JP3360168B2 - Magnetic impedance element - Google Patents

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 recent rapid development of information devices and measurement / control devices, there is an increasing demand for small, low-cost, high-sensitivity, high-speed magnetic sensors. For example, in the hard disk drive of the external storage device of the computer, the performance has been improved from the bulk type inductive magnetic head to the thin film magnetic head and the magnetoresistive (MR) head, and the rotary encoder which is the rotation sensor of the motor has the magnet. Since high ring magnetization density is required, the conventionally used magnetoresistive effect
There is a need for a magnetic sensor that can detect weak surface magnetic flux with high sensitivity in place of the (MR) sensor. In addition, demand for high-sensitivity sensors that can be used for nondestructive inspection and banknote inspection has been increasing.

At present, typical magnetic detecting elements used include an inductive reproducing magnetic head, a magnetoresistive effect (MR) element, a flux gate sensor, and a Hall element. Recently, the magnetic impedance effect of an amorphous wire (JP-A-6-176930, JP-A-7-181239, JP-A-7-333305) and the magnetic impedance effect of a magnetic thin film (JP-A-8-75835, Japanese Application Journal of the Magnetics Society of Japan vol.20,5
53 (1996)) has been proposed.

The inductive reproducing magnetic head requires a coil winding, so that the magnetic head itself becomes large. Further, when the magnetic head is miniaturized, the number of turns of the coil is reduced, and the detection sensitivity is remarkably lowered. On the other hand, a magnetoresistance (MR) element using a ferromagnetic film has come to be used. The MR element detects the magnetic flux itself rather than the time change of the magnetic flux, and thus the miniaturization of the magnetic head has been promoted.
However, even the current MR element, for example, an MR element using a spin-valve element, has a small rate of change in electric resistance of 6% or less at the maximum, and an external magnetic field required to obtain a resistance change of several%.
1.6kA / m or more. Therefore, the magnetoresistance sensitivity is 0.001% /
(A / m) Low sensitivity below. Recently, the giant magnetoresistance effect (GM
R) has been found. However, an external magnetic field of several tens A / m is required to obtain a resistance change of several tens of percent, and practical use as a magnetic sensor has not been realized.

The flux gate sensor measures the magnetism by utilizing the fact that the symmetric BH characteristic of a high magnetic permeability core such as permalloy is changed by an external magnetic field, and has a high resolution and a high directivity of ± 1 °. Have. However, there is a problem that a large magnetic core is required to increase detection sensitivity, it is difficult to reduce the size of the entire sensor, and 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 of thermal oscillations of the lattice in the semiconductor due to temperature changes. Have.

Japanese Unexamined Patent Publications Nos. 6-176930, 7-181239, and 7-333305 disclose a magneto-impedance element, which achieves a significant improvement in magnetic field sensitivity. This magnetic impedance element is a magnetic impedance element whose basic principle is to detect only a voltage with respect to a time change of a circumferential magnetic flux generated by applying a time-varying current to a magnetic wire as a change due to an externally applied magnetic field. is there. FIG. 12 shows an example of the magneto-impedance element. Magnetic impedance element 1 of FIG.
Then, as the magnetic wire 2, the diameter of zero magnetostriction such as FeCoSiB is 30 μm.
Amorphous wires (wires that have been drawn and then annealed in tension) have been used. FIG. 13 shows the applied magnetic field dependence of the impedance change of the wire (for example, the magnetic wire 2 in FIG. 12). When a high-frequency current of about 1 MHz is applied to a small-sized wire with a length of about 1 mm, the amplitude of the wire voltage changes with a high sensitivity of about 0.1% / (A / m), which is 100 times or more that of the MR element.

[0008]

SUMMARY OF THE INVENTION As a magnetic sensor,
There is a need for a high-sensitivity magnetic sensor that is small, low-cost, and has excellent output linearity and temperature characteristics with respect to the detected magnetic field. Magnetic sensors that use the magnetic impedance effect of amorphous wires exhibit high-sensitivity magnetic field detection characteristics. . Further, in Japanese Patent Application Laid-Open Nos. 6-176930 and 6-347489, the application of a bias magnetic field improves the linearity of the applied magnetic field dependence of the impedance change. By applying a current proportional to the voltage at both ends of the wire to the coil and applying negative feedback, a sensor (high-sensitivity magnetic impedance element) with excellent linearity and invariant magnetic field detection sensitivity to changes in the temperature of the sensor section It is shown that it 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. Also, both the bias coil and the negative feedback coil must be manufactured by winding a thin copper wire, and there is a limit to miniaturization, and
Since an oxide film is formed on the surface of the wire, there is a problem in terms of productivity, such as poor solderability of the electrode.
Furthermore, if the length of the element is increased in order to increase the impedance of the element for the purpose of obtaining a large sensor output, it is not suitable for downsizing the magnetic sensor. On the other hand, it is conceivable to use the wire by bending the wire, but when the wire, which is a magnetic material, is bent, the magnetic properties are deteriorated due to the strain stress, and the sensor output is significantly deteriorated. It is also conceivable to divide the wires into several wires, arrange the wires in parallel, and use them electrically connected in series, but this involves productivity problems such as soldering of electrodes.

On the other hand, Japanese Patent Application Laid-Open No. 8-75835
The publication proposes a magneto-impedance element using a magnetic thin film to reduce the size of the element. In addition, the inventors have proposed a small-sized magnetic impedance element having a bias coil and a negative feedback coil in which a thin-film coil is three-dimensionally wound around a thin-film magnetic core in Japanese Patent Application No. 9-269084. In this case, to increase the sensor output, that is,
In order to increase the amount of change ΔZ in impedance, it is necessary to increase the length of the element when the rate of change ΔZ / Z in impedance and the width and thickness of the element are fixed. For this reason, there is a problem that the entire chip size becomes large.

[0011] Also, "electronic technology" (Nikkan Kogyo Shimbun) 1
A magnetic impedance (MI) element has been proposed in which a magnetic thin film as shown in FIG. In the structure, the magnetic domain structure of the curved part becomes complicated, and when a magnetic field is applied from the outside, the magnetic domain wall of the curved part moves unevenly, causing noise due to a sudden change in the output voltage of the element due to the Barkhausen jump. Becomes

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a small-sized, low-cost, high-output, high-sensitivity magneto-impedance element excellent in output linearity with respect to a detected magnetic field and excellent in temperature characteristics. With the goal.

[0013]

According to the first aspect of the present invention,
In a magneto-impedance element comprising a substrate made of a non-magnetic material and a thin-film magnetic core formed on the substrate and provided with electrodes at both ends in the longitudinal direction, at least three or more thin-film magnetic cores have an interval of 5 μm or more. And the respective thin-film magnetic cores are electrically connected to each other in series. At least two or more thin film magnetic cores are arranged in parallel as in the above configuration, and the respective thin film magnetic cores are electrically connected to each other in series, without increasing the overall chip size. The impedance of the magnetic impedance element can be increased, thereby increasing the sensor output.

According to a second aspect of the present invention, in the configuration of the first aspect, a thin-film bias coil and a thin-film negative feedback coil are formed on the thin-film magnetic core with an insulator interposed therebetween. The negative feedback coils are wound alternately in the same direction on the same plane at regular intervals, and are each wound the same number of times. The above magnetic impedance element has a structure in which thin film coils for bias and negative feedback are wound around a thin film magnetic core arranged in parallel with an insulator interposed therebetween. With this structure, the magnetic sensor can be miniaturized and mass-produced, and the thin-film coil manufactured in the above structure has a high coil efficiency, so that a necessary bias magnetic field can be obtained with a small current, and With the amount of negative feedback, the linearity of the output with respect to the magnetic field can be improved. In addition, by alternately winding the thin film coil for bias and the thin film coil for negative feedback on the same plane, 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. Characteristics are stabilized.

The third aspect of the present invention provides the first or second aspect.
In the configuration described in the above, the thin film magnetic core is NiFe, Co
Fe, NiFeP, FeNiP, FeCoP, FeNiCoP, CoB, NiCoB
, FeNiCoB, FeCoB, at least one of the group of CoFe
The seed is formed from a selected plating film. According to a fourth aspect of the present invention, in the configuration of the first or second aspect, the thin-film magnetic core is made of CoZrNb, FeSi.
It is characterized by being formed by an amorphous sputtered film formed of any one of B and CoSiB or a NiFe sputtered film.

[0016]

Next, first and second embodiments of the present invention will be described.
The magneto-impedance element in the form of FIG.
However, before that, a reference example (first reference example)
All the magnetic impedance elements will be described based on FIG. 1 and with reference to FIGS. First, the magnetic impedance effect (MI effect) of a magnetic impedance element (hereinafter, the magnetic impedance is appropriately indicated as MI) and its characteristics will be described.

The MI effect is a phenomenon in which when a high-frequency current is applied to a high-permeability magnetic material, the impedance between both ends is changed by an external magnetic field applied in the direction of application. That is,
The impedance Z (shown by the equation (1)) due to the internal inductance Li of the magnetic material and the resistance Rw that increases with the frequency f of the flowing current due to the skin effect is increased by applying a magnetic field from the outside. Varying magnetic permeability in the width direction

(Equation 1) Because it varies as a function of

[0018]

(Equation 2)

When the magnetic material is a thin film, the resistance of the thin film in a high frequency region (thickness d >> 2δ) where the skin effect is remarkable.
Rw is Rw = Rdc (d / 2δ), where DC resistance is Rdc
It can be expressed as When the film thickness d >> 2δ, the inductance L can be expressed as L = Li (2δ / d). Here, δ indicates the skin depth, which is a value shown in Expression (2).

[0020]

(Equation 3)

Therefore, the impedance Z of the thin film is given by Z = Rd
c (d / 2δ) + jωLi (2δ / d). here,
When the thickness of the thin film is d = 2a, and the width is W and the length is l, the impedance Z of the thin film is as shown in Expression (3).

[0022]

(Equation 4)

Here, since the skin depth δ is given by the equation (2), the impedance Z of the thin film is

(Equation 5) Is a function of

Further, as shown in FIG. 10, when the pattern of the thin film 3 is provided with uniaxial anisotropy in the width direction, the magnetization vector is directed in the width direction and the magnetic domain structure has a 180 ° domain wall. . When the high-frequency current _Iac flows in the length direction of the thin film 3, a magnetic field is generated by the high-frequency current in the width direction, but the movement of the 180 ° domain wall is hindered by eddy current braking. In addition, since the direction of the magnetic field due to the high-frequency current and the direction of the magnetization vector are the same, rotational magnetization hardly occurs. Therefore, there is little change in magnetic flux and magnetic permeability

(Equation 6) Is small.

On the other hand, when an external magnetic field Hex (FIG. 11) is applied in the length direction of the pattern of the thin film 3, the direction of the magnetization vector is tilted from the width direction. Permeability due to change

(Equation 7) Becomes larger. When the external magnetic field Hex becomes the same as the anisotropic magnetic field Hk of the film pattern (the pattern of the thin film 3)

(Equation 8) Is maximum, and the impedance Z is maximum at this time. When Hex is further increased (Hex> Hk), the magnetization vector is fixed at Hex, so that the rotation of the magnetization vector is suppressed,

(Equation 9) Becomes smaller, and the impedance Z
Is also getting smaller.

These phenomena will be verified based on the magnetization rotation model with reference to FIG.

(Equation 10) In this case, the rotation angle θ ₀ is determined by the minimum energy condition of the following equation (4).

E ₀ = −Ku cos ² (π / 2−θ ₀ ) −Ms Hex cos θ ₀ (4)

Therefore, using Hk = 2 Ku / Ms, θ
₀ = Hex / Hk is obtained. here

[Equation 11] If Δθ << θ ₀ , the change ΔM in the width direction can be expressed by the following equation (5).

ΔM = Ms cos θ ₀ Δθ (5)

(Equation 12) The total energy including the term due to is expressed by the following equation.

[0030]

(Equation 13)

From this equation (6) and the following equation (7), Δθ is obtained,
Substituting this Δθ into equation (5) gives equation (8).

[0032]

[Equation 14]

Therefore, when Hex <Hk, the magnetic permeability increases with the increase of the magnetic field.

(Equation 15) That is, it is shown that the impedance Z 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,

(Equation 16) Does not change much, so the MI effect is very small.

Here, the first reference example will be described. FIG.
FIG. 3 is a schematic diagram showing a structure of a thin-film MI sensor 4 (magnetic impedance element) of a first reference example . Hereinafter, the thin film MI sensor 4
The two thin-film MI magnetic cores 5 are arranged in parallel at an interval of 20 μm, and the respective cores 5 are electrically connected in series by a nonmagnetic conductor 6 such as Cu. In this case, the total length of the magnetic core (thin-film MI magnetic core 5) can be doubled without increasing the overall length of the sensor element (thin-film MI sensor 4), so that the impedance is doubled and The sensor sensitivity (the sensitivity of the thin-film MI sensor 4) is doubled because the magnetic field from is uniformly applied to the two magnetic cores. The core 5 is a substrate made of a non-magnetic material (not shown) (see the non-magnetic substrate 20 in FIG. 7).
Is formed on.

In FIG. 1, the thin film MI magnetic core 5 is made of NiFe, CoFe,
NiFeP, FeNiP, FeCoP, FeNiCoP, CoB, NiCoB, FeN
At least one selected from the group consisting of iCoB, FeCoB and CoFe is formed of a plating film (soft magnetic film). The thin-film MI magnetic core 5 may be formed by an amorphous sputtered film (soft magnetic film) formed of CoZrNb, FeSiB, or CoSiB, or a NiFe sputtered film (soft magnetic film).

Here, a description will be given of a production example in which a NiFe plating film is used as a thin film magnetic core (thin film MI magnetic core 5). First, a NiFe sputtered film having a thickness of about 200 nm is formed to be a seed layer for plating. A photoresist pattern of a predetermined coil shape reverse pattern is formed on the seed layer, and then NiFe plating is buried to a thickness of about 3 μm between the photoresist patterns, and the photoresist pattern is removed with an organic solvent or the like. After doing
It is formed by removing the seed layer of the NiFe sputtered film by etching. When a CoFeNi plating film is used as a thin-film magnetic core (thin-film MI magnetic core 5), a similar process is used. In addition, if the heat treatment is performed in a rotating magnetic field and in a static magnetic field after manufacturing the thin film magnetic core, the magnetic properties can be improved.

In FIG. 1, reference numeral 7 denotes a thin-film MI element (thin-film MI sensor 4).
This is an electrode for passing a high-frequency current through the device. Further, as described above, the nonmagnetic conductor 6 such as Cu is a conductor for electrically connecting the two thin-film MI magnetic cores 5 in series, and the nonmagnetic conductor 6 is made of Au, Al, or the like. A non-magnetic low-resistance conductor may be used. The case where Cu is used for the nonmagnetic conductor 6 will be described.
A 50-nm thick Cu sputter film is formed to serve as a seed layer for plating.After forming a photoresist pattern of a predetermined coil-shaped inversion pattern on the seed layer, a photoresist pattern is formed between the photoresist patterns. Cu plating about 3 μm
After the photoresist pattern is removed by an organic solvent or the like, the seed layer of the Cu sputtered film is removed by etching.
In addition, a Cu sputtered film is formed to a thickness of about 3 μm, then a predetermined coil-shaped photoresist pattern is formed, and the photoresist pattern is used as an etching mask to perform etching by ion milling or other etching means. Furthermore, the lower coil portion can be manufactured by removing the photoresist pattern with an organic solvent or the like. An Au wire bonding pad is formed at the end of the conductor. After that, each chip is cut by a slicer. The chip size at this time was 2.3 mm × 1.2 mm.

As described above, FIG. 1 (first reference example)
1 shows a thin-film MI sensor 4 using a thin-film MI magnetic core 5. On the other hand, the first embodiment of the present invention shown in FIG.
Now, three thin film MI magnetic cores 5 are arranged in parallel to
The sensor 4 is constituted. Further, instead of FIG. 3, four or more thin-film MI magnetic cores 5 are arranged in parallel to form a thin-film MI sensor 4.
(Second embodiment of the present invention) may be configured. FIG.
(First embodiment of the present invention) and FIG. 3 (second embodiment of the present invention )
In the embodiment , the interval between the thin-film MI magnetic cores 5 arranged in parallel is 20 μm,
Are electrically connected in series by a nonmagnetic conductor 6 such as Cu. By the way, three or more elements (thin-film MI magnetic core 5)
When the elements are arranged in close proximity to each other, the outermost element (thin-film MI magnetic core 5) and the innermost element (thin-film MI magnetic core 5) cause magnetic interference, and are equally applied to each element. It is conceivable that no magnetic field is required. Here, FIG. 4 shows the difference in magnetic flux between the outer element and the inner element when three elements (thin-film MI magnetic core 5) are arranged in parallel and a uniform magnetic field is applied. When the distance between the elements is changed, the magnetic flux density of the inner element with respect to the outer element is expressed in%. When the distance between the elements is reduced, the influence of interference is seen. In this case, it is about 3%, which is almost no problem. That is, as is apparent from FIG.
The devices are arranged in parallel at intervals of 5 μm or more.
The difference in magnetic flux density of the element can be suppressed to about 3% or less.
It is possible to apply a magnetic field uniformly to each element.
It works.

FIG. 5 shows a thin-film MI sensor 4 (FIG. 1) in which two thin-film MI magnetic cores 5 are arranged in parallel and each thin-film MI magnetic core 5 is electrically connected in series. The thin film MI magnetic cores 5 are arranged in parallel, and each thin film MI
4 shows a magnetic field-impedance characteristic of the thin film MI sensor 4 (FIG. 2) configured by electrically connecting the magnetic cores 5 in series. The measurement current was a sine wave of 20 MHz and 40 mAp-p. In addition, the characteristics in the case of one thin-film MI magnetic core 5 are also shown for comparison. The output value is a thin film with two or three thin film MI magnetic cores 5 connected in series.
The output value of the MI sensor 4 was twice or three times that of a single thin-film MI magnetic core 5.

Next, a second reference example will be described with reference to FIGS. 6 is a plan view showing an arrangement of other elements omitted insulating film structure of the thin film MI sensor 4. The shape of the thin-film MI magnetic core 5 of the thin-film MI sensor 4 has a width of 20.
μm, 3 μm in thickness, and 2000 μm in length. A thin film coil 11 for bias and a thin film coil 12 for negative feedback are three-dimensionally wound around a thin film magnetic core (thin film MI magnetic core 5) via an insulating film 10. I have. The thin film coil 11 for bias and the thin film coil 12 for negative feedback are wound alternately, and the number of turns is respectively
42 turns. Further, Au pads for wire bonding are provided on a part of each electrode portion.

FIG. 7 shows a manufacturing process of the thin film MI sensor 4, which is shown in a cross section along the longitudinal direction in FIG. Next, FIG.
The detailed structure and manufacturing process of the thin film MI sensor 4 will be described with reference to (a) to (e). The thin-film processes are accumulated in order from FIG. 7A to FIG. 7E to manufacture the thin-film MI sensor 4.

FIG. 7A shows a coil lower layer portion (lower coil portion 21) constituting the thin film coil 11 for bias and the thin film coil 12 for negative feedback, and FIG. 7E shows an end portion of each coil portion. Are connected to the coil end of the coil upper layer portion 22 shown in FIG. 1 to form a continuous thin film coil 11 for bias and a thin film coil 12 for negative feedback.

The lower coil portion 21 is formed by forming a Cu sputter film having a thickness of about 50 nm as a seed layer for plating on a non-magnetic substrate 20, such as an Al2O3 ceramic wafer, a Si wafer, or a glass wafer, having improved surface smoothness. After forming a photoresist pattern of a predetermined coil shape reverse pattern on the seed layer, bury Cu plating to a thickness of about 3 μm between the photoresist patterns, and further embed the photoresist pattern. It is formed by removing the seed layer of the Cu sputtered film by etching after removing with an organic solvent or the like. 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. Further, the lower coil portion 21 can be manufactured by removing the photoresist pattern with an organic solvent or the like.

The above-described methods of manufacturing the Cu coil (the thin film coil for bias 11 and the thin film coil 12 for negative feedback) include a method of manufacturing a coil by winding a conductor wire and a method of manufacturing a coil by winding a thin conductor band. In comparison, the coil itself can be reduced in size, and the coil can be made closer to the magnetic core (thin-film MI magnetic core 5), so that the coil efficiency can be increased.

In FIG. 7B, reference numeral 10a denotes an insulating film formed to electrically insulate the lower coil portion and the thin-film magnetic core. The insulating film 10a is obtained by exposing and developing a photoresist to form a predetermined insulating film 10a, and then hardening by performing a heat treatment at 270 ° C. for 10 hours. Further, a resin obtained by curing a resin such as polyimide or a resin obtained by forming an inorganic film such as SiO2 into a predetermined shape may be used.

In FIG. 7C, reference numeral 5 denotes the thin film MI magnetic core, which is composed of NiFe, CoFe, NiFeP, FeNiP, FeCoP, FeNiCoP,
At least one selected from the group consisting of CoB, NiCoB, FeNiCoB, FeCoB and CoFe is formed of a plating film (soft magnetic film). The thin-film MI magnetic core 5 is made of CoZrNb, FeZn.
It may be formed by an amorphous sputtered film (soft magnetic film) formed of either SiB or CoSiB or a NiFe sputtered film (soft magnetic film).

Here, an example in which a NiFe plating film is used as the thin-film MI magnetic core 5 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 predetermined coil shape reverse pattern is formed on the seed layer, then NiFe plating is buried to a thickness of about 3 μm between the photoresist patterns, and the photoresist pattern is further filled with an organic solvent or the like. After removal, the NiFe sputtered film is formed by removing the seed layer by etching. CoFeN
i When the plating film is used as the thin-film MI magnetic core 5, the same process is used. Further, if the heat treatment is performed in a rotating magnetic field and in a static magnetic field after manufacturing the thin-film MI magnetic core 5, the magnetic properties can be improved.

Next, an amorphous sputtered film such as CoZrNb, FeSiB, or CoFeB, or a soft magnetic film such as a NiFe sputtered film is thinned.
A manufacturing process when using as the MI magnetic core 5 will be described.
For example, a CoZrNb sputtered film is formed to a thickness of about 3 μm, a photoresist pattern having a predetermined magnetic core shape is formed, and the photoresist pattern is used as an etching mask, and etching is performed by etching means such as ion milling. Alternatively, the lower coil portion 21 can be manufactured by removing the photoresist pattern with an organic solvent or the like. On the other hand, a predetermined thin-film MI magnetic core 5
There is also a metal mask method in which a reversed metal shape is formed on a thin metal plate and the thin metal plate is used as a sputter mask. However, this method is not preferable because it is difficult to obtain a magnetic core having a fine shape and the dimensional accuracy is poor.

In FIG. 7D, reference numeral 10b denotes an insulating film for electrically insulating the upper coil portion (coil upper portion 22) from the thin-film MI magnetic core 5. The manufacturing method is the same as that of the insulating film 10a shown in FIG.
Is the same as Fig. 7 (e) shows a thin film coil for bias.
11 and a coil upper layer portion 22 constituting the negative feedback thin film coil 12
As shown in the description of FIG. 7A, the end of each coil is connected to the coil end of the coil lower layer (lower coil 21) shown in FIG. The thin film coil 11 for negative feedback and the thin film coil 12 for negative feedback are configured. The fabrication method is the same as that of the coil shown in FIG.

Finally, although not shown, a protective layer for protecting the manufactured magnetic sensor unit and a wire bonding for obtaining an electrical connection between a peripheral circuit for driving and detecting the magnetic sensor are provided. Create a bonding pad. As for the protective layer, a photoresist is exposed and developed in the same manner as the insulating film 10a shown in FIG.
After being formed into the shape of above, it was cured by heat treatment at 270 ° C. for 10 hours. Further, a resin such as polyimide may be cured, or an inorganic film such as SiO2 may be formed in a predetermined shape. The Au pad for wire bonding provided in a part of the electrode portion 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.

Next, the characteristics of the manufactured thin film MI sensor 4 will be described. Here, the dimensions of the thin film MI magnetic core 5 are 20 μm in width.
m, thickness 3 μm, length 2000 μm, and two thin film MI magnetic cores 5 are connected in series. The chip size of the device was 2.3 mm × 0.8 mm. Further, the thin film coil for bias 11 and the thin film coil for negative feedback 12 are alternately wound on the same surface, and the number of turns is 42 turns, respectively. Thin film coil 11 for bias and thin film coil 12 for negative feedback
Are alternately wound around the thin-film MI magnetic core 5 on the same surface, so that a bias magnetic field and a negative feedback magnetic field can be uniformly applied to each part of the thin-film MI magnetic core 5 as a magnetic sensor (thin-film MI sensor 4). Characteristics are stabilized.

The two thin film MI sensors 4 shown in FIG. 6 are arranged so as to be capable of differential drive, and the circuit system of the magnetic sensor is a differential drive circuit 30 shown in FIG.
Was configured. The magnetic sensor 31 for detecting a magnetic field includes two thin film MIs.
An oscillation circuit section 32 for supplying a high-frequency current to the sensor 4 is provided. The differential drive circuit 30 includes diodes D1-1, D1-2, D2-
It comprises a detection circuit section 33 having a detection section (denoted by reference numerals) including D1, D2-2 and the like, and an amplification section 34 for differentially amplifying and outputting a signal from the detection circuit section 33. The output section of the amplification section 34 and the negative feedback thin film coil 12 are connected via a negative feedback section 35, so that the output signal from the amplification section 34 is negatively fed back to the negative feedback thin film coil 12. .

Using the magnetic sensor 31 for magnetic field detection having the above circuit configuration, a sensor (magnetic sensor for magnetic field detection) for an applied magnetic field when a negative feedback with a bias coil magnetic field of 240 (A / m) and a negative feedback rate of 40% is applied. FIG. 9 shows the relationship between the output voltages of 31). Here, the energizing current is a pulse wave having a pulse width of 5 ns, the pulse current is 35 mA, and the amplification of the output is 25 times. As shown in the figure, when two magnetic cores (thin-film MI magnetic cores 5) are arranged in parallel and connected in series, the output is one magnetic core (thin-film MI magnetic core 5) measured for comparison. The output was twice as large as the output. Similarly, the output when three magnetic cores (thin-film MI magnetic cores 5) were arranged in parallel and connected in series also tripled. The chip size at this time was 2.3 mm × 1.2 mm, which was the same as the chip size of one magnetic core.

The sensor characteristics exhibited excellent linearity in a measurement magnetic field of ± 80 (A / m) and a magnetic field resolution of 10 ^-3 (A / m). These results show good characteristics as a linear magnetic field sensor. Further, in the case of a device using a negative feedback coil in which a copper wire is wound around an amorphous wire, about 300% of negative feedback must be applied in order to obtain linearity equivalent to that of FIG. As compared to the negative feedback coil in which a copper wire is wound around an amorphous wire, the thin film coil was able to obtain the same linearity with a negative feedback ratio of about 1/6. Is close to the magnetic core (thin-film MI magnetic core 5), and the coil efficiency of the thin-film coil is increased.

[0055]

According to any one of claims 1 to 4,
According to the described invention, at least two or more thin film magnetic cores are arranged in parallel, and the respective thin film magnetic cores are electrically connected to each other in series, without increasing the chip size of the element. Since the impedance of the magnetic impedance element can be increased, a small and high-output magnetic sensor can be obtained. In addition, there are few thin-film magnetic cores.
At least three or more should be arranged in parallel at intervals of 5 μm or more.
The three or more thin-film magnetic cores
Magnetic interference is practically negligible
To three or more thin-film magnetic cores
Can be applied evenly. Claim 2
According to Ming, the thin-film magnetic core is formed with a thin-film bias coil and a thin-film negative feedback coil via an insulator, enabling the miniaturization and mass production of the magnetic impedance element.
In addition, since the thin-film coil manufactured in the above-described structure has a high coil efficiency, a required bias magnetic field can be obtained with a small current, and 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. Furthermore, a thin film coil for bias,
By alternately winding the negative feedback thin film coil, 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 is a plan view showing a main part of a magneto-impedance element according to a first reference example of the present invention, excluding a coil and an insulating film.

FIG. 2 shows three thin films according to the first embodiment of the present invention .
FIG. 3 is a plan view showing a main part of a magneto-impedance element using an MI core excluding a coil and an insulating film.

FIG. 3 is a plan view showing a main part of a magneto-impedance element using four or more thin-film MI cores according to a second embodiment of the present invention, excluding a coil and an insulating film;

FIG. 4 is a characteristic diagram in which three thin-film MI magnetic cores are arranged in parallel, and when a uniform magnetic field is applied, the magnetic flux density of the inner element with respect to the magnetic flux distance of the outer element and the inner element is expressed as a percentage. .

FIG. 5 is a diagram showing magnetic field-impedance characteristics of a magnetic impedance element having one, two, and three thin-film MI magnetic cores.

FIG. 6 is a plan view for explaining a second reference example .

FIG. 7 is a diagram showing a manufacturing process of the thin-film MI sensor.

FIG. 8 is a circuit diagram showing a magnetic sensor for detecting a magnetic field configured by using two thin film MI sensors shown in FIG. 1;

9 is a diagram showing output voltage characteristics of the magnetic field detecting magnetic sensor of FIG.

FIG. 10 is a diagram showing a magnetic domain model for explaining characteristics of the thin film MI element.

FIG. 11 is a diagram illustrating characteristics of a thin-film MI element.

FIG. 12 is a diagram schematically showing a conventional magnetic impedance element.

FIG. 13 is a diagram showing the applied magnetic field dependence of the impedance change of the magnetic wire of FIG.

[Explanation of symbols]

 4 Thin-film MI sensor (thin-film impedance element) 5 Thin-film MI core (thin-film magnetic core) 6 Non-magnetic conductor

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideki Kato 173-1 Asana-cho, Asaba-cho, Iwata-gun, Shizuoka Prefecture Inside the Minebea Development Technology Center (72) Inventor Akira Goto 1743- Asana-cho, Asaba-cho, Iwata-gun, Shizuoka Prefecture 1 Minebea Co., Ltd. Development Technology Center (56) References JP-A-8-75835 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01R 15/18 G01R 33/02- 33/06 G11B 5/33

Claims (4)

(57) [Claims] 1. A magnetic impedance element comprising a substrate made of a non-magnetic material and a thin-film magnetic core formed on the substrate and provided with electrodes at both ends in the longitudinal direction, wherein at least three or more thin-film magnetic cores are provided. A magneto-impedance element which is arranged in parallel at an interval of 5 μm or more , and wherein the respective thin-film magnetic cores are electrically connected to each other in series. 2. A thin-film bias coil and a thin-film negative feedback coil are formed on the thin-film magnetic core via an insulator, and the thin-film bias coil and the thin-film negative feedback coil are alternately arranged on the same plane at a constant interval in the same direction. 2. The magneto-impedance element according to claim 1, wherein the magnetic impedance element is wound around the same number of times. 3. The thin-film magnetic core is made of NiFe, CoFe, NiFe.
P, FeNiP, FeCoP, FeNiCoP, CoB, NiCoB, FeNiCoB
3. The magneto-impedance element according to claim 1, wherein at least one selected from the group consisting of Fe, Co, and CoFe is formed from a plating film. 4. The thin-film magnetic core comprises CoZrNb, FeSiB,
The magneto-impedance element according to claim 1, wherein the magneto-impedance element is formed of an amorphous sputtered film formed of CoSiB or a NiFe sputtered film.