JP7473591B2 - Film forming apparatus and film forming method - Google Patents

Description

The present invention relates to a film formation apparatus and a film formation method that form a film on a substrate using a mist-like raw material.

Conventionally, high vacuum deposition apparatuses capable of realizing a non-equilibrium state, such as pulsed laser deposition (PLD), molecular beam epitaxy (MBE), and sputtering, have been developed, and it has become possible to produce oxide semiconductors that could not be produced by conventional melt methods. In addition, mist chemical vapor deposition (Mist CVD) (hereinafter also referred to as "mist CVD") has been developed, in which a mist-like raw material is used to grow crystals on a substrate, and it has become possible to produce gallium oxide (α-Ga ₂ O ₃ ) having a corundum structure. As a semiconductor with a large band gap, α-Ga ₂ O ₃ is expected to be applied to next-generation switching elements that can realize high voltage resistance, low loss, and high heat resistance.

Regarding the mist CVD method, Patent Document 1 describes a tubular furnace type mist CVD device. Patent Document 2 describes a fine channel type mist CVD device. Patent Document 3 describes a linear source type mist CVD device. Patent Document 4 describes a tubular furnace mist CVD device, which differs from the mist CVD device described in Patent Document 1 in that a carrier gas is introduced into the mist generator. Patent Document 5 describes a mist CVD device in which a substrate is placed above a mist generator and a susceptor is mounted on a hot plate as a rotating stage. Patent Document 6 describes a film formation device and a film formation method in which an aerosol is heated in a heating tower attached to a nozzle provided immediately above and adjacent to the substrate and sprayed onto the substrate to form a film.

Japanese Patent Application Laid-Open No. 1-257337 JP 2005-307238 A JP 2012-46772 A Patent No. 5397794 JP 2014-63973 A Patent No. 4841338

Unlike other CVD methods, the mist CVD method does not require high temperatures and can produce metastable crystal structures such as the corundum structure of α-gallium oxide. However, the inventors discovered a new problem in that the generated mist condenses and aggregates inside the supply pipe before being transported to the substrate (reducing the lifespan of the mist), and the condensed mist is not sent to the film formation section, reducing the film formation speed.

The present invention has been made to solve the above problems, and aims to provide a film formation apparatus that has excellent film formation speed and is applicable to the mist CVD method, and a film formation method that has excellent film formation speed.

The present invention has been made to achieve the above object, and provides a film formation device having a mist generating section that generates mist by turning a raw material solution into a mist, a carrier gas supplying section that supplies a carrier gas that transports the mist, a film formation section that heat-treats the mist to form a film on a substrate, a transport section that connects the mist generating section and the film formation section and transports the mist by the carrier gas, and a transport section heating means that heats at least a portion of the transport section.

Such a film forming device makes it possible to extend the life of the mist in the transport section and increase the film forming speed.

In this case, the film forming apparatus further has a control unit, which can control the conveying section heating means to set the temperature of the conveying section to 30 to 120°C.

This will further improve the lifespan of the mist before film formation.

The present invention also provides a film forming method for forming a film by heat-treating a mist in a film forming section, the film forming method including the steps of: generating mist by turning a raw material solution into mist in the mist forming section; heating at least a part of a transport section connecting the mist forming section and the film forming section; transporting the mist from the mist forming section to the film forming section via the transport section using a carrier gas; and heat-treating the mist in the film forming section to form a film on a substrate.

This type of film formation method can extend the life of the mist in the transport section and increase the film formation speed.

At this time, the temperature of the conveying section can be set to 30 to 120°C.

This can further improve the lifespan of the mist before film formation.

As described above, the film formation apparatus of the present invention makes it possible to greatly improve the film formation speed with a simple device configuration. Furthermore, the film formation method of the present invention makes it possible to greatly improve the film formation speed with a simple method.

1 is a schematic diagram showing an example of a film forming apparatus according to the present invention; FIG. 2 is a diagram illustrating an example of a mist generating unit used in the present invention. FIG. 4 is a schematic configuration diagram showing another example of a film forming apparatus according to the present invention. FIG. 13 is a schematic diagram showing still another example of the film forming apparatus of the present invention.

The present invention is described in detail below, but is not limited to these.

As described above, there was a demand for a film formation device capable of improving the film formation speed in the mist CVD method, and a film formation method that significantly improves the film formation speed.

After extensive research into the above-mentioned problems, the inventors discovered that a film formation device having a mist-forming section that generates mist by turning a raw material solution into a mist, a carrier gas supplying section that supplies a carrier gas that transports the mist, a film-forming section that heat-treats the mist to form a film on a substrate, a transporting section that connects the mist-forming section and the film-forming section and transports the mist by the carrier gas, and a transporting section heating means that heats at least a portion of the transporting section can extend the life of the mist in the transporting section and increase the film formation speed, thus completing the present invention.

Furthermore, as a result of extensive research into the above-mentioned problems, the inventors have discovered that a film-forming method for forming a film by heat-treating a mist in a film-forming section includes the steps of: generating mist by turning a raw material solution into mist in the mist-forming section; heating at least a part of a conveying section connecting the mist-forming section and the film-forming section; conveying the mist from the mist-forming section to the film-forming section via the conveying section using a carrier gas; and forming a film on a substrate by heat-treating the mist in the film-forming section, thereby making it possible to extend the life of the mist in the conveying section and increase the film-forming speed, and have completed the present invention.

The following explanation will be given with reference to the drawings.

Here, the term "mist" as used in this invention refers to a general term for fine liquid particles dispersed in a gas, and includes what are called fog, droplets, etc.

Figure 1 shows an example of a film forming apparatus 101 according to the present invention. The film forming apparatus 101 has a mist generating section 120 that generates mist by misting a raw material solution, a carrier gas supply section 130 that supplies a carrier gas for transporting the mist, a film forming section 140 that heat-treats the mist to form a film on a substrate, a transport section 109 that connects the mist generating section 120 and the film forming section 140 and transports the mist by the carrier gas, and a transport section heating means 111 that heats at least a part of the transport section 109. The film forming apparatus 101 may also be controlled in operation by including a control section 117 that controls the entire or part of the film forming apparatus 101. It is preferable that the control section 117 be capable of controlling at least the transport section heating means 111.

(Mist generating section)
In the mist generating section 120, the raw solution is adjusted and the raw solution is turned into mist to generate mist. The mist generating means is not particularly limited as long as it can turn the raw solution into mist, and any known mist generating means may be used, but it is preferable to use a mist generating means using ultrasonic vibrations, as this allows for more stable mist generation.

An example of such a mist generating unit 120 is shown in FIG. 2. For example, it may include a mist generating source 104 in which the raw solution 104a is contained, a container 105 in which a medium capable of transmitting ultrasonic vibrations, such as water 105a, and an ultrasonic vibrator 106 attached to the bottom surface of the container 105. In detail, the mist generating source 104 consisting of a container in which the raw solution 104a is contained is contained in the container 105 in which the water 105a is contained, using a support (not shown). The bottom of the container 105 is equipped with an ultrasonic vibrator 106, which is connected to an oscillator 116. When the oscillator 116 is operated, the ultrasonic vibrator 106 vibrates, and ultrasonic waves are propagated into the mist generating source 104 through the water 105a, turning the raw solution 104a into mist.

(Carrier gas supply unit)
The carrier gas supply unit 130 may have a carrier gas source 102a for supplying a carrier gas, and may be provided with a flow rate control valve 103a for adjusting the flow rate of the carrier gas sent from the carrier gas source 102a. In addition, the carrier gas supply unit 130 may also be provided with a dilution carrier gas source 102b for supplying a dilution carrier gas as required, and a flow rate control valve 103b for adjusting the flow rate of the dilution carrier gas sent from the dilution carrier gas source 102b.

The type of carrier gas is not particularly limited and can be appropriately selected depending on the film to be formed. For example, oxygen, ozone, inert gas such as nitrogen or argon, or reducing gas such as hydrogen gas or forming gas can be used. The type of carrier gas may be one type or two or more types. For example, a dilution gas obtained by diluting the same gas as the first carrier gas with another gas (e.g., diluted 10 times) may be used as the second carrier gas, or air may be used.
Furthermore, the number of supply points of the carrier gas may be two or more, not just one.
The flow rate of the carrier gas is not particularly limited. For example, when forming a film on a 30 mm square substrate, the flow rate is preferably 0.01 to 20 L/min, and more preferably 1 to 10 L/min.

(Film forming section)
In the film forming section 140, the mist is heated to cause a thermal reaction, and a film is formed on a part or the whole of the surface of the substrate 110. The film forming section 140 may include, for example, a film forming chamber 107 in which the substrate 110 is placed, and a hot plate 108 for heating the substrate 110. The hot plate 108 may be provided outside the film forming chamber 107 as shown in FIG. 1, or may be provided inside the film forming chamber 107. In addition, the film forming chamber 107 is provided with an exhaust gas exhaust port 112 at a position that does not affect the supply of the mist to the substrate 110.

In the present invention, the substrate 110 may be placed on the upper surface of the film formation chamber 107 in a face-down position, or may be placed on the bottom surface of the film formation chamber 107 in a face-up position.
The thermal reaction is not particularly limited as long as the mist reacts by heating. The reaction conditions can be appropriately set according to the raw material and the film to be formed. For example, the heating temperature can be in the range of 120 to 600°C, preferably in the range of 200°C to 600°C, and more preferably in the range of 300°C to 550°C.
The thermal reaction may be carried out under any of the following atmospheres: vacuum, non-oxygen atmosphere, reducing gas atmosphere, air atmosphere, and oxygen atmosphere, and may be appropriately set depending on the film to be formed. The reaction pressure may be under any of atmospheric pressure, pressurized pressure, and reduced pressure, but film formation under atmospheric pressure is preferred because the apparatus configuration can be simplified.

(Transportation section)
The transport unit 109 connects the mist generating unit 120 and the film forming unit 140. The mist is transported by a carrier gas from the mist generating source 104 of the mist generating unit 120 to the film forming chamber 107 of the film forming unit 140 via the transport unit 109. The transport unit 109 can be, for example, a supply pipe 109a. For example, a quartz pipe or a resin tube can be used as the supply pipe 109a.

(Transportation section heating means)
The conveying section heating means 111 is provided in the conveying section 109 to heat the conveying section 109. As shown in Fig. 1, the conveying section heating means 111 is preferably provided over the entire conveying section 109, that is, over the entire range from the outlet of the mist generating section 120 to the inlet of the film forming section 140, but may be provided only in a part of the supply pipe 109a of the conveying section 109 as shown in Fig. 3 and Fig. 4 (reference numbers are omitted as appropriate). The heating mechanism of the conveying section heating means 111 is not particularly limited, and any heating method such as resistance heating, high frequency heating, and light heating using infrared rays or the like may be used.

If the amount of moisture in the pipe is formally converted to the amount of saturated water vapor from the flow rate of the carrier gas and the flow rate of the mist, it is shown that the concentration of the mist in the pipe is supersaturated. Therefore, when the mist comes into contact with the cold wall of the pipe, the mist easily condenses, aggregates, and dews (reducing the lifespan of the mist), and the condensed mist is not sent to the film formation section and cannot contribute to film formation. In other words, this causes a decrease in the film formation speed. To address this problem, if the transport section 109 is heated by the transport section heating means 111, the condensation and aggregation of the mist is suppressed, and as a result, the film formation speed can be increased.

The temperature at which the transport section 109 is heated by the transport section heating means 111 is preferably 30 to 120° C. Within this range, condensation and aggregation of the mist can be more effectively suppressed, and the film formation speed can be increased.
The heating temperature can also be controlled by providing a control unit 117 in the film forming apparatus 101 .

(raw material solution)
The raw material solution is not particularly limited as long as it contains a material that can be turned into mist, and may be an inorganic material or an organic material. A metal or a metal compound is preferably used, and one or more metals selected from gallium, iron, indium, aluminum, vanadium, titanium, chromium, rhodium, nickel, and cobalt can be used.
The raw material solution is not particularly limited as long as it can turn the metal into mist, but the raw material solution can be suitably used in which the metal is dissolved or dispersed in an organic solvent or water in the form of a complex or salt. Examples of the complex include acetylacetonate complexes, carbonyl complexes, ammine complexes, and hydride complexes. Examples of the salt include metal chlorides, metal bromides, and metal iodides. In addition, the metals can be dissolved in hydrobromic acid, hydrochloric acid, hydroiodic acid, or the like to be used as an aqueous salt solution.

The raw material solution may be mixed with additives such as hydrohalogenated acid and oxidizing agents. Examples of the hydrohalogenated acid include hydrobromic acid, hydrochloric acid, and hydroiodic acid, with hydrobromic acid and hydroiodic acid being preferred. Examples of the oxidizing agent include peroxides such as hydrogen peroxide (H ₂ O ₂ ), sodium peroxide (Na ₂ O ₂ ), barium peroxide (BaO ₂ ), and benzoyl peroxide (C ₆ H ₅ CO) ₂ O ₂ , hypochlorous acid (HClO), perchloric acid, nitric acid, ozone water, and organic peroxides such as peracetic acid and nitrobenzene.

Furthermore, the raw material solution may contain a dopant. The dopant is not particularly limited. Examples of the dopant include n-type dopants such as tin, germanium, silicon, titanium, zirconium, vanadium, and niobium, and p-type dopants such as copper, silver, tin, iridium, and rhodium. The concentration of the dopant may be, for example, about 1×10 ¹⁶ /cm ³ to 1×10 ²² /cm ³ , and may be a low concentration of about 1×10 ¹⁷ /cm ³ or less, or a high concentration of about 1×10 ²⁰ /cm ³ or more.

(Base)
The substrate 110 is not particularly limited as long as it can form a film and can support the film. The material of the substrate 110 is not particularly limited, and a known substrate can be used, and may be an organic compound or an inorganic compound. Examples of the substrate include polysulfone, polyethersulfone, polyphenylene sulfide, polyetheretherketone, polyimide, polyetherimide, fluororesin, metals such as iron, aluminum, stainless steel, and gold, silicon, sapphire, quartz, glass, and gallium oxide, but are not limited thereto. The substrate may have any shape and is effective for any shape, and examples of the substrate include plate-like such as a flat plate or a disk, fibrous, rod-like, cylindrical, prismatic, cylindrical, spiral, spherical, and ring-like, but in the present invention, a plate-like substrate is preferred. The thickness of the plate-like substrate is not particularly limited, but is preferably 10 to 2000 μm, and more preferably 50 to 800 μm.

Next, an example of the manufacturing method according to the present invention will be described with reference to FIG.
First, the raw material solution 104a is accommodated in the mist generating source 104, the substrate 110 is placed on the hot plate 108 directly or through the wall of the film forming chamber 107, and the hot plate 108 is operated. Next, the conveying section heating means 111 is operated to heat the supply pipe 109a of the conveying section 109. Next, the flow rate control valves 103a and 103b are opened to supply carrier gas from the carrier gas sources 102a and 102b into the film forming chamber 107, and the atmosphere of the film forming chamber 107 is sufficiently replaced with the carrier gas, and then the flow rate of the carrier gas and the flow rate of the dilution carrier gas are adjusted. Next, the ultrasonic vibrator 106 is vibrated, and the vibration is propagated to the raw material solution 104a through the water 105a, thereby misting the raw material solution 104a to generate mist. Next, the mist is introduced into the film forming chamber 107 through the conveying section 109 by the carrier gas. At this time, since the supply pipe 109a is heated to, for example, 30 to 120° C. by the conveying section heating means 111, condensation of the mist in the supply pipe 109a is suppressed. Therefore, the mist efficiently introduced into the film formation chamber 107 thermally reacts with the heat of the hot plate 108 in the film formation chamber 107, and a film is formed on the substrate 110 at a high film formation speed.

The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto.

Example 1
First, the film forming apparatus 101 used in this embodiment will be described with reference to Fig. 1. The film forming apparatus 101 includes a carrier gas source 102a for supplying a carrier gas, a flow rate control valve 103a for adjusting the flow rate of the carrier gas sent from the carrier gas source 102a, a dilution carrier gas source 102b for supplying a dilution carrier gas, a flow rate control valve 103b for adjusting the flow rate of the dilution carrier gas sent from the dilution carrier gas source 102b, a mist generating source 104 containing a raw material solution 104a, a container 105 containing water 105a, an ultrasonic vibrator 106 attached to the bottom surface of the container 105, a film forming chamber 107, a quartz supply pipe 109a connecting the mist generating source 104 to the film forming chamber 107, and a hot plate 108. As the conveying section heating means 111, a ribbon heater JK-3 manufactured by AS ONE Corporation is wrapped around the entire supply pipe 109a to enable temperature control.

Next, a raw material solution was prepared. An aqueous solution of 0.1 mol/L gallium bromide was prepared, and 48% hydrobromic acid solution was added to make the volume ratio 10%. This was used as raw material solution 104a.

The raw material solution 104a obtained as described above was contained in the mist generating source 104. Next, a 4-inch (100 mm diameter) c-plane sapphire substrate was placed as the base 110 adjacent to the hot plate 108 in the film formation chamber 107, and the hot plate 108 was operated to raise the temperature to 500°C.
Next, the temperature of the conveying section heating means 111 was adjusted to 80° C. Next, the flow rate control valves 103a and 103b were opened to supply carrier gas from the carrier gas sources 102a and 102b into the film formation chamber 107, and the atmosphere in the film formation chamber 107 was sufficiently replaced with the carrier gas, after which the flow rate of the carrier gas was adjusted to 5 L/min and the flow rate of the dilution carrier gas was adjusted to 0.5 L/min. Note that oxygen was used as the carrier gas.

Next, the ultrasonic vibrator 106 was vibrated at 2.4 MHz, and the vibration was propagated to the raw material solution 104a through the water 105a, thereby misting the raw material solution 104a to generate mist. This mist was introduced into the film formation chamber 107 through the supply pipe 109a by the carrier gas. Then, the mist was thermally reacted in the film formation chamber 107 under atmospheric pressure and at 500° C., to form a thin film of gallium oxide (α-Ga ₂ O ₃ ) having a corundum structure on the substrate 110. The film formation time was 30 minutes.

The film thickness of the thin film on the substrate 110 was measured at 17 points on the surface of the substrate 110 using a step gauge, and an average value was calculated from each film thickness value.
The average film thickness was 5.6 μm. The film formation rate, calculated by dividing the average film thickness by the film formation time, was 11.2 μm/hour.

Example 2
The film was formed under the same conditions as in Example 1, except that the temperature of the conveying section heating means 111 was set to 30° C. The average film thickness was 5.5 μm, and the film formation speed was 11.0 μm/hour.

Example 3
The film was formed under the same conditions as in Example 1, except that the temperature of the conveying section heating means 111 was set to 120° C. The average film thickness was 5.1 μm, and the film formation speed was 10.2 μm/hour.

Example 4
The conveying section heating means 111 was provided in the manner shown in Fig. 3. That is, the conveying section heating means 111 was installed and heated in an area of 60% of the entire supply pipe 109a. Except for this, film formation was performed under the same conditions as in Example 1. The average film thickness was 5.2 µm, and the film formation speed was 10.4 µm/hour.

Example 5
The conveying section heating means 111 was provided in the manner shown in Fig. 4. That is, the conveying section heating means 111 was installed and heated in a range of 30% of the entire supply pipe 109a. Except for this, film formation was performed under the same conditions as in Example 1. The average film thickness was 4.8 µm, and the film formation speed was 9.6 µm/hour.

(Comparative Example 1)
The conveying section heating means 111 was not provided, and the temperature of the supply pipe 109a was kept at room temperature, and other than these, the film was formed under the same conditions as in Example 1. The average film thickness was 3.7 μm, and the film formation speed was 7.4 μm/hour.

The results of Examples 1-5 and Comparative Example 1 are summarized in Table 1. Note that in Comparative Example 1, the conveying section heating means coverage ratio [%] is "0" because the conveying section heating means 111 is not provided.

Comparing Examples 1 to 5 with Comparative Example 1, it was found that a dramatic improvement in the film formation speed was achieved by providing the conveying section heating means 111 and heating the conveying section. It was also found that the film formation speed could be improved even if the conveying section heating means 111 was installed in only a part of the conveying section.

The present invention is not limited to the above-described embodiment. The above-described embodiment is merely an example, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits similar effects is included within the technical scope of the present invention.

101...film forming apparatus, 102a...carrier gas source,
102b...dilution carrier gas source; 103a...flow rate control valve;
103b...flow rate control valve; 104...mist generating source; 104a...raw material solution;
105: container; 105a: water; 106: ultrasonic transducer; 107: film formation chamber;
108...hot plate; 109...transport unit; 109a...supply pipe; 110...substrate;
111: conveying section heating means; 112: exhaust port; 116: oscillator; 117: control section;
120 mist generating section, 130 carrier gas supply section, 140 film forming section.

Claims (6)

A film forming apparatus,
a mist generating unit that generates mist by misting the raw material solution;
A carrier gas supply unit that supplies a carrier gas that carries the mist;
a film forming section for forming a film on a substrate by heat-treating the mist;
a transport section that connects the mist generating section and the film forming section, and that transports the mist that is supersaturated by the carrier gas, and that does not include a flow rate adjusting means;
a conveying section heating means for heating at least a part of the conveying section to suppress condensation and aggregation of the mist . The deposition apparatus further includes a control unit,
2. The film forming apparatus according to claim 1, wherein the control unit controls the conveying unit heating means to set the temperature of the conveying unit at 30 to 120.degree. A film forming method for forming a film by heat-treating a mist in a film forming unit, comprising:
A step of generating mist by misting the raw material solution in a mist generating section;
a step of connecting the mist generating unit and the film forming unit and heating at least a part of a transport unit that does not include a flow rate adjusting means;
transporting the supersaturated mist from the mist generating unit to the film forming unit by a carrier gas via the transport unit;
and forming a film on a substrate by heat-treating the mist in the film-forming section ,
The film forming method is characterized in that in the heating step, condensation and aggregation of the mist is suppressed by the heating . A film forming method for forming a film by heat-treating a mist in a film forming unit, comprising:
A step of generating mist by misting the raw material solution in a mist generating section;
a step of connecting the mist generating unit and the film forming unit, controlling the temperature of at least a part of a transport unit not equipped with a flow rate adjusting means to suppress condensation and aggregation of the mist , and transporting the supersaturated mist from the mist generating unit to the film forming unit by a carrier gas via the transport unit;
and a step of heat-treating the mist in the film-forming section to form a film on a substrate. A film forming method for forming a film by heat-treating a mist in a film forming unit, comprising:
A step of generating mist by misting the raw material solution in a mist generating section;
The method includes a step of transporting the mist from the mist generating unit to the film forming unit by a carrier gas through a transport unit not equipped with a flow rate adjusting means, and a step of heat-treating the mist in the film forming unit to form a film on a substrate,
measuring a flow rate of the carrier gas and a flow rate of the mist, and comparing an amount of water vapor in the transport section calculated by assuming that the mist is water vapor with saturated water vapor at room temperature, thereby controlling a temperature of at least a part of the transport section;
The film forming method , wherein in the step of controlling the temperature of at least a part of the transport section, condensation and aggregation of mist is suppressed by the temperature control . The film forming method according to any one of claims 3 to 5, characterized in that the temperature of the transport section is set to 30 to 120°C.

Images