FILM FORMATION APPARATUS AND METHOD FOR MANUFACTURING SEMICONDUCTOR DEVICE

A film formation apparatus includes a stage, a heater, a mist supply source, a superheated vapor supply source, and a delivery device. The stage is configured to allow a substrate to be mounted thereon. The heater is configured to heat the substrate. The mist supply source is configured to supply mist of a solution that comprises solvent and a film material dissolved in the solvent. The superheated vapor supply source is configured to supply a superheated vapor of a same material as the solvent. The delivery device is configured to deliver the mist and the superheated vapor toward a surface of the substrate to grow a film containing the film material on the surface of the substrate.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims the benefit of priority from Japanese Patent Application No. 2021-132611 filed on Aug. 17, 2021. The entire disclosures of the above application are incorporated herein by reference.

TECHNICAL FIELD

The technique disclosed herein relates to a film formation apparatus and a method for manufacturing a semiconductor device.

BACKGROUND

It has been proposed a film formation apparatus configured to grow a film on a surface of a substrate. The film formation apparatus supplies mist of a solution that includes a solvent and a material of the film dissolved in the solvent, and heated gas to the surface of the substrate, so the film is grown on the surface of the substrate.

SUMMARY

The present disclosure describes a film formation apparatus, which is capable of heating mist more efficiently, and a method for manufacturing a semiconductor device using the film formation apparatus.

DETAILED DESCRIPTION

To begin with, a relevant technology will be described only for understanding the embodiments of the present disclosure.

It has been proposed a film formation apparatus configured to grow a film on a surface of a substrate. The film formation apparatus supplies mist of a solution that includes a solvent and a material of the film dissolved in the solvent, and heated gas to the surface of the substrate, so the film is grown on the surface of the substrate. In such a configuration, the mist can be heated by the heated gas while suppressing evaporation of the solvent from the mist. Since the heated mist is supplied to the surface of the substrate, the temperature drop of the substrate can be suppressed. Accordingly, the film can be epitaxially grown on the surface of the substrate with stable quality.

In such a technique, however, a heating efficiency of the mist by the heated gas may not be so high. The present disclosure provides a technique which is capable of heating the mist more efficiently.

According to an aspect of the present disclosure, a film formation apparatus may include: a stage configured to allow a substrate to be mounted thereon; a heater configured to heat the substrate; a mist supply source configured to supply mist of a solution that includes a solvent and a film material dissolved in the solvent; a superheated vapor supply source configured to supply a superheated vapor of a same material as the solvent; and a delivery device configured to deliver the mist and the superheated vapor toward the surface of the substrate to grow a film containing the film material on the surface of the substrate.

The superheated vapor means a gas having a temperature higher than a boiling point.

In such a film formation apparatus, the mist and the superheated vapor are delivered toward the surface of the substrate. When the mist and the superheated vapor are delivered toward the surface of the substrate, the mist is heated by the superheated vapor. The molecular energy of the superheated vapor is much higher than that of saturated vapor (i.e., a gas having a temperature equal to the boiling point) because the energy of latent heat is required to raise the temperature of vapor to be higher than the temperature of the boiling point. Therefore, the mist can be more efficiently heated by means of the superheated vapor than the saturated vapor. That is, the mist can be efficiently heated by the superheated vapor while suppressing the evaporation of the solvent from the mist. Accordingly, the film formation apparatus described above enables the film to be grown on the surface of the substrate with more stable quality.

According to an aspect of the present disclosure, a method for manufacturing a semiconductor device is for manufacturing a semiconductor device using a film formation apparatus. The film formation apparatus: includes a stage configured to allow a substrate to be mounted thereon; a heater configured to heat the substrate; a mist supply source configured to supply mist of a solution that includes a solvent and a film material dissolved in the solvent; a superheated vapor supply source configured to supply a superheated vapor of a same material as the solvent; and a delivery device configured to deliver the mist and the superheated vapor toward the surface of the substrate. The method includes delivering the mist and the superheated vapor toward the surface of the substrate to grow a film containing the film material on the surface of the substrate.

According to the manufacturing method described above, the film can be grown on the surface of the substrate with more stable quality.

According to an aspect of the present disclosure, a film formation apparatus may be configured to epitaxially grow the film on the surface of the substrate.

According to an aspect of the present disclosure, in the film formation apparatus, the solvent may be H2O and the superheated vapor may be a superheated water vapor.

According to an aspect of the present disclosure, in the film formation apparatus, the superheated water vapor may have a mass velocity G and a temperature T that satisfy a relation of T<530G−0.15at a confluence position where the superheated water vapor and the mist are merged.

According to such a configuration, the heating efficiency of the mist by the superheated water vapor can be further increased.

According to an aspect of the present disclosure, in the film formation apparatus, the temperature of the superheated water vapor may be lower than 175 degrees Celsius (° C.).

According to an aspect of the present disclosure, in the film formation apparatus, the temperature of the superheated water vapor may be lower than 150° C.

According to an aspect of the present disclosure, in the film formation apparatus, a pressure in a flow path through which the superheated water vapor flows may be lower than the atmospheric pressure, and the temperature of the superheated water vapor may be lower than 100° C.

As described above, when the pressure in the flow path is lower than the atmospheric pressure, the boiling point of water is lower than 100° C., so that the temperature of the superheated water vapor can be lower than 100° C.

According to an aspect of the present disclosure, the delivery device may have a mixing flow path that allows a mixture of the mist and the superheated vapor to flow. The mixture may be delivered to the surface of the substrate through the mixing flow path.

In an embodiment of the present disclosure, the delivery device may have a first flow path and a second flow path provided separately from the first flow path. The mist may be delivered to the surface of the substrate through the first flow path. The superheated vapor may be delivered to the surface of the substrate through the second flow path.

According to an aspect of the present disclosure, in the film formation apparatus, the superheated vapor source may be configured to generate the superheated vapor by heating a liquid material made of the same material as the solvent to a first temperature lower than the boiling point of the liquid material, and then lowering the boiling point of the liquid material to the temperature lower than the first temperature by reducing the pressure of the liquid material.

According to such a configuration, a large amount of superheated vapor can be generated in a short time.

Embodiments of the present disclosure will be described more in detail with reference to the drawings.

First Embodiment

As shown inFIG.1, a film formation apparatus of a first embodiment is configured to epitaxially grow a film on a surface of a substrate12. The film formation apparatus of the first embodiment is used for manufacturing a semiconductor device having an epitaxially grown film. The film formation apparatus of the first embodiment includes a film formation furnace15, a mist generation reservoir20, and a superheated water vapor generator80.

A susceptor16is arranged in the film formation furnace15. The susceptor16has a horizontally arranged flat top surface. The susceptor16is configured to allow the substrate12to be mounted thereon. The susceptor16incorporates a heater14therein. The heater14heats the substrate12. The susceptor16is rotatable about its central axis. As the susceptor16rotates, the substrate12on the susceptor16rotates within the plane.

The mist generation reservoir20is a closed container. The mist generation reservoir20is configured to store a solution21in which a raw material of the film to be epitaxially grown on the surface of the substrate12is dissolved in water (H2O). For example, in the case of epitaxially growing a film of gallium oxide (Ga2O3), a solution in which gallium is dissolved in water can be used as the solution21. For example, a raw material (for example, ammonium fluoride or the like) for imparting an n-type or p-type dopant to the gallium oxide film may be further dissolved in the solution21. For example, hydrochloric acid may be contained in the solution21. In the mist generation reservoir20, a space26is provided between a surface21aof the solution21and an upper surface of the mist generation reservoir20. An ultrasonic vibrator28is installed at a bottom surface of the mist generation reservoir20. The ultrasonic vibrator28is configured to apply ultrasonic waves to the solution21stored in the mist generation reservoir20. When the ultrasonic waves are applied to the solution21, the surface21aof the solution21vibrates, and a mist of the solution21(hereinafter referred to as a solution mist72) is generated in the space26above the solution21. An upstream end of a solution mist supply path24is connected to the upper surface of the mist generation reservoir20. A downstream end of a carrier gas supply path22is connected to an upper part of an outer peripheral wall of the mist generation reservoir20. An upstream end of the carrier gas supply path22is connected to a carrier gas supply source (not shown). The carrier gas supply path22is configured to introduce a carrier gas23from the carrier gas supply source into the space26in the mist generation reservoir20. The carrier gas23is, for example, an inert gas such as nitrogen. The carrier gas23that has been introduced into the space26from the carrier gas supply path22flows from the space26to the solution mist supply path24. At this time, a solution mist72in the space26flows to the solution mist supply path24together with the carrier gas23.

The solution mist supply path24extends to the inside of the film formation furnace15. A downstream end of the solution mist supply path24is formed with a nozzle34extending toward the upper surface of the susceptor16. The solution mist72that has flowed to the downstream end of the solution mist supply path24is discharged from the nozzle34toward the upper surface of the substrate12on the susceptor16.

The superheated water vapor generator80has a water storage reservoir60and a heating furnace40.

The water storage reservoir60is a closed container. The water storage reservoir60stores water, more specifically, pure water (H2O)61. A space66is provided between a surface61aof the water61and an upper surface of the water storage reservoir60. An ultrasonic vibrator68is installed at a bottom surface of the water storage reservoir60. The ultrasonic vibrator68is configured to apply ultrasonic waves to the water61stored in the water storage reservoir60. When ultrasonic waves are applied to the water61, the surface61aof the water61vibrates, and mist of the water61(hereinafter referred to as water mist70) is generated in the space66above the water61. An upstream end of the water mist supply path64is connected to the upper surface of the water storage reservoir60. A downstream end of a carrier gas supply path62is connected to an upper part of an outer peripheral wall of the water storage reservoir60. An upstream end of the carrier gas supply path62is connected to a carrier gas supply source (not shown). The carrier gas supply path62is configured to introduce a carrier gas63from the carrier gas supply source into the space66in the water storage reservoir60. The carrier gas63is, for example, an inert gas such as nitrogen. The carrier gas63that has been introduced into the space66from the carrier gas supply path62flows from the space66into the water mist supply path64. At this time, the water mist70in the space66flows to the water mist supply path64together with the carrier gas63.

The heating furnace40is a tubular furnace extending from an upstream end40ato a downstream end40b. A heater44is arranged outside the heating furnace40. The heater44is a heating wire type heater and is arranged along an outer peripheral wall of the heating furnace40. The heater44heats the outer peripheral wall of the heating furnace40, thereby heating an inside of the heating furnace40. A downstream end of the water mist supply path64is connected to the upstream end40aof the heating furnace40. An upstream end of the superheated water vapor supply path42is connected to the downstream end40bof the heating furnace40. The water mist70and the carrier gas63are introduced into the heating furnace40from the water mist supply path64. The water mist70and the carrier gas63flow through the heating furnace40from the upstream end40ato the downstream end40b. The water mist70and the carrier gas63are heated inside the heating furnace40. While flowing through the heating furnace40, the water mist70evaporates, and turns into water vapor. The pressure inside a flow path through which the water vapor generated in the heating furnace40flows, that is, the pressure inside the heating furnace40, the superheated water vapor supply path42, and the film formation furnace15is substantially atmospheric pressure. In the heating furnace40, the water vapor is heated to a temperature higher than 100° C., that is, the boiling point of water under atmospheric pressure. Therefore, a superheated water vapor43is generated in the heating furnace40. The superheated water vapor43flows from the heating furnace40into the superheated water vapor supply path42. The superheated water vapor43is a superheated vapor made of the same material as water (H2O), which is the solvent of the solution21.

The superheated water vapor supply path42extends to the inside of the film formation furnace15. A downstream end of the superheated water vapor supply path42is formed with a nozzle32extending toward the upper surface of the susceptor16. The superheated water vapor43that has flowed to the downstream end of the superheated water vapor supply path42is discharged from the nozzle32toward the upper surface of the substrate12on the susceptor16.

Next, a film formation method using the film formation apparatus of the first embodiment will be described. Here, a semiconductor substrate that is composed of a single crystal of p-type gallium oxide (β-Ga2O3) is used as the substrate12. Further, an aqueous solution that contains water and gallium chloride (GaCl3, Ga2Cl6) dissolved in the water is used as the solution21. Moreover, nitrogen gas is used as the carrier gas23and63.

First, the substrate12is installed on the susceptor16. Next, the substrate12is heated by the heater14while rotating the susceptor16. When the temperature of the substrate12has stabilized, the ultrasonic vibrator68is activated so as to generate the water mist70in the space66of the water storage reservoir60. Further, the carrier gas63is introduced from the carrier gas supply path62into the water storage reservoir60. The water mist70thus flows into the heating furnace40through the water mist supply path64, and the superheated water vapor43is generated in the heating furnace40. The superheated water vapor43flows into the nozzle32through the superheated water vapor supply path42. As such, the superheated water vapor43is discharged from the nozzle32toward the upper surface of the substrate12. Further, the ultrasonic vibrator28is activated substantially at the same time as the ultrasonic vibrator68is activated. As a result, the solution mist72is generated in the space26of the mist generation reservoir20. Further, the carrier gas23is introduced from the carrier gas supply path22into the mist generation reservoir20. The solution mist72thus flows into the nozzle34through the solution mist supply path24. As such, the solution mist72is discharged from the nozzle34toward the upper surface of the substrate12.

The superheated water vapor43discharged from the nozzle32and the solution mist72discharged from the nozzle34merge together above the substrate12. The nozzle32and the nozzle34are configured such that an angle between a discharge direction of the nozzle32and a discharge direction of the nozzle34is less than 90°. Therefore, a relative velocity Vr of the superheated water vapor43and the solution mist72at a confluence position is lower than a flow velocity V43of the superheated water vapor43discharged from the nozzle32. The superheated water vapor43and the solution mist72are mixed at a position above the substrate12. Thus, a mixture of the superheated water vapor43and solution mist72is supplied to the upper surface of the substrate12.

When the superheated water vapor43and the solution mist72are mixed, the solution mist72is heated by the superheated water vapor43. Since the superheated water vapor43has high energy, the solution mist72can be efficiently heated.

When the mixture of the superheated water vapor43and the solution mist72is discharged toward the upper surface of the substrate12, the solution mist72adheres to the upper surface of the substrate12. Because the temperature of the substrate12is higher than the temperature of the solution mist72, the solution mist72(that is, the solution21) causes a chemical reaction on the substrate12. As a result, β-type gallium oxide (β-Ga2O3) is generated on the substrate12. Because the solution mist72is continuously supplied to the surface of the substrate12, a gallium oxide film grows on the upper surface of the substrate12. A single crystal gallium oxide film epitaxially grows on the surface of the substrate12. A semiconductor device can be manufactured by using the gallium oxide film thus formed. In a case where the solution21contains a raw material for the dopant, the dopant is incorporated into the gallium oxide film. For example, in a case where the solution21contains ammonium fluoride (NH4F), a gallium oxide film doped with fluoride is formed.

When adhering to the upper surface of the substrate12, the solution mist72removes heat from the substrate12. At this time, if the temperature of the substrate12decreases, the film quality of a gallium oxide film is likely to deteriorate. In the first embodiment, on the other hand, since the solution mist72has been heated by the superheated water vapor43, it is less likely that the solution mist72will remove heat from the substrate12when the solution mist72adheres to the upper surface of the substrate12. Therefore, the substrate12can be stably maintained at an appropriate temperature. As a result, the gallium oxide film can be suitably grown epitaxially on the upper surface of the substrate12.

When the water, that is, the solvent evaporates from the solution mist72during heating of the solution mist72, the concentration of the solution21constituting each droplet of the solution mist72increases. If the concentration of the solution21constituting each droplet changes as described above, it becomes difficult to control the characteristics of the film to be grown. Further, if the water excessively evaporates from the solution21constituting each droplet, the solution21changes into solid fine particles. If such solid fine particles are generated, the solid fine particles adhere to the film to be grown and the film quality is likely to deteriorate. However, in the film formation apparatus of the present embodiment, since the solution mist72is heated by the superheated water vapor43, the partial pressure of the water vapor is high around the solution mist72, and it is less likely that the water will evaporate from the solution mist72. Therefore, the solution21having an appropriate concentration can be supplied to the upper surface of the substrate12as the solution mist72. As a result, a high-quality film can be grown on the upper surface of the substrate12.

When water is heated by a gas, an evaporation rate S (kg/(m2·hr)) of water is different depending on the type of gas, a mass velocity G (kg/(m2·hr)) of the gas, and the temperature T (° C.) of the gas. The mass velocity G is the mass of the gas flowing per unit time when the gas is applied toward the water.FIG.2shows the evaporation rate S of the water when the water in a stationary state is heated by a gas (air or superheated water vapor). As shown inFIG.2, the evaporation rate S of air and the evaporation rate S of the superheated water vapor increase with an increase in the mass velocity G. Further, the evaporation rate S of each mass velocity G increases with an increase in the temperature T. A rate of increase in the evaporation rate S of each mass velocity G with respect to the temperature T (that is, the slope of the graph) is larger in the superheated water vapor than in the air. Therefore, in each mass velocity G, there is a reversal point temperature Tr in which the magnitude of the evaporation rate S is reversed between the superheated water vapor and the air. That is, in regard to each mass velocity G, when the temperature T is lower than the reversal point temperature Tr, the evaporation rate S of the superheated water vapor is smaller than that of the air, and when the temperature T is higher than the reversal point temperature Tr, the evaporation rate S of the superheated water vapor is higher than the air. Therefore, in the case where the water is heated by the superheated water vapor, if the temperature T of the superheated water vapor is lower than the reversal point temperature Tr, the water can be heated more efficiently. From the experimental results ofFIG.2, the reversal point temperature Tr can be regarded as a function of the mass velocity G. The reversal point temperature Tr satisfies a relation of Tr=530G−0.15. Therefore, if the superheated water vapor is in the temperature range satisfying T<530G−0.15, the water can be heated while effectively suppressing the evaporation of the water.

In the film formation apparatus of the first embodiment, a mass velocity G43and the temperature T43of the superheated water vapor43discharged from the nozzle32satisfy a relation of T43<530G43−0.15. As described above, the relative velocity Vr of the superheated water vapor43and the solution mist72at the confluence position of the superheated water vapor43and the solution mist72is lower than the flow velocity V43of the superheated water vapor43discharged from the nozzle32. Therefore, the mass velocity Gr of the superheated water vapor43with respect to the solution mist72at the confluence position is lower than the mass velocity G43of the superheated water vapor43discharged from the nozzle32. As such, if the relation of T43<530G43−0.15is satisfied, the relation of T43<530Gr−0.15is satisfied. In the film formation apparatus of the first embodiment, therefore, the temperature T43of the superheated water vapor43at the confluence position can be set to a temperature lower than the reversal point temperature Tr. Accordingly, in the film formation apparatus of the first embodiment, the solution mist72can be heated by the superheated water vapor43while effectively suppressing the evaporation of water from the solution mist72. The temperature T43may be lower than 175° C. By setting the temperature T43to be lower than 175° C., the temperature T43can be set to be equal to or lower than the reversal point temperature within the range of a practical mass velocity Gr. In particular, the temperature T43may be lower than 150° C.

In the first embodiment, the superheated water vapor supply path42and the solution mist supply path24are separate. However, as shown inFIG.3, the superheated water vapor supply path42and the solution mist supply path24may be merged at their downstream positions to form a mixing flow path45. A downstream end of the mixing flow path45is formed with a nozzle30extending toward the upper surface of the substrate12. In this configuration, the superheated water vapor43and the solution mist72merge at an upstream end of the mixing flow path45. The superheated water vapor43and the solution mist72are mixed in the mixing flow path45to form a mixture73. The mixture73is discharged from the nozzle30toward the upper surface of the substrate12. Even in this configuration, the solution mist72can be heated by the superheated water vapor43while suppressing the evaporation of water from the solution mist72. In this case, the temperature T43and the mass velocity G43of the superheated water vapor43are set so as to satisfy the relationship of T43<530G43−0.15at the confluence position of the superheated water vapor43and the solution mist72, that is, at the upstream end of the mixing flow path45. As a result, the evaporation of water from the solution mist72can be suppressed more effectively.

Second Embodiment

A second embodiment will be described with reference toFIG.4. In a film formation apparatus of the second embodiment shown inFIG.4, a superheated water vapor generator80includes a liquid material vaporization system90and a refill system92. Other configurations of the film formation apparatus of the second embodiment are the same as those of the film formation apparatus ofFIG.3. The refill system92supplies water to the liquid material vaporization system90. The liquid material vaporization system90sequentially executes a heat treatment and a pressure reduction treatment on the water supplied from the refill system92. In the heat treatment, the liquid material vaporization system90heats the water under a pressure P1higher than the atmospheric pressure. In this case, the liquid material vaporization system90heats the water to a temperature that is below the boiling point. In the pressure reduction treatment, the liquid material vaporization system90reduces the pressure applied to the water from the pressure P1to a pressure P2. With this, the boiling point of the water drops to a temperature lower than the temperature of the water. That is, the water is brought into a state in which the temperature of the water is higher than the boiling point. As a result, the water evaporates rapidly and superheated water vapor43is generated.

For example, in the heat treatment, in a state where the water is applied with the pressure P1at which the boiling point of water is about 130° C., the water can be heated to 120° C., which is higher than 100° C. and lower than the boiling point (that is, about 130° C.). After that, when the water is transferred under the pressure P2which is substantially equal to the atmospheric pressure, the boiling point of the water drops to about 100° C. Thus, the temperature of the water (about 120° C.) is higher than the boiling point (about 100° C.), so that the water evaporates rapidly. As a result, the superheated water vapor43having a temperature higher than the boiling point (about 100° C.) is generated.

As described above, according to the method of lowering the boiling point of water by reducing the pressure, the superheated water vapor43can be generated more rapidly than the method of simply heating water.

The superheated water vapor43generated by the liquid material vaporization system90is sent to the mixing flow path45via the superheated water vapor supply path42. Further, the solution mist72generated in the mist generation reservoir20is sent to the mixing flow path45via the solution mist supply path24. In the mixing flow path45, the superheated water vapor43and the solution mist72are mixed. A mixture73of the superheated water vapor43and the solution mist72is discharged from the nozzle30toward the upper surface of the substrate12. Therefore, similarly to the film formation apparatus ofFIG.3, the film can be efficiently grown on the upper surface of the substrate12.

In the configuration in which the superheated water vapor43and the solution mist72are mixed in the mixing flow path45as shown inFIG.4, since the heating time of the solution mist72by the superheated water vapor43is long, the solution mist72can be uniformly heated. On the other hand, if the heating time is long, the water evaporates from the solution mist72and the concentration of the solution21constituting the solution mist72is likely to change. In the second embodiment, when the superheated water vapor43having a temperature lower than 150° C. is used, the number of water molecules that aggregate in the solution mist72and the number of water molecules that evaporate from the solution mist72are easily balanced. Therefore, the change in the concentration of the solution21constituting the solution mist72can be suppressed.

In the second embodiment, the superheated water vapor supply path42and the solution mist supply path24may be separated as inFIG.1.

Third Embodiment

A third embodiment of the present disclosure will be described with reference toFIG.5. As shown inFIG.5, in a firm formation apparatus of the third embodiment, the mixture73of the superheated water vapor43and the solution mist72is supplied to the nozzle30. The nozzle30has a rectangular parallelepiped shape that is elongated in one direction. The nozzle30has a plurality of discharge ports30aon a lower surface. The discharge ports30aare arranged in line. The nozzle30discharges the mixture73from each discharge port30atoward the susceptor16. Further, in the third embodiment, a plurality of substrates12can be placed on the susceptor16. The substrates12are arranged around the central axis16aof the susceptor16. As shown by arrows81, the mixture73discharged downward from the nozzle30is able to impinge on an entirety of a diameter of the susceptor16. The susceptor16rotates around the central axis16a. Further, in the third embodiment, an exhaust pump98is installed at an exhaust port of the film formation furnace15. By activating the exhaust pump98, the pressure inside the film formation furnace15is reduced. That is, in the third embodiment, the pressure inside the film formation furnace15is lower than the atmospheric pressure.

When the susceptor16is rotated while discharging the mixture73from the nozzle30, the mixture73flows laminar along the upper surfaces of the substrates12. Therefore, the gallium oxide film can be uniformly grown on the upper surface of each substrate12.

Further, in the third embodiment, since the pressure in the film formation furnace15is lower than the atmospheric pressure, the boiling point of the water in the film formation furnace15is lower than 100° C. For example, the pressure in the film formation furnace15can be controlled so that the boiling point of water in the film formation furnace15is about 80° C. Moreover, in the third embodiment, the temperature of the superheated water vapor43supplied from the nozzle30into the film formation furnace15is higher than the boiling point of water in the film formation furnace15and lower than 100° C. For example, the temperature of the superheated water vapor43supplied into the film formation furnace15can be about 90° C. As described above, even the water vapor having the temperature lower than 100° C. can become superheated water vapor in a pressure-reduced atmosphere. Even in this configuration, the solution mist72can be heated by the superheated water vapor43while suppressing the evaporation of water from the solution mist72. Therefore, the film can be favorably grown epitaxially.

Also in the first and second embodiments, the pressure in the flow path through which the superheated water vapor43flows may be lower than the atmospheric pressure, in the similar manner to the third embodiment. In this case, the temperature of the superheated water vapor43can be made lower than 100° C.

In each of the embodiments described above, the solvent of the solution21is water. As another example, a liquid other than water may be used as the solvent. In such a case, the solution mist can be heated by a superheated vapor, which is made of the same material as the solvent.

In each of the embodiments described above, the gallium oxide film is epitaxially grown on the upper surface of the substrate. As another example, other films may be epitaxially grown. In addition, a film may be grown by a growth method other than the epitaxial growth.

The susceptor16of each of the embodiments is an example of a stage. The mist generation reservoir20of each of the embodiments is an example of a mist supply source. The superheated water vapor generator80of each of the embodiments is an example of a superheated vapor supply source. The superheated water vapor supply path42, the solution mist supply path24, and the mixing flow path45of each of the embodiments are examples of a delivery device. The solution mist supply path24of each of the embodiments is an example of a first flow path. The superheated water vapor supply path42of each of the embodiments is an example of a second flow path.

Although the embodiments have been described in detail above, these are merely examples and do not limit the scope of the present disclosure. The techniques described in the present disclosure include various modifications and modifications of the specific examples illustrated above. The technical elements described in the present disclosure or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the present disclosure at the time of filing. In addition, the techniques illustrated in the present specification or drawings achieve multiple objectives at the same time, and achieving one of the objectives itself has technical usefulness.