Method for producing gallium oxide semiconductor film and film forming apparatus

Abstract

A method for producing a gallium oxide semiconductor film using an atomizing CVD method includes the following steps: a mist generation step of generating a mist by atomizing a raw material solution containing gallium in a misting section; a carrier gas supply step of supplying a carrier gas for transporting the mist to the misting section; a transport step of transporting the mist from the misting section to a film formation chamber using the carrier gas via a supply pipe connecting the misting section and the film formation chamber; a rectification step of rectifying the flow of the mist and the carrier gas supplied to the surface of a substrate in the film formation chamber so as to flow along the surface of the substrate; a film formation step of performing heat treatment on the mist that has been rectified to form a film on the substrate; and an exhaust step of exhausting exhaust gas above the substrate. Thus, a method for producing a gallium oxide semiconductor film having excellent in-plane uniformity of film thickness and film formation rate is provided.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for manufacturing a gallium oxide semiconductor film and a film forming apparatus. BACKGROUND

[0002] In the past, a high-vacuum film forming apparatus in a non-equilibrium state such as a pulsed laser deposition method (PLD), a molecular beam epitaxy method (MBE), and a sputtering method have been developed, and an oxide semiconductor that cannot be produced by a melt method or the like has been produced. In addition, a mist chemical vapor deposition method (Mist CVD) in which a mist-like raw material is atomized and crystalline growth is performed on a substrate has been developed, and gallium oxide (α-Ga2O3) having a corundum structure has been produced. α-Ga2O3 is expected to be applied to a next-generation switching element capable of achieving high withstand voltage, low loss, and high heat resistance because of its large band gap.

[0003] Regarding the mist CVD method, a tubular furnace type mist CVD apparatus is described in Patent Literature 1. A fine channel type mist CVD apparatus is described in Patent Literature 2. A linear source type mist CVD apparatus is described in Patent Literature 3. A tubular furnace type mist CVD apparatus is described in Patent Literature 4, which is different from the mist CVD apparatus described in Patent Literature 1 in terms of introducing a carrier gas into a mist generator. A mist CVD apparatus in which a substrate is provided above a mist generator and a rotary stage on which a susceptor is mounted is provided on a hot plate is described in Patent Literature 5.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Laid-Open No. H1-257337

[0007] Patent Literature 2: Japanese Patent Application Laid-Open No. 2005-307238

[0008] Patent Literature 3: Japanese Patent Application Laid-Open No. 2012-46772

[0009] Patent Literature 4: Japanese Patent No. 5397794

[0010] Patent Literature 5: Japanese Patent Application Laid-Open No. 2014-63973

[0011] Patent Literature 6: Japanese Patent Application Laid-Open No. 2020-2396 SUMMARY

[0012] (I) Technical problem to be solved

[0013] The atomized CVD method is different from other CVD methods in that it can perform film formation at a relatively low temperature and can produce a quasi-stable phase crystal structure such as the corundum structure of α-gallium oxide. However, the present inventors have found a new problem that if heating is performed in a film formation chamber in order to perform film formation under thermal reaction, the supplied mist decreases exponentially, the film formation rate decreases, and it is difficult to maintain the in-plane uniformity of the film thickness. The larger the diameter of the substrate, the more significant this problem becomes. In response to this problem, the inventions described in Patent Literature 3 and Patent Literature 5 attempt to solve the problem by scanning and rotating the substrate. However, even if these methods are used, the in-plane uniformity of the film thickness cannot be completely eliminated. In addition, there are secondary problems that the initial cost of the device increases due to the provision of a driving unit for scanning and rotation on the film formation device, and maintenance becomes complicated.

[0014] In response to this, Patent Literature 6 describes that a unit that supplies mist in opposite directions is provided on the side surface of the film formation chamber, whereby the in-plane uniformity of the film thickness can be improved by a simple device structure, and the film formation rate can be greatly improved. However, since the mist supply ports are not completely symmetrical with respect to the substrate, the film thickness distribution deviates to some extent and improvement is desired.

[0015] The present application was completed in order to solve the above problems, and aims to provide a film formation device in which the in-plane uniformity of the film thickness and the film formation rate are excellent and in which the atomized CVD method can be applied, and a method for manufacturing a gallium oxide semiconductor film in which the in-plane uniformity of the film thickness and the film formation rate are excellent.

[0016] (II) Technical solution

[0017] The present application was completed in order to achieve the above object, and provides a method for manufacturing a gallium oxide semiconductor film using the atomized CVD method, comprising the following steps: a mist generation step of generating mist by atomizing a raw material solution containing gallium in an atomization section; a carrier gas supply step of supplying a carrier gas for transporting the mist to the atomization section; a transport step of transporting the mist from the atomization section to a film formation chamber using the carrier gas via a supply pipe connecting the atomization section and the film formation chamber; a rectification step of rectifying the flow of the mist and the carrier gas supplied to the surface of a substrate in the film formation chamber so as to flow along the surface of the substrate; a film formation step of performing heat treatment on the mist that has been rectified to perform film formation on the substrate; and an exhaust step of exhausting exhaust gas above the substrate.

[0018] According to such a method for manufacturing a gallium oxide semiconductor film, the in-plane uniformity of the film thickness can be improved using a simple method, and the film formation rate can be greatly improved.

[0019] At this time, preferably, as the substrate, a substrate having an area of 100 mm 2 or a substrate having a diameter of 2 inches (50 mm) or more.

[0020] In the method for producing a gallium oxide semiconductor film according to the present application, even in the case of using a large-area substrate in which the film thickness is likely to be non-uniform, higher in-plane uniformity of the film thickness can be obtained.

[0021] Here, preferably, in the rectifying process, the flow of the mist and the carrier gas supplied to the surface of the substrate is rectified to flow from the periphery of the substrate toward the center of the substrate.

[0022] Thus, the in-plane uniformity of the film thickness can be more reliably improved with a simpler method, and the film formation speed can be greatly improved.

[0023] Further, provided is a film formation apparatus including at least: a misting section that mists a raw material solution to generate a mist; a carrier gas supply section that supplies a carrier gas that transports the mist; a supply pipe that connects the misting section and a film formation chamber and transports the mist with the carrier gas; and the film formation chamber that heat-treats the mist supplied from a supply port together with the carrier gas and performs film formation on a substrate placed on a substrate placement section, the film formation chamber having, inside, a middle plate that rectifies the flow of the mist and the carrier gas and an exhaust pipe that exhausts exhaust gas, the middle plate being disposed above the substrate placement section and between the supply port and the substrate placement section and having a constant gap from a side wall of the film formation chamber, the exhaust pipe being connected to an opening section of a surface of the middle plate that faces the substrate placement section and being disposed to extend upward from the middle plate and penetrate a wall of the film formation chamber, the flow of the mist supplied to the film formation chamber from the supply port together with the carrier gas being rectified to flow along the surface of the substrate by the middle plate, and film formation being performed on the substrate.

[0024] According to such a film formation apparatus, the in-plane uniformity of the film thickness is improved with a simple apparatus structure, and the film formation speed is excellent.

[0025] At this time, preferably, a substrate having an area of 100 mm 2 or a substrate having a diameter of 2 inches (50 mm) or more is processed.

[0026] In the film formation apparatus according to the present application, even a large-area substrate in which the film thickness is likely to be non-uniform can obtain higher in-plane uniformity of the film thickness.

[0027] At this time, preferably, the flow of the mist supplied to the film formation chamber together with the carrier gas from the supply port is rectified by the intermediate plate to flow from the outer periphery of the substrate toward the center of the substrate, and a film is formed on the substrate.

[0028] Thus, the in-plane uniformity of the film thickness can be more reliably improved with a simpler device structure, and the film formation rate is excellent.

[0029] At this time, preferably, the substrate placement portion has a substrate placement surface at a position higher than the periphery of the substrate placement portion inside the film formation chamber.

[0030] Thus, mist that has reacted outside the substrate can be suppressed from being supplied to the substrate, and a higher-quality film can be obtained.

[0031] At this time, preferably, the heating region in which the heat treatment of the mist is performed in the film formation chamber is the same size as the substrate placement portion.

[0032] Thus, the reaction of mist outside the substrate can be further suppressed, and a higher-quality film can be obtained.

[0033] (III) Advantages

[0034] As described above, according to the film formation device of the present application, the in-plane uniformity of the film thickness can be improved with a simple device structure, and the film formation rate is excellent. In addition, according to the film formation method of the present application, the in-plane uniformity of the film thickness can be improved with a simple method, and the film formation rate can be greatly improved. In particular, when a large-area substrate in which the film thickness is likely to be non-uniform is formed into a film, a higher in-plane uniformity of the film thickness can be obtained at a higher film formation rate. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a schematic configuration view of a film formation device of the present application.

[0036] Figure 2 is a view illustrating an example of a misting portion of the film formation device of the present application.

[0037] Figure 3 is a cross-sectional schematic view of an example of a film formation chamber of the film formation device of the present application. DETAILED DESCRIPTION

[0038] The present application is described in detail below, but the present application is not limited thereto.

[0039] As described above, a film formation device in which the in-plane uniformity of the film thickness and the film formation rate are excellent, and a method of manufacturing a gallium oxide semiconductor film in which the in-plane uniformity of the film thickness and the film formation rate are excellent are being sought in the mist CVD method.

[0040] As a result of repeated and careful studies on the above technical problems, the present inventors have found that a manufacturing method of a gallium oxide semiconductor film, which uses an atomization CVD method and includes the following steps: a mist generation step of generating a mist by atomizing a raw material solution containing gallium in an atomization section; a carrier gas supply step of supplying a carrier gas for transporting the mist to the atomization section; a transport step of transporting the mist from the atomization section to a film formation chamber using the carrier gas via a supply pipe connecting the atomization section and the film formation chamber; a rectification step of rectifying the flow of the mist and the carrier gas supplied to the surface of a substrate in the film formation chamber so as to flow along the surface of the substrate; a film formation step of performing heat treatment on the mist that has been rectified to form a film on the substrate; and an exhaust step of exhausting exhaust gas above the substrate, can improve the in-plane uniformity of film thickness in a simple method and has excellent film formation speed, thereby completing the present invention.

[0041] In addition, it has been found that a film formation apparatus, which has at least an atomization section that atomizes a raw material solution to generate a mist, a carrier gas supply section that supplies a carrier gas for transporting the mist, a supply pipe that connects the atomization section and a film formation chamber and transports the mist using the carrier gas, and a film formation chamber that performs heat treatment on the mist supplied from a supply port together with the carrier gas and forms a film on a substrate placed on a substrate placement section, has a middle plate that rectifies the flow of the mist and the carrier gas inside the film formation chamber, and an exhaust pipe that exhausts exhaust gas, the middle plate is provided above the substrate placement section and between the supply port and the substrate placement section and has a constant gap from the side wall of the film formation chamber, the exhaust pipe is connected to an opening portion of the middle plate that faces the substrate placement section and is provided to extend upward from the middle plate and penetrate the wall of the film formation chamber, and the flow of the mist supplied from the supply port together with the carrier gas to the film formation chamber is rectified to flow along the surface of the substrate using the middle plate, thereby forming a film on the substrate, can improve the in-plane uniformity of film thickness in a simple apparatus structure and has excellent film formation speed, thereby completing the present invention.

[0042] Further, as a result of intensive studies by the present inventors on the above technical problems, it has been found that a manufacturing method of a gallium oxide semiconductor film using an atomization CVD method, which includes the following steps: a mist generation step of generating a mist by atomizing a raw material solution containing gallium in a misting section; a carrier gas supply step of supplying a carrier gas for transporting the mist to the misting section; a transport step of transporting the mist from the misting section to a film formation chamber using the carrier gas via a supply pipe connecting the misting section and the film formation chamber; a rectification step of rectifying the flow of the mist and the carrier gas supplied to the surface of a substrate in the film formation chamber so as to flow from the periphery of the substrate toward the center of the substrate; a film formation step of performing heat treatment on the mist that has been rectified to perform film formation on the substrate; and an exhaust step of exhausting exhaust gas above the substrate, can improve the in-plane uniformity of film thickness in a simple manner and has excellent film formation speed, and the present invention has been completed.

[0043] Further, it has been found that a film formation apparatus, which has at least a misting section that atomizes a raw material solution to generate a mist, a carrier gas supply section that supplies a carrier gas for transporting the mist, a supply pipe that connects the misting section and a film formation chamber and transports the mist using the carrier gas, and a film formation chamber that performs heat treatment on the mist supplied from a supply port together with the carrier gas and performs film formation on a substrate placed on a substrate placement section, has a middle plate that rectifies the flow of the mist and the carrier gas inside, and an exhaust pipe that exhausts exhaust gas, the middle plate is provided above the substrate placement section and between the supply port and the substrate placement section and has a constant gap from the side wall of the film formation chamber, and the exhaust pipe is connected to an opening portion of the middle plate that faces the substrate placement section and is provided so as to extend upward from the middle plate and penetrate the wall of the film formation chamber, the flow of the mist supplied from the supply port together with the carrier gas to the film formation chamber is rectified by the middle plate so as to flow from the periphery of the substrate toward the center of the substrate, and film formation is performed on the substrate, can improve the in-plane uniformity of film thickness in a simple apparatus structure and has excellent film formation speed, and the present invention has been completed.

[0044] Here, the mist in the present invention refers to the general term for liquid particles dispersed in a gas and also includes cases referred to as mist, droplets, and the like.

[0045] The following description is given with reference to the drawings.

[0046] <First Embodiment>

[0047] (Film formation apparatus)

[0048] Figure 1An example of a film formation apparatus 101 according to the present application is shown in FIG. 1. The film formation apparatus 101 has at least an atomizing section 120 that atomizes a raw material solution 104a to generate mist, a carrier gas supply section 130 that supplies a carrier gas that transports the mist, a supply pipe 109 that connects the atomizing section 120 and a film formation chamber 300 and transports the mist using the carrier gas, and the film formation chamber 300 that performs heat treatment on the mist supplied from a supply port 301 together with the carrier gas to perform film formation on a substrate 310 placed on a substrate placement section 313.

[0049] (Atomizing section)

[0050] In the atomizing section 120, the raw material solution 104a is atomized to generate mist. The atomizing unit is not particularly limited as long as it can atomize the raw material solution 104a and can be a publicly known atomizing unit. It is preferable to use an atomizing unit based on ultrasonic vibration because it can atomize more stably.

[0051] An example of such an atomizing section 120 is described with reference to Figure 2 For example, the atomizing section 120 can include a mist generation source 104 that houses the raw material solution 104a, a container 105 that contains a medium such as water 105a that can transmit ultrasonic vibration, and an ultrasonic vibrator 106 that is installed on the bottom surface of the container 105. In detail, the mist generation source 104 that is constituted by the container that houses the raw material solution 104a can be housed in the container 105 that houses the water 105a using a support body (not shown). The ultrasonic vibrator 106 can be installed on the bottom of the container 105 and can be connected to an oscillator 116. Furthermore, it can be configured such that the ultrasonic vibrator 106 vibrates if the oscillator 116 is operated, the ultrasonic wave is propagated to the mist generation source 104 via the water 105a, and the raw material solution 104a is atomized.

[0052] (Raw material solution)

[0053] The material included in the raw material solution 104a is not particularly limited as long as it contains at least gallium and can be atomized and can be an inorganic material or an organic material. In addition, a metal or a metal compound can be mixed in addition to gallium, and for example, a raw material solution that contains a metal selected from one or two or more of iron, indium, aluminum, vanadium, titanium, chromium, rhodium, nickel, and cobalt can be used.

[0054] There are no particular limitations on the raw material solution as long as it can atomize the aforementioned metals. The raw material solution can be appropriately obtained by dissolving or dispersing the metal in an organic solvent or water as a complex or salt. Examples of complexes include acetylacetone complexes, hydroxyl complexes, ammonia complexes, and hydrogenated complexes. Examples of salts include metal chloride salts, metal bromide salts, and metal iodide salts. Furthermore, solutions formed by dissolving the aforementioned metals in hydrobromic acid, hydrochloric acid, hydroiodic acid, etc., can also be used as aqueous solutions of salts.

[0055] Alternatively, additives such as hydrohalic acids and oxidizing agents can be mixed into the raw material solution. Examples of hydrohalic acids include hydrobromic acid, hydrochloric acid, and hydroiodic acid, with hydrobromic acid or hydroiodic acid being preferred. Examples of oxidizing agents include peroxides such as hydrogen peroxide (H2O2), sodium peroxide (Na2O2), barium peroxide (BaO2), and benzoyl peroxide (C6H5CO)2O2, as well as organic peroxides such as hypochlorous acid (HClO), perchloric acid, nitric acid, ozone water, peracetic acid, and nitrobenzene.

[0056] Furthermore, dopants can also be included in the raw material solution. There are no particular limitations on the dopants. Examples include n-type dopants such as tin, germanium, silicon, titanium, zirconium, vanadium, or niobium, and p-type dopants such as copper, silver, tin, iridium, and rhodium. The concentration of the dopant can be, for example, approximately 1 × cm⁻¹. 3 / cm 3 ~1×10 22 / cm 3 It can be approximately 1×10 17 / cm 3 The following low concentrations can also be approximately 1×10⁻⁶. 20 / cm 3 The above are high concentrations.

[0057] (Carrier Gas Supply Department)

[0058] like Figure 1 As shown, the carrier gas supply unit 130 includes a carrier gas source 102a for supplying carrier gas. A flow regulating valve 103a may also be included to regulate the flow rate of the carrier gas supplied from the carrier gas source 102a. Additionally, a dilution carrier gas source 102b for supplying dilution carrier gas and a flow regulating valve 103b for regulating the flow rate of the dilution carrier gas supplied from the dilution carrier gas source 102b may also be included, if necessary.

[0059] The kind of the carrier gas is not particularly limited and can be appropriately selected depending on the film-forming material. For example, inert gases such as oxygen, ozone, nitrogen, argon, or the like, or reducing gases such as hydrogen, synthetic gas, or the like can be given. In addition, the kind of the carrier gas can be one or two or more. For example, a diluted gas in which the same gas as the first carrier gas is diluted by a gas other than the same gas (for example, diluted by 10 times) or the like can be used as the second carrier gas, and air can also be used. The flow rate of the carrier gas is not particularly limited. For example, when film formation is performed on a substrate of 30 mm square, the flow rate of the carrier gas is preferably 0.01 to 20 L / min, and more preferably 1 to 10 L / min.

[0060] (Supply pipe)

[0061] The film-forming apparatus 101 has a supply pipe 109 that connects the atomization section 120 and the film-forming chamber 300. In this case, the mist generated from the mist generation source 104 of the atomization section 120 is transported using the carrier gas via the supply pipe 109 and is supplied into the film-forming chamber 300. The supply pipe 109 can be formed of, for example, a quartz pipe, a resin pipe, or the like.

[0062] (Film-forming chamber)

[0063] Figure 3 is a cross-sectional view schematically showing an example of the film-forming chamber 300 of the film-forming apparatus of the present application (the same as the film-forming chamber 300 of Figure 1 ). The film-forming chamber 300 is substantially closed and has at least one or more mist inlets, i.e., supply ports 301, an exhaust pipe 312 that exhausts exhaust gas to the upper side of a substrate 310, and a middle plate 321 that regulates the flow of the mist and the carrier gas. The supply ports 301 are connected to the supply pipe 109 and supply the mist into the film-forming chamber 300.

[0064] By adjusting the position of the opening of the supply port 301 using a position adjusting mechanism, the position of the mist and the carrier gas that is ejected can be changed by changing the position of the front end of the supply port 301 in the film-forming chamber 300 in accordance with the film-forming conditions.

[0065] (Middle plate)

[0066] Figure 3The film formation chamber 300 shown has a middle plate 321 inside above the substrate mounting portion 313 and between the supply port 301 and the substrate mounting portion 313. Further, a constant gap 322 is formed between the outer periphery of the middle plate 321 and the side wall of the inside of the film formation chamber 300. By providing such a middle plate 321 inside the film formation chamber 300, the flow of the mist supplied from the supply port 301 together with the carrier gas is rectified so that the mist supplied from the supply port 301 passes through the gap 322 between the side wall of the film formation chamber 300 and the middle plate 321 and further passes through the gap 323 between the substrate 310 and the middle plate 321. That is, the mist is rectified so as to flow from the outer periphery of the substrate 310 toward the center of the substrate 310, and the uniformity of the flow rate and direction of the mist is achieved. The size of the middle plate 321 is preferably such that it covers the substrate 310 (substrate mounting portion 313) entirely. Thus, in addition to improving the utilization efficiency of the mist, the uniformity of the flow rate and direction of the mist is achieved. The shape of the middle plate 321 is preferably circular, but is not particularly limited. The material of the middle plate 321 is not particularly limited, and is preferably a material that does not react with the mist.

[0067] The gap 322 between the outer periphery of the middle plate 321 and the side wall of the inside of the film formation chamber 300 is preferably 0.1 to 10 mm. If the gap 322 is in this range, the uneven flow of the gas containing the mist and the deviation generated in the gap can be effectively suppressed, and the flow of the mist on the substrate 310 can be made more uniform. The gap 322 can be changed in correspondence with the film formation conditions. For example, in the case where the middle plate 321 is circular, by preparing two or more plates having different diameters and mounting them by replacement, the gap 322 can be arbitrarily changed. The gap 323 between the middle plate 321 and the substrate 310 is preferably 0.5 to 10 mm. If the gap 323 is in this range, the flow of the gas containing the mist can be made more stable, and in addition, the utilization efficiency of the mist can be maintained in a higher state. The gap 323 can be changed in correspondence with the film formation conditions. For example, by providing a height adjustment mechanism for the middle plate 321 in advance, the gap 323 can be arbitrarily changed.

[0068] (Exhaust pipe)

[0069] Further, the exhaust pipe 312 is connected to the opening portion of the surface of the middle plate 321 opposite to the substrate mounting portion 313, and is provided so as to extend upward from the middle plate 321 and penetrate the wall of the film formation chamber 300, for example, the top plate. The position of the opening portion of the exhaust pipe 312 is not particularly limited, but in order to exhaust the unused exhaust gas in the gas flowing from the outer periphery of the substrate 310 toward the center during film formation, it is preferably arranged so that the center of the middle plate 321, the center of the opening portion, and the center of the substrate mounting portion 313 coincide. The diameter of the opening portion of the portion of the middle plate 321 connected to the exhaust pipe 312 can be appropriately set, and can be 1 to 15 mm.

[0070] By making the film forming chamber 300 the above structure, the mist is rectified by the middle plate 321, and can flow uniformly at the same flow rate from the outer periphery of the substrate 310 toward the center. Also, since the volume flow per unit area increases as it gets closer to the center of the substrate 310, there is an effect of suppressing the consumption of mist due to film formation in appearance. Due to these effects, it is possible to make the film thickness deviation extremely small at a higher film formation speed.

[0071] (Substrate mounting portion)

[0072] The substrate 310 is mounted on the substrate mounting surface 314 of the substrate mounting portion 313 in the film forming chamber 300. Here, the substrate mounting portion 313 refers to the portion of the member that supports the substrate 310, which opposes the lower surface of the substrate 310 when the substrate 310 is placed on the member that supports the substrate 310. Also, the substrate mounting surface 314 refers to the surface that supports the substrate 310. It is possible to provide a heating unit that heats the substrate 310 and performs heat treatment of the mist below the substrate 310. The heating unit is not particularly limited, and for example, can be a hot plate 308. The hot plate 308 can be provided inside the film forming chamber 300 as shown in FIG. 1, or can be provided outside the film forming chamber 300. Also, the hot plate 308 can constitute the entire bottom surface of the film forming chamber 300, can be slightly larger than the substrate 310, or can be the same size as the substrate 310. Due to this, it is possible to suppress the reaction of the mist outside the substrate 310, and it is possible to obtain a higher quality film. Also, it is preferable that the heating region be approximately the same size as the substrate mounting portion 313, and more preferably, the same size. Figure 3

[0073] It is also possible to provide a cooling unit on the substrate mounting portion 313. By cooling at the same time as heating, it is possible to prevent local temperature increases and overshoots of the temperature increase, and it is possible to perform temperature adjustment with higher precision. The cooling unit is not particularly limited, and for example, a Peltier element can be used, or a method in which a coolant is circulated can be used.

[0074] It is possible to provide a rotation mechanism for rotating the substrate 310 during film formation on the substrate mounting portion 313, and due to this, it is possible to further reduce the film thickness deviation.

[0075] It is possible to provide a mechanism for adsorbing the substrate 310 on the substrate mounting portion 313. By adsorbing the substrate, it is possible to improve the heat transfer efficiency and uniformity, and it is possible to perform temperature increases / decreases in a shorter time, and also, it is possible to make the temperature distribution of the substrate more uniform. Also, it is possible to prevent the substrate from slipping or detaching in the case where the aforementioned rotation mechanism is used. The adsorption unit is not particularly limited, and for example, adsorption using static electricity or adsorption using a vacuum can be used.

[0076] ​Further, it is also preferable to make the heating region a block of metal having good heat conductivity provided under the substrate 310, a convex shape formed on the hot plate 308, and make the height of the substrate placement surface 314 be higher than the periphery of the substrate placement portion 313, and can be located at a position of about 1 to 50 mm higher than the periphery. In this way, mist that has reacted outside the substrate 310 can be suppressed from being supplied to the substrate 310, and thus a film of higher quality can be obtained.

[0077] (Substrate)

[0078] The substrate 310 is not particularly limited as long as it can form a film and can support the film. The material of the substrate 310 is also not particularly limited, and a publicly known substrate can be used, and can be an organic compound or an inorganic compound. For example, organic compounds such as polysulfone, polyethersulfone, polyphenylene sulfide, polyether ether ketone, polyimide, polyetherimide, and fluororesin, metals such as iron, aluminum, stainless steel, and gold, and inorganic compounds such as silicon, sapphire, quartz, glass, lithium tantalate, potassium tantalate, and gallium oxide can be given, but are not limited thereto. The thickness of the substrate is not particularly limited, and is preferably 10 to 2000 μm, and more preferably 50 to 800 μm.

[0079] The size of the substrate 310 is not particularly limited, and in a general method, the larger the area, the more likely the film thickness is to be uneven, and the effect of the present application is significant. Thus, the present application preferably uses a substrate having an area of 100 mm 2 The above or a substrate having a diameter of 2 inches (50 mm) or more can also use a substrate having a diameter of 2 to 8 inches (50 to 200 mm) or more. Since the larger the area, the more significant the effect of the present application as described above, it is preferable, and thus the upper limit of the area or diameter of the substrate is not specified.

[0080] (Method for manufacturing gallium oxide semiconductor film)

[0081] Next, the method for manufacturing a gallium oxide semiconductor film according to the present application will be described with reference to the drawings. Figure 1 The method for manufacturing a gallium oxide semiconductor film according to the present application will be described.

[0082] First, the raw material solution 104a containing gallium is housed in the mist generation source 104, the substrate 310 is placed on the hot plate 308 directly or via the wall of the film formation chamber 300, and the hot plate 308 is operated. Next, the flow rate adjustment valves 103a and 103b are opened to supply the carrier gas from the carrier gas sources 102a and 102b into the film formation chamber 300, and when the atmosphere of the film formation chamber 300 is sufficiently replaced with the carrier gas, the flow rate of the carrier gas and the flow rate of the dilution carrier gas are adjusted.

[0083] Next, as a mist generation step, the ultrasonic vibrator 106 is vibrated, and the vibration is propagated to the raw material solution 104a through the water 105a, and thus the raw material solution 104a is atomized to generate mist.

[0084] Next, as a carrier gas supply step, a carrier gas for transporting the mist is supplied to the atomizing section 120.

[0085] Next, as a transport step, the mist is transported from the atomizing section 120 to the film forming chamber 300 by the carrier gas via the supply pipe 109 connecting the atomizing section 120 and the film forming chamber 300. The mist is supplied from above the middle plate 321, and can be supplied from multiple directions instead of one direction.

[0086] Next, as a rectification step, the flow of the mist and the carrier gas supplied to the surface of the substrate 310 in the film forming chamber 300 is rectified so as to become a flow from the periphery of the substrate 310 toward the center of the substrate 310. The mist is rectified by the middle plate 321 in the film forming chamber 300, and a uniform flow is formed in parallel with the surface of the substrate 310.

[0087] Next, as a film forming step, the mist that has been rectified is heat treated to form a film on the substrate 310. The mist is heat reacted by the heat of the hot plate 308 in the film forming chamber 300, and a film is formed on the substrate 310.

[0088] In the film forming chamber 300, the mist is heated to cause a heat reaction, and a film is formed on the substrate 310. As for the heat reaction, it is sufficient that the mist is caused to react by heating, and the reaction conditions and the like are not particularly limited. They can be appropriately set according to the raw material and the film to be formed. For example, the heating temperature is in the range of 120 to 600°C, preferably in the range of 200 to 600°C, and more preferably in the range of 300 to 550°C.

[0089] In addition, the heat reaction can be performed under any atmosphere of vacuum, a non-oxygen atmosphere, a reducing gas atmosphere, an air atmosphere, and an oxygen atmosphere, as long as it is appropriately set according to the film to be formed. In addition, as for the reaction pressure, it can be performed under any conditions of atmospheric pressure, pressurization, or reduced pressure, and if it is formed under atmospheric pressure, the device structure can be simplified, and thus it is preferable.

[0090] Here, as an exhaust step, exhaust gas is exhausted to the upper side of the substrate 310. The gas in the film forming chamber 300 can be exhausted to the outside of the film forming chamber 300 from the exhaust pipe 312 provided above the substrate 310.

[0091] By supplying the mist like this, the mist introduced into the film forming chamber 300 is uniformly and highly dense over a wide range on the substrate 310, and thus the in-plane distribution of the film thickness can be improved and the film forming speed can be increased.

[0092] (BUFFER LAYER)

[0093] When forming the film containing the gallium oxide described above, a buffer layer can be appropriately provided between the substrate and the film. As the material of the buffer layer, Al2O3, Ga2O3, Cr2O3, Fe2O3, In2O3, Rh2O3, V2O3, Ti2O3, Ir2O3, or the like is preferably used. The method of forming the buffer layer is not particularly limited, and the film can be formed by a publicly known method such as a sputtering method, an evaporation method, or the like, and in the case of using the atomizing CVD method described above, the buffer layer can be formed simply by appropriately changing the raw material solution of the buffer layer. Specifically, a solution in which one or two or more kinds of 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 a salt can be used as the raw material aqueous solution of the buffer layer. As the form of the complex, for example, an acetylacetone complex, a hydroxyl complex, an ammonia complex, a hydride complex, or the like can be given. As the form of the salt, for example, a metal chloride, a metal bromide, a metal iodide, or the like can be given. In addition, a solution in which the above metal is dissolved in hydrobromic acid, hydrochloric acid, hydroiodic acid, or the like can also be used as the aqueous solution of the salt. The solute concentration of the raw material solution of the buffer layer is preferably 0.01 to 1 mol / L. The other conditions can also be formed by the same as described above to form the buffer layer. After the buffer layer is formed to a prescribed thickness, the oxide semiconductor film having gallium as the main component is formed by the method described above. The thickness of the buffer layer is preferably 0.1 μm to 2 μm.

[0094] (Heat treatment)

[0095] In addition, the film obtained by the method for manufacturing a gallium oxide semiconductor film of the present application can be subjected to heat treatment at 200 to 600°C. Thereby, unreacted species or the like in the film can be removed, and a higher-quality layered structure can be obtained. The heat treatment can be performed in air, in an oxygen atmosphere, or in an inert gas atmosphere such as nitrogen or argon. The heat treatment time can be appropriately determined, and for example, can be 5 to 240 minutes.

[0096] <Second Embodiment>

[0097] In addition to the film formation apparatus and the method for manufacturing a gallium oxide semiconductor film of the first embodiment described above, the following apparatus and method can also be used.

[0098] With the second embodiment, first, the film forming apparatus is described. In the first embodiment, the flow of the mist and carrier gas from the outer periphery (outer periphery side) of the substrate 310 toward the center of the substrate 310 was rectified, and in the second embodiment, as a more general method, the mist and carrier gas were rectified so as to flow along the surface of the substrate 310. That is, the mist and carrier gas were rectified so as to flow along the surface of the substrate 310 toward the opening of the exhaust pipe 312, and even with such an apparatus, the in-plane uniformity of the film thickness and the growth rate can be improved simply compared to the conventional apparatus. The position of the opening of the exhaust pipe 312 can be close to the center of the substrate 310 or can be away from the center of the substrate 310.

[0099] In addition, by also providing a lateral position adjustment mechanism of the middle plate 321, the position of the middle plate 321 can be changed in conjunction with the movement of the supply port 301 corresponding to the film forming conditions.

[0100] In addition, with the exhaust pipe 312, by providing a position adjustment mechanism of the exhaust pipe 312, the relative position of the lower end opening of the exhaust pipe 312 and the substrate 310 can be changed corresponding to the film forming conditions. In this case, the middle plate 321 can be fixed to the exhaust pipe 312 and the position can be changed integrally, or the middle plate 321 can be provided so that the opening of the middle plate 321 through which the exhaust pipe 312 passes is larger than the size of the exhaust pipe 312, and the exhaust pipe 312 moves along the opening range of the opening.

[0101] By making the film forming chamber 300 the above structure, the mist is rectified by the middle plate 321, and can flow uniformly along the surface of the substrate 310 (particularly, in parallel with the surface of the substrate 310) at the same flow rate. Furthermore, the volume flow per unit area increases the closer it is to the opening of the exhaust pipe 312 provided, and thus has the effect of suppressing the consumption of the mist due to film formation in appearance. Due to these effects, the deviation of the film thickness can be made extremely small at a high film formation rate. By changing the opening position of the exhaust pipe 312 appropriately corresponding to the film forming conditions, the deviation of the film thickness can be made even smaller.

[0102] In particular, for example, the center of the middle plate 321, the center of the opening thereof (the position of the opening of the exhaust pipe 312), and the center of the substrate placement portion 313 can be aligned, and by such a simpler structure, the mist and carrier gas can be made to flow uniformly from the outer periphery (outer periphery side) of the substrate 310 along the surface of the substrate 310 toward the center direction thereof (toward the opening of the exhaust pipe 312 located in the center direction) at the same flow rate more reliably. Furthermore, in this case, the structure is substantially the same as the first embodiment.

[0103] Thus, it is possible to make a structure in which the relative positions of the center of the middle plate 321, the exhaust pipe 312, and the center of the substrate 310 are appropriately changed in accordance with the film formation conditions before or during film formation.

[0104] Further, the above-described lateral position adjustment mechanism of the middle plate 321 or the position adjustment mechanism of the exhaust pipe 312 itself can also be provided in the first embodiment. In the first embodiment, as repeatedly described, as a result, only the flow of the mist and the carrier gas is rectified to flow from the outer periphery (the outer periphery side) of the substrate 310 toward the center by the middle plate 321.

[0105] Further, as the method for manufacturing a gallium oxide semiconductor film according to the second embodiment, when rectifying the flow of the mist and the carrier gas supplied to the surface of the substrate 310 in the film formation chamber 300, the flow is rectified to flow along the surface of the substrate 310 (particularly, flow parallel to the surface of the substrate 310). By the middle plate 321 in the film formation chamber 300, it is possible to rectify the mist and the carrier gas as described above, and it is possible to obtain the effect of simply improving the in-plane uniformity of the film thickness and greatly improving the film formation speed.

[0106] At this time, in particular, it is possible to rectify the flow from the outer periphery (the outer periphery side) of the substrate 310 toward the center of the substrate 310. As described above, by configuring such that the center of the middle plate 321, the center of the opening portion thereof (the position of the opening portion of the exhaust pipe 312), and the center of the substrate placement portion 313 coincide, it is possible to more simply and reliably obtain the above-described effect. Further, in this case, it is a substantially same method as that of the first embodiment.

[0107] Embodiment

[0108] The present application will be specifically described below by citing an embodiment, but this does not limit the present application.

[0109] (Embodiment 1)

[0110] (Film formation apparatus)

[0111] Reference Figure 1The film formation apparatus 101 used in this example (first embodiment) will be described. The film formation apparatus 101 is provided with: a carrier gas source 102a that supplies a carrier gas; a flow rate adjustment valve 103a for adjusting the flow rate of the carrier gas sent from the carrier gas source 102a; a dilution carrier gas source 102b that supplies a dilution carrier gas; a flow rate adjustment valve 103b for adjusting the flow rate of the dilution carrier gas sent from the dilution carrier gas source 102b; a mist generation source 104 that houses a raw material solution 104a; a container 105 that houses water 105a; an ultrasonic transducer 106 that is installed to the bottom surface of the container 105; a film formation chamber 300; a quartz-made supply tube 109 that connects from the mist generation source 104 to the film formation chamber 300; and a hot plate 308 that is provided inside the film formation chamber 300. A substrate 310 is provided inside the film formation chamber 300, and is heated on the hot plate 308.

[0112] A middle plate 321 having a diameter of 120 mm is provided inside the film formation chamber 300, and an opening having a diameter of 10 mm is provided at the center and is connected to the exhaust pipe 312. The gap 322 between the middle plate 321 and the side wall of the film formation chamber 300 is set to 4 mm, and the gap 323 between the middle plate 321 and the substrate 310 is also set to 4 mm. The exhaust pipe 312 that extends from the middle plate 321 penetrates the top plate of the film formation chamber 300.

[0113] (Substrate)

[0114] A c-plane sapphire substrate having a diameter of 4 inches (100 mm) was placed as the substrate 310 on the hot plate 308 inside the film formation chamber 300, and the hot plate 308 was operated to raise the temperature to 500°C. A Cu block having a diameter of 101 mm and a height of 13 mm was placed below the substrate 310, and the substrate 310 was raised while maintaining the temperature constant.

[0115] (Raw material solution)

[0116] A 0.1 mol / L gallium bromide aqueous solution was adjusted to contain a 48% hydrobromic acid solution at a volume ratio of 10%, and this was used as the raw material solution 104a.

[0117] (Film formation)

[0118] The raw material solution 104a obtained as described above was housed in the mist generation source 104. Next, the flow rate adjustment valves 103a, 103b were opened, and the carrier gas was supplied from the carrier gas sources 102a, 102b into the film formation chamber 300, and after the atmosphere of the film formation chamber 300 was sufficiently replaced with the carrier gas, the flow rate of the carrier gas was adjusted to 10 L / minute, and the flow rate of the dilution carrier gas was adjusted to 30 L / minute.

[0119] Oxygen was used as the carrier gas.

[0120] Next, the ultrasonic vibrator 106 was vibrated at 2.4 MHz, and the vibration was propagated to the raw material solution 104a through the water 105a, thereby atomizing the raw material solution 104a to generate a mist. The mist was introduced into the film formation chamber 300 through the supply pipe 109 using a carrier gas. The mist was allowed to generate a thermal reaction in the film formation chamber 300 under atmospheric pressure at 500°C, and a thin film of gallium oxide (α-Ga2O3) having a corundum structure was formed on the substrate 310. The film formation time was 30 minutes.

[0121] For the thin film formed on the substrate 310, the measurement sites were set to 17 points in the plane of the substrate 310, and the film thickness was measured using an optical interference type film thickness meter, and the average film thickness, the film formation rate, and the standard deviation were calculated.

[0122] As a result, the average film thickness was 5.0 μm, the film formation rate was 10.0 μm / hour, and the standard deviation was 0.3 μm.

[0123] (Example 2)

[0124] Film formation and evaluation were performed under the same conditions as in Example 1 except that the flow rate of the carrier gas was 5 L / minute and the flow rate of the dilution carrier gas was 15 L / minute. As a result, the average film thickness was 2.4 μm, the film formation rate was 4.8 μm / hour, and the standard deviation was 0.1 μm.

[0125] (Example 3)

[0126] Film formation and evaluation were performed under the same conditions as in Example 1 except that the flow rate of the dilution carrier gas was 60 L / minute. As a result, the average film thickness was 4.7 μm, the film formation rate was 9.4 μm / hour, and the standard deviation was 0.2 μm.

[0127] (Comparative Example)

[0128] Film formation and evaluation were performed under the same conditions as in Example 1 except that the middle plate 321 of the film formation chamber 300 was not provided. As a result, the average film thickness was 0.7 μm, the film formation rate was 1.4 μm / hour, and the film formation was basically not possible. In addition, the standard deviation was 0.4 μm, and if the film thickness was considered to be thin, a result of a very large deviation was obtained.

[0129] As described above, by the structure of the film formation apparatus of the present application and the gallium oxide production method of the present application, even if a substrate having a large area is used, a gallium oxide film having a sufficient film thickness, an excellent film formation rate, and excellent in-plane uniformity can be formed.

[0130] Furthermore, the present application is not limited to the above-described embodiments. The above-described embodiments are examples, and any solutions having substantially the same structure as that recited in the claims of the present application and achieving the same effects are included in the technical scope of the present application.

Claims

1. A method for producing a gallium oxide semiconductor film using a mist CVD method, characterized by, The method comprises the following steps: a mist generation step of generating a mist by atomizing a raw material solution containing gallium in an atomization section; a carrier gas supply step of supplying a carrier gas for transporting the mist to the atomization section; a transport step of transporting the mist from the atomization section to a film formation chamber using the carrier gas via a supply pipe connecting the atomization section and the film formation chamber; a rectification step of rectifying the flow of the mist and the carrier gas supplied to the surface of a substrate in the film formation chamber using a middle plate provided inside the film formation chamber so as to have a gap of 0.5 to 10 mm from the substrate; a film formation step of performing heat treatment of the mist rectified in the rectification step using a heating unit provided below the substrate in the film formation chamber to perform film formation on the substrate; and an exhaust step of exhausting exhaust gas above the substrate, the relative positions of the rectification step or the exhaust step of the mist and the carrier gas and the substrate are changed during film formation.

2. The method of manufacturing a gallium oxide semiconductor film according to claim 1, wherein As the substrate, a substrate having an area of 100 mm 2 The above or a substrate having a diameter of 2 inches or more.

3. The method of manufacturing a gallium oxide semiconductor film according to claim 1 or 2, wherein in the rectification step, the flow of the mist and the carrier gas supplied to the surface of the substrate is rectified to flow from the periphery of the substrate toward the center of the substrate.

4. A film formation apparatus having at least: an atomization section that atomizes a raw material solution to generate a mist; a carrier gas supply section that supplies a carrier gas for transporting the mist; a supply pipe that connects the atomization section and a film formation chamber and transports the mist using the carrier gas; and a film formation chamber that performs heat treatment of the mist supplied from a supply port together with the carrier gas and performs film formation on a substrate placed on a substrate placement section, characterized in that a heating unit is provided below the substrate placed on the substrate placement section, and performs heat treatment of the mist by heating the substrate, the film formation chamber has inside: a middle plate that rectifies the flow of the mist and the carrier gas; and an exhaust pipe that exhausts exhaust gas, the middle plate is provided above the substrate placement section and between the supply port and the substrate placement section, has a gap from the side wall of the film formation chamber, and has a gap of 0.5 to 10 mm from the substrate, the exhaust pipe is connected to an opening portion of the middle plate opposite the substrate placement section and is provided so as to extend upward from the middle plate and penetrate the wall of the film formation chamber, the flow of the mist supplied from the supply port together with the carrier gas to the film formation chamber is rectified to flow along the surface of the substrate using the middle plate, and film formation is performed on the substrate, the relative positions of the middle plate, the lower end opening portion of the exhaust pipe, and the substrate can be changed during film formation.

5. The film formation apparatus according to claim 4, wherein A substrate having an area of 100 mm 2 The above or a substrate having a diameter of 2 inches or more is processed.

6. The film formation apparatus according to claim 4, wherein The flow of the mist supplied from the supply port together with the carrier gas to the film formation chamber is rectified by the middle plate to flow from the outer periphery of the substrate toward the center of the substrate, and film formation is performed on the substrate.

7. The film formation apparatus according to claim 5, wherein The flow of the mist supplied from the supply port together with the carrier gas to the film formation chamber is rectified by the middle plate to flow from the outer periphery of the substrate toward the center of the substrate, and film formation is performed on the substrate.

8. The film formation apparatus according to any one of claims 4 to 7, wherein In the inside of the film formation chamber, the substrate placement portion has a substrate placement surface at a position higher than the periphery of the substrate placement portion, and the middle plate is sized to cover the substrate entirely.

9. The film formation apparatus according to any one of claims 4 to 7, wherein In the film formation chamber, a heating region in which the heat treatment of the mist is performed and the substrate placement portion are the same size.

10. The film formation apparatus according to claim 8, wherein In the film formation chamber, a heating region in which the heat treatment of the mist is performed and the substrate placement portion are the same size.

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