Method for manufacturing crystalline films

Abstract

To provide a method for manufacturing a crystal film useful for manufacturing semiconductor devices, electronic equipment, etc., by performing surface treatment on a substrate as an object, thereby modifying the surface of the substrate in an industrially advantageous manner and obtaining a substrate of higher quality.SOLUTION: A method for manufacturing a crystal film using a surface treatment apparatus 19 includes at least the following: treating an object 20, which is a substrate and / or a crystal layer having latent flaws, with a surface treatment agent containing hydrobromic acid (HBr) or hydroiodic acid (HI) in a treatment chamber 30 to reduce or eliminate the latent flaws, and depositing a crystal film by growing at least a portion of the surface treated surface is used as a crystal growth surface. The substrate and / or crystal layer has a corundum structure and the crystal film has a corundum structure.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a method for producing crystalline films useful in the manufacture of semiconductor devices, electronic devices, and the like. [Background technology]

[0002] Semiconductor devices using gallium oxide (Ga2O3), which has a large bandgap, are attracting attention as next-generation switching elements that can achieve high voltage resistance, low loss, and high heat resistance, and are expected to be applied to power semiconductor devices such as inverters. Moreover, due to its wide bandgap, it is also expected to be applied to light-emitting and light-receiving devices such as LEDs and sensors. The bandgap of gallium oxide can be controlled by mixing it with indium or aluminum, either individually or in combination, and it constitutes an extremely attractive material system as an InAlGaO-based semiconductor. Here, an InAlGaO-based semiconductor is In X Al Y Ga Z It exhibits the O3 property (0≦X≦2, 0≦Y≦2, 0≦Z≦2, X+Y+Z=1.5~2.5) and can be viewed as part of the same material system containing gallium oxide.

[0003] However, gallium oxide can develop latent defects during film formation and polishing, similar to those that occur during the polishing of SiC. These latent defects also exist within the sapphire substrate used for gallium oxide crystal growth, resulting in a problem where the properties of gallium oxide are not fully realized. Compared to SiC, gallium oxide is difficult to etch even with etching solutions such as HF. While techniques for etching substrates using liquid materials are known, such as immersion and spray methods, in recent years, the manufacturing process of semiconductor devices and electronic equipment has required the formation of submicron-order patterns. Therefore, there has been a strong demand for surface treatment methods that can control the surface treatment of objects at the nanoscale, which are useful in the manufacturing of semiconductor devices and electronic equipment.

[0004] Patent Document 1 discloses an etching method in which a sapphire substrate is immersed in phosphoric acid, sulfuric acid, or a mixture thereof heated to 200°C or higher to dissolve and remove the surface of the sapphire substrate. However, because this method uses strong acids, a safer processing method has been desired.

[0005] Patent Document 2 describes an etching process in which a micromist having an average particle size of 10 μm or less is sprayed onto the surface of a semiconductor wafer to dissolve and remove existing structures on the wafer. However, the etching method described in Patent Document 2 is still insufficient for etching gallium oxide, and an etching method that can effectively etch gallium oxide has been eagerly awaited.

[0006] Patent Document 3 describes a fine-channel mist etching apparatus, which uses an etching solution composed of an etching raw material consisting of hydrochloric acid or a mixture of hydrochloric acid and nitric acid, and a solvent consisting of pure water, to perform etching on an object to be etched, such as zinc oxide. However, the etching method described in Patent Document 3 makes it difficult to etch gallium oxide well, and there has been a need for an etching method that is industrially applicable with a small etching amount. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2007-137736 [Patent Document 2] Japanese Patent Publication No. 2009-010033 [Patent Document 3] Japanese Patent Publication No. 2011-181784 [Overview of the project] [Problems that the invention aims to solve]

[0008] One objective of the present invention is to provide a method for manufacturing a crystalline film that reduces latent defects originating from the substrate and / or crystalline layer, which is industrially advantageous. Another objective of the present invention is to provide a safer surface treatment method. [Means for solving the problem]

[0009] As a result of diligent research to achieve the above objective, the present inventors have found that a method for manufacturing a crystal film, comprising at least the following steps: surface treatment of a substrate and / or crystal layer having latent defects using a surface treatment agent to reduce or eliminate the latent defects; and formation of a crystal film by growing crystals on at least a portion of the surface of the surface-treated object as a crystal growth surface, wherein the substrate and / or crystal layer have a corundum structure, and the crystal film has a corundum structure, can industrially reduce or eliminate latent defects in the substrate and / or crystal layer and obtain a high-quality crystal film. Furthermore, they have found that such a method for manufacturing a crystal film can solve the above-mentioned conventional problems all at once. Furthermore, after obtaining the above findings, the inventors conducted further studies and completed the present invention.

[0010] In other words, the present invention relates to the following invention. [1] A method for producing a crystal film, comprising at least the steps of: reducing or eliminating latent defects by surface treatment of a substrate and / or crystal layer having latent defects using a surface treatment agent; and forming a crystal film by growing crystals on at least a portion of the surface of the surface-treated object as a crystal growth surface, wherein the substrate and / or crystal layer has a corundum structure, and the crystal film has a corundum structure. [2] The method according to [1] wherein the substrate and / or crystalline layer comprises at least aluminum and / or gallium. [3] The method according to [1], wherein the surface treatment agent is in the form of atomized droplets. [4] The method according to any one of [1] to [3], wherein the surface treatment agent comprises bromine. [5] The method according to any one of [1] to [3] above, wherein the surface treatment agent contains a hydroxide. [6] The method according to any one of [1] to [5] above, wherein the surface treatment temperature is 200°C or higher. [7] The method according to any one of [3] above, wherein the atomized droplets are those obtained by atomizing and suspending the surface treatment agent and then being transported using a carrier gas. [8] The method according to [7] above, wherein the carrier gas is an inert gas. [9] The method according to any one of [1] to [8] above, wherein the atomized droplets are those obtained by atomizing and suspending the surface treatment agent and then being transported using a carrier gas.

[10] A method for manufacturing a product using a method for manufacturing a crystal film, wherein the method for manufacturing the crystal film is the method for manufacturing a crystal film according to any one of [1] to [9].

[11] A method for manufacturing a product using the method for manufacturing a crystal film according to [1] above, wherein the crystal film is a crystal film without latent defects.

[12] A method for manufacturing a product using the method for manufacturing a crystal film according to [1] above, wherein the crystal layer is a single layer.

[13] A method for manufacturing a product using the method for manufacturing a crystal film according to [1] above, wherein the crystal layer is a multi-layer of two or more layers. [Effect of the Invention]

[0011] According to the method for manufacturing a crystal film of the present invention, it is possible to provide a method for manufacturing a crystal film that can advantageously reduce or eliminate latent defects in the substrate and / or the crystal layer industrially and obtain a high-quality crystal film. [Brief Description of the Drawings]

[0012] [Figure 1] It is a schematic configuration diagram of the surface treatment apparatus used in the examples. [Figure 2] The result of observing the latent defects before surface treatment in the examples using a microscope is shown. [[ID=3�]] [Figure 3] It is a diagram showing the microscope image after surface treatment in the examples. [Figure 4] As an example, the relationship between the etching amount of an object and the etching conditions when hydrobromic acid is used as the surface treatment agent is shown. [Figure 5] As an example, the relationship between the etching amount of an object and the etching conditions when hydroiodic acid is used as the surface treatment agent is shown.

Mode for Carrying Out the Invention

[0013] The method for manufacturing a crystal film of the present invention includes at least treating a substrate and / or a crystal layer having latent defects with a surface treatment agent to reduce or eliminate the latent defects, and forming a crystal film by growing crystals with at least a part of the surface-treated surface as a crystal growth surface. The substrate and / or the crystal layer have a corundum structure, and the crystal film has a corundum structure.

[0014] (Surface treatment agent) The surface treatment agent may be a known surface treatment agent. The surface treatment agent may contain an inorganic material or an organic material. In an embodiment of the present invention, it is preferable that the surface treatment agent is an etching agent. In a first aspect of the present invention, it is preferable that the surface treatment agent contains bromine or iodine because surface treatment can be performed better. More preferably, it contains hydrobromic acid (HBr) or hydroiodic acid (HI), and most preferably, it contains hydroiodic acid (HI). In a second aspect of the present invention, it is also preferable that the surface treatment agent contains a hydroxide. The solvent of the surface treatment agent is not particularly limited, but preferably an inorganic solvent, more preferably a polar solvent, and most preferably water. The concentration of the surface treatment agent is not particularly limited, but preferably 5% or more, more preferably 10% or more, and most preferably 20% by volume ratio with respect to the solvent of the surface treatment agent. The upper limit of the concentration is not particularly limited as long as atomization or droplet formation is possible. In an embodiment of the present invention, it is preferable that the surface treatment agent is in the form of atomized droplets.

[0015] (atomized droplets) The atomized droplets used in the embodiments of the present invention are suspended in the air, and are more preferably mist that can be transported as a gas with zero initial velocity, rather than being sprayed like a spray. The droplet size of the mist is not particularly limited and may be several millimeters in size, but is preferably 50 μm or less, and more preferably 1 to 10 μm. In the embodiments of the present invention, it is preferable that the method for generating the atomized droplets is an atomization method using ultrasonic vibration. The atomized droplets obtained using ultrasound are preferable because they have zero initial velocity and are suspended in the air, and are very preferable because they can be transported as a gas with zero initial velocity, rather than being sprayed like a spray, so there is no damage due to collision energy. In the present invention, it is preferable that the atomized droplets are formed by atomizing the etching solution and then transported using a carrier gas.

[0016] (Objects to be surface treated) The object to be surface-treated is preferably an etchable object that can be etched using the atomized droplets. The material of the etchable object is not particularly limited as long as it does not hinder the objective of the present invention, and may be a known material, and may be an organic compound or an inorganic compound. The shape of the etchable object may be any shape and is effective for all shapes, such as plates such as flat plates and discs, films, fibers, rods, cylinders, prismatics, tubes, spirals, spheres, and rings. In the present invention, the etchable object is preferably a film. In embodiments of the present invention, the etchable object preferably contains at least aluminum and / or gallium, more preferably an oxide containing aluminum and / or gallium, even more preferably aluminum oxide and / or gallium oxide, and most preferably gallium oxide. Furthermore, in embodiments of the present invention, the substrate and / or crystalline layer of the etchable object has a corundum structure.

[0017] The object may be a substrate or a layer integrated with a substrate, and in one embodiment of the present invention, it is preferable that it is laminated directly on a substrate or via another layer. The substrate is not particularly limited as long as it can support the object to be etched. Furthermore, at least a part of the substrate may be included in the object to be etched. The material of the substrate is also not particularly limited as long as it does not hinder the objective of the present invention, and may be a known substrate, an organic compound or an inorganic compound. The shape of the substrate may be any shape and is effective for all shapes, for example, plate-like such as a flat plate or disc, fibrous, rod-like, cylindrical, prismatic, tubular, spiral, spherical, ring-like, etc., but in the present invention, a substrate is preferred. The thickness of the substrate is not particularly limited in the present invention.

[0018] In embodiments of the present invention, the substrate may be the object, the crystalline layer formed on the substrate may be the object, or the crystalline layer formed on the substrate and at least a part of the substrate may be the object. The crystalline layer may be a single layer or a multilayer consisting of two or more layers. In embodiments of the present invention, the substrate is preferably in the form of a plate. Furthermore, if the object is a crystalline layer formed on the substrate, the substrate is not particularly limited as long as it serves as a support for the object. It may be an insulating substrate, a semiconductor substrate, or a conductive substrate, but it is preferable that the substrate is an insulating substrate, and it is also preferable that the substrate has a metal film on its surface. Preferably, the substrate is, for example, a substrate having a corundum structure. The substrate material is not particularly limited as long as it does not hinder the objective of the present invention, and may be a known material. As the substrate having a corundum structure, for example, it may be a substrate having a corundum structure on at least a part of its surface. Furthermore, the substrate may be mainly composed of a substrate material having a corundum structure, and more specifically, examples include a sapphire substrate (preferably a c-plane sapphire substrate) and an α-type gallium oxide substrate. Here, "main component" means that the substrate material having the specific crystal structure is preferably present in an atomic ratio of 50% or more, more preferably 70% or more, and even more preferably 90% or more of the total components of the substrate material, and may be 100%. The method for stacking the etching target on the substrate may be a known method.

[0019] In embodiments of the present invention, a buffer layer including a stress relaxation layer or the like may be provided on the substrate. In one embodiment of the present invention, it is preferable that the substrate has a buffer layer on part or all of its surface. The buffer layer may be a crystalline layer in one embodiment of the manufacturing method of the present invention. The buffer layer may also be a crystalline film in one embodiment of the present invention. In embodiments of the present invention, the method for forming the crystalline layer and / or crystalline film is not particularly limited, and known methods may be used. In this specification, the term "crystalline film" is used for convenience to distinguish a film or layer in which latent defects are reduced or eliminated compared to an object requiring surface treatment. Examples of the forming method include the spray method, mist CVD method, HVPE method, MBE method, MOCVD method, sputtering method, etc. In the present invention, it is preferable that the crystalline layer and / or crystalline film is formed by the mist CVD method because it can improve the film quality of the crystalline layer and / or crystalline film, and in particular, it can suppress crystal defects such as tilt. A preferred embodiment for forming the buffer layer by the mist CVD method will be described in more detail below.

[0020] The crystalline layer and / or crystalline film can preferably be formed, for example, by atomizing the raw material solution (atomization step), transporting the resulting atomized droplets (including mist) to the substrate using a carrier gas (transportation step), and then subjecting the atomized droplets to a thermal reaction on part or all of the surface of the substrate (crystalline layer and / or crystalline film formation step).

[0021] (Atomization process) In the atomization step, the raw material solution is atomized to obtain atomized droplets. The method for atomizing the raw material solution is not particularly limited as long as it can atomize the raw material solution, and any known method may be used. However, in the above embodiment of the present invention, it is preferable to obtain atomized droplets by transmitting ultrasonic vibrations to the raw material solution. The atomized droplets obtained by transmitting ultrasonic vibrations are preferable because they have zero initial velocity and float in the air. For example, they are atomized droplets that can be transported as a gas by floating in space, rather than being sprayed like a spray, so there is no damage due to collision energy, making them very preferable. The droplet size of the atomized droplets is not particularly limited and may be several millimeters in size, but is preferably 50 μm or less, and more preferably 0.1 to 10 μm.

[0022] (Raw material solution) The raw material solution is not particularly limited as long as it is a solution from which the crystalline layer and / or crystalline film can be obtained by mist CVD. In one embodiment, the composition of the raw material solution for the crystalline layer and the composition of the raw material solution for the crystalline film may be the same. In another embodiment, the composition of the raw material solution for the crystalline layer and the composition of the raw material solution for the crystalline film may be different. Examples of the raw material solution include an organometallic complex of the atomizing metal (e.g., acetylacetonate complex) or an aqueous solution of a halide (e.g., fluoride, chloride, bromide, or iodide). The atomizing metal is not particularly limited, and examples of such atomizing metals include one or more metals selected from aluminum, gallium, indium, iron, chromium, vanadium, titanium, rhodium, nickel, cobalt, and iridium. In embodiments of the present invention, it is preferable that the atomizing metal contains at least gallium, indium, or aluminum, and more preferably at least gallium. The content of the atomizing metal in the raw material solution is not particularly limited as long as it does not hinder the objective of the present invention, but is preferably 0.001 mol% to 50 mol%, and more preferably 0.01 mol% to 50 mol%.

[0023] Also, as one of the embodiments, it is preferable that the raw material solution contains a dopant. By including a dopant in the raw material solution, the conductivity of the crystal layer and / or crystal film can be easily controlled without performing ion implantation or the like and without breaking the crystal structure. In the present invention, the dopant is preferably tin, germanium, or silicon, more preferably tin or germanium, and most preferably tin. The concentration of the dopant is usually about 1×10 16 / cm 3 ~1×10 22 / cm 3 and may be so, or the concentration of the dopant may be, for example, a low concentration of about 1×10 17 / cm 3 or less, or the dopant may be contained at a high concentration of about 1×10 20 / cm 3 or more. In the present invention, the concentration of the dopant is preferably 1×10 20 / cm 3 or less, and more preferably 5×10 19 / cm 3 or less.

[0024] The solvent of the raw material solution is not particularly limited, and may be an inorganic solvent such as water, an organic solvent such as alcohol, or a mixed solvent of an inorganic solvent and an organic solvent. In the present invention, it is preferable that the solvent contains water, more preferably water or a mixed solvent of water and alcohol, and most preferably water. More specifically, examples of the water include pure water, ultrapure water, tap water, well water, mineral water, mineral water, hot spring water, spring water, fresh water, seawater, etc. In the present invention, ultrapure water is preferable.

[0025] (Transportation step) In the transport process, the mist or droplets are transported into the film deposition chamber by a carrier gas. The carrier gas is not particularly limited as long as it does not hinder the objective of the present invention, and suitable examples include inert gases such as oxygen, ozone, nitrogen, and argon, or reducing gases such as hydrogen gas and foaming gas. There may be one type of carrier gas, or there may be two or more types, and a dilution gas with a reduced flow rate (e.g., a 10-fold dilution gas) may be used as a second carrier gas. There may also be two or more locations for supplying the carrier gas, not just one. The flow rate of the carrier gas is not particularly limited, but is preferably 0.01 to 20 L / min, and more preferably 1 to 10 L / min. In the case of a dilution gas, the flow rate of the dilution gas is preferably 0.001 to 2 L / min, and more preferably 0.1 to 1 L / min.

[0026] (Process for forming crystalline layers and / or crystalline films) In the step of forming a crystalline layer and / or crystalline film, the crystalline layer or crystalline film is formed on the substrate by thermally reacting the atomized droplets in the film formation chamber. The thermal reaction only needs to involve the reaction of the atomized droplets with heat, and the reaction conditions are not particularly limited as long as they do not hinder the objectives of the present invention. In this step, the thermal reaction is usually carried out at a temperature above the evaporation temperature of the solvent, but is preferably not too high (e.g., 1000°C or lower), more preferably 650°C or lower, and most preferably between 400°C and 650°C. Furthermore, the thermal reaction may be carried out under any atmosphere, such as vacuum, a non-oxygen atmosphere, a reducing gas atmosphere, or an oxygen atmosphere, as long as it does not hinder the objectives of the present invention, and may also be carried out under any conditions, such as atmospheric pressure, pressurized pressure, or reduced pressure, but in the present invention, it is preferable to carry it out under atmospheric pressure. The thickness of the formed layer or film can be set by adjusting the formation time.

[0027] As described above, after forming a buffer layer on part or all of the surface of the substrate, the crystal film is formed on the buffer layer using the film formation method of the present invention described above. This makes it possible to further reduce defects such as tilt in the crystal film and to improve the film quality.

[0028] Furthermore, the crystalline layer and / or crystalline film are not particularly limited, but in the embodiments of the present invention, it is preferable that they mainly contain a metal oxide. Examples of the metal oxide include metal oxides containing one or more metals selected from aluminum, gallium, indium, iron, chromium, vanadium, titanium, rhodium, nickel, cobalt, and iridium. In the present invention, it is preferable that the metal oxide contains one or more elements selected from indium, aluminum, and gallium, more preferably contains at least indium and / or gallium, and most preferably contains at least gallium. In the present invention, "main component" means that the metal oxide is preferably present in an atomic ratio of 50% or more, more preferably 70% or more, and even more preferably 90% or more, of the total components of the buffer layer, and may be 100%.

[0029] It goes without saying that if a crystal layer with few or no latent defects is obtained when a crystal layer is formed using the method for forming the crystal layer and / or crystal film described in this application, depending on the substrate conditions, the etching treatment described below may be omitted. Furthermore, the substrate surface treatment can be performed before forming the crystal layer on the substrate. By forming a crystal layer on a substrate without latent defects, it is possible to obtain a crystal film with reduced latent defects or a defect-free film. A crystal layer without latent defects may be used as a buffer layer or as a crystal film. On the other hand, there are cases where the presence of latent defects becomes apparent only after the crystal layer has been formed, and in one embodiment of the present invention, the object to be surface treated may be the crystal layer. In this case, the object may be the crystal layer formed on the substrate and at least a part of the substrate.

[0030] In embodiments of the present invention, the surface treatment is performed on the object using the atomized droplet containing the etching solution at a temperature of 200°C or higher. Embodiments of the present invention are not particularly limited as long as the etching treatment can be performed at a surface treatment temperature of 200°C or higher. In embodiments of the present invention, it is preferable that the treatment temperature is 300°C or higher. Furthermore, in embodiments of the present invention, it is preferable that the surface treatment is performed by reacting the atomized droplet with the object to be etched. The surface treatment temperature here refers to the temperature of the object to be etched.

[0031] In embodiments of the present invention, it is preferable to transport the atomized droplets using a carrier gas. The carrier gas is not particularly limited as long as it does not hinder the objective of the present invention, and suitable examples include inert gases such as oxygen, ozone, nitrogen, and argon, or reducing gases such as hydrogen gas and foaming gas. The carrier gas may be of one type, or it may be of two or more types, and a dilution gas with a reduced flow rate (e.g., a 10-fold dilution gas) may be used as a second carrier gas. The carrier gas may also be supplied from two or more locations, not just one. The flow rate of the carrier gas is not particularly limited, but is preferably 0.01 to 20 L / min, and more preferably 1 to 10 L / min. In the case of a dilution gas, the flow rate of the dilution gas is preferably 0.001 to 2 L / min, and more preferably 0.1 to 1 L / min.

[0032] The reaction described above is acceptable as long as it allows the etching target to be etched using the atomized droplets, and may include chemical reactions or thermal reactions. In embodiments of the present invention, the etching process is usually carried out at a temperature of 200°C or higher, but in embodiments of the present invention, 350°C or higher is preferred, and 400°C or higher is more preferred. In embodiments of the present invention, even at such high temperatures, the etching process is carried out by increasing the temperature of the etching target rather than raising the temperature of the strong acid etching solution, thus enabling stable and effective etching of the etching target. The upper limit is not particularly limited as long as it does not hinder the objective of the present invention, but 1900°C or lower is preferred, and 1400°C or lower is more preferred. Furthermore, the reaction may be carried out under any of the following atmospheres, as long as it does not hinder the objective of the present invention, but it is preferred to be carried out under a non-oxygen atmosphere or an oxygen atmosphere, and it is more preferred to be carried out under an inert gas atmosphere. Furthermore, it may be carried out under any of the following conditions, such as atmospheric pressure, pressurized, or reduced pressure, but in embodiments of the present invention, it is preferred to be carried out under atmospheric pressure. The etching amount can be set by adjusting the etching process time.

[0033] The etching method described above is carried out using an etching apparatus comprising, for example, an atomizing unit that generates atomized droplets by atomizing an etching solution and suspending the droplets, a transporting unit that transports the atomized droplets generated in the atomizing unit with a carrier gas, and an etching unit that etches the object to be etched with the atomized droplets, wherein the etching unit is equipped with a heater that heats the object to be etched to a temperature of 200°C or higher. In one embodiment of the present invention, it is preferable that the etching unit is equipped with a heater that can heat the object to be etched to a temperature of 400°C or higher. The object to be etched may be placed directly on the heater, or it may be placed indirectly via other layers or spaces. In the embodiment of the present invention, it is also preferable that the heater is a hot plate. In the embodiment of the present invention, it is also preferable that the etching unit has a retention structure that retains the atomized droplets. According to this preferred embodiment, it is possible to achieve better etching amount and etching quality than the fine channel method.

[0034] Furthermore, after the etching process, a crystalline film is formed on the etched surface. The crystalline film may be a buffer layer, a semiconductor layer, an insulating layer, or a conductive layer. In one embodiment of the present invention, the crystalline film may be a buffer layer, and a crystalline oxide semiconductor film may be formed on the buffer layer. Also, in another embodiment of the present invention, it is preferable to form a crystalline oxide semiconductor film as the crystalline film on the etched surface. Furthermore, the constituent materials of the crystalline film and the buffer layer are not particularly limited as long as they do not hinder the objective of the present invention, and the constituent materials of the crystalline film and the buffer layer may be the same or different. The shape of the crystalline film is also not particularly limited, and if a buffer layer is provided, it may be the same as the shape of the buffer layer. The crystal structure of the crystalline film is not particularly limited, but in the embodiments of the present invention, a corundum structure is more preferable. The above method can be used to form the crystalline layer and the crystalline film.

[0035] The method for manufacturing a crystalline film in the embodiments of the present invention can be applied to the manufacturing processes of various products, and is preferably used in the manufacturing processes of semiconductor devices. Examples of semiconductor devices include diodes, transistors, and JBS. Examples of products other than semiconductor devices include CPU-equipped electronic devices such as digital cameras, printers, projectors, personal computers, and mobile phones, power supply unit-equipped electronic devices such as vacuum cleaners and irons, motors, drive mechanisms, electric vehicles, electric airplanes, small electric devices, and MEMS drive electronic devices. [Examples]

[0036] The following describes embodiments of the present invention, but the present invention is not limited to these embodiments.

[0037] (Example 1) 1. Surface treatment equipment The surface treatment apparatus 19 used in this embodiment will be explained with reference to Figure 1. The surface treatment apparatus 19 in Figure 1 comprises a carrier gas supply source 22a for supplying carrier gas, a flow control valve 23a for adjusting the flow rate of carrier gas discharged from the carrier gas supply source 22a, a carrier gas (dilution) source 22b for supplying carrier gas (dilution), a flow control valve 23b for adjusting the flow rate of carrier gas (dilution) discharged from the carrier gas (dilution) source 22b, a mist generation source 24 containing etching solution 24a, a container 25 for water 25a, an ultrasonic transducer 26 attached to the bottom of the container 25, an etching chamber 30 which is the etching section, a quartz supply pipe 27 connecting the mist generation source 24 to the etching chamber 30, and a hot plate 28 which is a heater installed in the etching chamber 30. A sapphire substrate 20 with a crystalline layer formed on its surface is placed on the hot plate 28 as the object to be treated. The crystal layer was formed using the mist CVD method with a gallium acetylacetonate solution (0.025 M) as the starting solution, 5% hydrobromic acid (HBr) as an additive, and N2 as the carrier gas (carrier gas flow rate 1 L / min, dilution carrier gas flow rate 1 L / min), with a film deposition time of 10 minutes. The sapphire substrate and the crystal layer 20 had latent defects. These latent defects included not only defects originating from the sapphire substrate but also defects in the buffer layer caused during buffer layer formation. Figure 2 shows the results of observing the latent defects before etching using a microscope. In addition, the etching chamber 30 is provided with an exhaust port at a high position on the side wall, and is configured so that atomized droplets accumulate around the etching target 20.

[0038] 2. Preparation of etching solution Hydrobromic acid was mixed with ultrapure water to a volume ratio of 20%, and this was used as the etching solution.

[0039] 3. Etching preparation The etching solution 24a obtained in step 2 above was placed inside the mist generating source 24. Next, a sapphire substrate 20 with an α-Ga2O3 film formed on its surface as a buffer layer was placed on a hot plate 28, and the hot plate 28 was operated to raise the temperature of the sapphire substrate with the α-Ga2O3 film formed on its surface as a crystal layer to 500°C, using the substrate as the object 20. Nitrogen was used as the carrier gas.

[0040] 4. Surface treatment Next, the ultrasonic transducer 26 was vibrated at 2.4 MHz, and the vibration was propagated through water 25a to the etching solution 24a, thereby atomizing the etching solution 24a and generating atomized droplets (including mist) 24b. These atomized droplets 24b were introduced into the processing chamber 30 through the supply pipe 27 by a carrier gas, and under atmospheric pressure and a surface treatment temperature of 500°C, the atomized droplets reacted on a sapphire substrate (object 20) on which an α-Ga2O3 film had been formed as a crystalline layer, thereby performing surface treatment of the object 20. The processing time was 6 hours. At least a portion of the surface of the surface-treated object was used as a crystal growth surface, and a crystalline film was formed again under the same conditions as the crystalline layer. The areas corresponding to the locations of latent defects shown in Figure 2 were observed with a microscope to confirm the presence or absence of latent defects. The observation results are shown in Figure 3. As is clear from Figures 2 and 3, in the crystalline film formed on the etched surface after the etching treatment as a surface treatment, the latent defects have disappeared, resulting in a defect-free film.

[0041] (Example 2) Furthermore, hydrobromic acid (HBr 20%) was used as the surface treatment agent, and the etching amount and etching conditions were as shown in Figure 4. Except for this, the procedure was the same as in Example 1, with α-Ga2O3 films formed as crystalline layers on sapphire substrates with different surface orientations. Etching treatment was then performed on the surface of the target object. Figure 4 shows the relationship between the etching amount and conditions of the etching treatment. In Figure 4, "c," "m," and "r" indicate the surface orientation of the sapphire substrate, respectively. In this example, the surface treatment of the target object was performed well in all surface orientations, but it can be seen that the surface treatment was particularly well performed in all surface orientations when the surface treatment temperature was 300°C or higher.

[0042] (Example 3) Furthermore, except that hydroiodic acid (HI 20%) was used as the surface treatment agent instead of hydrobromic acid, and the etching conditions are shown in Figure 5, the same procedure as in Example 1 was used to form α-Ga2O3 films as crystalline layers on sapphire substrates with different surface orientations, and etching was performed as the surface treatment of the objects. Figure 5 shows the relationship between the etching amount and the etching conditions. In Figure 5, "c," "m," and "r" indicate the surface orientation of the sapphire substrate, respectively. It can be seen that the surface treatment of the objects was performed well in all surface orientations. After etching, a crystalline film was formed on the surface-treated surface of the objects in the same manner as in Example 1. As a result, for objects that had latent defects, a defect-free crystalline film was obtained with the latent defects eliminated, similar to Example 1.

[0043] Furthermore, it is also possible to perform the above surface treatment on a substrate, and since there is no crystalline layer on the substrate, the surface treatment can be performed in a shorter time. Therefore, according to the embodiment of the present invention, by performing surface treatment on a substrate, the surface of the substrate can be modified in an industrially advantageous manner, and a higher quality substrate can be obtained.

[0044] (Comparative Example 1) The object was etched in the same manner as in Example 1, except that hydrobromic acid was used instead of an etching solution prepared by mixing sulfuric acid and phosphoric acid in a 1:1 volume ratio. After the etching process, a crystalline film was formed on the etched surface in the same manner as in Example 1, and the crystalline film became cloudy after 15 minutes from the start of film formation. [Industrial applicability]

[0045] The method for manufacturing a crystalline film in the embodiments of the present invention can be used in various manufacturing fields such as semiconductor devices and electronic equipment because it allows for the industrially advantageous production of high-quality crystalline films. Furthermore, according to the embodiments of the present invention, surface treatment of objects including substrates and / or crystalline layers can be performed more safely. [Explanation of symbols]

[0046] 19 Surface treatment equipment 20 Objects 22a Carrier gas supply source 22b Carrier gas (dilution) supply source 23a Flow control valve 23b Flow control valve 24 Mist Sources 24a Etching solution 24b Atomized droplets 25 Container 25a water 26. Ultrasonic transducer 27 Supply pipe 28. Heater (hot plate) 30 Processing Rooms

Claims

1. A method for producing a crystalline film, comprising at least the steps of: surface-treating a substrate and / or crystalline layer with a surface treatment agent; forming a crystalline film by growing crystals on at least a portion of the surface-treated surface of the substrate and / or crystalline layer as a crystal growth surface, wherein the substrate and / or crystalline layer has a corundum structure, the crystalline film has a corundum structure, and the surface treatment agent contains bromine, iodine, or hydroxide.

2. A method for producing a crystalline film, comprising at least the steps of: surface-treating a substrate and / or crystalline layer with a surface treatment agent; forming a crystalline film by growing crystals on at least a portion of the surface-treated surface of the substrate and / or crystalline layer as a crystal growth surface, wherein the substrate and / or crystalline layer has a corundum structure, the crystalline film has a corundum structure, and the surface treatment agent contains hydrobromic acid or hydroiodic acid.

3. The method for producing a crystalline film according to claim 1 or claim 2, wherein the surface treatment agent is an etching agent.

4. A method for producing a crystalline film according to any one of claims 1 to 3, wherein the substrate and / or crystalline layer comprises at least aluminum and / or gallium.

5. A method for producing a crystalline film according to any one of claims 1 to 4, wherein the surface treatment agent is in the form of atomized droplets.

6. The method for producing a crystalline film according to claim 5, wherein the atomized droplets atomize and suspend the surface treatment agent, and then transport it using a carrier gas.

7. The method for producing a crystalline film according to claim 6, wherein the carrier gas is an inert gas.

8. A method for producing a crystalline film according to any one of claims 1 to 7, wherein the surface treatment temperature is 200°C or higher.

9. The method for manufacturing a crystalline film according to any one of claims 1 to 8, wherein the crystalline film has reduced latent defects compared to the crystalline layer.

10. The method for producing a crystalline film according to any one of claims 1 to 9, wherein the crystalline film is a flawless crystalline film.

11. The method for producing a crystalline film according to any one of claims 1 to 10, wherein the crystalline layer is a single layer.

12. The method for producing a crystalline film according to any one of claims 1 to 11, wherein the crystalline layer is a multilayer of two or more layers.

13. A method for manufacturing a semiconductor device using a method for manufacturing a crystalline film, wherein the method for manufacturing the crystalline film is the method for manufacturing a crystalline film described in any one of claims 1 to 12.

14. A method for manufacturing a product using a method for manufacturing a crystalline film, wherein the method for manufacturing the crystalline film is the method for manufacturing a crystalline film described in any one of claims 1 to 12.

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