Film forming method and film forming apparatus

Abstract

The present invention is a film forming method in which a mist is discharged from a nozzle onto a heated substrate and a crystalline oxide film is formed by an atomizing CVD method, characterized in that: a nozzle including at least two or more opposing air inlets, a gas mixing unit provided with the air inlets, and an air outlet from which the mist is discharged is used as the nozzle; when the volume of the gas mixing unit is set to be V (cm3), the linear velocity L (cm / sec) of the mist at any one of the two or more opposing intake ports is set to be equal to or greater than 0.8 V-200. As a result, it is possible to provide a film-forming method for forming a crystalline oxide film having excellent crystallinity, excellent in-plane film thickness distribution even if the crystalline oxide film has a large area and a thin film thickness, and excellent semiconductor characteristics when applied to a semiconductor device, and a film-forming apparatus for implementing the film-forming method.

Description

Technical Field

[0001] The present invention relates to a film forming method and a film forming device. Background Art

[0002] As the next generation of switching elements that can achieve high withstand voltage, low loss and high heat resistance, semiconductor devices using gallium oxide (Ga2O3) with a large band gap have attracted attention, and are expected to be used in power semiconductor devices such as inverters. In addition, due to its wide band gap, gallium oxide is also expected to be widely used as a light receiving / transmitting device such as LEDs or sensors. In particular, for α-Ga2O3 with a corundum structure in gallium oxide, the band gap can be controlled by using indium or aluminum alone or combining the two to form a mixed crystal, forming an extremely attractive material system as an InAlGaO-based semiconductor. Among them, InAlGaO-based semiconductors refer to In X Al Y Ga Z O3 (0≤X≤2, 0≤Y≤2, 0≤Z≤2, X+Y+Z=1.5~2.5) can be fully regarded as the same material system containing gallium oxide.

[0003] However, since the most stable phase of gallium oxide is the β-gallia structure, it is difficult to form a crystalline film of a corundum structure as a metastable phase without using a special film formation method. For example, in heteroepitaxial growth, the crystal growth conditions are often restricted, so the dislocation density tends to be high. In addition, not only in the case of a crystalline film with a corundum structure, there are still many technical problems in terms of improving the film formation rate and crystal quality, suppressing cracks and abnormal growth, and suppressing the breakage of the substrate caused by twinning and warping. Under such circumstances, some research has been conducted on the film formation of crystalline semiconductors with a corundum structure.

[0004] Patent document 1 describes a method for manufacturing an oxide crystal thin film using bromide or iodide of gallium or indium and using an atomized CVD (Chemical Vapor Deposition) method. Patent documents 2 to 4 describe a multilayer structure formed by stacking a semiconductor layer having a corundum crystal structure and an insulating film having a corundum crystal structure on a base substrate having a corundum crystal structure. In addition, as described in patent documents 5 to 7, film formation using an ELO (Epitaxial Lateral Overgrowth: epitaxial lateral overgrowth) substrate or the formation of a void and implemented by an atomized CVD method has also been studied.

[0005] Patent document 8 describes that at least a gallium raw material and an oxygen raw material are used to form a gallium oxide film having a corundum structure by hydride vapor phase epitaxy (HVPE). In addition, Patent document 9 describes that an ELO crystal is grown using a substrate having a pattern formed thereon to obtain a surface area of ​​9 μm 2 Above and dislocation density is 5×10 6 cm -2 The following crystal membrane.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent No. 5397794

[0009] Patent Document 2: Japanese Patent No. 5343224

[0010] Patent Document 3: Japanese Patent No. 5397795

[0011] Patent Document 4: Japanese Patent Application Laid-Open No. 2014-072533

[0012] Patent Document 5: Japanese Patent Application Publication No. 2016-100592

[0013] Patent Document 6: Japanese Patent Application Publication No. 2016-098166

[0014] Patent Document 7: Japanese Patent Application Publication No. 2016-100593

[0015] Patent Document 8: Japanese Patent Application Laid-Open No. 2016-155714

[0016] Patent Document 9: Japanese Patent Application Publication No. 2019-034883

[0017] Patent Document 10: International Publication No. 2021 / 065940 Summary of the invention

[0018] 1. Technical issues to be resolved

[0019] However, gallium oxide has problems with heat release. To eliminate the heat release problem, for example, the film thickness of gallium oxide needs to be reduced to less than 30 μm. However, the grinding process is complicated and the cost becomes high. Moreover, when thinning by grinding, it is difficult to obtain a large-area gallium oxide film with a maintained film thickness distribution. Moreover, when applied to vertical devices, the series resistance cannot be fully satisfied. Therefore, in order to give full play to the performance of gallium oxide as a power semiconductor device, it is desired to obtain a thin gallium oxide film with a larger area and good film thickness distribution, for example, a film thickness of less than 30 μm, and such a crystalline film is urgently needed.

[0020] In response to the above technical problems, Patent Document 10 discloses a method for obtaining a gallium oxide film with good film thickness distribution using an ELO mask. However, this method requires a stripping process and a grinding process, which are complicated. Due to the complicated process, there is a problem of reduced yield.

[0021] The object of the present invention is to provide a film forming method for forming a crystalline oxide film and a film forming device for implementing the film forming method. The crystalline oxide film has excellent crystallinity, and even if the film is large in area and thin in thickness, the film thickness distribution within the surface is good, and it has excellent semiconductor properties when applied to semiconductor devices.

[0022] (II) Technical solution

[0023] In order to solve the above technical problems, the present invention provides a film forming method, which is a film forming method for forming a crystalline oxide film by spraying mist from a nozzle onto a heated substrate through an atomization CVD method.

[0024] As the nozzle, a nozzle including at least two air inlets facing each other, a gas mixing section having the air inlets, and an air outlet for ejecting the mist is used.

[0025] The volume of the gas mixing unit is V (cm 3 ), the linear velocity L (cm / sec) of the mist at any one of the two or more opposing air inlets is set to L≥0.8V-200.

[0026] According to the above film forming method, a crystalline oxide film having excellent crystallinity and good in-plane thickness distribution can be obtained even with a relatively thin film thickness. In addition, a crystalline oxide film having excellent semiconductor characteristics when used in a semiconductor device can be obtained.

[0027] At this time, as the substrate, a substrate having a diameter of 100 mm to 200 mm can be used.

[0028] According to the film forming method of the present invention, a crystalline oxide film having a good film thickness distribution can be obtained even for such a large-area substrate.

[0029] In this case, the main component of the crystalline oxide film can be gallium oxide.

[0030] According to the above film forming method, a crystalline oxide film having gallium oxide as a main component and having a good in-plane film thickness distribution can be obtained even when the film thickness is relatively thin.

[0031] At this time, the volume V (cm 3 ) is a gas mixing portion with V>250 as the film forming method of the gas mixing portion.

[0032] According to the above-described film forming method, a crystalline oxide film having a more favorable in-plane film thickness distribution can be obtained.

[0033] The present invention also provides a film forming device,

[0034] The device comprises an atomizing section for generating mist, a film forming section for forming a crystalline oxide film, and a nozzle for supplying the mist to the film forming section.

[0035] The nozzle includes at least two or more opposing air inlets, a gas mixing portion having the air inlets, and an air outlet for ejecting the mist.

[0036] The atomizing section and the gas inlet of the gas mixing section are connected via a pipe, and the film forming apparatus further includes a portion where an inner diameter of the pipe near the gas inlet is smaller than an inner diameter of the pipe upstream thereof.

[0037] The above film forming apparatus can implement the above film forming method and can obtain a crystalline oxide film having excellent crystallinity and good in-plane thickness distribution even with a relatively thin film thickness. In addition, a crystalline oxide film having excellent semiconductor properties can be obtained when applied to a semiconductor device.

[0038] At this time, the volume of the gas mixing unit can be set to V (cm 3 ) when V>250.

[0039] According to the above film forming apparatus, it is possible to obtain a film having a better in-plane film thickness distribution.

[0040] Furthermore, the present invention provides a film forming method, which is a film forming method for forming a crystalline oxide film by an atomization CVD method by spraying mist from a nozzle onto a heated substrate.

[0041] As the nozzle, a nozzle including at least two air inlets facing each other, a gas mixing section having the air inlets, and an air outlet for ejecting the mist is used.

[0042] The linear velocity of the mist is increased near the air inlet.

[0043] According to the above film forming method, a crystalline oxide film having excellent crystallinity and good in-plane thickness distribution can be obtained even with a relatively thin film thickness. In addition, a crystalline oxide film having excellent semiconductor characteristics when used in a semiconductor device can be obtained.

[0044] At this time, the volume of the gas mixing unit is set to V (cm 3), the linear velocity L (cm / sec) of the mist at any one of the two or more opposing air inlets can be set to L≥0.8V-200.

[0045] According to the above-described film forming method, a crystalline oxide film having a more favorable in-plane film thickness distribution can be obtained.

[0046] At this time, the volume V (cm 3 ) is a gas mixing portion with V>250 as the film forming method of the gas mixing portion.

[0047] According to the above-described film forming method, a crystalline oxide film having a more favorable in-plane film thickness distribution can be obtained.

[0048] At this time, as the substrate, a substrate having a diameter of 100 mm to 200 mm can be used.

[0049] According to the film forming method of the present invention, a crystalline oxide film having a good film thickness distribution can be obtained even for such a large-area substrate.

[0050] In this case, the main component of the crystalline oxide film can be gallium oxide.

[0051] According to the above film forming method, a crystalline oxide film having gallium oxide as a main component and having a good in-plane film thickness distribution can be obtained even when the film thickness is relatively thin.

[0052] (III) Beneficial effects

[0053] As described above, according to the film forming method of the present invention, a crystalline oxide film with gallium oxide as the main component can be formed, which has excellent crystallinity, good film thickness distribution in the plane even with a relatively thin film thickness, and excellent semiconductor properties when applied to a semiconductor device. According to the film forming device of the present invention, it is a film forming device that can implement the above-mentioned film forming method and obtain a crystalline oxide film with gallium oxide as the main component, which has excellent crystallinity and good film thickness distribution in the plane even with a relatively thin film thickness. According to the crystalline oxide film formed in the above manner, the film thickness distribution is good, and when a power semiconductor device is manufactured, the performance of the crystalline oxide film can be fully utilized, and the performance deviation can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is a diagram for explaining an example of a nozzle that can be used in the present invention.

[0055] Figure 2 This is a diagram for explaining another example of the nozzle that can be used in the present invention.

[0056] Figure 3This is a schematic structural diagram showing an example of a semiconductor device using the stacked structure of the present invention.

[0057] Figure 4 This is a schematic structural diagram showing an example of a film forming apparatus (atomization CVD apparatus) suitable for forming a film of the laminated structure of the present invention.

[0058] Figure 5 This is a diagram for explaining an example of an atomizing unit used in the present invention.

[0059] Figure 6 This is a diagram for explaining an example in which the area of ​​the opening in the nozzle that can be used for the nozzle of the present invention is 50% or less of the area of ​​the partition wall.

[0060] Figure 7 This is a diagram for explaining an example in which the area of ​​the opening in the nozzle that can be used for the nozzle of the present invention is larger than 50% of the area of ​​the partition wall.

[0061] Figure 8 This is a diagram for explaining an example of a nozzle without a partition wall in the nozzle that can be used in the present invention. DETAILED DESCRIPTION

[0062] As described above, it is necessary to provide a film forming method for forming a crystalline oxide film and a film forming device for implementing the film forming method. The crystalline oxide film has excellent crystallinity, and even if the film is large in area and thin in thickness, the film thickness distribution within the surface is good, and it has excellent semiconductor properties when applied to semiconductor devices.

[0063] In view of the above technical problems, the inventors of the present invention have repeatedly conducted in-depth studies and found that a crystalline oxide film with excellent crystallinity and good film thickness distribution in a plane even with a relatively thin film thickness can be obtained by the following film forming method. When applied to a semiconductor device, the crystalline oxide film has excellent semiconductor properties, thereby completing the present invention. The film forming method is a film forming method in which mist is sprayed from a nozzle onto a heated substrate and a crystalline oxide film is formed by an atomized CVD method, characterized in that the nozzle has two or more opposing air inlets, a gas mixing section having the air inlets, and an air outlet for spraying the mist, and the volume of the gas mixing section is set to V (cm 3 ), the linear velocity L (cm / sec) at any one of the two or more air inlets is L≥0.8V-200.

[0064] In addition, the inventors of the present invention also discovered that a crystalline oxide film with excellent crystallinity and good in-plane film thickness distribution even with a relatively thin film thickness can be obtained by using the following film-forming device, thereby completing the present invention. The film-forming device is characterized in that it comprises a nozzle, a film-forming section, and an atomizing section for generating mist, the nozzle comprising at least two or more relative air inlets, a gas mixing section having the air inlets, and an air outlet for spraying mist, the atomizing section and the air inlet of the gas mixing section are connected by a pipe, and the film-forming device further comprises a portion where the inner diameter of the pipe near the air inlet is smaller than the inner diameter of the pipe upstream thereof.

[0065] Furthermore, the inventors of the present invention discovered that a crystalline oxide film having excellent crystallinity and good in-plane film thickness distribution even with a relatively thin film thickness can be obtained by the following film forming method, and the crystalline oxide film having excellent semiconductor properties when applied to a semiconductor device, thereby completing the present invention. The film forming method is a film forming method in which mist is sprayed from a nozzle onto a heated substrate and a crystalline oxide film is formed by an atomization CVD method, and is characterized in that the nozzle includes at least two or more relative air inlets, a gas mixing section having the air inlets, and an air outlet for spraying mist, so that the linear velocity of the mist increases near the air inlets.

[0066] That is, the present invention is a film forming method for forming a crystalline oxide film by an atomization CVD method by spraying mist from a nozzle onto a heated substrate.

[0067] As the nozzle, a nozzle including at least two air inlets facing each other, a gas mixing section having the air inlets, and an air outlet for ejecting the mist is used.

[0068] The volume of the gas mixing unit is V (cm 3 ), the linear velocity L (cm / sec) of the mist at any one of the two or more opposing air inlets is set to L≥0.8V-200.

[0069] Furthermore, the present invention is a film forming device,

[0070] The device comprises an atomizing section for generating mist, a film forming section for forming a crystalline oxide film, and a nozzle for supplying the mist to the film forming section.

[0071] The nozzle includes at least two or more opposing air inlets, a gas mixing portion having the air inlets, and an air outlet for ejecting the mist.

[0072] The atomizing section and the gas inlet of the gas mixing section are connected via a pipe, and the film forming apparatus further includes a portion where an inner diameter of the pipe near the gas inlet is smaller than an inner diameter of the pipe upstream thereof.

[0073] Furthermore, the present invention is a film forming method, which is a film forming method for forming a crystalline oxide film by an atomization CVD method by spraying mist from a nozzle onto a heated substrate.

[0074] As the nozzle, a nozzle including at least two air inlets facing each other, a gas mixing section having the air inlets, and an air outlet for ejecting the mist is used.

[0075] The linear velocity of the mist is increased near the air inlet.

[0076] Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

[0077] (Crystalline Oxide Film)

[0078] The film thickness distribution of the crystalline oxide film of the present invention is good. Regarding the film thickness distribution, as long as the value obtained by ((maximum film thickness - minimum film thickness) / (maximum film thickness + minimum film thickness))×100(%) for the film thickness at 25 points in the plane is less than 10%, it can be considered good. More preferably, as long as it is less than 5%, it is considered good. The above-mentioned crystalline oxide film of the present invention can fully exert the performance of the crystalline oxide film when it is made into a power semiconductor device, and can suppress the deviation of the performance.

[0079] Generally, a crystalline oxide film is composed of a metal and oxygen, but for the crystalline oxide film of the present invention, it is preferred that gallium is used as the main component as the metal. In addition, in the present invention, "gallium oxide is used as the main component" means that 50 to 100% of the metal component is gallium. As a metal component other than gallium, for example, one or more metals selected from iron, indium, aluminum, vanadium, titanium, chromium, rhodium, iridium, nickel and cobalt may be included.

[0080] The crystalline oxide film may also contain doping elements. For example, n-type dopants such as tin, germanium, silicon, titanium, zirconium, vanadium, or niobium; or p-type dopants such as copper, silver, tin, iridium, rhodium, or magnesium may be listed, without particular limitation. The concentration of the dopant may be, for example, about 1×10 16 / cm 3 ~1×10 22 / cm 3 , can be set to about 1×10 17 / cm 3 The following low concentrations can also be set to about 1×10 20 / cm 3 Above high concentration.

[0081] The crystal structure of the crystalline oxide film is not particularly limited, and may be a β-gallia structure, a corundum structure, or an orthorhombic crystal. A variety of crystal structures may be mixed, and may be polycrystalline, but preferably a single crystal or a uniaxially oriented film. It can be determined to be a single crystal or a uniaxially oriented film by an X-ray diffraction device or an electron diffraction device. If the film is irradiated with X-rays or electron beams, a diffraction image corresponding to the crystal structure can be obtained. If it is uniaxially oriented, only specific diffraction peaks will appear. Thus, it can be judged as uniaxially oriented.

[0082] The film thickness of the crystalline oxide film is not particularly limited, but is preferably 0.1 μm or more. The upper limit is not particularly limited. For example, it can be 100 μm or less, preferably 50 μm or less, and more preferably 30 μm or less. The film thickness can be measured by using a probe profiler or a spectral reflection film thickness meter, an ellipsometer, and observing the cross section using a SEM (Scanning Electron Microscope) or a TEM (Transmission Electron Microscope), and can be any of the above methods.

[0083] The crystalline oxide film can be obtained by forming a film using a mist CVD method using a mist CVD apparatus (film forming apparatus) described later.

[0084] (Substrate)

[0085] The substrate (base substrate) for forming a crystalline oxide film of the present invention is not particularly limited as long as it is a substrate that becomes the support body of the above-mentioned crystalline oxide film. The material is not particularly limited, and a known substrate can be used, which can be an organic compound or an inorganic compound. For example, polysulfone, polyethersulfone, polyphenylene sulfide, polyetheretherketone, polyimide, polyetherimide, fluororesin, iron or aluminum, stainless steel, gold and other metals, quartz, glass, calcium carbonate, gallium oxide, ZnO, etc. can be listed. In addition, single crystal substrates such as silicon, sapphire or lithium tantalate, lithium niobate, SiC, GaN, iron oxide, chromium oxide, etc. can also be listed, and this single crystal substrate is more desired in the present invention. Thus, a crystalline oxide film with better quality can be obtained. In particular, the price of sapphire substrates, lithium tantalate substrates, and lithium niobate substrates is relatively cheap, which is more advantageous in industry.

[0086] The thickness of the base substrate is preferably 100 to 5000 μm. Within the above range, handling is easy, and thermal resistance can be suppressed during film formation, so that a film of good quality can be easily obtained.

[0087] There is no particular limit to the size of the substrate, but if the area of ​​the substrate is 100 mm 2More than, or the diameter is 2 inches (50mm) or more, then a large-area film with good crystallinity can be obtained, so it is preferred. In addition, if the diameter of the substrate is set to 4 inches (100mm) to 8 inches (200mm), it is easy to use existing processing equipment for processing the obtained crystalline oxide film, which is industrially advantageous when manufacturing semiconductor devices. In addition, it will become a crystalline oxide film with a large area and excellent film thickness distribution, and excellent semiconductor properties when applied to semiconductor devices. For example, when a semiconductor device such as a power semiconductor device is manufactured from the above-mentioned crystalline oxide film, a product batch containing more than two of the semiconductor devices can make its withstand voltage yield more than 75%.

[0088] There may also be other layers between the substrate and the crystalline oxide film. Other layers refer to layers whose composition is different from that of the substrate and the outermost crystalline oxide film, and are also called buffer layers. The buffer layer can be any one of an oxide semiconductor film, an insulating film, a metal film, etc. As its material, for example, Al2O3, Ga2O3, Cr2O3, Fe2O3, In2O3, Rh2O3, V2O3, Ti2O3, Ir2O3, etc. are suitable. The thickness of the buffer layer is preferably 0.1μm~2μm.

[0089] (Configuration Example of Semiconductor Device)

[0090] A preferred example of a semiconductor device 100 using a crystalline oxide film of the present invention is shown in FIG. Figure 3 .exist Figure 3In the example, a crystalline oxide film 103 is formed on a substrate 101, thereby forming a stacked structure 110. The crystalline oxide film 103 is formed by stacking an insulating film 103a and a conductive film 103b in order from the substrate 101 side. A gate insulating film 105 is formed on a surface 103c on the conductive film 103b. A gate electrode 107 is formed on the gate insulating film 105. In addition, on the surface 103c on the conductive film 103b, a source-drain electrode 109 is formed in a manner that sandwiches the gate electrode 107. According to the above-mentioned structure, by applying a gate voltage to the gate electrode 107, the depletion layer formed in the conductive film 103b can be controlled, making the operation of the transistor (FET (Field Effect Transistor: field effect transistor) device) possible. As semiconductor devices formed by using the stacked structure of the present invention, transistors such as MIS (Metal-Insulator-Semiconductor: metal-insulator-semiconductor structure transistor) or HEMT (High Electron Mobility Transistor: high electron mobility transistor), IGBT (Insulate-Gate Bipolar Transistor: insulated gate bipolar transistor), TFT (Thin Film Transistor: thin film transistor), Schottky barrier diodes using semiconductor-metal junctions (Schottky Barrier Diodes), PN or PIN diodes combined with other P layers, and light receiving / emitting elements can be listed. The stacked structure of the present invention can be used to improve the characteristics of these devices.

[0091] The following describes the film forming apparatus and method of the present invention for forming a crystalline oxide film by atomization CVD. The term "mist" in the present invention is a general term for liquid particles dispersed in a gas, including substances called mist, droplets, and the like.

[0092] (Film forming device)

[0093] Figure 4 Schematically shows a film forming apparatus 201 for forming a film by an atomization CVD method. The film forming apparatus 201 comprises at least: an atomizing unit 220 for atomizing a raw material solution 204a to generate mist, a carrier gas supply unit 230 for supplying a carrier gas for conveying the mist, a supply pipe 209 for connecting the atomizing unit 220 and a film forming chamber 207 and conveying the mist by the carrier gas, a film forming chamber 207 for heat-treating the mist to form a film on a substrate 210, and a nozzle 250 for ejecting the mist supplied together with the carrier gas from the supply pipe 209 onto the substrate. In addition, a top plate for rectifying the supplied mist on the substrate may be provided.

[0094] (Atomization part)

[0095] In the atomizing section 220, the raw material solution 204a is atomized to generate mist. The atomizing method is not particularly limited as long as the raw material solution 204a can be atomized, and can be a known atomizing method, preferably an atomizing method based on ultrasonic vibration. This is because atomization can be performed more stably.

[0096] An example of the atomizing unit 220 is shown in FIG. Figure 5 . The atomization section 220 includes: a mist generating source 204 that contains a raw material solution 204a; a container 205 containing a medium that can conduct ultrasonic vibrations, such as water 205a; and an ultrasonic vibrator 206 installed on the bottom surface of the container 205. Specifically, the mist generating source 204 composed of a container containing the raw material solution 204a can be stored in the container 205 containing water 205a by using a support body (not shown in the figure). The ultrasonic vibrator 206 can be installed at the bottom of the container 205, and the ultrasonic vibrator 206 can also be connected to the oscillator 216. In addition, it can be configured as follows: if the oscillator 216 is started, the ultrasonic vibrator 206 vibrates, and the ultrasonic wave is transmitted in the mist generating source 204 through the water 205a, and the raw material solution 204a is atomized.

[0097] (Raw material solution)

[0098] As long as the raw material solution 204a can be atomized, the material contained in the solution is not particularly limited, and it can be an inorganic material or an organic material. As a material, a metal or a metal compound can be used appropriately. For example, a material containing one or more metals selected from gallium, iron, indium, aluminum, vanadium, titanium, chromium, rhodium, nickel and cobalt can be used. As the above-mentioned raw material solution, a solution in which the metal is dissolved or dispersed in an organic solvent or water in the form of a complex or a salt can be used appropriately. As the form of the salt, for example, halides such as metal chloride salts, metal bromide salts, and metal iodide salts can be listed. In addition, a solution in which the above-mentioned metal is dissolved in hydrogen halides such as hydrobromic acid, hydrochloric acid, and hydroiodic acid can also be used as a salt solution. As the form of the complex, for example, acetylacetone complexes, carbonyl complexes, ammonia complexes, hydride complexes, etc. can be listed. By mixing acetylacetone in the solution of the above-mentioned salt, acetylacetone complexes can also be formed. The metal concentration in the raw material solution 204a is not particularly limited, and can be set to 0.005 to 1 mol / L, etc. The temperature during mixing and dissolving is preferably 20°C or higher.

[0099] Additives such as halogenated hydrochloric acid and oxidizing agent may also be mixed in the raw material solution. As halogenated hydrochloric acid, for example, hydrobromic acid, hydrochloric acid, hydroiodic acid, etc. may be listed, wherein hydrobromic acid or hydroiodic acid is preferred. As oxidizing agent, for example, peroxides such as hydrogen peroxide (H2O2), sodium peroxide (Na2O2), barium peroxide (BaO2), benzoyl peroxide (C6H5CO)2O2, hypochlorous acid (HClO), perchloric acid, nitric acid, ozone water, peracetic acid or organic peroxides such as nitrobenzene may be listed.

[0100] The raw material solution may contain a dopant. The dopant is not particularly limited. For example, n-type dopants such as tin, germanium, silicon, titanium, zirconium, vanadium, or niobium; or p-type dopants such as copper, silver, tin, iridium, rhodium, or magnesium can be listed.

[0101] (Carrier gas supply unit)

[0102] like Figure 4 As shown, the carrier gas supply unit 230 has a carrier gas source 202a for supplying carrier gas. At this time, a flow control valve 203a for adjusting the flow rate of the carrier gas sent from the carrier gas source 202a can be provided. In addition, a dilution carrier gas source 202b for supplying a dilution carrier gas and a flow control valve 203b for adjusting the flow rate of the dilution carrier gas sent from the dilution carrier gas source 202b can also be provided as needed. In addition, in the present invention, the sum of the carrier gas flow rate and the dilution carrier gas flow rate is referred to as the total carrier gas flow rate.

[0103] The type of carrier gas is not particularly limited and can be appropriately selected according to the film-forming material. For example, inert gases such as oxygen, ozone, nitrogen or argon, or reducing gases such as hydrogen, nitrogen-hydrogen mixed gas (forming gas), etc. can be listed. In addition, the type of carrier gas can be one or more than two. For example, as the second carrier gas, a dilution gas obtained by diluting the same gas as the first carrier gas with a gas other than the gas (for example, diluting 10 times) can be further used, and air can also be used. The flow rate of the total carrier gas is not particularly limited. For example, when film formation is performed on a substrate with a diameter of 2 inches (about 50 mm), the flow rate of the total carrier gas is preferably set to 0.05~50L / minute, and more preferably set to 5~20L / minute.

[0104] (Supply pipe)

[0105] The film forming device 201 has a supply pipe 209 connecting the mist generating unit 220 and the film forming chamber 207. At this time, mist is transported by the carrier gas from the mist generating source 204 of the mist generating unit 220 through the supply pipe 209 and supplied into the film forming chamber 207. The supply pipe 209 can be made of, for example, a quartz tube, a glass tube, or a resin tube.

[0106] (Film Forming Room)

[0107] As the film forming unit provided in the film forming apparatus of the present invention, for example, a film forming chamber 207 can be cited. A substrate 210 is provided in the film forming chamber 207, and a heater 208 for heating the substrate 210 can be provided. The heater 208 can be as follows: Figure 4 Although shown as being provided outside the film forming chamber 207, it may be provided inside the film forming chamber 207. The mist supplied from the supply pipe 209 passes through the pipe in the film forming chamber 207 and is ejected toward the substrate 210 from the nozzle 250 together with the carrier gas.

[0108] The film forming device of the present invention comprises a nozzle 250 including at least two opposing air inlets, a gas mixing section having the air inlets, and an air outlet for ejecting the mist, and a portion where the inner diameter of the pipe near the air inlet is smaller than the inner diameter of the pipe upstream thereof. An example of a nozzle having opposing air inlets is shown in Figure 1 , 2 .

[0109] Typically, the nozzle has an air inlet and an air outlet, and the two are continuous in space. In the present application, the nozzle 250 can be divided into a space including the air inlet 502 and a space including the air outlet 501 by a partition wall provided with an opening. In this case, as long as the opening area is less than 50% of the area of ​​the partition wall, the space including the air inlet 502 can be set as the gas mixing section 500, and the space including the air outlet 501 can be set as the gas discharge section. An example in which the area of ​​the opening 510 in the nozzle is less than 50% of the area of ​​the partition wall (including the opening) is shown in Figure 6 The gas mixing unit 500 has the following function: the gas entering from the gas inlet 502 is retained, stirred, and sent to the gas discharge unit.

[0110] On the other hand, when the opening area is larger than 50% of the partition wall area, or there is no partition wall, the nozzle 250 is regarded as a gas mixing unit 500 as a whole. Figure 7 , an example without partition walls is shown in Figure 8 In the present invention, Figure 7 , Figure 8 The nozzle 250 is regarded as a gas mixing unit 500 as a whole.

[0111] The shape of the air outlet 501 is not limited, and can be a slit-shaped, square, or circular shape as shown in the figure. In the present invention, there are more than two air inlets 502, and they are opposite to each other. Usually, the air inlets are connected to the pipes. As long as the normals extending from the center of the pipe (the center of gravity when it is not circular) to the two air inlets are roughly consistent, it can be considered that the air inlets of the nozzle are opposite to each other.

[0112] The inner diameter of the piping is usually 10 to 80 mm, but is not limited thereto. In the present invention, there is a portion where the inner diameter of the piping near the air inlet is smaller than the inner diameter of the piping upstream thereof. For example, if the inner diameter of the piping is 10 mm, an opening of about 1 to 9 mm can be provided in the piping, or a reducer or the like can be used to tighten the inner diameter of the piping. The vicinity of the air inlet refers to a portion approximately 0 to 10 cm away from the air inlet. The portion where the inner diameter of the piping is smaller than the inner diameter of the piping upstream thereof will be provided near each air inlet.

[0113] By reducing the inner diameter of the pipe, the linear velocity of the gas can be increased, and by making the air inlets 502 face each other, the mist can be evenly dispersed in the nozzle. As a result, the density of the mist ejected from the nozzle (air outlet 501) becomes uniform, and the obtained film thickness also becomes uniform. In addition, the volume V (cm 3 ) It is preferred that V>250. This allows the mist to be more uniformly dispersed in the nozzle, and the obtained film thickness also becomes uniform.

[0114] The distance between the opposing air inlets is not particularly limited, but if it is too close, the mist dispersion will be poor and the film thickness distribution will be poor. Therefore, it is preferred that the distance is about the same as the substrate diameter or longer than the substrate diameter.

[0115] In the film forming chamber 207, an exhaust port 212 for exhausting gas may be provided at a position that does not affect the supply of mist to the substrate 210. In addition, the substrate 210 may be placed on the top surface of the film forming chamber 207 to face downward, or on the bottom surface of the film forming chamber 207 to face upward.

[0116] The substrate placement unit or the nozzle may be connected to a conveying mechanism so as to be able to move in a reciprocating motion or a rotational motion, etc. By performing such a moving operation during film formation, the uniformity of the obtained film is further improved.

[0117] The material of the nozzle 250 is preferably a material with high heat resistance and mechanical strength. Specifically, metals or ceramics can be cited. More specifically, iron, aluminum, titanium, magnesium, nickel, copper, and alloys of these metals, silicon oxide, aluminum oxide, zirconium oxide, titanium oxide, silicon carbide, silicon nitride, and solid solutions of these substances are suitable. In addition, since the temperature inside the nozzle 250 is lower than that of the outer surface, from the perspective of corrosion resistance, a resin or ceramic lining or coating can also be applied to at least a portion of the inside of the nozzle 250. Specifically, any one of polyethylene, polypropylene, vinyl chloride, polystyrene, polyvinyl acetate, urethane resin, fluororesin, acrylonitrile butadiene styrene resin, acrylic resin, polyamide, polyimide, polyamideimide, nylon, acetal resin, polycarbonate, polyphenylene ether, polyester, polyethylene terephthalate, polybutylene terephthalate, polyolefin, polyphenylene sulfide, polysulfone, polyethersulfone, polyarylate, polyetheretherketone, acrylic rubber, isoprene rubber, urethane rubber, ethylene propylene rubber, ethylene vinyl acetate rubber, chloroprene rubber, styrene rubber, nitrile rubber, fluororubber, butadiene rubber, butyl rubber, aluminum oxide, aluminum nitride, silicon oxide, silicon nitride and silicon carbide can be suitably used.

[0118] In addition, the shape of the nozzle is not limited to Figure 1 , Figure 2 The rectangular parallelepiped shown may also be a cylindrical or conical shape, or a combination of these two shapes. As described above, the shape of the nozzle is not limited as long as it includes two or more opposing air inlets, a gas mixing portion having the air inlets, and an air outlet for ejecting the mist.

[0119] (Film Forming Method)

[0120] The atomization CVD method is composed of the following steps: a mist generating step of atomizing a raw material solution containing gallium in an atomizing section to generate mist; a carrier gas supplying step of supplying a carrier gas for transporting the mist to the atomizing section; a transporting step of transporting the mist from the atomizing section to the film forming chamber by the carrier gas via a supply pipe connecting the atomizing section and the film forming chamber; and a film forming step of heat-treating the transported mist to form a film on a base substrate.

[0121] The raw material solution 204a manufactured in the above manner is stored in the mist generation source 204, the substrate 210 is placed in the film forming chamber 207, and the heater 208 is turned on. Next, the flow regulating valves 203a and 203b are opened, and the carrier gas is supplied from the carrier gas sources 202a and 202b to the film forming chamber 207. After the atmosphere of the film forming chamber 207 is fully replaced with the carrier gas, the flow rate of the carrier gas and the flow rate of the dilution carrier gas are adjusted respectively.

[0122] Next, as a mist generation step, the ultrasonic vibrator 206 is vibrated, and the vibration is propagated to the raw material solution 204a through the water 205a, thereby atomizing the raw material solution 204a to generate mist.

[0123] Next, as a carrier gas supplying step, a carrier gas for conveying the mist is supplied to the atomizing unit 220 .

[0124] Next, as a transport step, the mist is transported from the atomizing section 220 to the nozzle in the film forming chamber 207 by a carrier gas through the supply pipe 209 connecting the atomizing section 220 and the film forming chamber 207 .

[0125] Next, as a film forming step, the mist transported to the nozzle is sprayed onto the substrate and heated to induce a thermal reaction, thereby forming a film on the surface of the substrate 210. In the present invention, the volume of the gas mixing unit 500 in the nozzle is set to V (cm 3 ), the linear velocity L (cm / sec) of the mist at any one of the air inlets 502 is L≥0.8V-200. By making the air inlets 502 relative to each other and making the mist have a larger linear velocity, the mist can be evenly dispersed in the nozzle 250. As a result, the density of the mist ejected from the nozzle also becomes uniform, and the obtained film thickness also becomes uniform. There is no particular restriction on the upper limit of the linear velocity L, for example, it can be set to 3,000 cm / sec or less. In addition, the volume V (cm 3 ) Preferably V>250. This allows the mist to be further evenly dispersed in the nozzle, and the obtained film thickness also becomes uniform. If V becomes too large, the required linear velocity will also increase, so it is necessary to reduce the inner diameter of the pipe. If V is too small, the mist will collide with the orifice or the inner wall of the pipe and disappear, resulting in a decrease in the film forming speed. Therefore, V is preferably 2000 or less.

[0126] In addition, the cross-sectional area of ​​the pipe at the narrowest inner diameter of the pipe is denoted as S (cm 2 ), and when the gas flow rate flowing there is set to Q (L / min), the linear velocity L can be obtained by L=Q / S×1000 / 60. The gas flow rate Q can be set to a value under standard conditions (0°C, 1 atmosphere). When there are two air inlets 502 and the piping shapes of the two are roughly the same, the gas flow rate Q of one air inlet 502 is estimated to be 1 / 2 of the total carrier gas flow rate. Even if the piping shapes are different, the flow rate of each inlet can be estimated by calculating the pressure loss using conventional methods, and the estimated value obtained can be used as the total carrier gas flow rate flowing through the piping.

[0127] The substrate or the nozzle can be moved by reciprocating motion, rotational motion, etc. during film formation by connecting to a transport mechanism, etc. By performing such a movement operation, the uniformity of the obtained film is further improved.

[0128] For the thermal reaction of the mist, it is necessary to promote the reaction of gallium and the like contained in the mist by heating, but unlike other CVD methods, the atomized CVD method requires the raw materials to reach the substrate surface in the state of misty liquid. Therefore, the temperature of the substrate surface will drop significantly. Therefore, the temperature of the substrate surface during the reaction will be different from the set temperature of the device. It is preferred to measure and control the temperature of the substrate surface during the reaction, but in the case where it is difficult to achieve this, as an alternative, the temperature can be measured by simulating the reaction by only introducing a carrier gas or introducing a water mist without solutes.

[0129] In addition, the thermal reaction also depends on the ambient temperature around the substrate. Therefore, it is desirable that the temperature of the nozzle or the inner wall of the film forming chamber is higher than the room temperature. This is to stabilize the thermal reaction. For example, the nozzle temperature can be set to 50~250℃.

[0130] In addition, the thermal reaction can be carried out in any of the following atmospheres: vacuum, oxygen-free atmosphere, reducing gas atmosphere, air atmosphere, and oxygen atmosphere, and can be appropriately set according to the film-forming material. In addition, the reaction pressure can be carried out under any of the following conditions: atmospheric pressure, pressurized, or reduced pressure. If the film is formed under atmospheric pressure, the device configuration can be simplified, so it is preferred.

[0131] (Formation of buffer layer)

[0132] As described above, a buffer layer can be appropriately provided between the substrate and the crystalline oxide film. The method for forming the buffer layer is not particularly limited, and the film can be formed by a known method such as a sputtering method and a vapor deposition method, but when using the above-mentioned atomized CVD method, it can be formed by only appropriately changing the raw material solution, which is relatively simple. Specifically, a solution in which one or more metals selected from aluminum, gallium, chromium, iron, indium, rhodium, vanadium, titanium and iridium are dissolved or dispersed in water in the form of a complex or salt can be suitably used as a raw material aqueous solution. As the form of the complex, for example, acetylacetone complexes, carbonyl complexes, ammonia complexes, hydride complexes, etc. can be listed. As the form of the salt, for example, metal chloride salts, metal bromide salts, metal iodide salts, etc. can be listed. In addition, a solution in which the above-mentioned metals are dissolved in hydrobromic acid, hydrochloric acid, hydroiodic acid, etc. can also be used as an aqueous solution of the salt. At this time, the solute concentration is also preferably 0.005~1mol / L, and the dissolution temperature is preferably set to above 20°C. The buffer layer can be formed by setting the other conditions to the same conditions as described above. After the buffer layer is formed into a film having a predetermined thickness, the crystalline oxide film is formed by the above-described method.

[0133] As a special case of the buffer layer formation method, the same material as the crystalline oxide film is sometimes used. In this case, the film forming temperature of the buffer layer can be set higher than the film forming temperature of the crystalline oxide film. For example, the film forming temperature of the buffer layer can be set to 450°C and the film forming temperature of the crystalline oxide film can be set to 400°C, or the buffer layer can be set to 500°C and the crystalline oxide film can be set to 450°C. As a result, the crystallinity of the crystalline oxide film is further improved.

[0134] (Heat Treatment)

[0135] In addition, the laminated structure of the present invention can be heat treated at 200 to 600° C. Thus, unreacted substances in the film are further removed, and a laminated structure with higher quality can be obtained. The heat treatment can be carried out in air or oxygen atmosphere, or in an inert gas atmosphere such as nitrogen or argon. The heat treatment time can be appropriately determined, for example, it can be set to 5 to 240 minutes.

[0136] (peel off)

[0137] For the stacked structure of the present invention, the crystalline oxide film can be peeled off from the base substrate. The peeling method is not particularly limited and can be a known method. As a method of peeling, for example, a method of applying physical impact to peel, a method of applying heat to peel using thermal stress, a method of applying vibration such as ultrasonic waves to peel, a method of performing etching to peel, etc. can be listed. By the above peeling, a crystalline oxide film as a self-supporting film can be obtained.

[0138] Example

[0139] Hereinafter, the present invention will be specifically described using Examples and Comparative Examples, but the present invention is not limited thereto.

[0140] [Example 1] V = 290, with orifice

[0141] In this embodiment, the Figure 4 The film forming apparatus 201 is shown. The film forming apparatus 201 includes: a carrier gas source 202a for supplying a carrier gas, a flow rate regulating valve 203a for regulating the flow rate of the carrier gas sent from the carrier gas source 202a, a dilution carrier gas source 202b for supplying a dilution carrier gas, a flow rate regulating valve 203b for regulating the flow rate of the dilution carrier gas sent from the dilution carrier gas source 202b, a mist generating source 204 for storing a raw material solution 204a, a container 205 for storing water 205a, an ultrasonic vibrator 206 installed on the bottom surface of the container 205, a film forming chamber 207 equipped with a heater 208, and a quartz supply pipe 209 connecting the mist generating source 204 to the film forming chamber 207.

[0142] The film forming chamber 207 has a nozzle 250 opposite to the gas inlet, and the supply pipe 209 is connected to the nozzle through a pipe with an inner diameter of 20 mm. An orifice with an opening diameter of 7 mm is set in the pipe 2 cm away from the gas inlet. The volume of the gas mixing section 500 in the nozzle is 290 cm 3 , 0.8V-200 is 32cm / second.

[0143] (Film Formation of Gallium Oxide Film)

[0144] Next, a gallium oxide film is formed. A 4-inch (100 mm) c-plane sapphire substrate is prepared as substrate 210. The substrate is placed in film forming chamber 207, and heater 208 is set to 450°C and heated. The chamber is left for 30 minutes to stabilize the temperature in the film forming chamber including the nozzle.

[0145] As the raw material solution 204a, ultrapure water is used as a solvent and gallium bromide is used as a solute. The gallium concentration in the raw material solution is set to 0.1 mol / L. The raw material solution 204a is stored in the mist generating source 204. Next, the flow regulating valves 203a and 203b are opened, and the carrier gas is supplied from the carrier gas sources 202a and 202b to the film forming chamber 207. After the atmosphere of the film forming chamber 207 is fully replaced with the carrier gas, the flow rate of the carrier gas is adjusted to 4 L / min, and the flow rate of the dilution carrier gas is adjusted to 6 L / min. Therefore, the total carrier gas flow rate is 10 L / min, and the linear velocity when passing through the orifice is 217 cm / sec. Nitrogen is used as the carrier gas.

[0146] Next, the ultrasonic vibrator 206 is vibrated at 2.4 MHz, and the vibration is transmitted to the raw material solution 204a through the water 205a, thereby atomizing the raw material solution 204a to generate mist. The mist is introduced into the film forming chamber 207 through the supply pipe 209 by a carrier gas, and the mist is thermally reacted on the substrate 210, thereby forming a thin film of gallium oxide on the substrate 210. The film forming time is set to 30 minutes.

[0147] (evaluate)

[0148] For the thin film formed on the substrate 210, it was confirmed by X-ray diffraction that α-Ga2O3 had been formed. The rocking curve of the (006) plane of α-Ga2O3 was measured, and the half-value width was 6 seconds, indicating excellent crystallinity. In addition, when measuring the rocking curve, a four-crystal monochromator composed of two grooved crystals was used to improve the monochromaticity of the X-rays and perform measurements with higher accuracy. Next, the film thickness was measured at 25 points using a spectral reflectance film thickness meter F50 from Filmetrics, INC., and the average film thickness was 583nm. In addition, the film thickness deviation obtained by ((maximum film thickness - minimum film thickness) / (maximum film thickness + minimum film thickness))×100(%) was good, at 3.8%.

[0149] [Comparative Example 1] V = 290, no orifice

[0150] Except that no orifice was provided in the pipe in Example 1, film formation and evaluation were performed under the same conditions and methods as in Example 1. The linear velocity at the nozzle inlet was 27 cm / sec. As a result, the average film thickness was 611 nm, and the film thickness deviation deteriorated to 13.6%.

[0151] [Example 2] V = 380, with orifice

[0152] In addition to the use of the nozzle in Example 1, the volume of the gas mixing section is 380 cm 3 Except for the nozzle, the film formation and evaluation were carried out under the same conditions and methods as in Example 1. As in Example 1, the linear velocity when passing through the orifice was 217 cm / sec. 0.8V-200 was 104 cm / sec. As a result, the average film thickness was 574 nm, and the film thickness deviation was good at 2.9%.

[0153] [Example 3] V=700, with orifice

[0154] In Example 1, the volume of the nozzle space used was 700 cm 3 The nozzle was set to 11 L / min for carrier gas flow rate and 7 L / min for dilution carrier gas flow rate. Film formation and evaluation were performed under the same conditions and methods as in Example 1. The linear velocity at the nozzle inlet was 390 cm / sec, and 0.8V-200 was 360 cm / sec. As a result, the average film thickness was 1134 nm, and the film thickness deviation was good at 3.2%.

[0155] [Comparative Example 2] V = 700, no orifice

[0156] Except that no orifice was provided in the pipe in Example 3, film formation and evaluation were performed under the same conditions and methods as in Example 3. The linear velocity at the nozzle inlet was 48 cm / sec. As a result, the average film thickness was 1180 nm, and the film thickness deviation deteriorated to 12.5%.

[0157] The following protocols are included in this manual.

[0158] [1]: A film forming method, which is a film forming method for forming a crystalline oxide film by an atomization CVD method by spraying mist from a nozzle onto a heated substrate, characterized in that:

[0159] As the nozzle, a nozzle including at least two air inlets facing each other, a gas mixing section having the air inlets, and an air outlet for ejecting the mist is used.

[0160] The volume of the gas mixing unit is V (cm3 ), the linear velocity L (cm / sec) of the mist at any one of the two or more opposing air inlets is set to L≥0.8V-200.

[0161] [2]: The film forming method according to the above-mentioned [1] is characterized in that a substrate having a diameter of 100 mm to 200 mm is used as the substrate.

[0162] [3]: The film forming method according to [1] or [2] above, characterized in that the main component of the crystalline oxide film is gallium oxide.

[0163] [4]: The film forming method according to [1], [2] or [3], characterized in that a gas mixing unit having a volume V (cm 3 ) is the gas mixing section with V>250.

[0164] [5]: A film forming device comprising an atomizing section for generating mist, a film forming section for forming a crystalline oxide film, and a nozzle for supplying the mist to the film forming section,

[0165] The nozzle includes at least two or more opposing air inlets, a gas mixing portion having the air inlets, and an air outlet for ejecting the mist.

[0166] The atomizing section and the gas inlet of the gas mixing section are connected via a pipe, and the film forming apparatus further includes a portion where an inner diameter of the pipe near the gas inlet is smaller than an inner diameter of the pipe upstream thereof.

[0167] [6]: The film forming apparatus according to [5] above, characterized in that the volume of the gas mixing section is set to V (cm 3 ), V>250.

[0168] [7]: A film forming method for forming a crystalline oxide film by spraying mist from a nozzle onto a heated substrate using an atomization CVD method, characterized in that:

[0169] As the nozzle, a nozzle including at least two air inlets facing each other, a gas mixing section having the air inlets, and an air outlet for ejecting the mist is used.

[0170] The linear velocity of the mist is increased near the air inlet.

[0171] [8]: The film forming method according to [7] above, characterized in that the volume of the gas mixing section is set to V (cm 3 ), the linear velocity L (cm / sec) of the mist at any one of the two or more opposing air inlets is set to L≥0.8V-200.

[0172] [9]: The film forming method according to [8] above, characterized in that a gas mixing unit having a volume V (cm 3 ) is the gas mixing section with V>250.

[0173]

[10] : The film forming method according to [7], [8] or [9], characterized in that a substrate having a diameter of 100 mm to 200 mm is used as the substrate.

[0174]

[11] : The film forming method according to [7], [8], [9] or

[10] above, characterized in that the main component of the crystalline oxide film is set to gallium oxide.

[0175] In addition, the present invention is not limited to the above-mentioned embodiments. The above-mentioned embodiments are examples, and any technical solution having substantially the same structure and the same technical effect as the technical concept described in the claims of the present invention is included in the technical scope of the present invention.

Claims

1. A film forming method, which is a film forming method for forming a crystalline oxide film by an atomization CVD method by spraying mist from a nozzle onto a heated substrate, characterized in that: As the nozzle, a nozzle including at least two air inlets facing each other, a gas mixing section having the air inlets, and an air outlet for ejecting the mist is used. The volume of the gas mixing unit is V (cm 3 ), the linear velocity L (cm / sec) of the mist at any one of the two or more opposing air inlets is set to L≥0.8V-200.

2. The film forming method according to claim 1, characterized in that: As the substrate, a substrate having a diameter of 100 mm to 200 mm is used.

3. The film forming method according to claim 1, characterized in that: The main component of the crystalline oxide film is gallium oxide.

4. The film forming method according to claim 2, characterized in that: The main component of the crystalline oxide film is gallium oxide.

5. The film forming method according to any one of claims 1 to 4, characterized in that: As the gas mixing unit, a volume V (cm 3 ) is the gas mixing section where V>250.

6. A film forming device, characterized in that: The invention comprises an atomizing unit for generating mist, a film forming unit for forming a crystalline oxide film, and a nozzle for supplying the mist to the film forming unit. The nozzle includes at least two or more opposing air inlets, a gas mixing portion having the air inlets, and an air outlet for ejecting the mist. The atomizing section and the gas inlet of the gas mixing section are connected via a pipe, and the film forming apparatus further includes a portion where an inner diameter of the pipe near the gas inlet is smaller than an inner diameter of the pipe upstream thereof.

7. The film forming device according to claim 6, characterized in that: The volume of the gas mixing unit is V (cm 3 ), V>250.

8. A film forming method, which is a film forming method for forming a crystalline oxide film by an atomization CVD method by spraying mist from a nozzle onto a heated substrate, characterized in that: As the nozzle, a nozzle including at least two air inlets facing each other, a gas mixing section having the air inlets, and an air outlet for ejecting the mist is used. The linear velocity of the mist is increased near the air inlet.

9. The film forming method according to claim 8, characterized in that: The volume of the gas mixing unit is V (cm 3 ), the linear velocity L (cm / sec) of the mist at any one of the two or more opposing air inlets is set to L≥0.8V-200.

10. The film forming method according to claim 9, characterized in that: As the gas mixing unit, a volume V (cm 3 ) is the gas mixing section with V>250.

11. The film forming method according to any one of claims 8 to 10, characterized in that: As the substrate, a substrate having a diameter of 100 mm to 200 mm is used.

12. The film forming method according to any one of claims 8 to 10, characterized in that: The main component of the crystalline oxide film is gallium oxide.

13. The film forming method according to claim 11, characterized in that: The main component of the crystalline oxide film is gallium oxide.

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