JPH05190327A - Magnetic thin film and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a highly corrosion-resisting magnetic thin film of low coercive force and high saturation magnetic flux density by a wet plating method excellent in mass productivity. CONSTITUTION:A Co-Fe-Rh alloy film is formed by plating to obtain a magnetically soft thin film with the Rh content being 1-8wt% and having the S content of 500-2000ppm. The magnetic thin film is excellent in corrosion resistance and has an excellent soft magnetism characteristic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic thin film formed by a wet plating method.

[0002]

2. Description of the Prior Art Magnetic thin films for thin film magnetic heads and thin film transformers are required to have excellent soft magnetic properties such as low coercive force, high saturation magnetic flux density and low magnetostriction, and at the same time have high corrosion resistance for improving reliability. is necessary.

These magnetic thin films are generally formed by a vapor phase film forming method such as a sputtering method or a liquid phase film forming method such as an electroplating method. However, the liquid phase plating method has a large area. Is advantageous in that it can be easily formed, a highly uniform film can be obtained, and the number of steps is small.

Particularly, the recent increase in recording density is largely due to the increase in coercive force of the recording medium. In order to sufficiently write on a recording medium having a large coercive force, it is necessary to generate a stronger magnetic field from the recording head. For this reason, there has been a demand for a material having a high saturation magnetic flux density which is higher than that of the Ni-Fe alloy (permalloy) which has been widely used in the past. A Co—Fe alloy is an example of a magnetic plating film that satisfies the magnetic property requirements.

However, the corrosion resistance was inferior to that of Ni-Fe alloy which is a relatively low saturation magnetic flux density material which has been widely used in the past.

The addition of the third element is effective for improving the corrosion resistance of the Co-Fe alloy, but it has been difficult to improve the corrosion resistance without impairing the excellent soft magnetic characteristics.

[0007] For example, the addition of Pd, Pt, Au, Cu or the like can improve the corrosion resistance, but it has an influence on the soft magnetic properties, so that it was not possible to contain a sufficient amount of noble metal in the film.

[0008]

The present invention has been made under such circumstances, and a method of plating a magnetic thin film having a low coercive force, a high saturation magnetic flux density and a high corrosion resistance without complicated management of a plating bath is provided. The purpose is to form a film.

[0009]

Means for Solving the Problems As a result of intensive studies and research for solving the above-mentioned problems, the present inventor has found that adding Rh to Co—Fe alloy plating has excellent corrosion resistance and does not impair magnetic properties. We have completed the magnetic material. Moreover, the composition control of the film does not depend only on the metal ion concentration in the bath or the metal ion concentration ratio, but is controlled by the current density at the time of film formation, or Rh ions in the bath are replenished as the electrolysis progresses. A stable film composition, that is, stable corrosion resistance and high soft magnetic properties can be obtained.

Such an object is achieved by the present invention described in (1) and (2) below.

(1) Co, Fe and Rh as main components, the content of Rh is 1 to 8% by weight, and the content of S is 5
A magnetic plating thin film, which is characterized in that it is 0.00 to 2000 ppm.

(2) A film formed by a wet plating method has a cobalt ion concentration of 0.05 to 5 mol / l, an iron ion concentration of 0.001 to 5 mol / l, and a pH of 1.0 to 4.0. A method for producing a magnetic thin film, characterized in that a low molecular organic compound having sulfur is dissolved in a bath.

[0013]

The magnetic thin film of the present invention is formed by a wet plating method, that is, an electroplating method, an electroless plating method and a displacement plating method, and contains Co and Fe as main components and contains Rh and S.

With such a composition, the magnetic thin film of the present invention can easily obtain a coercive force Hc of 3 Oe or less, particularly 1 Oe or less and high corrosion resistance, and is extremely useful as a magnetic thin film for a thin film magnetic head or a thin film transformer, for example. It is useful.

Moreover, although three kinds of metal ions of Co, Fe and Rh are present in the plating bath used for forming the magnetic thin film of the present invention, the metal ion concentration in the bath and the metal ion concentration in the bath are used to control the film composition. By controlling not only the metal ion composition ratio but also the current density during film formation, a film having a stable composition can be easily formed.

The magnetic alloy of the present invention contains C, Cr, C.
u, Sn, Ru, Au, Pd, Ag, Mn, P, B, I
It is expected that the high frequency characteristics will be improved by containing 3 wt% or less of one or more elements selected from n, Mo, Pb, Re, W, Zn, Zr, Pt and the like. Further, even if a trace amount of these elements is contained as an impurity, no particular trouble is observed, so that the cost can be reduced by using an inexpensive reagent.

However, it should be noted that the content of 3% by weight or more often adversely affects the magnetic properties and lowers Bs.

[0018]

[Specific Structure] The specific structure of the present invention will be described in detail below.

The magnetic thin film of the present invention is formed by a wet plating method and contains S with Co, Fe and Rh as the main components.

The content of Rh is 1 to 8% by weight, preferably 3 to 7% by weight. If the content of Rh is less than the above range, sufficient corrosion resistance cannot be obtained, and if it exceeds the above range, the soft magnetic properties deteriorate.

The content of S is 500 to 2000 ppm,
It is preferably 800 to 1500 ppm. If the content of S is less than the above range, a low coercive force Hc cannot be obtained, and if it exceeds the above range, the corrosion resistance decreases.

The magnetic thin film of the present invention has low Hc and excellent corrosion resistance. Specifically, Hc of 3 Oe or less, particularly 1 Oe or less, and further 0.5 Oe or less can be obtained. As for the corrosion resistance, a value of -70 mV or more is obtained at a natural potential using a silver / silver chloride electrode as a reference electrode in a 0.01N-KCl solution. This is equivalent to or better than Permalloy.

The plating bath preferably used in the present invention contains cobalt ions, iron ions, and Rh ions, and further contains a low molecular organic compound containing S.

As the cobalt ion, iron ion and Rh ion source used in the present invention, it is preferable to use a water-soluble salt such as sulfate, chloride, sulfamate, acetate or nitrate. Cobalt ions and iron ions can be effectively used as ions that are naturally dissolved by immersing a metal in a plating bath and ions that are dissolved by electrolysis as an anode.

The concentration of cobalt ion is preferably 0.05 to 5 mol / l, particularly 0.1 to 1 mol / l.
If the concentration of cobalt ions is less than the above range, the deposition rate is remarkably reduced, and if it exceeds the above range, the viscosity of the plating bath increases, and workability and film formation in a fine resist pattern are generally difficult.

The iron ion concentration in the plating bath is in the range of 0.001 to 5 mol / l, more preferably 0.01 to 1 mol / l. Since the concentration ratio with cobalt ions is a major factor in determining the composition of the film to be formed, it may be determined so that a desired film composition can be obtained.

However, when the iron ion is zero, CoRh
It becomes a film and has an HCP structure, and the soft magnetic properties are not sufficient.
Generally, a composition in which the saturation magnetostriction is zero is preferable.

The concentration of Rh ions in the plating bath is
Usually 0.005 to 5 g / l, more preferably 0.01
~ 0.5 g / l. Since Rh has a far different deposition potential from Co and Fe, in order to co-deposit it with Co and Fe, the Rh ion concentration in the bath should be made smaller than the Co and Fe ion concentrations to use a diffusion-controlled precipitation reaction. To do. That is, Rh
When focusing only on ions, the amount of Rh metal deposited is constant regardless of the current density. The composition ratio of the film is determined by the amounts of Co and Fe that are additionally deposited.

The pH of the bath is 1.0 to 4.0, especially 2.0 to 4.0.
3.0 is preferable. Below the above range, the film formation rate is slow,
If the content is more than the above range, precipitation of ferric iron is likely to occur.

When the current density is low and the deposition potential of Co and Fe is lower than that, a pure Rh film is formed and the current density becomes high, and Co,
A CoFeRh alloy is obtained when the precipitation potential of Fe is higher than the precipitation potential.

Then, as the current density increases, the CoFe precipitation rate increases, and the Rh content in the film relatively decreases.

To obtain a metal thin film having a constant Rh content, R
In order to keep the h ion concentration constant, it is possible to replenish the ions that are deposited and reduced according to the film formation. Replenishment is easy if the consumption is stable.

The Rh content can also be kept constant by controlling the current density during film formation, that is, the potential. In this case, the film forming rate of the entire film changes, but it is possible to avoid the trouble of bath management.

As the iron ion, divalent iron ion is preferable. However, divalent iron ions are easily oxidized to trivalent iron ions. If the amount of trivalent iron ion is small, it does not matter, and it may be effective in leveling property. Further, it can be easily reduced to divalent iron ions, and it is easy to prevent the generation.

As a reducing method, a reducing agent such as ascorbic acid, hypophosphorous acid or a salt thereof is added, or Co or Fe is added.
It is generally known to utilize a side reaction when the above metal is immersed in a plating bath and spontaneously dissolved.

As the low molecular weight organic compound containing sulfur, those having various structures are effective, but aromatic sulfonates, particularly sodium naphthalene trisulfonate are preferable.

It is considered that sulfur in the plating film is segregated at the grain boundaries of the crystals to hinder grain growth, and is effective in reducing internal stress. The source of sulfur is a low molecular weight organic compound containing sulfur contained in the bath.

It is also preferable that the plating bath contains unsaturated alcohol. Particularly, a low molecular weight alcohol having an acetylene bond is preferable, and the lowest molecular weight compound is propargyl alcohol.

This unsaturated alcohol is also effective in improving various characteristics of the plating film, but its mechanism is unknown in many cases. There may be 100-2000 ppm C in the membrane, one source of which is believed to be unsaturated alcohols.

In the plating bath, in addition to these, components such as pH buffering agents such as boric acid, conductive salts such as ammonium sulfate and ammonium chloride, and surfactants such as sodium lauryl sulfate are added to ordinary electroplating baths. It is preferably contained.

Further, in order to obtain particularly soft magnetic characteristics, it is preferable that the plating bath contains ammonium ions, especially ammonium chloride. However, the cause is unknown.

The magnetic thin film of the present invention preferably imparts uniaxial anisotropy in a desired direction.

As this method, film formation in a magnetic field or annealing in a magnetic field after the film formation can be used.

The film formation in a magnetic field is generally performed in a constant DC magnetic field. However, in the present magnetic thin film, the anisotropic magnetic field Hk often becomes too large, and in order to obtain high magnetic permeability, it is often necessary to optimize Hk.

As a method for optimizing Hk, it is effective to use film formation in a perpendicular magnetic field, annealing in a rotating magnetic field, or in-plane orthogonalization of the magnetic field directions during film formation in a DC magnetic field and annealing in a DC magnetic field.

In the case of film formation in an orthogonal magnetic field, it is possible to generate a magnetic field with a coil and alternately apply a current. When a permanent magnet is used, it is possible to rotate the cathode by 90 °.

Further, in order to obtain excellent magnetic characteristics, it is necessary to remove fine particles and hydroxides in the plating bath by continuous filtering. As for the degree of filtration, when the capacity of the plating bath is V, the filtration flow rate is preferably V × 0.1 l / min or more. The filter mesh depends on the application, but is 0.2μ especially when forming a film in a fine resist pattern.
m or less is preferable.

The anode is preferably insoluble TiPt or ferrite electrode from the viewpoint of removing fine particles. However, since an oxidation reaction occurs at the anode, it is desirable to separate it from the cathode part by an ion exchange membrane, for example.

The current density during film formation may be selected in the range of 0.01 A / dm ² to 5 A / dm ² according to the purpose. In addition to direct current, it is also possible to use an alternating current type that performs pulse electrolysis and cathode dissolution. Zero voltage and voltage V especially in pulse electrolysis
By applying a plurality of three or more kinds of voltages such as 1, V2 and the like, it is possible to make a large difference in the eutectoid amount of Rh to form a multilayer film structure. It is important that the Rh substitution reaction occurs at the zero potential and the Rh film is formed.

Further, instead of changing the voltage applied from the outside, a shielding plate having slits or holes is placed near the cathode, and by moving this, the portion where the current density is locally concentrated due to the slit portion is removed. The multi-layering can be realized by using a composition different from that of the other low current density portions.

The multi-layered film may be used as it is, but it is also possible to use it as a uniform composition film by utilizing the diffusion effect by heat treatment or the like.

As the solvent for the plating bath of the present invention, non-aqueous solvents such as methyl alcohol, ethyl alcohol, propylene carbide and molten salt can be used in addition to ordinary water.

[0053]

EXAMPLES The present invention will be described in more detail below by showing specific examples of the present invention.

Example 1 A substrate in which 50 A of titanium and 500 A of permalloy were formed on a Corning 7059 glass by a sputtering method was used. 3 in 1N-hydrochloric acid (normal temperature) as a pretreatment for plating
After immersion for 0 second and washing with water, a magnetic film was formed under the following plating conditions.

Plating bath composition (in 1 liter) Cobalt sulphate 0.1 mol Cobalt chloride 0.1 mol Iron sulphate (divalent) 0.01 mol Ammonium chloride 10 g Boric acid 40 g 1,3,6-Naphthalene trisulfonate trisodium salt See Table 1 Propagyl alcohol 0.05 ml Rhodium chloride trihydrate See Table 1

[0056]

[Table 1]

The plating bath temperature was 40 ° C., the plating bath pH was 2.8, the current density was 1 A / dm ² , the plating time was 5 minutes, and electroplating was performed while applying a DC magnetic field of 600 Oe.

The thickness of the sample was 1 μm. The compositions of these samples are shown in Table 1. For the analysis, a fluorescent X-ray analyzer, ICP and CS meter were used. In Table 1, Fe, R
Although the contents of h and S are shown, the balance is Co.

The following measurements were performed on each sample.
The results are shown in Table 2.

[0060]

[Table 2]

(Coercive force Hc) Measured at 60 Hz with an AC BH tracer.

(Saturation magnetic flux density Bs) Measured by VSM.

(Natural Electrode Potential) Using a silver / silver chloride electrode as a reference electrode, measurement was carried out in a 0.01N-KCl solution at room temperature.

Example 2 The following plating bath was used to prepare the samples shown in Table 3 below.

Plating bath composition (in 1 liter) Cobalt sulfamate 0.5 mol Iron sulfamate See Table 3 Ammonium chloride 10 g Boric acid 40 g 1,3,6-Naphthalenetrisulfonate trisodium 60 g Propagyl alcohol 0.05 ml Rhodium chloride 3 Water salt 0.1 g Plating bath temperature is 40 ° C., pH of plating bath is 2.8, current density is 5 minutes under the conditions shown in Table 5, and 6
A DC magnetic field of 00 Oe was applied for 5 seconds and 15 seconds in the directions orthogonal to each other in the plane.

The sample thus obtained was evaluated in the same manner as in Example 1. The results are shown in Tables 3 and 4.

[0067]

[Table 3]

[0068]

[Table 4]

From the results of the above examples, the effect of the present invention is clear. That is, according to the present invention, a magnetic thin film having low Hc and high corrosion resistance can be easily obtained.

[0070]

According to the present invention, a magnetic thin film having low Hc and high corrosion resistance can be easily obtained. Moreover, high productivity can be obtained due to the plating method.

Claims (2)

[Claims] 1. R, which contains Co, Fe and Rh as main components,
The content of h is 1 to 8% by weight and the content of S is 500 to
A magnetic plating thin film, which is 2000 ppm. 2. A film formed by a wet plating method, which has a cobalt ion concentration of 0.05 to 5 mol / l, an iron ion concentration of 0.001 to 5 mol / l, and a pH of 1.0 to 4.0. A method for producing a magnetic thin film, characterized in that a low molecular weight organic compound containing sulfur is dissolved in a bath.