JP2011047730A - Magnetic field sensor and method of measuring magnetic field using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a magnetic field with high reliability by enabling determination of positive and negative directions. <P>SOLUTION: A magnetic field sensor includes: a ferromagnetic thin film 3; power feed sections 5A, 5B including input/output terminals for supplying an element current to the ferromagnetic thin film; and detection sections 5C, 5D for detecting voltage of the ferromagnetic thin film (between end sections) in a direction orthogonal to the direction of the element current. The ferromagnetic thin film is formed symmetrically to the direction of the element current. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a magnetic field sensor and a magnetic field measurement method using the same, and more particularly to voltage extraction of the magnetic field sensor for realizing high-precision magnetic field measurement without offset.

  A magnetic field sensor is an element that converts an external magnetic field change into an electrical signal. Patterning a magnetic field detection film, such as a ferromagnetic thin film or a semiconductor thin film, and passing a current through the magnetic field detection film pattern changes the external magnetic field as a voltage change. Is converted into an electric signal.

For example, a ferromagnetic magnetoresistive sensor measures the magnetic field strength using a phenomenon (magnetoresistance effect) in which the electrical resistance of a ferromagnetic metal changes due to an external magnetic field.
For example, Patent Document 1 proposes a magnetic field sensor in which a current-carrying portion is formed by opening a part of an annular pattern in order to increase sensitivity.

JP 11-274598 A

For example, as shown in FIG. 16, a current I ₁ is passed through a conductor 200 disposed along the diameter direction of a magnetic thin film 100 having ferromagnetic properties, the magnetic field generated by the current is H, and the spontaneous magnetization of the element is Assuming M, the magnetic flux density vector obtained by combining the magnetic field H and the spontaneous magnetization M of the element is B _M0 , the angle formed by the current density vector and the magnetic flux density vector is θ, and the resistance between the points A and B of the ferromagnetic thin film 100. Is R, and the maximum value of the resistance value between points A and B that changes due to the magnetic field is ΔR,
The voltage V _AB between the points A and B is V _AB = I ₂ (R + ΔR cos 2θ) (1)
It becomes. Here, I is a current density vector, B _M0 is a magnetic flux density vector, and I ₂ is an element current.

However, the above configuration has a problem that the positive / negative direction cannot be determined when an alternating magnetic field is applied. This is because cos 2θ is positive and negative and takes the same value in the above equation (1).
The present invention has been made in view of the above circumstances, and an object of the present invention is to make it possible to determine a positive / negative direction and to detect a magnetic field with high reliability.

In view of this, the magnetic field sensor of the present invention provides a voltage between a magnetic thin film, a power feeding unit having an input / output terminal for supplying an element current to the magnetic thin film, and an end of the magnetic thin film in a direction orthogonal to the direction of the element current. The magnetic thin film is formed so as to be symmetric with respect to the direction of the device current.
According to the above configuration, it is possible to determine whether the direction of the direction of the magnetic thin film is positive or negative by forming the output direction of the magnetic thin film in a direction orthogonal to the element current direction and symmetric with respect to the element current direction. In addition, since there is no offset when no magnetic field is applied, the circuit configuration can be simplified.

According to the present invention, in the magnetic field sensor, the magnetic thin film has a circular outer shape.
According to this configuration, it is possible to provide a highly reliable magnetic field sensor that is symmetrical and can be easily formed to be symmetric with respect to the device current direction.

According to the present invention, in the magnetic field sensor, the magnetic thin film is an annular body.
According to this configuration, since the width of the magnetic thin film is reduced, the electrical resistance is increased, the resistance value can be increased without increasing the outer shape of the element, and the output can be increased.

According to the present invention, in the above magnetic field sensor, the magnetic thin film includes a square annular body, and a power feeding unit is provided so that a current flows in a diagonal direction of the square.
According to this configuration, high sensitivity can be achieved. The output Vmr of the sensor can be expressed by the following equation.
However, the angle between the current density vector and the magnetic flux density vector is θ ₁ , θ ₂ ,
The angle between AB and AC and AB and AD is φ,
The voltage between AC when there is no external magnetic field is V _AC0 , the voltage between AD is V _AD0 ,
Let ΔVr be the maximum value of the voltage change due to the magnetoresistive effect.

  In the circular ring, it can be expressed by substantially the same expression. However, in the case of the circular ring, the direction of the current density vector changes from A to C, and from A to D, and components other than φ = 45 degrees that have the maximum output are also included. Since it exists, the output is smaller than that of the diamond.

In the magnetic field sensor according to the present invention, the magnetic thin film is an annular body and has a constant line width.
According to this configuration, the voltage when no magnetic field is applied becomes equal and the voltage output becomes zero, so that saturation due to offset can be suppressed when amplification is performed in the subsequent circuit, the circuit configuration is simplified, and High-precision magnetic field detection is possible.

According to the present invention, in the magnetic field sensor, the magnetic thin film includes an annular magnetic body provided with an internal magnetic thin film made of a magnetic film.
With this configuration, since a space is formed between the magnetic bodies, sensitivity to an external magnetic field is reduced. Therefore, the sensitivity can be further increased by providing the internal magnetic film independently independently in order to improve only the magnetic sensitivity while increasing the electrical resistance.

According to the present invention, in the magnetic field sensor, the internal magnetic thin film includes a magnetic thin film made of the same material as the magnetic thin film.
According to this configuration, it is possible to provide a magnetic field sensor that is easy to manufacture and has high sensitivity and high reliability only by changing the pattern.

According to the present invention, in the magnetic field sensor, the internal magnetic thin film includes a magnetic thin film different from the magnetic thin film.
According to this configuration, the sensitivity can be adjusted, and when a large number of magnetic field sensors are arranged side by side, the sensitivity can also be adjusted by adjusting the material of the internal magnetic thin film in order to align the sensitivity. It becomes possible.

The magnetic field measuring method of the present invention supplies the element current so that the pattern of the magnetic thin film is symmetric with respect to the direction of the element current, and the magnetic thin film end in a direction orthogonal to the element current supply direction. The magnetic field strength is measured by detecting the voltage between the parts.
According to this configuration, the output direction of the magnetic thin film is set to be a direction orthogonal to the element current direction, and is formed so as to be symmetric with respect to the direction of the element current, thereby determining whether the direction is positive or negative. In addition, since there is no offset when no magnetic field is applied, the circuit configuration can be simplified.

  As described above, according to the present invention, since the voltage is extracted from a point orthogonal to the element current direction with a very simple configuration, the direction of the magnetic field can be detected, there is no offset, and reliability is improved. High magnetic field detection is possible.

Illustration of the principle of the magnetic field sensor of the present invention FIG. 1 is a diagram illustrating the principle of a magnetic field sensor according to Embodiment 1 of the present invention. 1 is a top view of a magnetic field sensor according to a first embodiment of the present invention. Sectional drawing of the magnetic field sensor of Embodiment 1 of this invention FIG. 2 is a circuit explanatory diagram showing a measuring apparatus for measuring element characteristics of the magnetic field sensor according to Embodiment 1 of the present invention. The figure which shows the measurement result of the element characteristic of the magnetic field sensor of Embodiment 1 of this invention The figure which shows the measurement result of the element characteristic of the magnetic field sensor of Embodiment 1 of this invention The figure which shows the relationship between the electric current value and output voltage of the magnetic field sensor of Embodiment 1 of this invention. FIG. 3 is a diagram illustrating the principle of a magnetic field sensor according to a second embodiment of the present invention. The top view of the magnetic field sensor of Embodiment 2 of this invention Sectional drawing of the magnetic field sensor of Embodiment 2 of this invention Sectional drawing of the magnetic field sensor of the modification of Embodiment 2 of this invention The top view of the magnetic field sensor of the modification of Embodiment 2 of this invention Explanatory drawing of the principle of the magnetic field sensor of Embodiment 3 of this invention Top view of a magnetic field sensor according to Embodiment 3 of the present invention. Illustration of a conventional magnetic field sensor

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Prior to the description of the embodiments of the present invention, the measurement principle of the present invention will be described.
In the present invention, the output of the ferromagnetic thin film used as the magnetic thin film is extracted in a direction orthogonal to the element current direction, and is substantially symmetric with respect to the output extraction direction.

  That is, as shown in FIG. 1, the principle A is shown in FIG. 1, and the points A and B on the periphery of the ferromagnetic thin film pattern are symmetrical with respect to the center of the pattern of the circular ferromagnetic thin film 3. The line segments C and D that are orthogonal to the line segment AB and that pass through the center of the circle are used as the output extraction direction.

At this time, as shown in FIG. 1, a current I ₁ is passed through a conductor 200 arranged along the diameter direction of the ferromagnetic thin film 3, the magnetic field generated by the current is H, and the spontaneous magnetization of the element is M. When the magnetic flux density vector obtained by combining the magnetic field H and the spontaneous magnetization M of the element is B _M0 , the angle between the current density vector and the magnetic flux density vector is θ, and the resistance between points A and B of the ferromagnetic thin film 3 is When the maximum value of the resistance value between points A and B that changes due to R and the magnetic field is ΔR, the voltage V _CD between the points _CD can be expressed by the difference between the voltage V _AC and the voltage V _AD .
If you formulate this,
V _CD = I ₂ (ΔR sin 2θ) (5)
Can be expressed as Here, I is a current density vector, B _M0 is a magnetic flux density vector, and I ₂ is an element current.
That is, when an alternating magnetic field is applied, positive / negative can be determined.

Further, compared to the conventional example represented by the expression (1), there is no offset when no magnetic field is applied, and the circuit configuration can be simplified because the offset is zero.
According to this configuration, when the current I ₁ is passed through the conductor 200 arranged along the diameter direction of the ferromagnetic thin film 3, the magnetic field generated by the current is H, and the spontaneous magnetization of the element is M, the magnetic field H The magnetic flux density vector obtained by synthesizing the spontaneous magnetization M of the element is B _M0 , the angle between the current density vector and the magnetic flux density vector is θ, the resistance between points A and B of the ferromagnetic thin film 3 is R, and the magnetic field is When the maximum resistance value between the changing points A and B is ΔR, the voltage V _CD between the points C and D can be expressed by the difference between the voltage V _AC and the voltage V _AD .

(Embodiment 1)
The magnetic field sensor according to the first embodiment will be described. FIG. 2 is a diagram illustrating the principle of the magnetic field sensor, FIG. 3 is a top view, and FIG. 4 is a cross-sectional view. In this magnetic field sensor, as shown in FIGS. 3 and 4, a silicon oxide film is formed as an insulating film 2 on the surface of a substrate 1 made of silicon, and an annular pattern made of a ferromagnetic thin film 3 having ferromagnetic properties is formed on the insulating film 2. , And a detection pattern formed in a direction orthogonal to the direction of the element current supplied from the power supply units 5A and 5B along the diameter direction of the annular pattern. And 5C and 5D conductor patterns.

  In other words, as shown in FIG. 2, the principle explanatory diagram is shown, and the points A and B on the periphery of the ferromagnetic thin film pattern are symmetrical with respect to the center of the circular ferromagnetic thin film 3 pattern. The line segments C and D that are orthogonal to the line segment AB and that pass through the center of the circle are used as the output extraction direction.

At this time, as shown in FIG. 2, a current I ₁ is passed through a conductor 200 arranged along the diameter direction of the ferromagnetic thin film 3, the magnetic field generated by the current is H, and the spontaneous magnetization of the element is M. When the magnetic flux density vector obtained by combining the magnetic field H and the spontaneous magnetization M of the element is B _M0 , the angle between the current density vector and the magnetic flux density vector is θ, and the resistance between points A and B of the magnetic thin film 3 is R When the maximum resistance value between points A and B that changes due to the magnetic field is ΔR, the voltage V _CD between the points _CD can be expressed by the difference between the voltage V _AC and the voltage V _AD .
Therefore, the above equation (5) holds, and when an alternating magnetic field is applied, it is possible to determine whether it is positive or negative.
In addition, there is no offset when no magnetic field is applied, and the circuit configuration can be simplified because it is zero.

Here, as the ferromagnetic thin film, in addition to a ferromagnetic thin film having a single layer structure, an antiferro (coupled) thin film having a (ferromagnetic / nonmagnetic conductor) structure, (high coercivity ferromagnetic / nonmagnetic conductor / Inductive ferri (non-coupled) type thin film with a low coercivity ferromagnet structure, spin valve type thin film with a (semi-ferromagnetic material / ferromagnetic material / non-magnetic conductor / ferromagnetic material) structure, non-Co / Ag family It is formed by selecting from a solid solution granular thin film.
As the conductor pattern, gold, copper, aluminum or the like is used.

Next, the manufacturing process of this magnetic field sensor will be described.
A silicon oxide film as the insulating film 2 is formed on the surface of the silicon substrate as the substrate 1, and a ferromagnetic thin film 3 is formed thereon by sputtering. At this time, sputtering is performed while applying a magnetic field so that the spontaneous magnetization directions are aligned.
Then, the ferromagnetic thin film 3 is patterned by photolithography to form an annular pattern.
After that, a conductive thin film such as gold is formed by sputtering, and patterned by photolithography to form power supply portions 5A and 5B and detection portions 5C and 5D as shown in FIGS.
And a protective film is formed as needed and a magnetic field sensor is completed.

  According to the magnetic field sensor of the present embodiment, since the width of the magnetic thin film is reduced, the electrical resistance is increased and the output can be increased.

In order to confirm the output characteristics of this magnetic field sensor, an experiment was conducted using a measuring apparatus as shown in FIG. AC is supplied from the AC power supply 507 through the transformer 506 and the resistor 505 to the power supply unit AB of the magnetic field sensor 501 shown in FIGS. 2 to 4, and the display unit is connected to the detection unit CD of the magnetic field sensor 501 through the amplifier 502. Is connected to an oscilloscope 504. Reference numeral 503 denotes a stabilized power source. This measuring device is housed in an iron casing 500. Here, the measurement was performed with the element substrate on which this element was mounted arranged vertically, and the distance between the element and the current line to be measured was about 3 mm.
The measurement results are shown in FIGS. FIG. 6 shows the instantaneous output when the device current I1 is 8.842A, and FIG. 7 shows the instantaneous output when the device current I1 is 0A.

  FIG. 8 shows the relationship between the current value thus obtained and the element output voltage. Here, the offset by the amplifier is 5.888 V, but otherwise there is no offset and the reliability is high.

  In the above-described embodiment, the measurement using the element substrate arranged in the vertical direction has been described. However, the measurement may be performed by placing the electric wire to be measured on the element substrate.

  In the embodiment, it is desirable that the line width is constant. If it is not constant, it is also effective to adjust the film thickness or add an auxiliary pattern so that the resistance values are symmetric.

(Embodiment 2)
Next, a second embodiment of the present invention will be described. In the present embodiment, as shown in FIGS. 9 to 11, a circular strong force that is similar to the inner periphery of the ring of the ferromagnetic thin film 3 constituting the annular pattern of the magnetic field sensor of the first embodiment. The magnetic thin film auxiliary pattern 4 is formed. As the configuration, only the auxiliary pattern 4 is added, and the other configuration is the same as that of the first embodiment, and the description is omitted here. The same symbols are assigned to the same parts. FIG. 9 is an explanatory diagram of the principle of the magnetic field sensor, FIG. 10 is a top view, and FIG. 11 is a cross-sectional view. This magnetic field sensor is basically the same as in the first embodiment, but the presence of the auxiliary pattern 4 increases the magnetic sensitivity while keeping the electrical resistance high. Since the outer annular pattern (3) and the inner auxiliary pattern 4 are not in electrical contact, the electrical resistance is the same as that of the magnetic field sensor of the first embodiment, but magnetically, the space portion is a magnetic thin film. Therefore, more magnetic flux can be guided and higher sensitivity can be achieved.

  As an element structure, as shown in FIG. 12, the entire surface of the substrate is covered with a protective insulating film 16 made of polyimide resin after the magnetic thin film pattern is formed, and the power feeding portions 5A and 5B are formed through the through holes. Further, the detection units 5C and 5D may be formed. According to this configuration, it is possible to provide a highly reliable magnetic field sensor that prevents deterioration of the magnetic thin film.

  Furthermore, the auxiliary pattern formed inside the annular pattern may be made of the same material, or the auxiliary pattern 24 may be formed of a magnetic thin film made of another material as shown in FIG. .

  Note that as the protective film, an organic film such as a polyimide resin or a novolac resin can be used in addition to an inorganic film such as a silicon oxide film or aluminum oxide.

(Embodiment 3)
Next, a third embodiment of the present invention will be described. In the present embodiment, as shown in FIGS. 14 and 15, the ferromagnetic thin film is formed of a square annular pattern 33, and power supply portions 5 </ b> A and 5 </ b> B are provided so that a current flows in the diagonal direction of the square. The detection portions 5C and 5D are formed in a direction orthogonal to the above.
Also in the present embodiment, only the square annular pattern 33 is formed in place of the annular pattern 3 of the magnetic field sensor of the first embodiment, and other configurations are the same as those of the first embodiment, and will be described here. Is omitted. The same symbols are assigned to the same parts. Here, FIG. 14 is a diagram illustrating the principle of this magnetic field sensor, and FIG. 15 is a top view.

Here, the magnetic flux density vector is a combination of the spontaneous magnetization vector M and the external magnetic field vector H possessed by the element. When there is no external magnetic field, the magnetic flux density vector is in the direction of the spontaneous magnetization vector.
When the external magnetic field is an alternating magnetic field, it vibrates in the vertical direction in the figure around the spontaneous magnetization vector.

According to this configuration, the output Vmr of the sensor can be expressed by the following equation.
However, the angle between the current density vector and the magnetic flux density vector is θ ₁ , θ ₂ ,
The angle formed by AB and AC and AB and AD is φ,
The voltage between AC when there is no external magnetic field is V _AC0 , the voltage between AD is V _AD0 ,
Let ΔVr be the maximum value of the voltage change due to the magnetoresistive effect.
As previously mentioned,

  In the case of an annular shape, the direction of the current density vector changes from A to C, and from A to D, and the maximum output is not φ = 45 degrees. The output is smaller than that of the square.

  In the above embodiment, the magnetic thin film is formed by the sputtering method. However, the magnetic thin film is not limited to the sputtering method, and can be formed by a vacuum deposition method, a coating method, a dipping method, or the like.

  As for the substrate, in addition to a semiconductor substrate such as silicon, an inorganic substrate such as sapphire, glass, or ceramic, or an organic substrate such as resin may be used. Among these, it is particularly preferable to use a thin and light material excellent in so-called flexibility. For example, a substrate similar to a plastic film widely used as a printed wiring board or the like can be used. More specifically, various known materials as plastic film materials, such as polyimide, polyethylene terephthalate (PET), polypropylene (PP), and Teflon (registered trademark) can be used. By using a flexible substrate, it can be arranged so as to have higher sensitivity, for example, so as to surround an electric wire to be measured. In consideration of bonding with solder, a polyimide film having high heat resistance may be used. The thickness of the substrate is not particularly limited, but is preferably about 1 to 300 μm.

  Furthermore, a magnetic thin film pattern may be formed directly on a substrate such as a glass substrate to form a magnetic field sensor, but once a chip is formed, this is applied to a glass substrate or a printed wiring board using a wire bonding method, You may make it mount by the flip-chip method. Further, by integrating the processing circuit in the chip, it becomes possible to provide a magnetic field sensor with higher accuracy and reliability.

The present invention is not limited to the above embodiment, and the magnetic thin film is formed so that the output extraction direction of the magnetic thin film is perpendicular to the element current direction and the magnetoresistance is symmetric with respect to the element current direction. The circuit configuration can be simplified because it is possible to determine whether the direction is positive or negative, and there is no offset when no magnetic field is applied.
Moreover, although the magnetic field sensor using a ferromagnetic thin film was used in the said embodiment, you may use another magnetic field sensor, without being limited to this.

  As described above, according to the magnetic field sensor of the present invention, it is possible to detect the magnetic field strength with high accuracy, and therefore it can be applied to a current sensor, a power sensor, and the like.

1 Substrate 2 Insulating film 3, 33 Ferromagnetic thin film ((annular) pattern)
4, 24 Auxiliary pattern 5A, 5B Power supply unit 5C, 5D Detection unit 100 Ferromagnetic thin film 200 Conductor

Claims (9)

A magnetic thin film;
A power feeding unit having an input / output terminal for supplying an element current to the magnetic thin film;
A detection unit for detecting a voltage between the end portions of the magnetic thin film in a direction orthogonal to the direction of the element current;
The magnetic thin film is formed so that the magnetic thin film is symmetric with respect to the direction of the element current. The magnetic field sensor according to claim 1,
The magnetic thin film has a circular outer shape. The magnetic field sensor according to claim 1 or 2,
The magnetic thin film is a magnetic field sensor having an annular body. The magnetic field sensor according to claim 3,
The magnetic thin film includes a square annular body, and a magnetic field sensor provided with a power feeding unit so that a current flows in a diagonal direction of the square. The magnetic field sensor according to claim 3,
The magnetic thin film is a magnetic field sensor having a constant line width. The magnetic field sensor according to any one of claims 2 to 5,
The magnetic thin film is a magnetic field sensor in which an internal magnetic thin film made of a magnetic film is provided inside the annular body. The magnetic field sensor according to claim 6,
The internal magnetic thin film is a magnetic field sensor composed of a magnetic thin film made of the same material as the magnetic thin film. The magnetic field sensor according to claim 6,
The internal magnetic thin film is a magnetic field sensor formed of a magnetic thin film different from the magnetic thin film. Magnetic thin film pattern
The device current is supplied so as to be symmetric with respect to the direction of the device current,
A magnetic field measurement method for measuring a magnetic field strength by detecting a voltage between the end portions of the magnetic thin film in a direction orthogonal to a supply direction of the element current.

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