Nozzle cleaning method, crystalline oxide film deposition method, and film deposition apparatus

Abstract

To provide a cleaning method of a nozzle, capable of preventing a nozzle to which a product material is adhered from being a particle source at a deposition.SOLUTION: A cleaning method of a nozzle, comprises: a stage for heating a substrate to be mounted; and a deposition part that includes a nozzle for supplying a mist of a deposition raw material containing a carrier gas and a gallium in accordance with them to the substrate. The cleaning method of a nozzle performs a cleaning step in which the mist to be supplied is reacted onto the substrate to be heated to use a deposition device for depositing a crystalline oxide film containing gallium as a main component onto the substrate, and a cleaning agent containing at least water to the nozzle is supplied in a state of a liquid or an air, a material to be produced adhered to the nozzle at the deposition is removed.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for cleaning nozzles, a method for forming crystalline oxide films, and a film formation apparatus. [Background technology]

[0002] Mist chemical vapor deposition (Mist CVD), a method for forming thin films on a substrate using atomized mist-like raw materials, has been developed and is used for fabricating oxide semiconductor films and the like (Patent Document 1). As an example of this Mist CVD method, a method of supplying mist to the substrate via a nozzle has also been disclosed, as shown in Patent Documents 2 and 3. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2013-028480 [Patent Document 2] Japanese Patent Publication No. 2014-063973 [Patent Document 3] Japanese Patent Publication No. 2021-136445 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, until now, a method for atomizing raw materials to form high-quality films had not been established, and there was a problem of numerous particles adhering to the fabricated film due to the quality of the raw material mist. Furthermore, it is known that increasing the mist supply rate, such as when increasing the film deposition rate, makes this particle adhesion even more pronounced, making it a challenge to balance film quality and productivity. To address these challenges, Patent Document 3 discloses a method for suppressing particle generation by controlling the atomization method. While this method is effective in suppressing particle generation, as the film thickness increases and the film deposition time is extended, the mist tends to aggregate within the nozzle, and the product adhering to the nozzle wall and other surfaces tends to detach and float, becoming a new source of particles. Therefore, it is preferable to more reliably prevent the product from becoming a source of particles.

[0005] The present invention was made to solve the above problems and aims to provide a nozzle cleaning method that can prevent products adhering to the nozzle during film formation from becoming a source of particles. Furthermore, the present invention aims to provide a film formation method and apparatus that can efficiently form high-quality thin films with suppressed particle adhesion. [Means for solving the problem]

[0006] The present invention has been made to achieve the above objective, and provides a nozzle cleaning method characterized by using a film deposition apparatus comprising a stage for heating a substrate on which a substrate is placed, and a film deposition section having a nozzle for supplying a mist of a film deposition raw material containing gallium, accompanied by a carrier gas, to the substrate, wherein a crystalline oxide film mainly composed of gallium is deposited on the substrate by a reaction of the supplied mist on the heated substrate, and by performing a cleaning step to remove products adhering to the nozzle during film deposition by supplying a cleaning agent containing at least water in a liquid or gaseous state to the nozzle.

[0007] This nozzle cleaning method removes the product adhering to the nozzle during film formation using a water-based cleaning agent. This prevents the adhering product from detaching, floating, and becoming particles. Therefore, it prevents the product adhering to the nozzle during film formation from becoming a source of particles. Furthermore, this nozzle cleaning method uses a general-purpose water-based cleaning agent to remove the product, allowing for inexpensive nozzle cleaning and ensuring excellent safety during the cleaning process. Furthermore, by incorporating such a cleaning method into the deposition method for crystalline oxide films, it is possible to obtain high-quality crystalline oxide films with significantly reduced particle density on the film surface. Additionally, it becomes possible to manufacture crystalline oxide films at low cost.

[0008] In the cleaning process, the temperature of the nozzle when supplying the cleaning agent to the nozzle may be set to 50 to 250°C. With this cleaning method, by setting the nozzle temperature to 50°C or higher during the cleaning process, it is possible to suppress the residue of the cleaning agent on the nozzle surface after cleaning and to promote the reaction in which the product dissolves in the cleaning agent. Furthermore, by setting the nozzle temperature to 250°C or lower during the cleaning process, it is possible to reliably cause the reaction in which the product dissolves in the cleaning agent and is removed. Therefore, if a film deposition process is carried out afterward, a high-quality crystalline oxide film with a significantly reduced particle density on the film surface can be obtained.

[0009] In the cleaning process, water or steam containing acid may be supplied as the cleaning agent. This cleaning method allows the acid to accelerate the reaction in which the product dissolves and is removed by the cleaning agent. Therefore, when a film deposition process is carried out afterward, a high-quality crystalline oxide film can be obtained with an even more significantly reduced particle density on the film surface.

[0010] In the cleaning step, the cleaning agent may be supplied to the nozzle as a mist. By using a mist of the cleaning agent in this way, the same misting equipment used to atomize the film-forming raw materials in the film-forming process can be used to supply the cleaning agent. Therefore, it is not always necessary to prepare a dedicated device for supplying the cleaning agent, and the cleaning process can be carried out at a low cost. Furthermore, by incorporating this cleaning method into the film-forming method for crystalline oxide films, it is possible to manufacture crystalline oxide films at a low cost.

[0011] The stage may be capable of supporting the substrate having a diameter of 4 inches (100 mm) to 8 inches (200 mm). By using a stage capable of supporting large-area substrates in this way, when a film deposition process is subsequently performed, a high-quality crystalline oxide film with significantly reduced particle density on the film surface can be obtained even on large-area substrates.

[0012] In the cleaning process, the nozzle may be heated using a heating device separate from the device that heats the stage. By heating the nozzle with a separate heating device from the stage heating device, the nozzle can be heated to a high temperature efficiently with less heat than when the stage is heated using the stage heating device and the nozzle is heated by heat conduction through the stage and the atmosphere inside the device, thereby reducing the cost of the cleaning process. Furthermore, by heating the nozzle with a separate heating device from the stage heating device, the nozzle can be heated more uniformly compared to heating the nozzle with the stage heating device, depending on the arrangement and structure of the heating devices. As a result, unevenness in the degree of product removal depending on the position on the nozzle surface is less likely to occur, and when a film deposition process is performed afterward, a high-quality crystalline oxide film with a significantly reduced particle density on the film surface can be efficiently obtained.

[0013] Further, the present invention provides a method for forming a crystalline oxide film, which comprises performing a film-forming step of supplying a mist of a film-forming raw material containing gallium accompanied by a carrier gas from a nozzle to a substrate placed on a heated stage, reacting the mist on the substrate, and forming a crystalline oxide film containing gallium as a main component on the substrate, and performing the cleaning step described above every time the film-forming step is performed for a predetermined time. Thus, by cleaning the nozzle every time the film-forming step is performed for a predetermined time to remove the deposits, the products adhering to the nozzle are removed from the nozzle before they are detached, floated, and become particles. Therefore, a high-quality crystalline oxide film with a significantly reduced particle density on the film surface can be obtained. Further, the crystalline oxide film can be manufactured at a low cost and has excellent safety during the manufacture of the crystalline oxide film.

[0014] Furthermore, the present invention provides a film-forming apparatus which comprises a stage for heating a placed substrate, a film-forming section having a nozzle for supplying a mist of a film-forming raw material accompanied by a carrier gas to the substrate, and a raw material supply section for supplying the mist to the nozzle of the film-forming section, wherein the supplied mist reacts on the heated substrate to form a film on the substrate, and the film-forming apparatus is characterized by comprising a cleaning agent supply section for supplying a cleaning agent containing at least water to the nozzle in a liquid or gaseous state.

[0015] Thus, by providing the film-forming apparatus with a cleaning agent supply section, the nozzle is cleaned every time film formation is performed for a predetermined time to remove the deposits, and the products adhering to the nozzle are removed from the nozzle before they are detached, floated, and become particles. Therefore, a high-quality film with a significantly reduced particle density on the film surface can be obtained. Further, the film can be manufactured at a low cost and has excellent safety during the manufacture of the film.

[0016] At this time, every time film formation is performed for a predetermined period, by supplying the cleaning agent from the cleaning agent supply unit to the nozzle, a control unit is provided that controls the raw material supply unit and the cleaning agent supply unit so as to perform cleaning to remove the product adhering to the nozzle during film formation.

[0017] By providing such a control unit and controlling the raw material supply unit and the cleaning agent supply unit by the control unit so as to perform cleaning every time film formation is performed for a predetermined period, it becomes possible to automatically switch between film formation and cleaning.

Advantages of the Invention

[0018] As described above, according to the nozzle cleaning method of the present invention, it is possible to prevent the product adhering to the nozzle during film formation from becoming a particle generation source. Therefore, when the film formation process is carried out after cleaning, a high-quality crystalline oxide film with a significantly reduced particle density on the film surface can be obtained. Further, according to the method for forming a crystalline oxide film of the present invention, a high-quality crystalline oxide film with suppressed particle adhesion can be efficiently formed. In addition, the crystalline oxide film can be formed at a low cost, and the safety during the film formation of the crystalline oxide film is also excellent. Furthermore, according to the film forming apparatus of the present invention, a high-quality film with suppressed particle adhesion can be efficiently formed. In addition, the film can be formed at a low cost, and the safety during the film formation of the film is also excellent. Furthermore, by cleaning the nozzle, clogging of the nozzle is suppressed, so that an effect of suppressing deterioration of the film thickness distribution can be obtained, and further an effect of suppressing a decrease in the film formation rate can be obtained. In addition, when doping is performed, an effect of suppressing nozzle contamination (memory effect) by the doping element can be obtained.

Brief Description of the Drawings

[0019] [Figure 1]A schematic diagram of an example of a semiconductor device using a multilayer structure having a crystalline oxide film manufactured by the crystalline oxide film formation method according to the present invention is shown. [Figure 2] A schematic diagram of an example of a film deposition apparatus (mist CVD apparatus) suitably used for forming crystalline oxide films according to the present invention is shown. [Figure 3] This diagram illustrates an example of the misting section of a film deposition apparatus used in the present invention. [Figure 4] This schematic diagram shows another example of a film deposition apparatus (mist CVD apparatus) suitably used for forming crystalline oxide films according to the present invention, in which a cleaning water misting unit for atomizing water as a cleaning agent is provided in addition to the misting unit for atomizing the raw material solution. [Figure 5] This schematic diagram shows another example of a film deposition apparatus (mist CVD apparatus) suitably used for forming crystalline oxide films according to the present invention, and illustrates a case in which a water vapor source is provided to supply water as a cleaning agent as water vapor. [Modes for carrying out the invention]

[0020] The present invention will be described in detail below, but the present invention is not limited to these descriptions.

[0021] As described above, there was a need for a nozzle cleaning method that could prevent products adhering to the nozzle during film formation from becoming a particle source, and for a crystalline oxide film formation method and apparatus that could form a high-quality crystalline oxide film with significantly reduced particle density on the film surface.

[0022] As a result of diligent study on the above problems, the present inventors have found that by using a film deposition apparatus comprising a stage for heating a placed substrate and a nozzle for supplying a mist of a film deposition raw material containing gallium, accompanied by a carrier gas, to the substrate, a crystalline oxide film mainly composed of gallium is deposited on the substrate by a reaction of the supplied mist on the heated substrate, and by performing a cleaning step to remove products adhering to the nozzle during film deposition by supplying a cleaning agent containing at least water in liquid or gaseous form to the nozzle, it is possible to prevent the nozzle to which products have adhered during film deposition from becoming a particle source, and when the film deposition process is performed after cleaning, a high-quality crystalline oxide film with significantly reduced particle density on the film surface can be obtained, thus completing the present invention.

[0023] Furthermore, as a result of diligent research into the above-mentioned problems, the inventors have discovered that a high-quality crystalline oxide film with significantly reduced particle density on the film surface can be obtained by a method for forming a crystalline oxide film, characterized in that a mist of a film-forming raw material containing gallium, accompanied by a carrier gas, is supplied from a nozzle to a substrate placed on a heated stage, reacting on the substrate to form a crystalline oxide film mainly composed of gallium on the substrate, and the cleaning step described above is performed after each predetermined time of the film-forming step. Thus, the inventors have completed the present invention.

[0024] Furthermore, after diligently studying the above problems, the present inventors have found that a high-quality film with significantly reduced particle density on the film surface can be obtained by a film-forming apparatus comprising a stage for heating a placed substrate, a film-forming section having a nozzle for supplying a mist of film-forming raw materials accompanied by a carrier gas to the substrate, and a raw material supply section for supplying the mist to the nozzle of the film-forming section, wherein the supplied mist reacts on the heated substrate to form a film on the substrate, and the apparatus further comprising a cleaning agent supply section for supplying a cleaning agent containing at least water in liquid or gaseous form to the nozzle, thereby completing the present invention.

[0025] Hereinafter, embodiments preferred for the present invention will be described with reference to the drawings. First, with reference to Figure 1, a preferred example of a semiconductor device 100 using a crystalline oxide film 103 manufactured by a film formation method for the crystalline oxide film 103, including a nozzle cleaning method according to an embodiment of the present invention, will be described.

[0026] As shown in Figure 1, in the semiconductor device 100, a crystalline oxide film 103 is formed on a substrate 101, and the substrate 101 and the crystalline oxide film 103 constitute a laminated structure 110. The crystalline oxide film 103 is constructed by stacking an insulating thin film 103a and a semiconductor thin film 103b in order from the substrate 101 side. A gate insulating film 105 is formed on the semiconductor thin film 103b. A gate electrode 107 is formed on the gate insulating film 105. In addition, source and drain electrodes 109 are formed on the semiconductor thin film 103b so as to sandwich the gate electrode 107. With this configuration, the depletion layer formed on the semiconductor thin film 103b can be controlled by the gate voltage applied to the gate electrode 107, enabling transistor operation (FET device). Semiconductor devices formed using the crystalline oxide film 103 deposited by the film deposition method according to the present invention include transistors such as MIS, HEMT, and IGBT, TFTs, Schottky barrier diodes utilizing semiconductor-metal junctions, PN or PIN diodes combined with other P layers, and light-emitting / receiving devices. The crystalline oxide film 103 according to the present invention is useful for improving the characteristics of these devices.

[0027] (Crystalline oxide film) The crystalline oxide film 103 produced by the film formation method of the present invention has a particle density of 50 particles / cm² with a diameter of 0.3 μm or more on the surface of the crystalline oxide film 103. 2 The following applies: Particles with a diameter of 0.3 μm or larger significantly affect the characteristics of the semiconductor device 100 when it is manufactured based on the crystalline oxide film 103. The above describes a particle density of 50 particles / cm² with a diameter of 0.3 μm or larger. 2The following crystalline oxide film 103 is of high quality and suitable for semiconductor device manufacturing.

[0028] In this invention, "particles" include those incorporated into the crystalline oxide film 103 and integrated with the film, as well as those adhering to the surface of the crystalline oxide film 103 as foreign matter, and refer to those observed as particles when the surface of the film is observed. Furthermore, the diameter of the particles is a value based on the size of the particles measured by a light scattering type particle measuring instrument. The size of the particles is determined by calibrating the measuring instrument with standard particles of multiple sizes.

[0029] In other words, the diameter of a particle is a value classified by comparing the measured value of a particle measured with a measuring instrument with the measured value of a standard particle. Particles on the surface of the crystalline oxide film 103 can be measured, for example, using a laser scattering type particle counter. It is also possible to observe the film surface using an optical microscope and count the number of particles for each size.

[0030] While crystalline oxide films 103 are generally composed of metal and oxygen, in the crystalline oxide film 103 according to the present invention, it is preferable that gallium is the main component as the metal. In this invention, "mainly composed of gallium" means that 50 to 100 atomic percent of the metal component is gallium. Other metal components may include, for example, one or more metals selected from iron, indium, aluminum, vanadium, titanium, chromium, rhodium, iridium, nickel, and cobalt. Unless otherwise specified, the following description will use the case where the crystalline oxide film 103 is mainly composed of gallium as an example.

[0031] The crystalline oxide film may contain a dopant element. For example, n-type dopants such as tin, germanium, silicon, titanium, zirconium, vanadium or niobium, or p-type dopants such as copper, silver, iridium, rhodium, magnesium, etc. may be mentioned, and it is not particularly limited. The concentration of the dopant is, for example, about 1×10 16 / cm 3 ~1×10 22 / cm 3 may be, or may be a low concentration of about 1×10 17 / cm 3 or less, or may be a high concentration of about 1×10 20 / cm 3 or more.

[0032] The crystal structure of the crystalline oxide film 103 is not particularly limited, and it may be a β-gallia structure, a corundum structure, or a cubic crystal. Even if a plurality of crystal structures are mixed or it is polycrystalline, it does not matter, but it is preferably a single crystal or a uniaxially oriented film. Whether it is a single crystal or a uniaxially oriented film can be confirmed by an X-ray diffractometer, an electron beam diffractometer, etc. When the film is irradiated with X-rays or an electron beam, a diffraction image corresponding to the crystal structure is obtained, but only specific peaks appear when it is uniaxially oriented. Thus, it can be determined that it is uniaxially oriented.

[0033] The film thickness of the crystalline oxide film 103 is not particularly limited, but it is preferably 0.1 μm or more. The upper limit value is not particularly limited. For example, it may be 100 μm or less, preferably 50 μm or less, and more preferably 30 μm or less. The film thickness can be measured by methods such as a stylus type step gauge, a reflection spectroscopic film thickness meter, an ellipsometer, or observing the cross section with SEM or TEM, and any method may be used. Such a crystalline oxide film 103 can be obtained by forming a film by a mist CVD method using a mist CVD apparatus (film forming apparatuses 201, 201a, 201b) described later.

[0034] (Underlying substrate) The substrate 101 for forming the crystalline oxide film 103 using the film formation method according to the present invention is not particularly limited as long as it serves as a support for the crystalline oxide film 103. The material is not particularly limited, and known substrates can be used, and may be organic compounds or inorganic compounds. Examples include polysulfone, polyethersulfone, polyphenylene sulfide, polyetheretherketone, polyimide, polyetherimide, fluororesin, metals such as iron, aluminum, stainless steel, and gold, quartz, glass, calcium carbonate, gallium oxide, and ZnO. In addition to these, single crystal substrates such as silicon, sapphire, lithium tantalate, lithium niobate, SiC, GaN, iron oxide, and chromium oxide can be used, and in the present invention, such single crystal substrates are desirable. This allows for obtaining a higher quality crystalline oxide film 103. In particular, sapphire substrates, lithium tantalate substrates, and lithium niobate substrates are relatively inexpensive and industrially advantageous.

[0035] The thickness of the substrate 101 is preferably 100 to 5000 μm. Within this range, handling is easy, and thermal resistance during film formation can be suppressed, making it easier to obtain a high-quality film.

[0036] There are no particular restrictions on the size of the base substrate 101, but the area of ​​the base substrate 101 is 100 mm². 2 If the film is 2 inches (50 mm) or larger in diameter, it is preferable to obtain a large-area film with good crystallinity. Furthermore, if the diameter of the substrate 101 is 4 inches (100 mm) to 8 inches (200 mm), the obtained crystalline oxide film 103 can be easily processed using existing processing equipment, which is industrially advantageous when manufacturing semiconductor devices. In addition, it has a large area and excellent film thickness distribution, and when applied to a semiconductor device, it exhibits excellent semiconductor properties. For example, when a semiconductor device such as a power semiconductor device is manufactured from such a crystalline oxide film 103, a product lot containing two or more of these semiconductor devices can achieve a breakdown yield of 75% or more.

[0037] Another layer may be interposed between the substrate 101 and the crystalline oxide film 103. This other layer is generally a layer with a different composition from the substrate 101 and the outermost crystalline oxide film 103, and is also called a buffer layer. The buffer layer can be an oxide semiconductor film, an insulating film, a metal film, etc., and suitable materials include, for example, Al2O3, Ga2O3, Cr2O3, Fe2O3, In2O3, Rh2O3, V2O3, Ti2O3, Ir2O3, and mixed crystals thereof. The thickness of the buffer layer is preferably 0.1 μm to 2 μm.

[0038] Next, a nozzle cleaning method and a method for forming a crystalline oxide film 103, including the nozzle cleaning method, according to the present invention using a mist CVD apparatus will be described. Here, the term "mist" in this invention refers to a general term for fine liquid particles dispersed in a gas, and includes what are called fog, droplets, etc.

[0039] (Film forming equipment) Figure 2 shows a schematic diagram of a film deposition apparatus 201 that performs film deposition by the mist CVD method. The film deposition apparatus 201 includes at least a misting unit 220 that atomizes the raw material solution 204a to generate mist, a carrier gas supply unit 230 that supplies a carrier gas to transport the mist, a supply pipe 209 that connects the misting unit 220 and the film deposition unit 207 and through which the mist is transported by the carrier gas, and a film deposition unit 207 that heat-treats the mist to deposit a film on the substrate 210.

[0040] (Misting section) In the misting unit 220, the raw material solution 204a is atomized to generate mist. The misting means is not particularly limited as long as it can atomize the raw material solution 204a, and any known misting means may be used, but it is preferable to use a misting means using ultrasonic vibration, because it can atomize more stably.

[0041] An example of such a misting unit 220 is shown in Figure 3. The misting unit 220 may include a mist generating source 204 containing a raw material solution 204a containing gallium, a container 205 containing a medium capable of transmitting ultrasonic vibrations, such as water 205a, and an ultrasonic transducer 206 attached to the bottom of the container 205.

[0042] In detail, a mist source 204, consisting of a container holding a raw material solution 204a, can be housed in a container 205 holding water 205a using a support (not shown). An ultrasonic transducer 206 may be installed at the bottom of the container 205, and the ultrasonic transducer 206 may be connected to an oscillator 216. When the oscillator 216 is activated, the ultrasonic transducer 206 vibrates, and ultrasonic waves are transmitted through the water 205a into the mist source 204, causing the raw material solution 204a to be atomized.

[0043] (Raw material solution) The raw material solution 204a is not particularly limited in terms of the materials contained in the solution, as long as it can be atomized, and may be inorganic or organic materials. Preferably, metals or metal compounds are used as materials, and for example, a solution containing one or more metals selected from gallium, iron, indium, aluminum, vanadium, titanium, chromium, rhodium, nickel, and cobalt may be used.

[0044] As the raw material solution 204a described above, a metal in the form of a complex or salt, dissolved or dispersed in an organic solvent or water, can be suitably used. Examples of salt forms include metal chloride salts, metal bromide salts, metal iodide salts, and other halide salts. Alternatively, a solution of the above metal dissolved in a hydrogen halide such as hydrobromic acid, hydrochloric acid, or hydroiodic acid can also be used as a salt solution. Examples of complex forms include acetylacetonate complexes, carbonyl complexes, ammine complexes, and hydride complexes. An acetylacetonate complex can also be formed by mixing acetylacetone with the aforementioned salt solution. The metal concentration in the raw material solution 204a is not particularly limited and can be 0.005 to 1 mol / L, for example. The mixing and dissolution temperature is preferably 20°C or higher.

[0045] Additives such as hydrohalic acid and oxidizing agents may be mixed into the raw material solution 204a. Examples of hydrohalic acid include hydrobromic acid, hydrochloric acid, and hydroiodic acid, but hydrobromic acid or hydroiodic acid are preferred because they provide a high film formation rate. Examples of oxidizing agents include peroxides such as hydrogen peroxide (H2O2), sodium peroxide (Na2O2), barium peroxide (BaO2), and benzoyl peroxide (C6H5CO)2O2, as well as organic peroxides such as hypochlorous acid (HClO), perchloric acid, nitric acid, ozonated water, peracetic acid, and nitrobenzene.

[0046] The raw material solution 204a may contain a dopant source. The dopant source is not particularly limited. Examples include n-type dopant sources such as tin, germanium, silicon, titanium, zirconium, vanadium, or niobium, or p-type dopant sources such as copper, silver, iridium, rhodium, or magnesium. In the following explanation, unless otherwise specified, the case where a gallium-containing solution is used as the raw material solution 204a will be described.

[0047] (Carrier gas supply department) As shown in Figure 2, the carrier gas supply unit 230 has a carrier gas source 202a that supplies carrier gas to the atomization unit 220. In this case, a flow control valve 203a for adjusting the flow rate of the carrier gas discharged from the carrier gas source 202a may be provided in the piping connecting the carrier gas source 202a and the atomization unit 220. Furthermore, a dilution carrier gas source 202b for supplying dilution carrier gas and a flow control valve 203b for adjusting the flow rate of dilution carrier gas discharged from the dilution carrier gas source 202b may also be provided as needed. In this invention, the sum of the carrier gas flow rate and the dilution carrier gas flow rate is called the total carrier gas flow rate.

[0048] The type of carrier gas is not particularly limited and can be appropriately selected depending on the film to be deposited. Examples include oxidizing gases such as oxygen and ozone, inert gases such as nitrogen and argon, or reducing gases such as hydrogen gas and foaming gas.

[0049] Furthermore, there may be one type of carrier gas or two or more types. For example, as the second carrier gas, a dilution gas may be used, which is the same gas as the first carrier gas diluted with another gas (for example, diluted 10 times), or air may be used. The total flow rate of the carrier gas is not particularly limited. For example, when depositing a film on a substrate with a diameter of 2 inches (approximately 50 mm), the total flow rate of the carrier gas is preferably 0.05 to 50 NL / min, and more preferably 5 to 20 NL / min. Note that the unit NL / min represents the flow rate converted to 0°C and 1 atmosphere (101325 Pa).

[0050] (supply pipe) The film deposition apparatus 201 has a supply pipe 209 connecting the atomizing section 220 and the film deposition section 207. In this case, the mist is transported from the mist generation source 204 of the atomizing section 220 via the supply pipe 209 by a carrier gas and supplied to the film deposition section 207. The supply pipe 209 can be, for example, a quartz tube, a glass tube, or a resin tube. If the film deposition apparatus 201 is equipped with a dilution carrier gas source 202b, the dilution carrier gas source 202b is connected to the middle of the supply pipe 209.

[0051] The supply pipe 209, carrier gas supply unit 230, and misting unit 220 constitute a raw material supply unit that supplies mist to the nozzle 215 of the film formation unit 207.

[0052] (Film forming section) The film deposition unit 207 has a film deposition chamber 207a, which is a container in which film deposition takes place, and a stage 207b on which the substrate 210 is placed is provided inside the film deposition chamber 207a. The stage 207b also heats the placed substrate 210 and is equipped with a heater 208 for heating the substrate 210. The stage 207b heats the substrate 210 by transferring the heat generated by the heater 208 to the substrate 210. Here, the bottom surface of the film deposition chamber 207a is shown as the stage 207b. The heater 208 may be provided outside the film deposition chamber 207a, for example, as shown in Figure 2, or it may be provided inside the film deposition chamber 207a. The stage 207b must be sized to accommodate the substrate 210. For example, the stage 207b may be capable of accommodating substrates 210 with a diameter of 4 inches (100 mm) to 8 inches (200 mm). By using a stage 207b capable of supporting a large-area substrate 210, a high-quality crystalline oxide film 103 with significantly reduced particle density on the film surface can be obtained through the film deposition process, even on a large-area substrate 210.

[0053] The film deposition unit 207 has one end of a supply pipe 209 located inside the film deposition chamber 207a, allowing the film deposition gas and accompanying mist supplied from the supply pipe 209 to be introduced into the film deposition chamber 207a. The film deposition unit 207 has a nozzle 215 connected to one end of the supply pipe 209 inside the film deposition chamber 207a, which supplies a mist of film deposition raw material containing gallium to the substrate 210, and the film deposition gas is ejected from the nozzle 215 toward the substrate 210.

[0054] As shown in Figure 2, an exhaust gas outlet 212 may be provided on the outer wall of the film deposition chamber 207a of the film deposition section 207. Furthermore, the deposition chamber 207a of the deposition unit 207 may be provided with a top plate or the like (not shown) for rectifying the supplied mist on the substrate.

[0055] Alternatively, the substrate 210 may be placed on a stage 207b provided on the upper surface of the film deposition section 207 to form a face-down configuration, or the substrate 210 may be placed on a stage 207b provided on the upper surface of the bottom of the film deposition section 207 to form a face-up configuration. Figure 1 illustrates the face-up configuration.

[0056] Furthermore, the heater 208 or nozzle 215 may be connected to a transport mechanism (not shown) and be capable of movement such as reciprocating motion or rotational motion. Performing these movement operations during film formation improves the uniformity of the resulting film.

[0057] (Film forming method) The mist CVD method comprises a mist generation step in which a raw material solution 204a is atomized in a misting unit 220 to generate mist; a carrier gas supply step in which a carrier gas for transporting the mist is supplied to the misting unit 220; a transport step in which the mist is transported by the carrier gas from the misting unit 220 to the film deposition unit 207 via a supply pipe 209 connecting the misting unit 220 and the film deposition unit 207; and a film deposition step in which the transported mist is heat-treated to form a film on the substrate 210, which is the base substrate. In addition, the present invention also includes a cleaning step for cleaning the nozzle 215.

[0058] First, the substrate 210 is placed on the stage 207b in the film deposition section 207, and the heater 208 is activated. Next, the flow control valves 203a and 203b are opened to supply carrier gas to the film deposition section 207 from the carrier gas source 202a and the dilution carrier gas source 202b. After the atmosphere in the film deposition section 207 has been sufficiently replaced with carrier gas, the flow rates of the carrier gas and the dilution carrier gas are adjusted, respectively.

[0059] Next, the raw material solution 204a prepared as described above is placed inside the mist generating source 204. In the mist generation process, the ultrasonic transducer 206 is vibrated, and the vibration is transmitted to the raw material solution 204a through the water 205a, thereby atomizing the raw material solution 204a and generating mist.

[0060] Next, as part of the carrier gas supply process, carrier gas for transporting the mist is supplied from the carrier gas source 202a to the misting unit 220.

[0061] Next, in the transport process, the mist is transported by carrier gas from the misting unit 220 to the nozzle 215 in the film-forming unit 207 via a supply pipe 209 connecting the misting unit 220 and the film-forming unit 207.

[0062] Next, in the film formation process, a mist of the film formation raw material containing gallium, along with a carrier gas, which has been transported to the nozzle 215, is sprayed from the tip of the nozzle 215 onto the substrate 210 and supplied to the substrate 210. The mist is heated by heat conduction from the heated substrate 210, causing a thermal reaction on the substrate 210, and a crystalline oxide film 103 mainly composed of gallium is formed on the surface of the substrate 210. In this manner, the film deposition apparatus 201 deposits a crystalline oxide film 103, mainly composed of gallium, onto the substrate 210 by reacting the mist supplied from the nozzle 215 on the heated substrate 210 during the film deposition process. The substrate 210 or nozzle 215 may be moved during film formation by means of a transport mechanism (not shown), such as by reciprocating motion or rotational motion. Performing these movement operations further improves the uniformity of the resulting film.

[0063] The thermal reaction of the mist also depends on the ambient temperature around the substrate. Therefore, it is desirable that the temperature of the nozzle 215 during film formation and the inner wall of the film formation chamber 207a of the film formation section 207 be higher than room temperature. This is because it stabilizes the thermal reaction. For example, the nozzle temperature can be set to 50-250°C.

[0064] The thermal reaction may be carried out under any of the following atmospheres: a non-oxygen atmosphere, a reducing gas atmosphere, an air atmosphere, or an oxygen atmosphere, and should be set appropriately depending on the film to be deposited. The reaction pressure may be under atmospheric pressure, a pressurized atmosphere, or a reduced pressure, but deposition under atmospheric pressure is preferable because it simplifies the apparatus configuration.

[0065] When the above-described film formation process is performed for a predetermined time, a considerable amount of product adheres to the inner or outer wall of the nozzle 215. If left unattended, these products will detach, float, and become a source of particles on the film. To remove these products, a cleaning process is performed. Specifically, in the cleaning process, the film formation apparatus 201 is used to supply a cleaning agent containing at least water to the nozzle 215 in liquid or gaseous form, thereby removing the products that adhered to the nozzle 215 during film formation.

[0066] The cleaning agent is, for example, water, and if supplied in gaseous form, water vapor is supplied. If the cleaning agent is water, it is preferable to use pure water so that no components of the cleaning agent remain in the nozzle 215 after cleaning, but tap water or other similar water is also acceptable.

[0067] Furthermore, while the cleaning agent may be supplied in a fluid state, it is preferable to atomize it using the method described above and supply it to the nozzle 215 in mist form, accompanied by gas. The reason is that the same atomizing unit 220 used to atomize the film-forming raw materials in the film-forming process can be used, eliminating the need to necessarily prepare a dedicated device for supplying the cleaning agent, thus allowing the cleaning process to be carried out at a low cost. In addition, by incorporating such a cleaning method into the film-forming method for the crystalline oxide film 103, it is possible to manufacture the crystalline oxide film 103 at a low cost.

[0068] Cleaning with misted water can be realized by replacing the raw material solution 204a with water in Figure 2. Specifically, water is placed in the mist source 204 as the cleaning agent instead of the raw material solution 204a, and the ultrasonic transducer 206 is vibrated. This vibration is then transmitted to the water as the cleaning agent through the water 205a, thereby atomizing the water as the cleaning agent and generating mist which is supplied to the nozzle 215.

[0069] As shown in Figure 4, the film deposition apparatus 201a may have a separate cleaning water misting unit 260 in addition to the raw material misting unit 220. The cleaning water misting unit 260 is connected to the carrier gas source 202a and further connected to the supply pipe 209 via the cleaning agent piping 261. A cleaning agent flow rate control valve 227b is provided in the cleaning agent piping 261 to regulate the flow rate of the cleaning agent flowing through the cleaning agent piping 261. Furthermore, a raw material flow rate control valve 227a is provided in the middle of the supply pipe 209 downstream of the connection to the dilution carrier gas source 202b to regulate the flow rates of the mist and carrier gas flowing through the supply pipe 209. In this configuration, the cleaning water misting unit 260, the cleaning agent piping 261, the cleaning agent flow rate control valve 227b, and the carrier gas source 202a of the carrier gas supply unit 230 constitute the cleaning agent supply unit. In addition, the supply pipe 209, the carrier gas supply unit 230, the misting unit 220, and the raw material flow rate control valve 227a constitute the raw material supply unit. In other words, the raw material supply unit and the cleaning agent supply unit share the carrier gas source 202a. In this configuration, the destination of the carrier gas is switched depending on the process. For example, in the film formation process, the destination of the carrier gas can be switched to the misting unit 220 for raw materials, and in the cleaning process, the destination of the carrier gas can be switched to the cleaning water misting unit 260.

[0070] The following are specific examples of configurations for performing such operations. First, a computer is installed in the film deposition apparatus 201a as a control unit 240, which controls the opening and closing of the raw material flow rate control valve 227a in the raw material supply unit and the detergent flow rate control valve 227b in the detergent supply unit.

[0071] For example, when the control unit 240 opens the raw material flow rate control valve 227a and closes the detergent flow rate control valve 227b while the raw material solution 204a is in a state where it can be atomized and a carrier gas can also be supplied, the atomized film-forming raw material is supplied to the nozzle 215, enabling film formation.

[0072] On the other hand, after a predetermined time has elapsed since the start of film formation, when the cleaning water misting unit 260 is in a state where it can mist water as a cleaning agent and a carrier gas can also be supplied, the control unit 240 closes the raw material flow rate control valve 227a and opens the cleaning agent flow rate control valve 227b, so that the nozzle 215 is supplied with cleaning agent instead of film formation raw material, and the nozzle 215 can be cleaned.

[0073] In this way, after each predetermined period of film formation, the control unit 240 controls the raw material supply unit and the cleaning agent supply unit to supply a cleaning agent containing at least water to the nozzle 215 in liquid or gaseous form from the supply unit, thereby performing cleaning to remove any products adhering to the nozzle 215 during film formation. This makes it possible to automatically switch between the film formation process and the cleaning process.

[0074] The term "switching by the control unit 240" as used herein includes cases where the control unit 240 performs all operations necessary to switch between the film deposition process and the cleaning process, such as opening and closing the raw material flow rate control valve 227a and the cleaning agent flow rate control valve 227b. However, it also includes cases where, for example, after a certain period of time has elapsed since the start of film deposition, the control unit 240 illuminates a lamp or sounds a buzzer to prompt the worker to switch to cleaning, and the worker performs the opening and closing of the raw material flow rate control valve 227a and the cleaning agent flow rate control valve 227b.

[0075] Furthermore, the control unit 240 can switch between the film deposition process and the cleaning process even when using the film deposition apparatus 201 shown in Figure 2. In this case, the raw material supply unit also serves as the cleaning agent supply unit.

[0076] Furthermore, the switching between the film formation process and the cleaning process using the raw material flow rate adjustment valve 227a and the cleaning agent flow rate adjustment valve 227b is illustrative. For example, the control unit 240 may control these devices to alternately generate mist using the misting unit 220 and the cleaning water misting unit 260, thereby switching between the film formation process and the cleaning process. The control unit 240 is provided as needed, for example, when it is desired to automatically switch between the film deposition process and the cleaning process, but it is not essential. For example, if the switching between the film deposition process and the cleaning process is performed manually, the control unit 240 is not required.

[0077] In a configuration like the film deposition apparatus 201a, which includes a separate cleaning water misting unit 260 in addition to the raw material misting unit 220, there is an advantage in that there is no need to replace the raw material solution 204a with the cleaning agent in the mist generation source 204 during the cleaning process.

[0078] Steam cleaning can be performed, for example, with the film deposition apparatus 201b shown in Figure 5. In Figure 5, a steam source 250 is provided instead of the cleaning water misting unit 260, and the steam generated from the steam source 250 is supplied to the nozzle 215 via the supply pipe 209. The steam may be supplied to the nozzle 215 in a supersaturated state, or the dilution gas may be entrained with the steam by adjusting the flow control valve 251 provided in the piping connecting the dilution carrier gas source 202b and the steam source 250, and supplied to the nozzle 215 in an unsaturated state.

[0079] In this case as well, the film deposition apparatus 201b may be equipped with a control unit 240, and the control unit 240 may control the raw material flow rate control valve 227a of the raw material supply unit and the cleaning agent flow rate control valve 227b of the cleaning agent supply unit so that, after each film deposition operation over a predetermined period, a cleaning agent containing at least water is supplied to the nozzle 215 from the supply unit in liquid or gaseous form, thereby performing cleaning to remove the product adhering to the nozzle 215 during film deposition. However, even in this case, the control unit 240 is not essential, for example, if the switching between the film deposition process and the cleaning process is performed manually.

[0080] The product adhering to the nozzle 215 is thought to be a metal hydroxide from the raw material solution 204a. Therefore, when the nozzle 215 is cleaned with a cleaning agent containing water, the metal hydroxide product adhering to the nozzle 215 is thought to adsorb water, dissolve in the water, and be discharged from the system. Accordingly, the water and water vapor used as cleaning agents may also contain acids such as hydrochloric acid, hydrobromic acid, hydroiodic acid, acetic acid, and formic acid.

[0081] Thus, by supplying water or steam containing acid as a cleaning agent in the cleaning process, the reaction in which the product dissolves and is removed by the cleaning agent can be accelerated by the acid. Therefore, a high-quality crystalline oxide film 103 with a significantly reduced particle density on the film surface can be obtained in the subsequent film formation process.

[0082] In the cleaning process, it is preferable that the temperature of the nozzle 215, particularly the temperature of the outer wall of the nozzle 215, when supplying the cleaning agent to the nozzle 215 is 50 to 250°C. By setting the temperature of the nozzle 215 to 50°C or higher during the cleaning process, it is possible to suppress the residue of the cleaning agent on the nozzle surface after cleaning and to promote the reaction in which the product dissolves in the cleaning agent. Furthermore, by setting the temperature of the nozzle 215 to 250°C or lower during the cleaning process, it is possible to reliably cause the reaction in which the product dissolves in the cleaning agent and is removed. Therefore, a high-quality crystalline oxide film 103 with a significantly reduced particle density on the film surface can be obtained through the subsequent film formation process.

[0083] Specifically, as a means of controlling the temperature of the nozzle 215, when water vapor is used as a cleaning agent, the nozzle temperature changes according to the partial pressure of the water vapor, so a means of adjusting the partial pressure of the water vapor can be exemplified.

[0084] When a liquid, such as water, is used as the cleaning agent, the nozzle 215 can be heated on the substrate mounting stage 207b. In this case, the heater 208 is activated to heat the stage 207b, thereby heating the nozzle 215 through heat conduction between the stage 207b and the atmosphere in the deposition chamber 207a of the deposition apparatus 201.

[0085] Alternatively, a nozzle heating mechanism may be provided as a separate heating device from the heater 208, which heats the stage 207b, and heating may be performed using this mechanism. This nozzle heating mechanism may, for example, directly heat the nozzle with a heater, or run piping around or inside the nozzle to directly heat it using hot water or steam as a medium.

[0086] By heating the nozzle 215 with a separate heating device from the device that heats the stage 207b, the nozzle 215 can be heated to a high temperature with less heat than when the stage 207b is heated using the heater 208 that heats the stage 207b, and the nozzle 215 is heated by heat conduction through the atmosphere in the deposition chamber 207a and stage 207b, thereby reducing the cost of the cleaning process.

[0087] Furthermore, by heating the nozzle 215 with a separate heating device from the heater 208 that heats the stage 207b, the nozzle 215 can be heated more uniformly compared to when the nozzle 215 is heated by the heater 208, depending on the arrangement and structure of the heating device. As a result, unevenness in the degree of product removal depending on the position on the surface of the nozzle 215 is less likely to occur, and a high-quality crystalline oxide film 103 with a significantly reduced particle density on the film surface can be efficiently obtained in the subsequent film deposition process.

[0088] The supply time of water or steam as a cleaning agent in the cleaning process is determined appropriately according to the flow rate, temperature, etc., but 5 to 120 minutes is preferred.

[0089] Furthermore, it is preferable to interrupt the film deposition process after a predetermined time and perform a cleaning process, and to terminate the cleaning process after a predetermined time and resume the film deposition process. In other words, it is preferable to perform a cleaning process after each predetermined period of time during the film formation process.

[0090] By repeating the film deposition and cleaning processes in this manner, it is possible to prevent the product adhering to the nozzle from adhering to the film as particles, thereby improving film deposition efficiency. Efficiency is further improved by replacing the substrate 210 when interrupting the film deposition process.

[0091] The predetermined time is less than the time required for the product attached to the nozzle 215 during the film formation process to become a new particle source. For example, the relationship between the film formation process time and the number of particles attached to the crystalline oxide film 103 can be determined in an experiment, and the predetermined time is within an acceptable range for the number of attached particles.

[0092] (Formation of a buffer layer) As described above, a buffer layer may be provided between the substrate 210 and the crystalline oxide film 103 as appropriate. The method for forming the buffer layer is not particularly limited, and it can be formed by known methods such as sputtering and vapor deposition. However, when using the mist CVD method described above, the buffer layer can be formed simply by appropriately changing the composition of the raw material solution 204a.

[0093] Specifically, one or more metals selected from aluminum, gallium, chromium, iron, indium, rhodium, vanadium, titanium, and iridium can be suitably used as the raw material aqueous solution for the buffer layer by dissolving or dispersing them in water in the form of a complex or salt.

[0094] Examples of complex forms include acetylacetonate complexes, carbonyl complexes, ammine complexes, and hydride complexes. Examples of salt forms include metal chloride salts, metal bromide salts, and metal iodide salts.

[0095] Furthermore, solutions of the above metals dissolved in hydrobromic acid, hydrochloric acid, hydroiodic acid, etc., can also be used as aqueous salt solutions. In this case as well, the solute concentration is preferably 0.005 to 1 mol / L, and the dissolution temperature is preferably 20°C or higher. The buffer layer can be formed under other conditions in the same manner as described above. When a buffer layer is to be provided, the buffer layer is first formed on the substrate 210 to a predetermined thickness, and then the crystalline oxide film 103 is formed using the method described above.

[0096] In a special case of the buffer layer formation method, the same material as the crystalline oxide film 103 may be used as the buffer layer. In this case, the deposition temperature of the buffer layer may be higher than that of the crystalline oxide film 103. For example, the deposition temperature of the buffer layer may be 450°C and the deposition temperature of the crystalline oxide film 103 may be 400°C, or the buffer layer may be deposited at 500°C and the crystalline oxide film 103 at 450°C. Doing so will further improve the crystallinity of the crystalline oxide film 103.

[0097] (Heat treatment) Furthermore, a laminated structure comprising a crystalline oxide film 103 and a substrate 210, formed by the crystalline oxide film formation method according to the present invention, may be heat-treated at 200 to 600°C. This further removes unreacted species and other impurities from the crystalline oxide film 103, resulting in a higher quality laminated structure. The heat treatment may be carried out in air, an oxygen atmosphere, or under an inert gas atmosphere such as nitrogen or argon. The heat treatment time can be determined as appropriate, but for example, it can be 5 to 240 minutes.

[0098] (Peeling) In a laminated structure comprising a crystalline oxide film 103 formed by the crystalline oxide film formation method according to the present invention, the crystalline oxide film 103 may be peeled off from the substrate 210, which is the underlying substrate. The peeling means is not particularly limited and may be a known means. Examples of peeling methods include peeling by applying mechanical impact, peeling by applying heat and utilizing thermal stress, peeling by applying vibration such as ultrasonic waves, and peeling by etching. By such peeling, the crystalline oxide film 103 can be obtained as a self-supporting film. [Examples]

[0099] The present invention will be described in detail below with reference to examples, but this is not intended to limit the present invention. The following is a detailed procedure for comparing the physical properties of the crystalline oxide film deposited on the second substrate when two substrates 210 were sequentially placed in the deposition chamber 207a using the mist CVD method, with and without cleaning the nozzle 215 when switching substrates 210.

[0100] [Example 1] A film was deposited using the film deposition apparatus 201 shown in Figure 2. The film deposition apparatus 201 includes a carrier gas source 202a for supplying carrier gas, a flow control valve 203a for adjusting the flow rate of carrier gas discharged from the carrier gas source 202a, a dilution carrier gas source 202b for supplying dilution carrier gas, a flow control valve 203b for adjusting the flow rate of dilution carrier gas discharged from the dilution carrier gas source 202b, a mist generator 204 containing the raw material solution 204a, a container 205 containing water 205a, and an ultrasonic transducer 206 attached to the bottom of the container 205. The film deposition section 207 includes a stage 207b, a heater 208, and a quartz supply pipe 209 connecting the mist generator 204 to the film deposition section 207, and has a nozzle 215 inside the film deposition chamber 207a.

[0101] (Dummy film deposition) Using the apparatus, a dummy gallium oxide film was deposited on the first substrate as a crystalline oxide film 103. The substrate 210 was a 4-inch (100 mm) sapphire dummy substrate, which was placed in the film deposition section 207, and the heater 208 was set to 450°C and heated up.

[0102] The raw material solution 204a used ultrapure water as the solvent and gallium bromide as the solute. The gallium concentration in the raw material solution was 0.1 mol / L. This raw material solution 204a was placed inside the mist generating source 204. Subsequently, flow control valves 203a and 203b were opened to supply carrier gas from carrier gas source 202a and dilution carrier gas source 202b into the deposition chamber 207a. After the atmosphere in the deposition chamber 207a was sufficiently replaced with carrier gas, the flow rate of the carrier gas was adjusted to 4 NL / min and the flow rate of the dilution carrier gas was adjusted to 6 NL / min. Nitrogen was used as the carrier gas.

[0103] Next, the ultrasonic transducer 206 was vibrated at 2.4 MHz, and the vibrations were propagated through water 205a to the raw material solution 204a, thereby atomizing the raw material solution 204a and generating a mist. This mist was introduced into the deposition chamber 207a via the supply pipe 209 using a carrier gas, and the mist was subjected to a thermal reaction on the substrate 210 to form a thin film of gallium oxide on the substrate 210. The deposition time was 60 minutes. After deposition, it was observed that a white product had adhered to almost the entire outer wall of the nozzle from the nozzle outlet downstream.

[0104] (Nozzle cleaning) With heater 208 kept at 450°C, the nozzle temperature was approximately 180°C. In this state, the raw material solution 204a was replaced with ultrapure water to generate mist. The carrier gas flow rate was adjusted to 4 NL / min and the dilution carrier gas flow rate to 6 NL / min, and the mist was introduced into nozzle 215 and left for 30 minutes. As a result, it was confirmed that the white product on the outer wall of the nozzle had disappeared. After cleaning, the dummy substrate was removed.

[0105] (Deposition of gallium oxide film) Next, a gallium oxide film was deposited on the second substrate 210. A new 4-inch (100 mm) c-plane sapphire substrate was prepared as substrate 210. This substrate was placed on stage 207b in the deposition unit 207, the heater 208 was set to 450°C, the temperature was raised, and it was left for 30 minutes to stabilize the temperature in the deposition chamber 207a, including the nozzle 215.

[0106] The raw material solution 204a used ultrapure water as the solvent and gallium bromide as the solute. The gallium concentration in the raw material solution was 0.1 mol / L. This raw material solution 204a was placed inside the mist generating source 204. Subsequently, flow control valves 203a and 203b were opened to supply carrier gas from carrier gas source 202a and dilution carrier gas source 202b into the deposition chamber 207a. After the atmosphere in the deposition chamber 207a was sufficiently replaced with carrier gas, the flow rate of the carrier gas was adjusted to 4 NL / min and the flow rate of the dilution carrier gas was adjusted to 6 NL / min. Nitrogen was used as the carrier gas.

[0107] Next, the ultrasonic transducer 206 was vibrated at 2.4 MHz, and the vibrations were propagated through water 205a to the raw material solution 204a, thereby atomizing the raw material solution 204a and generating a mist. This mist was introduced into the deposition chamber 207a via the supply pipe 209 using a carrier gas, and the mist was subjected to a thermal reaction on the substrate 210 to form a thin film of gallium oxide on the substrate 210. The deposition time was 60 minutes.

[0108] (evaluation) X-ray diffraction was used to confirm the formation of α-Ga2O3 in the thin film formed on the second substrate 210. Measurement of the rocking curve of the (006) plane of α-Ga2O3 showed an extremely good crystallinity with a full width at half maximum of 7 seconds. For the rocking curve measurement, a 4-crystal monochromator, combining two channel-cut crystals, was used to enhance the monochromaticity of the X-rays and achieve higher precision. Next, the film thickness was measured at 25 points using a Filmetrics F50 reflection spectrometer, and the average film thickness was 583 nm. Furthermore, the film thickness variation, calculated as (maximum film thickness - minimum film thickness) / (maximum film thickness + minimum film thickness) × 100 (%), was a good 1.7%.

[0109] Furthermore, using an optical microscope, 69 points on the substrate surface were observed at 50x magnification to check for the presence or absence of particles on the film. No particles with a diameter of 0.3 μm or larger were found within the observed area. Calculating the particle density from the observed area, we obtained 29 / cm³. 2The following applies.

[0110] [Example 2] During the cleaning process, the nozzle 215 was left for 5 minutes with water mist introduced. Otherwise, film formation and evaluation were performed under the same conditions and methods as in Example 1.

[0111] [Example 3] During the cleaning process, the nozzle 215 was left for 120 minutes with water mist introduced. Otherwise, film formation and evaluation were performed under the same conditions and methods as in Example 1.

[0112] [Example 4] Using the film deposition apparatus 201b shown in Figure 5, saturated water vapor at 1 atmosphere was introduced instead of water mist during the cleaning process and left for 30 minutes. Film deposition and evaluation were performed under the same conditions and methods as in Example 1.

[0113] [Example 5] In the cleaning process, a 1.5 wt% aqueous solution of hydrochloric acid was used instead of water, atomized, and introduced into nozzle 215, where it was left for 30 minutes. Film formation and evaluation were performed under the same conditions and methods as in Example 1.

[0114] [Example 6] In the cleaning process, the heater temperature was adjusted to a nozzle temperature of 50°C, water mist was introduced into nozzle 215, and it was left for 30 minutes. Otherwise, film formation and evaluation were performed under the same conditions and methods as in Example 1.

[0115] [Example 7] During the cleaning process, the heater temperature was adjusted to set the nozzle temperature to 250°C, and water mist was introduced into nozzle 215 and left for 30 minutes. Film formation and evaluation were performed under the same conditions and methods as in Example 1.

[0116] [Comparative Example] In Example 1, after dummy film deposition, the second substrate 210 was placed on the stage 207b without performing a cleaning step, and film deposition and evaluation were performed under the same conditions and methods as in Example 1. The results are shown in Table 1 below.

[0117] [Table 1]

[0118] As shown in Table 1, in Examples 1 to 7, in which the crystalline oxide film 103 was formed using the crystalline oxide film formation method including the cleaning method of the present invention, it can be seen that the amount of particles adhering to the film was drastically reduced compared to the comparative example in which the crystalline oxide film 103 was formed without cleaning. Furthermore, in Examples 1 to 7, the full width at half maximum of the rocking curve was smaller than in the comparative example, and the crystallinity was also improved. This is thought to be because the incorporation of foreign matter into the crystalline oxide film 103 was suppressed.

[0119] As described above, according to the embodiments of the present invention, it was found that by cleaning the nozzle 215 during the film formation process, the number of particles adhering to the crystalline oxide film 103 can be drastically reduced, and a high-quality thin film with improved crystallinity can be obtained.

[0120] This specification includes the following embodiments: [1]: A film deposition apparatus comprising a stage for heating a substrate on which a substrate is placed, and a film deposition section having a nozzle for supplying a mist of a film deposition raw material containing gallium, accompanied by a carrier gas, to the substrate, wherein the supplied mist reacts on the heated substrate to deposit a crystalline oxide film mainly composed of gallium on the substrate, A method for cleaning a nozzle, characterized by performing a cleaning step to remove products adhering to the nozzle during film formation by supplying a cleaning agent containing at least water to the nozzle in a liquid or gaseous state. [2] In the cleaning process, The method for cleaning the nozzle according to [1] above, characterized in that the temperature of the nozzle is set to 50 to 250°C when supplying the cleaning agent to the nozzle. [3] In the cleaning process, The method for cleaning a nozzle according to [1] or [2] above, characterized in that water or steam containing acid is supplied as the cleaning agent. [4]: In the cleaning process, A method for cleaning a nozzle according to any one of the above [1] to [3], characterized in that the cleaning agent is supplied to the nozzle as the mist. [5]: The nozzle cleaning method according to any one of [1] to [4] above, characterized in that the stage is capable of accommodating the substrate having a diameter of 4 inches (100 mm) to 8 inches (200 mm). [6]: In the cleaning process, A method for cleaning a nozzle according to any one of the above [1] to [5], characterized in that the nozzle is heated with a heating device separate from the device that heats the stage. [7]: A mist of a film-forming raw material containing gallium, accompanied by a carrier gas, is supplied from a nozzle to a substrate placed on a heated stage, and the reaction is carried out on the substrate to form a crystalline oxide film mainly composed of gallium on the substrate. This film-forming process is performed for a predetermined time, A method for forming a crystalline oxide film, characterized by performing the cleaning step described in any of the above [1] to [6]. [8]: A film-forming apparatus comprising a stage for heating a substrate on which a substrate is placed, a film-forming section having a nozzle for supplying a mist of a film-forming material accompanied by a carrier gas to the substrate, and a material supply section for supplying the mist to the nozzle of the film-forming section, wherein the supplied mist reacts on the heated substrate to form a film on the substrate, A film-forming apparatus characterized by comprising a detergent supply unit that supplies a detergent containing at least water to the nozzle in liquid or gaseous form, [9]: The film-forming apparatus according to [8] above, characterized in that it includes a control unit that controls the raw material supply unit and the cleaning agent supply unit to perform cleaning to remove products adhering to the nozzle during film formation by supplying the cleaning agent to the nozzle from the cleaning agent supply unit each time film formation is performed for a predetermined period of time.

[0121] It should be noted that the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention. [Explanation of Symbols]

[0122] 100...Semiconductor device, 101...Underlayment substrate, 103...Crystalline oxide film, 103a...Insulating thin film, 103b...Semiconductor thin film, 105...Gate insulating film, 107...Gate electrode, 109...Source / drain electrodes, 110...Laminated structure, 201...Film deposition apparatus, 201a...Film deposition apparatus, 201b...Film deposition apparatus, 202a...Carrier gas source, 202b...Dilution carrier gas source, 203a...Flow control valve, 203b...Flow control valve, 204...Mist source, 204a...Raw material solution, 205...Container, 205a...Water, 206...Ultrasonic transducer, 207...Film deposition section, 207a...Film deposition chamber, 207b...Stage, 208...Heater, 209...Supply pipe, 210...Substrate, 216...Oscillator, 212...Exhaust port, 215...Nozzle, 220...Misting unit, 227a...Raw material flow rate control valve, 227b...Detergent flow rate control valve, 230...Carrier gas supply unit, 240...Control unit, 250...Steam source, 251...Flow rate control valve, 260...Cleaning water misting unit, 261...Detergent piping.

Claims

1. A film deposition apparatus is used that comprises a stage for heating a placed substrate and a film deposition section having a nozzle for supplying a mist of a film deposition raw material containing gallium, accompanied by a carrier gas, to the substrate, wherein the supplied mist reacts on the heated substrate to deposit a crystalline oxide film mainly composed of gallium on the substrate. A cleaning process is performed to remove the product adhering to the nozzle during film formation by supplying a cleaning agent containing at least water in a liquid or gaseous state to the nozzle. In the cleaning process described above, A method for cleaning a nozzle, characterized by heating the nozzle with a heating device separate from the device that heats the stage.

2. In the cleaning process described above, The nozzle cleaning method according to claim 1, characterized in that the temperature of the nozzle is set to 50 to 250°C when the cleaning agent is supplied to the nozzle.

3. In the cleaning process described above, The nozzle cleaning method according to claim 1, characterized in that water or steam containing acid is supplied as the cleaning agent.

4. In the cleaning process described above, The nozzle cleaning method according to claim 1, characterized in that the cleaning agent is supplied to the nozzle as a mist.

5. The nozzle cleaning method according to claim 1, characterized in that the stage is capable of accommodating the substrate having a diameter of 4 inches (100 mm) to 8 inches (200 mm).

6. Each time the film deposition process is performed for a predetermined time, a mist of a film-forming raw material containing gallium, accompanied by a carrier gas, is supplied from a nozzle to a substrate placed on a heated stage, and the reaction occurs on the substrate to form a crystalline oxide film mainly composed of gallium on the substrate, A method for forming a crystalline oxide film, characterized by performing the cleaning step described in any one of claims 1 to 5.

7. A film-forming apparatus comprising a film-forming section having a stage for heating a placed substrate, a nozzle for supplying a mist of film-forming raw materials accompanied by a carrier gas to the substrate, and a heater for heating the substrate, and a raw material supply section for supplying the mist to the nozzle of the film-forming section, wherein the supplied mist reacts on the heated substrate to form a film on the substrate, A film-forming apparatus characterized by comprising a cleaning agent supply unit that supplies a cleaning agent containing at least water to the nozzle in liquid or gaseous form, and a heating device separate from the heater for heating the nozzle.

8. The film-forming apparatus according to claim 7, further comprising a control unit that controls the raw material supply unit and the cleaning agent supply unit to perform cleaning to remove products adhering to the nozzle during film formation by supplying the cleaning agent to the nozzle from the cleaning agent supply unit each time film formation is performed for a predetermined period of time.

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