Substrate with gallium oxide film and method for manufacturing same

Abstract

The present invention relates to a substrate with a gallium oxide film, the substrate comprising: a Si single crystal substrate; a gallium layer provided on the Si single crystal substrate; and a gallium oxide film provided on the gallium layer.

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 grown heteroepitaxially 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 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 layer, thereby completing 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 layer provided on the Si single crystal substrate, and a gallium oxide film provided on the gallium layer. [2] The gallium oxide film-coated substrate according to [1] above, wherein the arithmetic mean surface roughness Ra of the gallium oxide film is 4.5 nm or less. [3] The gallium oxide film-coated substrate according to [1] or [2] above, wherein the gallium layer has a thickness of 0.1 to 50 nm. [4] The gallium oxide film-coated substrate according to any one of [1] to [3] above, wherein the breakdown voltage exceeds 100 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 gallium oxide film-coated substrate according to any one of [1] to [5] above, wherein the gallium oxide layer is provided on the Si single crystal substrate having a (100) plane orientation. [7] The gallium oxide film-attached substrate according to any one of [1] to [6], wherein the plane orientation of the gallium oxide film is (100).

[0014] [8] 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; supplying elemental gallium into the reaction chamber; and growing a gallium 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-constituting particles, supplying the ozone into the reaction chamber under reduced pressure, and simultaneously supplying elemental gallium into the reaction chamber, thereby epitaxially growing a gallium oxide film on the surface of the gallium layer. [9] A method for producing a gallium oxide film-coated substrate according to [8], wherein the Si single crystal substrate is cleaned and then placed inside the reaction chamber.

[10] A method for producing a gallium oxide film-coated substrate according to [8] or [9], wherein the reflection high-energy electron diffraction pattern obtained when the gallium layer is grown is streaky.

[11] A method for producing a gallium oxide film-coated substrate according to any one of [8] to

[10] , wherein the growth temperature for growing the gallium layer is greater than 200°C and not greater than 680°C.

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

[11] above, wherein the growth time for growing the gallium oxide layer is 5 to 25 seconds.

[13] The method for producing a gallium oxide film-coated substrate according to any one of [8] to

[12] above, wherein the film formation temperature for epitaxially growing the gallium oxide film is 600°C or less.

[14] The method for producing a gallium oxide film-coated substrate according to any one of [8] to

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

[15] The method for producing a gallium oxide film-coated substrate according to any one of [8] to

[14] above, wherein the gallium oxide layer is grown to a thickness of 0.1 to 50 nm.

[16] The method for producing a gallium oxide film-coated substrate according to any one of [8] to

[15] above, wherein the resulting gallium oxide film-coated substrate has a breakdown voltage of more than 100 V / μm.

[17] The method for producing a gallium oxide film-coated substrate according to any one of [8] to

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

[18] The method for producing a gallium oxide film-coated substrate according to any one of [8] to

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

[19] The method for producing a gallium oxide film-coated substrate according to any one of [8] to

[18] above, wherein the plane orientation of the gallium oxide film is (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 2, where (a) of Fig. 3 is an SEM image of the surface of the gallium oxide film-coated substrate observed at a magnification of 5,000 times, (b) of Fig. 3 is an SEM image of the surface of the gallium oxide film-coated substrate observed at a magnification of 100,000 times, and (c) 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 shows AFM images of the gallium oxide film-coated substrate obtained in Example 2, where Fig. 4(a) is an AFM image of the gallium oxide film-coated substrate surface in a scanning range of 5 × 5 μm, Fig. 4(b) is an AFM image of the gallium oxide film-coated substrate surface in a scanning range of 1 × 1 μm, and Fig. 4(c) is an AFM bird's-eye view of the gallium oxide film-coated substrate surface in a scanning range of 5 × 5 μm. Fig. 5 shows a RHEED pattern observed in situ using the MBE method when a gallium layer was grown on a Si single crystal substrate in Example 2.

[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] <<Substrate with Gallium Oxide Film>> As shown in FIG. 1 , the substrate with a gallium oxide film 100 according to this embodiment has a Si single crystal substrate 110, a gallium layer 120 provided on the Si single crystal substrate 110, and a gallium oxide film 130 provided on the gallium layer 120.

[0019] The gallium 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 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 layer 120 is preferably provided.

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

[0023] However, the gallium 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 gallium layer is more preferably uniaxially oriented, and even more preferably single crystal. The crystallinity of the gallium layer can be determined by X-ray diffraction, transmission electron diffraction, reflection high-energy electron diffraction (RHEED), or the like.

[0025] In this embodiment, it was found that providing the gallium 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 good pressure resistance when applied to a semiconductor.

[0026] The reason why the above effect is obtained by using the gallium layer 120 is not clear, but it is thought to be as follows. Compared to forming a gallium oxide film directly on a Si single crystal substrate, when a gallium layer, i.e., a layer made of gallium, is used, the oxygen atoms that make up the gallium oxide are more likely to be deposited on the gallium layer first when the gallium oxide film is formed. As a result, it is thought that the Ga atoms and O atoms that make up the gallium oxide are more likely to be arranged regularly, and the crystallinity of the gallium oxide film is enhanced. It is thought that the high crystallinity of this gallium oxide film contributes to the realization of high breakdown voltage when used in a semiconductor.

[0027] The thickness of the gallium layer 120 in this embodiment is preferably 0.1 to 50 nm. Here, in order to improve the crystallinity of the gallium oxide film 130 provided on the gallium layer 120, the gallium layer 120 should be approximately one atomic layer thick or more. From this perspective, the thickness is preferably 0.1 nm or more, more preferably 0.2 nm or more, and preferably 0.25 nm or more. On the other hand, from the perspective that the thinner the better, the film thickness is preferably 50 nm or less, more preferably 15 nm or less, even more preferably 10 nm or less, even more preferably 5 nm or less, and particularly preferably 3 nm or less. The thickness of the gallium layer 120 can be measured by observing a cross section of the substrate with a gallium oxide film using a field emission scanning electron microscope (FE-SEM)-energy dispersive X-ray spectroscopy (EDX) method or a transmission electron microscope (TEM).

[0028] <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 layer 120.

[0029] 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 suitability according to their respective characteristics.

[0030] From the viewpoint of crystallinity, the gallium oxide film 130 is preferably uniaxially oriented.

[0031] 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.

[0032] When the gallium oxide film is single crystal, the plane orientation of the gallium oxide film is preferably (100), and more preferably, the gallium oxide film having a (100) plane orientation is provided on a Si single crystal substrate having a (100) plane orientation via a gallium layer. The gallium oxide film here is more preferably a β-type gallium oxide film.

[0033] 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.

[0034] 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.

[0035] 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).

[0036] 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.

[0037] <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 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.

[0038] 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.

[0039] 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.

[0040] 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 layer.

[0041] 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.

[0042] The breakdown voltage of the gallium oxide film-attached substrate according to this embodiment is preferably more than 100 V / μm, more preferably 120 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.

[0043] The lattice constant mismatch ratio between the Si single crystal substrate and the gallium oxide film formed via the gallium layer is preferably 15% or less, more preferably 12% or less, and even more preferably 8% or less. The lower the ratio, the better, but it is usually greater than 0%. The lattice constant mismatch ratio is determined by analyzing the epitaxial relationship between the gallium 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.

[0044] <<Method for Producing Gallium Oxide Film-Coated Substrate>> There are no particular limitations on the method for producing the <<Gallium Oxide Film-Coated Substrate>> as long as it can produce a gallium oxide film-coated substrate having a Si single crystal substrate, a gallium layer provided on the Si single crystal substrate, and a gallium oxide film provided on the gallium layer.

[0045] 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 into the reaction chamber to grow a gallium layer on the surface of the Si single crystal substrate; Step 2: generating plasma from a mixed gas containing oxygen and ozone to dissociate the ozone into oxygen constituent particles and supplying them 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 layer.

[0046] 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.

[0047] 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.

[0048] <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.

[0049] The reaction chamber 1100 is a place where a gallium 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 on the substrate placement section 1200 and supported by the susceptor 1210.

[0050] 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.

[0051] Gallium element (Ga) is supplied to the placed Si single crystal substrate 110 by a gallium element supply device 1300. This allows a gallium layer 120 to grow on the surface of the Si single crystal substrate 110. The gallium element supply device 1300 is not particularly limited as long as it can supply gallium element, 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 communication between the gallium element supply device 1300 and the reaction chamber 1100 or blocks communication therebetween. The gallium element supply device 1300 may also have a heating device or a cooling device.

[0052] 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 constituent particles 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.

[0053] The oxygen constituent particles supplied by the oxygen element supply device 1400 to the Si single crystal substrate on which the gallium layer has been formed are ozone dissociated when a mixed gas containing oxygen and ozone is turned into plasma by the plasma generation unit 1450. This allows a gallium oxide film 130 to grow on the surface of the gallium layer.

[0054] 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.

[0055] The oxygen gas flowing into the ozonizer 1700 is partially 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. The ozonizer 1700 preferably has the capacity to make the ozone concentration relative to the total of oxygen and ozone 10% by volume or more, more preferably 20% by volume or more, and even more preferably 25% by volume or more. There is no particular upper limit to the ozone concentration, but it is usually 50% by volume or less.

[0056] 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.

[0057] 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.

[0058] 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 .

[0059] 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.

[0060] 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.

[0061] 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.

[0062] <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.

[0063] Examples of organic solvents used for cleaning include acetone, isopropyl alcohol, ethanol, and methanol. The acid used for cleaning is an acid that removes SiO on the Si single crystal substrate. ２ From the viewpoint of removing the above, hydrofluoric acid is preferable.

[0064] 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.

[0065] <Step 1> In step 1, a Si single crystal substrate is placed inside a reaction chamber, and elemental gallium is supplied into the reaction chamber to grow a gallium layer on the surface of the Si single crystal substrate.

[0066] 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.

[0067] Before forming the gallium 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 layer 120 may be formed directly on the surface of the Si single crystal substrate 110.

[0068] After the Si single crystal substrate is placed 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 the gallium element supply device 1300 to the reaction chamber 1100 under reduced pressure. As a result, a gallium layer grows on the surface of the Si single crystal substrate 110 by the supplied Ga.

[0069] In this case, it is preferable to provide a gallium layer on the Si single crystal substrate 110 oriented in the (100) plane.

[0070] When growing the gallium layer, the 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 4.0 × 10 －６ Pa or more is more preferable, and 5.0 × 10 －６ Pa or more is more preferable, and 8.0 × 10 －６ Pa or more is more preferable, and 1.0 × 10 －５ In order to prevent a large amount of Ga from being deposited, the gas pressure is 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.

[0071] The growth temperature when growing the gallium layer is preferably higher than 200° C. and lower than 680° C. From the viewpoint of growing the gallium layer, the growth temperature is preferably higher than 200° C., more preferably higher than 300° C., even more preferably higher than 400° C., and even more preferably higher than 450° C. From the viewpoint of growth rate, the growth temperature is preferably lower than 680° C., more preferably lower than 650° C., and even more preferably lower than 600° C.

[0072] 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.

[0073] The growth time for growing the gallium layer varies depending on the growth temperature, but is preferably 5 to 25 seconds when the growth temperature is 500°C. From the viewpoint of growing a gallium layer with a thickness of about a monolayer of Ga, the growth time is preferably 5 seconds or more, more preferably 7 seconds or more, and even more preferably 9 seconds or more. Furthermore, from the viewpoint of not depositing more Ga than necessary, the growth time is preferably 25 seconds or less, more preferably 20 seconds or less, and even more preferably 15 seconds or less. The combination of growth temperature and growth time for growing the gallium layer is preferably greater than 200°C and equal to or less than 680°C, and 5 to 25 seconds. In addition, the heating rate for raising the temperature to the growth temperature is more preferably 1 to 20°C / min.

[0074] When the gallium 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 layer can be observed in situ by molecular beam epitaxy (MBE).

[0075] In the manufacturing method according to this embodiment, it is preferable that the reflection high-energy electron diffraction pattern (RHEED pattern) of the gallium layer when observed in situ using the MBE method is streaky, which means that the crystal surface of the grown gallium layer is flat and the crystal is two-dimensional.

[0076] As mentioned above, the thickness of the gallium layer is preferably 0.1 to 50 nm, but this thickness can be adjusted by appropriately changing the growth time and the temperature of the Ga supply source.

[0077] 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 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] 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.

[0080] 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).

[0081] 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.

[0082] 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 layer grown in step 1, and a flat gallium oxide film is epitaxially grown on the surface of the gallium layer.

[0083] 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.

[0084] Here, compared to the case where a gallium oxide film is directly formed on a Si single crystal substrate, the crystallinity of the gallium oxide film is increased by using a gallium layer, and high breakdown voltage 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 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 likely to be improved.

[0085] 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.

[0086] 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.

[0087] 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. －５ Pa 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.

[0088] 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.

[0089] The temperature of the Si single crystal substrate 110 on which the gallium 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 0 to 500°C, even more preferably 0 to 400°C, and may be 10 to 350°C, or may be 20 to 300°C. 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. 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, even more preferably 350°C or less, and particularly preferably 300°C or less.

[0090] When the film formation temperature of the gallium oxide film is lower than the growth temperature of the gallium layer, the gallium oxide film is cooled from the film formation temperature to the growth temperature of the gallium layer, and the cooling rate should be as fast as possible. The cooling rate in cooling after the gallium oxide film formation is, for example, 1 to 20 ° C. / min, preferably 5 to 15 ° C. / min, more preferably 6 to 14 ° C. / min, and even more preferably 8 to 12 ° C. / min. Here, from the viewpoint of process throughput, the cooling rate is preferably 1 ° C. / min or more, more preferably 5 ° C. / min or more, even more preferably 6 ° C. / min or more, and even more preferably 8 ° C. / min or more. Furthermore, from the viewpoint of uniform cooling, the cooling rate is preferably 20 ° C. / min or less, more preferably 15 ° C. / min or less, even more preferably 14 ° C. / min or less, and even more preferably 12 ° C. / min or less.

[0091] 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, and even more preferably 8% or less. The lower the rate, the better, but it is usually more than 0%. The rate of lattice constant mismatch is uniquely determined from the epitaxial relationship that is physically optimal due to the bond energy between the single crystal constituent elements and the constituent elements of gallium oxide with respect to the Si single crystal substrate.

[0092] 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.

[0093] 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 3.5 nm or less. The smaller the better, but it is usually 0.1 nm or more.

[0094] 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.

[0095] When the gallium oxide film is single crystal, the plane orientation of the gallium oxide film is preferably (100), and more preferably, the gallium oxide film having a (100) plane orientation is provided on a Si single crystal substrate having a (100) plane orientation via a gallium layer. The gallium oxide film here is more preferably a β-type gallium oxide film.

[0096] The withstand voltage of the gallium oxide film-attached substrate according to this embodiment is preferably more than 100 V / μm, more preferably 120 V / μm or more, and even more preferably 130 V / μm or more, with the higher the better.

[0097] The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. Example 1 is a comparative example, and Example 2 is an example.

[0098] Example 1: Production of a substrate with a gallium oxide film Using the production apparatus 1000 shown in Figure 2, a gallium 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 the susceptor 1210. The temperature of the Si single crystal substrate was heated to 300°C at a heating rate of 10°C / min.

[0099] Next, an ozonizer 1700 was used to mix oxygen gas supplied from the oxygen gas supply unit with ozone, with the ozone concentration relative to the total of oxygen and ozone being 28% by volume, and this mixed gas containing oxygen and ozone was supplied into the oxygen element supply unit 1400. At the same time, Ar gas was also supplied from the inert gas supply unit 1600 into the oxygen element supply unit 1400. The ratio of the mixed gas containing oxygen and ozone to Ar gas was 1:4.

[0100] After that, O ２ and O ３ at a flow rate of 8 sccm O ２ +O ３ The oxygen element supply device 1400 supplies the gas to the reaction chamber 1100 under reduced pressure. At the same time, the plasma output is set to 1000 W, and Ga is supplied to the reaction chamber 1100 at a pressure of 1.13×10 －４ Pa was further supplied from the gallium element supply device 1300 to the reaction chamber 1100, and a gallium oxide film was grown for 60 minutes. In this way, a substrate with a gallium oxide film was obtained.

[0101] Example 2: Production of a substrate with a gallium oxide film In the same manner as in Example 1, a Si single crystal substrate supported by a susceptor 1210 was heated to 500° C. at a heating rate of 10° C. / min. and, while being maintained at that temperature, the pressure in the reaction chamber 1100 was reduced to 5.0×10 －６ The pressure was reduced to 6.1×10 Pa. －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 10 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. Thereafter, in the same manner as in Example 1, a mixed gas containing oxygen and ozone was supplied into the oxygen element supply device 1400, and simultaneously, Ar gas was also supplied into the oxygen element supply device 1400 from the inert gas supply unit 1600. Then, O ２ and O ３ at a flow rate of 8 sccm O ２ +O ３ The oxygen element supply device 1400 supplies the gas to the reaction chamber 1100 under reduced pressure. At the same time, the plasma output is set to 1000 W, and Ga is supplied to the reaction chamber 1100 at a pressure of 1.13×10 －４ Pa was further supplied from the gallium element supply device 1300 to the reaction chamber 1100, and a gallium oxide film was grown for 60 minutes. In this way, a substrate with a gallium oxide film was obtained.

[0102] <Evaluation> <Gallium oxide film> The surfaces and cross sections of the gallium oxide film-coated substrates of Examples 1 and 2 obtained above were observed using a scanning electron microscope. SEM images of the gallium oxide film surface of Example 2 are shown in Figure 3(a) (magnification: 5,000 times) and Figure 3(b) (magnification: 100,000 times), and an SEM image of the cross section of the gallium oxide film is shown in Figure 3(c) (magnification: 20,000 times). As a result, it was confirmed that the gallium oxide film of Example 2 had higher flatness than that of Example 1.

[0103] In addition, the surfaces of the gallium oxide film side of the gallium oxide film-coated substrates of Examples 1 and 2 were also observed at room temperature using an atomic force microscope. AFM images of the gallium oxide film surface of Example 2 are shown in FIG. 4(a) (scanning range: 5 × 5 μm) and FIG. 5(b) (scanning range: 1 × 1 μm), and a bird's-eye view of the gallium oxide film surface is shown in FIG. 4(c) (scanning range: 5 × 5 μm). As a result, it was confirmed that the gallium oxide film of Example 2 had higher flatness than that of Example 1. The arithmetic mean surface roughness Ra of the gallium oxide film was also determined by AFM. The results are shown in Table 1.

[0104] <Gallium Layer> For Example 2, while the gallium layer was being grown, an in-situ RHEED pattern was obtained by MBE observation. The results are shown in Figure 5. From this, it was confirmed that the gallium layer of Example 2 was streaky.

[0105] <Gallium oxide film-coated substrate> Symmetric X-ray diffraction measurement was performed on the gallium oxide film-coated substrate. 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 on the obtained gallium oxide film-coated substrate was a single crystal film of β-type gallium oxide.

[0106] 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.

[0107] 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 layer is (100).

[0108] <Breach of Pressure> The gallium oxide film-coated substrates of Examples 1 and 2 were immersed in Fluorinert, a fluorine-based inert liquid with a resistance to pressure, and Al foil was attached to the backside. A W needle was then brought into contact with the front side to measure the resistance of the substrate. The results are shown in Table 1. For reference, the resistance of the gallium oxide film-coated substrate, which was formed by growing a gallium oxide film on a gallium oxide substrate, was 62 to 64 V / μm.

[0109]

[0110] From the 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 layer, and therefore has excellent pressure resistance when used in a semiconductor. In addition, the arithmetic mean surface roughness Ra of the gallium oxide film can be reduced, and a gallium oxide film with excellent flatness can be epitaxially grown.

[0111] 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. 2023-159111) filed on September 22, 2023, the contents of which are incorporated herein by reference.

[0112] REFERENCE SIGNS LIST 100 gallium oxide film-coated substrate 110 Si single crystal substrate 110a first main surface 120 gallium 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 layer provided on the Si single crystal substrate; and a gallium oxide film provided on the gallium layer.

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 layer has a thickness of 0.1 to 50 nm.

4. The gallium oxide film-attached substrate according to claim 1 or 2, having a breakdown voltage of more than 100 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 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. 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 to the reaction chamber, and growing a gallium 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-constituting particles, supplying the plasma to the reaction chamber under reduced pressure, and simultaneously supplying gallium element to the reaction chamber, and epitaxially growing a gallium oxide film on the surface of the gallium layer.

9. The method for producing a substrate with a gallium oxide film according to claim 8, wherein the Si single crystal substrate is cleaned and then placed inside the reaction chamber.

10. The method for producing a substrate with a gallium oxide film according to claim 8 or 9, wherein a reflection high energy electron diffraction pattern obtained when the gallium layer is grown is streaky.

11. The method for producing a gallium oxide film-attached substrate according to claim 8 or 9, wherein the growth temperature for growing the gallium layer is higher than 200°C and not higher than 680°C.

12. The method for producing a substrate with a gallium oxide film according to claim 11, wherein the growth time for growing the gallium layer is 5 to 25 seconds.

13. The method for producing a gallium oxide film-coated substrate according to claim 8 or 9, wherein the film formation temperature for epitaxially growing the gallium oxide film is 600° C. or less.

14. The method for producing a gallium oxide film-coated substrate according to claim 8 or 9, wherein the arithmetic mean surface roughness Ra of the gallium oxide film is 4.5 nm or less.

15. The method for producing a substrate with a gallium oxide film according to claim 8 or 9, wherein the gallium layer is grown to a thickness of 0.1 to 50 nm.

16. The method for producing a substrate with a gallium oxide film according to claim 8 or 9, wherein the resulting substrate with a gallium oxide film has a withstand voltage of more than 100 V / μm.

17. The method for producing a gallium oxide film-coated substrate according to claim 8 or 9, wherein the gallium oxide film is a β-type gallium oxide film.

18. The method for producing a substrate with a gallium oxide film according to claim 8 or 9, wherein the gallium layer is provided on the Si single crystal substrate having a (100) plane orientation.

19. The method for producing a gallium oxide film-coated substrate according to claim 18, wherein the plane orientation of the gallium oxide film is (100).

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