Method for producing a product with an oxide film

Abstract

A method for producing a product (2) comprising an oxide film (6) of a second metal doped with a first metal includes generating a mist (23m) from a feed solution (23) in which the first metal and the second metal are dissolved; and supplying the mist to the surface of a substrate (4) to form an oxide film on the surface of the substrate. The pH of the feed solution is less than 7.

Description

Technical Field

[0001] The technology disclosed herein relates to a method for producing products having oxide films. The products described herein include not only end products with specific uses and functions, but also semi-finished products temporarily manufactured during the manufacturing process of the end products.

[0002] WO 2018 / 004008 discloses a method for manufacturing a semiconductor device. This method includes the steps of preparing one or more raw material solutions, generating a mist from each of the one or more raw material solutions, and supplying the mist to the surface of a substrate. A metal as a dopant is dissolved in the raw material solution, and the mist of the raw material solution is supplied to the surface of the substrate, such that an oxide film of the doped metal is deposited on the surface of the substrate. This type of technique is sometimes referred to as atomized chemical vapor deposition (CVD). Summary of the Invention

[0003] The aforementioned production methods suffer from the problem that the properties of the resulting oxide film differ from the expected properties. This disclosure provides a technique that suppresses the property changes in oxide films caused by the production method and enables the production of high-quality oxide films.

[0004] One factor causing the properties of the generated oxide film to differ from the expected properties is the difference between the concentration of the dopant in the oxide film and the expected concentration. In this regard, it has been found that in a feed solution containing a metal used as a dopant, the metal reacts with hydroxide ions and precipitates as a hydroxide. This hydroxide formation unintentionally reduces the concentration of the metal dissolved in the feed solution. Then, as the concentration of the metal dissolved in the feed solution decreases, the concentration of the dopant in the oxide film also decreases. As a result, the concentration of the dopant in the oxide film differs from the expected concentration, leading to the aforementioned problem of not obtaining the expected properties of the oxide film.

[0005] Based on this discovery, in the technique disclosed herein, the pH of the raw material solution in which the metal as a dopant is dissolved is less than 7. When the pH of the raw material solution is less than 7, the concentration of hydroxide ions in the raw material solution decreases. By reducing the concentration of hydroxide ions, the precipitation of the metal as a dopant in the form of hydroxide can be suppressed. This allows the concentration of the metal dissolved in the raw material solution to be properly adjusted and maintained at the desired value.

[0006] Based on the above technology, a method for producing a product having an oxide film of a second metal doped with a first metal is provided. The production method includes generating a mist from a raw material solution in which the first metal and the second metal are dissolved, and supplying the mist to the surface of a substrate to form an oxide film on the substrate surface. The pH of the raw material solution is less than 7. The production method may also include generating a first mist from a first raw material solution in which the first metal is dissolved, generating a second mist from a second raw material solution in which the second metal is dissolved, and supplying the first mist and the second mist to the surface of a substrate to form an oxide film on the substrate surface. The pH of the first raw material solution is less than 7.

[0007] According to the above production method, the precipitation of the first metal as a dopant in the raw material solution can be prevented. Therefore, the concentration of the first metal dissolved in the raw material solution can be correctly adjusted and maintained at the desired concentration. As a result, the concentration of the first metal contained in the oxide film is stabilized, and manufacturing variations in the oxide film properties can be suppressed. Attached Figure Description

[0008] Figure 1 This is a schematic diagram illustrating the film-forming equipment 10 used in the production method of the first embodiment.

[0009] Figure 2 This is a schematic cross-sectional view of product 2 produced by the production method of the first embodiment.

[0010] Figure 3 This is a flowchart illustrating the steps included in the production method of the first embodiment.

[0011] Figure 4 This is a diagram illustrating step (S12) of preparing the raw material solution 23 of the first embodiment.

[0012] Figure 5 This is a flowchart illustrating the steps of the production method of the second embodiment.

[0013] Figure 6 This is a diagram illustrating the steps (S12A) for preparing the raw material solution 23 of the second embodiment.

[0014] Figure 7 This is a diagram illustrating the steps (S12B) for preparing the raw material solution 23 of the second embodiment.

[0015] Figure 8 This is a flowchart illustrating the steps of the production method of the third embodiment.

[0016] Figure 9 This is a diagram illustrating the steps (S12C) for preparing the raw material solution 23 of the third embodiment.

[0017] Figure 10 This is a schematic diagram illustrating the film-forming equipment 100 used in the production method of the fourth embodiment.

[0018] Figure 11 This is a standard reduction-oxidation potential table in aqueous solutions of metals and hydrogen, as exemplified in this disclosure.

[0019] Figure 12 This is a standard reduction-oxidation potential table in aqueous solutions of metals and hydrogen, as exemplified in this disclosure. Detailed Implementation

[0020] In one embodiment of this technology, in the raw material solution (25°C) in which the first metal is dissolved, the standard redox potential of the first metal can be lower than the standard redox potential of hydrogen. With this configuration, the precipitation of the first metal as a hydroxide in the raw material solution in which it is dissolved can be further limited.

[0021] In one embodiment of this disclosure, the first metal may be at least one selected from Li, K, Rb, Cs, Ba, Ra, Sr, Ca, Na, Mg, No, Md, La, Fm, Y, Ce, Nd, Lu, Sm, Gd, Yb, Es, Ac, Cf, Am, Cm, Sc, Bk, Pu, Eu, Be, Th, Np, Hf, Al, U, Ti, Zr, Mn, V, Nb, Cr, Zn, Ga, Fe, Cd, In, Tl, Co, Ni, Mo, Sn, and Pb. These metals are examples of metals whose standard redox potential in the feed solution is lower than that of hydrogen.

[0022] In one embodiment of this disclosure, the concentration of the first metal in the feed solution containing the first metal may be 1 mol / L or less. However, the concentration of the first metal in the feed solution is not limited to this range and may be appropriately set according to the desired characteristics of the oxide film.

[0023] In one embodiment of this disclosure, the method may further include dissolving a first metal in an acidic solution and adjusting the pH of the acidic solution to be less than 7. According to this configuration, the concentration of the first metal to be dissolved in the raw material solution can be correctly adjusted and maintained at a desired concentration. For example, in the step of dissolving the first metal in the acidic solution, adjusting the pH of the acidic solution to a relatively low value can promote the dissolution of the first metal. Subsequently, the pH of the acidic solution in which the first metal is dissolved can be increased to a value less than 7.

[0024] In the above embodiment, in the step of dissolving the first metal in the acidic solution, the first metal can be dissolved in the acidic solution in a container made of a silicon-free (Si) material. According to this configuration, in the step of preparing the raw material solution, Si, as an impurity, can be prevented from being introduced into the raw material solution from the container. Conversely, if the container is made of a Si-containing material, Si may unintentionally contaminate the raw material solution. When Si contaminates the raw material solution, the resulting oxide film may also contain Si. Even if the amount of Si contained in the oxide film is very small, it may have a significant impact on the properties of the oxide film.

[0025] In the above embodiment, during the step of dissolving the first metal in the acidic solution, the gas generated when the first metal dissolves in the acidic solution can be used to maintain the container at a positive pressure relative to atmospheric pressure. This configuration prevents impurities in the air from unintentionally contaminating the raw material solution.

[0026] In one embodiment of this disclosure, the production method includes generating a first mist from a first feedstock solution in which a first metal is dissolved, and generating a second mist from a second feedstock solution in which a second metal is dissolved. The pH of the second feedstock solution in which the second metal is dissolved can be less than 7. According to this configuration, even in the second feedstock solution in which the second metal is dissolved, the precipitation of the second metal as a hydroxide can be limited. The concentration of the second metal dissolved in the second feedstock solution can be properly adjusted and maintained at a desired concentration, allowing the generation of a high-quality oxide film.

[0027] In one embodiment of the invention, the standard redox potential of the second metal can be lower than the standard redox potential of hydrogen in the feed solution in which the second metal is dissolved. According to this configuration, the precipitation of the second metal as a hydroxide in the feed solution in which the second metal is dissolved can be further limited.

[0028] In one embodiment of this disclosure, the second metal may be at least one selected from Li, K, Rb, Cs, Ba, Ra, Sr, Ca, Na, Mg, No, Md, La, Fm, Y, Ce, Nd, Lu, Sm, Gd, Yb, Es, Ac, Cf, Am, Cm, Sc, Bk, Pu, Eu, Be, Th, Np, Hf, Al, U, Ti, Zr, Mn, V, Nb, Cr, Zn, Ga, Fe, Cd, In, Tl, Co, Ni, Mo, Sn, and Pb. These metals are examples of metals whose standard redox potential in the feed solution is lower than that of hydrogen. The second metal is different from the first metal.

[0029] In one embodiment of this disclosure, the concentration of the second metal in the feed solution containing the dissolved second metal can be 1 mol / L or less. However, the concentration of the second metal in the feed solution is not limited to this range and can be appropriately set according to the desired characteristics of the oxide film.

[0030] In one embodiment of this disclosure, the method may further include dissolving the second metal in an acidic solution and adjusting the pH of the acidic solution containing the dissolved second metal to less than 7. According to this configuration, the concentration of the second metal to be dissolved in the raw material solution can be correctly adjusted and maintained at the desired concentration.

[0031] In the above embodiment, in the step of dissolving the second metal in the acidic solution, the second metal can be dissolved in the acidic solution in a container made of a Si-free material. According to this configuration, in the step of preparing the raw material solution, Si, as an impurity, can be prevented from being mixed into the raw material solution from the container.

[0032] In the above embodiment, during the step of dissolving the second metal in the acidic solution, the gas generated when the second metal dissolves in the acidic solution can be used to maintain the container at a positive pressure relative to atmospheric pressure. This configuration prevents impurities in the air from unintentionally contaminating the raw material solution.

[0033] In one embodiment of this disclosure, the oxide film may be a single-crystal film. Alternatively, the oxide film may be a semiconductor film.

[0034] (First Implementation Plan)

[0035] Referring to the accompanying drawings, the production method of the first embodiment is described. The production method of this embodiment mainly involves... Figure 1 The film-forming equipment 10 shown performs the process and produces... Figure 2 Product 2 is shown in the image. (As shown in the image) Figure 2 As shown, product 2 has an oxide film 6 on the surface of substrate 4. The oxide film 6 is composed of an oxide of a second metal doped with a first metal. Here, product 2 is not limited to a final product with a specific use and function, but also includes semi-finished products temporarily generated during the production of the final product.

[0036] Product 2 is, for example, a semiconductor device or a semi-finished semiconductor device. As an example, the first metal may be magnesium (Mg) and the second metal may be gallium (Ga). In this case, the oxide film 6 is a gallium oxide (Ga₂O₃) film containing magnesium as a dopant. The substrate 4 may be made of gallium iron oxide (GaFeO₃). The magnesium-containing gallium oxide (Ga₂O₃) coating film can be a monocrystalline film or a semiconductor film. However, the oxide film 6 in this embodiment is not limited to these. The oxide film 6 is not limited to a monocrystalline film and may be a polycrystalline film. Furthermore, the oxide film 6 is not limited to a semiconductor film and may be an insulating film or a conductive film.

[0037] First, refer to Figure 1 Film deposition apparatus 10 is described. Film deposition apparatus 10 is configured to form an oxide film 6 on the surface of a substrate 4 using atomization CVD. The substrate 4 is not limited to the gallium iron oxide substrate described above, but may be another semiconductor substrate or other substrates. Film deposition apparatus 10 includes a chamber 12 in which the substrate 4 is disposed, a heater 14 for heating the chamber 12, and a mist generation device 20 connected to the chamber 12.

[0038] There are no particular limitations on the specific configuration of chamber 12. As an example, chamber 12 in this embodiment has an upstream end 12a and a downstream end 12b, and extends tubularly from the upstream end 12a to the downstream end 12b in the longitudinal direction. A mist generating device 20 is connected to the upstream end 12a of chamber 12. An exhaust pipe 16 is connected to the downstream end 12b of chamber 12.

[0039] A step 13 for supporting the substrate 4 is disposed in the chamber 12. The step 13 has an inclined surface 13a on which the substrate 4 is disposed. The inclined surface 13a is inclined relative to the longitudinal direction of the chamber 12. Although there is no particular limitation, the angle formed by the inclined surface 13a relative to the longitudinal direction of the chamber 12 can be in the range of, for example, 30 degrees to 60 degrees, and can be, for example, 45 degrees.

[0040] There are no particular limitations on the specific configuration of heater 14. As an example, heater 14 in this embodiment has a plurality of annular heaters. The plurality of annular heaters are arranged in the longitudinal direction of chamber 12. Each of the annular heaters has an annular shape, and the annular heaters are arranged along the outer circumferential surface of chamber 12 to surround chamber 12. The annular heaters are grouped along the longitudinal direction of chamber 12, and the operation of the annular heaters is controlled for these groups.

[0041] The mist generating device 20 includes a raw material solution tank 22, a water tank 24, and an ultrasonic vibrator 26. The raw material solution tank 22 is a container for storing a raw material solution 23. As will be described in detail later, a first metal and a second metal, which are the main raw materials for the oxide film 6, are dissolved in the raw material solution 23. The raw material solution tank 22 is connected to the upstream end 12a of the chamber 12 via a mist supply channel 30. The water tank 24 is a container for storing water 25. The upper part of the water tank 24 is open, and the raw material solution tank 22 is inserted into the water tank 24 from the open upper part. The bottom surface of the raw material solution tank 22 is immersed in the water 25 within the water tank 24.

[0042] The ultrasonic vibrator 26 is a device that generates ultrasonic waves. The ultrasonic vibrator 26 is disposed at the bottom of the water tank 24 and faces the bottom surface of the raw material solution tank 22. The ultrasonic waves generated by the ultrasonic vibrator 26 are transmitted through the water 25 in the water tank 24 to the raw material solution 23 in the raw material solution tank 22. When the ultrasonic waves are transmitted to the raw material solution 23, the surface of the raw material solution 23 vibrates, causing a mist 23m of the raw material solution 23 to be generated in the raw material solution tank 22. Here, the bottom surface of the raw material solution tank 22 is preferably a membrane made of a flexible material, thereby facilitating the transmission of ultrasonic waves to the raw material solution 23.

[0043] The mist 23m generated in the raw material solution tank 22 is supplied to the chamber 12 through the mist supply channel 30. The carrier gas supply channel 32 is fluidly connected to the raw material solution tank 22, and the dilution gas supply channel 34 is fluidly connected to the mist supply channel 30. The carrier gas supply channel 32 supplies a carrier gas 33, such as N2 (nitrogen), to the raw material solution tank 22. The dilution gas supply channel 34 supplies a dilution gas 35, such as N2 (nitrogen), to the mist supply channel 30. The mist 23m is delivered to the chamber 12 at an appropriate density by the carrier gas 33 and the dilution gas 35.

[0044] In chamber 12, a gas containing mist 23m flows from upstream end 12a to downstream end 12b. Substrate 4 is disposed within chamber 12, and mist 23m of the raw material solution 23 is supplied to the surface of substrate 4. As described above, a first metal and a second metal are dissolved in the raw material solution 23, and mist 23m contains ions of both the first and second metals. As a result, an oxide of the second metal is deposited on the surface of substrate 4, while the first metal is incorporated into substrate 4 as a dopant. That is, an oxide film 6 of the second metal doped with the first metal is formed on the surface of substrate 4.

[0045] Next, we will refer to Figure 3 This embodiment describes a production method using film-forming equipment 10. For example... Figure 3As shown, the production method of this embodiment mainly includes the steps of preparing raw material solution 23 (S12, S14), generating mist 23m from raw material solution 23 (S16), and supplying mist 23m to the surface of substrate 4 (S18). As can be seen from the above description, the step of generating mist 23m from raw material solution 23 (S16) is performed by mist generating device 20, and the step of supplying mist 23m to the surface of substrate 4 (S18) is performed in chamber 12. These steps (S16, S18) are performed simultaneously and in parallel, and an oxide film 6 is formed on the surface of substrate 4. As described above, the first metal and the second metal are dissolved in raw material solution 23. By appropriately adjusting the concentrations of the first metal and the second metal in raw material solution 23, an oxide film 6 of the second metal doped with the first metal can be formed.

[0046] In contrast, the steps for preparing the raw material solution 23 (S12, S14) are performed before film formation via the film-forming device 10. As detailed later, in this step, an acidic raw material solution 23 with a pH adjusted to less than 7 is prepared. Even in the step of generating the mist 23m (S16), the pH of the raw material solution 23 is maintained at a value less than 7. As a result, the precipitation of the first metal dissolved in the raw material solution 23 as a hydroxide is prevented, and the concentration of the first metal is correctly adjusted and maintained at the desired concentration. Consequently, the concentration of the first metal contained in the oxide film 6 is stabilized, and manufacturing changes in the properties of the oxide film 6 can be suppressed. The lower the pH of the raw material solution 23, the stronger the precipitation of the first metal as a hydroxide is prevented. From this perspective, the pH of the raw material solution 23 can be less than 5 or less than 3.

[0047] The first metal is not limited to magnesium as exemplified above. The first metal may be selected from the group consisting of Li, K, Rb, Cs, Ba, Ra, Sr, Ca, Na, Mg, No, Md, La, Fm, Y, Ce, Nd, Lu, Sm, Gd, Yb, Es, Ac, Cf, Am, Cm, Sc, Bk, Pu, Eu, Be, Th, Np, Hf, Al, U, Ti, Zr, Mn, V, Nb, Cr, Zn, Ga, Fe, Cd, In, Tl, Co, Ni, Mo, Sn, and Pb. When these metals are used as the first metal, the standard redox potential of the first metal is less than the standard redox potential of hydrogen in the raw material solution 23 in which the first metal is dissolved (see [reference]). Figure 11 and 12 As a result, in the raw material solution 23 in which the first metal is dissolved, the precipitation of the first metal in the form of hydroxide can be further suppressed.

[0048] Furthermore, in the production method of this embodiment, the second metal is also dissolved in the raw material solution 23 in which the first metal is dissolved. In other words, the pH of the raw material solution 23 in which the second metal is dissolved is also adjusted to be less than 7. According to this configuration, not only the first metal but also the second metal is prevented from precipitating in the form of hydroxides. Therefore, the concentration of the second metal dissolved in the raw material solution 23 can be correctly adjusted and maintained at the expected concentration, and a high-quality oxide film 6 can be generated.

[0049] The second metal is not limited to gallium as exemplified above. The second metal is selected from the group consisting of Li, K, Rb, Cs, Ba, Ra, Sr, Ca, Na, Mg, No, Md, La, Fm, Y, Ce, Nd, Lu, Sm, Gd, Yb, Es, Ac, Cf, Am, Cm, Sc, Bk, Pu, Eu, Be, Th, Np, Hf, Al, U, Ti, Zr, Mn, V, Nb, Cr, Zn, Ga, Fe, Cd, In, Tl, Co, Ni, Mo, Sn, and Pb. When these metals are used as the second metal, the standard redox potential of the second metal is less than the standard redox potential of hydrogen in the raw material solution 23 in which the second metal is dissolved (see [reference]). Figure 11 and 12 As a result, in the raw material solution 23 in which the second metal is dissolved, the precipitation of the second metal as a hydroxide can be further suppressed. The second metal is different from the first metal.

[0050] Next, refer to Figure 4 The steps for preparing raw material solution 23 are described. Figure 3 (S12 and S14 in the text). Figure 4 As shown, in this step, a container 50 made of PTFE (polytetrafluoroethylene) is used. The container 50 can be sealed with a lid 52, also made of PTFE. PTFE is an example of a silicon-free (Si) material. An exhaust channel is defined in the lid 52 or in the upper part of the container 50. The cross-sectional area of ​​the exhaust channel is small, and the gas generated in the container 50 is configured to be discharged little by little. Here, the first metal as a dopant is magnesium, and the second metal as the main element of the oxide film 6 is gallium.

[0051] First, in container 50 with lid 52, 0.05 moles of metallic magnesium are dissolved in an acidic aqueous solution containing 0.11 moles of hydrogen chloride (HCl). Figure 3In this process, the reaction Mg + 2HCl → MgCl2 + H2 occurs, producing 0.05 mol magnesium chloride (MgCl2) and 0.05 mol hydrogen gas (H2). The produced hydrogen gas is gradually discharged through the exhaust channel, and container 50 is maintained at a positive pressure relative to atmospheric pressure. This series of processes is preferably carried out in a nitrogen atmosphere. Magnesium chloride dissolves immediately in water. The remaining 0.01 mol HCl is almost completely ionized. Then, pure water is added to the aqueous solution to make the total volume 1 L, and the pH is adjusted to a value less than 7. Figure 3 (S14 in the above procedure). According to the above procedure, an aqueous solution with a pH of 2 and a magnesium concentration of 0.05 mol / L can be obtained. By adding it to a raw material solution 23 in which gallium, as a second metal, is dissolved, a raw material solution 23 containing dissolved magnesium and gallium and with a pH less than 7 can be prepared.

[0052] In contrast, in conventional methods, the feed solution is prepared by dissolving 0.05 mol of magnesium chloride in pure water to a total volume of 1 L. Magnesium chloride hexahydrate (MgCl₂·6H₂O) is often used as the solute in this case. Magnesium chloride hexahydrate is obtained by dissolving magnesium hydroxide in hydrochloric acid to be neutralized and then concentrating it. However, during the heat treatment in the concentration process, undesirable impurities eluted from the container often cause contamination. Specifically, when using a typical borosilicate glass container, a small amount of silicon (Si) is eluted from the container. In this case, Si may be incorporated into the gallium oxide film during film formation and act as a donor. Therefore, it significantly affects the electrical properties of the oxide film.

[0053] Furthermore, it is difficult to obtain only the hexahydrate through concentration. For example, the dehydrated product (MgCl2), magnesium hydroxide (Mg(OH)2), and magnesium chloride (MgCl(OH)) may be mixed through concentration. Moreover, the hexahydrate (MgCl2·6H2O) is hygroscopic and therefore readily absorbs moisture from the atmosphere. When magnesium hydroxide is present in the presence of moisture, carbon dioxide can be introduced through the reaction 2Mg(OH)2 + CO2 → MgCO3·Mg(OH)2 + H2O. As a result, the oxide film 6 may contain carbon (C) as an unintended impurity. Magnesium hydroxide is less soluble in water than magnesium chloride and forms colorless colloidal particles in aqueous solution. Therefore, contamination by these impurities not only leads to quantitative errors but also makes it difficult to form a uniform doped film.

[0054] Regarding these points, in this embodiment, a container 50 made of a silicon-free (Si) material is used. Therefore, silicon contamination into the feed solution 23 can be prevented. Furthermore, by maintaining the container 50 at a positive pressure relative to atmospheric pressure, atmospheric impurities such as carbon can be prevented from contaminating the feed solution 23. Thus, not only is the concentration of the first metal in the feed solution 23 stabilized, but accidental contamination by impurities is also avoided. As a result, characteristic changes due to the production method can be suppressed, and a high-quality oxide film 6 can be formed.

[0055] (Second Implementation Plan)

[0056] Reference Figures 5 to 7 Describe the production method of the second implementation scheme. For example... Figure 5 As shown, in the production method of this embodiment, the steps (S12A, S12B, S14) for preparing the raw material solution 23 are changed compared to the production method of the first embodiment. Therefore, in the following description, the steps (S12A, S12B, S14) for preparing the raw material solution 23 in this embodiment will be mainly described, and the description of other common parts will be omitted by adding the same reference numerals.

[0057] In this embodiment, it can also be used in the steps (S12A, S12B, S14) of preparing the raw material solution 23. Figure 3 The container 50 is shown. Here, zinc (Zn) is used as the first metal to act as a dopant, and gallium is used as the second metal as the main element of the oxide film 6. First, as... Figure 6 As shown, 0.02 moles of zinc metal are dissolved in an aqueous solution containing 0.045 moles of hydrogen chloride. Figure 5 (S12A in the text). At this point, the reaction Zn + 2HCl → ZnCl2 + H2 occurs, producing 0.02 moles of hydrogen gas and an aqueous solution containing 0.02 moles of ZnCl2 and 0.005 moles of hydrogen chloride.

[0058] Next, as Figure 7 As shown, using a similar container 50, 0.2 moles of gallium metal were dissolved in an aqueous solution containing 0.605 moles of hydrogen chloride. Figure 5 (S12B in step S12). At this point, the reaction 2Ga + 6HCl → 2GaCl3 + 3H2 occurs, producing 0.3 moles of hydrogen gas and an aqueous solution containing 0.2 moles of gallium chloride (GaCl3) and 0.005 moles of hydrogen chloride. Then, the aqueous solution produced in step S12A is mixed with the aqueous solution produced in step S12B, and pure water is further added to bring the total volume to 1 L. The pH of the prepared solution is adjusted to less than 7. Figure 5(S14 in the original text). As a result, a raw material solution 23 with a pH of 2, a zinc concentration of 0.02 mol / L, and a gallium concentration of 0.2 mol / L can be obtained. By using the raw material solution 23, an oxide film 6 made of zinc-doped gallium oxide can be formed.

[0059] (Third Implementation Plan)

[0060] Reference Figure 8 and 9 Describe the production method of the third implementation scheme. For example... Figure 8 As shown, in the production method of this embodiment, compared with the production methods of the first embodiment and the second embodiment, the steps (S12C, S14) for preparing the raw material solution 23 are changed. Therefore, in the following description, the steps (S12C, S14) for preparing the raw material solution 23 in this embodiment will be mainly described, and the description of other common parts will be omitted by adding the same reference numerals.

[0061] In this embodiment, it can also be used in the steps (S12C, S14) of preparing the raw material solution 23. Figure 3 The container 50 is shown. Here, zinc is used as the first metal to act as a dopant, and gallium is used as the second metal as the main element of the oxide film 6. First, as... Figure 9 As shown, 0.02 moles of zinc metal and 0.2 moles of gallium metal are dissolved together in an aqueous solution containing 0.65 moles of hydrogen chloride in container 50. Preferably, the zinc and gallium metals are in granular form and container 50 is cooled from the outside. Therefore, the zinc and gallium metals can dissolve slowly and gradually, thus suppressing heat generation. Furthermore, this series of operations can be carried out in a high-purity nitrogen atmosphere.

[0062] Next, pure water is added to the aqueous solution prepared in step S12C to make the total volume 1L, and the pH is adjusted to less than 7. Figure 8 (S14 in the original text). As a result, a raw material solution 23 with a pH of 2, a zinc concentration of 0.02 mol / L, and a gallium concentration of 0.2 mol / L can be obtained. By using the raw material solution 23, an oxide film 6 made of zinc-doped gallium oxide can be formed.

[0063] (Fourth Implementation Plan)

[0064] Reference Figure 10 Describe the production method of the fourth embodiment. The production method of this embodiment differs from the production method of the first embodiment in that this method... Figure 10 The film-forming equipment 100 shown is used for this process. Figure 10As shown, the film-forming apparatus 100 of this embodiment has two mist-generating devices 20. That is, two raw material solutions 23 can be used in the film-forming apparatus 100. Therefore, although there are no particular limitations, the first raw material solution 23 in which a first metal is dissolved is disposed in one of the mist-generating devices 20, and the second raw material solution in which a second metal is dissolved is disposed in the other of the mist-generating devices 20. In this case, the first and second raw material solutions 23 may have the same pH or may have different pH values ​​from each other.

[0065] Although specific examples of the technology disclosed in this disclosure have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications to the specific examples described above. The technical elements described in this specification or drawings exhibit technical utility individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. The technology shown in this specification or drawings can achieve multiple objectives simultaneously and is technically useful by achieving one of these objectives.

Claims

1. A method for producing a product (2) comprising an oxide film (6) of a second metal doped with a first metal, the method comprising: A mist (23m) is generated from the raw material solution (23) in which the first metal and the second metal are dissolved; and The mist is supplied to the surface of the substrate (4) to form the oxide film on the surface of the substrate, wherein The pH value of the raw material solution is less than 7. The method further includes: The first metal is dissolved in an acidic solution; and The pH of the acidic solution is adjusted to be less than 7. The container is kept under positive pressure relative to atmospheric pressure by the gas generated when the first metal dissolves in the acidic solution.

2. The method according to claim 1, wherein in the raw material solution, the standard redox potential of the first metal is less than the standard redox potential of hydrogen.

3. The method according to claim 1, wherein the first metal is selected from the group consisting of Li, K, Rb, Cs, Ba, Ra, Sr, Ca, Na, Mg, No, Md, La, Fm, Y, Ce, Nd, Lu, Sm, Gd, Yb, Es, Ac, Cf, Am, Cm, Sc, Bk, Pu, Eu, Be, Th, Np, Hf, Al, U, Ti, Zr, Mn, V, Nb, Cr, Zn, Ga, Fe, Cd, In, Tl, Co, Ni, Mo, Sn, and Pb.

4. The method according to claim 1, wherein the concentration of the first metal in the raw material solution is less than 1 mol / L.

5. The method of claim 1, further comprising: The first metal is dissolved in the acidic solution in a container (50) made of a Si-free material.

6. The method according to claim 1, wherein the second metal is selected from the group consisting of Li, K, Rb, Cs, Ba, Ra, Sr, Ca, Na, Mg, No, Md, La, Fm, Y, Ce, Nd, Lu, Sm, Gd, Yb, Es, Ac, Cf, Am, Cm, Sc, Bk, Pu, Eu, Be, Th, Np, Hf, Al, U, Ti, Zr, Mn, V, Nb, Cr, Zn, Ga, Fe, Cd, In, Tl, Co, Ni, Mo, Sn, and Pb.

7. The method according to claim 1, wherein the concentration of the second metal in the raw material solution is less than 1 mol / L.

8. The method of claim 1, further comprising: The second metal is dissolved in an acidic solution; and The pH of the acidic solution is adjusted to be less than 7.

9. The method of claim 8, further comprising: The second metal is dissolved in the acidic solution in a container made of a Si-free material.

10. The method of claim 9, further comprising: The container is kept under positive pressure relative to atmospheric pressure by the gas generated when the second metal dissolves in the acidic solution.

11. The method according to claim 1, wherein the oxide film is a single crystal film.

12. The method according to any one of claims 1 to 11, wherein the oxide film is a semiconductor film.

13. A method for producing a product (2) comprising an oxide film (6) of a second metal doped with a first metal, the method comprising: A first mist (23m) is generated from a first raw material solution in which the first metal is dissolved; A second mist (23m) is generated from a second raw material solution in which the second metal is dissolved; and The first mist and the second mist are supplied to the surface of the substrate (4) to form the oxide film on the surface of the substrate, wherein The pH of the first raw material solution is less than 7. The method further includes: The first metal is dissolved in an acidic solution; and The pH of the acidic solution is adjusted to be less than 7. The container is kept under positive pressure relative to atmospheric pressure by the gas generated when the first metal dissolves in the acidic solution.

14. The method according to claim 13, wherein the pH of the second raw material solution is less than 7.

15. The method of claim 13, wherein in the first raw material solution, the standard redox potential of the first metal is less than the standard redox potential of hydrogen.

16. The method according to any one of claims 13 to 15, wherein in the second raw material solution, the standard redox potential of the second metal is less than the standard redox potential of hydrogen.

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