METHOD FOR FORMING FILM, FILM-FORMING APPARATUS, SUSCEPTOR, AND a-GALLIUM OXIDE FILM

Abstract

A method for forming a film, including: atomizing a raw material solution into a mist to form raw material mist; mixing raw material mist and a carrier gas to form gas mixture; placing a substrate on a placement section of susceptor; supplying gas mixture from an atomizer to the substrate to perform film formation by thermal reaction on substrate; and discharging gas mixture after the film formation through an exhaust unit, wherein in the step of supplying the gas mixture from atomizer to substrate to perform film formation by thermal reaction on the substrate, at least a part of gas mixture is supplied from a smooth section adjacent to placement section to a surface of substrate, the smooth section having a surface roughness of 200 m or less. A method for forming a film capable of uniformly and stably producing a high-quality film on a surface of a large-diameter substrate.

Claims

1.-13. (canceled)

14. A method for forming a film, comprising the steps of: atomizing a raw material solution into a mist to form a raw material mist; mixing the raw material mist and a carrier gas to form a gas mixture; placing a substrate on a placement section of a susceptor; supplying the gas mixture from an atomizer to the substrate to perform film formation by thermal reaction on the substrate; and discharging the gas mixture after the film formation through an exhaust unit, wherein in the step of supplying the gas mixture from the atomizer to the substrate to perform film formation by thermal reaction on the substrate, at least a part of the gas mixture is supplied from a smooth section adjacent to the placement section to a surface of the substrate, the smooth section having a surface roughness of 200 m or less.

15. The method for forming a film according to claim 14, wherein the surface roughness is 150 m or less.

16. The method for forming a film according to claim 14, wherein difference in height between a surface of the smooth section and the surface of the substrate placed on the placement section is 1 mm or more and +1 mm or less.

17. The method for forming a film according to claim 15, wherein difference in height between a surface of the smooth section and the surface of the substrate placed on the placement section is 1 mm or more and +1 mm or less.

18. The method for forming a film according to claim 14, wherein an angle between a surface of the smooth section and a flowing direction of the gas mixture into the smooth section is 0 or more and 60 or less.

19. The method for forming a film according to claim 15, wherein an angle between a surface of the smooth section and a flowing direction of the gas mixture into the smooth section is 0 or more and 60 or less.

20. A film-forming apparatus, comprising: a carrier gas supplier configured to supply a carrier gas; an atomizer configured to atomize a raw material solution into a mist to generate a raw material mist; a film-forming unit configured to supply a gas mixture of the raw material mist and the carrier gas to a substrate to perform film formation; and a heater capable of heating the substrate, wherein the film-forming unit has a susceptor comprising a placement section on which the substrate is placed, the susceptor comprises a smooth section adjacent to the placement section, through which at least a part of the gas mixture flows, and the smooth section has a surface roughness of 200 m or less.

21. The film-forming apparatus according to claim 20, wherein the surface roughness is 150 m or less.

22. The film-forming apparatus according to claim 20, wherein difference in height between a surface of the smooth section and a surface of the substrate placed on the placement section is 1 mm or more and +1 mm or less.

23. The film-forming apparatus according to claim 21, wherein difference in height between a surface of the smooth section and a surface of the substrate placed on the placement section is 1 mm or more and +1 mm or less.

24. The film-forming apparatus according to claim 20, wherein an angle between a surface of the smooth section and a flowing direction of the gas mixture into the smooth section is 0 or more and 60 or less.

25. The film-forming apparatus according to claim 21, wherein an angle between a surface of the smooth section and a flowing direction of the gas mixture into the smooth section is 0 or more and 60 or less.

26. A susceptor comprising a placement section on which a substrate is placed in a film-forming apparatus, the film-forming apparatus comprising: a carrier gas supplier configured to supply a carrier gas; an atomizer configured to atomize a raw material solution into a mist to generate a raw material mist; a film-forming unit configured to supply a gas mixture of the raw material mist and the carrier gas to the substrate to perform film formation; and a heater capable of heating the substrate, wherein a smooth section through which at least a part of the gas mixture flows is disposed adjacent to the placement section, and the smooth section has a surface roughness of 200 m or less.

27. The susceptor according to claim 26, wherein the surface roughness is 150 m or less.

28. The susceptor according to claim 26, wherein the smooth section has the surface roughness of 200 m or less, and difference in height between a surface of the smooth section and a surface of the substrate placed on the placement section is 1 mm or more and +1 mm or less.

29. An -gallium oxide film to be formed on approximately an entire surface of a c-plane sapphire substrate having a diameter of 4 inches or more, wherein the -gallium oxide film has a half width of an x-ray diffraction rocking curve peak of a (0006) plane of 9.5 seconds or less, and a film thickness distribution of 9% or less.

30. An -gallium oxide film to be formed on approximately an entire surface of a c-plane sapphire substrate having a diameter of 4 inches or more, wherein a foreign substance density in the -gallium oxide film is 1.1 cm.sup.2 or less, and a film thickness distribution of the -gallium oxide film is 9% or less.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0043] FIG. 1 is a diagram illustrating one configuration of a film-forming apparatus according to the present invention;

[0044] FIG. 2 is a diagram illustrating one configuration of a susceptor of a film-forming apparatus according to the present invention;

[0045] FIG. 3(a) is a diagram illustrating another configuration of a susceptor of a film-forming apparatus according to the present invention, and FIG. 3(b) is a diagram illustrating yet another configuration of a susceptor of a film-forming apparatus according to the present invention;

[0046] FIG. 4 is a diagram illustrating yet another configuration of a susceptor of a film-forming apparatus according to the present invention;

[0047] FIG. 5 is a diagram illustrating yet another configuration of a susceptor of a film-forming apparatus according to the present invention;

[0048] FIG. 6 is a diagram illustrating one form of a flow of a gas mixture toward a substrate placed on a susceptor of a film-forming apparatus according to the present invention;

[0049] FIG. 7 shows examples of various recesses and protrusions with abnormal growth of a film surface as can been seen by microscopic observation on cloudiness; and

[0050] FIG. 8 shows other examples of various recesses and protrusions with abnormal growth of a film surface as can been seen by microscopic observation on cloudiness.

DESCRIPTION OF EMBODIMENTS

[0051] Hereinafter, the present invention will be described in detail. However, the present invention is not limited thereto.

[0052] As described above, there have been demands for a method for forming a film, a film-forming apparatus, and a susceptor, that enable to uniformly and stably produce a high-quality film on a surface of a large-diameter substrate.

[0053] The present inventor has made an intensive investigation on the above problem, and consequently found that: [0054] stable production of a high-quality film and thus highly productive film formation are made possible by a method for forming a film, including the steps of:
atomizing a raw material solution into a mist to form a raw material mist; mixing the raw material mist and a carrier gas to form a gas mixture; placing a substrate on a placement section of a susceptor; supplying the gas mixture from an atomizer to the substrate to perform film formation by thermal reaction on the substrate; and discharging the gas mixture after the film formation through an exhaust unit, wherein in the step of supplying the gas mixture from the atomizer to the substrate to perform film formation by thermal reaction on the substrate, at least a part of the gas mixture is supplied from a smooth section adjacent to the placement section to a surface of the substrate, the smooth section having a surface roughness of 200 m or less; and [0055] stable production of a high-quality film and thus highly productive film formation are made possible by a film-forming apparatus, including: a carrier gas supplier configured to supply a carrier gas; an atomizer configured to atomize a raw material solution into a mist to generate a raw material mist; a film-forming unit configured to supply a gas mixture of the raw material mist and the carrier gas to a substrate to perform film formation; and a heater capable of heating the substrate, wherein the film-forming unit has a susceptor including a placement section on which the substrate is placed, the susceptor includes a smooth section adjacent to the placement section, through which at least a part of the gas mixture flows, and the smooth section has a surface roughness of 200 m or less; and [0056] stable production of a high-quality film and thus highly productive film formation are made possible by a susceptor including a placement section on which a substrate is placed in a film-forming apparatus, the film-forming apparatus including: a carrier gas supplier configured to supply a carrier gas; an atomizer configured to atomize a raw material solution into a mist to generate a raw material mist; a film-forming unit configured to supply a gas mixture of the raw material mist and the carrier gas to the substrate to perform film formation; and a heater capable of heating the substrate, wherein a smooth section through which at least a part of the gas mixture flows is disposed adjacent to the placement section, and the smooth section has a surface roughness of 200 m or less, [0057] and completed the present invention.

[0058] Furthermore, as described above, there has been a demand for an -gallium oxide film with higher quality than conventional ones.

[0059] The present inventor has made an intensive investigation on the above problem, and consequently found that -gallium oxide film with higher quality than conventional ones can be realized as: an -gallium oxide film to be formed on approximately an entire surface of a c-plane sapphire substrate having a diameter of 4 inches or more, wherein the -gallium oxide film has a half width of an x-ray diffraction rocking curve peak of a (0006) plane of 9.5 seconds or less, and a film thickness distribution of +9% or less; and an -gallium oxide film to be formed on approximately an entire surface of a c-plane sapphire substrate having a diameter of 4 inches or more, wherein a foreign substance density in the -gallium oxide film is 1.1 cm.sup.2 or less, and a film thickness distribution of the -gallium oxide film is +9% or less, and completed the present invention.

[0060] Hereinafter, the present invention will be described in detail with reference to the drawings. However, the present invention is not limited thereto.

FIRST EMBODIMENT

Film-Forming Apparatus

[0061] Firstly, one configuration of a film-forming apparatus according to the present invention will be described.

[0062] FIG. 1 illustrates one configuration of a film-forming apparatus according to the present invention. However, the film-forming apparatus according to the present invention is not limited to the film-forming apparatus illustrated in FIG. 1.

[0063] As illustrated in FIG. 1, a film-forming apparatus 1 according to the present invention includes a mechanism 50 for forming a gas mixture, a film-forming unit 30, and an exhaust unit 40. The mechanism 50 for forming a gas mixture has a carrier gas supplier 10 and an atomizer 20.

[0064] The carrier gas supplier 10 and the atomizer 20 are coupled to each other by a pipe 101. A carrier gas 111 is supplied from the carrier gas supplier 10 to the atomizer 20, in which a gas mixture is formed.

[0065] The atomizer 20 and a deposition chamber 31 of the film-forming unit 30 are coupled to each other by a pipe 102, and a gas mixture 112 is supplied from the atomizer 20 to the deposition chamber 31 of the film-forming unit 30.

[0066] The deposition chamber 31 of the film-forming unit 30 and the exhaust unit 40 are coupled to each other by a pipe 103, and the gas is discharged from the deposition chamber 31 of the film-forming unit 30 to the exhaust unit 40.

[0067] Note that the pipe 102 is not particularly limited as long as it has sufficient stability against a raw material solution 21 to be used, a temperature at an interface between the film-forming unit 30 and the pipe 102, etc., and can be made of resin, metal, glass, ceramic, or a combination of these materials according to its purpose.

[0068] The pipe 101 and the pipe 103 are also not particularly limited as long as they have sufficient stability.

(Carrier Gas Supplier 10)

[0069] The carrier gas supplier 10 supplies the carrier gas 111 toward the atomizer 20.

[0070] The carrier gas 111 is not particularly limited, and for example, air, oxygen, ozone, an inert gas such as nitrogen and argon, or a reducing gas such as hydrogen gas and forming gas is suitably used. The carrier gas 111 may include one kind or two or more kinds of carrier gasses. A flow rate of the carrier gas 111 may be set as appropriate depending on a size of a substrate 33 and a size of the film-forming unit 30, and can be set to about 0.01 to 100 L/min, for example.

[0071] Although not illustrated, it is also possible to further add a dilution gas to adjust proportions of a raw material mist 22 and the carrier gas 111. A flow rate of the dilution gas may be set as appropriate, and can be set to 0.1 to 10 times of the flow rate of the carrier gas, for example. The dilution gas is preferably supplied to a downstream side of the atomizer 20, for example. The dilution gas to be used may be the same as or different from the carrier gas 111.

(Atomizer 20)

[0072] Inside the atomizer 20, the raw material solution 21 is housed as a raw material. The raw material solution 21 is not particularly limited as long as the solution can be atomized (also referred to as atomized into a mist), and an aqueous solution containing a raw material according to its purpose, or an organic solvent solution such as alcohols, ketones, esters, ethers, amides, halogenated solvents, and aromatic compounds can be applied.

[0073] The raw material solution 21 is atomized by using a known technique to form the raw material mist 22.

[0074] The carrier gas 111 is supplied to the atomizer 20 and mixed with the raw material mist 22 to form the gas mixture 112.

[0075] The atomization of the raw material solution 21 is not particularly limited as long as the raw material solution 21 can be atomized into a mist or formed into droplets, and may be performed in a known manner. In the present invention, ultrasonic waves are preferably used. The mist or droplet obtained using ultrasonic waves is preferable because they have zero initial velocity and float in the air. For example, the mist can be conveyed as a gas floating in a space, rather than sprayed, without damage due to collision energy, and thus very suitable. A size of the droplet is not particularly limited, and may be a few millimeters. The size is preferably 50 m or less, and more preferably 0.1 to 10 m.

[0076] The atomizer 20 can include a temperature control unit (not shown). The temperature control unit may directly or indirectly control a temperature of the raw material solution 21, or may perform heat exchange using a liquid or gas heating medium, or may apply Peltier effect.

[0077] Known heating mediums can widely be used as the heating medium. For example, a liquid heating medium such as water, glycols, alcohols, and silicon oils, or a gas heating medium such as air, helium, and fluorocarbons is suitably used.

(Film-Forming Unit 30)

[0078] As illustrated in FIG. 1, the film-forming unit 30 includes the deposition chamber 31 and a heater 34.

[0079] Inside the deposition chamber 31, a susceptor 32 having a triangular shape in side view is disposed.

[0080] On an inclined surface of the susceptor 32, the substrate 33 is placed.

[0081] The pipe 102 is coupled to one wall of the deposition chamber 31 while the pipe 103 is coupled to the other wall of the deposition chamber 31. The gas mixture 112 is conveyed through the pipe 102 and supplied to the deposition chamber 31.

[0082] The deposition chamber 31 is not particularly limited as long as it has sufficient stability against the raw material solution 21 to be used and a use temperature, and may be made of resin, metal, glass, ceramic, or a combination of these materials according to its purpose.

[0083] The film formation may be performed under any condition of an atmospheric pressure, an increased pressure, and a reduced pressure, but preferably performed under an atmospheric pressure in view of an apparatus cost and productivity.

[0084] FIG. 2 illustrates one configuration of the susceptor of the film-forming apparatus according to the present invention. FIG. 2 illustrates one configuration of the susceptor, where the gas mixture 112 always flows in one direction (y direction) on the susceptor 32.

[0085] As illustrated in FIG. 2, the susceptor 32 includes a circular placement section 32b at the center of the plane. The placement section 32b allows the substrate 33 to be placed thereon.

(Susceptor Structure and Material)

[0086] A structure, a material, etc. of the susceptor 32 are not particularly limited, and may has sufficient stability according to a property of the raw material solution 21 to be used and temperature conditions.

[0087] The structure of the susceptor 32 may include a mechanism (not shown) for holding the substrate 33. In this case, a known method for holding a substrate, such as a vacuum chuck, a mechanical clamp, or an electrostatic chuck, is applicable.

[0088] As the material for the susceptor 32, metals such as aluminum and stainless steel may be used. In a case of forming a film at a higher temperature exceeding heat resistance temperature of these metals, or in a case of using an acidic or alkaline raw material, alloys such as Hastelloy (registered trademark), or ceramics such as soda-lime glass, borosilicate glass, quarts, silicon carbide, silicon nitride, and aluminum nitride may be used.

[0089] In a lower portion of the susceptor 32 adjacent to the placement section 32b, a smooth section 32a is disposed. The smooth section 32a is installed upstream of the placement section 32b, that is, on the side where the gas mixture 112 flows into the susceptor 32, and is adjacent to the placement section 32b. The smooth section 32a has a smooth surface.

[0090] Through the smooth section 32a, at least a part of the gas mixture 112 flows. In other words, a part of the gas mixture 112 supplied to the deposition chamber 31 directly flows in a straight line to a surface of the substrate 33, and the other is supplied to the surface of the substrate 33 along the smooth section 32a. In the course of this process, the gas mixture 112 reacts on the substrate 33 and a film is formed on the substrate 33.

[0091] The smooth section 32a is preferably disposed so as to include at least an area in contact with both ends of the placement section 32b (or alternatively, the substrate (not shown)) in x direction. This makes it possible to supply the gas mixture 112 to the substrate surface while constantly keeping the gas mixture 112 as a laminar flow, thereby enabling stable and favorable crystal growth on the substrate surface.

[0092] A surface roughness (arithmetic mean roughness) Ra_cor of the smooth section 32a is defined as 200 m or less. This can make the gas mixture 112, that is supplied to the surface of the substrate 33 along the smooth section 32a, a flow with less turbulence, thereby allowing stable formation of a uniform film with high quality.

[0093] When the surface roughness (arithmetic mean roughness) Ra_cor of the smooth section 32a exceeds 200 m, the gas mixture becomes turbulence, causing significant adhesion of particles or cloudy appearance due to abnormal growth. Cloudiness is microscopically observed as various recesses and protrusions with abnormal growth of the film surface, as shown in FIGS. 7 and 8, for example. Such abnormal growth is often caused by abnormal nucleation due to adhesion of a foreign substance or uneven composition of a film. Macroscopically, the degree thereof can be visually determined in most cases, or can be quantified by measuring reflectance or transmittance of visible ray or measuring recesses and protrusions on the surface, for example. Known methods can widely be applied to such measurement, and a common spectrophotometer, stylus surface shape measurement system, or atomic force microscope is suitably used. Particularly, when the thin film is transparent in the visible light range, it can be determined based on regular reflectance of visible light incident on the film surface at a certain angle. Specifically, in a case of gallium oxide, for example, the regular reflectance can be 15% or less under conditions of an incident light wavelength of 633 nm and an incident angle of 45, for example. Note that the regular reflectance refers to a ratio of energy of incident light to reflected light when light incident on a sample (film) surface from a light source is reflected and received by a light-receiving probe at a reflection angle equal to an incident angle.

[0094] Note that particle in the present invention includes the one incorporated into a film and integrated with the film and the one attached to a film surface as a foreign substance. The particle refers to the one determined as a particle when observed on a film surface, and can be measured using light scattering, for example. The surface roughness (arithmetic mean roughness) Ra_cor of the smooth section 32a is preferably 150 m or less. A lower limit thereof is not particularly limited, and can be 0.1 nm, for example.

[0095] The surface roughness (arithmetic mean roughness) Ra refers to a value calculated based on JIS B 0601 using measurement results of surface profile by a stylus method, an atomic force microscope (AFM) method, or a non-contact measurement method using a laser microscope or confocal microscope, such as optical interferometry, confocal microscopy, and an image synthesis method with focus movement.

[0096] A material used for the smooth section 32a may be the same as or different from the material for the susceptor. Specifically, aluminum, stainless steel, alloys such as Hastelloy (registered trademark), or ceramics such as soda-lime glass, borosilicate glass, quarts, silicon carbide, silicon nitride, and aluminum nitride may be used.

[0097] Smoothness of such smooth section 32a is easily obtained, for example, in a case of borosilicate glass, by lapping the surface with diamond abrasive grain, and thereafter further giving a mirror finish by chemical mechanical polishing (CMP) using colloidal silica.

[0098] Furthermore, the smooth section 32a may be maintained at a lower temperature than that of the substrate placement section 32b. This can prevent the raw material mist from evaporating on the surface of the smooth section 32a, thereby reducing particle generation due to the evaporated mist and further maintaining smoothness of the smooth section 32a for a longer period of time. In this case, the temperature of the smooth section 32a may be optimized as appropriate depending on the kind of the raw material mist and various conditions thereof for film formation. In a case of using water as a solvent for the raw material mist, in general, the temperature is preferably set to about 30 C. to 100 C. A method for cooling the smooth section 32a is not particularly limited and a known temperature control technique can be applied. For example, a coolant (not shown) may be brought into contact with the inside or back face of the smooth section 32a to perform heat exchange, or a Peltier element may be used for cooling.

(Substrate)

[0099] The substrate 33 is capable of supporting a film to be formed.

[0100] A material for the substrate 33 is not particularly limited, and may be a known material, or may be an organic compound, an inorganic simple substance, or an inorganic compound. Examples thereof include, but are not limited to, polysulfone, polyethersulfone, polyphenylene sulfide, polyetheretherketone, polyimide, polyetherimide, fluororesin, metals such as iron, aluminum, stainless steel, and gold, silicon, sapphire, quarts, glass, calcium carbonate, lithium tantalate, lithium niobate, gallium oxide, SiC, ZnO, GaN, and the like.

[0101] Regarding a size of the substrate 33, an area thereof is preferably 5 cm.sup.2 or more, more preferably 10 cm.sup.2 or more, and a thickness thereof is preferably 50 to 2000 m, more preferably 100 to 800 m.

[0102] The substrate 33 has a circular shape in plan view, as can be inferred from the shape of the placement section illustrated in FIG. 2. However, the shape is not limited thereto, and may be a rectangular or polygonal shape in plan view.

[0103] Note that when the shape or size of the substrate 33 is changed, the shape or size of the placement section 32b will be changed according to the shape or size of the substrate 33.

(Smoothness of Substrate)

[0104] A surface roughness (arithmetic mean roughness) Ra_sub of the surface of the substrate 33 is preferably equal to or less than the surface roughness (arithmetic mean roughness) Ra_cor of the surface of the smooth section 32a. This makes it possible to maintain the gas mixture as a laminar flow even on the substrate surface. When 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 section 32a, abnormal growth is more likely to occur on the substrate 33.

[0105] The surface roughness (arithmetic mean roughness) Ra_sub of the surface of the substrate 33 is preferably a value of 0.05 nm or more and 1 m or less, for example.

[0106] Such smoothness of the surface of the substrate 33 can easily be obtained, for example, in a case of sapphire, by lapping, with diamond abrasive grain, the surface of the substrate 33 obtained by processing crystal, and thereafter further giving a mirror finish by chemical mechanical polishing (CMP) using colloidal silica.

[0107] Next, one form of a flow of the gas mixture toward the substrate placed on the susceptor of the film-forming apparatus according to the present invention will be described with reference to FIG. 6, from the viewpoints of an inflow direction of the gas mixture and difference in height between the substrate and the susceptor.

(Inflow Direction of Gas Mixture)

[0108] In the film-forming apparatus according to the present invention, the substrate 33 is placed on the substrate placement section 32b disposed in the susceptor 32, and a part of the gas mixture 112 flows along the smooth section 32a toward the substrate 33.

[0109] On this occasion, an angle between the inflow direction of the gas mixture 112 and the smooth section 32a is not particularly limited.

[0110] However, the angle e is preferably 0 or more and 60 or less. When the angle exceeds 60, the gas mixture 112 collides with the susceptor 32 or the upper surface of the substrate 33 to cause turbulence, which may partially cause generation of powder and adhesion thereof to the film surface. When the angle e is 0 or more and 60 or less, such generation can be reduced. The angle is more preferably 0 or more and 45 or less.

[0111] Note that the angle e in the configuration of FIG. 1 can also be regarded as an inclination angle of the smooth section 32a with respect to the horizontal plane.

(Difference in Height)

[0112] Difference in height h between the surface of the substrate 33 and the surface of the smooth section 32a is not particularly limited, but preferably-1 mm or more and 1 mm or less. The difference in height h within such range leads to improved thickness uniformity at the edge of the substrate and no generation of turbulence at the edge. If there is a step of 1 mm or more, a film thickness distribution may occur, particularly near the edge of the substrate adjacent to the smooth section 32a.

[0113] The positive or negative numerical value as described herein indicates the relative position of the substrate surface with respect to the surface of the smooth section. The negative value indicates that the substrate surface is recessed with respect to the surface of the smooth section, while the positive value indicates that the substrate surface is protruding with respect to the surface of the smooth section.

[0114] When the substrate surface is at a higher level than the surface of the smooth section, the gas mixture concentrates at the edge of the substrate, resulting in a thicker film thickness. Conversely, when the substrate surface is at a lower level than the surface of the smooth section, the step causes the flow of the gas mixture to pass over the edge of the substrate, resulting in a thinner film thickness. Additionally, such structure may cause turbulence in the flow of the gas mixture.

[0115] The thickness of the film formed on the substrate can be measured by every known method. For example, ellipsometry, optical interference spectroscopy, a stylus method, a laser displacement method, or the like is suitably used.

(Exhaust Unit 40)

[0116] The surplus gas mixture 112 not contributing to the film formation and byproducts generated during the reaction of the gas mixture 112 on the substrate 33 are sucked by the exhaust unit 40 as the gas mixture after the film formation and discharged outside the system.

[0117] The exhaust air from the exhaust unit 40 may be treated as necessary using an abatement device such as a particle collector, a combustion device, and a scrubber (not shown), or may be treated with a filter for recovering the raw material, or may be treated with a combination thereof.

[0118] Although FIG. 1 illustrates the configuration in which one atomizer 20 is used, the film-forming apparatus according to the present invention is not limited thereto and a plurality of atomizers 20 connected in series or parallel can also be used. In this case, each atomizer 20 for use may contain a different raw material solution from each other or contain the same raw material solution. Additionally, each raw material solution may be individually atomized and independently supplied to the film-forming unit 30, or a plurality of kinds of raw material mists may be premixed and then supplied to the film-forming unit 30.

[0119] Although FIGS. 1 and 2 each illustrates the configuration in which the gas mixture 112 flows in one direction from the supply side to the exhaust side of the deposition chamber 31 relative to the substrate 33, the present invention is not limited thereto and can be configured according to the supply method of the gas mixture 112 to the substrate.

Method for Forming Film

[0120] Next, the method for forming a film according to the present invention will be described with reference to FIGS. 1 and 2.

[0121] The method for forming a film according to the present invention includes a raw material mist forming step, a gas mixture forming step, a substrate placing step, a film forming step, and a discharge step.

(Raw Material Mist Forming Step)

[0122] The raw material mist forming step is a step of atomizing the raw material solution 21 into a mist to form the raw material mist 22.

(Gas Mixture Forming Step)

[0123] The gas mixture forming step is a step of mixing the raw material mist 22 and the carrier gas 111 to form the gas mixture 112.

(Substrate Placing Step)

[0124] The substrate placing step is a step of placing the substrate 33 on the placement section 32b of the susceptor 32.

(Film Forming Step)

[0125] The film forming step is a step of supplying the gas mixture 112 from the atomizer 20 to the substrate 33 and forming a film by thermal reaction on the substrate 33.

[0126] In this step, at least a part of the gas mixture 112 is supplied from the smooth section 32a adjacent to the placement section 32b to the surface of the substrate 33, the smooth section 32a having the surface roughness (arithmetic mean roughness) Ra_cor of 200 m or less.

(Discharge Step)

[0127] The discharge step is a step of discharging the gas mixture 112 after the film formation through the exhaust unit 40.

[0128] Such method for forming a film is capable of stably producing a high-quality film on the surface of the large-diameter substrate 33, since it can maintain the gas mixture 112 containing the raw material mist 22 as a laminar flow while supplying the same to the substrate 33, thereby reducing generation of powder and abnormal growth.

[0129] The surface roughness of the smooth section 32a is preferably 150 m or less. This enables more stable production of a film with higher quality.

[0130] The difference in height h between the surface of the smooth section 32a and the surface of the substrate 33 is preferably-1 mm or more and 1 mm or less. Such method for forming a film can more stably maintain the gas mixture 112 as a laminar flow, thereby stably and uniformly producing a high-quality film.

[0131] The angle between the surface of the smooth section 32a and the flowing direction of the gas mixture 112 into the smooth section 32a is preferably 0 or more and 60 or less. Such method for forming a film can more stably maintain the gas mixture 112 as a laminar flow, thereby more stably producing a high-quality film.

SECOND EMBODIMENT

[0132] A second embodiment has the same configuration as the first embodiment except that the susceptor 32 illustrated in FIG. 3(a) is used, and the film formation is performed by intermittently rotating the susceptor 32 by 180 degrees.

[0133] In this case, as illustrated in FIG. 3(a), the gas mixture 112 is supplied to the placement section 32b from the top and bottom of the page, and accordingly, the smooth section 32a is formed in each inflow direction of the gas mixture 112.

[0134] This configuration also makes it possible to supply the gas mixture 112 to the surface of the substrate as a laminar flow.

THIRD EMBODIMENT

[0135] A third embodiment has the same configuration as the first embodiment, except that the susceptor 32 illustrated in FIG. 3(b) is used, a nozzle (not shown) configured to eject the gas mixture 112 is opposite the susceptor 32, and the film formation is performed by changing the relative position between the nozzle and the susceptor 32 in a uniaxial direction.

[0136] In this case, as illustrated in FIG. 3(b), the gas mixture 112 is supplied to the placement section 32b from the top and bottom of the page, and accordingly, the smooth section 32a is formed in each inflow direction of the gas mixture. The smooth section 32a may at least include an area surrounded by an ejection port width W and a movable length L of the nozzle, excluding the placement section 32b.

[0137] The ejection port width W in this case may be equal to or longer than a width of the substrate parallel to W, and can be, for example, 1.0 times or more and twice or less of the width of the substrate. More preferably, the ejection port width W may be 1.1 times or more and 1.5 times or less in order to more stably and easily reduce deterioration in the film thickness distribution due to discontinuity in the mist concentration that is likely to occur at the nozzle end.

[0138] Additionally, while the movable length L depends on a shape and a configuration of the nozzle to be used, it may generally be equal to or longer than a width of the substrate parallel to L. The movable length L can be, for example, 1.0 times or more and 1.5 times or less of the width of the substrate, and more preferably 1.2 times or less from the viewpoint of productivity.

[0139] This configuration also makes it possible to supply the gas mixture 112 to the surface of the substrate as a laminar flow.

FOURTH EMBODIMENT

[0140] A fourth embodiment has the same configuration as the first embodiment except that the susceptor 32 with the smooth section 32a surrounding the placement section 32b as illustrated in FIG. 4 is used, and the film formation is performed by continuously rotating the susceptor 32 relative to the gas mixture 112 flowing in one direction.

[0141] As illustrated in FIG. 4, the film formation is performed by continuously rotating the susceptor 32 relative to the gas mixture 112 flowing in one direction. This configuration also makes it possible to supply the gas mixture 112 to the surface of the substrate as a laminar flow.

FIFTH EMBODIMENT

[0142] A fifth embodiment has the same configuration as the first embodiment except that the susceptor 32 with the smooth section 32a surrounding the placement section 32b as illustrated in FIG. 5 is used, and the film formation is performed by supplying the gas mixture 112 to the secured susceptor 32 as a rotational flow. As illustrated in FIG. 5, the film formation is performed by supplying the gas mixture 112 to the secured susceptor 32 as a rotational flow. This configuration also makes it possible to supply the gas mixture 112 to the surface of the substrate as a laminar flow.

[0143] For the susceptor 32 in the first to fifth embodiments, the exemplified configurations include the circular placement section 32b corresponding to the circular substrate 33. However, the susceptor of the film-forming apparatus according to the present invention is not limited thereto, and the placement section can have a shape corresponding to the shape of the substrate as previously described.

[0144] In the first to fifth embodiments, the substrate 33 is mounted with the film formation surface facing up, but not limited thereto. A configuration in which the substrate 33 is mounted with the film formation surface facing down is also possible.

(Semiconductor Apparatus)

[0145] The method for forming a film according to the present invention can be applied to any film type of a metal film, a semiconductor film, and an insulator film, and particularly, it can suitably be used for producing a semiconductor film. Furthermore, a semiconductor film and a laminate obtained by the method for forming a film according to the present invention have reduced defects such as particles and abnormal growth and excellent electrical properties, and are industrially useful.

[0146] Such film and laminate can suitably be used for a semiconductor apparatus, etc. Furthermore, a crystal layer formed as a part of the laminate may be used as it is (in a state of the laminate), or may be applied to a semiconductor apparatus etc. after debonded from the crystal substrate, etc. by a known method.

[0147] Moreover, a semiconductor apparatus can be classified into a horizontal element (horizontal device) in which electrodes are formed on one side of a semiconductor layer, and a vertical element (vertical device) in which electrodes are provided on both of front and back sides of a semiconductor layer. At least a part of the laminate according to the present invention can suitably be used for both of horizontal and vertical devices. Particularly, it is preferably used for a vertical device.

[0148] Examples of the semiconductor apparatus 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), a light-emitting diode (LED), etc.

(-Gallium Oxide Film)

[0149] An example of the film formed by the method for forming a film according to the present invention is an -gallium oxide film.

[0150] A specific example of the -gallium oxide film is the one formed on approximately an entire surface of a c-plane sapphire substrate having a diameter of 4 inches or more, wherein the -gallium oxide film has a half width of an x-ray diffraction rocking curve peak of a (0006) plane of 9.5 seconds or less, and a film thickness distribution of +9% or less.

[0151] Incidentally, approximately an entire surface as described herein refers to 80% or more of the total area of the substrate surface.

[0152] This enables the -gallium oxide film to have good crystal orientation, a favorable film thickness distribution, and high quality.

[0153] Incidentally, the smaller half width of the rocking curve is more preferable, and thus a lower limit thereof exceeds 0 seconds, for example.

[0154] Additionally, an example of the film thickness distribution is a value obtained by using a known method such as optical interference spectroscopy to calculate film thickness at a plurality of points on the film surface, and dividing a difference between maximum and minimum values by a doubled average value.

[0155] Furthermore, although not particularly limited, an upper limit of the diameter of the c-plane sapphire substrate is about 12 inches (about 30 cm), for example.

[0156] An alternative example is an -gallium oxide film to be formed on approximately an entire surface of a c-plane sapphire substrate having a diameter of 4 inches or more, wherein a foreign substance density in the -gallium oxide film is 1.1 cm.sup.2 or less, and a film thickness distribution of the -gallium oxide film is +9% or less.

[0157] This enables the -gallium oxide film to be formed on approximately an entire surface of a large-diameter substrate, with a low foreign substance density and high quality. The foreign substance herein refers to a convex object on the film surface, particularly including both of a particle and an abnormally grown grain, and can be detected by a known wafer defect inspection apparatus.

[0158] Note that the lower foreign substance density is more preferable and thus a lower limit thereof is 0 cm-2, for example.

[0159] Furthermore, although not particularly limited, an upper limit of the diameter of the c-plane sapphire substrate is about 12 inches, for example.

EXAMPLE

[0160] Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. However, the present invention is not limited thereto.

Example 1

[0161] In the film-forming apparatus of FIG. 1, an -gallium oxide film was formed according to the following procedure.

[0162] In the film-forming apparatus, a gas cylinder filled with nitrogen gas was used to supply a carrier gas. The gas cylinder was coupled to an atomization device by a tube made of urethan resin, and the atomization device was further coupled to a deposition chamber by a pipe made of quarts.

[0163] Firstly, a c-plane single crystal sapphire substrate having a thickness of 0.65 mm and a diameter of 4 inches (about 10 cm) was placed on a susceptor made of SiC having the surface structure of FIG. 2 and the inclination angle () of 35.

[0164] In this event, the difference in height h between the surface of the smooth section and the surface of the substrate was 0 mm.

[0165] Note that the surface roughness (arithmetic mean roughness) Ra_cor of the smooth section disposed in the susceptor was measured at 5 points in the plane of the smooth section by AFM (Nanosurf Nanite AFM), and an average value of 0.55 m was obtained. Additionally, the surface roughness (arithmetic mean roughness) Ra_sub of the above sapphire substrate was measured at 5 points in a cruciform direction passing through the center of the substrate by AFM, and an average value of 0.08 nm was obtained.

[0166] Next, as a raw material solution, hydrochloric acid at a concentration of 34% was added to a diluted hydrochloric acid aqueous solution at a volume ratio of 1%, gallium acetylacetonate was dissolved therein in a proportion of 0.05 mol/L, and the resultant was loaded into the atomization device (atomizer).

[0167] Then, ultrasonic vibration was propagated by an ultrasonic vibration plate through water to the raw material solution in the atomization device, thereby atomizing the raw material solution (into a mist).

[0168] Next, nitrogen gas was added to the container of the raw material solution inside the atomization device (atomizer) at a flow rate of 20 L/min to form a gas mixture of the mist and the nitrogen gas.

[0169] Next, heating was performed such that a temperature of the substrate placed on the placement section of the susceptor became 450 C.

[0170] Next, the gas mixture was supplied to the deposition chamber and film formation was performed for 60 minutes.

[0171] Thereafter, the supply of the nitrogen gas was stopped to stop the supply of the gas mixture to the deposition chamber.

[0172] The film thus formed had clear and bright appearance in an area excluding 5 mm of an outer peripheral width of the film-formed surface.

[0173] The film was confirmed to be -phase Ga.sub.2O.sub.3 (-gallium oxide film) by X-ray diffraction measurement (Rigaku SmartLab).

[0174] At 5 points in the cruciform direction passing through the center of the substrate, rocking curve of the -Ga.sub.2O.sub.3 (0006) plane was measured, and the half width was evaluated. Note that upon the rocking curve measurement, a four-crystal monochromator that combines two channel-cut crystals was used to increase monochromaticity of x-ray to enable the measurement with higher precision. Other measurement conditions are as follows.

Measurement Conditions

[0175] Measurement apparatus: SmartLab manufactured by Rigaku

Holdings Corporation

[0176] Analysis Conditions:
Measurement method: rocking curve measurement ( scan) [0177] X-ray generation unit: anticathode Cu: [0178] output 45 KV 200 mA [0179] Detection unit: semiconductor detector [0180] Incident optical system: Ge (220) channel-cut monochromator [0181] Soller slit: incident side: [0182] light receiving side 5.0 [0183] Slit: incident side IS=1 (mm): [0184] length limitation 0.5 (mm): [0185] light receiving side RS1=1 RS2=1.1 (mm) [0186] Scanning conditions: evaluated diffraction surface Ga.sub.2O.sub.3 (006): [0187] scanning axis [0188] scanning mode step measurement [0189] scanning range 18 to 22 [0190] step width 0.005 [0191] cumulative time 0.5 sec./step

[0192] Additionally, a density of a foreign substance (having a diameter of 0.3 m or more) in the area excluding 5 mm of the outer peripheral width of the film-formed surface was evaluated using substrate inspection equipment (KLA candela-CS10). Note that the foreign substance herein refers to a convex object on the film surface, particularly including both of a particle and an abnormally grown grain.

[0193] Thereafter, thickness of the fabricated film was measured at 21 points on the film surface by optical interference spectroscopy (Filmetrics F50), and a film thickness distribution was calculated by dividing a difference between maximum and minimum values by a doubled average value.

Example 2

[0194] A film was formed in the same manner as in Example 1 except that the surface roughness (arithmetic mean roughness) Ra_cor of the smooth section in Example 1 was changed to 183 m.

[0195] The film thus formed had clear and bright appearance in an area excluding 5 mm of an outer peripheral width of the film-formed surface, and was confirmed to be -phase Ga.sub.2O.sub.3 by X-ray diffraction measurement. Subsequently, the film was evaluated in the same manner as in Example 1.

Comparative Example 1

[0196] A film was formed in the same manner as in Example 1 except that the surface roughness (arithmetic mean roughness) Ra_cor of the smooth section in Example 1 was changed to 220 m.

[0197] Slight cloudiness in appearance of the film thus formed was recognized from the outer periphery of the substrate adjacent to the smooth section to the inner side. The film was confirmed to be -phase Ga.sub.2O.sub.3 by X-ray diffraction measurement. Subsequently, the film was evaluated in the same manner as in Example 1.

Example 3

[0198] A film was formed in the same manner as in Example 1 except that the difference in height h in Example 1 was changed to 0.85 mm (the substrate surface was at a higher level than the surface of the smooth section). The film thus formed had clear and bright appearance in an area excluding 5 mm of an outer peripheral width of the film-formed surface, and was confirmed to be -phase Ga.sub.2O.sub.3 by X-ray diffraction measurement. Subsequently, the film was evaluated in the same manner as in Example 1.

Example 4

[0199] A film was formed in the same manner as in Example 1 except that the difference in height h in Example 1 was changed to 0.85 mm (the substrate surface was at a lower level than the surface of the smooth section).

[0200] The film thus formed had clear and bright appearance in an area excluding 5 mm of an outer peripheral width of the film-formed surface, and was confirmed to be -phase Ga.sub.2O.sub.3 by X-ray diffraction measurement. Subsequently, the film was evaluated in the same manner as in Example 1.

Comparative Example 2

[0201] A film was formed in the same manner as in Example 1 except that the surface roughness (arithmetic mean roughness) Ra_cor of the smooth section in Example 1 was changed to 220 m, and further the difference in height h was changed to 1.2 mm.

[0202] Cloudiness in appearance of the film thus formed was recognized in a wide range from the outer periphery of the substrate adjacent to the smooth section to the inner side. The film was confirmed to be -phase Ga.sub.2O.sub.3 by X-ray diffraction measurement. Subsequently, the film was evaluated in the same manner as in Example 1.

Comparative Example 3

[0203] A film was formed in the same manner as in Example 1 except that the surface roughness (arithmetic mean roughness) Ra_cor of the smooth section in Example 1 was changed to 220 m, and further the difference in height h was changed to 1.2 mm.

[0204] Cloudiness in appearance of the film thus formed was recognized in a wide range from the outer periphery of the substrate adjacent to the smooth section to the inner side. The film was confirmed to be -phase Ga.sub.2O.sub.3 by X-ray diffraction measurement. Subsequently, the film was evaluated in the same manner as in Example 1.

Example 5

[0205] A film was formed in the same manner as in Example 1 except that the inclination angle () in Example 1 was changed to 55.

[0206] The film thus formed had clear and bright appearance in an area excluding 5 mm of an outer peripheral width of the film-formed surface, and was confirmed to be -phase Ga.sub.2O.sub.3 by X-ray diffraction measurement. Subsequently, the film was evaluated in the same manner as in Example 1.

Comparative Example 4

[0207] A film was formed in the same manner as in Example 1 except that the surface roughness (arithmetic mean roughness) Ra_cor of the smooth section in Example 1 was changed to 220 m, and further the inclination angle () was changed to 80.

[0208] Cloudiness in appearance of the film thus formed was recognized in a wide range from the outer periphery of the substrate adjacent to the smooth section to the inner side. The film was confirmed to be -phase Ga.sub.2O.sub.3 by X-ray diffraction measurement. Subsequently, the film was evaluated in the same manner as in Example 1.

Example 6

[0209] A film was formed in the same manner as in Example 1 except that the surface roughness (arithmetic mean roughness) Ra_cor of the smooth section in Example 1 was changed to 200 m.

[0210] The film thus formed had clear and bright appearance in an area excluding 5 mm of an outer peripheral width of the film-formed surface, and was confirmed to be -phase Ga.sub.2O.sub.3 by X-ray diffraction measurement. Subsequently, the film was evaluated in the same manner as in Example 1.

Example 7

[0211] A film was formed in the same manner as in Example 1 except that the surface roughness (arithmetic mean roughness) Ra_cor of the smooth section in Example 1 was changed to 150 m.

[0212] The film thus formed had clear and bright appearance in an area excluding 5 mm of an outer peripheral width of the film-formed surface, and was confirmed to be -phase Ga.sub.2O.sub.3 by X-ray diffraction measurement. Subsequently, the film was evaluated in the same manner as in Example 1.

[0213] Table 1 shows the evaluation results in Examples 1, 2, 3, 4, 5, 6, and 7, as well as Comparative Examples 1, 2, 3, and 4.

TABLE-US-00001 TABLE 1 Half Foreign Film Ra_cor h Appear- width substance thickness [m] [mm] [] ance [sec] [cm.sup.2] distribution Ex. 1 0.55 0 35 Clear 9.1 0.33 3.6% bright Ex. 2 183 0 35 Clear 8.7 0.80 4.0% bright Comp. 220 0 35 Cloudy 67.3 17 15.3% Ex. 1 Ex. 3 0.55 0.85 35 Clear 9.1 0.91 8.7% bright Ex. 4 0.55 0.85 35 Clear 9.2 0.88 8.5% bright Comp. 220 1.20 35 Cloudy 121.2 153 25.2% Ex. 2 Comp. 220 1.20 35 Cloudy 108.0 149 22.0% Ex. 3 Ex. 5 0.55 0 55 Clear 8.8 0.6 4.5% bright Comp. 220 0 80 Cloudy 87.4 250 19.2% Ex. 4 Ex. 6 200 0 35 Clear 9.5 1.05 5.3% bright Ex. 7 150 0 35 Clear 8.6 0.74 3.7% bright

[0214] The films formed by the method for forming a film according to the present invention demonstrated the low half width (good crystal orientation), stable film growth performed with the favorable film thickness distribution, and the foreign substance density reduced to a low level. In contrast, the film formation by the conventional methods resulted in the deteriorated crystal orientation with cloudiness due to abnormal growth, and obvious increase in the film thickness distribution and the foreign substance density. It is believed that the increase in the surface roughness of the smooth section caused turbulence in the gas mixture flow, and as a result, the abnormal growth due to abnormal nucleation and adhesion of the foreign substances due to precipitation of the raw material solids were accelerated.

[0215] The above results have revealed that the present invention can provide a film-forming apparatus capable of stably producing a film with higher quality as compared with the conventional techniques.

[0216] The present description includes the following embodiments.

[0217] [1]: A method for forming a film, comprising the steps of: [0218] atomizing a raw material solution into a mist to form a raw material mist; [0219] mixing the raw material mist and a carrier gas to form a gas mixture; [0220] placing a substrate on a placement section of a susceptor; [0221] supplying the gas mixture from an atomizer to the substrate to perform film formation by thermal reaction on the substrate; and [0222] discharging the gas mixture after the film formation through an exhaust unit, [0223] wherein in the step of supplying the gas mixture from the atomizer to the substrate to perform film formation by thermal reaction on the substrate, at least a part of the gas mixture is supplied from a smooth section adjacent to the placement section to a surface of the substrate, the smooth section having a surface roughness of 200 m or less.

[0224] [2]: The method for forming a film according to the above [1], wherein the surface roughness is 150 m or less.

[0225] [3]: The method for forming a film according to the above [1] or [2], wherein difference in height between a surface of the smooth section and the surface of the substrate placed on the placement section is 1 mm or more and +1 mm or less.

[0226] [4]: The method for forming a film according to any one of the above [1] to [3], wherein an angle between a surface of the smooth section and a flowing direction of the gas mixture into the smooth section is 0 or more and 60 or less.

[0227] [5]: A film-forming apparatus, comprising: [0228] a carrier gas supplier configured to supply a carrier gas; [0229] an atomizer configured to atomize a raw material solution into a mist to generate a raw material mist; [0230] a film-forming unit configured to supply a gas mixture of the raw material mist and the carrier gas to a substrate to perform film formation; and [0231] a heater capable of heating the substrate, [0232] wherein the film-forming unit has a susceptor comprising a placement section on which the substrate is placed, [0233] the susceptor comprises a smooth section adjacent to the placement section, through which at least a part of the gas mixture flows, and [0234] the smooth section has a surface roughness of 200 m or less.

[0235] [6]: The film-forming apparatus according to the above [5], wherein the surface roughness is 150 m or less.

[0236] [7]: The film-forming apparatus according to the above [5] or [6], wherein difference in height between a surface of the smooth section and a surface of the substrate placed on the placement section is 1 mm or more and +1 mm or less.

[0237] [8]: The film-forming apparatus according to any one of the above [5] to [7], wherein an angle between a surface of the smooth section and a flowing direction of the gas mixture into the smooth section is 0 or more and 60 or less.

[0238] [9]: A susceptor comprising a placement section on which a substrate is placed in a film-forming apparatus, the film-forming apparatus comprising: a carrier gas supplier configured to supply a carrier gas; an atomizer configured to atomize a raw material solution into a mist to generate a raw material mist; a film-forming unit configured to supply a gas mixture of the raw material mist and the carrier gas to the substrate to perform film formation; and a heater capable of heating the substrate, [0239] wherein a smooth section through which at least a part of the gas mixture flows is disposed adjacent to the placement section, and [0240] the smooth section has a surface roughness of 200 m or less.

[0241] [10]: The susceptor according to the above [9], wherein the surface roughness is 150 m or less.

[0242] [11]: The susceptor according to the above [9], wherein the smooth section has the surface roughness of 200 m or less, and difference in height between a surface of the smooth section and a surface of the substrate placed on the placement section is 1 mm or more and +1 mm or less.

[0243] [12]: An -gallium oxide film to be formed on approximately an entire surface of a c-plane sapphire substrate having a diameter of 4 inches or more, wherein the -gallium oxide film has a half width of an x-ray diffraction rocking curve peak of a (0006) plane of 9.5 seconds or less, and a film thickness distribution of +9% or less.

[0244] [13]: An -gallium oxide film to be formed on approximately an entire surface of a c-plane sapphire substrate having a diameter of 4 inches or more, wherein a foreign substance density is 1.1 cm.sup.2 or less, and a film thickness distribution is +9% or less.

[0245] It should be noted that the present invention is not limited to the above-described embodiments. The embodiments are just examples, and any examples that substantially have the same feature and demonstrate the same functions and effects as those in the technical concept disclosed in claims of the present invention are included in the technical scope of the present invention.