JPH04196402A - Soft magnetic thin film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention can be used for magnetic head materials, sensor materials, or magnetic core materials for transformers, choke coils, supersaturation reactors, noise filters, etc. that exhibit good magnetic properties. The invention relates to soft magnetic thin films.

<Conventional technology> For example, in the field of magnetic recording, the coercive force of recording media is increasing in order to achieve high recording densities, and in order to fully utilize this characteristic, thin film heads and metal-in-gap type heads are being developed. The soft magnetic thin film used in magnetic heads such as
It is necessary to have high saturation magnetic flux density and high magnetic permeability.

In this case, the magnetostriction is preferably in the range of -IXIO-6 to 1x10-6.

There is also a need to be able to industrially produce it in large quantities at low cost.

This also applies to soft magnetic thin films other than magnetic heads.

Conventionally, soft magnetic thin films for such purposes have been produced by vacuum film forming methods such as sputtering or electroplating methods, and their composition is generally permalloy or the like.

<Problem to be solved by the invention> However, permalloy, which has conventionally been widely used as a soft magnetic thin film, has -1X
The range of the Fe/N-5 amount ratio of magnetostriction in the range of I CM' to I X I CM' (7) is narrow.

When a film is formed by sputtering, mass productivity is poor, and it is difficult to uniformly form a film over a large area.

Further, when a film is formed by electroplating, there are problems such as oxidation of divalent iron and compositional deviation due to current distribution.

Furthermore, regarding the permalloy film produced by the electroless method, Kojima et al.
13 1984), Okichina et al. (Metal Surface Technology Association Vol. 7)
Although it has been proposed in the Abstracts of the 4th Lecture Conference 16A-11), it is still difficult to control the composition, and it is difficult to obtain a narrow Fe/Ni composition range that exhibits good characteristics with good reproducibility.

In addition, electroless plated Co--P thin films have been studied by Kojima et al., but the coercive force Hc is only reduced to 50e at most, and sufficient characteristics have not been obtained.

An object of the present invention is to provide an electroless plated soft magnetic thin film that exhibits good soft magnetic properties, is easy to manage and control, and has high film uniformity (and excellent productivity).

Means for Solving the Problems> These objects are achieved by the following inventions (1) to (11).

(1) Contains Co, Fe and B, Fe ion/C
The film is formed from a plating bath with a molar ratio of o ions of 0.005 to 0.3, contains 1 to 7 at% of Fe, and -
A soft magnetic thin film characterized by having a magnetostriction of 1×10 −6 to +1×10 −6 .

(2) The soft magnetic thin film according to (1) above, wherein the content of B is 1 to 7 at%.

(3) The coercive force is 10e or less (1) or (
2) The soft magnetic thin film described in item 2).

(4) The plating bath contains complexing agent ions at 0.05 mol/
The soft magnetic thin film according to any one of (1) to 3) above, containing 1 or more.

(5) The complexing agent ion is a tartrate ion (4)
) The soft magnetic thin film described in ).

(6) The soft magnetic thin film according to any one of (1) to 5) above, wherein the plating bath contains dimethylamine borane.

(7) The plating bath contains an ammonia source of 0.1 mol/l
The soft magnetic thin film according to any one of (1) to 6) above, containing the above.

(8) The soft magnetic thin film according to (7) above, wherein the ammonia source is ammonium sulfate.

(9) The soft magnetic thin film according to any one of (1) to 8) above, which is formed by electroless plating.

(10) The soft magnetic thin film according to (9) above, wherein the film formation is performed while applying magnetic fields from different directions alternately or while applying a rotating magnetic field.

(l l) The soft magnetic thin film according to (9) or (10) above, wherein the film formation is performed by using electroless plating in combination with electrolytic plating and/or AC electrolytic plating.

Effect〉 The soft magnetic thin film of the present invention is a Co-Fe-B quinary system.

Since it is manufactured using a predetermined electroless plating bath, it is excellent in mass production and there is no problem in film uniformity.

In this case, in the present invention, a boron-containing compound such as dimethylamine borane is used as a reducing agent for Co-Fe electroless plating, and B is contained as a third element.
By mixing this B, excellent magnetic properties that could not be obtained with the Co--P systems that have been studied in the past can be obtained.

The present inventor has made many studies and considerations regarding this cause, but unfortunately no clear basis has been obtained yet.

However, it is clear that the important point is that the precipitated particles are extremely fine.

In particular, films with a structure similar to amorphous have excellent magnetic properties.

In this case, the amorphous-like structure has a very fine structure that gives a broad beak according to X-ray diffraction, and it is considered that each fine structure is a crystal.

In other words, it refers to a structure that can be called an amorphous-like structure based on the X-ray diffraction pattern.

Note that CO□B (33,3at
%, i.e. 8.41wt%B) and CoB (50at%
, that is, 15.51wt%B), etc. are known, but
The soft magnetic thin film of the present invention is different from these.

Co-Fe-B11 of the present invention has a B content of about 7 at % at most, and is not a completely homogeneous film.

In other words, it is made up of a fine structure consisting of parts that can be called a B-rich phase and a B-poor phase.

According to the electroless plating method, such a complicated microstructure can be easily formed with good reproducibility.

Furthermore, a major point of the present invention is that a small amount of iron ions are allowed to coexist in the plating bath.

In order to obtain sufficient properties as a soft magnetic thin film, especially sufficient magnetic permeability, the magnetostriction should be near zero, that is, −I
-' to I X 10-'.

Conventionally, this was achieved by setting the composition to around 90Co-10Fe.

However, this required a large amount of iron ions to coexist during plating.

Although Fe ions are preferably present in the solution in a divalent state during plating, they are easily oxidized and become trivalent. This made management extremely difficult.

In the present invention, due to the coexistence of a small amount of iron ions, the magnetostriction of the formed soft magnetic film becomes almost zero.

Even though the film contains at most 1 to 7 at% iron, the magnetostriction is small.

Although the cause of this is not clear, it is presumed that iron is segregated locally in the microstructure.

Specific composition> Hereinafter, the specific configuration of the present invention will be explained in detail.

The soft magnetic thin film of the present invention contains Fe, Co and B. The Fe content in the film is 1 to 7 at%.

If it is less than lat%, the magnetostriction becomes large (becomes large), and if it exceeds 7at%, the coercive force Hc increases and the magnetostriction also becomes large.

In this case, Fe is preferably 1.5 to 6 at%.

The B content in the film is IQ7at%, more preferably 3
~6at%.

When the B content exceeds 7 at%, Co-B alloy or C
If the o-Fe-B alloy becomes the main component, and if the B content is low, Co or Co-Fe crystals become the main component, and neither of them can form a fine structure, making it impossible to obtain desirable properties.

The remainder of the soft magnetic thin film is formed essentially of CO, but N
i%W, Mo, P, Cu, Zn, Sn, S, Ca, etc.
More than one species may be contained in a total amount of 5 at% or less.

Moreover, if the film thickness is 0.05- or more, it becomes a homogeneous film.

For this reason, the film thickness is usually about 0.05 to 10 -.

However, as the film thickness increases, it tends to form a giant crystal structure (
Become. For this reason, it is preferable that the film thickness is 0.05 to 5.

If a thicker film thickness is desired, the layers can be stacked with an intermediate layer such as another electroless plated layer interposed therebetween.

Other electroless plated layers include non-magnetic layers such as nickel-phosphorous layers and Cu layers.

That is, preferably a nonmagnetic layer is provided as an intermediate layer,
It is also possible to form Co-Fe-BM above and below it. Furthermore, it is possible to increase the number of intermediate layers and laminate many layers.

This is useful when the structure of the Co--Fe--H film changes depending on its thickness, by stacking several thin layers to obtain the desired thickness.

The intermediate layer may be a magnetic layer, but a non-magnetic plated layer is particularly preferred.

When laminated in this way, the Co-Fe-B layer should be about 0.05 to 2 layers, as described above, and the middle layer should be about 5 to 3 layers.
The film thickness is approximately 0%.

Note that the NLP used as the intermediate layer is P5 to 18% by weight.
It is preferable to have a composition of approximately゛In addition, the intermediate layer may be CoP or CoN'iP with a thickness of 0.01μ or less.

It is preferable that such an electroless plated soft magnetic thin film has an amorphous-like structure as described above.

For example, it has a microstructure that is considered to be crystalline with an average grain size assumed to be about 100 Å or less.

The soft magnetic thin film of the present invention is 1 Oe or less, particularly 0, '1
~0.90e coercive force and 10000~20000G
It shows a saturation magnetic flux density of , and a squareness ratio of 0.8 to 1.00.

And -1XIO''6~+lX10-', especially -0,
5×10−” to +0.5×−10−′ (7) Magnetostrictive.

As a result, it has a magnetic permeability of 1000 or more, particularly 1000 to 2000, at 5 M and Hz, for example.

The substrate supporting such a soft magnetic thin film may be any known substrate (the thin film may be peeled off from the substrate if necessary).

Such a soft magnetic thin film is produced by electroless plating.

The substrate used can be previously subjected to a known electroless plating activation process.

As the Co source of the electroless plating bath used, any known Co source such as cobalt sulfate or cobalt chloride can be used, and these are used at about 0.05 to 3.0 mol/P.

As the Fe source, any known Fe sources such as cobalt sulfate and cobalt chloride can be used.

However, the amount of Fe source used must be such that the molar ratio of Fe ions/Co ions is 0.005 to 0.3.

In this manner, by controlling the amount of Fe ions/Co ions in the bath, the Fe/Co ratio in the film is controlled and a fine structure is imparted.

In this case, the Fe ion/Co ion molar ratio is 0.
It is preferable that it is 01-0.2.

Source B also serves as a reducing agent, and dimethylamine borane, sodium borohydride, etc. can be suitably used. Among these, dimethylamine borane is most suitable as the B source.

The concentration thereof is approximately 0.01 to 0.10 mol/l.

Furthermore, it is preferable to add a complexing agent such as a salt of tartaric acid, succinic acid, malonic acid, malic acid, gluconic acid, etc. to the solution.

Particularly suitable complexing agents are tartaric acid or its salts, especially sodium tartrate.

and the amount of complexing agent ions is 0.05 mol/i or more,
In particular, 0.1 to 1 molha is suitable.

As a result, a fine structure is stably formed, soft magnetic properties are improved, and He is reduced.

Furthermore, it is preferable that an ammonia source is contained in the liquid.

Examples of the ammonia source include ammonium sulfate and ammonium chloride.

This also stabilizes the microstructure, improves the soft magnetic properties, and particularly reduces Hc.

The ammonia source is 0.1 mol/E or more, especially 0.2 to 0
．． The content is preferably 4 mol/1.

In addition, a buffer agent such as oxalic acid may be added to the bath if necessary.

The p)l of the bath is preferably 7 to 10.

For pH adjustment, sodium hydroxide or the like may be used to keep the amount of ammonium ions constant.

If the pH is too low, the precipitation rate will be slow; if the pH is too high, the bath will be unstable and prone to separation.

The bath temperature for plating is about 40-75℃, especially 60-70℃
is preferred.

If the bath temperature is too high, the bath will be unstable and will easily separate, and if it is too low, the precipitation rate will be slow.

Moreover, it is preferable for the plating time to be 2 to 60 minutes, particularly 10 to 20 minutes, to achieve a predetermined film thickness.

When a thick soft magnetic film is required, it is also possible to obtain a film of the desired thickness in a short time by using electrolytic plating or activating electroless deposition by alternating current electrolysis.

Furthermore, these electrolytic techniques can also be performed only during a certain period of time during plating.

For example, after initially forming a film to a thickness of 0.5 microns using only electrolysis, it is possible to use electrolysis in combination, or it is possible to repeat electrolytic plating for 5 minutes every 5 minutes of electroless plating. .

In this case, the current density of the electrolytic plating used in combination is 0.5 to 3
A/dm", and AC electrolysis is 0, 1
Frequency 1 to 100 at a current density of “-I A/dm”
0) Approximately 1z.

Furthermore, if it is desired to impart appropriate magnetic anisotropy, it is effective to apply an orthogonal magnetic field during plating film formation.

For example, this can be achieved by applying a magnetic field strength of 8000e in the easy axis direction for 10 seconds, then applying it in the hard axis direction at 2000e for 5 seconds, and repeating this during film formation.

Alternatively, the same effect can be obtained by rotating the plated substrate in a DC magnetic field.

In this way, by alternately applying magnetic fields from different directions or forming a film while applying a rotating magnetic field, appropriate magnetic anisotropy can be imparted.

In this case, the required magnetic field applied in the in-plane easy axis direction is about 50 to 10,000 e, and the required magnetic field applied in the in-plane hard axis direction is about 50 to 10,000 e.

The period of application of such an alternating or rotating magnetic field may generally be about 0.1 to 200 seconds.

Note that when a NiP layer is provided as an intermediate layer, sodium hypophosphite or the like may be used as the P source;
As the i-source, nickel sulfate, nickel chloride, etc. are possible.

In addition, various intermediate layers are formed by known methods.

The electroless plated soft magnetic film of the present invention produced in this manner can be used as a magnetic pole material for a thin film magnetic head, a soft magnetic thin film for a metal-in-gap magnetic head, a soft magnetic underlayer for a perpendicular magnetic recording medium, a magnetic sensor, distance sensor, direction sensor,
Sensor thin films such as tilt sensors, thin film magnetic cores such as transformers, choke coils, noise filters, supersaturation reactors, etc.
It is useful as a thin film for magnetic shielding, etc.

<Examples> Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Examples 1 to 6, Comparative Example 1.2 A 50 μm thick polyimide film sputtered with 300 rhinoceros Au was prepared.

This film was degreased by immersion in a 5% sodium hydroxide solution (room temperature) for 30 seconds, washed with water, and then activated by immersion in a 10% hydrochloric acid solution (room temperature) for 30 seconds.

This substrate was subjected to electroless plating for 10 minutes in a plating bath shown in Table 1 below (Example 1.2).

In addition, a film was formed in the plating bath shown in Table 1 below using a 0.1 mm glass substrate (Corning product number 7059) sputtered with 500 Cu particles and activated with 10% hydrochloric acid at room temperature for 30 seconds. (Example 3.4).

For magnetostriction measurement, a 0.1 mm thick glass substrate (Matsunami Glass Industry No. 0) sputtered with Au and Cu in the same manner was used, and a film was formed using the same method.

Further, as a comparative example, film formation was performed for 10 minutes using a plating bath shown in Table 1 below using the same plated substrate as in the example.

All films were formed by plating in an alternating orthogonal magnetic field.

That is, a direct current magnetic field was obtained by pairing two permanent magnets and facing each other. Then, by changing the position during plating, this was made into an orthogonal magnetic field.

The easy axis direction is 6000e and the hard axis direction is 3000e.
The magnetic field strength was set to e, and the period was set to 20 seconds.

Further, Example 5 was prepared by using a TiPt anode as an anode during plating under the same conditions as in Example 1, and using DC electrolysis at 0.5 A/d.

Furthermore, Example 6 was obtained by performing AC electrolysis under the same conditions as in Example 4.

This AC electrolysis condition is such that positive and negative electrolysis with a current value of 0.5 A/da'' is applied for a time of 50 m5 each. Since the positive and negative values are the same, the amount of precipitation due to electrolysis is considered to be zero.

The film thickness, magnetic properties, magnetostriction, and magnetic permeability of each magnetic film thus obtained were measured.

For the measurements, a step meter, VSM, optical lever method, and figure-eight coil method were used, respectively.

Further, after dissolving in nitric acid, plasma emission spectrometry was performed to quantify the boron content and iron content in the film.

The results are shown in Table 2.

From the results shown in Table 2, it can be seen that the soft magnetic thin film of the present invention exhibits good magnetic properties.

<Effects of the Invention> According to the present invention, a soft magnetic thin film is realized which exhibits extremely good soft magnetic properties, has high film uniformity even when deposited over a large area, and is highly mass-producible.

Applicant: Educational corporation: Waseda University Same TDT-K Co., Ltd.

Claims (1)

[Claims] (1) Contains Co, Fe and B, Fe ion/Co
The film is formed from a plating bath with an ion molar ratio of 0.005 to 0.3, contains 1 to 7 at% of Fe, and -1
A soft magnetic thin film characterized by having a magnetostriction of ×10^-^6 to +1x10^-^5. (2) The soft magnetic thin film according to claim 1, wherein the content of B is 1 to 7 at%. (3) The soft magnetic thin film according to claim 1 or 2, having a coercive force of 1 Oe or less. (4) The soft magnetic thin film according to any one of claims 1 to 3, wherein the plating bath contains complexing agent ions of 0.05 mol/l or more. (5) Claim 4, wherein the complexing agent ion is a tartrate ion.
Soft magnetic thin film described in . (6) The soft magnetic thin film according to any one of claims 1 to 5, wherein the plating bath contains dimethylamine borane. (7) The plating bath contains an ammonia source of 0.1 mol/l
The soft magnetic thin film according to any one of claims 1 to 6, which contains the above. (8) The soft magnetic thin film according to claim 7, wherein the ammonia source is ammonium sulfate. (9) The soft magnetic thin film according to any one of claims 1 to 8, which is formed by electroless plating. (10) The soft magnetic thin film according to claim 9, wherein the film formation is performed while applying magnetic fields from different directions alternately or while applying a rotating magnetic field. (11) The soft magnetic thin film according to claim 9 or 10, wherein the film formation is performed using electroless plating, electrolytic plating and/or alternating current electrolytic plating.