JP2001329381A - Plating solution, functional thin film and method for producing functional thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plating solution for depositing an iron oxide magnetic thin film excellent in crystallinity and surface properties, to provide a magnetic thin film and to provide a method for producing the magnetic thin film. SOLUTION: A plating solution composed of a solution containing iron ions, nitrate ions and dimethylamineborane and/or trimethylamineborane is used, and nitrate nitrite reduction reaction is utilized. Namely, iron hydroxide is formed on the surface by OH- released when nitrate ions are reduced into nitrite ions by borane and is thereafter made iron oxide. Moreover, the irradiation of light with a wavelength of <=400 μm may jointly be used. Further, it is possible that an initial precipitated layer is formed by the above reaction, and, with the same as a cathode, an iron oxide film is deposited by electrolysis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a plating solution and a functional thin film which can be widely used for magnetic recording media, magneto-optical recording media, magnetic heads, magneto-optical devices, microwave devices, magneto-acoustic devices, radio wave absorbing materials and the like. And a method for producing a functional thin film. In addition, these functional thin films are expected to be applied not only to the above fields but also to the medical field. For example,
Enzyme immunoreagents (cancer screening reagents) in which a ferrite film is formed on polymer microspheres, segmented polyurethane tubes plated on the inner wall with magnetite (blood coagulation prevention), and the like are being studied.

[0002]

2. Description of the Related Art As a method for forming an iron oxide film, a sputtering method (Japanese Patent No. 2508479), a plasma CVD method, and the like.
A vacuum film forming method such as a method (Japanese Patent Publication No. 9-97647) and a solution coating method using a sol-gel reaction after applying a solution (Japanese Patent Publication No. 7-58645) are known.

On the other hand, a method of forming an iron oxide film from an aqueous solution using an inexpensive apparatus has been proposed in Japanese Patent Publication No. 63-15990.
No., and Thin Soild Films, 216, 155 (1992). A substrate having an OH group on its surface is treated with an aqueous solution containing Fe ²⁺ and another metal ion Mn ⁺ (PH = 6.5).
-8.0), Fe2 ⁺ and Mn ⁺ are adsorbed via OH groups. In this state, when an oxidizing agent such as nitrous acid (NaNO ₂ ) or O ₂ is added, ferrite is formed with an oxidation reaction of Fe ²⁺ → Fe ³⁺ . Since OH groups are present on the surface of the ferrite layer, the reaction is repeated and the ferrite layer grows with time. The inventor of the present invention, Masaki Abe, calls this method a ferrite plating method. This is a revolutionary method that enables film formation from a low-temperature aqueous solution.

[0004] Further, as a method of improving based on this technique, a uniformity improving method (Japanese Patent Publication No. 5-58252, Japanese Patent Publication No. 5-46615, Japanese Patent Publication No. 7-6072, Japanese Patent No. 2629896, No. 2,595,691 and No. 2942829), a method for improving magnetic properties (Japanese Patent No. 266)
Nos. 8998 and 2792115) and a method of forming a film on various substrates (Japanese Patent Application Laid-Open No. 63-65085).

Further, Japanese Patent No. 2841568 discloses a ferrite plating method in which light is irradiated during film formation to improve the film formation speed, or a ferrite plating method is used in which a ferrite film is deposited only on a necessary portion by scanning with a laser. Is disclosed.

On the other hand, the present inventors have disclosed a novel method for forming a metal oxide film other than iron from an aqueous solution using an inexpensive apparatus, as disclosed in JP-A-11-71112 and JP-A-9-278.
No. 437 and the Journal of Japan Institute of Electronics Packaging, Volume 3, 1
No. 40, 2000 (2000). In this method, zinc oxide or indium oxide is formed from a solution containing nitrate and dimethylamine borane. After the catalyst is applied and the initial film is grown, the film can be grown by cathodic electrolysis. At first glance, this method is similar to the ferrite plating method described above, but is completely different. That is, a nitrite-nitrite reduction reaction in which nitric acid is reduced to nitrite by utilizing a reducing agent called dimethylamine borane in the liquid is used.

[0007] In addition, the inventors of the Institute of Electrical Engineers of Japan, MAG-00-18 (2000), irradiate a substrate with light having a wavelength of 300 nm to initiate a nitrite-nitrite reduction reaction, thereby forming a ZnO film. It discloses that a film can be formed.

[0008] Both the vacuum film forming method and the solution coating method require a large-scale apparatus and are expensive. In addition, 30
A heat treatment at a high temperature of 0 ° C. or higher was required, and a substance having a low melting point and decomposition point or a substance lacking thermal stability could not be used as a substrate.

In the ferrite plating method disclosed in JP-B-63-15990, etc., a ferrous ion solution is supplied for adsorbing ferrous ions, and then a ferrous plating solution is supplied for oxidizing the adsorbed ferrous ions. Essentially requires a two-stage process of supplying an oxidant solution. In actual processing, this 2
A method is used in which two solutions are supplied almost simultaneously.
That is, the divalent iron solution and the oxidizing agent solution are mixed, and even the divalent iron ions in the solution not adsorbed on the substrate surface are oxidized into trivalent iron ions. For this reason, various improvement measures have been tried as described above, but there is no fundamental measure. For this reason, the film thickness and area that can be formed from a unit amount of solution are small, and most of the metal ions in the prepared solution are not formed into a film but are discarded as waste liquid. The formed film was also a film having poor surface properties and many pinholes and low crystallinity because trivalent iron ions were deposited on the surface as trivalent iron hydroxide having low solubility. Therefore, it has been difficult to obtain satisfactory magnetic properties. Furthermore, since the crystal structure that can be formed is a spinel-type ferrite structure, its use has been limited.

On the other hand, the nitrite-nitrite reduction method developed by the inventors has only studied only ZnO and InO. In particular, iron is the same metal as zinc and indium, but iron is a polyvalent metal that becomes an ion having a valence different from divalent or trivalent. The application of was a completely unknown territory.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide an iron oxide magnetic thin film, particularly a magnetite film, which exhibits high characteristics, by a wet film forming method using a stable plating solution.
Functional thin films such as nickel zinc ferrite film and YIG film,
And a method for producing a functional thin film at a low cost.

[0012]

(1) A plating solution containing iron ions, nitrate ions, and a reducing agent as metal ions. (2) The plating solution according to (1), wherein the reducing agent is dimethylamine borane and / or trimethylamine borane. (3) The plating solution according to the above (1) or (2), further comprising at least one metal ion selected from nickel, zinc, and yttrium as the metal ion. (4) Copper, cobalt,
Manganese, vanadium, lithium, molybdenum, titanium, magnesium, aluminum, silicon, chromium,
(1) to ((1) to (1) containing at least one element selected from tin, calcium, cadmium, indium, gallium, yttrium, samarium, europium, gadolinium, terbium, dysprosium, holonium, praseodymium, neodymium, lanthanum, and cerium. The plating solution according to any one of 3). (5) The plating solution according to any one of the above (1) to (4), wherein the oxide film is formed by a nitric acid-nitrite reduction reaction. (6) The plating solution according to any one of the above (1) to (5), on which an iron oxide film is formed. (7) The plating solution according to (5) or (6), wherein the oxide film contains non-oxide metallic iron. (8) A functional thin film containing iron oxide and boron. (9) The functional thin film according to (8), wherein the functional thin film is formed by a wet film forming method and has a boron content of 0.001 to 2% by mass. (10) The functional thin film according to the above (8) or (9), containing a nickel oxide and / or a zinc oxide. (11) The functional thin film according to the above (8) or (9), containing yttrium oxide. (12) M oxide (where M is copper, cobalt,
Manganese, vanadium, lithium, molybdenum, titanium, magnesium, aluminum, silicon, chromium,
(8) to (8) to (10) containing at least one element selected from tin, calcium, cadmium, indium, gallium, yttrium, samarium, europium, gadolinium, terbium, dysprosium, holonium, praseodymium, neodymium, lanthanum, and cerium). The functional thin film according to any of (11). (13) The above (8) containing non-oxide metal iron.
To (12). (14) A method for producing a functional thin film in which an iron oxide layer is formed by irradiation with light having a wavelength of 400 nm or less using a plating solution containing iron ions, nitrate ions and a reducing agent. (15) Using a plating solution containing iron ions, nitrate ions, and a reducing agent, forming a conductive iron oxide layer as an initial deposition layer on a non-conductive substrate, and then forming the initial iron layer in the same plating solution. A method for producing a functional thin film in which an iron oxide film is electrolytically formed using a deposition layer as a cathode. (16) A method for producing a functional thin film in which an iron oxide film is electrolytically formed using a plating solution containing iron ions, nitrate ions, and a reducing agent. (17) The method for producing a functional thin film according to the above (16), wherein the iron oxide film contains non-oxide metal iron.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a specific configuration of the present invention will be described in detail. The functional thin film formed by the wet plating method of the present invention is a thin film containing iron oxide, and is formed by a nitrite-nitrite reduction reaction in which nitric acid changes to nitrous acid. This reaction is represented by the following formulas (1) to (5). That is, when dimethylamine borane is used as a reducing agent, dimethylamine borane emits electrons e, which generate nitrous acid, and iron is formed on the surface as iron hydroxide, and then becomes iron oxide. Note that M in the formula (5) represents an example in which a metal other than iron is a divalent ion.

That is, the basic reaction is an immersion film-forming method in which the film-forming reaction proceeds without electric current from the outside only by immersing the substrate in the plating solution.

[0015] _{(CH 3) 2 NHBH 3 +} H 2 O → BO 2- + (CH 3) 2 NH + 7H + + 6e - (1) NO 3- + H 2 O + 2e - → NO 2- 2OH - ^{(2) Fe 2+ + 2OH -} → Fe (OH) 2 (3) Fe (OH) 2 → FeO + H 2 O (4) M (OH) x → MO + 1 / 2xH 2 O (5)

[Formation of Initial Deposition Layer] In the present invention, the film is continuously grown only on the initial deposition layer, which is the first film formed on the substrate, and other portions and liquids are formed. No formation reaction takes place inside. The method of forming the initial precipitation layer is roughly classified into two. A catalyst driving method using a noble metal catalyst layer of palladium, silver, or the like, and a light driving method by irradiating light, particularly, ultraviolet light having a short wavelength. When using a conductive substrate in the case of electrolytic film formation, the above treatment is not necessary, and after the initial deposition layer is formed on the substrate by electrolysis,
Film formation proceeds.

In the case of the catalyst driving system, palladium catalysis, which is widely used as a pretreatment for electroless plating, is preferably used. This is Sensitizing-
The palladium metal is adsorbed on the surface by a method such as an activation method, a catalyst-accelerator method, or an alkaline catalyst method. Instead of palladium, a silver nitrate / nickel sulfate catalyst method using silver capable of forming a denser catalyst nucleus can also be preferably used. Moreover,
It is also effective to form a catalyst layer of platinum or the like by a vacuum film forming method such as sputtering. In this case, the catalyst layer is very thin, and a thickness of 10 nm or less is sufficient. The catalyst layer does not need to be a continuous layer, and may be a cluster-like discontinuous layer.

Since the initial deposition is initiated only on the catalyst layer, the oxide film is patterned by forming the catalyst layer and then performing patterning by a photolithography method, a Sn activity reduction method by ultraviolet light exposure, or the like. For example, it is also possible to form a minute circular dot of about several tens nm or a line.

The latter method of forming an initial layer by an optical driving method involves irradiating light having a short wavelength necessary for causing a nitrite-nitrite reduction reaction. For this reason, unlike light irradiation and long-wavelength laser irradiation for applying heat, which has been performed to increase the film forming rate by a conventionally known ferrite plating method, a wavelength of 400 nm or less, particularly preferably 350 nm
The following ultraviolet rays are irradiated by a high-pressure mercury lamp, an excimer laser or the like. In addition, since it is used only to cause an initial reaction for forming an initial deposited layer, there is no need to continuously irradiate the film at all times during film formation. Completely different. Since such ultraviolet rays are extremely easily absorbed, it is possible to form a thin solution layer on the surface of the substrate and irradiate from the surface.However, a quartz plate or a sapphire plate that does not absorb ultraviolet rays is used as the substrate, and the back surface of the substrate is used. It is preferred to irradiate from Also in the case of optical driving, patterning is possible by irradiating the irradiated light to only a part of the base with a mask or the like.

[Plating Solution and Film-Forming Conditions] In the present invention, it is essential to add a reducing agent to the plating solution. As the reducing agent, various known reducing agents can be used, preferably amine-borane complex, hypophosphorous acid and the like, particularly preferably inexpensive dimethylamine borane, trimethylamine borane, or dimethylamine borane and Trimethylamine borane. It is also possible to use two different reducing agents.

The amounts of dimethylamine borane and trimethylamine borane in the liquid are not particularly limited, but are preferably 0.0001 to 1.0 mol / l in total.
Particularly preferably, it is 0.0005 to 0.5 mol / liter. Below the above range, the film forming rate is low, and above the above range, the solution becomes unstable and self-decomposes easily, which is not practical.

These dimethylamine borane and trimethylamine borane have a very large effect of preventing not only the nitric acid-nitrite reduction reaction but also the oxidation of iron ions in the plating solution to trivalent. This effect is, of course, only exerted in the plating solution containing iron ions, and is an important factor in that the functional thin film of the present invention has extremely good surface properties, that is, a structure with few defects and good magnetic properties. .

As the nitrate ion source, various known nitrate ion-containing chemicals such as nitric acid, iron nitrate, ammonium nitrate, sodium nitrate, lithium nitrate and urea nitrate can be used. In the present invention, the mechanism is basically different from the mechanism in which the reaction proceeds with either nitrite ion or nitrate ion as in the ferrite plating method described above.
For this reason, it is not nitrite ions that are present in the liquid,
Must be nitrate. The same applies to the initial deposited layer. Even if the nitrous acid is irradiated with ultraviolet light, it does not return to nitric acid nor is it reduced to ammonia, so that no film is formed. The reaction is the same when a catalyst is used.

As the metal ion source, sulfate, hydrochloride,
It is possible to use various salts such as carbonates, but nitrates are particularly preferred. This is because the presence of an anion other than the nitrate ion facilitates the formation of a hydroxide.

When only iron (Fe) is contained as a metal ion, a magnetite or hematite film is formed. And other metal (M) ions (M = copper (Cu), cobalt (Co), manganese (Mn), vanadium (V), lithium (Li), molybdenum (Mo), titanium (T
i), magnesium (Mg), aluminum (Al),
When containing silicon (Si), chromium (Cr), tin (Sn), calcium (Ca), cadmium (Cd), indium (In), and gallium (Ga); For example, when M is one type, cobalt ferrite is obtained, and when M is several types, mixed crystal ferrite such as MnZn ferrite is obtained. These elements are different depending on the composition of the target thin film, but each of the elements is 1 to 70 with respect to Fe.
About atomic% can be added.

Other metal ions in addition to the iron ions are rare earth metal (R) ions containing yttrium (Y) (R = samarium (Sm), europium (E
u), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holonium (Ho), praseodymium (Pr), neodymium (Nd), lanthanum (La),
And one or more elements selected from cerium (Ce)), a garnet-type ferrite (R ₃ Fe ₅ O ₁₂ ) or the like is obtained. These elements vary depending on the composition of the target thin film, but can be added in an amount of about 1 to 70 atomic% with respect to Fe. Since the plating solution of the present invention contains a reducing agent, metal ions in the solution are reduced, and many of them are ions having a small valence. For example, in a reagent as an ion source, even in the state of trivalent iron, it exists as divalent ions in the bath due to a reducing action.

The metal ion concentration and the nitrate ion concentration can be adjusted in a wide range. However, if any of the concentrations is too low, the film forming rate becomes extremely slow. It is easy to form, and the crystallinity of the film is lowered, so that good characteristics cannot be obtained. Therefore, the metal ion concentration and the nitrate ion concentration are each preferably 0.001 to 5 mol / l, and particularly preferably 0.01 to 0.1 mol / l.
It is preferably 5 mol / liter and the ratio of the concentration of metal ions to the concentration of nitrate ions is in the range of 0.1 to 10.

There is no particular limitation on the temperature of the plating solution.
To 95 ° C, particularly preferably 10 to 30 ° C for an optical drive system, and 20 to 70 ° C for a catalyst drive system.
It is. If it is too low, the film forming rate will be low. If it is too high, the decomposition reaction of the reducing agent tends to proceed. Although the cause is unknown at present, the valence of the metal oxide in the film changes depending on the temperature of the plating solution. For example, in the case of iron, the higher the temperature, the higher the proportion of trivalent iron. Therefore, the ratio of divalent iron and trivalent iron in the film can be controlled by the temperature of the plating solution.

The pH of the plating solution is not particularly limited, but is preferably about 3 to 9, particularly preferably 4 to 8.
It is. Below the above range, the film forming rate becomes slow, and above the above range, the liquid becomes unstable and tends to self-decompose. When a film containing a metal oxide other than iron is formed, its composition is greatly affected by pH. For this reason, it is also possible to add a known buffer to the bath in order to stably maintain the predetermined pH. For example, potassium dihydrogen phosphate, potassium phthalate, borax and the like.

In order to improve the film quality, various known organic compounds can be added to the solution. For example, dextrin, sucrose and the like.

The plating solution of the present invention is stable and can be used for a long period of time. As the film is formed,
In some cases, the amount of metal ions and the reducing agent may decrease, but in such a case, it can be used for a longer period of time by supplementing as appropriate.

Although most of the functional thin films of the present invention are non-conductive, in the case of oxide thin films such as magnetite having relatively high conductivity, they can be formed by electrolytic plating. In particular, when the substrate is made of non-conductive ceramics or the like, it is possible to perform electrolytic plating using the initially deposited layer as a cathode after the initial deposited layer is formed by the immersion method.
Electroplating makes it easy to control the film formation potential and can increase the film formation speed. The cathode potential is silver /
When a silver chloride electrode is used as a reference electrode, -0.2 to
It is preferable to be in the range of -1.7V. Above the range, the deposition rate is low, and below the range, the deposition efficiency is reduced.

Further, in the present invention, even a functional thin film having low conductivity can be formed by electrolytic plating. Although the film formation mechanism is unknown, it is considered that some conductive layer is formed on the outermost surface where the film formation is in progress. This conductive layer loses conductivity as the film-forming reaction proceeds, and it is considered that the reaction of forming a new conductive layer thereon is repeated. That is, in the present invention, it is possible to form a high-resistivity magnetic film with little deterioration due to eddy loss even by using a high frequency by an electrolytic plating method that enables high-speed film formation.

Further, when the functional thin film of the present invention is formed by electrolytic plating, it becomes possible to co-deposit a metal, that is, a non-oxide in the oxide film. And, as the cathode potential is set to a lower potential, the amount of eutectoid metal increases. The eutectoid of the metal makes it possible to obtain a magnetic film having a higher saturation magnetic flux density than the oxide. Furthermore, a granular structure film in which a fine metal phase is dispersed in the high-resistance oxide main phase can be formed, and can be used as a giant magnetoresistive film. In the present invention, metallic iron can be co-deposited not only when the film is formed by the electrolytic plating method but also when electricity is not supplied. However, in order to control the metallic iron content, an electrolytic plating method is preferred.

Then, in the functional thin film of the present invention in which iron oxide and metallic iron are mixed, the saturation magnetic flux density and Ms are increased as compared with the eutectoid ratio of metallic iron. For example,
The Ms of magnetite (iron oxide) is 480 emu / cm ³ , whereas the Ms is increased to 670 emu / cm ³ when only 5% of metallic iron is eutectoid. This is higher than 610 emu / cm ³ calculated using the conventionally known iron Ms (1700 emu / cm ³ ). This may be because special iron having a high Ms is eutectoid. Although the detailed structure is unknown, anyway, it is possible to form a film by the method of the present invention.

The functional thin film of the present invention has a thickness of 0.001.
Since about 2% by mass of boron is eutectoid, and about 0.0005 to 1% by mass of hydrogen is also eutectoid due to the cathodic reaction, these atoms having a small atomic radius are considered to be iron atoms. The fact that a special crystal structure is formed may be the cause. Also, of course, the M of the magnetite phase itself
The possibility that s has changed cannot be denied.

As the film formation potential becomes lower, the lattice constant calculated from the X-ray diffraction spectrum of the formed film tends to become smaller. From this, it is considered that boron doped in the lattice is bonded to iron ions and reduces the lattice constant.

The content of the non-oxide metal iron is about 1/100 to 1/1 in terms of the ratio to the iron oxide, but when the film formation potential is further reduced, the content becomes 1/1. It is also possible to set to １００100/1.

[Film Forming Apparatus, Substrate] The material used as the substrate is not particularly limited. For example, metal materials such as copper, iron, and aluminum, glass materials such as soda glass and non-alkali glass, ceramic materials, and plastic materials can be given. A composite material in which a polyimide resin is applied to the surface of an alumina ceramic plate or a titanium oxide fine particle composite Teflon (registered trademark) film is provided can also be used.

Each substrate needs to be subjected to optimal pretreatment, cleaning, surface adjustment, etching, etc. according to its properties and surface condition. In particular, in the case of a substrate containing iron oxide as a main component, it is possible to form a film without the need for the above-mentioned initial deposition layer.

The shape used as the substrate is not particularly limited. It is possible to form a film on a special complicated three-dimensional surface such as only a powdery, fibrous, or tubular inner wall as well as a flat surface.

In order to improve the uniformity of the film, it is possible to use various known stirring methods. For example,
Bubble agitation by air, nitrogen, oxygen, etc., cathode lock method for moving the substrate, paddle agitation for moving the rod-shaped stirring mechanism near the substrate, or superimposed ultrasonic waves (especially 28 kHz, 45 kHz , 10
It is also possible to use a high-frequency ultrasonic wave whose frequency has been increased to about 1 GHz using a method of changing the frequency depending on time or the method of changing the frequency with time.

These plating solutions are placed in a plating bath having a predetermined heating device and a filter device, and the substrate is immersed in the plating bath, thereby forming a film.

In addition to ordinary immersion plating, a spraying method in which a solution is sprayed on a substrate, and a spin coating method in which the solution is supplied while rotating the substrate, are also possible. In particular, in the case of these techniques, the solution can be easily recovered and reused. In this case, it is preferable to use after filtering with a filter of about 0.2 μm mesh or the like.

By performing the film formation in a magnetic field, it is possible to improve the magnetic characteristics. As the magnetic field, not only a DC magnetic field but also an AC magnetic field, a magnetic field from two directions in a plane, and a film formation in a rotating magnetic field in which the direction of the magnetic field rotates do not cause any problem. Of course, the same applies to the heat treatment after the film formation described later.

When it is desired to increase the film forming rate, it is possible to form a film at a temperature of 100 ° C. or higher by applying a high pressure in a pressure vessel. The use of a pre-heated substrate also increases the actual reaction temperature.

[Structure and Characteristics of Oxide Film] The functional thin film formed by the wet film formation method of the present invention is characterized by a side reaction of dimethylamine borane and trimethylamine borane.
That is, boron is contained. The content is preferably 0.01 to 2% by mass. When the ratio is less than the above range, the effect as a reducing agent is insufficient, and the film forming rate is low and not practical. On the other hand, when the ratio is more than the above range, the side reaction proceeds too much, and a film having good characteristics (such as surface properties, crystallinity, and magnetic characteristics) is not obtained.

When the plating solution contains only iron as metal ions, the functional thin film of the present invention becomes a magnetite or hematite film. When nickel and zinc are contained as other metal (M) ions, NiZn ferrite is obtained.

When the plating solution contains yttrium as another metal (M) ion, it becomes garnet type ferrite (Y ₃ Fe ₅ O ₁₂ ) or YIG. Of course, as is well known, it is also possible to form a substitutional garnet crystal in which some elements are substituted with Gd, Al, or the like.

The functional thin film of the present invention contains various elements inevitably included in the production in addition to the above-mentioned main components. Although it is technically possible to remove them, it is possible to tolerate the contamination from the balance with the cost. For example, an iron salt used as a raw material contains relatively large amounts of cobalt and nickel. As the purity of the reagent used in the present invention, JIS reagent standard grade 1 or higher, preferably special grade is used. The amount of impurities mixed into the film and the plating solution is determined from the purity of these reagents. That is, there is no problem even if it is mixed in the amount of various impurity elements contained in the primary reagent. Further, a light element such as iron or M element, hydrogen or Na or K in a metal state may be mixed. As with the above-mentioned impurities, a small amount of these may be mixed.

Further, the functional thin film of the present invention is required after film formation.
It is possible to perform a heat treatment according to the conditions. Generally heat treatment
By doing so, the strain is relaxed and a film with higher crystallinity is obtained.
It is possible to obtain. However, depending on the conditions,
The crystal structure may change, so depending on the purpose,
Select the heat treatment temperature, atmosphere, and time. For example, Fe _Three
O_FourThe film is heated at 200-400 ° C. in air for 10 minutes to 10 hours.
By performing heat treatment, γ-Fe_TwoO_ThreeCan be a membrane
You.

The functional thin film of the present invention is used after patterning or cutting and separating the entire substrate according to the purpose. If necessary, it can be laminated with another functional layer, for example, a coil layer. In the case of a high-resistance oxide magnetic thin film, for example, a NiZn ferrite film, it is also possible to laminate with a conductor coil without interposing an insulating layer.

The thickness of the functional thin film of the present invention is 0.01 μm.
It can be selected according to the purpose within the range of m to 1 mm, preferably 0.1 to 100 μm. Below the above range, it is difficult to form a uniform film, and above the above range, it takes a long time to form a film, and practical application is difficult.

The functional thin film of the present invention can be widely used for magnetic recording media, magneto-optical recording media, magnetic heads, magneto-optical devices, microwave devices, magneto-acoustic devices, radio wave absorbing materials, and the like. In addition, application to the medical field as well as the above fields is expected. For example, an enzyme immunoreagent (a cancer screening reagent) having a ferrite film formed on polymer microspheres, a segmented polyurethane tube (preventing blood coagulation) plated on the inner wall with magnetite, and the like have been studied.

[0055]

The present invention will be described below in more detail with reference to Examples and Comparative Examples. Example 1 Chromic acid-etched polyethylene terephthalate (PET) film (50 μm thick)
m) was subjected to a Pd / Sn catalysis treatment. As a plating solution, a solution of iron nitrate, 0.01 mol / l, dimethylamine borane, 0.03 mol / l was prepared,
Warmed to ° C. The catalyzed substrate was immersed in a plating solution, and a film was formed for 15 minutes while stirring with a stirrer.

On the surface of the substrate, a black specular film having a thickness of 0.5 μm was formed. MXP1 manufactured by Mac Science
FIG. 1 shows the result of X-ray diffraction using No. 8. This peak is
Magnetite was also identified from the composition analysis, and the lattice constant (a
= 8.39 nm) and a half-width (0.26 deg.), Indicating that the crystal structure was extremely clean, and that the distortion of the crystal lattice was small. The broad peak around 30 degrees is due to the influence of the substrate. The film contained 0.15% by mass of boron. When the magnetic properties of this thin film were evaluated using a vibrating sample magnetometer, a saturation magnetization of about 450 emu / cc was obtained.
A coercive force of about 800 A / m was confirmed.

Further, a magnetite film was formed on 20 similar substrates for 3 days using the plating solution used in this example, but a stable film formation was possible to the end.

Next, the same film formation was carried out by changing the amount of dimethylamine borane in the plating solution to 0.00001 to 1.5 mol / liter, and the same evaluation was performed.
As a result, the boron content in the film was 0.001 to 2% by mass.
It has been found that the films having the above-mentioned range show good crystallinity, are excellent in bath stability, and have a practically acceptable film forming rate.

Example 2 After forming a 0.5 μm initial deposited layer in 5 minutes under the same conditions as in Example 1, continuously about 100 mA (−1. Electroplating was performed at a constant potential of 3 V) for 60 minutes. This film thickness 15μ
The m 2 black film was also magnetite. 0.9 for this film
% By weight of boron.

Example 3 In Example 1, in addition to iron, copper, cobalt, manganese, vanadium, lithium, molybdenum, titanium, magnesium, aluminum, silicon, chromium, tin, calcium, cadmium, indium, yttrium, samarium , Europium, gadolinium, terbium, dysprosium, holonium,
It was confirmed that a thin film could be formed even when at least one element selected from praseodymium, neodymium, gallium, lanthanum, and cerium was added.

Comparative Example 1 A substrate treated in the same manner as in Example 1 was immersed in a solution obtained by removing dimethylamine borane from a plating solution, but no reaction occurred.

[Comparative Example 2] Instead of iron nitrate in the plating solution, iron sulfate having the same mole number of iron ions was used, and nitric acid was added to a solution in which the same mole number of sodium nitrite was added. The substrate, which had been subjected to the same catalyst treatment as in Example 1, was immersed, but no reaction occurred.

Example 4 A light-driven oxide plating apparatus shown in FIG. 2 was used to irradiate light 20 from the back surface of a quartz plate that transmits light having a wavelength of 300 nm as a substrate 11. In FIG. 2, a plating bath 13 is filled with a plating solution 14, and a substrate 11 is mounted in an opening opening on one side. The plating tank 13 is provided with a lid 21 and is immersed in a heating tank 16 filled with water 15 controlled to a predetermined temperature. A temperature control means for controlling the heater 17 is connected to the heating tank 16 so that the water 15 in the heating layer 16 can be heated and maintained at a predetermined temperature. Behind the substrate 11 mounted on the plating tank 13, an ultraviolet irradiation device 19 is disposed,
Ultraviolet rays can be irradiated from the back side of the base 11.

First, as the plating solution 15, iron nitrate was added.
02 mol / l, trimethylamine borane, 0.0
A solution prepared by adding an appropriate amount of nickel nitrate and zinc nitrate to 1 mol / liter was prepared, and heated to 20 ° C. by the heating tank 16.
The plating tank 13 was irradiated with ultraviolet light having a wavelength of 300 nm from the ultraviolet irradiation device 19 to the back surface of the substrate 11 through a mask.
Irradiation was performed for only 5 minutes, and after confirming that film formation had started, film formation was performed for 2 hours without irradiation.

The black specular film 12 was formed to a thickness of 15 μm only on the portion of the substrate surface where light was irradiated. X-ray diffraction, composition analysis, and metal valence analysis revealed that the film was a NiZn ferrite film. When the surface of this film was observed with an atomic force microscope (AFM), it was confirmed that the film had an extremely smooth surface with a surface roughness of 3.2 nm as shown in FIG. Further, this film contained 0.3% by mass of boron.

Comparative Example 3 A wavelength of 78 was used instead of ultraviolet rays.
Irradiation with a 0 nm infrared laser was performed from the back, but the decomposition reaction of dimethylamine borane proceeded violently and the plating bath was self-decomposed.

Example 5 As a plating solution, iron nitrate
0.2 mol / l, trimethylamine borane, 0.
A solution in which an appropriate amount of yttrium nitrate was added to 3 mol / liter was prepared and heated to 70 ° C.

On an alumina substrate (500 μm thick), Pt
Was formed by sputtering to an average film thickness of 3 nm.
Further, patterning was performed using a negative photoresist, and an opening was provided only in a portion where an oxide film was to be formed. The substrate was immersed in a plating solution, and a film was formed for 3 hours while oscillating at a frequency of 1 Hz.

On the surface of the substrate, a brown mirror-like film having a thickness of 5 μm was formed. From X-ray diffraction and composition analysis to YIG
Was identified. This film contained 0.5% by mass of boron.

Example 6 An aqueous solution containing 0.01 mol / L iron (III) nitrate hydrate and 0.03 mol / L dimethylamine borane (DMAB) at a temperature of 20 to 60 ° C. and a pH of 3 was used as an electrolyte. . Corning 1737 glass was used for the substrate.
Before the film formation, the glass substrate was activated using a catalyst imparting agent (Uemura Kogyo Co., Ltd., S-10X, MSA-27, A-10X) which is industrially used. Without this treatment, no film was deposited on the substrate. Of course, when a conductive substrate is used, this processing is not necessary.

First, the potential is raised from +1400 mV to -1400 mV.
While changing the voltage to mV (with reference to a silver / silver chloride standard electrode), electrolytic film formation was performed to prepare a sample. When the potential was positive, the film was formed on the anode side, and when the potential was negative, the film was formed on the cathode side. However, for anodic deposition +1600 to +1200 mV
At a potential of, a yellow-brown film was formed, and as a result of analysis, it was a trivalent iron oxide.

Under the conditions of this embodiment, +1000 mV to -3
In the range of 00 mV, the film formation reaction hardly proceeded for both the cathode and the anode. On the other hand, at a potential of -400 mV or less, the power supply voltage during film formation hardly changed, and a film of about 0.5 to 4 μm was obtained on the cathode by film formation for 1 hour. Table 1 shows the evaluation results of these samples. The data for magnetite and metallic iron are also shown.

[0073]

[Table 1]

FIG. 4 shows a sample formed at a potential of -1400 mV by FeCA by surface analysis using photoelectron spectroscopy (ESCA).
It is an analysis result of the chemical state of a peak. Ferrous iron (708.
8eV), trivalent iron (710.8 eV) and metallic iron (70
A peak of 6.6 eV) was clearly observed. As a result of the X-ray diffraction analysis, the main component of each film was magnetite. Also, these films have a thickness of 0.15 to 1.35.
It contained boron by mass.

The effects of the present invention are clear from the above results.

[0076]

As described above, according to the present invention, an iron oxide magnetic thin film, particularly a magnetite film and a nickel zinc ferrite film exhibiting high characteristics, can be efficiently formed by a wet film forming method using a stable plating solution. , A functional thin film such as a YIG film, and a method for manufacturing the functional thin film can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a view showing an X-ray diffraction pattern of a magnetite film of the present invention.

FIG. 2 is a schematic view of a light-driven plating apparatus that can be used in the present invention.

FIG. 3 shows an AFM surface shape image of a NiMn ferrite film of the present invention.

FIG. 4 is a view showing the measurement results of a metal iron-containing, iron oxide thin film of Example 6 by photoelectron spectroscopy.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Substrate 12 Thin film 13 Plating tank 14 Plating solution 15 Water 16 Heating tank 17 Heater 18 Temperature control means 19 UV irradiation device 20 UV

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Osamu Shinoura 1-1-13 Nihonbashi, Chuo-ku, Tokyo TDK Corporation F-term (reference) 4K044 AA02 AA06 AA12 AA13 AA16 BA12 BB01 BB03 BC04 BC14 CA17 CA53

Claims (17)

[Claims] 1. A plating solution containing iron ions, nitrate ions, and a reducing agent as metal ions. 2. The plating solution according to claim 1, wherein the reducing agent is dimethylamine borane and / or trimethylamine borane. 3. The plating solution according to claim 1, wherein the metal ions further contain at least one metal ion selected from nickel, zinc, and yttrium. 4. The metal ions further include copper, cobalt, manganese, vanadium, lithium, molybdenum,
Titanium, magnesium, aluminum, silicon, chromium, tin, calcium, cadmium, indium, gallium, yttrium, samarium, europium, gadolinium, terbium, dysprosium, holonium,
The plating solution according to any one of claims 1 to 3, wherein the plating solution contains at least one element selected from praseodymium, neodymium, lanthanum, and cerium. 5. The plating solution according to claim 1, wherein the oxide film is formed by a nitric acid-nitrite reduction reaction. 6. The plating solution according to claim 1, wherein an iron oxide film is formed. 7. The plating solution according to claim 5, wherein the oxide film contains non-oxide metal iron. 8. A functional thin film containing iron oxide and boron. 9. The functional thin film according to claim 8, which is formed by a wet film forming method and has a boron content of 0.001 to 2% by mass. 10. The functional thin film according to claim 8, which contains nickel oxide and / or zinc oxide. 11. The functional thin film according to claim 8, comprising yttrium oxide. 12. An oxide of M (where M is copper, cobalt, manganese, vanadium, lithium, molybdenum,
Titanium, magnesium, aluminum, silicon, chromium, tin, calcium, cadmium, indium, gallium, yttrium, samarium, europium, gadolinium, terbium, dysprosium, holonium,
The functional thin film according to any one of claims 8 to 11, comprising at least one element selected from praseodymium, neodymium, lanthanum, and cerium). 13. The functional thin film according to claim 8, further comprising a non-oxide metal iron. 14. A method for producing a functional thin film in which an iron oxide layer is formed by irradiation with light having a wavelength of 400 nm or less using a plating solution containing iron ions, nitrate ions and a reducing agent. 15. An electroconductive iron oxide layer is formed as an initial deposition layer on a non-conductive substrate using a plating solution containing iron ions, nitrate ions, and a reducing agent. A method for producing a functional thin film, wherein an iron oxide film is electrolytically formed using the initial deposition layer as a cathode. 16. A method for producing a functional thin film by electrolytically depositing an iron oxide film using a plating solution containing iron ions, nitrate ions, and a reducing agent. 17. The method according to claim 16, wherein the iron oxide film contains non-oxide metal iron.