JP2014156622A - Thin film formation method and thin film formation apparatus by atmospheric pressure induction coupling plasma - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin film formation method and an apparatus therefor capable of forming various thin films on a product to be processed by utilizing atmosphere pressure induction coupling plasma.SOLUTION: Plasma gas 31 is introduced into a plasma generation space 40, and atmosphere pressure induction coupling plasma 10 is generated by plasma generation means 5. Mist 64 of a solution containing a reaction material 61 is generated by mist generation means 2, and the mist is introduced into the plasma generation space together with mist transfer gas 32. While controlling an oxidative atmosphere or a reduction atmosphere in the atmosphere pressure induction coupling plasma by controlling high-frequency power imparted to the plasma generation means, a thin film containing at least a partial component of the reaction material is formed on a product 8 to be processed.

Description

  The present invention relates to a technique for forming a thin film by atmospheric pressure inductively coupled plasma, and in particular, a thin film forming method for forming a thin film of various compositions by supplying a solution containing a reactive material in the plasma as a mist, and the thin film formation used therein Relates to the device.

  Plasma is generated by applying electric power or electromagnetic energy to plasma gas. Plasma is a state in which positively and negatively charged particles (typically positive ions and electrons) move freely, and ions, radicals, atoms, and electrons exist in an electrically neutral state as a whole. is there. Many ions and radicals (active excitation molecules) existing in plasma can be used for various treatments. For example, it is used for hydrophilization of films and resins, thin film formation, reduction treatment of metal oxide films, etching, doping, washing, analysis of trace elements, reaction of compounds, synthesis, polymerization of polymers, and the like.

  The method of generating plasma can be appropriately selected according to the intended application, but in general, the method of generating plasma by high-frequency discharge in a vacuum is compared to the method of generating plasma at atmospheric pressure. The radical species has a long life and can stably generate plasma. Especially in the fields of semiconductors and liquid crystal display devices, reactive gases are supplied to form films by CVD (Chemical Vapor Deposition). Etching, surface cleaning, oxidation, and the like were performed. On the other hand, the method of generating plasma under atmospheric pressure does not require an evacuation system, so that the facilities are simple and the size of the object to be processed is small. It is difficult and has been used for applications that require relatively no plasma control, such as metal fusing and analysis sample decomposition.

  Conventionally, a plasma CVD method, which is a film forming method using plasma, has been used for forming a semiconductor film (Si film, etc.) and an insulating film (silicon oxide film, silicon nitride film, etc.). For example, when a thin film such as a semiconductor material is to be formed by CVD using plasma under vacuum, a special gas (monosilane, phosphine, or the like) is introduced as a source gas, and the thin film is formed by plasma. However, such special gases are expensive and highly toxic, which is dangerous to handle. As a method of forming a metal film using plasma, plasma MOCVD (Metal, which forms a metal film (for example, aluminum, gold, copper, etc.) by introducing a gas or vapor of an organometallic material into ECR plasma. Organic CVD) was known.

  On the other hand, in recent years, there have been a few proposals that use not only gases but also liquids as raw materials. For example, Patent Document 1 discloses a plasma system that treats the surface of a substrate using atmospheric pressure plasma in a non-thermal equilibrium state. The plasma system described in Patent Document 1 includes an electrode disposed in a process gas atmosphere in a housing, means for applying a high-frequency voltage to the electrode, an atomizer for a surface treatment agent disposed in the housing, and the like. Is provided. According to such a plasma system, it is said that non-thermal equilibrium atmospheric pressure plasma containing an atomized surface treatment agent is generated, and the surface of the substrate can be coated using the atmospheric pressure plasma.

  Patent Document 2 discloses a liquid introduction plasma apparatus capable of directly introducing a liquid such as an analysis sample or a CVD raw material into plasma. The liquid-introduced plasma device described in Patent Document 2 includes a plasma generation chamber configured by a cylindrical body having an opening at one end, a spray device that sprays liquid from the spray port into the plasma generation chamber using a spray gas, and the like. In such a plasma apparatus, since a liquid such as an analysis sample can be directly introduced into the plasma, it is said that a high analysis capability can be realized even with a very small amount of liquid.

Special table 2008-519411 JP 2006-202541 A

  In the plasma system described in Patent Document 1, various plasma gases and various surface treatment agents can be used, and it is described that, as an example, a fluorocarbon coating and a methacrylate coating could be formed. However, the plasma system described in Patent Document 1 uses low-temperature plasma generated by a glow discharge method or the like. Low-temperature plasma is a non-equilibrium plasma in which the temperature of ions and neutral particles is low although the electron temperature is high, and the plasma reaction is relatively easy to control, but the chemical reaction rate is low. In contrast, high-temperature plasma (thermal plasma) has a high particle density, and the temperature of ions and neutral particles is almost equal to the electron temperature. The chemical reaction rate is higher than that of low-temperature plasma, but it must be controlled. Was relatively difficult.

  Further, in the plasma system described in Patent Document 1, since the electrode for generating plasma is arranged in the housing, the metal component in the electrode may be mixed into the plasma as an impurity and may affect the surface treatment. is there.

  Patent Document 2 discloses a technique for introducing a liquid such as a sample into a plasma generation chamber for generating plasma in a plasma apparatus including a liquid introduction plasma torch and a liquid introduction parallel plate plasma source. In Patent Document 2, in addition to an analysis sample, a liquid such as a CVD raw material or a liquid mixture can be introduced into plasma and used for plasma processing such as surface modification, surface treatment, etching, and CVD of a substance such as metal. It is also described. However, Patent Document 2 describes a specific CVD raw material, a thin film formed by CVD, and a specific method for forming a thin film on a substrate by reacting the CVD raw material in plasma. As a specific application, only a method of analyzing a small amount of sample by introducing a liquid containing the analysis sample into the plasma generation chamber is described.

  The present invention is based on this technology, and is easy to handle and forms various thin films on an object to be processed using atmospheric pressure inductively coupled plasma (high temperature plasma) having a high chemical reaction rate. It is an object of the present invention to provide a method and a thin film forming apparatus that can be used.

  In order to solve the above-mentioned problem, the thin film formation method using atmospheric pressure inductively coupled plasma according to the present invention introduces a plasma gas into a plasma generation space, generates atmospheric pressure inductively coupled plasma by the plasma generating means, and generates mist generating means. To generate a mist of a solution containing a reaction material, introduce the mist into the plasma generation space together with a mist transfer gas, and control the high-frequency power applied to the plasma generation means to control the atmospheric pressure inductively coupled plasma. A thin film containing at least a part of the components of the reaction material is formed on an object to be processed while controlling an oxidizing atmosphere or a reducing atmosphere therein.

  In the thin film forming method, plasma gas is introduced into the plasma generation space, atmospheric pressure inductively coupled plasma is generated by the plasma generation means, mist of the solution containing the reaction material is generated by the mist generation means, and the mist is It is preferable to introduce into the plasma generation space together with the mist transfer gas and form a thin film containing at least a part of the reaction material on the object to be processed. It is preferable to generate mist having a particle size of 50 μm or less, preferably 20 μm or less by the mist generating means.

  Further, water may be used as the solvent of the solution to supply an oxidizing atmosphere containing OH or O and / or a reducing atmosphere containing H in the atmospheric pressure inductively coupled plasma. A reducing atmosphere may be supplied into the atmospheric pressure inductively coupled plasma using formic acid or aldehydes as a solvent of the solution. The reaction material is a metal-containing compound and can form a thin film containing a metal.

  Furthermore, it is preferable to form a metal oxide thin film having a desired oxidation valence by controlling high-frequency power applied to the plasma generating means. The flow rate of the mist transfer gas is preferably set in a range of 3/28 or less of the flow rate of the plasma gas. It is preferable that a reactive gas is introduced into the plasma generation space and an oxidizing atmosphere or a reducing atmosphere is supplied in the atmospheric pressure inductively coupled plasma by the reactive gas. The reactive gas may be hydrogen gas or monoxide gas, and a reducing atmosphere may be supplied to the atmospheric pressure inductively coupled plasma. When generating the atmospheric pressure inductively coupled plasma, it is preferable to supply the plasma for ignition generated by the electrodeless discharge means to the plasma generation chamber. After the atmospheric pressure inductively coupled plasma is generated, the supply of the ignition plasma may be stopped.

  A thin film forming apparatus using atmospheric pressure inductively coupled plasma of the present invention generates a mist of a solution containing a plasma generation chamber having at least one gas inlet and a plasma outlet, and a reactive material for forming the thin film. Mist transfer for supplying mist generation means, plasma gas supply means for supplying plasma gas to the plasma generation chamber, and mist transfer gas for transferring mist generated by the mist generation means to the plasma generation chamber A gas supply means; and a plasma generation means for generating an atmospheric pressure inductively coupled plasma by applying energy to the plasma gas introduced into the plasma generation chamber. At least the reaction material contained in the mist supplied to the plasma generation chamber by a transfer gas. And forming a thin film containing some of the components.

  In the thin film forming apparatus, the mist generating means is configured by a combination of an air fog atomizer, an ultrasonic atomizer or a nebulizer, and a classification tank, and generates a mist having a particle size of 50 μm or less, preferably 20 μm or less. Is preferred. The apparatus further comprises a reactive gas supply means for supplying a reactive gas to the plasma generation space, and generates an oxidizing atmosphere or a reducing atmosphere in the atmospheric pressure inductively coupled plasma with the reactive gas, It is preferable to react some components with at least some components of the reactive gas. You may further provide the electrodeless discharge means for producing | generating the plasma for ignition.

  According to the present invention, since a mist of a solution capable of containing various reaction materials can be used as a raw material instead of a raw material gas having a limited variety, various kinds of desired compositions having a desired composition can be used. A thin film can be formed easily and at high speed. Further, by using inductively coupled plasma under atmospheric pressure, it is possible to realize a plasma processing apparatus for forming a thin film having a simple structure at low cost. Further, by appropriately selecting a solution solvent, a desired redox atmosphere can be supplied to the atmospheric pressure inductively coupled plasma, and the film quality of the thin film can be affected. Furthermore, by adding a reactive gas as required, a desired oxidation-reduction atmosphere can be supplied to the atmospheric pressure inductively coupled plasma, and the film quality of the thin film can be further controlled. Other effects will be described in the mode for carrying out the invention.

Schematic configuration diagram of an atmospheric pressure inductively coupled plasma processing apparatus of the present invention Schematic configuration diagram of mist generation means Schematic illustration of how to introduce mist into the plasma generation chamber Example of atmospheric pressure inductively coupled plasma processing apparatus Measurement results of plasma density of atmospheric pressure inductively coupled plasma Measurement results of electron density of atmospheric pressure inductively coupled plasma Measurement results of excitation temperature of atmospheric pressure inductively coupled plasma Result of selection experiment of mist generation means Mist particle size distribution chart Figure showing the relationship between mist supply conditions and plasma conditions and plasma stability The figure which shows the relationship between the electric power in the plasma which introduce | transduced water, and intensity | strength of OH, O (I), and H (alpha) emission spectrum. Emission spectrum when hydrogen is introduced as a reaction gas The figure which shows the relationship between the electric power and OH, O (I), and H (alpha) emission spectrum in the plasma which introduce | transduced the formic acid aqueous solution. The figure which shows the relationship between the electric power and the CO and CO ⁺ emission spectrum in the plasma which introduced the formic acid aqueous solution Experimental conditions for nickel thin film formation. Analysis results of nickel thin film by X-ray photoelectron spectroscopy Photomicrograph of nickel thin film Results of X-ray photoelectron spectroscopy analysis of silicon oxide films deposited using TEOS

  In the present invention, unlike a conventional CVD technique in which a raw material containing a target thin film component is supplied in a gas state, a solution containing a reactive material containing at least a part of the target thin film component (hereinafter, (Also referred to as “reactive material-containing solution”), the resulting solution is atomized into fine droplets, the fine droplets (mist) are supplied to atmospheric pressure inductively coupled plasma, A thin film having a desired composition is formed by a gas phase reaction.

  Inductively coupled plasma generates a high-temperature plasma by winding a coil around the plasma generation space and applying a high-frequency and high-frequency fluctuating magnetic field to the plasma generation space by flowing a high-frequency large current through the coil. Technology. In this specification, the “plasma generation space” includes a space in a chamber of a plasma generating apparatus capable of generating atmospheric pressure inductively coupled plasma and a space from the open end of the chamber to an object to be processed (see FIG. 1). ). Since inductively coupled plasma has high energy, it has been conventionally used for analysis in which an analysis sample is heated and atomized or thermally excited. However, inductively coupled plasma, especially atmospheric pressure inductively coupled plasma, is more difficult to generate plasma and maintain stable plasma than plasma under vacuum. Each condition was limited. Therefore, conventionally, the atmospheric pressure inductively coupled plasma has been used for the purpose of analyzing by adding a small amount of analysis sample that does not affect the plasma.

However, the present inventors supply a relatively large amount of the reaction material-containing solution necessary for forming a thin film by atomizing the reaction material-containing solution into fine droplets and supplying it to the plasma. It was confirmed that plasma can be maintained, and as a result, it was found that a thin film can be formed on the object to be processed, and the present invention has been achieved. Atmospheric pressure inductively coupled plasma has high density (electron density: 10 ²² m ⁻³ ) and high temperature (electron temperature: 8500 K or higher, excitation temperature: 10000 K or higher) (see FIGS. 5 to 7), and has high reactivity. Therefore, it is advantageous for forming a thin film. Furthermore, the plasma treatment under atmospheric pressure does not need to be depressurized as compared with the low-pressure plasma treatment, so that it is easy to handle and can be operated continuously. For this reason, there is an advantage that the processing amount can be increased.

  Conventionally, since the reaction material is supplied only by gas, a material that cannot be vaporized cannot be used, the choice of materials is limited, and a toxic material has to be used. In contrast, in the present invention, since at least a part of the reaction material can be supplied in a liquid state, the reaction material can be dissolved in a solution as various compounds to form a thin film having a desired desired composition. It is.

  In the present invention, atmospheric pressure inductively coupled plasma is used. Atmospheric pressure inductively coupled plasma generates plasma by supplying a plasma gas to a plasma generation space at atmospheric pressure and flowing a high-frequency large current through a coil wound around the plasma generation space. In the plasma generation space, air may be substituted with high-purity nitrogen or the like in advance. The plasma gas supplied to the plasma generation space may be any gas that is ionized by application of energy, such as helium (He) gas, argon (Ar) gas, xenon (Xe) gas, or neon (Ne) gas. A rare gas, hydrogen gas, oxygen gas, nitrogen gas, carbon dioxide gas, air, or a mixed gas thereof can be used. In particular, it is preferable to use a rare gas as the plasma gas and supply other gases as the mist transfer gas or the reactive gas after the plasma is generated from the stability of the plasma.

  In the thin film formation method of the present invention, in addition to a thin film containing a single metal element, a thin film containing a plurality of metal elements and an organic or inorganic thin film other than a metal may be formed. Table 1 to be described later exemplifies a thin film containing a single metal element, and Table 2 to be described later exemplifies a thin film containing a plurality of metal elements. Note that the thin film containing a single metal element and the thin film containing a plurality of metal elements may contain components other than metals as impurities or additives. The organic film includes organic polymer compounds such as polyethylene, polypropylene, cellulose oxide, and polysulfone, and the inorganic material includes silicon oxide and silicon nitride.

The reaction material is metal, metal-containing compound (for example, metal oxide, metal chloride, metal hydroxide, metal sulfide, metal carbonate), other than metal, depending on the desired desired thin film and solution solvent It can be appropriately selected from organic materials and inorganic materials. The reaction materials related to the metal-containing compound are exemplified in Tables 1 and 2 described later. Moreover, as a reaction material for forming an inorganic thin film, for example, TEOS (Tetraethyl orthosilicate) or the like can be used. The reaction material is an element or compound having at least one of the components of the thin film, and needs to be dissolved in the solvent of the reaction material-containing solution. For example, when forming a nickel film, nickel chloride (II) (NiCl ₂ ) and nickel nitrate (Ni (NO ₃ ) ₂ ) are soluble in water, and thus can be used for a reaction material-containing solution using water as a solvent. However, nickel (II) (NiO) is almost insoluble in water, and cannot be used as a reaction material for a reaction material-containing solution using water as a solvent. However, since nickel (II) oxide is dissolved in an acid, a reaction material-containing solution using an acid as a solvent can be used as a reaction material.

  When preparing the reaction material-containing solution, a nonpolar solvent, a polar aprotic solvent, or a polar protic solvent can be appropriately used as a solvent for dissolving the reaction material. Examples of nonpolar solvents include chloroform, diethyl ether, toluene, hexane, benzene, methylene chloride, and ethyl acetate, and polar aprotic solvents include tetrahydrofuran, dimethyl sulfoxide, acetone, acetonitrile, N, N-dimethylformamide, and the like. Examples of polar protic solvents include water, formic acid, acetic acid, ethanol, 2-propanol, 1-propanol, and 1-butanol. Moreover, you may use it, mixing a some solvent as a solvent. An aqueous solution containing an aldehyde containing an aldehyde group (—CHO), for example, acetaldehyde, formaldehyde or the like can also be used as the reducing solvent.

  When an organic solvent such as ethanol is employed, it is preferable to supply oxygen gas as a reactive gas to the plasma generation space and control the atmospheric pressure inductively coupled plasma to an oxidizing atmosphere. In this case, it is possible to prevent the carbon contained in ethanol from being precipitated in the plasma generation space due to the oxidizing action, so that the possibility of the plasma disappearing due to the influence of carbon is reduced, and the plasma can be stably maintained. The supply amount of oxygen gas is preferably about 0.5 to 1 L / min.

  The concentration of the reaction material in the reaction material-containing solution is preferably as high as possible, and more preferably close to saturation. In this way, the deposition rate of the thin film is increased, so that the processing efficiency can be improved.

  The reaction material-containing solution is atomized by the mist generating means to generate mist. The mist generating means can be constituted by, for example, a liquid sprayer (nebulizer, atomizer, ultrasonic sprayer, etc.) and a classification tank (Scott chamber, cyclone chamber, etc.) (see FIG. 2 as an example). The mist generating means is preferably configured to be able to generate the reaction material-containing solution as a mist having a predetermined particle size or less (50 μm or less, preferably 20 μm or less) so that the atmospheric pressure inductively coupled plasma does not become unstable. The generated mist is introduced into the plasma generation space together with the mist transfer gas. The components of the reactive material in the mist form a thin film having a desired composition by a gas phase reaction in atmospheric pressure inductively coupled plasma.

  The mist transfer gas is a gas having a function of transferring the mist to the plasma generation space. In the plasma generation space, the mist transfer gas may be ionized to generate plasma, and further, a part of the components of the ionized mist transfer gas may be generated. You may react with the reaction material. For example, rare gas such as helium (He) gas, argon (Ar) gas, xenon (Xe) gas or neon (Ne) gas, hydrogen gas, oxygen gas, nitrogen gas, carbon dioxide gas, air, or a mixed gas thereof Can be used.

  In addition, the component that was the solvent of the mist is, in atmospheric pressure inductively coupled plasma, a hydroxyl radical (OH), an oxygen radical (O) or the like that acts as an oxidizing agent, or a hydrogen radical (H) that acts as a reducing agent, CO Since it is ionized by radicals or the like, the oxidation-reduction atmosphere of atmospheric pressure inductively coupled plasma can be controlled by selecting a mist solvent.

Further, a reactive gas for adjusting the oxidation-reduction atmosphere in the plasma atmosphere or for forming a thin film may be introduced into the plasma generation space. By supplying the reactive gas, the oxidation-reduction atmosphere in the plasma atmosphere can be adjusted without changing the components of the mist. The reactive gas is one that generates radicals acting as an oxidizing agent or a reducing agent by plasma. For example, chlorofluorocarbon, hydrofluorocarbon, perfluorocarbon, carbon halide such as CF ₄ or C ₂ F ₆ , SiH _{4, and the like.} Gas for semiconductors such as B ₂ H ₆ or PH ₃ , clean air, dry air, oxygen, nitrogen, hydrogen, water vapor, carbon monoxide, carbon dioxide, formaldehyde gas, sulfur dioxide, hydrogen sulfide, halogen, ozone, SF ₆ A gas composed of one kind of the above or a mixed gas composed of a plurality of kinds of them can be used. The reactive gas may provide at least one of the components of the thin film and form the thin film together with the mist of the reaction material-containing solution. For example, when nitrogen gas is employed as the reactive gas, nitrogen does not contribute to the formation of an oxidation-reduction atmosphere, but the component in the mist and the nitrogen in the reactive gas can be combined to form a nitride film (for example, , Metal nitride film, silicon nitride film, etc.). In addition, if a reactive gas containing carbon, silicon or the like is used, a film containing a component such as carbon or silicon (for example, a metal carbide film, a metal silicide film, etc.) due to a gas phase reaction in plasma. ) Etc. can also be formed.

  The same type of gas may be used as the plasma gas and the mist transfer gas, or different types of gas may be used. For at least one of the plasma gas and the mist transfer gas, a reactive gas may be used instead of or in addition to the rare gas. When the reactive gas is added, the atmosphere of the atmospheric pressure inductively coupled plasma can be controlled by the oxidation-reduction action by the components of the reactive gas. That is, in the present invention, the oxidation-reduction atmosphere of the atmospheric pressure induction plasma can be controlled by the solvent component of the reaction material-containing solution, and the oxidation-reduction can also be performed by the reactive gas added in addition to the solvent component. The atmosphere can be controlled.

  In the oxidation-reduction atmosphere of atmospheric pressure induction plasma, the present invention reacts at least a part of the reaction material with at least a part of the solvent in a gas phase, or at least a part of the reaction material In addition to at least a part of the components of the solvent, a reactive gas component may be reacted in a gas phase to form a thin film containing at least a part of the reactive material on the object to be processed. it can.

  Embodiments of the present invention will be described below with reference to the drawings. However, the present invention is not limited to the following examples.

[Thin film formation method]
Specifically, in the thin film formation method using the atmospheric pressure inductively coupled plasma of the present invention, first, a plasma gas is introduced into the plasma generation space to generate atmospheric pressure inductively coupled plasma. As the plasma gas, a rare gas may be used, or a reactive gas may be used instead of or in addition to the rare gas.

  The plasma generation space is not only a space where plasma is actually generated, but also a space in the chamber of a plasma generator capable of generating atmospheric pressure inductively coupled plasma and a region including the space from the open end of the chamber to the object to be processed. (See FIG. 1). The object to be processed is not particularly limited, and is, for example, a semiconductor, glass, quartz, metal, ceramic or resin substrate, film, or the like.

  Next, the reaction material-containing solution prepared in advance is atomized by the mist generating means to generate mist, and the generated mist is introduced into the plasma generation space together with the mist transfer gas. The mist generating means is preferably configured to be capable of generating mist having a predetermined particle size or less (50 μm or less, preferably 20 μm or less) so that the atmospheric pressure inductively coupled plasma does not become unstable. For example, the mist generating means is preferably constituted by a nebulizer and a classification tank (see FIG. 2).

  The mist transfer gas is a gas for transferring the mist of the reaction material-containing solution or diluting the mist. When introduced into the plasma generation space, the mist transfer gas is ionized to generate plasma, so it is a carrier gas from the viewpoint of mist transfer and dilution, but from the point of generating plasma, Become.

  As the mist transfer gas, a rare gas that does not affect the reaction in the atmospheric pressure inductively coupled plasma may be used, or instead of the rare gas, it contributes to the gas phase reaction in the atmospheric pressure inductively coupled plasma. A reactive gas may be used. Further, a mixed gas of a rare gas and a reactive gas may be used as the mist transfer gas.

  When the same kind of gas as the plasma gas is used as the mist transfer gas, the mist transfer gas may be supplied through the same supply path as the plasma gas or may be supplied through a separate supply path. Even when a gas different from the plasma gas is used as the mist transfer gas, the mist transfer gas may be supplied through the same supply path as the plasma gas or may be supplied through a separate supply path. In this case, first, only the plasma gas is supplied to generate plasma, and after the plasma is stabilized, the mist transfer gas may be supplied. If a reactive gas is used as the mist transfer gas, the mist transfer gas, like the solution solvent, generates various radicals that act as an oxidant or a reducing agent in the atmospheric pressure inductively coupled plasma. The atmosphere of the atmospheric pressure inductively coupled plasma can be controlled.

  Next, at least a part of the reaction material and at least a part of the solvent of the solution are reacted in the atmospheric pressure inductively coupled plasma. When a reactive gas is used as the mist transfer gas, at least a part of the reaction material can be reacted with at least a part of the mist transfer gas in the atmospheric pressure inductively coupled plasma. Then, a thin film containing at least a part of the components of the reaction material is formed on the object to be processed that is in contact with the plasma generation space. Table 1 shows an example of a combination of a target thin film containing one type of metal element and a reaction material for forming the thin film. Table 1 shows, from the left, the names of metal elements, the composition of the thin film, the application examples of the thin film, and examples of the reaction materials that can be used when the solvent is water.

Table 2 shows an example of a combination of a target thin film containing two or more kinds of metal elements and a reaction material for forming the thin film. Table 2 shows, from the left, the name of the metal element, the name or composition of the thin film, the application example of the thin film, and examples of reactive materials that can be used when the solvent is water.

  As described above, according to the present invention, it is possible to use a mist of a solution containing various reactive materials, and various thin films having a desired composition can be easily and rapidly formed. Can do. According to the present invention, the type of the object to be processed is not particularly limited, and a thin film having a desired composition is formed not only on a metal substrate but also on, for example, a glass substrate, a resin substrate, and various film-like substrates. Can do. Moreover, the oxidation-reduction atmosphere of the atmospheric pressure inductively coupled plasma can be controlled by appropriately selecting the solvent of the reaction material-containing solution and the reactive gas. The reaction material can also be selected as appropriate, and the thin film that can be formed is not limited to one containing one type of metal element, but can also contain a plurality of types of metal elements. By appropriately selecting a reaction material, a solvent, and a reactive gas, not only a metal-containing thin film but also a thin film containing a nonmetal, an organic substance, or an inorganic substance can be formed.

[Schematic configuration of plasma processing equipment]
FIG. 1 is a schematic configuration diagram of a plasma processing apparatus (thin film forming apparatus) 1 for carrying out a thin film forming method using atmospheric pressure inductively coupled plasma of the present invention. The plasma processing apparatus 1 includes at least a mist generation unit 2, a plasma generation chamber 4, and a plasma generation unit 5, and is connected to a gas supply source 3 and a liquid tank 6.

  The gas supply source 3 supplies at least a plasma gas 31 and a mist transfer gas 32. In FIG. 1, the plasma gas 31 is supplied to the plasma generation chamber 4 through a supply path different from the mist transfer gas 32, but the plasma gas 31 can also be used as the mist transfer gas 32. As the plasma gas 31 and the mist transfer gas 32, the same type of gas may be used, or different types of gases may be used. For example, a rare gas may be used for the plasma gas 31 and a reactive gas may be used for the mist transfer gas 32.

  Further, the gas supply source may supply the cooling gas 33 as necessary. The cooling gas 33 is a gas for cooling the periphery of the plasma generation chamber 4, and nitrogen gas is preferably used. Although a cooling liquid can be used instead of the cooling gas 33, when using as the mist transfer gas 32, the cooling gas 33 is used instead of the cooling liquid. Also, a reactive gas or a reaction solution can be used as the cooling medium. The reaction solution reacts when irradiated with plasma and reacts with the formed thin film. For example, the reaction solution includes chloroform, diethyl ether, toluene, hexane, benzene, methylene chloride, ethyl acetate, tetrahydrofuran, dimethyl sulfoxide, acetone, acetonitrile, N, N-dimethylformamide, water, formic acid, acetic acid, ethanol, 2- Propanol, 1-propanol, 1-butanol, alkali, hydrogen peroxide solution, ozone water, hydrogen water and the like can be used. As an example of using a reaction solution, acid, hydrogen peroxide solution, ozone water or the like is supplied as a reaction solution to the surface of the formed thin film to oxidize the surface, or hydrogen water is supplied as a reaction solution. Thus, the surface can be terminated with hydrogen.

  The liquid tank 6 is a tank for storing a solution 63 obtained by dissolving a reaction material 61 for forming a target thin film in a solvent 62. The reaction material-containing solution 63 is supplied to the mist generating means 2.

  FIG. 2 is a schematic configuration diagram of the mist generating means 2. Although the mist production | generation means 2 is not specifically limited, For example, it can be comprised with the liquid sprayer (nebulizer) 22 and the classification tank (Scott chamber) 24. FIG. When the reaction material-containing solution 63 supplied from the liquid tank 6 is introduced into the liquid sprayer 22, it receives the pressure of the mist transfer gas 32 introduced from the other inlet and enters the classification tank 24 as mist from the injection port. Be injected. In the classification tank 24, the mist is separated according to the particle size, mist 64 having a predetermined particle size or less is supplied to the plasma generation chamber 4, and mist 65 having a larger particle size is discharged. The predetermined particle size is preferably 50 μm or less, and more preferably 20 μm or less.

  Referring again to FIG. 1, the plasma generation means 5 (51, 52, 53) applies electromagnetic field energy to the plasma gas 31 introduced into the plasma generation chamber 4, and generates plasma including the internal space of the plasma generation chamber 4. An atmospheric pressure inductively coupled plasma 10 is generated in the space 40. Specifically, the plasma generation means 5 includes a high-frequency coil 51 that supplies energy to the plasma gas 31, a matching box 52 that adjusts power to the high-frequency coil 51, a power supply 53 that supplies high-frequency power to the high-frequency coil 51, and a cooling unit. (Not shown).

  The plasma generation chamber 4 has a cylindrical shape, particularly preferably a cylindrical shape, and includes a plasma gas inlet 41, a mist inlet 42 and a plasma outlet 43. The workpiece 8 is disposed at a predetermined distance from the plasma outlet 43. Although the predetermined distance depends on the configuration of the apparatus, it can be set to about 5 to 30 mm, for example. The plasma gas 31 is introduced into the plasma gas inlet 41 and flows into the plasma generation chamber 4 as a swirling flow that advances spirally along the inner wall of the cylindrical plasma generation chamber 4 in order to stably maintain the plasma. Is preferred. By using such a swirl flow, the plasma gas 31 is not directly introduced into the plasma generated near the center of the plasma generation chamber 4, but is supplied from the periphery of the plasma. It can be kept stable. The plasma gas 31 is ionized by the energy added by the plasma generating means 5 to generate the plasma 10. It is preferable that the mist 64 is introduced into the mist inlet 42 together with the mist transfer gas 32 and flows into the plasma generation chamber 4 by a linear flow. When the mist 64 and the mist transfer gas 32 come into contact with the plasma 10, they are ionized and become part of the plasma 10.

The plasma generation chamber 4 contains a part of the plasma generation space 40. The plasma generation space 40 includes a space from the plasma outlet 43 of the plasma generation chamber 4 to the workpiece 8. The plasma generation chamber 4 is not particularly limited as long as the atmospheric pressure inductively coupled plasma can be maintained in the plasma generation space. For example, a plasma torch can be used. The plasma generation chamber 4 includes the plasma generation chamber 4. It is preferable to provide a cooling means for cooling. As the cooling means, for example, the cooling gas 33 is introduced through the cooling gas inlet 46 connected to the gap between the outer shell 44 and the inner shell 45 of the plasma generation chamber 4, and the cooling gas 33 is supplied to the cooling gas injection port. It is good also as a structure injected from 47. The cooling gas 33 introduced from the cooling gas introduction port 46 cools the plasma generation chamber 4 and is further injected from the cooling gas injection port 47 so as to cover the periphery of the plasma 10. The cooling gas 33 covering the surroundings makes it difficult for outside air or the like to be mixed into the plasma, so that the plasma is stably maintained and impurities due to the influence of outside air are prevented from being mixed into the thin film. Further, a pipe for flowing a cooling medium (gas or liquid) around the plasma generating chamber 4 may be provided, or the coil 51 of the plasma generating means 5 is formed of a hollow conductive material, and the cooling medium (gas) is formed in the coil. Alternatively, the liquid may be flowed.

  By the way, it is generally difficult to generate plasma at atmospheric pressure as compared with a vacuum state. In order to generate inductively coupled plasma at atmospheric pressure, ignition means such as a high melting point conductor is provided in the plasma generation space. It is necessary. However, if a high melting point conducting wire or the like is provided in the plasma generation space, these components are inevitably mixed into the plasma as impurities, making it difficult to accurately form a thin film having a desired composition. Therefore, in the present embodiment, an appropriate electrodeless discharge means (for example, a plasma generator using a dielectric barrier discharge, not shown) capable of generating low temperature plasma is provided outside (upstream side) of the plasma generation chamber. It is preferable that plasma is introduced into the plasma generation chamber as an ignition means and is brought into contact with the plasma gas to generate atmospheric pressure inductively coupled plasma. Thus, it is preferable to use a structure that does not include a high-melting-point conductor or the like in the plasma generation space because the possibility of impurities being mixed is reduced. After the atmospheric pressure inductively coupled plasma is stably maintained, the introduction of the low temperature plasma may be stopped.

  Although FIG. 1 illustrates an example in which the mist 64 is introduced into the plasma generation chamber 4 from the mist introduction port 42 together with the mist transfer gas 32, the present invention is not limited to this. The mist 64 can be supplied together with the plasma gas 31 to the plasma generation space via the plasma gas introduction port 41, or can be introduced together with the cooling gas 33 and supplied to the plasma generation space via the cooling gas injection port 47. it can.

  FIG. 3 is an example of mist introduction into the plasma generation chamber. FIG. 3A shows an example in which the mist 64 is supplied to the plasma generation space 40 from the mist inlet 42 together with the mist transfer gas 32. The plasma gas 41 is supplied from the plasma gas inlet 41 to the plasma generation space 40 and generates atmospheric pressure inductively coupled plasma 10. The cooling gas 33 is supplied from the cooling gas introduction port 46 to the periphery of the plasma generation space 40 and is injected from the cooling gas injection port 47 to block outside air. Alternatively, a cooling liquid may be supplied from the cooling gas inlet 46 instead of the cooling gas, and the plasma generation space 40 may be blocked from the outside air by a curtain made of the cooling liquid. Under the present circumstances, the characteristic of a thin film can also be changed by using a reaction solution as a cooling liquid.

  FIG. 3B shows an example in which the mist 64 is supplied to the plasma generation space 40 from the plasma gas inlet 41 together with the plasma gas 31. In this case, the mist inlet 41 is not used, and the plasma gas 31 also functions as the mist transfer gas 32. The supply example in FIG. 3 (B) is not different from the supply example in FIG. 3 (A) in terms of thin film formation, but the introduction port from which the mist is supplied depends on the purpose and the configuration of the apparatus. And may be selected as appropriate.

  FIG. 3C shows an example in which the mist 64 is supplied from the cooling gas inlet 46 together with the cooling gas 33 to the periphery of the plasma generation space 40. In this case, the cooling gas 33 also functions as the mist transfer gas 32. The mist 64 is injected from the cooling gas injection port 47 and contacts the atmospheric pressure inductively coupled plasma 10 in the vicinity of the plasma outlet 43. Even in the case of FIG. 3C, a thin film can be formed on the workpiece 8 by the so-called Saya effect. In the case of the supply example in FIG. 3C, the reactivity in the gas phase is poorer than in the case of FIGS. 3A and 3B in which mist is directly introduced into the plasma, but a mild reaction is required. It is preferable in some cases.

  As described above, according to the plasma processing apparatus 1 of the present embodiment, at least a part of the reaction material 61 and at least a part of the solution solvent 62 in the plasma generation chamber 4 (plasma generation space 40). By reacting, the thin film 20 including at least a part of the components of the reaction material 61 can be formed on the workpiece 8 adjacent to the plasma outlet 43. Furthermore, if reactive gas is added, at least a part of the reactive material and a part of the reactive gas are reacted with each other, so that the reaction material 61 is brought close to the workpiece 8 close to the plasma outlet 43. The thin film 20 including a part of the reactive gas in addition to at least a part of the component can be formed.

  As described above, in the embodiments of the present invention, since inductively coupled plasma is used under atmospheric pressure, it is possible to provide a plasma processing apparatus for forming a thin film having a simple configuration at low cost. By making the particle size of the mist of the reaction material-containing solution relatively small, the atmospheric pressure inductively coupled plasma in contact with the mist can be stably maintained.

[Example]
Hereinafter, various examples of the thin film forming method of the present invention will be described.
FIG. 4 is a schematic configuration diagram of an embodiment of the plasma processing apparatus. The plasma processing apparatus 1 of this example is an atmospheric pressure flow type reaction apparatus including an atmospheric pressure inductively coupled plasma generation chamber 4 and plasma generation means 5 (51, 53), and includes a mist generation means 2, a gas supply source (not shown). ). The atmospheric pressure inductively coupled plasma generation chamber 4 is constituted by a cylindrical quartz torch. The high frequency power supply 53 can apply high frequency power of 40.68 MHz to the induction coil 51 provided on the outer periphery of the quartz torch.

  Argon gas was used as the plasma gas 31 </ b> A and introduced into the plasma gas inlet 41 of the plasma generation chamber 4. Hydrogen gas was used as the reactive gas 31B as necessary, and was introduced into the plasma gas inlet 41. Argon gas was used as the mist transfer gas 32 and introduced into the mist inlet 42 together with the mist 64. Further, a plasma generator by dielectric barrier discharge is provided as an electrodeless discharge means that is an ignition means upstream of the mist inlet 42, and low temperature plasma is supplied to the plasma generation space at atmospheric pressure to ignite the plasma. It is possible to make it. Nitrogen gas was used as the cooling gas 33 and introduced into the cooling gas inlet 46. Moreover, the emission spectrum of the atmospheric pressure inductively coupled plasma injected from the plasma outlet 43 was measured by the analyzing means 9 (Hamamatsu Photonics multi-channel photo analyzer, type PMA-11 (C7473-36)).

  First, in the apparatus shown in FIG. 4, the state of plasma when mist was not supplied was analyzed. In this embodiment, the supply amount of the argon gas 31A is 14 L / min, the supply amount of the hydrogen gas 31B is 0.42 L / min, the supply power (40.68 MHz) is 1000 or 1500 W, and the upstream of the mist inlet 42. An argon / hydrogen atmospheric pressure inductively coupled plasma was generated by supplying a plasma jet using argon from a plasma generating device with dielectric barrier discharge provided on the side into the plasma torch. Note that the plasma jet using argon is merely an example, and a plasma jet using another plasma gas such as helium may be employed.

5 and 6 are measured values of plasma density and electron temperature in plasma generated in the plasma torch, respectively. As shown in FIGS. 5 and 6, an electron density of 2.02 × 10 ²² / m ³ at an electric power supply of 1000 W, an electron temperature of 8868 K, an electron density of 1.82 × 10 ²² / m ³ at an electric power of 1500 W, and an electron temperature of 10032 K are high. A high density and high temperature plasma could be obtained. FIG. 7 shows measured values of the excitation temperature of argon plasma when only argon gas 31A is supplied at 14 L / min and plasma is generated at a supply power of 400 to 1000 W. As shown in FIG. 7, the excitation temperature of the argon plasma was 10000 K or higher at any supply power. Next, a method for stably supplying mist to plasma was studied.

[Selection experiment of mist generation means]
First, an experiment was conducted on an optimum mist generating means. Air fog atomizer, ultrasonic atomizer, saturated steam generator, nebulizer, and combination of nebulizer and classification tank are used as mist generating means. Using an organic substance-containing solution and a metal salt-containing aqueous solution, the possibility of mist generation was examined. FIG. 8 shows the result of the selection experiment of the mist generating means, and is a diagram showing whether mist generation is possible for each mist generating means. Evaluation with a circle in the figure indicates that the mist has been generated, and evaluation with a triangle in the figure indicates that the mist has been generated conditionally.

  As shown in FIG. 8, when any means is used as the mist generating means, mist can be generated with only water. When using an air fog atomizer, spraying a metal salt aqueous solution can temporarily generate mist, but if it is used for a certain period of time, the nozzle may clog and cannot be used continuously. It was. Further, when an ultrasonic atomizer was used, when a viscous organic substance-containing solution and a metal salt aqueous solution were sprayed, sufficient mist was not generated, and the mist supply amount was unstable. The saturated water vapor generator generates only the solvent (water) vapor, and cannot generate the vapor containing the reaction material.

  Furthermore, an experiment was conducted in which mist generated using each of the mist generating means was supplied to atmospheric pressure inductively coupled plasma. The atmospheric pressure inductively coupled plasma is generated with an argon gas 31A supply rate of 14 L / min and a supply power (frequency of 40.68 MHz) of 1000 W. The atmospheric pressure inductively coupled plasma is generated by each mist generating means. The supplied mist is supplied with 1 L / min mist transfer gas (argon gas), and a solution (water, non-viscous organic substance-containing solution, viscous organic substance-containing solution, or metal salt-containing aqueous solution) is 3.15 mL / min. (Same as condition 7 in FIG. 10).

  As a result, when the water mist of the saturated steam generator and the mist of each solution of the nebulizer alone were used, the plasma disappeared when the mist was supplied to the plasma because the mist particle size was large (˜100 μm). The plasma was stable when using air fog atomizer water, non-viscous organic-containing solution or viscous organic-containing solution. In addition, when an ultrasonic atomizer was used, the plasma was stable if it was limited to water or a non-viscous organic substance-containing solution. When a combination of a nebulizer and a classification tank was used, the plasma could be stably maintained with any solution.

  FIG. 8 shows the mist particle size by each mist generating means. When a mist of 50 to 100 μm is supplied for the mist particle size (saturated steam generator and nebulizer alone), the plasma becomes unstable. It became clear that it could not be maintained. Therefore, the mist particle size is preferably 50 μm or less, and more preferably 20 μm or less. From the above experimental results, it was found that it is optimal to use a combination of a nebulizer and a classification tank as the mist generating means from the point of solution selectivity. However, water or an organic substance-containing solution that is not viscous may use an air fog atomizer or an ultrasonic atomizer as the mist generating means. If it is a viscous organic substance-containing solution, the mist generating means may be used. Air fog atomizer can be used. In addition, when using an air fog atomizer or an ultrasonic atomizer, it is good also as a structure which adds a classification tank and supplies the mist below a fixed particle size to plasma.

FIG. 9 is an example of the particle size distribution of mist when a combination of a nebulizer and a classification tank is used as the mist generating means. The mist transfer gas is argon gas (supply flow rate F _C per unit time is 1 L / min), and the supply flow rate F _MD of water per unit time is 3.15 mL / min. The horizontal axis of the graph of FIG. 9 is the measured mist particle size (d _MD [μm]), and the vertical axis is the mist number distribution (N _MD / ΣN _MD ). As shown in FIG. 9, in this example, a mist of approximately 20 μm or less could be generated, and the average particle diameter of the mist was 5.12 μm. Although the feed flow rate F _MD of water was varied in the range of 1~7mL / min, in this condition, the supply flow rate F _MD Water clear that no effect less against the mist particle diameter d _MD It became. In this example, the mist particle size was measured based on the immersion method. In the immersion method, a receiving liquid that does not dissolve the mist to be measured (silicon oil if the mist is water) is filled into a receiving pan, and mist particles are collected in the receiving dish, and the particle size is obtained by microscopic observation and photography. Is what you want.

[Water mist supply and plasma stability]
Next, the stability of plasma under various mist supply conditions and plasma conditions when a combination of a nebulizer and a classification tank was used as a mist generating means was examined.

  FIG. 10 is a diagram showing the relationship between the mist supply condition, the plasma condition, and the plasma stability. In any case of Conditions 1 to 20, the supply amount of plasma gas (argon) is 14.0 L / min. Under conditions 1 to 9, the supply amount of mist transfer gas (argon) is fixed at 1 L / min, the supply amount of water is fixed at 3.15 mL / min, and the supply power is appropriately changed as shown in the range of 400 to 1500 W. did. Under conditions 7 and 10-15, the supply amount of water was fixed at 3.15 mL / min and the supply power was fixed at 1000 W, and the supply amount of mist transfer gas (argon) was appropriately changed as illustrated. In conditions 7 and 16 to 22, the supply amount of mist transfer gas (argon) was fixed at 1 L / min, the supply power was 1000 W, and the supply amount of water was appropriately changed as shown. The particle size of the mist supplied to the plasma is 20 μm or less in any case.

From FIG. 10, when the power P _W is 400 W, when the mist is supplied to the plasma, the plasma is extinguished (evaluation of condition 1 “×”). When the power P _W was 500 W or more, the plasma was stable if the supply amount of the mist transfer gas was limited to a range of 1.5 L / min or less (evaluation of conditions 2 to 12 and conditions 16 to 22 “◯”). . In addition, when the supply amount of mist transfer gas is in a range of 2 L / min or more, the swirl flow of plasma gas is disturbed by the mist transfer gas, and lightning-like discharge (similar to arc discharge) is generated in the plasma generation space. Then, after a few minutes, the plasma disappeared (evaluation of conditions 13 to 15 “Δ”). The amount of water supply itself does not affect the stability of the plasma up to a range of at least 10 mL / min.

  As described above, when a water mist having a particle size of 20 μm or less is supplied using a combination of a nebulizer and a classification tank as mist generating means, the power is set to 500 W or more, and the supply amount of the mist transfer gas is set to ( It was revealed that the plasma can be stably maintained by setting it to 1.5 L / min or less (relative to the plasma gas supply rate of 14.0 L / min).

  As described above, in the example of the present invention, since the mist particle size is reduced to some extent, the atmospheric pressure inductively coupled plasma generated in the plasma generation chamber does not become unstable, and the flow rate of plasma gas (14 L / min) The mist and mist transfer gas could be supplied in a range up to about 1.5 L / min. For this reason, for example, the mist is supplied at a much larger flow rate (for example, 0.5 to 1.5 L / min) than in the case of supplying a very small amount (for example, about 100 μL) of the sample in the analysis method disclosed in Patent Document 2. Therefore, a sufficient amount of reaction material can be continuously supplied, and efficient thin film formation can be realized.

[Redox control by supplied power]
In the plasma processing apparatus 1 of FIG. 4, plasma 10 is generated using argon gas as the plasma gas 31 </ _b > A, argon gas is used as the mist transfer gas 32, and the mist 64 of water (H ₂ O) is added to the plasma generation chamber 4. Supplied. The plasma emission spectrum was measured by the analyzing means 9 while increasing the high frequency power P _W supplied to the induction coil 53 by 100 _W in the range of 500 to 1000 _W.

  FIG. 11 is an explanatory diagram showing the characteristics of the emission spectrum of a typical radical in such water mist plasma. Circles indicate the intensity of the emission spectrum of OH radical (OH.) At 310 nm, triangles indicate the intensity of the emission spectrum of oxygen atom (O) at 777 nm, and square marks indicate the hydrogen atom (Hα ray at 656 nm). ) Spectrum intensity.

In the power P _w is 500W, peak of the spectrum due to the OH · in the vicinity of 310nm is dominant. On the other hand, it was revealed that the intensity of the spectrum of OH · decreased as the power P _w increased, and the spectrum of Hα ray at 656 nm and O at 777 nm increased. That is, when water mist is supplied to the plasma, OH is mainly obtained at 500 W, and an oxidizing atmosphere is provided in the plasma. And when electric power is increased, OH * with low excitation energy is ionized into H and O with high excitation energy. For this reason, in the vicinity of 1000 W, OH · acting as an oxidizing agent decreases, while H acting as a reducing agent increases, so that a reducing atmosphere is provided in the plasma.

  Thus, even when the plasma gas 31 and the mist transfer gas 32 are rare gases such as argon and do not contain a reactive gas, the abundance ratio of various radicals in the plasma can be increased by increasing the high-frequency power to the plasma. Can be changed. That is, since the oxidation / reduction atmosphere in the plasma can be controlled by changing the abundance ratio of radicals based on the magnitude of the high frequency power, the degree of oxidation and reduction can be appropriately set. Thus, for example, if a metal oxide is used as the reaction material, a metal oxide thin film having a desired oxidation valence can be formed.

[Reduction control with hydrogen gas]
In the plasma processing apparatus 1 of FIG. 4, instead of introducing water mist, hydrogen gas was supplied as the reactive gas 31B together with the argon plasma gas 31A. The flow rate of argon gas is 14.0 L / min, and the flow rate of hydrogen gas is 0.42 L / min. The high frequency power is 40.68 MHz and 1000 W.

FIG. 12 is an explanatory diagram showing the characteristics of the emission spectrum of radicals by hydrogen gas (H ₂ ). According to FIG. 12, peaks of 656.28 nm Hα line and 485.13 nm Hβ line were observed. That is, it was found that the presence of hydrogen atoms H was confirmed in the plasma of argon gas and hydrogen gas, and it was possible to provide a reducing atmosphere for the plasma. In this example, hydrogen gas is used as a reactive gas exhibiting reducibility. However, carbon monoxide gas or carbon dioxide gas can be used to supply a reducing atmosphere of CO or CO ⁺ into the plasma. . Moreover, you may employ | adopt formaldehyde gas, sulfur dioxide, hydrogen sulfide etc. as a reducing reactive gas. Thus, according to the present invention, it is possible to control the oxidation-reduction atmosphere of plasma also by addition of a reactive gas.

[Redox control by formic acid mist]
In the plasma processing apparatus 1 of FIG. 4, argon gas was supplied as the plasma gas 31 </ _b > A, a formic acid aqueous solution (HCOOH / H ₂ O) was used as the solution solvent 62, and a formic acid mist 64 was supplied together with the argon gas of the mist transfer gas 32. The plasma emission spectrum was measured by the analysis means 9 while increasing the high frequency power P _W supplied to the induction coil 53 by a predetermined amount of power in the range of 400 to 1500 _W.

FIG. 13 and FIG. 14 are explanatory diagrams showing the characteristics of the emission spectrum of radicals by formic acid aqueous solution (HCOOH / H ₂ O). According to FIG. 13, when the power Pw is 400 to 600 _W , the peak of the spectrum due to OH · is dominant. Decreasing the intensity of the spectrum of the OH · (circles) with an increase in the power P _w is the spectrum of O (triangles) and Hα line (squares) that increases revealed. FIG. 14 reveals that the spectrum of CO (circle mark) at 483 nm and CO ⁺ (triangle mark) at 617.4 nm gradually increases when the power P _w is 600 W or more. In other words, when formic acid mist is supplied to the plasma, OH · acting as an oxidizing agent is predominant at 400 to 600 W, so that an oxidizing atmosphere is provided in the plasma, and at about 900 W or more, it acts as a reducing agent. As H, CO, and CO ⁺ dominated, a reducing atmosphere is provided in the plasma. In this example, formic acid is used as a reducing solvent, but aldehydes containing an aldehyde group (—CHO) such as acetaldehyde and formaldehyde can also be employed.

[Nickel thin film formation]
In FIG. 4, an experiment was conducted in which a thin film containing nickel (Ni), nickel oxide (NiO, Ni ₂ O ₃ ) or the like was formed using a solution mist 64 containing nickel chloride (NiCl ₂ ) as the reaction material 61. Such nickel thin film formation is suitable for pretreatment of electroless plating, manufacture of electrical devices, and the like. The experimental conditions (the flow rate of each gas, the adjusted concentration of the nickel chloride-containing solution, etc.) are as shown in FIG. As basic conditions, argon gas is used for the plasma gas and mist transfer gas, and nitrogen gas is used for the cooling gas. In conditions 1 to 5, the solvent of the nickel chloride-containing solution is water (H ₂ O), and in conditions 6 to 11, the solvent is an aqueous formic acid solution (HCOOH / H ₂ O). Under conditions 5, 10 and 11, hydrogen gas (H ₂ ) was added as a reactive gas together with argon plasma gas. In conditions 1 to 8 and 10, the supplied power is 1000 W, and in conditions 9 and 11, the supplied power is 600 W. At an electric power of 1000 W, hydrogen atoms (H) in water (H ₂ O) have a reducing action (see FIG. 11), and CO and CO ⁺ in formic acid aqueous solution (HCOOH / H ₂ O) also have a reducing action. Possible (see FIGS. 13 and 14). It is also considered that hydrogen atoms (H) in hydrogen gas (H ₂ ) have a reducing action.

Under any of the conditions shown in FIG. 15, a thin film of nickel (Ni) and nickel oxide (NiO, Ni ₂ O ₃ ) could be formed on the object to be processed. ) A thin film could be obtained predominantly. A silicon wafer, a bakelite plate, a glass epoxy substrate, or a polyimide film was used as an object to be processed.

FIGS. 16A and 16B are graphs showing analysis results by X-ray photoelectron spectroscopy (XPS) of the thin films formed under the conditions 3 and 5, respectively. Conditions 3 and 5 are the same conditions except that hydrogen gas is added in Condition 5. FIG. 16A shows a case where hydrogen gas (H ₂ ) is not added (condition 3), and FIG. 16B shows a case where hydrogen gas (H ₂ ) is added as a reactive gas (condition 5). ). Compared to FIG. 16A, in FIG. 16B, the peak of nickel (Ni) near 852.5 eV is relatively larger than the peak of nickel oxide (NiO, Ni ₂ O ₃ ). It is clear that a nickel (Ni) thin film was formed.

  FIGS. 17A and 17B are photographs obtained by microscopic observation of the thin films formed under the conditions 3 and 5, respectively. 17A and 17B, the thin film shown in FIG. 17B has larger particles and a larger amount of deposition.

From the results shown in FIGS. 16 and 17, when hydrogen gas (H ₂ ) is added as a reactive gas (condition 5), formation of a metal thin film is promoted more than when no reactive gas is added (condition 3). I found out that As shown in FIG. 15, since oxygen exists as water as a solvent in the reaction system, the metal film is easily oxidized, but hydrogen in hydrogen gas (H ₂ ) added as a reactive gas. It is considered that the atom (H) acts as a reducing agent, the nickel oxide is reduced, and more nickel metal is deposited.

[Formation of tungsten thin film]
Next, in FIG. 4, a mist 64 of an aqueous solution containing sodium tungstate (Na ₂ WO ₄ ) is used as the reaction material 61, and a thin film containing tungsten oxide (WO ₃ ), tungsten (W), or the like is processed (silicon Experiments were carried out on the wafer. Such thin film formation of tungsten oxide or the like is suitable for manufacturing optical films, transparent conductive films, photocatalysts, and the like. By adding oxygen (O ₂ ) as a reactive gas, oxygen radicals can act as an oxidizing agent to oxidize tungsten atoms ionized in the plasma and deposit tungsten oxide (WO ₃ ). A thin film could be formed on top. Further, when the power supplied to the plasma was increased, the oxidizing action of oxygen atoms (O) in the plasma became stronger, and the oxidation state of tungsten could be controlled. Furthermore, by microscopic observation, precipitates such as ratio _of tungsten oxide (WO ₃₎ was found to contain nanoparticles 50 to 100 nm.

[Formation of silicon oxide film by TEOS]
In FIG. 4, a thin film mainly composed of silicon oxide (SiO ₂ ) was formed on a polyimide film using a mist 64 of TEOS (Tetraethyl orthosilicate) as a reaction material 61. TEOS is an organic compound having the chemical formula Si (OC ₂ H ₅ ) ₄ , has a structure in which four ethyl groups are bonded to SiO ₄ ^4- ion (orthosilicate ion), and is a colorless and transparent liquid. Liquid TEOS was used as it was as the material-containing solution.

  FIG. 18 is a graph showing the analysis result by XPS of the silicon oxide film formed by TEOS. 18A shows the analysis result by XPS in the range (95 to 112 eV) in the vicinity of the binding energy (99 eV) of silicon (Si (2p)), and FIG. 18B shows oxygen (O (1s)). Is an analysis result by XPS in a range (525 to 540 eV) in the vicinity of the binding energy (531 eV). 18A and 18B, the lower curve shows the surface state of the silicon wafer before the plasma treatment, and the upper curve shows when the mist of the TEOS solution is supplied to the atmospheric pressure inductively coupled plasma by argon gas. The surface state of is shown.

In FIG. 18A, a Si (2p) peak was confirmed before the plasma treatment (lower curve). In FIGS. 18A and 18B, a peak of SiO ₂ (2p) is also observed, which is considered to be due to a natural oxide film. On the other hand, after the plasma treatment by the mist of the TEOS solution in FIG. 18A (upper curve), the Si (2p) peak disappeared and the SiO ₂ (2p) peak appeared stronger than before the plasma treatment. Further, in FIG. 18B, the peak of SiO ₂ (1s) appeared more strongly after plasma treatment with the TEOS solution mist (upper curve) than before plasma treatment (lower curve). As a result, it was confirmed that the mist of the TEOS solution was decomposed in the atmospheric pressure inductively coupled plasma, and SiO ₂ was deposited on the silicon wafer.

As described above, according to an example of the present invention, a mist having a particle size of 20 μm or less can be supplied by a nebulizer and a classification tank, and the plasma is stabilized even when the mist is brought into contact with atmospheric pressure inductively coupled plasma. Can be maintained. Moreover, if water is used as the solution solvent, the plasma can be controlled to an oxidizing atmosphere or a reducing atmosphere by changing the power supplied to the high-frequency coil. If formic acid mist is used as the solution solvent, the plasma can be controlled in a reducing atmosphere. In addition, an oxidizing atmosphere can be provided to the plasma by adding hydrogen gas as a reactive gas. In one example of the present invention, when water (H ₂ O) is used as the solution solvent, the plasma redox atmosphere can be controlled by appropriately setting the magnitude of the high-frequency power supplied to the plasma generating means. it can.

  If a nickel chloride solution is used, a thin film containing nickel or nickel oxide can be formed. If a sodium tungstate solution is used, a thin film containing tungsten oxide, tungsten, or the like can be formed. When a TEOS solution is used, a thin film such as silicon oxide can be formed.

  Although various embodiments have been described above, the scope of application of the present invention is not limited to each embodiment. A plurality of these embodiments can be combined, and the conditions used in each embodiment can be changed and replaced to form a thin film having a desired composition.

DESCRIPTION OF SYMBOLS 1 Plasma processing apparatus 2 Mist production | generation means 4 Plasma production | generation chamber 5 Plasma production | generation means 8 To-be-processed object 10 Atmospheric pressure inductively coupled plasma 31 Plasma gas 32 Mist transfer gas 33 Cooling gas 40 Plasma production space 61 Reactive material 62 Solvent 63 Reactive material containing solution 64 Mist

Claims (16)

Plasma gas is introduced into the plasma generation space, and atmospheric pressure inductively coupled plasma is generated by the plasma generation means.
A mist of the solution containing the reaction material is generated by the mist generating means,
Introducing the mist together with the mist transfer gas into the plasma generation space;
A thin film containing at least a part of the reaction material is formed on an object to be processed while controlling an oxidizing atmosphere or a reducing atmosphere in the atmospheric pressure inductively coupled plasma by controlling high-frequency power applied to the plasma generating means. A method for forming a thin film using atmospheric pressure inductively coupled plasma. Plasma gas is introduced into the plasma generation space, and atmospheric pressure inductively coupled plasma is generated by the plasma generation means.
A mist of the solution containing the reaction material is generated by the mist generating means,
Introducing the mist together with the mist transfer gas into the plasma generation space;
A thin film forming method using atmospheric pressure inductively coupled plasma, wherein a thin film containing at least a part of the reaction material is formed on an object to be processed.   The thin film forming method according to claim 1 or 2, wherein the mist generating means generates a mist having a particle size of 50 µm or less, preferably 20 µm or less.   4. The method according to claim 1, wherein water is used as a solvent of the solution to supply an oxidizing atmosphere containing OH or O and / or a reducing atmosphere containing H in the atmospheric pressure inductively coupled plasma. The thin film forming method according to item.   5. The thin film forming method according to claim 1, wherein a reducing atmosphere is supplied into the atmospheric pressure inductively coupled plasma using formic acid or an aldehyde as a solvent of the solution.   The thin film forming method according to claim 1, wherein the reaction material is a metal-containing compound, and a thin film containing a metal is formed.   7. The thin film forming method according to claim 6, wherein a high frequency power applied to the plasma generating means is controlled to form a metal oxide thin film having a desired oxidation valence.   8. The thin film forming method according to claim 1, wherein the flow rate of the mist transfer gas is set in a range of 3/28 or less of the flow rate of the plasma gas. Introducing a reactive gas into the plasma generation space;
9. The thin film forming method according to claim 1, wherein an oxidizing atmosphere or a reducing atmosphere is supplied in the atmospheric pressure inductively coupled plasma by the reactive gas.   The reactive gas is hydrogen gas, carbon monoxide gas, carbon dioxide gas, formaldehyde gas, sulfur dioxide, or hydrogen sulfide, and supplies a reducing atmosphere to the atmospheric pressure inductively coupled plasma. Thin film production method.   11. The thin film generation according to claim 1, wherein when generating the atmospheric pressure inductively coupled plasma, an ignition plasma generated by an electrodeless discharge means is supplied to the plasma generation chamber. Method.   The thin film generation method according to claim 11, wherein the supply of the ignition plasma is stopped after the atmospheric pressure inductively coupled plasma is generated. A plasma generation chamber having at least one gas inlet and a plasma outlet;
A mist generating means for generating a mist of a solution containing a reaction material for forming a thin film;
Plasma gas supply means for supplying a plasma gas to the plasma generation chamber;
A mist transfer gas supply means for supplying a mist transfer gas for transferring the mist generated by the mist generation means to the plasma generation chamber;
Plasma generating means for generating an atmospheric pressure inductively coupled plasma by applying energy to the plasma gas introduced into the plasma generating chamber;
With
A thin film containing at least a part of the reaction material contained in the mist supplied to the plasma generation chamber by the mist transfer gas is formed on an object to be processed close to the plasma outlet. Thin film forming equipment using atmospheric pressure inductively coupled plasma.   The said mist production | generation means is comprised by the combination of an air fog atomizer, an ultrasonic atomizer, or a nebulizer, and a classification tank, and produces | generates mist with a particle size of 50 micrometers or less, Preferably it is 20 micrometers or less. 13. The thin film forming apparatus according to 13. A reactive gas supply means for supplying a reactive gas to the plasma generation space;
An oxidizing atmosphere or a reducing atmosphere is generated in the atmospheric pressure inductively coupled plasma by the reactive gas,
15. The thin film forming apparatus according to claim 13, wherein at least a part of the reactive material is reacted with at least a part of the reactive gas.   The thin film forming apparatus according to any one of claims 13 to 15, further comprising an electrodeless discharge means for generating plasma for ignition.