JPH11109006A - Magnetic impedance sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a sensor with improve linearity and temperature characteristics by winding a bias coil and a negative feedback coil around a thin-film magnetic core via an insulator. SOLUTION: A bias coil 4 and a negative feedback coil 5 consisting of a Cu sputter film are alternately wound in the same direction around an MI sensor plate 1 that is a rectangular, thin-plate-shaped thin-film magnetic core via insulator layers 2 and 3. Bias coil terminals 6 and 7 and negative feedback coil terminals 8 and 9 are provided at both terminals and MI sensor terminals 10 and 11 are provided at both terminals of the MI sensor plate 1. The terminals 6-11 are Au thin films and have a wide part for external wiring at the tip parts. An insulation protection film is provided while covering an entire part. The bias coil 4 and the negative feedback coil 5 in this structure have improved coil efficiency, a bias magnetic field can be obtained with less current, and the linearity of output for the magnetic field can be improved with less amount of negative feedback.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a magnetic sensor,
In particular, it relates to a magnetic impedance sensor which is a high-sensitivity magnetic sensor.

[0002]

2. Description of the Related Art With the rapid development of information devices and measurement / control devices in recent years, there has been an increasing demand for small, low-cost, high-sensitivity, high-speed magnetic sensors. For example, in a hard disk drive of an external storage device of a computer, the performance has been improved from a bulk type inductive magnetic head to a thin film magnetic head and a magnetoresistive effect (MR) head, and a rotary encoder which is a rotation sensor of a motor has a magnet. As the number of magnetic poles of the ring increases, a magnetic sensor capable of detecting a weak surface magnetic flux with high sensitivity is required instead of a conventionally used magnetoresistive effect (MR) sensor. In addition, demand for a high-sensitivity sensor that can be used for nondestructive inspection and banknote inspection has been increasing. In addition, there is a growing demand for small and lightweight direction sensors for automobiles, sensors for active magnetic shielding of display tubes of high-definition color televisions and personal computers, and the like.

[0003] Typical magnetic detecting elements currently used include an inductive reproducing magnetic head, a magnetoresistive (MR) element, a flux gate sensor, and a Hall element. Recently, the magnetic impedance effect of an amorphous wire (Japanese Patent Application Laid-Open No. 6-176930 and Japanese Patent Application Laid-Open No.
239, JP-A-7-333305) and the magnetic impedance effect of a magnetic thin film (JP-A-8-758).
No. 35, Journal of the Japan Society of Applied Magnetics, vol. 20,553
(See (1996))).

The inductive reproducing magnetic head requires a coil winding, so that the magnetic head itself becomes large, and when the size of the disk is reduced, the relative speed between the magnetic head and the medium is reduced, and the detection sensitivity is significantly reduced. There is. On the other hand, a magnetoresistive effect (MR) element using a ferromagnetic film has come to be used. The MR element detects the magnetic flux itself, not the temporal change of the magnetic flux, and thus, the miniaturization of the magnetic head has been promoted. However, the change rate of the electric resistance of the current MR element is about 2%, and even the MR element using the spin valve element has a small change rate of the electric resistance of 6% or less at the maximum and obtains a resistance change of several%. The external magnetic field required for this is as large as 20 Oe or more. Therefore, the magnetoresistive sensitivity is as low as 0.1% / Oe or less. Recently, a giant magnetoresistance effect (GMR) using an artificial lattice having a magnetoresistance change rate of several tens of percent has been found. But number 10
To obtain a% resistance change, an external magnetic field of several hundred Oe is required, and it has not been put to practical use as a magnetic sensor.

[0005] A fluxgate sensor, which is a conventional high-sensitivity magnetic sensor, has a symmetrical B-type magnetic core of high permeability, such as permalloy.
The magnetism is measured by utilizing the fact that the −H characteristic changes due to an external magnetic field, and a high resolution of 10 ⁻⁶ Oe and ± 1
° High directivity. However, in order to increase the detection sensitivity, a large magnetic core with a small demagnetizing field is required, making it difficult to reduce the size of the entire sensor and to increase the response speed.
In addition, there is a problem that power consumption is large.

In a magnetic field sensor using a Hall element, when a magnetic field is applied perpendicularly to the plane through which current flows, an electric field is generated in a direction perpendicular to both the current and the applied magnetic field, and an electromotive force is induced in the Hall element. This is a sensor that utilizes Hall elements are advantageous in terms of cost, but have low magnetic field detection sensitivity,
In addition, since it is composed of semiconductors such as Si and GaAs, the mobility of electrons or holes changes due to the scattering due to thermal oscillation of the lattice in the semiconductor due to temperature changes, and the temperature characteristics of magnetic field sensitivity are poor because of the disadvantage. .

[0007] JP-A-6-176930, JP-A-7-176930
As described in JP-A-181239 and JP-A-7-333305, a magneto-impedance element has been proposed to realize a significant improvement in magnetic field sensitivity, miniaturization, and high-speed response. The basic principle of this magneto-impedance element is to detect only the voltage with respect to the time change of the circumferential magnetic flux using the skin effect generated by applying a current that changes rapidly with time to a magnetic wire as a change due to an externally applied magnetic field. Magnetic impedance element.
FIG. 16 shows an example of the magneto-impedance element. This magnetic wire has a zero magnetostriction diameter of 3 such as FeCoSiB.
An amorphous wire of about 0 μm (wire that has been drawn and then annealed in tension) is used, and FIG. 17 shows the applied magnetic field dependence of the impedance change of the wire. When a high-frequency current of about 1 MHz is applied to a wire having a small dimension of about 1 mm, the voltage swing of the wire changes with a high sensitivity of about 100% / Oe, which is 1000 times or more that of the MR element.

[0008]

SUMMARY OF THE INVENTION As a magnetic sensor, a small, low-cost, linear output with respect to a detected magnetic field,
There is a need for high-sensitivity magnetic sensors with excellent temperature characteristics.
A magnetic sensor using the magneto-impedance effect of an amorphous wire exhibits high-sensitivity magnetic field detection characteristics. Also, JP-A-6-176930 and JP-A-6-347489.
The linearity of the applied magnetic field dependence of the impedance change is improved by applying a bias magnetic field, and a current is proportional to the voltage across the amorphous wire by winding a negative feedback coil around the amorphous wire. By applying a negative feedback to the coil,
This shows that a sensor excellent in linearity and response speed and invariant in magnetic field detection sensitivity with respect to a temperature change of the sensor unit can be provided.

However, since this high-sensitivity magnetic impedance element is made of an amorphous wire having a diameter of about 30 μm, it is not suitable for fine processing, and it has been difficult to provide an ultra-small magnetic detection element. In addition, electrode formation by soldering is not easy, and special measures have been taken. Further, both the bias coil and the negative feedback coil have to be wound around a thin copper wire to produce a coil, which limits the miniaturization and has a problem in productivity.

On the other hand, Japanese Patent Application Laid-Open No. 8-75835 proposes a magneto-impedance element using a magnetic thin film to reduce the size of the element, but to improve the linearity of sensor sensitivity. A method using a hard magnet and a method using a single-plate conductor have been proposed as the bias magnetic field applying method. The method of using a hard magnet for the bias is difficult to fabricate, and it is not easy to control the bias magnetic field due to the aging of the magnet. In addition, the method of applying a bias using a single-plate conductor is structurally simple, and the control of the bias magnetic field can be controlled by the amount of current, but since it is a single-plate conductor, it is necessary to obtain a bias magnetic field necessary for practical use. Requires a very large current to flow, which causes problems such as heat generation and disconnection of the element. No consideration is given to adding a negative feedback function.

The Journal of the Japan Society of Applied Magnetics, vol. 21,649
According to -652 (1997), a thin-film coil is wound around a thin-film magnetic core to form a bias coil, but this structure is not a structure having a bias coil and a negative feedback coil at the same time. Further, the use of Au for the thin film coil is problematic in terms of cost. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a small-sized, low-cost, high-sensitivity magnetic sensor excellent in linearity of output with respect to a detected magnetic field, temperature characteristics, and mass productivity.

[0012]

In order to achieve the object of the present invention as described above, the present invention provides a substrate made of a non-magnetic material, a thin film magnetic core formed on the substrate, and a longitudinal axis of the thin film magnetic core. A magneto-impedance sensor comprising a first electrode and a second electrode provided at both ends in the direction, having a structure in which a bias coil and a negative feedback coil are wound around an insulator around the thin-film magnetic core. A magneto-impedance sensor is provided. Further, the bias coil and the negative feedback coil are formed of thin-film coils, and are wound alternately and at a constant interval in the same direction. However, the number of turns may be the same. When forming a magnetic impedance sensor, a plurality of thin-film conductors are arranged in parallel on the lower surface of the thin-film magnetic core, insulated from the thin-film magnetic core, and are arranged in parallel on the upper surface of the thin-film magnetic core, insulated from the thin-film magnetic core. Having a plurality of thin film conductors, and electrically connecting the top ends of the thin film conductors on the upper and lower surfaces of the thin film magnetic core, respectively,
The bias coil and the negative feedback coil are formed alternately and in the same direction at regular intervals. The thin film magnetic core is made of NiFe, CoFeNi, FeP, FeNiP, FeCoP, FeNi
It is formed of a plated film of CoP, CoB, NiCoB, FeNiCoB, FeCoB, CoFe, or an amorphous sputtered film of CoZrNb, FeSiB, CoSiB, or a NiFe sputtered film.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a front view schematically showing the structure of a thin-film MI sensor using a magnetic impedance (MI) element according to the present invention, and FIG. 2 is a cross-sectional view taken along the line AB in FIG. FIG. 3 is a cross-sectional view taken along the line CD of FIG. Although the entire actual thin film MI sensor is formed on a plate-like body such as a thin film ceramic plate or a glass plate, this is omitted in FIG.
1, 2 and 3, reference numeral 1 denotes an MI sensor plate which is a thin-film magnetic core formed in a thin plate shape having a rectangular planar shape. The shape of the thin film magnetic core as the MI sensor plate is 20 μm in width, 5 μm in thickness, and 500 μm in length.
Around the MI sensor plate 1, a bias coil 4 and a negative feedback coil 5 are alternately wound in the same direction via insulating layers 2 and 3. Although not shown exactly in the figure, each of these coils has 20 turns. Bias coil terminals 6 and 7 are connected to both ends of the bias coil 4, and negative feedback coil terminals 8 and 9 are connected to both ends of the negative feedback coil 5. MI sensor terminals 10 and 11 are connected to both ends of the MI sensor plate 1. These terminals are made of an Au metal thin film, and the wide portions at the ends serve as pads for external wiring. Reference numeral 12 denotes an insulating protective film that covers the entire MI sensor.

Next, a manufacturing process of the thin film MI sensor according to the present invention will be described in detail with reference to FIG. Note that FIG. 4 is described in a state viewed from the AB cross section direction in FIG. FIG. 4A shows a lower coil portion constituting a bias coil and a negative feedback coil. Each end of each coil portion pattern is connected to the coil end portion of the upper coil portion pattern shown in FIG. 4E. Thus, the continuous bias coil 4 and the negative feedback coil 5 shown in FIG. 1 are configured.

[0015] As shown in (a) of FIG. 4, the coil lower part, Al ₂ O ₃ ceramic wafer, Si wafer, on the non-magnetic substrate 20 having enhanced surface smoothness such as glass wafer 5
A Cu sputter film having a thickness of about 0 nm is formed to serve as a seed layer for plating, and a photoresist pattern of a predetermined coil shape inversion pattern is formed on the seed layer. About 3μm plating
After removing the photoresist pattern with an organic solvent or the like, the seed layer of the Cu sputtered film is removed by etching, so that the coil pattern 21 is removed.
Is formed. On the other hand, a Cu sputtered film is formed to a thickness of about 3 μm, and thereafter, a photoresist pattern having a predetermined coil shape is formed, and the photoresist pattern is used as an etching mask to perform etching by etching means such as ion milling. By removing the photoresist pattern with an organic solvent or the like, the lower coil portion can be manufactured. The method of manufacturing a Cu coil according to the above can reduce the size of the coil itself and bring the coil closer to the magnetic core compared to a method of manufacturing a coil by winding a conductor wire or a method of manufacturing a coil by winding a conductor ribbon. Therefore, the coil efficiency can be increased.

As shown in FIG. 4B, an insulator layer 3 is deposited on the lower layer of the formed coil. FIG. 4 (c)
A thin-film magnetic core is formed on the insulator layer 3. This thin film magnetic core is made of a plated film of NiFe, CoFeNi, etc.
Amorphous sputtered film of ZrNb, FeSiB, CoSiB, etc., Ni
A soft magnetic film such as a Fe sputtered film is used. Where NiFe
An example of preparation when a plating film is used as a thin-film magnetic core will be described. First, a NiFe sputtered film having a thickness of about 50 nm is formed to be a seed layer for plating. A photoresist pattern of a reverse pattern of a predetermined coil shape is formed on the seed layer, and then NiFe plating is buried to a thickness of about 5 μm between the photoresist patterns, and the photoresist pattern is removed with an organic solvent or the like. Later, Ni
It is formed by removing the seed layer of the Fe sputtered film by etching. When a CoFeNi plating film is used as a thin-film magnetic core, a similar process is used. Further, if a heat treatment is performed in a rotating magnetic field and in a static magnetic field after forming the thin film magnetic core, the magnetic properties can be improved.

Next, a manufacturing process in the case of using a soft magnetic film such as an amorphous sputtered film such as CoZrNb, FeSib or CoFeB or a NiFe sputtered film as a thin film magnetic core will be described. For example, a CoZrNb sputtered film is formed to a thickness of about 5 μm, then a photoresist pattern having a predetermined magnetic core shape is formed, and the photoresist pattern is used as an etching mask, and is etched by an etching means such as ion milling. Further, the lower coil portion can be formed by removing the photoresist pattern with an organic solvent or the like. On the other hand, there is also a metal mask method in which a predetermined thin film magnetic core is inverted on a thin metal plate and is used as a sputtering mask. However, this method makes it difficult to obtain a magnetic core having a fine shape and has poor dimensional accuracy. Not preferred.

As shown in FIG. 4D, an insulating layer 2 is formed on the thin film magnetic core. This insulating layer 2
This is an insulating film for electrically insulating the next upper coil portion and the thin-film magnetic core. The forming method is the same as that of the insulator layer 3 shown in FIG. Next, as shown in FIG. 4E, a coil upper layer constituting a bias coil and a negative feedback coil is formed on the surface of the insulator layer 2. As shown in the description of FIG. 4A, the end of each coil is connected to the coil end of the coil lower layer shown in FIG. 4A, and the continuous bias coil 4 and the negative feedback are provided. The coil 5 is configured. The manufacturing method is the same as that of the case of forming the coil upper layer shown in FIG.

After the step shown in FIG. 4E is completed, an electrical connection is obtained between the insulating protective film 12 for protecting the manufactured magnetic sensor unit and a peripheral circuit for driving and detecting the magnetic sensor. Pad for wire bonding (bias coil terminal 7, MI sensor terminal 10, 1)
1 etc.) to obtain the state of FIG. The insulating protective film 12
The photoresist is exposed and developed in the same manner as the insulating layer 3 shown in FIG. 4 (b), formed into a predetermined insulating layer shape, and then cured by heat treatment at 270 ° C. for 10 hours. Used. Further, a resin obtained by curing a resin such as polyimide, or a resin obtained by forming an inorganic film such as SiO ₂ into a predetermined shape may be used. The bonding pad for wire bonding is made of an Au plating film or an Au sputtered film. The manufacturing process is substantially the same as that for the Cu coil. In this manner, the thin film processes are sequentially stacked from FIG. 4A to FIG. 4E and FIG.
An I-sensor is created.

The magnetic impedance effect (MI effect) is a phenomenon in which when a high-frequency current is applied to a high-permeability magnetic material, the impedance at both ends of the magnetic material changes due to an external magnetic field applied in the direction in which the current is applied. That is, the internal inductance Li of the magnetic material and the impedance Z = Rw (μθ) + jωLi (μθ) due to the resistance Rw that increases with the current frequency f due to the skin effect apply an external magnetic field. This changes as a function of the magnetic permeability μ in the width direction of the magnetic material that changes as a result. In the case of a thin film, the resistance Rw of the thin film in a high-frequency region (thickness d> 2δ) where the skin effect is remarkable is represented by a DC resistance Rd.
Assuming that c, Rw = Rdc (d / 2δ) can be expressed. On the other hand, when d> 2δ, the inductance can be expressed as L = Li (2δ / d). Here, δ indicates the depth of the epidermis,
The values are as shown in FIG. Therefore, the impedance Z of the thin film
Is as follows: Z = Rdc (d / 2δ) + jωLi (2δ / d) Here, assuming that the thickness of the thin film is d = 2a, and the width is W and the length is 1, the absolute value of the impedance Z of the thin film is as shown in FIG. Here, since the skin depth δ is as shown in FIG. 5, the absolute value of the impedance Z of the thin film is a function of the magnetic permeability μθ.

As shown in FIG. 7A, when uniaxial anisotropy is given in the width direction of the pattern of the thin film, the magnetization vector is oriented in the width direction and the magnetic domain structure has a structure having a 180 ° domain wall. Become. When a high-frequency current flows in the length direction of the thin film, a high-frequency magnetic field is generated in the width direction.
Movement of the 0 ° domain wall is hindered by eddy current braking. Also,
Since the direction of the high-frequency magnetic field and the direction of the magnetization vector are the same, rotational magnetization hardly occurs. Therefore, the change in magnetic flux is small and μθ is small.

On the other hand, an external magnetic field extends in the length direction of the thin film pattern.
When Hex is applied, the direction of the magnetization vector is tilted from the width direction, so that the magnetic field generated by the high-frequency current causes the rotation of the magnetization vector (rotational magnetization), and thus the change in the magnetic flux.
θ increases. The external magnetic field Hex is the anisotropic magnetic field of the pattern
When it becomes equal to Hk, μθ becomes maximum, and at this time, the impedance Ζ becomes maximum. Hex is larger (Hex
> Hk), the magnetization vector is fixed at Hex, so the rotation of the magnetization vector is suppressed, and μθ decreases,
Accordingly, Z also becomes smaller. These phenomena will be verified using FIG. 7B based on a rotational magnetization model. The rotation angle θ ₀ when H θ = 0 is determined by the minimum energy condition of Expression (3) shown in FIG. Therefore, Hk
= 2 Ku / Ms, θ ₀ = Hex / Hk is obtained. Wherein a change in the rotation angle by H θ | Δθ |> magnetization variation ΔΜ of theta ₀ to the width direction is expressed by the following equation. ΔM = Ms COSθ ₀ Δθ (4) The total energy including the term based on Hθ is expressed by the following equation. E = -Ms (Hθ + Hk) COS [π / 2- (θ 0 + Δθ)] - Ms Hex COS (θ 0 + Δθ) ····· (5) (5) formula used is shown in FIG. 9 ( Calculate Δθ from equation 7),
By substituting into equation (4), equation (6) shown in FIG. 9 is obtained. Accordingly, it is shown that when Hex <Hk, μθ, that is, Ζ, increases as the magnetic field increases, reaches a maximum value when Hex = Hk, and then decreases as the magnetic field increases. When the magnetization vector is oriented in the length direction of the thin film pattern, the μ effect in the width direction due to Hex hardly changes, so that the MI effect becomes very small.

Next, the characteristics of the manufactured thin film MI sensor will be described. Here, the dimensions of the thin-film magnetic core are 20 μm in width, 5 μm in thickness, and 500 μm in length, and the energizing current is 10 mA. The coils for bias and negative feedback are wound alternately on the same surface, and the number of turns is 20 turns, respectively. A bias magnetic field and a negative feedback magnetic field can be uniformly applied to each part of the magnetic core by a structure in which a bias coil and a negative feedback coil are alternately wound around the same surface on the same surface, thereby stabilizing the characteristics as a magnetic sensor. . FIG. 10 shows a magnetic field of 0 and 30 Oe (Hex) in the length direction of the thin film magnetic sensor when the thin film magnetic core is formed by NiFe plating.
) Is applied to both ends of the sensor Ε (Ε = Ζ * I)
4 shows the current-carrying frequency characteristics of FIG. Hex = 0 and Hex =
The difference ΔΕ of Ε at 30 Oe is 20MHz
It was the largest near. FIG. 11 shows that the current frequency is 20 MHz.
It shows the applied magnetic field (Hex) dependence of the rate of change of impedance when z (10 mA) is constant. As the applied magnetic field is increased, the rate of change of impedance ΔΖ / Z _o
Becomes large, and ΔΖ /
Z _o is the maximum and will, in addition Hex> Hk ΔΖ / Z _o becomes smaller. These results have the characteristics shown by the above-mentioned theoretical formula. The amount of change in impedance per unit applied magnetic field (magnetic field sensitivity) became maximum around Hex = 20 Oe, indicating a magnetic field sensitivity of 1.5% / Oe.

When used as a magnetic sensor, the sensitivity of the sensor can be improved by bringing the operating point to the maximum sensitivity. FIG. 12 shows a change rate of impedance ΔΖ / when the operating point is changed by applying a bias magnetic field of 20 Oe to the thin film magnetic material by passing a current through the bias coil.
It applied magnetic field of Z _o (Hex) shows the dependence. As can be seen from the figure, by applying a bias magnetic field of 20 Oe to the magnetic core using a thin-film coil, MI characteristics that maximize the magnetic field sensitivity at a magnetic field of 0 Oe were obtained.

FIG. 13 shows the relationship between the coil magnetomotive force (the product of the current and the number of turns) and the bias magnetic field. When a thin film coil is used as a bias coil, 28 (Oe / A
T) is the slope of the graph of FIG.
The value was 2 (Oe / AT) when a bias coil in which a copper wire was wound around an amorphous wire having a diameter of m was produced. The thin film coil was close to the NiFe thin film core and could form the coil densely, so that the coil efficiency for converting current to magnetic flux was 10 times or more higher than that of a bias coil wound with a copper wire.

On the other hand, when the applied magnetic field
When the operating point is moved to bring the maximum sensitivity to
As shown in FIG. 12, the linearity of the change in impedance (change in output) with respect to the magnetic field is not very good. As a method for improving this linearity, the output signal is fed back, and the output signal is corrected by applying a magnetic field sufficient to correct the nonlinearity of the output with respect to the magnetic field using a negative feedback coil to the thin film magnetic core as a negative feedback magnetic field. There is a way to get sex. FIG. 14 shows a block diagram of an electronic circuit of the linear magnetic field MI sensor. With this circuit, the operating point is moved to the point of maximum sensitivity, the output signal is fed back, and a negative feedback magnetic field is applied to the thin film core to improve the linearity of the sensitivity characteristic.

FIG. 15 shows the relationship between the applied magnetic field and the output voltage when applying a negative feedback with a bias coil magnetic field of 20 Oe and a negative feedback rate of 50% using the circuit of FIG. Here, the frequency of the conduction current is 20 MHz, and the amplification of the output is 500 times. As shown in the figure, excellent linearity was exhibited within a measurement magnetic field of ± 3 Oe, and a magnetic field resolution of 10 ⁻⁵ Oe was exhibited. These results are good characteristics as a linear magnetic field sensor. In the case of a device using a negative feedback coil in which a copper wire is wound around a comparative amorphous wire, about 300% of negative feedback had to be applied in order to obtain a straight line equivalent to the diagram. As compared to the negative feedback coil in which a copper wire is wound around an amorphous wire, the thin film coil obtained the same linearity with a negative feedback rate of about 1/6. This is due to the high efficiency. The above is an example of measurement. As another method of driving the MI sensor, a pulse excitation type MI using a C-MOSIC capable of driving with low power consumption is used.
It is also possible to use effects. Further, the bias magnetic field can be applied by applying a pulse in conjunction with the pulse excitation, whereby a necessary bias magnetic field can be obtained.

Although the present invention has been described with reference to the above-described embodiment, various modifications can be made within the scope of the present invention. For example, the bias coil 4 and the negative feedback coil 5 are not made to have the same number of turns, and as shown in FIG.
May be partially short-circuited by a connection line 5 ′ that straddles the bias coil 4, and the number of turns between the bias coil 4 and the negative feedback coil 5 may be changed. Of course, a part of the bias coil 4 may be connected by a connecting wire to change the number of turns of the bias coil and the negative feedback coil. These modifications and applications are not excluded from the scope of the present invention.

[0029]

The thin-film MI having a thin-film coil for bias and negative feedback formed around the thin-film magnetic core via an insulator.
The sensor structure enables the magnetic sensor to be miniaturized, highly reliable, and mass-produced, and the thin-film coil manufactured with the above structure has high coil efficiency, so the required bias magnetic field can be obtained with a small current. In addition, the output linearity with respect to the magnetic field can be improved with a small amount of negative feedback. From these facts, it is possible to provide a thin-film linear magnetic field sensor having high sensitivity, good linearity of sensitivity, and excellent temperature characteristics. Further, by alternately winding the thin film coil for bias and the thin film coil for negative feedback, a bias magnetic field and a negative feedback magnetic field can be uniformly applied to each part of the magnetic core of the thin film, and the characteristics as a magnetic sensor are stabilized. .

[Brief description of the drawings]

FIG. 1 shows a magnetic impedance (M) according to the present invention.
FIG. 1 is a front view schematically showing a structure of a thin film MI sensor using an element.

FIG. 2 is a sectional view taken along the line AB in FIG. 1;

FIG. 3 is a sectional view taken along the line CD of FIG. 1;

FIG. 4 is a sectional view showing a manufacturing process of the magneto-impedance sensor according to the present invention.

FIG. 5 is an equation diagram showing values of δ.

FIG. 6 is an equation diagram showing an absolute value of impedance.

FIG. 7 is a model diagram of a magnetic domain structure of a magnetic core portion of the thin-film MI sensor.

FIG. 8 is an equation showing the value of EO.

FIG. 9 is an equation diagram showing the value of ΔM0.

FIG. 10 is a characteristic diagram showing the dependence of the output on the current-carrying frequency.

FIG. 11 is a characteristic diagram illustrating magnetic field dependence of an impedance change rate.

FIG. 12 is a characteristic diagram illustrating the magnetic field dependence of the impedance change rate when a bias magnetic field of 20 Oe is applied.

FIG. 13 is a characteristic diagram illustrating a bias coil magnetomotive force dependency of a bias magnetic field intensity.

FIG. 14 is a circuit block diagram using a magnetic impedance sensor according to the present invention.

FIG. 15 is a characteristic diagram showing linear sensing characteristics of the magnetic impedance sensor according to the present invention.

FIG. 16 is a circuit block diagram using a magnetic impedance sensor.

FIG. 17 is a characteristic diagram illustrating an MI effect of an amorphous wire.

FIG. 18 is a front view showing another embodiment.

[Explanation of symbols]

 1 ... MI sensor plate 2 ... Insulator layer 3 ... Insulator layer 4 ... Bias coil 5 ... Negative feedback coil 6 ... Bias coil terminal 7 Bias coil terminal 8 Negative feedback coil terminal 9 Negative feedback coil terminal 10 MI sensor terminal 11 MI sensor terminal 12 ... Insulating protective film 20 ... Nonmagnetic substrate 21 ... Coil pattern

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akiyo Yuguchi 173-1 Asana-machi, Asaba-cho, Iwata-gun, Shizuoka Prefecture Inside the Minebea Development Technology Center (72) Inventor Yoshinori Mouri Tenpaku, Tenpaku-ku, Nagoya-shi Shimada Kuroishi 3911-3

Claims (7)

[Claims] 1. A magnetic impedance sensor comprising a substrate made of a non-magnetic material, a thin-film magnetic core formed on the substrate, and first and second electrodes provided at both longitudinal ends of the thin-film magnetic core. A magnetic impedance sensor having a structure in which a bias coil and a negative feedback coil are wound around an insulator around the thin-film magnetic core. 2. The magneto-impedance sensor according to claim 1, wherein the bias coil and the negative feedback coil are constituted by thin-film coils. 3. The magneto-impedance sensor according to claim 1, wherein the bias coil and the negative feedback coil are wound alternately at a constant interval in the same direction. 4. The magneto-impedance sensor according to claim 1, wherein the bias coil and the negative feedback coil are wound the same number of times around the thin-film magnetic core. 5. A plurality of thin-film conductors arranged in parallel on the lower surface of the thin-film magnetic core and insulated from the thin-film magnetic core, and a plurality of thin-film conductors arranged on the upper surface of the thin-film magnetic core and insulated from the thin-film magnetic core. A bias coil and a negative feedback coil, which are electrically connected alternately at regular intervals and in the same direction by electrically connecting the top ends of the thin film conductors on the upper and lower surfaces of the thin film magnetic core. The magneto-impedance sensor according to claim 2, wherein 6. The thin film magnetic core is made of NiFe, CoFeNi, FeP
, FeNiP, FeCoP, FeNiCoP, CoB, NiCoB, FeNiCoB
, FeCoB, CoFe plating film, or CoZrNb, FeSiB
2. The magneto-impedance sensor according to claim 1, wherein the magneto-impedance sensor is formed of a CoSiB amorphous sputtered film or a NiFe sputtered film. 7. The magneto-impedance sensor according to claim 1, wherein the thin-film magnetic core is heat-treated in a magnetic field.