JPS5872071A - Thin film magnetic sensor - Google Patents

Abstract

PURPOSE:To obtain a minute magnetic sensor having thickness of several microons-several tens microns, by forming a strip-shaped magnetic thin film, which consists of two layers different in coersive force, on a substrate. CONSTITUTION:Magnetic materials having a composition ratio of Fe:Co:V=35- 52:41-63:1-8 (weight ratio) are used for a soft film 2, and magnetic materials having a composition ratio of Fe:Co:V=25-51:40-63:2-5 (wt%) are used for a hard film 3, and borosilicate glass is used for a substrate 1. The soft film 2 is deposited on the substrate 1 by electron beam vapor-deposition, and the hard film 3 is deposited on the soft film 2. This two-layered film is formed to a shape like a strip by photolithography, and an aqueous ferric chloride solution is used for etching. An SiO2 film is deposited on all of the surface of the strip-staped magnetic thin film by the sputtering method. Al is deposited on all of the surface of the substrate by vacuum depostion to form a coil 5. This device is cut and is made into a chip and is mounted on a reed frame, and Al wires of 25 microns are connected to electrode pads 6 and 6' of the coil and onto the reed frame by wire bonding, and finally, this device is molded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves forming two types of magnetic thin films with different coercive forces over each other by vacuum evaporation, electron beam evaporation, or sputtering evaporation, and then winding a pickup coil around the magnetic thin films or by winding the pickup coil around the magnetic thin films. [This invention relates to a thin film magnetic sensor equipped with a coil made using triso technology.]

That is, F is applied on glass, porcelain, or a silicon (Sl) wafer with a non-magnetic oxide film on its surface.
Two layers of magnetic thin films made from the composition of e-Go-V are stacked with different component ratios, and a pickup coil is wound on top of the layers through an insulating film, or by using thin film photolithography technology. This is a thin film magnetic sensor constructed by installing the created coil and then molding it.

Conventionally, many sensors using semiconductor materials, magnetic materials, etc. have been developed and put into practical use as magnetic sensors that detect the amount of change or change in an external magnetic field. For example, devices using semiconductor materials include Hall elements and FIT elements. These are In5l).

m-v compounds such as CT2LAs, Si or cTe
etc. are mainly used. There are memory elements, magnetoresistive elements, magnetic heads, etc. that use magnetic materials, and permalloy, sendust, Ni-Zn, Mn-Znn fluorite, etc. are used.

Furthermore, in Japanese Patent Application Laid-Open No. 53-137641, a magnetic wire is subjected to mechanical and thermal treatment, and a layer near the surface of the magnetic wire (
A magnetic device is disclosed in which the magnetic properties of the second magnetic part (second magnetic part) are changed to have a larger coercive force than the internal (first magnetic part), and a wire is wound around this. This is because the coercive force of the second magnetic portion is greater than the coercive force of the first magnetic portion. That is, it has a structure in which a magnetic portion with a small coercive force is covered in the circumferential direction by a magnetic portion with a large coercive force.

This magnetic device measures the magnitude of an external magnetic field, for example.

When changing the direction in the longitudinal direction of the wire, the part with a large coercive force interacts magnetically with the part with a small coercive force, so the magnetization direction of both is the same direction and opposite to the external magnetic field. In this case, the magnetization reversal of the portion with a small coercive force occurs in an external magnetic field that is greater than the coercive force Hc1 and smaller than the coercive force ■c2 of the portion with a large coercive force. Still, the magnetization direction of the external magnetic field and the part with large coercive force are the same,
If only the magnetization direction of the part with a small coercive force is opposite to those, the part with a large coercive force will help the magnetization reversal of the part with a small coercive force, and a magnetic field of about Hc1 will cause the magnetization to change more rapidly. Suddenly, magnetization reversal occurs in areas with low coercive force. Magnetization reversal due to the influence of an external magnetic field in these parts with low coercive force causes an electromagnetic induction phenomenon, and a current is generated in the pickup coil wound on a wire, and a small pulse voltage is applied to both ends of the coil in the former case, and a small pulse voltage in the latter case. A large pulse voltage can be obtained. The magnitude of this pulse voltage,
The steepness is much better than that made of a single magnetic material. Furthermore, in the case of a pickup coil made of a single magnetic material, the width of the pulse generated in the pickup coil depends on the speed of change of the external magnetic field, and a constant pulse voltage cannot be obtained; the slower the change, the wider the change, and the faster the change, the narrower the pulse voltage becomes.

In this way, the one published in Japanese Patent Application Laid-Open No. 53-137641 is
Although magnetic devices have excellent characteristics, their manufacturing methods are complicated, and it is difficult to manufacture them with a high yield. Also, although a thin wire with a diameter of 260 microns is used, it would be very difficult or even impossible to create smaller devices. Furthermore, when creating a matrix by arranging many such devices, or creating a magnetic sensor that detects minute magnetic fields,
It is not possible to create magnetic devices suitable for this.

The present invention seeks to significantly solve these problems and difficulties. That is, by forming a thin film structure, (1) it is possible to create a minute magnetic sensor with a size of several microns to several tens of microns.

? ) Since the integration density can be increased, a matrix consisting of a large number of sensors can be formed at a high density.

(3) Manufacturing becomes easier.

(4) It is highly suitable for mass production.

An excellent 1A koshigami such as the following can be obtained.

An embodiment of the present invention will be described below with reference to the drawings. Figures 2 and 3 show the configuration of an embodiment of the present invention. The thin film magnetic sensor of this embodiment uses Fe-C0-■. Two layers of magnetic thin films 2 and 3 having different coercive forces are deposited on the substrate 1 of FIG. 2 by vacuum evaporation, electron beam evaporation, or sputtering evaporation.

In order to vary the coercive force, the component ratio of the composition of F6-GO-V is changed. A partial investigation of the relationship between the composition and coercive force of the F, -co-v magnetic material revealed that it was roughly as shown in Figure 1. In this region, the amount of V added most effectively influences the coercive force. Therefore, the structure consists of two layers of magnetic thin films with different coercive forces, that is, magnetic thin film 2 with a small coercive force and magnetic thin film 3 with a large coercive force, but even if the difference in size is not very large,
The resulting pulse voltage generated in the pickup coil is difficult to obtain. In experiments conducted by the inventors, the coercive force of a magnetic thin film with a large coercive force (hereinafter referred to as a . . . -de film) is approximately greater than that of a magnetic thin film with a small coercive force (hereinafter referred to as a soft film). Pulse characteristics were obtained in a range of about 6 times to 2 degrees. However, when the magnification is further increased, the pulse voltage gradually becomes smaller. Even if the magnification is made smaller than this, the pulse voltage becomes smaller and the pulse width becomes wider, probably because the interaction between the soft film and the node film is weak. This is because if the coercive force of the hard film is too large, the magnetization direction of the soft film will be forced to the direction of magnetization of the hard film even in the absence of an external magnetic field, making it difficult to obtain a pulse voltage. Furthermore, if the coercive force of the hard film is larger than but close to that of the soft film, it will not be possible to effectively suppress or assist magnetization reversal of the soft film in response to an external magnetic field, and the pulse voltage will be close to that of a single film. It seems that you will be able to get it. In order to effectively generate an interaction between the coercive forces of the soft film and the hard film in response to an external magnetic field, it is preferable to select the component ratio of the soft film and the hard film to the above-mentioned ratio in FIG.

That is, the composition of the soft film is Fa: 36 to 62% by weight.
, Co: 41-63% by weight, V: 1-8% by weight, the composition of the hard film is Fe: 26-51% by weight, G
o: 40 to e 3% by weight, V: 2 to 15% by weight.

Note that the coercive forces of the magnetic materials can be appropriately combined at composition ratios other than these Fe-Go-V, but as will be described later, if the coefficient of thermal expansion of the substrate is significantly different from that of the magnetic film, 2 When deposited as a layered film, the apparent coercive force changes and the soft film 2. It is difficult to decide on the combination of hard films 3, and it is also difficult to produce them stably under various production conditions.

Such a soft film2. The hard film 3 is formed by vapor deposition on the substrate 1 by the method described above, but if the magnetization direction of the film is isodirectional, it is difficult to obtain the desired pulse. Both films have easy axes of magnetization and must be parallel to each other.

In order to provide a film with easy magnetization axes and to make the directions parallel to each other, it is necessary to form the film using a method using deposition force in a magnetic field.

Also, a soft film 2. When forming the hard film 3, it is deposited in a vacuum chamber. At this time, the interface between the soft film 2 and the hard film 3 is coated with an oxide film caused by moisture or other adsorbed gases, or a magnetic film caused by strain. If a layer with drastically different properties is formed, interaction between the two films becomes impossible.

To prevent this, soft membrane 2. It is necessary to continuously deposit and form the hard film 3 in the same tank without breaking the vacuum. Furthermore, since strain greatly changes even the magnetic properties of the film itself, it is important to match the coefficient of thermal expansion, which is a physical constant, of the substrate 1 with that of the soft film by as much as 1°. If the coefficient of thermal expansion of the hard film 3 is not significantly different from that of the substrate 1 or the soft film 2,
Variations in the magnetic field where pulses are generated are reduced.

If the hard film 3 is formed on a substrate and then the soft film 2 is formed overlappingly, even if the thermal expansion coefficient of the substrate 1 is made to match the value of the soft film 2 as much as possible in advance, it will not be directly affected by the hard film 3. As a result, a large amount of strain is applied to the soft film 2, and the magnetic characteristics tend to fluctuate.

This is also sensitive to the thickness of the hard film 3. However, if the soft film 2 is deposited on the substrate 1 and then the . . . -de film 3 is formed over the soft film 2, these effects can be improved.

The two magnetic thin films 2 and 3 thus formed overlappingly on the substrate 1 can be easily formed into, for example, a rectangular shape of an appropriate size by using photolithography. In this example, the FortResist is Shipley's AZ1.
Using 350J, a 400 micron x 25 micron piece was created. The magnetic film was manufactured using an aqueous solution of iron chloride.

On top of the magnetic thin films 2 and 3 consisting of two tanzaku-shaped layers, 5102 is deposited by sputtering to provide electrical insulation.
A film 4 is formed over the entire surface. The thickness of this Si,02 film 4 is 6
About 000 people. Next, an AP film for forming a pickup coil is deposited on the entire surface of the 5i02 film 4, and then a tanzaku-shaped magnetic thin film 2, 3 is formed using IJ technology.
A pickup coil 5 was formed on top. Note that 6 and 6' in FIG. 2 are electrode pads.

Examples of the present invention will be specifically described below.

[Example 1] Fe:Co:V=35-52 as magnetic material for soft film
:41-63:1-8 (weight ratio) as magnetic material for hard film Fe:Co:V=25-
The composition ratio of 51:40 to 63:2 to 5 (wt%) was used. For the substrate 1, borosilicate glass was used.

The thermal expansion coefficient of this substrate 1 can be varied from approximately 65×1O-77C to 8C by mainly changing the component ratio of horic acid and silica.
It can vary from 0x10 to about 710C. A soft film 2 is deposited on the substrate 1 to a thickness of 3000 nm by electron beam evaporation,
Subsequently, a hard film 3 having a thickness of 2,500 layers was deposited on top of the soft film 2. Various combinations of soft film 2 and hard film 30 were deposited as shown in Table 1. This 2
The layer film is made into a strip of 400 microns x 26 microns.
4) Formed using IJ-So technology. Etching was carried out using water-soluble ferric chloride.

Next, a 5i02 film 4 was deposited on the entire surface of the striped magnetic thin film by sputtering. This 5102 membrane 4
It was estimated that there would be around 5,000 people.

The coil 5 was formed by depositing Mue on the entire surface of the substrate by vacuum deposition. The film thickness of A/ is o, 8 microns,
The number of turns was 8 turns.

Next, it is cut using a dicing machine to form depths, then it is mounted on a lead frame-1-, and a 25 micron A wire is connected to the electrode pad 6°6' of the coil by wire bonding on the lead frame. Finally, I molded it.

3 The device thus produced was placed in a solenoid, an external magnetic field was applied, and the voltage of the aforementioned pulse generated at both ends of the pickup coil was measured.

In addition, the IKH coil is used for the external magnetic field.
An external magnetic field was generated by passing a sinusoidal current of z. The measurement results are shown in Table 1.

(The following is a blank space) 4 15 [Example 2] Using the magnetic material for the soft film and the magnetic material for the hard film used for the N1112 sample in Example 1, the material was deposited on the borosilicate glass substrate 1 by electron beam evaporation. The soft film is deposited first, and then the node film is deposited on top of it.
A comparison was made between a case in which a magnetic thin film of one layer was formed and a case in which a hard film was deposited first and then a soft film was deposited on top of it to form a two-layer magnetic thin film. The method after the step of forming the magnetic thin film in a danzag shape is the same as in Example 1.

The thickness of the soft film and hard film is 30oO, respectively.
The number of people was 2,500. As a result, when the hard film was deposited first, even if the external magnetic field was set much higher than the coercive force of the hard film, large and steep pulse characteristics could not be obtained, and only small pulses of about 25 μV were obtained. . In the case where the soft film was formed first, a pulse voltage as large as 1.75 μIJ volts and a pulse width of 0.1 microseconds or less were obtained. The relationship between pulse ' and ear pressure with respect to the external magnetic field is shown in FIG. Two types of pulses with different sizes were obtained in the region where the external magnetic field was small.

[Example 3] Example 1-1! ], 12 samples, the magnetic thin film was formed as follows. That is, after a soft film was first deposited on the substrate, the vacuum of the vacuum chamber was broken and the film was once exposed to normal pressure air, and then this was put back into the vacuum to deposit the hard film on top of the soft film. After the step of forming these two layers into a tanzak shape, the same method as in Example 1 was carried out.

The thin film magnetic sensor thus prepared was placed in an external magnetic field and driven. As a result, even if a magnetic field greater than the coercive force of the node film was applied, a large and steep pulse could not be obtained.

As shown in the examples above, in the present invention, the thermal expansion coefficient of the substrate is appropriately selected by changing the composition ratio of Fa, Go, and V for the soft and hard films, and the soft film is deposited first. Then, by depositing a hard film on top of a soft film, a large and steep external pulse voltage can be applied to the pickup voltage with respect to changes in the magnitude and direction of the external magnetic field.

7 A thin film magnetic sensor with such characteristics can be operated without load and has a higher output voltage than a thin film magnetic sensor that uses magnetoresistive characteristics or a Hall element that uses the Hall effect. Furthermore, since the output is obtained in the form of a pulse, it is useful as a sensor for obtaining digital signals. Furthermore, by making the film thinner, it can be miniaturized and is useful for integrated circuits such as ICs.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the composition ratio of Fa-Co-V system, coercive force, and saturation magnetization, FIG. The same plan view and FIG. 3 are diagrams showing the relationship between the external magnetic field and the pulse voltage of the thin film magnetic sensor created according to the present invention. 1... Substrate, 2, 3... Magnetic thin film, 4
...5102 membrane, 6...coil. Name of agent: Patent attorney Satoshi Nakao et al. 1 Tatsutsu 1
Drawing seat Co (wt Tao)

Claims (6)

[Claims] (1) A tanzaku-shaped magnetic thin film with a two-layer structure with different coercive forces is provided on the substrate, and a pickup coil is provided on top of the tanzaku-shaped magnetic thin film with an electrically insulating nonmagnetic film interposed therebetween, and the magnetic thin film is made of Fe- A thin film magnetic sensor comprising a Go-V alloy. (2) The two magnetic thin films having different coercive forces are both made of the same Fe-co-v alloy, but have different composition ratios. Thin film magnetic sensor. (3) A two-layer magnetic thin film with different coercive forces is a combination of a thin film with a small coercive force and a magnetic thin film with a large coercive force, and the ratio of the magnitude of the coercive force between the two is 6 to 20 times. A thin film magnetic sensor according to claim 1, characterized in that: (4) The component ratio of the composition of the magnetic thin film with low coercive force is Fe
:Co:v-36~52:41~63:1~8 (wt%
) The thin film magnetic sensor according to claim 2, characterized in that: (5) The component ratio of the composition of the magnetic thin film with large coercive force is Fe
The thin film magnetic sensor according to claim 2, characterized in that :CO:v-25~51:4o~63:2~15 (weight ratio). (6) The thin film magnetic sensor according to claim 1, wherein the easy axes of the two layers of the magnetic thin films having different coercive forces are aligned.