JP2007158091A - Method for producing soft magnetic thin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a soft magnetic thin film with which a soft magnetic thin film comprised of an alloy containing Co and Fe as the main components and having a high saturated magnetic flux density and a low coercive force can be obtained without thermal treatment. <P>SOLUTION: When producing a soft magnetic thin film comprised of an alloy containing Co and Fe as the main components, by performing electric plating using an electric plating solution containing Co ions and divalent Fe ions; electric plating is performed with a pulse reverse electrolytic technique alternately giving a pulse current with an object to be plated as a cathode for causing this object to deposit the alloy, and a pulse reverse current with the object to be plated as an anode. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a soft magnetic thin film containing Co and Fe as main components.

  Soft magnetic thin films are widely used in electronic parts used in the electronic industry such as thin film magnetic heads, thin film inductors, and thin film transformers. In particular, in order to perform high-density magnetic recording with a thin film magnetic head, it is necessary to reduce the recording bits, and for this purpose, the thin film magnetic head must generate a strong write magnetic field. The soft magnetic thin film used for the head needs to be formed using a soft magnetic material having a high saturation magnetic flux density (Bs). In addition, in thin film inductors and thin film transformers, a soft magnetic material having a high saturation magnetic flux density as well as a thin film magnetic head is required in order to realize miniaturization and thinning.

  As a magnetic thin film having a high saturation magnetic flux density, for example, the following Patent Document 1 discloses a method for producing a CoNiFe soft magnetic thin film having a saturation magnetic flux density of 1.7 to 2.1 T by electroplating. 2 shows a method for producing a CoFeNi soft magnetic film having a saturation magnetic flux density of 2 to 2.3 T by electroplating.

  In recent years, for the purpose of increasing the density of magnetic recording and the like, the main component is CoFe having a higher saturation magnetic flux density than the NiFe-based alloy or the CoNiFe-based alloy conventionally used as a soft magnetic thin film. It has been studied to use an alloy.

  The saturation magnetic flux density of the CoFe alloy is described in detail in the following Non-Patent Document 1, and theoretically when the composition is approximately 5 at% ≦ Co ≦ 70 at% and 30 at% ≦ Fe ≦ 95 at%. It is shown that the saturation magnetic flux density is 2.2 T or more, and especially when Co is about 35 at% and Fe is about 65 at%, the saturation magnetic flux density is the highest, about 2.4 T. Non-Patent Document 2 described below describes that the saturation magnetic flux density of a CoFe alloy film of approximately 90 at% Co and approximately 10 at% Fe formed by electroplating is approximately 1.9 T. .

  On the other hand, Non-Patent Document 3 below shows a CoFe alloy film in which Co is about 35 at% and Fe is about 65 at%. However, although this film has a composition that exhibits the highest saturation magnetic flux density, the saturation magnetic flux density is about 2.0 T, and the expected high saturation magnetic flux density cannot be achieved.

In view of such a point, the present applicant has previously described "a method for producing a soft magnetic thin film made of an alloy containing Co and Fe as main components, and comprising a cathode chamber and a diaphragm or a salt bridge. A plating tank having a chamber and an anode chamber that is capable of charge transfer but is isolated so as to prevent permeation of Fe ions, and the cathode chamber contains a plating solution containing Co ions and divalent Fe ions. A method for producing a soft magnetic thin film characterized in that an object to be plated is immersed in the plating solution, an electrolytic solution is accommodated in the anode chamber, and the anode is immersed in the electrolytic solution for electroplating.
Was proposed (Japanese Patent Laid-Open No. 2004-21068).

  According to this method, a soft magnetic thin film having a Bs of 2.4 T can be easily obtained. In this case, a thin film with good crystallinity can be obtained by electroplating using a pulse current. Further, the thin film as obtained by the above method has a coercive force (Hc) of about 15 Oe, which is inferior in terms of soft magnetic properties, but by heat-treating this thin film at 400 ° C., Hc becomes 10 Oe or less, By performing the heat treatment in this way, it is possible to reduce the coercive force while maintaining a high saturation magnetic flux density.

  However, a heat treatment temperature such as 400 ° C. may adversely affect other components in the magnetic recording head manufacturing process and the like, and therefore, a method of obtaining a soft magnetic thin film having high Bs and low Hc without heat treatment. Was desired.

Japanese Patent No. 2821456 JP 2000-322707 A JP 2004-216808 A R. M.M. Bozorth, “Ferromagnetism”, D.C. Van Nostrand Co. Inc. , N.M. Y. , 1951 IEEE. Trans. Magn. 1987, Vol. 23, p. 2981 IEEE. Trans. Magn. 2000, 36, p. 3479

  The present invention has been made in response to the above-mentioned demand, and is made of an alloy containing Co and Fe as main components, and a soft magnetic thin film having a high saturation magnetic flux density and a low coercive force can be obtained without heat treatment. It aims at providing the manufacturing method of.

  As a result of intensive studies to achieve the above object, the present inventors have performed pulse electroplating when producing a soft magnetic thin film using an electroplating solution containing Co ions and divalent Fe ions. In this case, in the so-called pause time in which the application of the pulse current is stopped, the current value is not set to 0, but a reverse pulse current (pulse reverse current) is given, that is, the cathode current is added in accordance with the convention, the anode current Is negative, it is effective to apply a negative current during the downtime when the pulse current (positive current) is not applied, and the pulse reverse electrodeposition method that gives a pulse reverse current during such a downtime By adopting it, it has a high saturation magnetic flux density Bs of about 2.2 to 2.4 T without performing heat treatment in the state of being deposited, It found that the soft magnetic thin film made of a CoFe alloy having the following low coercive force Hc 0 Oe is obtained, in which the present invention has been accomplished.

  Therefore, the present invention provides an electroplating solution containing an electroplating solution containing Co ions and divalent Fe ions to produce a soft magnetic thin film made of an alloy containing Co and Fe as main components. A soft magnetic thin film characterized in that electroplating is carried out by a pulse reverse electrodeposition method in which a plated object is used as a cathode and a pulse current for precipitating the above alloy and a pulse reverse current using the object to be plated as an anode are alternately applied. A manufacturing method is provided.

In this case, the absolute value of the ratio of the pulse reverse current density i _pr to the pulse current density _{i p | i pr / i p} | is 0.05 to 0.3, the pulse current applied time t _on the pulse reverse current attachment time The total time T with t _off is preferably 0.002 to 0.1 seconds, and the ratio t _on / T of the pulse current application time t _{on to} the total time T is preferably 0.1 to 0.8, the pulse current density i _p is 10 to 100 / cm ^2, it is preferable pulse reverse current density i _pr is -5~-20mA / cm ^2. In the present invention, the dissolution current is indicated by minus and the deposition current is indicated by plus.

  According to the present invention, a soft magnetic thin film having a high saturation magnetic flux density and a low coercive force can be easily produced without heat treatment.

  The method for producing a soft magnetic thin film according to the present invention performs electroplating by pulse reverse electrodeposition using an electroplating solution containing Co ions and divalent Fe ions.

Here, as the plating solution used in the method of the present invention, a solution containing Co ions and divalent Fe ions is used. As a source of these metal ions, water-soluble cobalt salts and water-soluble iron (II) salts are preferably used. Co or Fe (divalent) sulfate, chloride, sulfamate, acetate, nitrate A water-soluble salt such as can be used. The metal ion concentration in the plating solution may be selected so as to obtain a desired magnetic property, and is not particularly limited, but each metal salt concentration is 0.01 to 1.5 mol / dm ³ , particularly 0.01 to It is preferably 0.3 mol / dm ³ , especially 0.01 to 0.1 mol / dm ^3, and the total metal ion concentration is 0.02 to 3.0 mol / dm ³ , particularly 0.02 to 0.0. 6 mol / dm ^3, particularly it is preferable that the 0.02~0.2mol / dm ^3.

  In addition, a conductive salt such as ammonium chloride, a buffering agent such as boric acid, and a surfactant such as sodium dodecyl sulfate and sodium dodecylbenzene sulfonate can be added to the plating solution at a normal dose.

  On the other hand, it is desirable not to add a sulfur-containing compound such as saccharin used as a stress relaxation agent or brightening agent. This is because when these are used, sulfur eutectoids occur in the film, and the corrosion resistance may be deteriorated.

The plating solution may be slightly oxidized by oxygen dissolved in the solution when exposed to air, but for the purpose of suppressing this, magnetic properties such as the saturation magnetic flux density of the soft magnetic thin film. Reducing agents such as ascorbic acid, hypophosphorous acid, trimethylamine borane, dimethylamine borane, thiourea, or salts and derivatives thereof can be added to the extent that they do not affect the above. In this case, the amount of the reducing agent added is appropriately determined depending on the type of the reducing agent, but is preferably 0.01 mol / dm ³ or less.

  The pH of the plating solution of the present invention is preferably acidic to weakly acidic, preferably pH = 1 to 6, particularly preferably pH = 1.8 to 4. Moreover, as for the temperature of a plating bath, 5-30 degreeC is desirable.

  In the method of the present invention, as an object to be plated, a known base substrate for forming a soft magnetic thin film can be used in electronic parts such as a thin film magnetic head, a thin film inductor, and a thin film transformer. As such, in the case of a non-conductive material such as a glass substrate, a conductive film or the like can be provided on the surface to be plated by sputtering or electroless plating in advance.

  In the method of the present invention, it is desirable to perform plating while quantitatively stirring using a rotating disk electrode (RDE), a paddle device or the like. It is also possible to perform plating by rotating or swinging an object to be plated. However, stirring by air bubbling should be avoided because it may cause oxidation of the plating solution. The thickness of the soft magnetic thin film produced by plating is preferably 0.01 to 10 μm, particularly preferably 0.1 to 1 μm.

  Further, as a method of the present invention, a plating solution is accommodated in a plating tank, the object to be plated and the anode are respectively immersed in this plating solution, and a current is passed between the object to be plated and the anode to soften the object to be plated. A method of forming a magnetic thin film can be employed. In this case, the anode may be an insoluble anode such as platinum, titanium, or carbon, but a soluble anode is preferably used.

As described above, by using the soluble anode, the anode is dissolved during plating, so that even if the anode is in contact with the plating solution, the divalent Fe ions in the plating solution are not oxidized by the anode. Accordingly, the produced soft magnetic thin film does not incorporate hydroxides derived from trivalent Fe ions generated by oxidation of divalent Fe ions, and the saturation magnetic flux density is very close to the theoretical value. Can be produced.
In this case, the soluble anode is preferably cobalt, iron or an alloy thereof.

  Alternatively, a plating chamber having a cathode chamber and an anode chamber separated from the cathode chamber by a diaphragm or a salt bridge so as to be able to transfer charges but to prevent permeation of Fe ions is used. A plating solution containing divalent Fe ions is accommodated, an object to be plated is immersed in the plating solution, an electrolytic solution is accommodated in the anode chamber, and an anode is immersed in the electrolytic solution to perform electroplating. It may be.

  In the present invention, the electroplating is performed using the pulse reverse electrodeposition method in the above-described plating bath composition and plating conditions. In this pulse reverse electrodeposition method, as shown in FIG. 1, first, a pulse current (positive current) for depositing a CoFe alloy with the object to be plated as a cathode and a pulse reverse current (negative current) with the object to be plated as an anode. ) Alternately, and when a pulse reverse current is applied, the deposited CoFe alloy acts to dissolve.

In this case, when the pulse current density is i _p and the pulse reverse current density is i _pr , the absolute value | i _pr / i _p | of the ratio is 0.05 to 0.3, particularly 0.1 to 0.2. In order to achieve the object of the present invention, the pulse current application time is t _on , the pulse reverse current application time is t _off , and the total time of t _on and t _off is T (= t _on + t _off ), T is set to 0.002 to 0.1 seconds, particularly 0.005 to 0.02 seconds, and t _on / T is set to (duty ratio γ) of 0.1 to 0.8, particularly 0.2. In order to achieve the object of the present invention, it is preferably set to ˜0.4.

Furthermore, i _p is 10 to 100 / cm ^2, particularly 50~90mA / cm ^2, especially 60~80mA / cm ^2, i _pr is -5~-20mA / cm ^2, particularly -8~-18mA / cm ^2, In particular, it is preferably −15 to −18 mA / cm ² .

  The soft magnetic thin film of the present invention is made of an alloy containing Co and Fe as main components, but it is particularly preferable that the soft magnetic thin film is substantially free of components other than Co and Fe. However, it is not limited to this and may contain other metal components. For example, by adding Ni for the purpose of reducing the coercive force, improving the corrosion resistance of the soft magnetic thin film, or changing the hardness, it is possible to co-deposit nonmagnetic metal elements such as W, Mo, and Cr. It can also be contained. In this case, plating may be performed by adding ions containing a desired metal element or an oxo acid or oxo acid salt containing a metal element to the plating solution.

  Here, according to the method of the present invention, a soft magnetic thin film made of an alloy containing Co and Fe as main components can be efficiently manufactured. In particular, the content of Co and Fe is 5 at% ≦ Co ≦ 70 at%, 30 at% ≦ Fe ≦ 95 at% Suitable for producing a soft magnetic thin film. In this case, the saturation magnetic flux density is 2.0 T or more, particularly 2.1 T or more, especially 2.2 T or more. The soft magnetic thin film can be manufactured.

  Further, the method of the present invention is more suitable for producing a soft magnetic thin film in which the contents of Co and Fe are in the range of 30 at% ≦ Co ≦ 50 at% and 50 at% ≦ Fe ≦ 70 at%. A soft magnetic thin film having a saturation magnetic flux density of 2.3 T or more, particularly 2.35 T or more, particularly about 2.4 T can be produced.

  Furthermore, in this case, according to the present invention, a coercive force of about 1 Oe can be achieved without heat treatment when the coercive force Hc is 10 Oe or less, particularly 8 Oe or less, especially 6 Oe or less.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

[Examples and Comparative Examples]
Cobalt / iron plating was performed under the bath composition and plating conditions shown below. In this case, the substrate on which the soft magnetic thin film was formed was a copper foil and a glass plate sputtered with permalloy (100 nm) / Ti (10 nm). The film formation was performed by a pulse reverse electrodeposition method using a paddle apparatus. In the following, the cathode current is indicated by plus according to the convention, and the anode current is indicated by minus.

Bath composition H ₃ BO ₃ 0.40 mol / dm ³
NH ₄ Cl 0.40 mol / dm ³
CoSO ₄ .7H ₂ O 0.05 mol / dm ³
FeSO ₄ .7H ₂ O 0.05 mol / dm ³
Trimethylamine borane 0.0005 mol / dm ³
Sodium lauryl sulfate 0.01 g / dm ³
Film formation conditions Bath pH 2.3
Bath temperature Room temperature stirring (rotation speed) 150rpm
Anode Co
Current Pulse reverse condition shown in Fig. 1
Pulse reverse condition (see Fig. 1)
Time T 0.01 seconds Pulse current density i _p 75 mA / cm ²
Pulse reverse current density i _pr 0 to −20 mA / cm ²
Duty ratio γ 0.3

  About the CoFe alloy obtained by said method and conditions, saturation magnetic flux density Bs (T) and coercive force Hc (Oe) were measured. The results are shown in FIGS. Bs and Hc were measured using a vibrating sample magnetometer (VSM).

The pulse current waveform is shown. It is a graph which shows the relationship between Bs value and i _pr . It is a graph which shows the relationship between Hc value and _ipr .

Claims (3)

  When electroplating is performed using an electroplating solution containing Co ions and divalent Fe ions to produce a soft magnetic thin film made of an alloy containing Co and Fe as main components, the object to be plated is used as a cathode. A method for producing a soft magnetic thin film, wherein electroplating is performed by a pulse reverse electrodeposition method in which a pulse current for precipitating the alloy and a pulse reverse current having an object to be plated as an anode are alternately applied. The absolute value of the ratio of the pulse reverse current density i _{pr to} the pulse current density i _p | i _pr / i _p | is 0.05 to 0.3, and the pulse current application time t _on and the pulse reverse current application time t _off are 2. The soft magnetism according to claim 1, wherein the total time T is 0.002 to 0.1 seconds, and the ratio t _on / T of the pulse current application time t _{on to} the total time T is 0.1 to 0.8. Thin film manufacturing method. Pulse current density i _p is 10 to 100 / cm ^2, a pulse reverse current density i _pr is -5 to-20 mA / cm ² in a claim 1 or 2 method for producing a soft magnetic thin film according.

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