Film forming method

Abstract

The present application provides a film forming method. The present application is a film forming method in which a raw material solution that has been atomized is heat treated to form a film, and includes the following steps: atomizing or dropletizing the raw material solution to generate mist; using a carrier gas to transport the mist to a film forming section; and supplying the mist from a nozzle to a substrate in the film forming section, heat treating the substrate to form a film, and when the area of the opening surface of the nozzle is set as S [cm 2 ], the longest distance among the distances from a point in the opening surface to the surface of the substrate is set as H [cm], and the flow rate of the carrier gas supplied from the nozzle is set as Q [L / min], SH / Q≧0.015 is satisfied. Thus, a film forming method is provided in which abnormal growth is suppressed and a film with good surface smoothness is formed.

Description

Technical Field

[0001] This invention relates to a film-forming method that uses a mist-like raw material solution to form a film on a substrate. Background Technology

[0002] Previously, high-vacuum film deposition devices capable of achieving non-equilibrium states, such as pulsed laser deposition (PLD), molecular beam epitaxy (MBE), and sputtering, have been developed to fabricate oxide semiconductors that were previously impossible to produce using methods such as melt deposition. Furthermore, a mist chemical vapor deposition (MistCVD) method, which uses atomized raw materials to crystallize and grow on a substrate, has been developed to fabricate gallium oxide (α-Ga₂O₃) with a corundum structure. α-Ga₂O₃, as a semiconductor with a large band gap, is expected to be used in next-generation switching devices that can achieve high breakdown voltage, low loss, and high heat resistance.

[0003] Regarding mist CVD, Patent Document 1 describes a tubular furnace-type mist CVD apparatus. Patent Document 2 describes a fine channel type mist CVD apparatus. Patent Document 3 describes a linear source type mist CVD apparatus. Patent Document 4 describes a tubular furnace-type mist CVD apparatus, which differs from the mist CVD apparatus described in Patent Document 1 in terms of introducing carrier gas into the mist generator. Patent Document 5 describes a mist CVD apparatus in which a substrate is provided above the mist generator, and the susceptor is a rotating stage mounted on a heating plate.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 01-257337

[0007] Patent Document 2: Japanese Patent Application Publication No. 2005-307238

[0008] Patent Document 3: Japanese Patent Application Publication No. 2012-046772

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

[0010] Patent Document 5: Japanese Patent Application Publication No. 2014-063973 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] Unlike other CVD methods, fog CVD can be performed at relatively low temperatures and can also produce quasi-stable crystalline structures such as the corundum structure of α-Ga₂O₃. However, the inventors of this invention have discovered the following problems: when fog CVD is used for film formation, pits are formed on the film surface, resulting in poor surface smoothness. Furthermore, films containing a large number of pits have the problem that these pits become fatal defects, leading to insulation breakdown in semiconductor devices. Moreover, removing pits by polishing increases the number of steps involved in manufacturing semiconductor devices.

[0013] The present invention was made to solve the aforementioned problems, and its purpose is to provide a film with good surface smoothness that suppresses pits, and a film-forming method for forming such a film.

[0014] Technical means to solve the problem

[0015] The present invention is made to achieve the aforementioned objective, and provides an oxide semiconductor film, which uses gallium as the main component, and the oxide semiconductor film has a corundum structure, and the surface of the oxide semiconductor film has fewer than 10,000 pits / cm2.

[0016] This type of oxide semiconductor film is readily available and inexpensive, and has excellent surface smoothness, making it suitable for use in semiconductor devices.

[0017] At this point, the number of pits on the surface of the oxide semiconductor film can be set to less than 100 per cm².

[0018] As a result, it has superior surface smoothness and is more suitable for use in semiconductor devices.

[0019] At this time, the area of ​​the oxide semiconductor film can be set to 10 cm2 or more.

[0020] Thus, it becomes a large-area oxide semiconductor film with excellent surface smoothness, suitable for use in semiconductor devices.

[0021] At this time, the pits on the surface of the oxide semiconductor film can be configured with an opening diameter of 10 nm to 10 μm and a depth of 10 nm to 10 μm.

[0022] This results in a large-area oxide semiconductor film with superior surface smoothness, making it more suitable for use in semiconductor devices.

[0023] At this point, a semiconductor device comprising the oxide semiconductor film can be fabricated.

[0024] Thus, it becomes a semiconductor device with excellent characteristics.

[0025] Furthermore, the present invention provides a film-forming method, which involves heat-treating an atomized raw material solution to form a film, and includes the following steps:

[0026] The raw material solution is atomized or dropletized to generate a mist;

[0027] The mist is transported to the film-forming section using a carrier gas; and

[0028] In the film-forming section, the mist is supplied from a nozzle to the substrate, and heat treatment is performed on the substrate to form a film.

[0029] When the area of ​​the nozzle opening is set to S [cm2], the longest distance between a point in the opening and the surface of the substrate is set to H [cm], and the flow rate of the carrier gas supplied from the nozzle is set to Q [L / min], then SH / Q≧0.015 is set.

[0030] This film-forming method can be used to form a film that suppresses surface pits and has good smoothness.

[0031] At this time, the raw material solution may contain gallium.

[0032] This allows for the formation of gallium-containing films that suppress surface pits and achieve good smoothness.

[0033] At this time, the raw material solution may contain halogens.

[0034] This allows for the formation of a film that further suppresses surface pits and achieves better smoothness.

[0035] At this time, when the temperature of the heat treatment is set to T [°C], it can be set to ST / Q≧40.

[0036] This allows for the formation of a film that further suppresses surface pits and achieves better smoothness.

[0037] At this time, the mist can be supplied to the substrate from the nozzle located vertically above the substrate.

[0038] This allows for the formation of a film that further suppresses surface pits and achieves better smoothness.

[0039] At this time, the substrate can be moved below the nozzle.

[0040] This allows for the formation of films with fewer pits and better smoothness over a large area.

[0041] At this time, when the area of ​​the surface of the substrate to be film-formed is set to A[cm2], S / A≦0.3 is set.

[0042] This allows for the formation of films with fewer pits and better smoothness over a large area.

[0043] At this time, the opening surface of the nozzle can be rectangular.

[0044] This allows for the formation of films with fewer pits and better smoothness over a large area.

[0045] At this time, when the length of the major axis of the nozzle opening surface is set to L[cm] and the maximum length of the nozzle in the major axis direction within the surface of the substrate to be film-forming is set to R[cm], L / R≧1 is set.

[0046] Therefore, it is easy to form a film with few pits and good smoothness over a large area.

[0047] At this time, the area of ​​the substrate can be set to 10 cm2 or more.

[0048] This allows for the formation of films with fewer pits and better smoothness over a large area.

[0049] The effects of the invention

[0050] As described above, the oxide semiconductor film according to the present invention has fewer pits and excellent surface smoothness, making it a suitable oxide semiconductor film for use in semiconductor devices.

[0051] Moreover, according to the film formation method of the present invention, a film with few surface pits and good smoothness can be formed in the fog CVD method using a simple method. Attached Figure Description

[0052] Figure 1 This is a schematic structural diagram illustrating an example of the film-forming apparatus used in this invention.

[0053] Figure 2 A diagram illustrating an example of the atomizing section used in this invention.

[0054] Figure 3 A diagram illustrating an example of the film-forming portion used in this invention.

[0055] Figure 4 A diagram illustrating an example of the nozzle used in this invention.

[0056] Figure 5 A diagram illustrating an example of a film-forming section comprising multiple nozzles.

[0057] Figure 6 A diagram illustrating an example of a nozzle comprising multiple opening surfaces.

[0058] Figure 7 A diagram illustrating an example of the nozzle used in this invention.

[0059] Figure 8 A diagram illustrating an example of the nozzle used in this invention.

[0060] Figure 9 The figure illustrates an example of the moving mechanism of the substrate used in this invention.

[0061] Figure 10 A diagram illustrating an example of a moving mechanism that reciprocates below the nozzle.

[0062] Figure 11 The diagram illustrates an example of a rotary moving mechanism that moves in one direction below the nozzle.

[0063] Figure 12 A graph showing the results of Experiment Example 1.

[0064] Figure 13 A diagram illustrating the structure of the semiconductor device fabricated in Example 2.

[0065] Figure 14 A graph showing the results of Experiment Example 2.

[0066] Figure 15 A diagram to represent a pit.

[0067] Figure 16 A figure illustrating an example of the oxide semiconductor film of the present invention. Detailed Implementation

[0068] As described above, there is a need for an oxide semiconductor film with few pits and excellent surface smoothness at low cost, and a method for manufacturing an oxide semiconductor film that simply and inexpensively utilizes a low-temperature process to form an oxide semiconductor film with few pits and excellent surface smoothness.

[0069] The inventors of this invention have conducted repeated and diligent research on the aforementioned subject matter, and have discovered that a material with gallium as its main component, a corundum structure, and a surface pit density of 10,000 pits / cm² is suitable. 2 The following oxide semiconductor films are readily available and inexpensive, and have excellent surface smoothness, making them suitable for use in semiconductor devices, thus completing this invention.

[0070] The inventors of this invention have repeatedly and diligently studied the aforementioned problem, and as a result, discovered that a film with few pits and good smoothness can be formed using the following film-forming method, thus completing this invention. The film-forming method involves heat-treating an atomized raw material solution to form a film, and includes the following steps: atomizing or dropletizing the raw material solution to generate mist; transporting the mist to a film-forming section using a carrier gas; and supplying the mist from a nozzle to a substrate in the film-forming section, performing heat treatment on the substrate to form a film, and setting the area of ​​the nozzle opening surface as S [cm²]. 2Let H[cm] be the longest distance between a point in the opening and the surface of the substrate, and let Q[L / min] be the flow rate of the carrier gas supplied from the nozzle, then let SH / Q≧0.015.

[0071] The present invention will now be described in detail, but the present invention is not limited to these descriptions.

[0072] The following explanation is based on the accompanying drawings.

[0073] [Oxide semiconductor film]

[0074] The oxide semiconductor film of the present invention is characterized by having gallium as the main component, a corundum structure, and a pit density of 10,000 pits / cm. 2 The following describes the process. Typically, oxide semiconductor films contain metal and oxygen; however, in the oxide semiconductor film of this invention, gallium is the main metal component. The term "main component" here refers to a metal composition that is 50% to 100% gallium. Furthermore, "gallium-based" means containing gallium as a metal component. Other metal components besides gallium may include, for example, one or more metals selected from iron, indium, aluminum, vanadium, titanium, chromium, rhodium, iridium, nickel, and cobalt.

[0075] The preferred number of pits is less than 10,000 per cm. 2 More preferably 100 per cm 2 Furthermore, it is preferable to have fewer than 100 per cm. 2 There is no specific lower limit for the number of pits. It can also be 0.01 pits / cm. 2 above.

[0076] The oxide semiconductor film may contain dopants depending on the application. The dopants are not particularly limited. Examples include n-type dopants such as tin, germanium, silicon, titanium, zirconium, vanadium, or niobium; or p-type dopants such as copper, silver, tin, iridium, or rhodium. The concentration of the dopant may, for example, be about 1.0 × 10⁻⁶. 16 / cm 3 ~1.0×10 22 / cm 3 It can be set to approximately 1.0 × 10 17 / cm 3 The following low concentrations can also be set to approximately 1.0 × 10⁻⁶. 20 / cm 3 The above are high concentrations.

[0077] Here, the term "pit" as used in this invention refers to... Figure 15These depressions formed on the membrane surface can be observed using optical microscopes, scanning electron microscopes (SEM), and transmission electron microscopes (TEM). The opening diameter of the depressions is approximately 10 nm to 10 μm, and the depth is 10 nm to 10 μm.

[0078] While the exact cause of pit formation is unclear, it can be assumed that when the velocity component of the fog in the direction orthogonal to the substrate is high, and the weight (moisture content) of the fog at the time of arrival at the substrate is also high, the impulse when the fog collides with the substrate increases. This leads to a localized oversupply of raw material, resulting in unreacted components or by-reactants remaining on the film. These residues, present on the film surface, can be considered to hinder local film growth. Therefore, it can be argued that by utilizing the conditions described later—reducing the velocity component of the fog in the direction orthogonal to the substrate and decreasing the weight (moisture content) of the fog at the time of arrival at the substrate—pit formation can be suppressed.

[0079] In the oxide semiconductor film of the present invention, the film thickness is not particularly limited. For example, it can be 0.05 μm to 100 μm, preferably 0.1 μm to 50 μm, and more preferably 0.5 μm to 20 μm.

[0080] The oxide semiconductor film 180 of the present invention, as shown in the figure Figure 16 As shown, it is formed on substrate 181.

[0081] Furthermore, other layers may be inserted between the substrate 181 and the oxide semiconductor film 180. These other layers are layers that are different from the substrate 181 and the outermost oxide semiconductor film 180, and may be, for example, any of the following: a crystalline oxide film, an insulating film, a metal film, etc.

[0082] The area of ​​the oxide semiconductor film is preferably 10 cm². 2 In the case of a circular shape, a diameter of 2 inches (50 mm) or more is preferred. There is no particular upper limit to the area; it can be 750 cm². 2 In the case of a round shape, the diameter should be 12 inches (300 mm) or less.

[0083] The oxide semiconductor film of the present invention can be used in semiconductor devices through appropriate structural design. For example, it can be used to form the semiconductor layers of Schottky Barrier Diode (SBD), Metal Semiconductor-Field Effect Transistor (MESFET), High Electron Mobility Transistor (HEMT), Metal Oxide Semiconductor-Field Effect Transistor (MOSFET), Static Induction Transistor (SIT), Junction Field Effect Transistor (JFET), Insulated-Gate Bipolar Transistor (IGBT), Light Emitting Diode (LED), etc.

[0084] [Film-forming device]

[0085] Figure 1 The diagram shows an example of a film-forming apparatus 101 that can be used in the film-forming method of the present invention. The film-forming apparatus 101 includes: an atomizing unit 120 for atomizing a raw material solution to generate mist; a carrier gas supply unit 130 for supplying a carrier gas for transporting the mist; a film-forming unit 140 for heat-treating the mist to form a film on a substrate; and a transport unit 109 for connecting the atomizing unit 120 and the film-forming unit 140 and transporting the mist using the carrier gas. Furthermore, the film-forming apparatus 101 can also be controlled by a control unit (not shown) that includes controlling the entire or a portion of the film-forming apparatus 101.

[0086] Here, the fog mentioned in this invention refers to the general term for liquid microparticles dispersed in a gas, and also includes fog as mist, droplets, etc.

[0087] (Atomization section)

[0088] The atomizing unit 120 atomizes the raw material solution to generate mist. The atomization method is not particularly limited as long as it atomizes the raw material solution; any well-known atomization method can be used. However, an atomization method utilizing ultrasonic vibration is preferred because it allows for more stable atomization.

[0089] An example of this atomizing section 120 is shown below Figure 2For example, it may include: a mist generating source 104 containing a raw material solution 104a; a container 105 containing a medium capable of transmitting ultrasonic vibrations, such as water 105a; and an ultrasonic transducer 106 mounted on the bottom surface of the container 105. Specifically, a support (not shown) is used to house the mist generating source 104, which contains the container holding the raw material solution 104a, within the container 105 containing the water 105a. An ultrasonic transducer 106 is provided at the bottom of the container 105 and connected to an exciter 116. Furthermore, if the exciter 116 is activated, the ultrasonic transducer 106 vibrates, and ultrasonic waves propagate through the water 105a into the mist generating source 104, atomizing the raw material solution 104a.

[0090] (Carrier Gas Supply Department)

[0091] The carrier gas supply unit 130 includes a carrier gas source 102a for supplying carrier gas, and may also include a flow regulating valve 103a for adjusting the flow rate of the carrier gas supplied from the carrier gas source 102a. Furthermore, it may include a dilution carrier gas source 102b for supplying dilution carrier gas, or a flow regulating valve 103b for adjusting the flow rate of the dilution carrier gas supplied from the dilution carrier gas source 102b, depending on the need. Moreover, the carrier gas supply unit may be a single location or two or more locations.

[0092] (film-forming part)

[0093] In the film-forming section 140, the mist is heated to perform heat treatment, forming a film on part or all of the surface of the substrate 110. The film-forming section 140 may be partially or entirely surrounded, or it may not be surrounded at all. For example, it may be as follows... Figure 1 As shown, the film-forming section 140 is entirely surrounded by a film-forming chamber 107. A substrate 110 is disposed in the film-forming section 140, and a heating plate 108 for heating the substrate 110 may be included. The heating plate 108 may be as follows: Figure 1 It can be located inside the film-forming chamber 107 as shown, or it can be located outside the film-forming chamber 107. Furthermore, it may include a moving stage 161a. Details will be described below.

[0094] Furthermore, in the film-forming section 140, such as Figure 3 As shown, a nozzle 150 is provided for supplying mist to the substrate 110. An example of the nozzle 150 is shown in... Figure 4 The nozzle 150 includes a connecting portion 151 that connects the conveying portion 109 to the nozzle 150, and an opening surface 152 for spraying mist. The location of the nozzle 150 is not particularly limited. Figure 3Alternatively, the substrate 110 can be placed on the lower surface of the film-forming chamber 107, with a nozzle 150 or the like mounted vertically above the substrate, thus facing upwards. Or, the substrate 110 can be placed on the upper surface of the film-forming chamber 107, with a nozzle 150 or the like mounted vertically below the substrate, thus facing downwards.

[0095] There are no particular restrictions on the number of nozzles or the number of nozzle openings, as long as there is one or more. For example... Figure 5 That includes multiple nozzles 150a and 150b, or as follows Figure 6 That includes the opening face of multiple nozzles 150c.

[0096] Furthermore, the angle between the plane of the nozzle opening 152 and the plane of the substrate 110 is not particularly limited. Figure 7 The nozzle 150d is configured as shown, and this nozzle 150d includes an opening face 152 of the nozzle that is tilted in a manner that facilitates the flow of mist in a specific direction, or as shown... Figure 8 Thus, a nozzle 150e is provided that tilts a portion of the nozzle's opening surface, but preferably as follows: Figure 4 In this way, the substrate 110 is arranged parallel to the opening surface of the nozzle. The reason for this is that a film with fewer pits and excellent smoothness can be formed using a simpler structure.

[0097] Furthermore, the film-forming section 140 may be equipped with a position adjustment mechanism (not shown) that can appropriately adjust the distance H [cm] between the point in the nozzle opening surface 152 and the surface of the substrate 110 within the range described below.

[0098] Furthermore, the nozzle 150 can be configured as a structure assembled from multiple components, and the area of ​​the nozzle opening surface can be appropriately adjusted by adjusting the size of the components.

[0099] The shape of the nozzle opening 152 is not particularly limited. It can be polygonal, circular, elliptical, etc., but is preferably quadrilateral, and more preferably rectangular.

[0100] Moreover, it is possible Figure 9 As shown, the film-forming section 140 includes a moving mechanism 160 that moves the substrate 110 below the nozzle 150. The direction of substrate movement is not particularly limited. The illustration shows the film-forming section 140, including the moving mechanisms 160a and 160b, viewed from above the substrate 110. Figure 10 and Figure 11 The following methods are available: (e.g.) Figure 10 As shown, it includes a movable stage 161a on which a substrate 110 and a heating plate 108 are placed, and the substrate 110 and the heating plate 108 move back and forth below the nozzle 150; or as Figure 11 As shown, the substrate 110 and the heating plate 108 are rotated and moved below the nozzle 150 using a movable stage 161b that carries the substrate 110 and the heating plate 108. Moreover, a mechanism for rotating the substrate may also be included to rotate the substrate.

[0101] When setting up the substrate moving mechanism, there is no particular limitation on the speed or range of substrate movement. The number of times a substrate passes under the nozzle can be 0.1 times or more per minute, preferably 0.5 times or more, and more preferably 1 time or more. If the number of times is 0.1 times or more, the portion where the local gas supply is excessive disappears (i.e., the SH / Q does not decrease locally), thereby preventing the pits from increasing and resulting in a film with good surface smoothness. Moreover, there is no particular upper limit to the number of times. If the number of times increases, the fixation of the substrate becomes unstable due to inertial forces. Therefore, it is preferable to keep the number of times to be 120 times or less, preferably 60 times or less.

[0102] More specifically, Figure 10 In the case of such a moving mechanism, the moving speed of the substrate is set to v [mm / min] relative to the amplitude D [mm] of the moving substrate. v / D is preferably 0.1 / min or more, more preferably 0.5 / min or more and 120 / min or less, and more preferably 1 / min to 60 / min. D is not particularly limited, but is preferably 100 mm or more (or 100 mm or more if it is 4 inches), and the upper limit is not particularly limited. Increasing this value allows each nozzle to deposit film on a large number of substrates. However, the film-forming speed per substrate decreases, so setting it to 1000 mm or less and limiting the number of substrates that can be film-formed by each nozzle is preferable for excellent productivity. v is not particularly limited. It is preferably 10 mm / min or more and 30000 mm / min or less, more preferably 30 mm / min or more and 12000 mm / min or less, and more preferably 60 mm / min or more and 6000 mm / min or less. Figure 11 In the case of such a rotary moving mechanism, the speed should be 0.1 rpm or more, preferably 0.5 rpm to 120 rpm, and more preferably 1 rpm to 60 rpm.

[0103] Furthermore, when the film-forming section 140 is surrounded, an exhaust port 111 for exhaust gas can be provided at a position that does not affect the supply of mist to the substrate 110. The exhaust port 111 can be provided in one place or in two or more places as long as it does not affect the supply of mist.

[0104] (Transportation Department)

[0105] The conveying unit 109 connects the atomizing unit 120 and the film-forming unit 140. Using a carrier gas, mist is conveyed from the mist generation source 104 of the atomizing unit 120 to the nozzle 150 of the film-forming unit 140 via the conveying unit 109. The conveying unit 109 may, for example, be a supply pipe 109a. The supply pipe 109a may, for example, be a quartz tube or a resin tube.

[0106] [Film Formation Method]

[0107] Next, the film-forming method of the present invention will be described. The present invention is a film-forming method that heat-treats an atomized raw material solution to form a film, and includes the following steps: atomizing or dropletizing the raw material solution to generate a mist; transporting the mist to a film-forming section using a carrier gas; and supplying the mist from a nozzle to a substrate in the film-forming section, performing heat treatment on the substrate to form a film, wherein the area of ​​the opening surface of the nozzle is set to S [cm²]. 2 Let H[cm] be the longest distance between a point in the opening and the surface of the substrate, and let Q[L / min] be the flow rate of the carrier gas supplied from the nozzle, then let SH / Q≧0.015.

[0108] (The process of generating fog)

[0109] First, the raw material solution 104a is atomized or dropletized to generate a mist. This step can be performed using an atomizing unit 120 as described above. Here, the raw material solution (aqueous solution) 104a is not particularly limited as long as it contains an atomizable material; it can be an inorganic or organic material. Regarding the raw material solution, a solution of metal or metal compound can be suitable, and a solution containing one or more metals selected from gallium, iron, indium, aluminum, vanadium, titanium, chromium, rhodium, nickel, and cobalt can be used. Among these, gallium is particularly preferred, as it can form a gallium-containing film with good smoothness and suppression of pits.

[0110] Regarding the raw material solution, there are no particular limitations as long as the solution of the metal (compound) can be atomized. Suitable raw material solutions may be those obtained by dissolving or dispersing the metal in an organic solvent or water in the form of a complex or salt. Examples of complex forms include: acetylacetonate complexes, carbonyl complexes, ammonia complexes, hydride complexes, etc. Examples of salt forms include: metal chloride salts, metal bromide salts, metal iodide salts, etc. Furthermore, solutions obtained by dissolving the metal in hydrobromic acid, hydrochloric acid, hydroiodic acid, etc., can also be used as aqueous solutions of the salt. The solute concentration is preferably 0.01 mol / L to 1 mol / L. Among these, the inclusion of halogens is particularly preferred, as it can form a film with better smoothness by further suppressing pits.

[0111] Furthermore, the raw material solution may also contain additives such as hydrohalic acids or oxidizing agents. 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; hypochlorous acid (HClO), perchloric acid, nitric acid, and ozone water; and organic peroxides such as peracetic acid or nitrobenzene.

[0112] Furthermore, the raw material solution may also contain dopants. The dopants are not particularly limited. Examples include n-type dopants such as tin, germanium, silicon, titanium, zirconium, vanadium, or niobium; or p-type dopants such as copper, silver, tin, iridium, or rhodium. The concentration of the dopant may, for example, be approximately 1.0 × 10⁻⁶. -9 mol / L to 1.0 mol / L, can be set to approximately 1.0 × 10⁻⁶. -7 Low concentrations below mol / L can also be set as high concentrations above approximately 0.01 mol / L.

[0113] (The process of transporting fog)

[0114] Next, the generated mist is transported to the film-forming section using a carrier gas. The type of carrier gas is not particularly limited and can be appropriately selected based on the film-forming material. Examples include inert gases such as oxygen, ozone, nitrogen, or argon, or reducing gases such as hydrogen or foaming gases. Furthermore, the carrier gas can be one type or two or more. For example, a diluent gas obtained by diluting the same gas as the first carrier gas with another gas (e.g., diluting it 10 times) can be used as a second carrier gas; air can also be used.

[0115] In this invention, the carrier gas flow rate Q [L / min] represents the total flow rate of the carrier gas. For example, when a dilution carrier gas is used in addition to the carrier gas, the total flow rate of the carrier gas and the dilution carrier gas is set as Q. Furthermore, Q is set as the measured value at 20°C. When the measurement is performed at other temperatures or when measuring different types of flow rates (mass flow rate, etc.), the volumetric flow rate at 20°C can be converted using the gas equation of state.

[0116] Furthermore, the flow rate of the carrier gas (total flow rate in the case of using multiple gases) is not particularly limited as long as the conditions described later are met. For example, when forming a film on a substrate with a diameter of 4 inches (100 mm), it is preferably set to 1 L / min to 80 L / min, and more preferably to 4 L / min to 40 L / min.

[0117] (The process of film formation)

[0118] Next, the mist is supplied from the nozzle to the substrate in the film-forming section, and a film is formed by heat treatment on the substrate. Here, the area of ​​the nozzle opening surface 152 is set to S [cm]. 2 When the flow rate of the carrier gas is set to Q [L / min], and the longest distance between a point within the nozzle opening surface 152 and the surface of the substrate 110 is set to H [cm], it is acceptable for SH / Q to be 0.015 or higher, preferably 0.1 or higher and 20 or lower. If SH / Q is less than 0.015, the film will have many pits and poor surface smoothness. Moreover, the velocity of the carrier gas in the direction orthogonal to the substrate from the nozzle opening surface 152 should preferably be 0.01 m / s or higher and less than 8.0 m / s, preferably 0.1 m / s or higher and less than 2.5 m / s.

[0119] Furthermore, the area S of the nozzle opening surface 152 should preferably be 0.1 cm². 2 Above and less than 400 cm 2 The shortest distance H between the nozzle opening surface 152 and the substrate 110 is preferably 0.1 cm or more and 6.0 cm or less, more preferably 0.2 cm or more and 3.0 cm or less.

[0120] Let the area of ​​the nozzle opening surface 152 be S[cm] 2 Let the area of ​​the substrate be A[cm]. 2 When the S / A ratio is less than or equal to 0.3, it is preferable to have a ratio of 0.004 to 0.15. If S / A is less than or equal to 0.3, the resulting film has fewer pits and a smoother surface. Furthermore, the substrate area A is preferably 10 cm². 2 In the case of a circular substrate, a diameter of 2 inches (50 mm) or more is preferred. This is because a film with good surface smoothness can be formed over a larger area. Moreover, there is no particular upper limit to A. The larger the area of ​​the substrate, the larger the area of ​​the film can be obtained in a single deposition process, thus making it suitable for mass production.

[0121] Regarding the nozzle, a rectangular nozzle with a rectangular opening is preferred. When the length of the major axis of the nozzle opening 152 is defined as L [cm], and the maximum length of the nozzle along its major axis on the substrate is defined as R [cm], it is preferable that L / R ≥ 1. This is because if L / R ≥ 1, a smooth film can be easily formed on a large-area substrate. Here, the major axis refers to the long side of the rectangle. There is no particular upper limit to L / R, but the larger L / R is, the more mist is not supplied to the substrate; therefore, it is preferable to set it to 3 or less.

[0122] Regarding heat treatment, any reaction can be achieved by heating, and the reaction conditions are not particularly limited. The temperature can be appropriately set according to the raw material or the film-forming material. For example, the heating temperature is in the range of 120°C to 600°C, preferably in the range of 200°C to 600°C, and more preferably in the range of 300°C to 550°C. The heating temperature is set to T [°C], and the area of ​​the nozzle opening surface 152 is set to S [cm²]. 2 When the carrier gas flow rate is set to Q [L / min], ST / Q is preferably 40 or more, more preferably 100 or more and 2000 or less. If ST / Q ≥ 40, a membrane with fewer pits and better surface smoothness is obtained.

[0123] Heat treatment can be carried out under any environment, including vacuum, oxygen-free environment, reducing gas environment, air environment, and oxygen environment, as long as the setting is appropriate according to the film-forming material. Moreover, the reaction pressure can be carried out under atmospheric pressure, pressurized conditions, or depressurized conditions. If film formation is carried out under atmospheric pressure, the apparatus structure can be simplified, which is therefore preferred.

[0124] The substrate 110 is not particularly limited as long as it can form a film and support the film. The material of the substrate 110 is also not particularly limited; well-known substrates can be used, and it can be an organic compound or an inorganic compound. Examples include: polysulfone, polyethersulfone, polyphenylene sulfide, polyetheretherketone, polyimide, polyetherimide, fluoropolymer, iron or aluminum, stainless steel, gold and other metals, silicon, sapphire, quartz, glass, gallium oxide, lithium niobate, lithium tantalate, etc., but are not limited to these. The thickness of the substrate is not particularly limited, but is preferably 10 μm to 2000 μm, more preferably 50 μm to 800 μm.

[0125] Film formation can be performed directly on the substrate or stacked on an intermediate layer formed on the substrate. The intermediate layer is not particularly limited; for example, an oxide comprising any one of aluminum, titanium, vanadium, chromium, iron, gallium, rhodium, indium, or iridium can be used as the main component. More specifically, it can be Al₂O₃, Ti₂O₃, V₂O₃, Cr₂O₃, Fe₂O₃, Ga₂O₃, Rh₂O₃, In₂O₃, or Ir₂O₃. Furthermore, when two elements selected from the aforementioned metallic elements are designated as A and B, it can be designated as (A...). x B 1-x The binary metal oxide represented by )2O3 (0 < x < 1), or, when three elements selected from the metal elements are designated as A, B, and C, it can be designated as (A x B y C 1-x-y The ternary metal oxides represented by )2O3 (0 < x < 1, 0 < y < 1, 0 < x + y < 1).

[0126] In this invention, annealing can also be performed after film formation. The annealing temperature is not particularly limited, but is preferably below 600°C, more preferably below 550°C. This is because it does not damage the crystallinity of the film. The annealing time is not particularly limited, but is preferably from 10 seconds to 10 hours, more preferably from 10 seconds to 1 hour.

[0127] (Stripping)

[0128] The substrate 110 can also be peeled off from the oxide semiconductor film. The peeling method is not particularly limited and can be any well-known method. Examples include: peeling by mechanical impact, peeling by applying heat and utilizing thermal stress, peeling by applying vibration such as ultrasound, peeling by etching, laser lift-off, etc. The oxide semiconductor film can be obtained in the form of a self-supporting film through this peeling.

[0129] (electrode)

[0130] Regarding the formation of electrodes required for constructing semiconductor devices, conventional methods can be used. That is, in addition to evaporation, sputtering, CVD, and plating, any method such as printing that bonds with resin can be used. Regarding electrode materials, in addition to metals such as Al, Ag, Ti, Pd, Au, Cu, Cr, Fe, W, Ta, Nb, Mn, Mo, Hf, Co, Zr, Sn, Pt, V, Ni, Ir, Zn, In, and Nd, any conductive film of metal oxides such as tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), and indium zinc oxide (IZO), or any organic conductive compound such as polyaniline, polythiophene, or polypyrrole, or alloys or mixtures of two or more of these can be used. The electrode thickness is preferably 1 nm to 1000 nm, more preferably 10 nm to 500 nm.

[0131] [Film-forming system]

[0132] Next, the film-forming system of the present invention will be described. The present invention is a film-forming system that forms a film by heat-treating an atomized raw material solution, and includes: a mechanism for atomizing or dropletizing the raw material solution to generate mist; a mechanism for conveying the mist to a film-forming section using a carrier gas; and a mechanism for supplying the mist from a nozzle to a substrate in the film-forming section, and performing heat treatment on the substrate to form a film, wherein the area of ​​the opening surface of the nozzle is set to S [cm²]. 2 Let H[cm] be the longest distance between a point in the opening and the surface of the substrate, and let Q[L / min] be the flow rate of the carrier gas supplied from the nozzle, then let SH / Q≧0.015.

[0133] (The mechanism that generates fog)

[0134] First, the raw material solution 104a is atomized or dropletized to generate a mist. This can be performed using an atomizing section 120 as described above. Here, the raw material solution (aqueous solution) 104a is not particularly limited as long as it contains an atomizable material; it can be an inorganic or organic material. Regarding the raw material solution, a solution of metal or metal compound can be suitable, and a solution containing one or more metals selected from gallium, iron, indium, aluminum, vanadium, titanium, chromium, rhodium, nickel, and cobalt can be used. Among these, gallium is particularly preferred, as it can form a gallium-containing film with good smoothness and suppression of pits.

[0135] Regarding the raw material solution, there are no particular limitations as long as it can atomize the solution of the metal (compound). Suitable raw material solutions may be those obtained by dissolving or dispersing the metal in an organic solvent or water in the form of a complex or salt. Examples of complex forms include: acetylacetonate complexes, carbonyl complexes, ammonia complexes, hydride complexes, etc. Examples of salt forms include: metal chloride salts, metal bromide salts, metal iodide salts, etc. Furthermore, solutions obtained by dissolving the metal in hydrobromic acid, hydrochloric acid, hydroiodic acid, etc., can also be used as aqueous solutions of the salt. The solute concentration is preferably 0.01 mol / L to 1 mol / L. Among these, the presence of halogens is particularly preferred, as it can form a film with better smoothness by further suppressing pits.

[0136] Furthermore, the raw material solution may also contain additives such as hydrohalic acids or oxidizing agents. 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; hypochlorous acid (HClO), perchloric acid, nitric acid, and ozone water; and organic peroxides such as peracetic acid or nitrobenzene.

[0137] Furthermore, the raw material solution may also contain dopants. The dopants are not particularly limited. Examples include n-type dopants such as tin, germanium, silicon, titanium, zirconium, vanadium, or niobium; or p-type dopants such as copper, silver, tin, iridium, or rhodium. The concentration of the dopant may, for example, be approximately 1.0 × 10⁻⁶. -9 mol / L to 1.0 mol / L, can be set to approximately 1.0 × 10⁻⁶. -7 Low concentrations below mol / L can also be set as high concentrations above approximately 0.01 mol / L.

[0138] (The organization that transports fog)

[0139] Next, the generated mist is transported to the film-forming section using a carrier gas. This can be performed using a transport section 109 as described above. The type of carrier gas is not particularly limited and can be appropriately selected depending on the film-forming material. Examples include inert gases such as oxygen, ozone, nitrogen, or argon, or reducing gases such as hydrogen or foaming gases. Furthermore, the type of carrier gas can be one or more. For example, a diluent gas obtained by diluting the same gas as the first carrier gas with another gas (e.g., diluting it 10 times) can be used as a second carrier gas; air can also be used.

[0140] In this invention, the carrier gas flow rate Q [L / min] represents the total flow rate of the carrier gas. For example, when a dilution carrier gas is used in addition to the carrier gas, the total flow rate of the carrier gas and the dilution carrier gas is set as Q. Furthermore, Q is set as the measured value at 20°C. When the measurement is performed at other temperatures or when measuring different types of flow rates (mass flow rate, etc.), the volumetric flow rate at 20°C can be converted using the gas equation of state.

[0141] Furthermore, the flow rate of the carrier gas (total flow rate in the case of using multiple gases) is not particularly limited as long as the conditions described later are met. For example, when forming a film on a substrate with a diameter of 4 inches (100 mm), it is preferably set to 1 L / min to 80 L / min, and more preferably to 4 L / min to 40 L / min.

[0142] (The mechanism for film formation)

[0143] Next, the mist is supplied from the nozzle onto the substrate in the film-forming section 140, and a film is formed by heat treatment on the substrate. Here, the area of ​​the nozzle opening surface 152 is set to S [cm]. 2 When the flow rate of the carrier gas is set to Q [L / min], and the longest distance between a point within the nozzle opening surface 152 and the surface of the substrate 110 is set to H [cm], it is acceptable for SH / Q to be 0.015 or higher, preferably 0.1 or higher and 20 or lower. If SH / Q is less than 0.015, the film will have many pits and poor surface smoothness. Moreover, the velocity of the carrier gas in the direction orthogonal to the substrate from the nozzle opening surface 152 should preferably be 0.01 m / s or higher and less than 8.0 m / s, preferably 0.1 m / s or higher and less than 2.5 m / s.

[0144] Furthermore, the area S of the nozzle opening surface 152 should preferably be 0.1 cm². 2 Above and less than 400 cm 2 The shortest distance H between the nozzle opening surface 152 and the substrate 110 is preferably 0.1 cm or more and 6.0 cm or less, more preferably 0.2 cm or more and 3.0 cm or less.

[0145] Let the area of ​​the nozzle opening surface 152 be S[cm] 2 Let the area of ​​the substrate be A[cm]. 2 When the S / A ratio is less than or equal to 0.3, it is preferable to have a ratio of 0.004 to 0.15. If S / A is less than or equal to 0.3, the resulting film has fewer pits and a smoother surface. Furthermore, the substrate area A is preferably 10 cm². 2 In the case of a circular substrate, a diameter of 2 inches (50 mm) or more is preferred. This is because a film with good surface smoothness can be formed over a larger area. Moreover, there is no particular upper limit to A. The larger the area of ​​the substrate, the larger the area of ​​the film can be obtained in a single deposition process, thus making it suitable for mass production.

[0146] Regarding the nozzle, a rectangular nozzle with a rectangular opening is preferred. When the length of the major axis of the nozzle opening 152 is defined as L [cm], and the maximum length of the nozzle along its major axis on the substrate is defined as R [cm], it is preferable that L / R ≥ 1. If L / R ≥ 1, a smooth film can be easily formed on a large-area substrate. Here, the major axis refers to the long side of the rectangle. There is no particular upper limit to L / R, but the larger L / R is, the more mist is not supplied to the substrate; therefore, it is preferable to set it to 3 or less.

[0147] Regarding heat treatment, any reaction can be achieved by heating, and the reaction conditions are not particularly limited. The temperature can be appropriately set according to the raw material or the film-forming material. For example, the heating temperature is in the range of 120°C to 600°C, preferably in the range of 200°C to 600°C, and more preferably in the range of 300°C to 550°C. The heating temperature is set to T [°C], and the area of ​​the nozzle opening surface 152 is set to S [cm²]. 2 When the carrier gas flow rate is set to Q [L / min], ST / Q is preferably 40 or more, more preferably 100 or more and 2000 or less. If ST / Q ≥ 40, a membrane with fewer pits and better surface smoothness is obtained.

[0148] Heat treatment can be carried out under any environment, including vacuum, oxygen-free environment, reducing gas environment, air environment, and oxygen environment, as long as the setting is appropriate according to the film-forming material. Moreover, the reaction pressure can be carried out under atmospheric pressure, pressurized conditions, or depressurized conditions. If film formation is carried out under atmospheric pressure, the apparatus structure can be simplified, which is therefore preferred.

[0149] The substrate 110 is not particularly limited as long as it can form a film and support the film. The material of the substrate 110 is also not particularly limited; well-known substrates can be used, and it can be an organic compound or an inorganic compound. Examples include: polysulfone, polyethersulfone, polyphenylene sulfide, polyetheretherketone, polyimide, polyetherimide, fluoropolymer, iron or aluminum, stainless steel, gold and other metals, silicon, sapphire, quartz, glass, gallium oxide, lithium niobate, lithium tantalate, etc., but are not limited to these. The thickness of the substrate is not particularly limited, but is preferably 10 μm to 2000 μm, more preferably 50 μm to 800 μm.

[0150] Film formation can be performed directly on the substrate or stacked on an intermediate layer formed on the substrate. The intermediate layer is not particularly limited; for example, an oxide comprising any one of aluminum, titanium, vanadium, chromium, iron, gallium, rhodium, indium, or iridium can be used as the main component. More specifically, it can be Al₂O₃, Ti₂O₃, V₂O₃, Cr₂O₃, Fe₂O₃, Ga₂O₃, Rh₂O₃, In₂O₃, or Ir₂O₃. Furthermore, when two elements selected from the aforementioned metallic elements are designated as A and B, it can be designated as (A...). x B 1-x The binary metal oxide represented by )2O3 (0 < x < 1), or, when three elements selected from the metal elements are designated as A, B, and C, it can be designated as (A x B y C 1-x-y The ternary metal oxides represented by )2O3 (0 < x < 1, 0 < y < 1, 0 < x + y < 1).

[0151] In this invention, annealing can also be performed after film formation. The annealing temperature is not particularly limited, but is preferably below 600°C, more preferably below 550°C. This is because it does not damage the crystallinity of the film. The annealing time is not particularly limited, but is preferably from 10 seconds to 10 hours, more preferably from 10 seconds to 1 hour.

[0152] (Stripping)

[0153] The substrate 110 can also be peeled off from the oxide semiconductor film. The peeling method is not particularly limited and can be any well-known method. Examples include: peeling by mechanical impact, peeling by applying heat and utilizing thermal stress, peeling by applying vibration such as ultrasound, peeling by etching, laser peeling, etc. The oxide semiconductor film can be obtained in the form of a self-supporting film through this peeling.

[0154] (electrode)

[0155] Regarding the formation of electrodes required for constructing semiconductor devices, conventional methods can be used. That is, in addition to evaporation, sputtering, CVD, and plating, any method such as printing that bonds the electrodes with resin can be used. Regarding electrode materials, in addition to metals such as Al, Ag, Ti, Pd, Au, Cu, Cr, Fe, W, Ta, Nb, Mn, Mo, Hf, Co, Zr, Sn, Pt, V, Ni, Ir, Zn, In, and Nd, any metal oxide conductive film such as tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), or zinc indium oxide (IZO), or any organic conductive compound such as polyaniline, polythiophene, or polypyrrole, or alloys or mixtures of two or more of these, can be used. The electrode thickness is preferably 1 nm to 1000 nm, more preferably 10 nm to 500 nm.

[0156] Example

[0157] The present invention will now be specifically described using examples and comparative examples, but the present invention is not limited to these examples.

[0158] (Example 1)

[0159] In this embodiment, using Figure 1 A film-forming device as shown.

[0160] A 0.05 mol / L gallium iodide aqueous solution was prepared by mixing tin chloride with gallium in an atomic ratio of 1:0.08, and this solution was used as raw material solution 104a. The raw material solution 104a obtained in this manner was then contained within a fog generation source 104. The temperature of the solution at this time was 25°C.

[0161] Next, a 4-inch (100 mm in diameter) c-side sapphire substrate, which serves as substrate 110, is placed in a film-forming chamber 107 on a heating plate 108, and the heating plate 108 is activated to raise the temperature to 500°C.

[0162] Next, flow regulating valves 103a and 103b are opened to supply nitrogen gas, which is used as carrier gas, into the film-forming chamber 107 from carrier gas sources 102a and 102b. The environment of the film-forming chamber 107 is fully replaced by the carrier gas, and the flow rate of the main carrier gas and the flow rate of the dilution carrier gas are adjusted to 12 L / min.

[0163] Next, the ultrasonic transducer 106 is vibrated at 2.4 MHz, and this vibration is transmitted through water 105a to the raw material solution 104a, thereby atomizing the raw material solution 104a to generate mist.

[0164] The mist is supplied to the substrate 110 via a carrier gas through a supply pipe 109a and a nozzle 150. Regarding the nozzle 150, a nozzle with a rectangular opening surface 152 is used, and the area of ​​the opening surface 152 is set to S [cm²]. 2 When the flow rate of the carrier gas is set to Q [L / min], and the longest distance between a point within the nozzle opening 152 and the surface of the substrate 110 is set to H [cm], the adjustment is made so that SH / Q = 0.5. At this time, S = 6.0, H = 2.0, and Q = 24.

[0165] Next, the fog was heat-treated in the film-forming chamber 107 under atmospheric pressure and 500°C to form a thin film of gallium oxide (α-Ga2O3) with a corundum structure on the substrate 110. The film-forming time was set to 30 minutes.

[0166] When the heat treatment temperature is set to T [°C], ST / Q = 40, and the substrate area is set to A [cm²]... 2 When the length of the nozzle opening surface 152 is set to L [cm], and the maximum length of the nozzle in the long axis direction of the substrate is set to R [cm], the length of the nozzle opening surface 152 is L / R = 1.2. At this time, the values ​​are T = 500, A = 78.5, L = 12, and R = 10.

[0167] Regarding the substrate, utilizing Figure 10 Such a moving mechanism allows the substrate and heating plate to move back and forth at a speed of 15 cm / min, passing under the nozzle once per minute.

[0168] Next, on the n+ semiconductor film obtained as described, an n- semiconductor film is laminated as a second layer using the same raw material solution except that it does not contain tin chloride, under the same conditions.

[0169] (Example 2)

[0170] In addition to changing the area S of the nozzle opening to 10.8 cm² 2 The total flow rate of the carrier gas was changed to 40 L / min, and the film formation temperature T was changed to 550°C. Film formation was carried out in the same manner as in Example 1. At this time, SH / Q = 0.54, ST / Q = 149, and S / A = 0.15.

[0171] (Example 3)

[0172] Except for changing the total carrier gas flow rate to 20 L / min and the film formation temperature T to 500°C, film formation was performed in the same manner as in Example 2. At this time, SH / Q = 1.08, ST / Q = 270, and S / A = 0.15.

[0173] (Example 4)

[0174] Except for changing the film-forming temperature T to 500°C, film formation was performed in the same manner as in Example 2. At this time, SH / Q = 0.54, ST / Q = 135, and S / A = 0.15.

[0175] (Example 5)

[0176] In addition to changing the concentration of the raw material solution to 0.3 mol / L, the area S of the nozzle opening was changed to 1.2 cm². 2 The longest distance H between the point within the nozzle opening 152 and the surface of the substrate 110 was set to 2.5 cm, and the total flow rate of the carrier gas was changed to a total of 14 L / min. Film formation was performed in the same manner as in Example 1. At this time, SH / Q = 0.21, ST / Q = 42.9, and S / A = 0.015.

[0177] (Example 6)

[0178] The raw material solution was set to a 0.3 mol / L gallium bromide aqueous solution. The longest distance H between the point within the nozzle opening 152 and the surface of the substrate 110 was changed to 1.6 cm. Otherwise, film formation was performed in the same manner as in Example 5. At this time, SH / Q = 0.14, ST / Q = 42.9, and S / A = 0.015.

[0179] (Example 7)

[0180] Using a 6-inch (150 mm diameter) sapphire substrate as substrate 110, the area S of the nozzle opening surface was changed to 8.5 cm². 2 The longest distance H between the point within the nozzle opening 152 and the surface of the substrate 110 was changed to 0.2 cm, and the total flow rate of the carrier gas was changed to a total of 36 L / min. Otherwise, film formation was performed in the same manner as in Example 1. At this time, SH / Q = 0.047, ST / Q = 118, S / A = 0.048, and L / R = 1.1.

[0181] (Example 8)

[0182] Using a 0.05 mol / L aqueous solution obtained by dissolving gallium acetylacetonate complex in water containing 1.5 vol% hydrochloric acid as the raw material solution, the area S of the nozzle opening was changed to 1.2 cm². 2The longest distance H between the point within the nozzle opening 152 and the surface of the substrate 110 was changed to 0.2 cm, the total flow rate of the carrier gas was changed to a total of 10 L / min, and the film formation temperature T was changed to 450°C. Otherwise, film formation was performed in the same manner as in Example 1. At this time, SH / Q = 0.024, ST / Q = 54, and S / A = 0.015.

[0183] (Example 9)

[0184] Except that the longest distance H between the point within the nozzle opening 152 and the surface of the substrate 110 is changed to 1.2 cm, film formation is performed in the same manner as in Example 6. In this case, SH / Q = 0.1, ST / Q = 42.9, and S / A = 0.015.

[0185] (Example 10)

[0186] In addition to changing the area S of the nozzle opening to 24 cm² 2 The longest distance H between the point within the nozzle opening 152 and the surface of the substrate 110 was changed to 0.2 cm, the total flow rate of the carrier gas was changed to a total of 80 L / min, and the film formation temperature T was changed to something other than 550°C. Film formation was then performed in the same manner as in Example 1. At this time, SH / Q = 0.06, ST / Q = 165, and S / A = 0.30.

[0187] (Example 11)

[0188] The area S of the nozzle opening is set to 5.0 cm². 2 The longest distance H between the point within the nozzle opening 152 and the surface of the substrate 110 was set to 0.2 cm, and the total flow rate of the carrier gas was set to 60 L / min. Film formation was performed in the same manner as in Example 1. At this time, SH / Q = 0.017, ST / Q = 41.7, S / A = 0.064, and L / R = 1.0.

[0189] (Example 12)

[0190] The nozzle opening was shaped as a circle with a diameter of 4 inches (100 mm). The longest distance H between a point within the nozzle opening 152 and the surface of the substrate 110 was changed to 0.2 cm. Without moving the substrate, the carrier gas flow rate was changed to a total of 80 L / min, and the heating temperature was set to 550°C. Otherwise, film formation was performed in the same manner as in Example 1. At this time, SH / Q = 0.20, ST / Q = 540, S / A = 1, and L / R = 1.

[0191] (Example 13)

[0192] The raw material solution was set as a 0.05 mol / L gallium bromide aqueous solution, and deuterbromic acid was added at a volume ratio of 10%. The longest distance H between the point within the nozzle opening 152 and the surface of the substrate 110 was changed to 0.2 cm, and the film formation temperature T was changed to 470°C. Otherwise, film formation was performed in the same manner as in Example 6. At this time, SH / Q = 0.017, ST / Q = 40, and S / A = 0.015.

[0193] (Example 14)

[0194] The raw material solution was set to a 0.05 mol / L gallium iodide aqueous solution. The longest distance H between the point within the nozzle opening 152 and the surface of the substrate 110 was changed to 0.2 cm. The total flow rate of the carrier gas was changed to a total of 16 L / min. The film deposition temperature T was changed to 450°C. Otherwise, film deposition was performed in the same manner as in Example 6. At this time, SH / Q = 0.015, ST / Q = 33.8, and S / A = 0.015.

[0195] (Comparative Example 1)

[0196] Except that the total carrier gas flow rate was changed to a total of 20 L / min, film formation was performed in the same manner as in Example 14. At this time, SH / Q = 0.012, ST / Q = 27, and S / A = 0.015.

[0197] (Comparative Example 2)

[0198] Except that the total carrier gas flow rate was changed to a total of 24 L / min, film formation was performed in the same manner as in Example 14. At this time, SH / Q = 0.01, ST / Q = 22.5, and S / A = 0.015.

[0199] (Comparative Example 3)

[0200] Except that the total carrier gas flow rate was changed to a total of 48 L / min, film formation was performed in the same manner as in Example 14. At this time, SH / Q = 0.005, ST / Q = 11.3, and S / A = 0.015.

[0201] (Comparative Example 4)

[0202] Except that the total carrier gas flow rate was changed to a total of 60 L / min, film formation was performed in the same manner as in Example 14. At this time, SH / Q = 0.004, ST / Q = 9, and S / A = 0.015.

[0203] (Experimental Example 1)

[0204] The surface of the film after deposition was observed using an optical microscope, focusing on areas at 0.01 cm. 2 ~1 cm 2The number of pits within the area was counted. The pit count was divided by the observed area, and the resulting pit density is shown in Table 1. Furthermore, the pit density relative to SH / Q is plotted and presented in... Figure 12 .

[0205] (Experimental Example 2)

[0206] Using the semiconductor film obtained as described, fabrication Figure 13 Such a semiconductor device 170.

[0207] <Formation of Schottky Electrodes>

[0208] A Schottky electrode 172 is formed by depositing a Pt layer, a Ti layer and an Au layer on an n-type semiconductor layer 171a by electron beam evaporation.

[0209] <Formation of Ohmic Electrodes>

[0210] An ohmic electrode 173 is formed by electron beam evaporation to deposit a Ti layer and an Au layer on the n+ type semiconductor layer 171b.

[0211] <Evaluation>

[0212] The current-voltage characteristics of the obtained semiconductor devices were evaluated. The voltage at which insulation breakdown occurs was investigated by measuring the current-voltage characteristics in the reverse direction. Semiconductor devices with a withstand voltage of 300 V or higher were considered acceptable. The yield rate was calculated as the number of acceptable devices / total number of semiconductor devices manufactured. The results are shown in Table 1.

[0213] Furthermore, a graph showing the yield obtained by plotting the pit density relative to that calculated in Experimental Example 1 is shown in [the figure]. Figure 14 .

[0214] [Table 1]

[0215]

[0216] A comparison of Examples 1 to 14 with Comparative Examples 1 to 4 reveals that when the area of ​​the nozzle opening surface is set to S [cm²], 2 When the longest distance between a point in the opening and the surface of the substrate is set as H [cm], and the flow rate of the gas supplied from the nozzle is set as Q [L / min], a film is formed by using a film formation method with SH / Q≧0.015, thereby creating a film that suppresses pits and has excellent smoothness, and can produce high-voltage semiconductor devices with excellent yield.

[0217] Furthermore, this invention is not limited to the described embodiments. The described embodiments are illustrative, and any embodiments having a structure that is substantially the same as the technical concept described in the claims of this invention and achieving the same effect are included within the technical scope of this invention.

Claims

1. A film-forming method, comprising heat-treating an atomized raw material solution to form a film, characterized in that... Include: The process of atomizing or dropletizing the raw material solution to generate a mist; The process of transporting the mist to the film-forming section using a carrier gas; and In the film-forming section, the mist is supplied from a nozzle to the substrate, and a film-forming process is performed by heat treatment on the substrate. Let the area of ​​the nozzle opening be S[cm] 2 Let H [cm] be the longest distance between a point within the opening and the surface of the substrate, and let Q [L / min] be the flow rate of the carrier gas supplied from the nozzle. Then, let SH / Q ≥ 0.

015. When the temperature of the heat treatment is set to T [°C], ST / Q is set to 33.

8.

2. The film-forming method according to claim 1, characterized in that, The raw material solution contains gallium.

3. The film-forming method according to claim 1, characterized in that, The raw material solution contains halogens.

4. The film-forming method according to claim 2, characterized in that, The raw material solution contains halogens.

5. The film-forming method according to claim 1, characterized in that, When the temperature of the heat treatment is set to T [°C], it is set to ST / Q≧40.

6. The film-forming method according to claim 2, characterized in that, When the temperature of the heat treatment is set to T [°C], it is set to ST / Q≧40.

7. The film-forming method according to claim 3, characterized in that, When the temperature of the heat treatment is set to T [°C], it is set to ST / Q≧40.

8. The film-forming method according to claim 4, characterized in that, When the temperature of the heat treatment is set to T [°C], it is set to ST / Q≧40.

9. The film-forming method according to any one of claims 1 to 8, characterized in that, The mist is supplied to the substrate using the nozzle located vertically above the substrate.

10. The film-forming method according to claim 9, characterized in that, The substrate is moved below the nozzle.

11. The film-forming method according to claim 10, characterized in that, Let the area of ​​the surface of the substrate to be film-formed be A[cm]. 2 When ], set S / A≦0.

3.

12. The film-forming method according to any one of claims 1 to 8, characterized in that, The nozzle has a rectangular opening.

13. The film-forming method according to claim 12, characterized in that, When the length of the major axis of the nozzle opening is set to L[cm], and the maximum length of the nozzle in the major axis direction within the surface of the substrate to be film-formed is set to R[cm], L / R≧1 is set.

14. The film-forming method according to any one of claims 1 to 8, characterized in that, The area of ​​the substrate is 10 cm². 2 above.

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