formation temperature for epitaxial growth of the gallium oxide film, is preferably 600°C or less, more preferably 0 to 600°C, even more preferably 10 to 500°C, even more preferably 20 to 400°C, and may be 200 to 350°C or 200 to 300°C. 200 to 600°C is also more preferable. Here, from the viewpoint of growing the crystal, the film formation temperature is preferably 0°C or higher, and may be 10°C or higher, or about room temperature or higher, i.e., 20°C or higher, preferably 200°C or higher. Furthermore, from the viewpoint of growth rate, the film formation temperature is preferably 600°C or lower, more preferably 500°C or lower, even more preferably 400°C or lower, even more preferably 350°C or lower, and particularly preferably 300°C or lower. Furthermore, it is preferable that the temperature be the same as the growth temperature of the gallium oxide layer from the viewpoint of preventing decomposition of the generated gallium oxide and impurity contamination that may occur when the temperature is changed.

[0104] The lattice constant mismatch rate of the obtained gallium oxide film with the Si single crystal substrate is preferably 15% or less, more preferably 12% or less, even more preferably 8% or less, and particularly preferably 5% or less. The lower the rate, the more preferable, but it is greater than the lattice constant mismatch rate between the Si single crystal substrate and the gallium oxide layer. The lattice constant mismatch rate of the gallium oxide film with the Si single crystal substrate may be, for example, 3% or more, or 4% or more. The lattice constant mismatch rate is uniquely determined from the epitaxial relationship that is physically optimal due to the binding energy between the single crystal constituent elements and the constituent elements of gallium oxide with respect to the Si single crystal substrate.

[0105] Preferred embodiments of the gallium oxide film are the same as those of the <Gallium Oxide Film> in the above <<Substrate with Gallium Oxide Film>>. For example, the thickness of the gallium oxide film is preferably 0.5 to 50 μm, more preferably 0.8 to 30 μm, and even more preferably 1 to 20 μm. Here, from the viewpoint of the withstand voltage for application to power devices and the like, the thickness is preferably 0.5 μm or more, more preferably 0.8 μm or more, and even more preferably 1 μm or more. Furthermore, although there are no particular upper limits, from the viewpoint of the film formation rate and film quality, the thickness is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less.

[0106] The arithmetic mean surface roughness Ra of the gallium oxide film is preferably 4.5 nm or less. From the viewpoint of improving the flatness of the gallium oxide film and realizing higher pressure resistance, the arithmetic mean surface roughness Ra is preferably 4.5 nm or less, more preferably 4.0 nm or less, and even more preferably 3.0 nm or less. The smaller the better, but it is usually 0.1 nm or more.

[0107] The gallium oxide film is preferably a β-type gallium oxide film from the viewpoint that it is the most stable phase and is expected to be useful in industrial applications, however, the gallium oxide film in this embodiment is not limited to a β-type gallium oxide film.

[0108] When the gallium oxide film is single crystal, the plane orientation of the gallium oxide film is preferably (100), and more preferably, a gallium oxide film having a (100) plane orientation is provided on a Si single crystal substrate having a (100) plane orientation via a gallium oxide layer, and even more preferably, a gallium oxide film having a (100) plane orientation is provided on a Si single crystal substrate having a (100) plane orientation via a gallium oxide layer. The gallium oxide film here is more preferably a β-type gallium oxide film.

[0109] The withstand voltage of the gallium oxide film-attached substrate according to this embodiment is preferably more than 120 V / μm, more preferably 125 V / μm or more, and even more preferably 130 V / μm or more, with the higher the better.

[0110] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these. Here, Example 1 is an example, Example 2 is a reference example, and Example 3 is a comparative example.

[0111] Examples 1 to 3: Production of a substrate with a gallium oxide film Example 1 Using the production apparatus 1000 shown in FIG. 2 , a gallium oxide layer was grown on a Si single crystal substrate according to the following procedure, and then a gallium oxide film was epitaxially grown to obtain a substrate with a gallium oxide film. Specifically, the Si single crystal substrate was first washed with an organic solvent, then washed with acid, and then dried. Next, the Si single crystal substrate was placed on the substrate placement unit 1200 with the (100) plane facing up, and supported by a susceptor 1210. The temperature of the Si single crystal substrate was heated to 300°C at a heating rate of 10°C / min. Then, Ga was added at a pressure of 6.1 × 10 －６ Pa was supplied from the gallium element supply device 1300 to the reaction chamber 1100 for 30 seconds. After the supply of Ga elements was stopped, oxygen constituent particles including oxygen radicals were supplied from the oxygen element supply device 1400 to the reaction chamber 1100 for 40 seconds while maintaining the same pressure and temperature, thereby growing a gallium oxide layer on the surface of the Si single crystal substrate.

[0112] When supplying the oxygen-composed particles, oxygen gas was supplied from the oxygen gas supply unit using an ozonizer 1700, and a mixed gas containing oxygen and ozone, with the ozone concentration relative to the total of oxygen and ozone set to 28 volume %, was supplied into the oxygen element supply device 1400. At the same time, Ar gas was also supplied from the inert gas supply unit 1600 into the oxygen element supply device 1400. The ratio of the mixed gas containing oxygen and ozone to Ar gas was 1:4.

[0113] After that, O ２ and O ３ at a flow rate of 1.5 sccm O ２ +O ３ At the same time, oxygen plasma treatment was carried out on the Si single crystal substrate for 40 seconds at a plasma output of 600 W. This allowed the gallium oxide layer to grow.

[0114] Then, while maintaining the same pressure and temperature, O ２ and O ３ Flow rate of 8 sccm O ２ +O ３ Oxygen constituent particles were supplied into the reaction chamber 1100 under the same conditions as those used for growing the gallium oxide layer, except that oxygen plasma treatment was performed at a plasma output of 1000 W and a pressure of 1.13 × 10 －４ Pa was further supplied from a gallium element supply device 1300 to the reaction chamber 1100 to grow a gallium oxide film. In this way, a substrate with a gallium oxide film was obtained.

[0115] Example 2 A Si single crystal substrate was prepared in the same manner as in Example 1 and supported by a susceptor 1210. Next, the temperature of the Si single crystal substrate was heated to 500°C at a rate of 10°C / min. Ga was then added at a pressure of 6.1 x 10 －６ Pa was supplied from the gallium element supply device 1300 to the reaction chamber 1100, and a gallium layer was grown on the surface of the Si single crystal substrate for 30 seconds. Next, with the supply of Ga temporarily stopped, the temperature of the Si single crystal substrate was lowered to 300°C at a cooling rate of 10°C / min. Then, a gallium oxide film was grown on the gallium layer under the same conditions as in Example 1. As a result, a substrate with a gallium oxide film was obtained.

[0116] Example 3 A Si single crystal substrate was prepared in the same manner as in Example 1 and supported by a susceptor 1210. Next, without growing a gallium oxide layer or a gallium layer, a gallium oxide film was grown directly on the Si single crystal substrate under the same conditions as in Example 1. In this manner, a substrate with a gallium oxide film was obtained.

[0117] <Evaluation> <Gallium oxide film> The surfaces and cross sections of the gallium oxide film-coated substrates of Examples 1 to 3 obtained above were observed with a scanning electron microscope on the gallium oxide film side. An SEM image of the surface of the gallium oxide film of Example 1 is shown in Figure 3(a) (magnification: 20,000 times), and an SEM image of the cross section of the gallium oxide film is shown in Figure 3(b) (magnification: 20,000 times). As a result, it was confirmed that the gallium oxide film of Example 1 had higher flatness than that of Example 2 and higher flatness than that of Example 3.

[0118] In addition, the surfaces of the gallium oxide film side of the gallium oxide film-coated substrates in Examples 1 to 3 were also observed at room temperature using an atomic force microscope. An AFM image of the gallium oxide film surface of Example 1 is shown in FIG. 4(a) (scanning range: 5 × 5 μm), and a bird's-eye view of the gallium oxide film surface is shown in FIG. 4(b) (scanning range: 5 × 5 μm). As a result, it was confirmed that the gallium oxide film of Example 1 had higher flatness than that of Example 2 and higher flatness than that of Example 3. The arithmetic mean surface roughness Ra of the gallium oxide film was also determined using AFM. The results are shown in Table 1.

[0119] <Gallium Oxide Layer> For Example 1, an RHEED pattern was obtained by in-situ observation using MBE while the gallium oxide layer was growing. The results are shown in Figure 5. From this, it was confirmed that the gallium oxide layer of Example 1 was streaky.

[0120] <Gallium oxide film-coated substrate> Symmetric X-ray diffraction measurement was performed on the gallium oxide film-coated substrate of Example 1. CuKα radiation was used as the radiation source, and the X-rays were irradiated at a Bragg diffraction angle θ relative to the Si surface at an incident angle, and the diffracted X-rays were measured by rotating the detector at θ-2θ to measure the diffraction angle. In the obtained diffraction pattern, in addition to the peak of the Si (200) plane and the peak of the Si (400) plane, a peak of the β-type gallium oxide (400) plane was observed at 2θ = 30.07 °, and a peak of the β-type gallium oxide (600) plane was observed at 2θ = 44.7 °. This clearly showed that the gallium oxide film in the obtained gallium oxide film-coated substrate was a single crystal film of β-type gallium oxide.

[0121] In-plane X-ray diffraction measurements were performed on the gallium oxide film-coated substrate. A CuKα ray was used as the radiation source, and the X-rays were irradiated at a minute angle of 0.3° relative to the Si surface. The X-rays diffracted in a direction perpendicular to the normal direction of the Si single crystal substrate were rotated at θ-2θ to measure the diffraction angle. In the obtained pattern, a peak of the β-type gallium oxide (00-3) plane was observed at 2θ = 48.05°, approximately 26° clockwise from the

[010] direction of Si. This further confirmed that a β-type gallium oxide single crystal had been formed as the gallium oxide film, and also clarified that there was an epitaxial relationship between the Si single crystal substrate and the β-type gallium oxide film.

[0122] From the results of the above X-ray diffraction measurement, it can be said that the plane orientation of the β-type gallium oxide single crystal film epitaxially grown on the (100)-oriented Si single crystal substrate via a gallium oxide layer is (100).

[0123] <Breach of Pressure> The gallium oxide film-coated substrates of Examples 1 to 3 were immersed in Fluorinert, a fluorine-based inert liquid with pressure resistance, and Al foil was attached to the backside, and a W needle was contacted with the front side to measure the breakdown pressure. The results are shown in Table 1. For reference, the breakdown pressure of the gallium oxide film-coated substrates, which were formed by using a gallium oxide substrate as the substrate and growing a gallium oxide film thereon, was 62 to 64 V / μm.

[0124]

[0125] As described above, the gallium oxide film-coated substrate according to this embodiment has a gallium oxide film provided on a Si single crystal substrate via a gallium oxide layer whose atomic arrangement matches that of the Si single crystal substrate, and therefore has excellent pressure resistance when used in a semiconductor.

[0126] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2023-159112) filed on September 22, 2023, the contents of which are incorporated herein by reference.

[0127] REFERENCE SIGNS LIST 100 gallium oxide film-coated substrate 110 Si single crystal substrate 110a first main surface 120 gallium oxide layer 130 gallium oxide film 1000 manufacturing apparatus 1100 reaction chamber 1200 substrate placement unit 1210 susceptor 1220 heating device 1300 gallium element supply device 1310, 1410 shutter 1400 oxygen element supply device 1450 plasma generation unit 1500 oxygen gas supply unit 1600 inert gas supply unit 1700 ozonizer 1810 oxygen gas supply pipe 1820, 1840, 1860 mass flow controller 1830 ozone-oxygen mixed gas supply pipe 1850 inert gas supply pipe 1870 mixed gas supply pipe

Claims

1. A substrate with a gallium oxide film, comprising: a Si single crystal substrate; a gallium oxide layer provided on the Si single crystal substrate; and a gallium oxide film provided on the gallium oxide layer, wherein the gallium oxide layer has an atomic arrangement that matches that of the Si single crystal substrate.

2. The gallium oxide film-attached substrate according to claim 1, wherein the arithmetic mean surface roughness Ra of the gallium oxide film is 4.5 nm or less.

3. The substrate with a gallium oxide film according to claim 1 or 2, wherein the gallium oxide layer has a thickness of 0.1 to 1000 nm.

4. The gallium oxide film-attached substrate according to claim 1 or 2, having a breakdown voltage of more than 120 V / μm.

5. The gallium oxide film-attached substrate according to claim 1 or 2, wherein the gallium oxide film is a β-type gallium oxide film.

6. A substrate with a gallium oxide film according to claim 1 or 2, wherein the gallium oxide layer is provided on the Si single crystal substrate having a (100) plane orientation.

7. The substrate with a gallium oxide film according to claim 6, wherein the plane orientation of the gallium oxide film is (100).

8. The substrate with a gallium oxide film according to claim 6, wherein the surface orientation of the gallium oxide layer is (100).

9. A method for manufacturing a substrate with a gallium oxide film, comprising the steps of: placing a Si single crystal substrate inside a reaction chamber; supplying gallium element and oxygen radicals in this order at least once each into the reaction chamber to grow a gallium oxide layer on a surface of the Si single crystal substrate; and plasmatizing a mixed gas containing oxygen and ozone to dissociate the ozone into oxygen constituent particles, supplying the plasma to the reaction chamber under reduced pressure, and simultaneously supplying gallium element to the reaction chamber to epitaxially grow a gallium oxide film on the surface of the gallium oxide layer.

10. The method for producing a substrate with a gallium oxide film according to claim 9, wherein the Si single crystal substrate is cleaned and then placed inside the reaction chamber.

11. The method for producing a substrate with a gallium oxide film according to claim 9 or 10, wherein a reflection high energy electron diffraction pattern when the gallium oxide layer is grown is streaky.

12. The method for producing a gallium oxide film-attached substrate according to claim 9 or 10, wherein the growth temperature for growing the gallium oxide layer is 200 to 600° C.

13. The method for producing a gallium oxide film-attached substrate according to claim 12, wherein the growth time for growing the gallium oxide layer is 10 to 50 seconds.

14. The method for producing a gallium oxide film-coated substrate according to claim 9 or 10, wherein the film formation temperature for epitaxially growing the gallium oxide film is 200 to 600°C.

15. The method for producing a gallium oxide film-coated substrate according to claim 9 or 10, wherein the arithmetic mean surface roughness Ra of the gallium oxide film is 4.5 nm or less.

16. The method for producing a gallium oxide film-attached substrate according to claim 9 or 10, wherein the gallium oxide layer is grown to a thickness of 0.1 to 1000 nm.

17. The method for producing a substrate with a gallium oxide film according to claim 9 or 10, wherein the resulting substrate with a gallium oxide film has a withstand voltage of more than 120 V / μm.

18. The method for producing a substrate with a gallium oxide film according to claim 9 or 10, wherein the gallium oxide film is a β-type gallium oxide film.

19. The method for producing a substrate with a gallium oxide film according to claim 9 or 10, wherein the gallium oxide layer is provided on the Si single crystal substrate having a (100) plane orientation.

20. The method for producing a gallium oxide film-coated substrate according to claim 19, wherein the plane orientation of the gallium oxide film is (100).

21. The method for producing a gallium oxide film-attached substrate according to claim 19, wherein the plane orientation of the gallium oxide layer is (100).

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