Film forming method and film forming apparatus

Abstract

To provide a film forming method and a film forming apparatus, capable of stably producing a high-quality and uniform film on a large-diameter substrate surface at low costs.SOLUTION: A film forming method using a mist CVD method includes: a step of placing a substrate on a susceptor; a step of forming a raw material mist by atomizing a raw material solution; a step of forming a gas mixture by mixing the raw material mist and a carrier gas; a first film formation step of forming a film by a thermal reaction on the substrate, by supplying the gas mixture onto the substrate while exhausting the gas mixture such that the gas mixture flows in one direction along a main surface of the substrate; and a second film formation step of forming a film by the thermal reaction on the substrate by supplying the gas mixture onto the substrate while exhausting the gas mixture such that the gas mixture flows in a direction different from the one direction along the main surface of the substrate.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a film forming method and a film forming apparatus.

Background Art

[0002] As a method capable of forming an epitaxial film or the like at low temperature and atmospheric pressure, a film forming technique using water fine particles such as a mist CVD method is known. Patent Document 1 shows an apparatus for forming a film by inclinedly installing a substrate placed on a substantially semi-circular susceptor in a horizontal furnace. Patent Document 2 shows a film forming apparatus for forming a film by horizontally supplying a raw material mist to a substrate fixed to a flat channel called a fine channel. Patent Document 3 describes a film forming method in which a raw material mist is transported into a reaction vessel by a carrier gas, and a swirling flow is further generated to react the mist with a substrate. Further, Patent Document 4 shows a film forming apparatus in which a film forming nozzle having a raw material solution ejection part and an exhaust part is arranged to face the film forming surface of a substrate, and film formation is performed while moving parallel to the substrate.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in conventional film-forming apparatuses that perform mist supply in a certain direction to a stationary substrate as disclosed in Patent Documents 1 to 3, there has been a problem that the thickness distribution of the film formed on the substrate becomes extremely large. Particularly for films used in semiconductor device applications, a film thickness distribution of at least 10% or less within the substrate plane is generally required from the perspective of performance yield. Therefore, it has been difficult to satisfy this condition with the above conventional method, and it has been useless especially for substrates with a practical size of 10 cm or more in diameter.

[0005] Also, the nozzle method as disclosed in Patent Document 4, although it could solve the above problems, not only made the device structure complicated for transporting the nozzle or the substrate, but also required additional measures to prevent dust generation and contamination from the sliding parts associated with this transport mechanism, resulting in a problem that the device became extremely expensive. Further, in the nozzle method, the nozzle moves relative to the substrate, but since the mist supply temporarily stops after the nozzle passes, the film growth rate decreases compared to the conventional technologies of Patent Documents 1 to 3, and there has been a problem that productivity significantly decreases. Moreover, a state occurs where the substrate goes against the mist flow due to the relative reciprocating movement of the nozzle, which may generate turbulent flow and cause a decrease in yield due to abnormal growth such as foreign matter adhesion and cloudiness.

[0006] The present invention has been made to solve the above problems, and an object thereof is to provide a film-forming method and a film-forming apparatus capable of stably and at low cost manufacturing a high-quality and uniform film on the surface of a large-diameter substrate.

Means for Solving the Problems

[0007] The present invention is made to achieve the above object, and is a film forming method by a mist CVD method, comprising: a step of placing a substrate on a susceptor; a step of atomizing a raw material solution to form a raw material mist; a step of mixing the raw material mist and a carrier gas to form a mixture; a first film forming step of exhausting while supplying the mixture to the substrate so that the mixture flows in one direction along the main surface of the substrate, and forming a film on the substrate by a thermal reaction; and a second film forming step of exhausting while supplying the mixture to the substrate so that the mixture flows in a direction different from the one direction along the main surface of the substrate, and forming a film on the substrate by a thermal reaction.

[0008] With such a film forming method, a high-quality and uniform film can be stably and inexpensively manufactured on the surface of a large-diameter substrate.

[0009] At this time, the different direction can be the reverse direction of the one direction.

[0010] Thereby, the control of the film thickness becomes easier, so that a high-quality and uniform film can be manufactured more stably.

[0011] At this time, after the first film forming step and after the second film forming step, a step of interrupting the supply of the mixture and replacing the mixture in the atmosphere in contact with the substrate with a replacement gas can be further included.

[0012] Thereby, it becomes possible to suppress the adhesion of particles generated by the turbulent flow of the mixture to the substrate, so that a higher-quality film can be stably and uniformly manufactured.

[0013] At this time, the first and second film forming steps may be repeated.

[0014] Thereby, the control of the film thickness becomes further easier, so that a high-quality and uniform film can be manufactured more stably.

[0015] The present invention also provides a film forming apparatus using a mist CVD method, comprising: atomizing means for atomizing a raw material solution to generate a raw material mist; at least first and second mixed gas supply means for supplying a mixed gas in which the raw material mist and a carrier gas are mixed to the surface of a substrate; supply switching means for switching the open / closed states of the first and second mixed gas supply means; first and second exhaust means corresponding to the first and second mixed gas supply means respectively; exhaust switching means for switching the open / closed states of the first and second exhaust means; a susceptor for placing the substrate; and heating means for heating the substrate. The first and second mixed gas supply means and the first and second exhaust means are arranged such that when the first mixed gas supply means and the first exhaust means are in an open state and the second mixed gas supply means and the second exhaust means are in a closed state, the flow path of the mixed gas passing from the first mixed gas supply means to the first exhaust means, and when the second mixed gas supply means and the second exhaust means are in an open state and the first mixed gas supply means and the first exhaust means are in a closed state, the flow path of the mixed gas passing from the second mixed gas supply means to the second exhaust means, are in different directions. A film forming apparatus is provided, which can stably and inexpensively produce a high-quality and uniform film on the surface of a large-diameter substrate with such a film forming apparatus.

[0016] With such a film forming apparatus, it becomes a film forming apparatus capable of stably and inexpensively manufacturing a high-quality and uniform film on the surface of a large-diameter substrate.

[0017] At this time, the different directions can be opposite directions.

[0018] Thereby, film thickness control becomes easier even for the surface of a large-diameter substrate, so that it becomes a film forming apparatus capable of more stably manufacturing a high-quality and uniform film.

[0019] At this time, the susceptor can be made capable of placing a plurality of substrates.

[0020] Thereby, productivity can be easily increased, so that it becomes a film forming apparatus capable of manufacturing a homogeneous film at a lower cost.

[0021] At this time, a plurality of substrates can be placed on the same surface of the susceptor, and the plurality of substrates can be placed in parallel with respect to the flow path direction of the air-fuel mixture.

[0022] As a result, it becomes easier to control the film thickness of the plurality of substrates, so that a highly productive film forming apparatus capable of stably manufacturing a high-quality and uniform film at a lower cost can be obtained.

Effect of the Invention

[0023] As described above, according to the film forming method of the present invention, a high-quality and uniform film can be stably and inexpensively manufactured on the surface of a large-diameter substrate. Further, according to the film forming apparatus of the present invention, it becomes a film forming apparatus capable of stably manufacturing a high-quality and uniform film on the surface of a large-diameter substrate at a low cost.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiment for Carrying Out the Invention

[0025] As described above, there has been a demand for a film forming method and a film forming apparatus capable of stably manufacturing a high-quality and uniform film on the surface of a large-diameter substrate at a low cost.

[0026] As a result of intensive studies on the above problems, the inventors of the present invention have found that by changing the direction of the flow of the mixed gas by opening and closing a plurality of air-fuel mixture supply means and exhaust means, a high-quality and uniform film can be stably and inexpensively formed on the surface of a large-diameter substrate, and thus the present invention has been completed.

[0027] That is, the present invention is a film-forming method by mist CVD method, comprising the steps of placing a substrate on a susceptor, atomizing a raw material solution to form a raw material mist, mixing the raw material mist and a carrier gas to form a mixed gas, supplying the mixed gas to the substrate while exhausting the mixed gas so that the mixed gas flows in one direction along the main surface of the substrate, and forming a film on the substrate by a thermal reaction; and a second film-forming step of supplying the mixed gas to the substrate while exhausting the mixed gas so that the mixed gas flows in a direction different from the one direction along the main surface of the substrate, and forming a film on the substrate by a thermal reaction.

[0028] According to such a film-forming method, a high-quality and uniform film can be stably and inexpensively formed on the surface of a large-diameter substrate.

[0029] The inventors of the present invention have also developed a film forming apparatus using a mist CVD method, which includes an atomizing means for atomizing a raw material solution to generate a raw material mist, at least first and second mixed gas supply means for supplying a mixed gas in which the raw material mist and a carrier gas are mixed to the surface of a substrate, a supply switching means for switching the open / closed states of the first and second mixed gas supply means, first and second exhaust means corresponding to the first and second mixed gas supply means respectively, an exhaust switching means for switching the open / closed states of the first and second exhaust means, a susceptor for placing the substrate, and a heating means for heating the substrate. The first and second mixed gas supply means and the first and second exhaust means are arranged such that the flow path of the mixed gas passing from the first mixed gas supply means to the first exhaust means when the first mixed gas supply means and the first exhaust means are in an open state and the second mixed gas supply means and the second exhaust means are in a closed state, and the flow path of the mixed gas passing from the second mixed gas supply means to the second exhaust means when the second mixed gas supply means and the second exhaust means are in an open state and the first mixed gas supply means and the first exhaust means are in a closed state, are in different directions. By means of this film forming apparatus, a film forming apparatus capable of stably and at low cost manufacturing a high-quality and uniform film on the surface of a large-diameter substrate has been found, and the present invention has been completed.

[0030] Hereinafter, the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto. As described above, the present invention aims to improve the uniformity of the film formed on a large-diameter substrate, but it goes without saying that the present invention can be applied regardless of the diameter of the substrate.

[0031] [Film Forming Apparatus] First, an example of the film forming apparatus according to the present invention will be described.

[0032] FIG. 1 shows a representative example of the film forming apparatus according to the present invention. However, the film forming apparatus capable of performing the film forming method according to the present invention is not limited to the film forming apparatus shown in FIG. 1.

[0033] The film forming apparatus 1 shown in Fig. 1 is a film forming apparatus by the mist CVD method, and includes a carrier gas supply means 10 for supplying a carrier gas 111, an atomizing means 20 for atomizing (hereinafter, also referred to as "mistifying") a raw material solution to generate a raw material mist, a film forming section 30, and an exhaust section 40 which are connected by supply pipes 101, 102 and an exhaust pipe 103, respectively. The mist CVD method is a film forming method that can form a film at low cost with a simple configuration without requiring special components or a vacuum.

[0034] The carrier gas 111 is not particularly limited. For example, in addition to air, oxygen, and ozone, inert gases such as nitrogen and argon, or reducing gases such as hydrogen gas and forming gas are preferably used. The type of the carrier gas 111 may be one type or two or more types. The flow rate of the carrier gas 111 may be appropriately set according to the size of the film forming section 30 and the like, and can be, for example, about 0.01 to 100 L / min.

[0035] Inside the atomizing means 20, a raw material solution 21 is stored as a raw material. The raw material solution 21 is not particularly limited as long as it is an atomizable solution, and an aqueous solution containing a raw material according to the purpose, or an organic solvent solution such as alcohols, ketones, esters, ethers, amides, halogenated solvents, and aromatic compounds can be applied.

[0036] Further, the atomizing means 20 can be provided with a temperature adjusting section (not shown in the figure). The temperature adjusting section may directly or indirectly adjust the temperature of the raw material solution, may perform heat exchange using a heat medium of a liquid or a gas, or may apply the Peltier effect. As the heat medium, known heat media can be widely used. For example, liquids such as water, glycols, alcohols, and silicone oils, or gas heat media such as air, helium, or fluorocarbons are preferably used.

[0037] In addition, although Fig. 1 shows a form in which one atomizing means 20 is used, the film forming apparatus 1 of the present invention is not limited thereto, and a plurality of atomizing means 20 may be connected in series or in parallel.

[0038] A carrier gas 111 is further supplied to the atomizing means 20 and mixed with the raw material mist 22 to form a mixture gas 211. It can be said that the carrier gas supply means 10 and the atomizing means 20 constitute a mechanism 50 for forming the mixture gas 211 of the raw material mist 22 and the carrier gas 111.

[0039] The film forming section 30 includes a film forming chamber 31, a susceptor 32, and a heating means 34. The supply pipe 102 is divided into a supply pipe 102a and a supply pipe 102b, which are respectively connected to the film forming chamber 31, and the mixture gas 211 is supplied from the supply ports 104a and 104b. The supply pipe 102a and the supply port 104a together are called the first mixture gas supply means, and the supply pipe 102b and the supply port 104b together are called the second mixture gas supply means. Further, supply switching means (supply opening / closing sections 35a, 35b) for opening and closing each pipe and switching the opening / closing states of the first and second mixture gas supply means are respectively installed in the pipes 102a and 102b.

[0040] In addition, discharge ports 105a, 105b for exhausting the mixer 211 and exhaust pipes 103a, 103b are connected to the film forming chamber 31, and the exhaust pipes 103a, 103b are connected to the exhaust pipe 103. The discharge port 105a and the exhaust pipe 103a together are called the first exhaust means, and the discharge port 105b and the exhaust pipe 103b together are called the second exhaust means. Further, exhaust switching means (exhaust opening / closing sections 36a, 36b) for opening and closing each pipe and switching the opening / closing states of the first and second exhaust means are respectively installed in the exhaust pipes 103a and 103b. Note that 33 is a substrate.

[0041] The supply pipe 102 is not particularly limited as long as it has sufficient stability with respect to the raw material solution 21 to be used, the temperature at the joint between the film forming section 30 and the supply pipe 102, etc., and can be a pipe made of resin, metal, glass, ceramic, or a combination of these materials according to the purpose.

[0042] The supply opening / closing parts 35a and 35b and the exhaust opening / closing parts 36a and 36b are not particularly limited as long as they can be stably used with respect to the process temperature, raw materials, and products derived from the raw materials, and known valves and shutters may be widely applied. Further, the supply opening / closing parts 35a and 35b and the exhaust opening / closing parts 36a and 36b may be directly or indirectly controlled by a control mechanism not shown in the figure.

[0043] The installation positions of the supply ports 104a and 104b in the film formation chamber 31 are not particularly limited, but preferably, the lower ends of the supply ports 104a and 104b are on the same horizontal plane as the film formation surface of the substrate 33, and more preferably, they are located on the ceiling side of the film formation chamber 31 relative to the film formation surface of the substrate 33. With such installation positions, while effectively preventing the formation of turbulent flow that causes dust generation (particle formation), the mixed gas 211 is supplied to the substrate 33.

[0044] Also, the installation positions of the discharge ports 105a and 105b in the film formation chamber 31 are not particularly limited, but in order to increase the raw material yield, preferably, the upper ends of the discharge ports 105a and 105b are on the same horizontal plane as the film formation surface of the substrate 33, and more preferably, they are located on the bottom side of the film formation chamber 31 relative to the film formation surface of the substrate 33.

[0045] As shown in FIG. 1, in the film forming apparatus of the present invention, the first and second mixed gas supply means and the first and second exhaust means are such that when the first mixed gas supply means and the first exhaust means are in an open state and the second mixed gas supply means and the second exhaust means are in a closed state, the flow path of the mixed gas 211a passing from the first mixed gas supply means to the first exhaust means, and when the second mixed gas supply means and the second exhaust means are in an open state and the first mixed gas supply means and the first exhaust means are in a closed state, the flow path of the mixed gas 211b passing from the second mixed gas supply means to the second exhaust means are arranged in different directions.

[0046] With such a film forming apparatus, it becomes a film forming apparatus capable of stably and at low cost manufacturing a high-quality and uniform film on the surface of a large-diameter substrate.

[0047] At this time, the different directions can be opposite directions.

[0048] As a result, the control of the film thickness becomes easy even for the surface of a large-diameter substrate, so that a film forming apparatus capable of more stably manufacturing a high-quality and uniform film is obtained.

[0049] Also, in the form of FIG. 1, one supply port 104a, 104b and one discharge port 105a, 105b are provided respectively, but the present invention is not limited to this, and more supply ports and discharge ports can be provided as necessary. Also, the shapes of the supply ports 104a, 104b and the discharge ports 105a, 105b are not particularly limited, and for example, the openings thereof may be circular, elliptical, or rectangular.

[0050] Furthermore, in the form of FIG. 1, one supply pipe 102a, 102b and one exhaust pipe 103a, 103b are provided respectively, but the present invention is not limited to this, and more supply pipes and exhaust pipes can be provided as necessary.

[0051] The substrate 33 is not particularly limited as long as it can support the film to be formed. The material of the substrate 33 is also not particularly limited and may be a known material, which may be an organic compound, an inorganic single substance, or an inorganic compound. For example, polysulfone, polyethersulfone, polyphenylene sulfide, polyetheretherketone, polyimide, polyetherimide, fluororesin, metals such as iron, aluminum, stainless steel, gold, silicon, sapphire, quartz, glass, calcium carbonate, lithium tantalate, lithium niobate, gallium oxide, SiC, ZnO, GaN, etc. can be mentioned, but it is not limited thereto. Also, in FIG. 4, a form in which the substrate 33 is circular is shown, but the shape of the substrate 33 is not limited thereto and may be rectangular or polygonal, and the area is 5 cm 2 or more preferably 10 cm 2The above-described substrate having a thickness of 50 to 2000 μm, more preferably 100 to 800 μm, can be suitably used. Further, in order to keep the mixed gas in laminar flow, the arithmetic mean roughness Ra_sub of the substrate surface is preferably equal to or less than the arithmetic mean roughness Ra_sus of the susceptor 32 surface. When Ra_sub is equal to or less than Ra_sus, the occurrence of abnormal growth on the substrate can be effectively prevented. At this time, the value of Ra_sub is preferably, for example, 0.05 nm or more and 1 μm or less.

[0052] The smoothness of the surface of such a substrate 33 can be easily obtained, for example, in the case of sapphire, by lapping the surface of the substrate 33 obtained by processing the crystal with diamond abrasive grains and then performing mirror finishing by chemical mechanical polishing (CMP) using colloidal silica.

[0053] The film formation chamber 31 and the susceptor 32 on which the substrate 33 is placed are not particularly limited as long as they have sufficient stability with respect to the raw material solution 21 to be used and the use temperature, and can be made of resin, metal, glass, ceramic, or a combination of these materials according to the purpose.

[0054] Further, the shape of the film formation chamber 31 is not particularly limited and may be a rectangular parallelepiped, polyhedron, cylinder, sphere, or a combination thereof. Also, a structure (fine channel) in which the space above and around the substrate 33 is narrowed from the outside as in the form of FIG. 2 may be used. With such a structure, the mixed gas 211 can be more easily controlled as a one-way flow.

[0055] The structure of the susceptor 32 and the like is not particularly limited, and it suffices to have sufficient stability according to the characteristics of the raw materials used and the temperature conditions. In this case, metals such as aluminum and stainless steel may be applied. When film formation is performed at a higher temperature exceeding the heat-resistant temperature of these metals, or when acidic or alkaline raw materials are used, alloys such as Hastelloy, soda-lime glass, borosilicate glass, quartz, silicon carbide, or ceramics such as silicon nitride and aluminum nitride may be applied, or a material combining these may also be used.

[0056] Also, in order to avoid the formation of turbulent flow in the mixture gas 211 flowing into the susceptor 32, the surface of the susceptor surrounding the substrate 33 is preferably smooth. Specifically, the arithmetic mean roughness Ra_sus is preferably 200 μm or less, more preferably 150 μm or less. The lower limit is not particularly limited, but it can be, for example, 0.1 nm. With an Ra_sus within such a range, it is possible to effectively prevent the mixture gas from becoming turbulent, significant particle adhesion, or the appearance of cloudiness due to abnormal growth. Cloudiness is microscopically observed as various irregularities on the film surface. Such abnormal growth is often caused by abnormal nucleation due to foreign matter adhesion or film composition bias.

[0057] The arithmetic mean roughness Ra of the surface refers to a value obtained by calculating based on JIS B 0601 using the surface shape measurement results obtained by non-contact measurement methods using a laser microscope or a confocal microscope, such as the stylus method, the atomic force microscope (AFM) method, or the optical interference method, the confocal method, and the image synthesis method by focus shift.

[0058] In addition, the height difference h between the surface of the substrate 33 and the surface of the susceptor 32 surrounding the substrate 33 is preferably 0 mm or more and 1 mm or less. When the substrate surface is higher than the surface of the susceptor 32, the mixed gas concentrates at the end of the substrate and the film thickness becomes thick. Conversely, when the substrate surface is lower than the surface of the susceptor 32, the mixed gas flow jumps over the end of the substrate due to the step, so the film thickness becomes thin. Further, such a structure causes turbulence in the flow of the mixed gas, and it is easy for particles to adhere to the film and abnormal growth to occur. However, if the height difference is within such a range, it is possible to effectively prevent the film thickness distribution from becoming significantly non-uniform particularly in the vicinity of the end of the substrate adjacent to the step, particle adhesion to the film, and abnormal growth.

[0059] In addition, although not shown in the figure, the susceptor 32 may be provided with a mechanism for holding the substrate 33. In this case, known substrate holding methods such as a vacuum chuck, a mechanical clamp, or an electrostatic chuck can be applied.

[0060] The heating means 34 heats the substrate 33, and known heating means can be widely applied, and it may be a resistance heating heater, an induction heating heater, a lamp heater, etc. As shown in the forms of FIGS. 1 and 2, it may be a cold wall method of heating the substrate through the susceptor, or a hot wall method of heating from the outside of the film forming chamber as in the form of FIG. 3 described later.

[0061] In the form described above, the substrate 33 is installed so that the film forming surface faces upward, but the film forming apparatus of the present invention is not limited to this, and the film forming surface of the substrate 33 may be installed so as to face downward or in the horizontal direction. As an example, it is also possible to adopt a form in which the substrate 33 is placed on both surfaces of the susceptor 32 as shown in FIG. 3. In this case, the susceptor 32 may be held so that the normal line in the film forming surface of the substrate 33 is perpendicular to the bottom surface of the film forming chamber 31, or may be held so as to be parallel.

[0062] As a result, productivity can be easily increased, and the film forming apparatus can manufacture a homogeneous film at a lower cost.

[0063] Further, the susceptor 32 may be capable of mounting a plurality of substrates 33 on the same surface, for example, in the form shown in FIG. 4. In this case, the supply ports 104a (104b) are linearly formed on one side surface of the film formation chamber, and the discharge ports 105a (105b) are linearly formed corresponding to the opposite side surface. In order to suppress the variation in film thickness between the substrates 33, it is preferable that the substrates 33 be mounted in parallel with respect to the flow path direction of the mixed gas 211a (211b) passing between the supply port 104a (104b) and the discharge port 105a (105b).

[0064] As a result, the control of the film thickness on a plurality of substrates becomes easier, so that a highly productive film formation apparatus capable of stably manufacturing a high-quality and uniform film at a lower cost can be obtained.

[0065] In the above, the form of forming a film on a substrate installed inside a film formation chamber to which the supply and discharge pipes of the mixed gas are connected has been described with reference to FIGS. 1 to 4. However, the apparatus of the present invention is not limited to these, and a form in which the mixed gas is supplied to the substrate by the mixed gas supply nozzle described below to form a film can also be adopted. When the film formation apparatus of the present invention is in the form of a nozzle system, compared with the conventional nozzle system, it is not necessary to use an expensive apparatus, the productivity and the yield can be improved, and the cost can be reduced.

[0066] FIG. 5 shows a form of the film formation part of a film formation apparatus by the nozzle system. In this case, the film formation nozzle 60 includes two nozzles, a nozzle having a supply port 104a and a discharge port 105b, and a nozzle having a supply port 104b and a discharge port 105a, and the two nozzles are installed to face each other via the top plate 37. Further, the substrate 33 is installed via a certain distance gap so as to face the bottom of the nozzle 60.

[0067] The shapes of the supply ports 104a and 104b and the discharge ports 105a and 105b are not particularly limited, and for example, the openings thereof may be circular, elliptical, or rectangular. However, in order to make the flows of the mixed gases 211a and 211b more uniform laminar flows, the length in the longitudinal direction of the openings of the supply ports 104a and 104b is preferably a sufficient length according to the shape of the substrate.

[0068] The installation positions of the supply ports 104a and 104b and the discharge ports 105a and 105b are not particularly limited, but preferably, the discharge ports 105a and 105b are arranged inside the two supply ports 104a and 104b. With such installation positions, deposition of solids at the openings of the supply ports 104a and 104b can be suppressed, so that stable film formation can be achieved over a longer period.

[0069] Also, the shape of the top plate 37 is not particularly limited as long as it does not disturb the flows of the mixed gases 211a and 211b, and it may be circular, elliptical, or rectangular. Preferably, it has a size sufficient to cover the film formation surface of the substrate 33.

[0070] The nozzle 60 is not particularly limited as long as it has sufficient stability with respect to the raw material solution 21 to be used and the use temperature, and it can be made of resin, metal, glass, ceramic, or a combination of these materials according to the purpose.

[0071] [Film Formation Method] Next, a film formation method by mist CVD according to the present invention will be described with reference to FIGS. 1 to 4. The mist CVD method is a film formation method that can form a film at low cost with a simple configuration without requiring special components or a vacuum.

[0072] [Step of Placing the Substrate on the Susceptor] First, the substrate 33 is placed on the susceptor 32 arranged in the film formation chamber 31.

[0073] [Step of Forming the Raw Material Mist] The raw material solution 21 is atomized within the atomizing means 20 to form a raw material mist 22. The atomization method of the raw material solution 21 is not particularly limited as long as the raw material solution 21 can be atomized or made into droplets, and it may be a known means. However, in the present invention, it is preferable to use ultrasonic waves. The mist or droplets obtained by using ultrasonic waves have an initial velocity of zero and float in the air, which is preferable. For example, instead of spraying like a spray, it is a mist that can float in space and be conveyed as a gas, so it is very suitable because there is no damage due to collision energy. The droplet size is not particularly limited and may be droplets with a diameter of about several millimeters, but is preferably 50 μm or less, and more preferably 0.1 to 10 μm.

[0074] As described above, the film forming apparatus 1 that can be used in the film forming method of the present invention can also be used by connecting a plurality of atomizing means 20 in series or in parallel. In this case, different raw material solutions may be used in each atomizing means 20, or the same raw material solution may be used. Also, each raw material solution may be atomized individually and supplied to the film forming section 30 independently, or a plurality of types of raw material mists may be mixed in advance and then supplied to the film forming section 30.

[0075] (Step of forming a mixture gas) A carrier gas 111 is further supplied to the atomizing means 20 and mixed with the raw material mist 22 to form a mixture gas 211.

[0076] Also, although not shown, it is also possible to add a dilution gas to the mixture gas 211 to adjust the ratio of the raw material mist 22 and the carrier gas 111. The flow rate of the dilution gas may be set appropriately. For example, it can be 0.1 to 10 times that of the carrier gas 111. The dilution gas may be supplied, for example, to the downstream side of the atomizing means 20. The dilution gas may be the same as the carrier gas 111 or different.

[0077] (First film forming step) The mixed gas 211 is supplied to the film forming chamber 31 through either one of the supply pipes 102a or 102b. Here, the case where the supply of the mixed gas 211 is started using the supply pipe 102a will be described. In this case, the supply opening / closing part 35b is closed and the supply opening / closing part 35a is opened by supply opening / closing part control means (not shown in the figure). Further, the exhaust opening / closing part 36b is closed and the exhaust opening / closing part 36a is opened by exhaust opening / closing part control means (not shown in the figure).

[0078] As a result, the mixed gas 211a is supplied from the supply port 104a to the film forming chamber 31, flows in one direction along the main surface of the substrate 33, and is then discharged from the discharge port 105a. During this time, film formation is performed by a thermal reaction on the substrate 33 heated by the heating means 34.

[0079] After a predetermined time has elapsed, the supply of the mixed gas to the film forming chamber 31 is stopped. The supply of the mixed gas 211 may be stopped by stopping the atomization of the raw material of the atomizing means 20, or by closing the supply opening / closing part 35a.

[0080] Also, at this time, the inside of the film forming chamber 31 may be replaced with gas. In this case, for example, the atomization of the raw material solution of the atomizing means 20 may be stopped while maintaining the supply opening / closing parts 35a, 35b and the exhaust opening / closing parts 36a, 36b in the state during the supply of the mixed gas, and the carrier gas 111 may be continuously flowed for a predetermined time. Alternatively, after closing the supply opening / closing part 35a while maintaining the atomization of the raw material solution of the atomizing means 20, a replacement gas may be supplied to the film forming chamber 31 from another pipe (not shown in the figure). Also, the gas used for the gas replacement may be the same as the carrier gas used for the mixed gas 211, or may be different.

[0081] As a result, it becomes possible to suppress the adhesion of particles generated by the turbulent flow of the mixed gas 211 to the substrate, so that a higher quality film can be stably and uniformly manufactured.

[0082] (Second film forming step) Next, the air-fuel mixture 211 is supplied from the supply pipe 102b. By the supply opening / closing control means, the supply opening / closing part 35a is closed and the supply opening / closing part 35b is opened. Further, by the exhaust opening / closing control means, the exhaust opening / closing part 36a is closed and the exhaust opening / closing part 36b is opened.

[0083] Thereby, the air-fuel mixture 211b is supplied from the supply port 104b to the film forming chamber 31, flows in a direction different from the flow path of the air-fuel mixture 211 during the first film forming step along the main surface of the substrate 33, and then is discharged from the discharge port 105b. During that time, film formation is performed by a thermal reaction on the substrate 33 heated by the heating means 34.

[0084] With such a film forming method, a high-quality and uniform film can be stably and inexpensively manufactured on the surface of a large-diameter substrate.

[0085] The supply time of the air-fuel mixture 211b is preferably made equal to the supply time of the above air-fuel mixture 211a. Thereby, it becomes possible to equalize the thickness distribution of the film formed on the surface of the substrate.

[0086] At this time, the flow path direction of the air-fuel mixture 211b is preferably the reverse direction of the flow path direction of the air-fuel mixture 211a. Thereby, since the control of the film thickness becomes easier, a high-quality and uniform film can be manufactured more stably.

[0087] After a predetermined time has elapsed, the supply of the air-fuel mixture to the film forming chamber 31 is stopped. The supply stop of the air-fuel mixture 211 may be performed by stopping the raw material atomization of the atomizing means 20, or may be performed by closing the supply opening / closing part 35b.

[0088] Also, at this time, the inside of the film formation chamber 31 may be replaced with gas. In this case, for example, while maintaining the supply opening / closing parts 35a and 35b and the exhaust opening / closing parts 36a and 36b in the state during the supply of the air-fuel mixture, the atomization of the raw material solution of the atomization means 20 may be stopped and the carrier gas 111 may be continuously flowed for a predetermined time. Alternatively, after closing the supply opening / closing part 35b while maintaining the atomization of the raw material solution of the atomization means 20, a replacement gas may be supplied to the film formation chamber 31 from another pipe not shown in the figure. Also, the gas used for gas replacement may be the same carrier gas as that used for the air-fuel mixture 211, or may be different.

[0089] Thereby, since it becomes possible to suppress the adhesion of particles generated by the turbulent flow of the air-fuel mixture 211 to the substrate, a higher-quality film can be stably and uniformly manufactured.

[0090] The film formation may be performed under any conditions of atmospheric pressure, increased pressure, and reduced pressure, but it is preferably performed under atmospheric pressure in terms of equipment cost and productivity.

[0091] In the present invention, the first and second film formation steps described above are taken as one cycle to form a uniform film on the substrate 33. This cycle may be preferably repeated 3 cycles or less from the viewpoint of productivity depending on the type of film to be produced and the manufacturing conditions, or may be one cycle. Thereby, the control of the film thickness becomes easier, so that a high-quality and uniform film can be more stably manufactured.

[0092] The surplus of the air-fuel mixture 211 that did not contribute to the film formation and the by-products generated during the reaction of the air-fuel mixture 211 on the substrate 33 are sucked by the exhaust part 40 as the air-fuel mixture after film formation and discharged out of the system. The exhaust from the exhaust part 40 may be treated by a decontamination device such as a particle collector, a mist trap, a combustion device, a scrubber, etc. not shown in the figure as necessary, or may be a filter for raw material recovery, or may be a combination of these.

[0093] The thickness of the film formed on the substrate can be measured by any known method. For example, polarization analysis, optical interference spectroscopy, stylus method, laser displacement method, etc. are preferably used.

[0094] The film forming method according to the present invention can also be implemented in a film forming apparatus equipped with a mixed supply nozzle as shown in FIG. 5 described above. When the film forming method of the present invention is in the form of a nozzle system, compared with the conventional nozzle system, it is not necessary to use an expensive apparatus, productivity and yield can be improved, and costs can be reduced.

[0095] In this case, as shown in FIG. 5, after the mixed gas 211a (211b) is discharged from the supply port 104a (104b), it flows through the gap between the substrate 33 and the bottom of the film forming nozzle 60 and is discharged from the discharge port 105a (105b). In this process, the raw material mist is supplied to the surface of the substrate 33 to form a film. After a predetermined time has elapsed, after stopping the supply of the mixed gas 211a (211b) in the same manner as in the forms from FIG. 1 to FIG. 4, the supply of the mixed gas 211b (211a) is started this time, and film formation is performed for a predetermined time.

[0096] Here, the shortest distance from the surface of the substrate to the bottom or top plate of the nozzle in the gap is not particularly limited and may be adjusted as appropriate. However, from the relationship of the raw material yield, it is preferably 1 mm to 4 cm, more preferably 3 mm to 3 cm.

[0097] When the supply of the mixed gases 211a and 211b is stopped, the space between the supply ports 104a and 104b and the nozzle 60 and the substrate may be replaced with gas. In this case, for example, while maintaining the above-described mixed gas supply and exhaust line, the atomization of the raw material solution of the atomizing means 20 is stopped and the carrier gas 111 is allowed to flow continuously for a predetermined time. Alternatively, after closing the supply opening / closing portions 35a and 35b while maintaining the atomization of the raw material solution of the atomizing means 20, a replacement gas may be supplied to the space from another supply line (not shown in the figure). The gas used for the gas replacement may be the same as or different from that used for the mixed gas 211. Thereby, it is possible to prevent the raw material mist in the mixed gas remaining in the supply ports 104a and 104b and the space from growing in the gas phase and descending onto the substrate when the supply of the mixed gas 211 is stopped.

[0098] Further, the nozzle 60 may be temperature-adjustable by temperature control means (not shown in the figure). In this case, the temperature may be appropriately adjusted according to the type of the raw material solvent, the type of the film to be formed, etc. For example, when water is used as the solvent, it is preferably set to 50°C to 90°C.

Example

[0099] Hereinafter, the present invention will be specifically described with reference to examples, which do not limit the present invention.

[0100] (Example 1) Using the film forming apparatus of FIG. 1, a gallium oxide film was formed.

[0101] For the carrier gas supply, a gas cylinder filled with nitrogen gas was used. The gas cylinder and the atomizing device were connected by a urethane resin tube, and further, the atomizing device (atomizing means) and the film forming chamber were connected by a quartz tube.

[0102] As the raw material solution, gallium acetylacetonate was dissolved in a dilute hydrochloric acid aqueous solution obtained by adding 1% by volume of hydrochloric acid with a concentration of 34% at a ratio of 0.05 mol / L, and this was filled into the atomizing device.

[0103] Next, ultrasonic vibration was propagated through water by an ultrasonic diaphragm to the raw material solution in the atomization device, and the raw material solution was atomized (mistified).

[0104] Next, a c-plane sapphire substrate (substrate) with a diameter of 10 cm and a thickness of 0.65 mm was placed on a susceptor made of SiC, and heated with a resistance heater so that the substrate temperature reached 450°C.

[0105] Next, with the supply opening / closing part 35b and the exhaust opening / closing part 36b closed, the supply opening / closing part 35a and the exhaust opening / closing part 36a were opened.

[0106] Next, nitrogen gas was added to the raw material container at a flow rate of 15 L / min, and a mixture of mist and nitrogen gas was supplied to the film formation chamber, and film formation was performed for 15 minutes.

[0107] Next, with the carrier gas supply maintained, the ultrasonic vibration of the atomization device was stopped for 1 minute to replace the gas in the film formation chamber.

[0108] Next, the supply opening / closing part 35a and the exhaust opening / closing part 36a were closed.

[0109] Next, raw material atomization was started again.

[0110] Next, the supply opening / closing part 35b and the exhaust opening / closing part 36b were opened.

[0111] Next, nitrogen gas was added to the raw material container at a flow rate of 15 L / min, and the mixture was supplied to the film formation chamber, and film formation was performed for 15 minutes.

[0112] Next, with the carrier gas supply maintained, the ultrasonic vibration of the atomization device was stopped for 1 minute to replace the gas in the film formation chamber.

[0113] After that, the heater was stopped and the substrate was cooled to room temperature.

[0114] Next, the supply opening / closing part 35b and the exhaust opening / closing part 36b were closed, and further, the supply of nitrogen gas was stopped, the supply of carrier gas to the film formation chamber was stopped, and the substrate was taken out from the film formation chamber.

[0115] The fabricated film was confirmed to be α-phase Ga2O3 by X-ray diffraction measurement (Rigaku SmartLab). After that, the thickness of the fabricated film was measured at 21 points in the film plane 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. As a result, the film thickness distribution was 2.83%.

[0116] (Comparative Example) Using a film-forming apparatus not equipped with the supply pipe 102b (supply port 104b) and the exhaust pipe 103b (exhaust port 105b), the first film formation in Example 1 was extended to 30 minutes for film formation, and film formation was carried out in the same manner as in Example 1 except that the second film formation was not performed.

[0117] After that, the substrate was cooled in the same manner as in Example 1 and taken out from the film formation chamber.

[0118] The fabricated film was evaluated by the same method as in Example 1. The crystal structure was α-phase Ga2O3, and the film thickness distribution was 46.7%.

[0119] (Example 2) Using a film-forming apparatus in which the film-forming part of FIG. 5 was applied to the film-forming apparatus of FIG. 1, a gallium oxide film was formed.

[0120] A gas cylinder filled with nitrogen gas was used for carrier gas supply. The gas cylinder and the atomizing device were connected by a urethane resin tube, and further, the atomizing device (atomizing means) and a film-forming nozzle with a PFA coating on the surface of an aluminum alloy (A5052) were connected by a quartz tube.

[0121] In addition, cooling water was circulated inside the film-forming nozzle to keep the temperature of the nozzle surface at 60°C.

[0122] As a raw material solution, gallium acetylacetonate was dissolved in a dilute hydrochloric acid aqueous solution with 1% hydrochloric acid with a concentration of 34% added by volume at a ratio of 0.05 mol / L, and this was filled into the atomizing device.

[0123] Next, ultrasonic vibration was propagated through water to the raw material solution in the atomization device by an ultrasonic diaphragm, and the raw material solution was atomized (mistified).

[0124] Next, a c-plane sapphire substrate with a diameter of 10 cm and a thickness of 0.65 mm was placed on a susceptor made of SiC, and heated with a resistance heater so that the substrate temperature reached 450°C. At this time, the shortest distance in the gap between the substrate surface and the nozzle bottom was set to 5 mm.

[0125] Next, with the supply opening / closing part 35b and the exhaust opening / closing part 36b closed, the supply opening / closing part 35a and the exhaust opening / closing part 36a were opened.

[0126] Next, nitrogen gas was added to the raw material container at a flow rate of 20 L / min, and a mixture of mist and nitrogen gas was supplied to the film formation chamber, and film formation was performed for 15 minutes.

[0127] Next, while maintaining the carrier gas supply, the ultrasonic vibration of the atomization device was stopped for 1 minute to replace the gas in the nozzle and the gap.

[0128] Next, the supply opening / closing part 35a and the exhaust opening / closing part 36a were closed.

[0129] Next, raw material atomization was started again.

[0130] Next, the supply opening / closing part 35b and the exhaust opening / closing part 36b were opened.

[0131] Next, nitrogen gas was added to the raw material container at a flow rate of 20 L / min, and the mixture was supplied to the film formation chamber, and film formation was performed for 15 minutes.

[0132] Next, while maintaining the carrier gas supply, the ultrasonic vibration of the atomization device was stopped (raw material atomization was stopped) to replace the gas in the nozzle and the gap.

[0133] Next, the supply opening / closing part 35b and the exhaust opening / closing part 36b were closed, and further supply of nitrogen gas was stopped.

[0134] After that, the heater was stopped, the substrate was cooled to room temperature, and the substrate was taken out.

[0135] The prepared film was confirmed to be α-phase Ga2O3 by X-ray diffraction measurement (Rigaku SmartLab). After that, the film thickness distribution was evaluated in the same manner as in Example 1, and further, the film formation rate was calculated by dividing the average value of the film thickness by the mixed gas supply time. As a result, the film thickness distribution was 3.11%, and the film formation rate was 1.52 μm per hour.

[0136] (Reference Example) A film formation apparatus for forming a gallium oxide film was used in the same manner as in Example 2, except that a substrate transfer mechanism was added to the film formation apparatus (Fig. 5) used in Example 2 so that the substrate position could reciprocate in a direction parallel to the flow direction of the mixed gas.

[0137] With the above substrate transfer mechanism, the mixed gas was supplied to the substrate under the same conditions as in Example 2 while reciprocating the substrate at a speed of 5 mm per second so that the supply port 104a swept the entire surface of the substrate, and film formation was carried out for 30 minutes.

[0138] After that, the supply and transfer of the mixed gas were stopped, and the substrate was cooled and taken out of the film formation chamber in the same manner as in Example 2.

[0139] The prepared film was evaluated in the same manner as in Example 2. The crystal structure was α-phase Ga2O3, the film thickness distribution was 3.80%, and the film formation rate was 0.87 μm per hour.

[0140] (Example 3) The film formation part in the form of Fig. 4 was applied to the film formation apparatus of Fig. 1, and a gallium oxide film was formed on five substrates simultaneously.

[0141] A gas cylinder filled with nitrogen gas was used for carrier gas supply. The gas cylinder and the atomizing device were connected by a urethane resin tube, and further, the atomizing device (atomizing means) and the film formation chamber were connected by a quartz tube.

[0142] As a raw material solution, gallium acetylacetonate was dissolved in a dilute hydrochloric acid aqueous solution obtained by adding 1% by volume of hydrochloric acid with a concentration of 34% at a ratio of 0.05 mol / L, and this was filled into an atomizing device.

[0143] Next, ultrasonic vibration was propagated through water to the raw material solution in the atomizing device by an ultrasonic vibrating plate to atomize (mistify) the raw material solution.

[0144] Next, five c-plane sapphire substrates with a diameter of 15 cm and a thickness of 0.65 mm were placed on the same surface of a SiC susceptor and heated with a resistance heater so that the substrate temperature reached 450°C.

[0145] Next, with the supply opening / closing part 35b and the exhaust opening / closing part 36b closed, the supply opening / closing part 35a and the exhaust opening / closing part 36a were opened.

[0146] Next, nitrogen gas was added to the raw material container at a flow rate of 90 L / min to supply a mixture of mist and nitrogen gas to the film deposition chamber, and film deposition was performed for 15 minutes.

[0147] Next, with the carrier gas supply maintained, the ultrasonic vibration of the atomizing device was stopped for 1 minute to perform gas replacement in the film deposition chamber.

[0148] Next, the supply opening / closing part 35a and the exhaust opening / closing part 36a were closed.

[0149] Next, raw material atomization was started again.

[0150] Next, with the supply opening / closing part 35a and the exhaust opening / closing part 36a closed, the supply opening / closing part 35b and the exhaust opening / closing part 36b were opened.

[0151] Next, nitrogen gas was added to the raw material container at a flow rate of 90 L / min to supply a mixture to the film deposition chamber, and film deposition was performed for 15 minutes.

[0152] Next, with the carrier gas supply maintained, the ultrasonic vibration of the atomizing device was stopped for 1 minute to perform gas replacement in the film deposition chamber.

[0153] After that, the heater was stopped and the substrate was cooled to room temperature.

[0154] Next, the supply opening / closing part 35b and the exhaust opening / closing part 36b were closed, and further, the supply of nitrogen gas was stopped to stop the supply of the carrier gas to the film formation chamber, and the substrate was taken out from the film formation chamber.

[0155] The films (samples) formed on the five substrates were evaluated by the same method as in Example 1. The crystal structure was α-phase Ga2O3 for all of them, and the film thickness distribution was as shown in Table 1.

[0156]

Table 1

[0157] As shown in Table 1, the film thickness distribution was 5% or less for all the samples.

[0158] As described above, according to the embodiment of the present invention, a film with a good film thickness distribution could be formed. On the contrary, in the comparative example (conventional film formation method), the film thickness distribution became very large. Also, in comparison with the reference example, the embodiment could form a film at a high film formation rate. It is considered that by alternately performing the supply of the raw material mist from two directions to the substrate, both a good film thickness distribution and a high film formation rate can be achieved.

[0159] From the above results, according to the present invention, a film formation method and a film formation apparatus capable of manufacturing a more homogeneous film with higher productivity than the prior art could be realized.

[0160] This specification includes the following aspects. [1]: A film forming method by mist CVD method, comprising a step of placing a substrate on a susceptor, a step of atomizing a raw material solution to form a raw material mist, a step of mixing the raw material mist and a carrier gas to form a mixed gas, and a first film forming step of exhausting while supplying the mixed gas to the substrate so that the mixed gas flows in one direction along the main surface of the substrate, and forming a film on the substrate by a thermal reaction, and a second film forming step of exhausting while supplying the mixed gas to the substrate so that the mixed gas flows in a direction different from the one direction along the main surface of the substrate, and forming a film on the substrate by a thermal reaction. [2]: The film forming method according to [1] above, wherein the different direction includes the direction opposite to the one direction. [3]: The film forming method according to [1] or [2] above, further comprising a step of interrupting the supply of the mixed gas after the first film forming step and after the second film forming step, and replacing the mixed gas in the atmosphere in contact with the substrate with a replacement gas. [4]: The film forming method according to [1], [2] or [3] above, wherein the first and second film forming steps are repeatedly performed. [5]: A film forming apparatus using the mist CVD method, comprising atomizing means for atomizing a raw material solution to generate a raw material mist, at least first and second mixed gas supply means for supplying a mixed gas in which the raw material mist and a carrier gas are mixed to the surface of a substrate, supply switching means for switching the open / closed states of the first and second mixed gas supply means, first and second exhaust means corresponding to the first and second mixed gas supply means respectively, exhaust switching means for switching the open / closed states of the first and second exhaust means, a susceptor for placing the substrate, and heating means for heating the substrate. The first and second mixed gas supply means and the first and second exhaust means are arranged such that when the first mixed gas supply means and the first exhaust means are in an open state and the second mixed gas supply means and the second exhaust means are in a closed state, the flow path of the mixed gas passing from the first mixed gas supply means to the first exhaust means, and when the second mixed gas supply means and the second exhaust means are in an open state and the first mixed gas supply means and the first exhaust means are in a closed state, the flow path of the mixed gas passing from the second mixed gas supply means to the second exhaust means, are in different directions. [6]: The film forming apparatus according to [5] above, wherein the different directions include opposite directions. [7]: The film forming apparatus according to [5] or [6] above, wherein the susceptor can place a plurality of substrates. [8]: The film forming apparatus according to [5], [6] or [7] above, wherein the susceptor can place a plurality of substrates on the same surface of the susceptor, and the plurality of substrates are placed in parallel with respect to the flow path direction of the mixed gas.

[0161] Note that the present invention is not limited to the above embodiments. The above embodiments are examples, and any device having a configuration substantially the same as the technical idea described in the claims of the present invention and exhibiting the same operational effects is included in the technical scope of the present invention.

Explanation of Reference Numerals

[0162] 10… Carrier gas supply means, 20… Atomizing means, 21… Raw material solution, 22… Raw material mist, 30… Film forming section, 31… Film forming chamber, 32… Susceptor, 33… Substrate, 34… Heating means, 35a, 35b… Supply opening / closing section, 36a, 36b… Exhaust opening / closing section, 37… Top plate, 40… Exhaust section, 50… Mechanism for forming a mixture gas, 60… Film forming nozzle, 101, 102, 102a, 102b… Supply pipes, 103, 103a, 103b… Exhaust pipes, 104a, 104b… Supply ports, 105a, 105b… Discharge ports, 111… Carrier gas, 211, 211a, 211b… Mixture gas.

Claims

1. A film forming method by mist CVD method, A step of placing a substrate on a susceptor, A step of atomizing a raw material solution to form a raw material mist, A step of mixing the raw material mist and a carrier gas to form a mixture, A first film forming step of exhausting while supplying the mixture to the substrate so that the mixture flows in one direction along the main surface of the substrate, and forming a film on the substrate by a thermal reaction, A film forming method characterized by including a second film forming step of exhausting while supplying the mixture to the substrate so that the mixture flows in a direction different from the one direction along the main surface of the substrate, and forming a film on the substrate by a thermal reaction.

2. The film forming method according to claim 1, wherein the different direction is the reverse direction of the one direction.

3. The film forming method according to claim 2, further including a step of interrupting the supply of the mixture after the first film forming step and after the second film forming step, and replacing the mixture in the atmosphere in contact with the substrate with a replacement gas.

4. The film forming method according to claim 3, wherein the first and second film forming steps are repeatedly performed.

5. A film forming apparatus by mist CVD method, Atomizing means for atomizing a raw material solution to generate a raw material mist, At least first and second mixture supply means for supplying a mixture in which the raw material mist and a carrier gas are mixed to the surface of a substrate, Supply switching means for switching the open / closed states of the first and second mixture supply means, First and second exhaust means corresponding to the first and second mixture supply means respectively, Exhaust switching means for switching the open / closed states of the first and second exhaust means, A susceptor for placing the substrate, Heating means for heating the substrate, and the first and second air-fuel mixture supply means and the first and second exhaust means are arranged such that when the first air-fuel mixture supply means and the first exhaust means are in an open state and the second air-fuel mixture supply means and the second exhaust means are in a closed state, the flow path of the air-fuel mixture passing from the first air-fuel mixture supply means to the first exhaust means, and when the second air-fuel mixture supply means and the second exhaust means are in an open state and the first air-fuel mixture supply means and the first exhaust means are in a closed state, the flow path of the air-fuel mixture passing from the second air-fuel mixture supply means to the second exhaust means, are in different directions. A film forming apparatus characterized by this.

6. The film forming apparatus according to claim 5, characterized in that the different directions are opposite directions.

7. The film forming apparatus according to claim 5, characterized in that the susceptor can place a plurality of substrates.

8. The film forming apparatus according to claim 7, characterized in that the susceptor can place a plurality of substrates on the same surface of the susceptor, and the plurality of substrates are placed in parallel with respect to the flow path direction of the air-fuel mixture.

Images