JPS61171114A - Manufacture of soft magnetic thin film - Google Patents

Abstract

PURPOSE:To obtain thin film of soft magnetic material which presents small irregularity of characteristics and shows little deterioration of the frequency characteristics and the Barkhausen noise even in the curved path of magnetic flux, by forming two- layered structure of the films of soft magnetic material which sandwiches a non- magnetic thin film, and annealing this element in the magnetic field generated by flowing the bias current. CONSTITUTION:When the bias current IB is supplied along the horseshoe pattern from the terminals 5 and 6, the bias current IB branches into the three paths corresponding to the electric resistance of the non-magnetic film 2, the first and the second thin films of soft magnetic material 1 and 3. Each of them generates the magnetic field perpendicular to the bias current IB. One part of the magnetic field penetrates the first and the second thin films of soft magnetic material 1 and 3 and magnetizes them. The directions of each magnetization M are inverse with each other and perpendicular to the bias current IB. In order to make the magnetization M in the direction of the magnetic field generated by the bias current IB easy to saturate, the thickness of the non-magnetic film 2 is so set that the first thin film 1 and the second thin film 2 have the magnetostatic coupling to reduce the demagnetization caused by their forms. Thus, annealing is performed under the condition of predetermined time and temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing a soft magnetic thin film used in magnetic transducers such as magnetic sensors and magnetic heads.

(Prior Art and its Problems) Conventionally, various magnetic transducers using soft magnetic thin films have been disclosed for writing and reading magnetic information to and from magnetic storage media such as magnetic tapes and magnetic disks. For example, a soft magnetic thin film as the magnetic core of an inductive magnetic head is
The purpose is to effectively converge the signal magnetic flux from the magnetic storage medium and link it with the coil, and there is no need for a soft magnetic thin film as a magnetic shield used in magnetoresistive magnetic heads, also known as flux-responsive magnetic heads. The purpose is to improve the reproduction resolution by reducing the magnetic field.

For these purposes, soft magnetic thin films are required to have high magnetic permeability and good frequency characteristics. Therefore, soft magnetic thin films are generally given uniaxial anisotropy so that the signal magnetic flux is guided parallel to the axis of hard magnetization.
The shape and positional relationship with the magnetic storage medium are optimally designed.

On the other hand, in a magnetic head designed to introduce signal magnetic flux in the direction of the easy axis of magnetization of a soft magnetic thin film, high magnetic permeability can be obtained at low frequencies, but as the frequency of signal magnetic flux increases, the permeability increases. The magnetic flux sharply decreases, and as a result, the signal magnetic flux interlinking with the coil also decreases, resulting in a sharp attenuation of the reproduction output.

Furthermore, Barkhausen noise and the like associated with the movement of domain walls are also observed.

As mentioned above, in a magnetic transducer using a soft magnetic thin film, uniaxial anisotropy is imparted to the soft magnetic thin film, and signal magnetic flux is directed parallel to the axis of hard magnetization (that is, in a direction orthogonal to the axis of easy magnetization). It is an essential condition to obtain good properties.

Conventionally, methods for imparting uniaxial anisotropy to magnetic transducers include forming a soft magnetic thin film on a substrate in a uniform magnetic field using methods such as vacuum evaporation, sputtering, and electrodeposition. Alternatively, after film formation, uniaxial anisotropy has been formed by annealing in a uniform magnetic field to make the axis of easy magnetization substantially parallel to the magnetic field. Further, in order to function as a magnetic transducer, the soft magnetic thin film formed on the substrate is processed by photolithography into a magnetic core pattern having a predetermined arrangement with the axis of easy magnetization. Furthermore,
After going through the process of forming and processing other functional parts such as coils,
Completed as a magnetic transducer.

However, in the above manufacturing process, the arrangement relationship between the magnetic core pattern and the axis of easy magnetization is not as set, and variations occur. This is because the easy axis direction of magnetization is not necessarily uniform over the entire surface of the substrate due to non-uniform magnetic field distribution and film quality when imparting -axis anisotropy. In addition, misalignment during processing into a magnetic core pattern is also reflected.

This results in variations in the characteristics of the magnetic transducer and a reduction in manufacturing yield.

Furthermore, the path of the signal magnetic flux and the axis of hard magnetization are not necessarily parallel throughout the entire magnetic core pattern, that is, a magnetic head with a curved path of magnetic flux may be It is disclosed in lecture number 17aB-10. Such a magnetic head has a closed magnetic path structure in which signal magnetic flux flowing from a magnetic storage medium is routed through the film surface from one end of a soft magnetic thin film and returned to the magnetic storage medium from the other end. In this type of magnetic transducer, the single magnetic flux path of the signal is curved, so in the method of manufacturing a soft magnetic thin film using the uniform magnetic field described above, there is a region where the axis of easy magnetization coincides with the direction of the signal magnetic flux. However, this results in deterioration of frequency characteristics and reduction in reproduction efficiency.

(Object of the Invention) The present invention discloses a method for manufacturing a soft magnetic thin film that solves the above-mentioned conventional drawbacks and has less variation in characteristics, as well as less deterioration of frequency characteristics and Barkhausen noise even with a curved magnetic flux path. It's about doing.

(Structure of the Invention) According to the present invention, a step of laminating a first and a second soft magnetic film through a non-magnetic thin film at an interval that allows magnetostatic coupling to occur; A method for manufacturing a soft magnetic thin film, comprising the steps of supplying a bias current to at least one of the soft magnetic thin films, and annealing the soft magnetic thin film in a magnetic field generated by the bias current. can get.

(Detailed Description of Configuration) The present invention solves the problems of the prior art by the above-mentioned manufacturing method. That is, in the present invention, a bias current is applied to a laminate having a structure in which a first soft magnetic thin film, a nonmagnetic conductive layer, and a second soft magnetic thin film are laminated in sequence, and which is processed into a predetermined pattern. , by using the magnetic field generated by the bias current to make the magnetization of at least one of the first or second soft magnetic thin films perpendicular to the bias current, and performing an annealing treatment in this state, the direction of the bias current can be changed. It is possible to generate uniaxial anisotropy having a hard axis of magnetization. Therefore, by aligning the path of the signal magnetic flux with the direction of the bias current, a soft magnetic thin film with less deterioration in frequency characteristics can be obtained.

Furthermore, since the direction of the bias current can be uniquely determined by the pattern of the soft magnetic thin film, the direction of the -axis anisotropy is uniquely determined according to the pattern of the soft magnetic thin film. This eliminates variations in characteristics that occur when soft magnetic thin film patterns are manufactured in bulk on the same substrate using photolithography technology.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic perspective view showing a configuration example of a soft magnetic thin film suitable for applying the present invention. are sequentially laminated to form a magnetic core with a horseshoe-shaped curved pattern.

The first and second soft magnetic thin films 1 and 3 are made of, for example, permalloy, amorphous soft magnetic material (e.g. Co-Zr,
Co-metal amorphous alloys such as Co-Ta and Co-Ti), sendust alloys, etc. are suitable, and non-magnetic thin films 2
People also use OB, insulators such as 5in1 or Ti,
A conductive material such as Ta is suitable.

Further, terminals 5 and 6 for supplying bias current IB are connected to both ends of the ringing hoof pattern.

In such a configuration, bias current IB is applied to terminals 5 and 6.
When applied along a more horseshoe pattern, the bias current 1. is divided according to the electrical resistance of the non-magnetic thin film 2 and the first and second soft magnetic thin films 1 and 3, and the bias current 1. A magnetic field is generated in the direction orthogonal to the A part of the magnetic field passes through the film planes of the first and second soft magnetic thin films 1 and 3,
The respective magnetizations M are in opposite directions, and the bias current is 1. It is excited in the direction perpendicular to . In addition, bias DC 1
In order to make it easier for the magnetization M to saturate in the direction of the excitation magnetic field generated by °, I! The thickness of the non-magnetic thin film 2 is set so that the first soft magnetic thin film l and the second soft magnetic thin film 3 perform magnetostatic coupling and reduce the shape demagnetizing field of each soft magnetic thin film.

In this state, an annealing treatment is performed under predetermined time and temperature conditions. The conditions for the annealing treatment are selected depending on the materials of the first and second soft magnetic films 1 and 3. For example, if an amorphous soft magnetic material is used, it is below its crystallization temperature (400-500°C), and if it is a polycrystalline material such as permalloy or sendust alloy, it is below the temperature at which grain growth does not occur (300-400°C). An annealing temperature of .

Annealing is performed at a bias current of 1. It may also be set using the gel heat generated by the supply of . Further, it is preferable that the annealing treatment be performed in a vacuum, hydrogen or nitrogen gas, or after an insulating protective film has been deposited. These prevent deterioration of magnetic properties due to oxidation of the first and second soft magnetic thin films 1 and 3.

As a result of the above annealing process, the bias current I.

Even without supplying the first and second soft magnetic thin films 1 and 3
The magnetization M of is fixed in the direction perpendicular to the path of the bias current III. That is, the bias current 1. The axis of easy magnetization is 10 in the direction perpendicular to the path of , and the bias current I
Uniaxial anisotropy having a hard magnetization axis in a direction parallel to n is generated.

Note that, as described above, the first and second soft magnetic thin films 1 and 3 are laminated for the purpose of reducing the shape demagnetizing field in the direction orthogonal to the bias current.

Therefore, either one of the first and second soft magnetic thin films 1 and 3 may have only the function of reducing the shape demagnetizing field of the other. In this case, the materials, film thicknesses, and dimensions of the first and second soft magnetic thin films 1 and 3, as well as the bias current r
An advantage arises that selection of a becomes easy. Further, in order to perform a good operation as a magnetic core, it is desirable to remove the soft magnetic thin film provided only for the purpose of reducing the shape demagnetizing field by etching or the like after the annealing process is completed.

In the magnetic core of FIG. 1 manufactured as described above, the terminals 5 and 6 are arranged so that the signal magnetic flux from the magnetic storage medium flows in and out from one end of the horseshoe pattern to the other end. For example, since the path of the signal magnetic flux is always perpendicular to the easy magnetization axes E and A, Barkhausen noise and deterioration of frequency characteristics due to irregular movement of the domain wall are eliminated. Although the method for manufacturing a magnetic thin film pattern has been described, the present invention is also suitable for manufacturing a plurality of soft magnetic thin film patterns on a substrate at once. FIG. 2 is a plan view for explaining such an example. In FIG. 2, a plurality of soft magnetic thin film patterns 7 are formed on the base.
By connecting these in parallel, the bias current 1. The soft magnetic thin film pattern 7 to which the terminals 5 and 6 for supplying the
It has a structure in which a soft magnetic thin film of , a nonmagnetic thin film, and a soft magnetic thin film of PI3 are sequentially laminated. Furthermore, the soft magnetic thin film pattern 7 and the terminals 5 and 6 are formed all at once using the IJ lithography technique. Therefore, the material constituting the terminals 5 and 6 may be the same as that of the soft magnetic thin film pattern 7.

In such a configuration, bias currents 1. is divided into a plurality of soft magnetic thin film patterns 7,
A magnetic field is generated that passes through the plane of the soft magnetic thin film pattern 7 in a direction perpendicular to the bias current IB that is divided into respective branches.

Hereinafter, as explained using FIG. 1, the magnetic field excites the magnetization of at least one of the first and second soft magnetic thin films in the direction of the magnetic field. In this state, by annealing at a time and temperature condition depending on the materials of the first and second soft magnetic thin films, a uniaxial magnet having easy magnetization axes E and A in a direction orthogonal to the direction in which the bias current is supplied is formed. A direction is generated. This axis of easy magnetization B. The direction of the person is uniquely determined by the direction of the bias current IB, that is, the shape of the soft magnetic thin film pattern 7 and the terminals 5 and 6, regardless of the position of the soft magnetic thin film pattern 7 on the base body. This means that a large number of soft magnetic thin film patterns with uniform magnetic properties and little variation can be obtained on the substrate 4.In addition, in FIG. 2, a plurality of soft magnetic thin film patterns 7 are shaped like short fences. However, a curved pattern as shown in FIG. 1 may also be used. Further, although the soft magnetic thin film patterns are connected in parallel, they may be connected in series or in a combination thereof.

Furthermore, in FIG. 2, in order to complete the soft magnetic thin film pattern, terminals 5 and 6 may be removed by etching or directly mechanically cut.

The above explanation has been about the method of forming a predetermined soft magnetic thin film pattern and then supplying a bias current to anneal it. A desired soft magnetic thin film pattern may be formed after annealing by supplying a bias current according to the present invention. This method is useful when the pattern width in the direction perpendicular to the bias current path of the required soft magnetic thin film pattern is extremely small and the shape demagnetizing field cannot be ignored, or when the pattern width of the pattern J
This is effective when the width of the bias current changes along with the path of the bias current and the direction of the bias current becomes non-uniform.

In other words, by reducing the non-uniformity of the shape demagnetizing field and bias current direction by using a large pattern formed in advance, and in this state, by uniformly generating uniaxial anisotropy using the molding method of the present invention, the desired soft magnetic properties can be obtained. Even after processing into a thin film pattern, -axis anisotropy can be uniformly imparted.

(Example) Examples of the present invention will be described below by illustrating specific materials and annealing conditions.

In FIG. 1, a first soft magnetic thin film 1 and a second soft magnetic thin film 3 are amorphous soft magnetic films having a composition of 90% Co-10% Ta (both atomic percentages), each having a thickness of 0.5 μm. As the non-magnetic thin film 2, a Ti film with a thickness of 0.05 μm was continuously formed by sputtering. These laminated films were processed into a horseshoe-shaped pattern having a width of 5 μm using photolithography technology, and the edges 5 and 6 were connected.

The temperature of the soft magnetic film thus constructed was raised to 250° C. in a nitrogen gas atmosphere, and 400 m of bias current was supplied from terminals 5 and 6, and this state was maintained for 4 hours. Note that while the bias current In was being supplied, the temperature of the soft magnetic film was set at 250° C., including Joule heat caused by this.

After the above annealing process, terminals 5 and 6 were removed and magnetic domains were observed using the Bitter method. As a result, domain walls were observed throughout the soft magnetic film pattern in a direction perpendicular to the bias current path. It was confirmed that the axis of easy magnetization was generated in a direction perpendicular to the path of the bias current IB.

(Comparative Example) For comparison, we observed the magnetic domains of a soft magnetic film pattern that had exactly the same structure as the above example but had not been subjected to the annealing process according to the present invention. An irregular arrangement of domain walls was observed.

Next, in both the above examples and comparative examples, a coil was formed using photolithography technology so as to surround the horseshoe pattern, and a magnetic transducer was fabricated such that both ends of the horseshoe pattern became input and output ends of the signal magnetic flux. As a result, in the comparative example, although a relatively large signal output was obtained at a signal magnetic field frequency of several hundred kHz or less, it was extremely noisy.
As the signal magnetic field frequency increased, a sharp decrease in signal output was observed. On the other hand, in the example according to the present invention, it was confirmed that the noise was small and a uniform signal output was obtained from low frequencies to high frequencies of 10 MHz or more, and that it had excellent high frequency characteristics.

(Effects of the Invention) As explained above, in the present invention, a soft magnetic thin film is formed into a two-layer structure with a non-magnetic thin film interposed therebetween, and annealing treatment is performed in a magnetic field generated by supplying a bias current to the soft magnetic thin film. Therefore, it is possible to generate uniaxial anisotropy with the axis of hard magnetization in the direction of the bias current. Therefore, by aligning the path of the signal magnetic flux with the direction of the bias current, a soft magnetic thin film with excellent frequency characteristics and less Barkhausen noise can be provided even with a single curve pattern.

Furthermore, since the direction of the -axis anisotropy is determined according to the shape of the soft magnetic thin film, variations in magnetic properties are extremely small when mass-produced at once, making it possible to provide soft magnetic thin films with high yields.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view for explaining an embodiment of the manufacturing method of the present invention, and FIG. 2 is a plan view for explaining an embodiment of another manufacturing method of the present invention. In the figure, 1... first soft magnetic thin film, 2... nonmagnetic thin film, 3...
...Second soft magnetic thin film, 5.6...Terminal, 7...Soft magnetic thin film pattern. Hajime 2nd figure

Claims (1)

[Claims] a step of laminating first and second soft magnetic thin films at intervals that allow magnetostatic coupling via the nonmagnetic thin film;
A soft magnetic thin film characterized by comprising a step of supplying a bias current to at least one of the first and second soft magnetic thin films and annealing the soft magnetic thin film in a magnetic field generated by the bias current. manufacturing method.