Film forming method, film forming apparatus, susceptor, and alpha-gallium oxide film

Abstract

The present invention is a film forming method characterized by comprising the steps of: atomizing a raw material solution to form a raw material mist; mixing the raw material mist with a carrier gas to form a mixed gas; a step of placing the substrate on a placement portion of the susceptor; a step in which the mixed gas is supplied from an atomizing means to the substrate and a film is formed on the substrate by a thermal reaction; and a step for discharging the mixed gas after film formation by means of an exhaust means. In the step of supplying the mixed gas from an atomizing means to the substrate and forming a film on the substrate by a thermal reaction, at least a portion of the mixed gas is supplied to the surface of the substrate from a smooth portion adjacent to the placement portion and having a surface roughness of 200 [mu] m or less. As a result, provided is a film formation method capable of uniformly and stably producing a high-quality film on the surface of a large-diameter substrate.

Description

Technical Field

[0001] The invention relates to a film forming method, a film forming device, a susceptor and an alpha-gallium oxide film. Background Art

[0002] As a method capable of forming an epitaxial film or the like at a low temperature and under atmospheric pressure, a film forming method using water particles such as a mist CVD method is known. Patent Document 1 discloses an apparatus for performing film formation by obliquely placing a substrate placed on a substantially semicircular susceptor in a horizontal furnace. Patent Document 2 discloses a film forming apparatus that forms a film by horizontally supplying a raw material mist to a substrate fixed to a flat flow channel called a micro flow channel. Patent Document 3 discloses a film forming apparatus in which a film forming nozzle including a raw material solution ejecting section and an exhaust section is arranged to face a film forming surface of a substrate, and a film is formed while being moved parallel to the substrate. In addition, Patent Document 4 discloses a film forming method in which a raw material mist is transported into a reaction container by using a carrier gas and further a swirl flow is generated to cause the mist to react with a substrate. Prior art literature Patent Literature

[0003] Patent Document 1: Japanese Patent Application Publication No. 2016-27636 Patent Document 2: Japanese Patent Application Publication No. 2013-28480 Patent Document 3: International Publication No. 2016 / 051559 Patent Document 4: Japanese Patent Application Publication No. 2016-146442 Summary of the invention Problems to be solved by the invention

[0004] However, these conventional film-forming devices have problems such as significant generation and adhesion of powder, introduction of a large number of defects in the film, and generation of turbidity due to abnormal film growth.

[0005] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a film forming method, a film forming apparatus, and a susceptor capable of uniformly and stably forming a high-quality film on the surface of a large-diameter substrate. Another object of the present invention is to provide an α-gallium oxide film having higher quality than before. Means of solving problems

[0006] The present invention is made to achieve the above-mentioned purpose and provides a film forming method, characterized in that it includes the following steps: atomizing a raw material solution to form a raw material mist; mixing the raw material mist with a carrier gas to form a mixed gas; placing a substrate on a carrying portion of a base; supplying the mixed gas to the substrate from an atomizing means and forming a film on the substrate through a thermal reaction; and exhausting the mixed gas after film formation through an exhaust means; in the step of supplying the mixed gas to the substrate from an atomizing means and forming a film on the substrate through a thermal reaction, at least a portion of the mixed gas is supplied to the surface of the substrate from a smooth portion adjacent to the carrying portion and having a surface roughness of less than 200 μm.

[0007] According to such a film forming method, a high-quality film can be uniformly and stably manufactured on the surface of a large-diameter substrate. Specifically, according to such a film forming method, since the mixed gas containing the raw material mist is supplied to the substrate in a laminar flow state, the generation and abnormal growth of powder can be suppressed, and thus a high-quality film can be stably manufactured on the surface of a large-diameter substrate.

[0008] In this case, the surface roughness can be set to 150 μm or less.

[0009] This makes it possible to produce a higher quality film more uniformly and stably.

[0010] At this time, the height difference between the surface of the smooth portion and the surface of the substrate placed on the placement portion can be set to be greater than or equal to -1 mm and less than or equal to +1 mm.

[0011] This makes it possible to maintain the mixed gas in a more stable laminar flow, and to stably and uniformly manufacture a high-quality film.

[0012] At this time, the angle formed by the surface of the smooth portion and the direction in which the mixed gas flows into the smooth portion can be set to be greater than or equal to 0° and less than or equal to 60°.

[0013] This makes it possible to effectively suppress the generation of powder, and further, to more stably produce a high-quality film.

[0014] The present invention is made to achieve the above-mentioned purpose, and provides a film forming device, characterized in that it comprises: a carrier gas supplying means for supplying a carrier gas; an atomizing means for atomizing a raw material solution to generate a raw material mist; a film forming section for supplying a mixed gas of the raw material mist and the carrier gas to a substrate for film formation; and a heating means for heating the substrate; the film forming section has a base, the base has a mounting portion for mounting the substrate, the base has a smooth portion adjacent to the mounting portion, at least a portion of the mixed gas flows through the smooth portion, and the surface roughness of the smooth portion is less than 200μm.

[0015] According to such a film forming apparatus, a high-quality film can be uniformly and stably manufactured on the surface of a large-diameter substrate. Specifically, according to such a film forming apparatus, since the mixed gas containing the raw material mist is supplied to the substrate in a laminar flow state, the generation and abnormal growth of powder can be suppressed, thereby stably manufacturing a high-quality film on the surface of a large-diameter substrate.

[0016] In this case, the surface roughness can be set to 150 μm or less.

[0017] This makes it possible to produce a higher quality film more uniformly and stably.

[0018] At this time, the height difference between the surface of the smooth portion and the surface of the substrate placed on the placement portion can be set to be greater than or equal to -1 mm and less than or equal to +1 mm.

[0019] This allows the mixed gas to maintain a more stable laminar flow, thereby enabling a high-quality film to be manufactured stably and uniformly.

[0020] At this time, the angle formed by the surface of the smooth portion and the direction in which the mixed gas flows into the smooth portion can be set to be greater than or equal to 0° and less than or equal to 60°.

[0021] This makes it possible to effectively suppress the generation of powder, and further, to more stably produce a high-quality film.

[0022] The present invention is made to achieve the above-mentioned purpose, and provides a susceptor, characterized in that the susceptor has a loading portion for loading the substrate in a film forming device, and the film forming device has: a carrier gas supplying means for supplying a carrier gas; an atomizing means for atomizing a raw material solution to generate a raw material mist; a film forming portion for supplying a mixed gas of the raw material mist and the carrier gas to the substrate for film formation; and a heating means for heating the substrate, and the susceptor has a smooth portion adjacent to the loading portion, and at least a portion of the mixed gas flows through the smooth portion, and the surface roughness of the smooth portion is less than 200μm.

[0023] According to such a susceptor, a high-quality film can be uniformly and stably manufactured on the surface of a large-diameter substrate. Specifically, according to such a susceptor, since the mixed gas containing the raw material mist is supplied to the substrate in a state of maintaining a laminar flow, the generation and abnormal growth of powder can be suppressed, thereby stably manufacturing a high-quality film on the surface of a large-diameter substrate.

[0024] In this case, the surface roughness can be set to 150 μm or less.

[0025] This makes it possible to produce a higher quality film more uniformly and stably.

[0026] In this case, the surface roughness of the smooth portion is 200 μm or less, and the height difference between the surface of the smooth portion and the surface of the substrate mounted on the mounting portion can be set to be greater than or equal to −1 mm and less than or equal to +1 mm.

[0027] This makes it possible to produce a higher quality film more uniformly and stably.

[0028] The present invention is made to achieve the above-mentioned purpose and provides an α-gallium oxide film, characterized in that it is formed on substantially the entire surface of a c-plane sapphire substrate with a diameter of more than 4 inches, the half-width of the rocking curve of the (0006) plane X-ray diffraction peak of the α-gallium oxide film is less than 9.5 seconds, and the film thickness distribution is less than ±9%.

[0029] As a result, a high-quality α-gallium oxide film with good crystal orientation and good film thickness distribution is obtained.

[0030] The present invention is made to achieve the above-mentioned object and provides an α-gallium oxide film, characterized in that it is formed on substantially the entire surface of a c-plane sapphire substrate having a diameter of 4 inches or more and a foreign matter density of 1.1 cm -2 Below, and the film thickness distribution is below ±9%.

[0031] As a result, a high-quality α-gallium oxide film with low foreign matter density and good film thickness distribution can be obtained. Effects of the Invention

[0032] As described above, according to the film forming method of the present invention, a high-quality film can be stably produced, and film formation can be performed with high productivity. According to the film forming apparatus and the susceptor of the present invention, a high-quality film can be stably manufactured, and film formation with high productivity can be performed. As described above, the α-gallium oxide film according to the present invention has higher quality than ever before. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a diagram showing one embodiment of a film forming apparatus according to the present invention. Figure 2 This is a diagram showing one embodiment of a susceptor of a film forming apparatus according to the present invention. Figure 3 (a) is a diagram showing another embodiment of the base of the film forming apparatus according to the present invention, Figure 3 (b) is a diagram showing still another form of the base. Figure 4 This is a diagram showing still another embodiment of the susceptor of the film forming apparatus according to the present invention. Figure 5 This is a diagram showing still another embodiment of the susceptor of the film forming apparatus according to the present invention. Figure 6 This is a diagram showing one mode of flow of a mixed gas toward a substrate placed on a susceptor of a film forming apparatus according to the present invention. Figure 7 Examples of various irregularities associated with abnormal growth on the film surface observed when turbidity is observed under a microscope are shown. Figure 8 Another example of various irregularities associated with abnormal growth on the film surface observed when turbidity is observed under a microscope is shown. DETAILED DESCRIPTION

[0034] The present invention will be described in detail below, but the present invention is not limited thereto.

[0035] As described above, there is a need for a film forming method, a film forming apparatus, and a susceptor that can uniformly and stably produce a high-quality film on a large-diameter substrate surface.

[0036] The inventors have conducted repeated and in-depth studies on the above-mentioned problems, and as a result, found that high-quality films can be stably manufactured and high-productivity films can be formed by the film forming method, film forming device and base described below, thereby completing the present invention: the film forming method comprises: a step of atomizing a raw material solution to form a raw material mist; a step of mixing the raw material mist with a carrier gas to form a mixed gas; a step of placing a substrate on a holding portion of a holding portion of a holding portion; a step of supplying the mixed gas to the substrate from an atomizing means and forming a film on the substrate through a thermal reaction; a step of exhausting the mixed gas after film formation by an exhaust means; characterized in that, in the step of supplying the mixed gas to the substrate from an atomizing means and forming a film on the substrate through a thermal reaction, at least a portion of the mixed gas is supplied to the surface of the substrate from a smooth portion adjacent to the holding portion and having a surface roughness of less than 200 μm. The film forming device comprises: a carrier gas supplying means for supplying a carrier gas; an atomizing means for atomizing a raw material solution to generate a raw material mist; a film forming section for supplying a mixed gas of the raw material mist and the carrier gas to a substrate for film formation; and a heating means for heating the substrate; and is characterized in that the film forming section has a base, the base has a mounting portion for mounting the substrate, the base has a smooth portion adjacent to the mounting portion, at least a portion of the mixed gas flows through the smooth portion, and the surface roughness of the smooth portion is less than 200 μm. The base has a loading portion for loading the substrate on a film forming device, and the film forming device comprises: a carrier gas supplying means for supplying a carrier gas; an atomizing means for atomizing a raw material solution to generate a raw material mist; a film forming portion for supplying a mixed gas of the raw material mist and the carrier gas to the substrate for film formation; and a heating means for heating the substrate; and is characterized in that it has a smooth portion adjacent to the loading portion, at least a portion of the mixed gas flows through the smooth portion, and the surface roughness of the smooth portion is less than 200 μm.

[0037] In addition, as described above, a higher quality α-gallium oxide film than ever before is required.

[0038] The inventors have repeatedly conducted in-depth studies on the above-mentioned problems and found that an α-gallium oxide film of higher quality than before can be provided by the α-gallium oxide film described below, thereby completing the present invention: the α-gallium oxide film is formed on substantially the entire surface of a c-plane sapphire substrate having a diameter of 4 inches or more, characterized in that the half width of the rocking curve of the (0006) plane X-ray diffraction peak of the α-gallium oxide film is less than 9.5 seconds and the film thickness distribution is less than ±9%, and the α-gallium oxide film is characterized in that the foreign matter density is 1.1 cm -2 The film thickness distribution is less than ±9%.

[0039] The present invention will be described in detail below with reference to the accompanying drawings, but the present invention is not limited thereto.

[0040] (First Embodiment) [Film forming device] First, one embodiment of the film forming apparatus according to the present invention will be described. Figure 1 One embodiment of the film forming apparatus according to the present invention is shown. However, the film forming apparatus according to the present invention is not limited to Figure 1 The film forming device shown.

[0041] like Figure 1 As shown, the film forming apparatus 1 according to the present invention comprises a mixed gas forming mechanism 50 , a film forming unit 30 , and an exhaust means 40 . The mixed gas forming mechanism 50 comprises a carrier gas supply means 10 and an atomizing means 20 .

[0042] The carrier gas supply means 10 and the atomizing means 20 are connected via a pipe 101 , and the carrier gas 111 is supplied from the carrier gas supply means 10 to the atomizing means 20 , where a mixed gas is formed. The atomizing means 20 and the film forming chamber 31 of the film forming unit 30 are connected via a pipe 102 , and the mixed gas 112 is supplied from the atomizing means 20 to the film forming chamber 31 of the film forming unit 30 . The film forming chamber 31 of the film forming unit 30 and the exhaust means 40 are connected via a duct 103 , and exhaust is discharged from the film forming chamber 31 of the film forming unit 30 to the exhaust means 40 .

[0043] It should be noted that there are no special restrictions on the pipe 102 as long as it has sufficient stability to the raw material solution 21 used or the temperature in the coordination between the film forming part 30 and the pipe 102. Depending on the purpose, the pipe can be made of resin, metal, glass, ceramic or a combination of these materials. There is no particular limitation on the pipelines 101 and 103 as long as they have sufficient stability.

[0044] (Carrier gas supply means 10) The carrier gas supplying means 10 supplies the carrier gas 111 to the atomizing means 20 . The carrier gas 111 is not particularly limited. For example, in addition to air, oxygen, and ozone, an inert gas such as nitrogen and argon, or a reducing gas such as hydrogen and synthetic gas is preferably used. The type of the carrier gas 111 can be one or more than one. The flow rate of the carrier gas 111 can be appropriately set according to the size of the substrate 33 and the size of the film forming unit 30, for example, it can be set to about 0.01 to 100 L / min.

[0045] Although not shown, the ratio of the raw material mist 22 to the carrier gas 111 can be adjusted by further adding a dilution gas. The flow rate of the dilution gas can be appropriately set, for example, it can be set to 0.1 to 10 times that of the carrier gas. The dilution gas can be supplied, for example, to the downstream side of the atomizing means 20. The dilution gas can be the same gas as the carrier gas 111, or a different gas can be used.

[0046] (Atomization means 20) A raw material solution 21 as a raw material is stored in the atomizing means 20. The raw material solution 21 is not particularly limited as long as it is a solution that can be atomized (also called "atomized"). Aqueous solutions containing raw materials according to the purpose and organic solvent solutions such as alcohols, ketones, esters, ethers, amides, halogenated solvents, and aromatic compounds can be used. The raw material solution 21 is atomized by known means to form raw material mist 22 .

[0047] The carrier gas 111 is supplied to the atomizing means 20 and mixed with the raw material mist 22 to form a mixed gas 112 .

[0048] The atomization of the raw material solution 21 is not particularly limited as long as the raw material solution 21 can be atomized or turned into droplets, and known means can be used, but in the present invention, ultrasound is preferably used. Since the initial velocity is zero and it floats in the air, it is preferred to use the mist or droplets obtained by ultrasound. For example, since it is not sprayed like a spray, but floats in the space, the mist can be transported as a gas, so it will not be damaged by collision energy, so it is very suitable. There is no particular limitation on the droplet size, and it can be a droplet of about several mm, but it is preferably less than 50 μm, and more preferably 0.1 to 10 μm.

[0049] The atomizing means 20 may include a temperature regulating unit (not shown) that can directly or indirectly regulate the temperature of the raw material solution 21, and may use a liquid or gas heat medium for heat exchange, or utilize the Peltier effect. As the heat medium, a wide range of known heat media can be used, and for example, liquid heat media such as water, glycols, alcohols, and silicone oils, and gas heat media such as air, helium, or fluorocarbons are preferably used.

[0050] (Film forming section 30) like Figure 1 As shown, the film forming unit 30 includes a film forming chamber 31 and a heating means 34 . A susceptor 32 having a triangular shape in side view is arranged in the film forming chamber 31 . A substrate 33 is placed on the inclined surface of the base 32 . A pipe 102 is connected to one wall of the film forming chamber 31 , and a pipe 103 is connected to the other wall thereof. The mixed gas 112 is transported and supplied to the film forming chamber 31 through the pipe 102 .

[0051] The film forming chamber 31 is not particularly limited as long as it has sufficient stability to the raw material solution 21 used or the operating temperature, and can be made of resin, metal, glass, ceramic or a combination of these materials depending on the purpose. The film formation may be performed under any conditions of atmospheric pressure, increased pressure, or reduced pressure, but is preferably performed under atmospheric pressure in view of the equipment cost and productivity.

[0052] Figure 2 One embodiment of a susceptor of the film forming apparatus according to the present invention is shown. Figure 2 One aspect of the susceptor is shown when the mixed gas 112 always flows in one direction (y direction) over the susceptor 32 . like Figure 2 As shown in FIG. 1 , the base 32 includes a circular placement portion 32 b at the center of the surface. The placement portion 32 b can place the substrate 33 thereon.

[0053] (Structure and material of the base) The structure, material, etc. of the base 32 are not particularly limited as long as they have sufficient stability according to the characteristics of the raw material solution 21 used and the temperature conditions. The structure of the susceptor 32 may include a mechanism (not shown) for holding the substrate 33. In this case, a known substrate holding method such as a vacuum chuck, a mechanical chuck, or an electrostatic chuck can be applied. As the material of the base 32, metals such as aluminum and stainless steel can be used. When film formation is carried out at a higher temperature than the heat-resistant temperature of these metals or when acidic or alkaline raw materials are used, alloys such as Hastelloy (registered trademark), soda-lime glass, borosilicate glass, quartz, silicon carbide, or ceramics such as silicon nitride and aluminum nitride can also be used.

[0054] The base 32 has a smooth portion 32a at the lower portion adjacent to the mounting portion 32b. The smooth portion 32a is provided upstream of the mounting portion 32b, that is, on the side where the mixed gas 112 flows into the base 32, and is provided adjacent to the mounting portion 32b. The smooth portion 32a has a smooth surface.

[0055] At least a portion of the mixed gas 112 flows through the smooth portion 32a. That is, a portion of the mixed gas 112 supplied to the film forming chamber 31 flows directly to the surface of the substrate 33 in a straight line, and another portion is supplied to the surface of the substrate 33 along the smooth portion 32a. In this process, the mixed gas 112 reacts on the substrate 33 and forms a film on the substrate 33.

[0056] The smooth portion 32a is preferably configured to include at least a region that is in contact with both ends of the mounting portion 32b (or the substrate (not shown)) in the x direction. Thus, the mixed gas 112 can be supplied to the substrate surface while always maintaining a laminar flow, thereby enabling stable and good crystal growth to be achieved on the substrate surface.

[0057] The surface roughness (arithmetic mean roughness) Ra_cor of the smooth portion 32a is set to 200 μm or less. Thus, the mixed gas 112 supplied to the surface of the substrate 33 along the smooth portion 32a can flow with less turbulence, thereby stably forming a uniform and high-quality film. If the surface roughness (arithmetic mean roughness) Ra_cor of the smooth portion 32a exceeds 200 μm, the mixed gas will become turbulent, causing significant particle adhesion, which may lead to turbid appearance due to abnormal growth. Turbidity is observed under a microscope as various concavities and convexities accompanying abnormal growth on the film surface, such as Figure 7 as well as Figure 8As shown. This abnormal growth is mostly caused by abnormal nucleation caused by foreign matter adhesion or deviation of film components. In addition, macroscopically, in general, its extent can be determined by visual inspection, but it can be quantified by measuring the reflectivity or transmittance of visible light, or measuring the surface unevenness, for example. These measurements can be widely applied to known methods, preferably using a general spectrophotometer, a stylus surface profiler or an atomic force microscope. In particular, when the film is transparent in the visible light range, it can be judged based on the mirror reflectivity of visible light incident on the film surface at a certain angle. Specifically, for example, in the case of gallium oxide, for example, under the conditions of an incident light wavelength of 633nm and an incident angle of 45°, the mirror reflectivity can be made less than 15%. It should be noted that the mirror reflectivity refers to the ratio of the energy of the incident light to the energy of the reflected light when the light is incident from the light source to the surface of the sample (film) and reflected, and is received by a light receiving probe located at the same reflection angle as the incident angle. It should be noted that the "particles" in the present invention include those that have penetrated into the film and become integrated with the film and those that adhere to the film surface as foreign matter, and refer to those that are observed as particles when observing the surface of the film and can be measured, for example, by light scattering. The surface roughness (arithmetic mean roughness) Ra_cor of the smooth portion 32a is preferably set to 150 μm or less. The lower limit is not particularly limited, and can be set to 0.1 nm, for example.

[0058] The surface roughness (arithmetic mean roughness) Ra is a value calculated based on JIS B 0601, using a stylus method, an atomic force microscope (AFM) method, or a non-contact measurement method using a laser microscope or a confocal microscope using an optical interferometer method, a confocal method, or an image synthesis method utilizing focus movement to measure the surface shape.

[0059] The smooth portion 32a may be made of the same material as the base or a different material, specifically, aluminum, stainless steel, alloys such as Hastelloy (registered trademark), soda-lime glass, borosilicate glass, quartz, silicon carbide, or ceramics such as silicon nitride and aluminum nitride. The smoothness of such a smooth portion 32a can be easily obtained, for example, by grinding the surface with diamond abrasive grains in the case of borosilicate glass and then further performing mirror finishing by chemical mechanical polishing (CMP) using colloidal silica. In addition, the smooth portion 32a can be maintained at a lower temperature than the substrate mounting portion 32b. As a result, the evaporation of the raw material mist on the surface of the smooth portion 32a can be suppressed, thereby suppressing the generation of particles due to the evaporated mist, and further maintaining the smoothness of the smooth portion 32a for a longer period of time. The temperature of the smooth portion 32a at this time can be appropriately optimized according to the type of raw material mist and its various film forming conditions. When water is used as the solvent for the raw material mist, it is usually best to set it to about 30°C to 100°C. There is no particular limitation on the cooling method of the smooth portion 32a, and known temperature control means can be applied. For example, a refrigerant not shown can be brought into contact with the inside or back of the smooth portion 32a for heat exchange, or a Peltier element can be used for cooling.

[0060] (Substrate) The substrate 33 can support the formed film. The material of the substrate 33 is not particularly limited, and can be a known material, an organic compound, or an inorganic monomer or inorganic compound. For example, polysulfone, polyethersulfone, polyphenylene sulfide, polyetheretherketone, polyimide, polyetherimide, fluororesin, metals such as iron, aluminum, stainless steel and gold, silicon, sapphire, quartz, glass, calcium carbonate, lithium tantalate, lithium niobate, gallium oxide, SiC, ZnO and GaN can be cited, but it is not limited thereto. The size of the substrate 33 is preferably 5 cm 2 More than 10 cm 2 The thickness is preferably 50 to 2000 μm, more preferably 100 to 800 μm. from Figure 2 The shape of the mounting portion shown in the figure can be inferred that the shape of the substrate 33 is circular in a plan view, but is not limited thereto and may be rectangular or polygonal in a plan view. It should be noted that when the shape and size of the substrate 33 are changed, the shape and size of the placement portion 32 b are changed according to the shape and size of the substrate 33 .

[0061] (Smoothness of substrate) The surface roughness (arithmetic mean roughness) Ra_sub of the surface of the substrate 33 is preferably set to be less than the surface roughness (arithmetic mean roughness) Ra_cor of the surface of the smooth portion 32a. Thus, the mixed gas can maintain a laminar flow even on the substrate surface. If the surface roughness (arithmetic mean roughness) Ra_sub of the surface of the substrate 33 is greater than the surface roughness (arithmetic mean roughness) Ra_cor of the surface of the smooth portion 32a, abnormal growth is likely to occur on the substrate 33. The value of the surface roughness (arithmetic mean roughness) Ra_sub of the surface of the substrate 33 is preferably set to, for example, 0.05 nm or more and 1 μm or less. The surface smoothness of such a substrate 33 can be easily obtained, for example, in the case of sapphire, by grinding the surface of the substrate 33 obtained by crystal processing with diamond abrasives and then further applying mirror finishing by chemical mechanical polishing (CMP) using colloidal silica.

[0062] Next, use Figure 6 , a method of flowing a mixed gas toward a substrate mounted on a susceptor of a film forming apparatus according to the present invention is described from the perspective of an inflow direction of the mixed gas and a height difference between the substrate and the susceptor.

[0063] (Direction of mixed gas inflow) In the film forming apparatus according to the present invention, the substrate 33 is placed on the substrate placement portion 32 b provided on the susceptor 32 , and a part of the mixed gas 112 flows toward the substrate 33 along the smooth portion 32 a . At this time, the angle θ formed by the inflow direction of the mixed gas 112 and the smooth portion 32 a is not particularly limited. However, it is preferably set to be 0° or more and 60° or less. If it exceeds 60°, the mixed gas 112 may collide with the upper surface of the susceptor 32 or the substrate 33, causing turbulence, and some powder may be produced and adhere to the film surface, but if it is set to be 0° or more and 60° or less, this can be suppressed. It is more preferably set to be 0° or more and 45° or less. It should be noted that Figure 1 The angle θ in the embodiment can also be said to be an inclination angle of the smooth portion 32a with respect to the horizontal plane.

[0064] (Height Difference) The height difference h between the surface of the substrate 33 and the surface of the smooth portion 32a is not particularly limited, but is preferably greater than -1 mm and less than 1 mm. Within this range, the thickness uniformity of the end of the substrate is improved, and turbulence does not occur at the end. If there is a height difference of more than 1 mm, film thickness distribution may occur, especially near the end of the substrate adjacent to the smooth portion 32a. The positive or negative value of the numerical value indicated here indicates the relative position of the substrate surface with respect to the smooth portion surface. A negative value indicates that the substrate surface is recessed with respect to the smooth portion surface, and a positive value indicates that the substrate surface protrudes with respect to the smooth portion surface. When the substrate surface is higher than the smooth surface, the mixed gas will be concentrated at the end of the substrate, resulting in a thicker film. On the contrary, when the substrate surface is lower than the smooth surface, the mixed gas will skip over the end of the substrate due to the height difference, resulting in a thinner film. In addition, such a structure may cause turbulence in the mixed gas flow. The thickness of a film formed on a substrate can be measured by any known method, and for example, ellipsometry, optical interference spectroscopy, a stylus method, or a laser displacement method is preferably used.

[0065] (Exhaust means 40) The remaining mixed gas 112 that does not contribute to film formation and byproducts generated when the mixed gas 112 reacts on the substrate 33 are sucked into the exhaust means 40 as a mixed gas after film formation and exhausted to the outside of the system. The exhaust gas passing through the exhaust means 40 can be processed as needed by an exhaust device such as a particle collector, a combustion device, a scrubber, etc. that is not shown, or can be processed by a filter for raw material recovery, etc. In addition, it can also be processed by a combination of these.

[0066] Figure 1 , a method of using one atomizing means 20 is shown, but the film forming apparatus according to the present invention is not limited thereto, and multiple atomizing means 20 can be connected in series or in parallel for use. In this case, different raw material solutions can be placed in each atomizing means 20 for use, or the same raw material solution can be placed in each atomizing means 20 for use. In addition, each raw material solution can be atomized separately and supplied to the film forming section 30 independently, or a plurality of raw material mists can be mixed in advance and supplied to the film forming section 30.

[0067] Figure 1 and Figure 2 The mixed gas 112 is shown as flowing unidirectionally from the supply side to the exhaust side of the film forming chamber 31 relative to the substrate 33 , but the present invention is not limited thereto, and the mode can be set according to the supply method of the mixed gas 112 relative to the substrate.

[0068] [Film Forming Method] Next, use Figure 1 , Figure 2 The film forming method of the present invention will be described. The film forming method of the present invention includes a raw material mist forming step, a mixed gas forming step, a substrate mounting step, a film forming step, and an exhaust step.

[0069] (Raw material mist forming step) The raw material mist forming step is a step of forming the raw material mist 22 by atomizing the raw material solution 21 .

[0070] (Mixed gas forming step) The mixed gas forming step is a step of mixing the raw material mist 22 and the carrier gas 111 to form the mixed gas 112 .

[0071] (Substrate mounting step) The substrate placement step is a step of placing the substrate 33 on the placement portion 32 b of the susceptor 32 .

[0072] (Film Forming Step) The film forming step is a step of supplying the mixed gas 112 from the atomizing means 20 to the substrate 33 to form a film on the substrate 33 through a thermal reaction. In this step, at least a part of the mixed gas 112 is supplied to the surface of the substrate 33 from the smooth portion 32 a adjacent to the mounting portion 32 b and having a surface roughness (arithmetic mean roughness) Ra_cor of 200 μm or less.

[0073] (Exhaust Steps) The exhaust step is a step of exhausting the mixed gas 112 after film formation by using the exhaust means 40 .

[0074] According to such a film forming method, since the mixed gas 112 including the raw material mist 22 is supplied to the substrate 33 while maintaining a laminar flow, the generation and abnormal growth of powder can be suppressed, so that a high-quality film can be stably manufactured on the surface of the substrate 33 with a large diameter.

[0075] The surface roughness of the smooth portion 32a is preferably set to 150 μm or less. This allows a higher quality film to be manufactured more stably.

[0076] The height difference h between the surface of the smooth portion 32a and the surface of the substrate 33 is preferably set to be not less than -1 mm and not more than 1 mm. According to such a film forming method, the mixed gas 112 can maintain a laminar flow more stably, so a high-quality film can be stably and uniformly manufactured.

[0077] The angle θ formed by the surface of the smooth portion 32a and the direction in which the mixed gas 112 flows into the smooth portion 32a is preferably set to be greater than 0° and less than 60°. This film forming method can maintain the mixed gas 112 in a more stable laminar flow, thereby more stably manufacturing a high-quality film.

[0078] (Second Embodiment) The second embodiment adopts Figure 3 The configuration is the same as that of the first embodiment except that the susceptor 32 shown in (a) is used and the film formation is performed by intermittently rotating the susceptor 32 by 180 degrees. At this time, if Figure 3 As shown in (a), the mixed gas 112 is supplied to the placement portion 32b from above and below the paper surface, and accordingly, the smooth portions 32a are formed in the directions in which the mixed gas 112 flows. This configuration also enables the mixed gas 112 to be supplied to the surface of the substrate in a laminar flow.

[0079] (Third Embodiment) The third embodiment adopts Figure 3 The configuration is the same as that of the first embodiment except that the nozzle (not shown) for discharging the mixed gas 112 is opposite to the susceptor 32 and the relative position between the nozzle and the susceptor 32 is changed along one axial direction to perform film formation. At this time, if Figure 3 As shown in (b), the mixed gas 112 is supplied to the supporting portion 32b from above and below the paper surface, and accordingly, a smooth portion 32a is formed in the direction in which the mixed gas flows in, but the smooth portion 32a at least includes the area surrounded by the discharge outlet width W and the variable length L of the nozzle minus the area of ​​the supporting portion 32b. At this time, the outlet width W only needs to be longer than the width of the substrate parallel to W. For example, it can be set to be greater than 1.0 times and less than 2 times the width of the substrate. However, in order to more stably suppress the deterioration of the film thickness distribution caused by the discontinuity of mist concentration that is easily generated at the nozzle end, it is more preferably greater than 1.1 times and less than 1.5 times. In addition, the variable length L also depends on the shape and configuration of the nozzle used, but generally speaking, as long as the length is greater than the width of the substrate parallel to L, it will suffice. For example, it can be set to greater than 1.0 times and less than 1.5 times the width of the substrate, but from the perspective of productivity, it is more preferably set to less than 1.2 times. This configuration also enables the mixed gas 112 to be supplied to the surface of the substrate in a laminar flow.

[0080] (Fourth Embodiment) The fourth embodiment adopts the following Figure 4 The configuration is the same as that of the first embodiment except that the susceptor 32 shown is provided with a smooth portion 32 a so as to surround a mounting portion 32 b and the susceptor 32 is continuously rotated relative to the one-way mixed gas 112 to perform film formation. like Figure 4 As shown, the film formation is performed by continuously rotating the susceptor 32 relative to the unidirectional mixed gas 112. With this configuration, the mixed gas 112 can also be supplied to the surface of the substrate in a laminar flow.

[0081] (Fifth Embodiment) The fifth embodiment adopts the following Figure 5 The configuration is the same as that of the first embodiment except that the susceptor 32 shown is provided with a smooth portion 32 a so as to surround a mounting portion 32 b and film formation is performed by supplying a mixed gas 112 in a swirl flow to the fixed susceptor 32 . like Figure 5 As shown, the mixed gas 112 is supplied to the fixed susceptor 32 in a swirl flow to form a film. With this configuration, the mixed gas 112 can also be supplied to the surface of the substrate in a laminar flow.

[0082] In the first to fifth embodiments, the base 32 is exemplified as having a circular mounting portion 32b corresponding to the circular substrate 33, but the base of the film forming apparatus according to the present invention is not limited thereto and can be set as a mounting portion corresponding to a substrate of the shape previously described.

[0083] In the first to fifth embodiments, the substrate 33 is disposed with the film-forming surface facing upward, but the present invention is not limited thereto, and the substrate 33 may be disposed with the film-forming surface facing downward.

[0084] (Semiconductor Device) The film forming method according to the present invention can be applied to any type of film, such as metal film, semiconductor film and insulator film, but can be preferably used in the manufacture of semiconductor film in particular. In addition, the semiconductor film and laminated body according to the film forming method of the present invention are useful in industry because they can suppress defects such as particles and abnormal growth and have excellent electrical properties.

[0085] Such films and laminates can be preferably used in semiconductor devices, etc. In addition, the crystal layer formed as a part of the laminate can be used as it is (laminate state), or can be peeled off from the crystal substrate, etc. by a known method, and then applied to semiconductor devices, etc.

[0086] In addition, semiconductor devices can be classified into horizontal elements (horizontal devices) in which electrodes are formed on one side of a semiconductor layer and vertical elements (vertical devices) in which electrodes are respectively formed on the front and back sides of a semiconductor layer. At least a part of the laminate according to the present invention can be preferably used in either a horizontal device or a vertical device. It is particularly preferred to be used in a vertical device.

[0087] Examples of the semiconductor device include a Schottky barrier diode (SBD), a metal semiconductor field effect transistor (MESFET), a high electron mobility transistor (HEMT), a metal oxide semiconductor field effect transistor (MOSFET), a junction field effect transistor (JFET), an insulated gate bipolar transistor (IGBT), and a light emitting diode (LED).

[0088] (α-Gallium Oxide Film) As a film formed by the film forming method according to the present invention, an α-gallium oxide film can be exemplified. As a specific example, an α-gallium oxide film can be exemplified which is formed on substantially the entire surface of a c-plane sapphire substrate having a diameter of more than 4 inches, the half-width of the rocking curve of the (0006) plane X-ray diffraction peak of the α-gallium oxide film being less than 9.5 seconds, and the film thickness distribution being less than ±9%. It should be noted that the “substantially the entire surface” mentioned here refers to a region that accounts for 80% or more of the total area of ​​the substrate surface.

[0089] As a result, a high-quality α-gallium oxide film with good crystal orientation and good film thickness distribution is obtained. It should be noted that the smaller the half width of the rocking curve, the more preferable it is, and therefore the lower limit is, for example, more than 0 seconds. The film thickness distribution can be calculated by, for example, calculating the film thickness at a plurality of points on the film surface using a known method such as optical interference spectroscopy and dividing the difference between the maximum value and the minimum value by twice the average value. In addition, the upper limit of the diameter of the c-plane sapphire substrate is not particularly limited, and is, for example, about 12 inches (about 30 cm).

[0090] Alternatively, an α-gallium oxide film can be exemplified, characterized in that it is formed on substantially the entire surface of a c-plane sapphire substrate having a diameter of 4 inches or more, and the foreign matter density is 1.1 cm -2 Below, and the film thickness distribution is below ±9%.

[0091] Thus, a high-quality α-gallium oxide film with low foreign matter density is formed on substantially the entire surface of the large-diameter substrate. Foreign matter here refers to convex objects existing on the film surface, especially particles and abnormally grown grains, which can be detected by a known wafer defect inspection device. It should be noted that since the lower the foreign matter density, the better, the lower limit is, for example, 0 cm -2 . In addition, the upper limit of the diameter of the c-plane sapphire substrate is not particularly limited, and is, for example, about 12 inches. Example

[0092] The present invention will be specifically described below using Examples and Comparative Examples, but the present invention is not limited thereto.

[0093] (Example 1) exist Figure 1 In the film forming apparatus, the α-gallium oxide film is formed according to the following steps. In the film forming device, a gas cylinder filled with nitrogen gas is used to supply carrier gas. The gas cylinder and the atomizing device are connected by a polyurethane resin pipe, and the atomizing device and the film forming chamber are further connected by a quartz pipe.

[0094] First, a c-plane single crystal sapphire substrate with a thickness of 0.65 mm and a diameter of 4 inches (about 10 cm) was placed on a Figure 2 The surface structure is on a SiC base with an inclination angle (θ) of 35°. At this time, the height difference h between the smooth portion surface and the substrate surface was 0 mm. It should be noted that the surface roughness (arithmetic mean roughness) Ra_cor of the smooth portion was measured at 5 points on the surface of the smooth portion provided on the base using AFM (Nanosurf Nanite AFM), and the average value was 0.55 μm. In addition, the surface roughness (arithmetic mean roughness) Ra_sub of the sapphire substrate was measured at 5 points in the cross direction passing through the center of the substrate using AFM, and the average value was 0.08 nm.

[0095] Next, as a raw material solution, gallium acetylacetonate was dissolved at a ratio of 0.05 mol / L in a dilute hydrochloric acid aqueous solution to which 34% hydrochloric acid was added at a volume ratio of 1%, and the solution was filled into an atomizing device (atomizing means). Next, ultrasonic vibration is transmitted to the raw material solution in the atomizing device through water by the ultrasonic vibration plate, thereby atomizing (atomizing) the raw material solution. Next, nitrogen gas was added to the container of the raw material solution in the atomizing device (atomizing means) at a flow rate of 20 L / min to form a mixed gas of mist and nitrogen gas.

[0096] Next, the substrate placed on the placement portion of the susceptor was heated to a substrate temperature of 450°C. Next, the mixed gas was supplied to the film forming chamber, and film formation was performed for 60 minutes. Subsequently, the supply of nitrogen gas was stopped, and the supply of the mixed gas to the film forming chamber was stopped.

[0097] The produced film was transparent in appearance except for a region other than a 5 mm outer peripheral width of the film-forming surface. X-ray diffraction measurement (Rigaku SmartLab) confirmed that it was α-phase Ga2O3 (α-gallium oxide film). The rocking curve of the α-Ga2O3 (0006) plane was measured at five points in the cross direction passing through the center of the substrate, and the half width was evaluated. It should be noted that when measuring the rocking curve, a four-crystal monochromator composed of two grooved crystals was used to improve the monochromaticity of the X-ray, thereby measuring with higher accuracy. Other measurement conditions are as follows. [Measurement conditions] ·Measurement device: SmartLab manufactured by Rigaku Analytical conditions: Measurement method: Rocking curve measurement (ω scan) X-ray generating part: cathode Cu : Output 45kV 200mA Detection unit: Semiconductor detector Incident optical system: Ge(220) slot monochromator Solar Slit: Entrance Side - : Light receiving side 5.0° Slit: Incident side IS = 1 (mm) :Length limit 0.5(mm) :Light receiving side RS1=1RS2=1.1(mm) Scanning conditions: Evaluated diffraction surface Ga2O3(0006) : Scanning axis ω :Scanning mode step measurement :Scanning range 18~22° :Step width 0.005° :Accumulated time 0.5sec. / step In addition, the density of foreign matter (diameter 0.3 μm or more) in the area other than the 5 mm outer circumference width of the film formation surface was evaluated using a substrate inspection machine (KLA candela-CS10). It should be noted that foreign matter here refers to convex objects on the film surface, especially particles and abnormally grown grains. Thereafter, the thickness of the prepared film was measured at 21 points within the film surface by optical interference spectroscopy (Filmetrics F50), and the film thickness distribution was calculated by dividing the difference between the maximum value and the minimum value by twice the average value.

[0098] (Example 2) The film formation was performed in the same manner as in Example 1, except that the surface roughness (arithmetic mean roughness) Ra_cor of the smooth portion was set to 183 μm. The film was transparent in appearance except for the 5 mm outer peripheral width of the film-forming surface, and was confirmed to be α-phase Ga 2 O 3 by X-ray diffraction measurement. Thereafter, the film was evaluated in the same manner as in Example 1.

[0099] (Comparative Example 1) The film was formed in the same manner as in Example 1, except that the surface roughness (arithmetic mean roughness) Ra_cor of the smooth portion was set to 220 μm. The appearance of the prepared film was slightly turbid from the outer periphery of the substrate adjacent to the smooth portion to the inner portion. X-ray diffraction measurement confirmed that it was α-phase Ga2O3. Thereafter, the film was evaluated in the same manner as in Example 1.

[0100] (Example 3) The film was formed in the same manner as in Example 1 except that the height difference h was set to 0.85 mm (the substrate surface was higher than the smooth portion surface). The film was transparent in appearance except for the 5 mm outer peripheral width of the film-forming surface, and was confirmed to be α-phase Ga 2 O 3 by X-ray diffraction measurement. Thereafter, the film was evaluated in the same manner as in Example 1.

[0101] (Example 4) The film was formed in the same manner as in Example 1 except that the height difference h was set to 0.85 mm (the substrate surface was lower than the smooth portion surface). The film was transparent in appearance except for the 5 mm outer peripheral width of the film-forming surface, and was confirmed to be α-phase Ga 2 O 3 by X-ray diffraction measurement. Thereafter, the film was evaluated in the same manner as in Example 1.

[0102] (Comparative Example 2) Film formation was performed in the same manner as in Example 1, except that the surface roughness (arithmetic mean roughness) Ra_cor of the smooth portion was set to 220 μm and the height difference h was set to 1.2 mm. The appearance of the prepared film was turbid in a wide range from the outer periphery of the substrate adjacent to the smooth portion to the inner portion. X-ray diffraction measurement confirmed that it was α-phase Ga2O3. Thereafter, the film was evaluated in the same manner as in Example 1.

[0103] (Comparative Example 3) Film formation was performed in the same manner as in Example 1, except that the surface roughness (arithmetic mean roughness) Ra_cor of the smooth portion was set to 220 μm and the height difference h was set to −1.2 mm. The appearance of the prepared film was turbid in a wide range from the outer periphery of the substrate adjacent to the smooth portion to the inner portion. X-ray diffraction measurement confirmed that it was α-phase Ga2O3. Thereafter, the film was evaluated in the same manner as in Example 1.

[0104] (Example 5) The film was formed in the same manner as in Example 1 except that the inclination angle (θ) was set to 55°. The film was transparent in appearance except for the 5 mm outer peripheral width of the film-forming surface, and was confirmed to be α-phase Ga 2 O 3 by X-ray diffraction measurement. Thereafter, the film was evaluated in the same manner as in Example 1.

[0105] (Comparative Example 4) The film was formed in the same manner as in Example 1 except that the surface roughness (arithmetic mean roughness) Ra_cor of the smooth portion was set to 220 μm and the inclination angle (θ) was set to 80°. The appearance of the prepared film was turbid in a wide range from the outer periphery of the substrate adjacent to the smooth portion to the inner portion. It was confirmed to be α-phase Ga2O3 by X-ray diffraction measurement. Thereafter, the film was evaluated in the same manner as in Example 1.

[0106] (Example 6) The film was formed in the same manner as in Example 1, except that the surface roughness (arithmetic mean roughness) Ra_cor of the smooth portion was set to 200 μm. The film was transparent in appearance except for the 5 mm outer peripheral width of the film-forming surface, and was confirmed to be α-phase Ga 2 O 3 by X-ray diffraction measurement. Thereafter, the film was evaluated in the same manner as in Example 1.

[0107] (Example 7) The film was formed in the same manner as in Example 1, except that the surface roughness (arithmetic mean roughness) Ra_cor of the smooth portion was set to 150 μm. The film was transparent in appearance except for the 5 mm outer peripheral width of the film-forming surface, and was confirmed to be α-phase Ga 2 O 3 by X-ray diffraction measurement. Thereafter, the film was evaluated in the same manner as in Example 1. Table 1 shows the evaluation results of Examples 1, 2, 3, 4, 5, 6 and 7 and Comparative Examples 1, 2, 3 and 4.

[0108]

Table 1

[0109] The film prepared by the film forming method according to the present invention has a lower half width (good crystal orientation), a stable film growth with a good film thickness distribution, and a low foreign matter density. In contrast, in the film forming according to the previous method, due to the turbidity caused by abnormal growth, the crystal orientation deteriorates, and the film thickness distribution and foreign matter density increase significantly. It is believed that due to the increase in the surface roughness of the smooth part, the mixed airflow becomes turbulent, resulting in abnormal growth caused by abnormal nucleation and precipitation of raw material solids, thereby promoting the adhesion of foreign matter.

[0110] As can be seen from the above results, according to the present invention, it is possible to provide a film forming apparatus capable of stably manufacturing a film of higher quality than the conventional technology.

[0111] This specification includes the following aspects. [1]: A film forming method, characterized in that it includes the following steps: a step of atomizing a raw material solution to form a raw material mist; a step of mixing the raw material mist with a carrier gas to form a mixed gas; a step of placing a substrate on a mounting portion of a susceptor; a step of supplying the mixed gas from an atomizing means to the substrate and forming a film on the substrate by a thermal reaction; and a step of exhausting the mixed gas after film formation by an exhaust means; in the step of supplying the mixed gas from an atomizing means to the substrate and forming a film on the substrate by a thermal reaction, at least a portion of the mixed gas is supplied to the surface of the substrate from a smooth portion adjacent to the mounting portion and having a surface roughness of less than 200 μm. [2]: The film forming method according to [1] above, characterized in that the surface roughness is set to 150 μm or less. [3]: The film forming method according to the above [1] or [2] is characterized in that the height difference between the surface of the smooth portion and the surface of the substrate placed on the placement portion is set to be greater than -1 mm and less than +1 mm. [4]: The film forming method according to any one of [1] to [3] above, characterized in that the angle formed by the surface of the smooth portion and the direction in which the mixed gas flows into the smooth portion is set to be greater than 0° and less than 60°. [5]: A film forming device, characterized in that it comprises: a carrier gas supplying means for supplying a carrier gas; an atomizing means for atomizing a raw material solution to generate a raw material mist; a film forming section for supplying a mixed gas of the raw material mist and the carrier gas to a substrate to form a film; and a heating means for heating the substrate; the film forming section comprises a base, the base comprises a mounting portion for mounting the substrate, the base comprises a smooth portion adjacent to the mounting portion, at least a portion of the mixed gas flows through the smooth portion, and the surface roughness of the smooth portion is less than 200 μm. [6]: The film forming apparatus according to the above-mentioned [5] is characterized in that the surface roughness is set to be less than 150 μm. [7]: The film forming device according to the above [5] or [6] is characterized in that the height difference between the surface of the smooth portion and the surface of the substrate placed on the placement portion is set to be greater than -1 mm and less than +1 mm. [8]: A film forming apparatus according to any one of [5] to [7] above, characterized in that an angle formed between the surface of the smooth portion and the direction in which the mixed gas flows into the smooth portion is set to be greater than 0° and less than 60°. [9]: A susceptor, characterized in that it has a placement portion for placing the substrate in a film forming device, wherein the film forming device comprises: a carrier gas supplying means for supplying a carrier gas; an atomizing means for atomizing a raw material solution to generate a raw material mist; a film forming portion for supplying a mixed gas of the raw material mist and the carrier gas to the substrate to form a film; and a heating means for heating the substrate. The susceptor includes a smooth portion adjacent to the mounting portion, and at least a portion of the mixed gas flows through the smooth portion. The surface roughness of the smooth portion is set to 200 μm or less.

[10] : The base according to the above [9] is characterized in that the surface roughness is set to be less than 150 μm.

[11] : The base according to the above [9] is characterized in that the surface roughness of the smooth portion is less than 200 μm, and the height difference between the surface of the smooth portion and the surface of the substrate placed on the placement portion is greater than -1 mm and less than +1 mm.

[12] : An α-gallium oxide film, characterized in that the half-width of the rocking curve of the (0006) plane X-ray diffraction peak of the α-gallium oxide film formed on substantially the entire surface of a c-plane sapphire substrate having a diameter of more than 4 inches is less than 9.5 seconds, and the film thickness distribution is less than ±9%.

[13] : An α-gallium oxide film, characterized in that it is formed on substantially the entire surface of a c-plane sapphire substrate having a diameter of 4 inches or more and a foreign matter density of 1.1 cm -2 Below, and the film thickness distribution is below ±9%.

[0112] It should be noted that the present invention is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any technical solution having substantially the same configuration as the technical idea described in the claims of the present invention and having the same effect is included in the technical scope of the present invention.

Claims

1. A film forming method, characterized in that: include: A step of atomizing the raw material solution to form raw material mist; The step of mixing the raw material mist with a carrier gas to form a mixed gas; The step of placing the substrate on a placing portion of the susceptor; The mixed gas is supplied from an atomizing means to the substrate to form a film on the substrate through a thermal reaction; The step of exhausting the mixed gas after film formation through exhaust means; In the step of supplying the mixed gas from the atomizing means to the substrate and forming a film on the substrate by thermal reaction, at least a portion of the mixed gas is supplied to the surface of the substrate from a smooth portion adjacent to the mounting portion and having a surface roughness of 200 μm or less.

2. The film forming method according to claim 1, characterized in that: The surface roughness is set to 150 μm or less.

3. The film forming method according to claim 1 or 2, characterized in that: The height difference between the surface of the smooth portion and the surface of the substrate placed on the placement portion is set to be greater than or equal to -1 mm and less than or equal to +1 mm.

4. The film forming method according to claim 1 or 2, characterized in that: The angle formed between the surface of the smooth portion and the direction in which the mixed gas flows into the smooth portion is set to be greater than or equal to 0° and less than or equal to 60°.

5. A film forming device, characterized in that: have: A carrier gas supply means for supplying a carrier gas; Atomization means, atomizing the raw material solution to produce raw material mist; A film forming section, supplying a mixed gas of the raw material mist and the carrier gas to a substrate to form a film; Heating means capable of heating the substrate; The film forming unit includes a susceptor having a mounting portion for mounting the substrate. The base has a smooth portion, the smooth portion is adjacent to the mounting portion, and at least a portion of the mixed gas flows through the smooth portion. The surface roughness of the smooth portion is set to 200 μm or less.

6. The film forming device according to claim 5, characterized in that: The surface roughness is set to 150 μm or less.

7. The film forming device according to claim 5 or 6, characterized in that: The height difference between the surface of the smooth portion and the surface of the substrate placed on the placement portion is set to be not less than -1 mm and not more than +1 mm.

8. The film forming device according to claim 5 or 6, characterized in that: An angle formed between a surface of the smooth portion and a direction in which the mixed gas flows into the smooth portion is greater than or equal to 0° and less than or equal to 60°.

9. A base, characterized in that: The susceptor has a placement portion for placing the substrate on the film forming device. The film forming device comprises: a carrier gas supply means for supplying a carrier gas; an atomizing means for atomizing a raw material solution to generate a raw material mist; a film forming part for supplying a mixed gas of the raw material mist and the carrier gas to a substrate to form a film; and a heating means capable of heating the substrate. The base includes a smooth portion, the smooth portion is adjacent to the mounting portion, and at least a portion of the mixed gas flows through the smooth portion. The surface roughness of the smooth portion is set to 200 μm or less.

10. The base according to claim 9, characterized in that The surface roughness is set to 150 μm or less.

11. The base according to claim 9, characterized in that The surface roughness of the smooth portion is 200 μm or less, and the height difference between the surface of the smooth portion and the surface of the substrate placed on the placement portion is not less than −1 mm and not more than +1 mm.

12. An α-gallium oxide film, characterized in that: The α-gallium oxide film formed on substantially the entire surface of a c-plane sapphire substrate having a diameter of 4 inches or more has a rocking curve of a (0006) plane X-ray diffraction peak of 9.5 seconds or less and a film thickness distribution of ±9% or less.

13. An α-gallium oxide film, characterized in that: It is formed on almost the entire surface of a c-plane sapphire substrate with a diameter of more than 4 inches, and the foreign matter density is 1.1cm -2 Below, and the film thickness distribution is below ±9%.

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