JP7057680B2 - Magnetic sensor and current sensor - Google Patents

Description

The present invention relates to a magnetic sensor and a current sensor including the magnetic sensor.

In fields such as motor drive technology for electric vehicles and hybrid cars, and in infrastructure-related fields such as pole transformers, relatively large currents are handled, so there is a need for current sensors that can measure large currents in a non-contact manner. There is. As such a current sensor, one using a magnetic sensor that detects an induced magnetic field from a measured current is known. Examples of the magnetic detection element for a magnetic sensor include a magnetoresistive element such as a GMR (giant magnetoresistive effect) element.

Although the magnetoresistive sensor has high detection sensitivity, it is characterized by high linearity and a relatively narrow range of detectable magnetic field strength. Therefore, as in the current sensor shown in FIG. 3 of Patent Document 1, a magnetic shield is arranged between the measured current and the magnetoresistive sensor, and an induced magnetic field substantially applied to the magnetoresistive sensor. In some cases, a method of reducing the strength of the magnetic field to be measured so that the magnitude of the measured magnetic field is within the magnetic field strength range having good detection characteristics is used. By using the magnetic shield in this way, it is possible to substantially reduce the strength of the magnetic field applied to the magnetoresistive sensor and expand the measurement range of the magnetic field strength.

International Publication No. 2011/111493

The effect of reducing the magnetic field strength is enhanced by providing a magnetic shield at a position close to the magnetoresistive sensor. However, when the magnetic field applied to the magnetic shield is as strong as about several tens of mT, residual magnetization is likely to occur in the magnetic shield even if the magnetic shield is made of a soft magnetic material. When a magnetic field based on the residual magnetization of the magnetic shield generated in this way is applied to the magnetoresistive sensor, the zero magnetic field hysteresis of the magnetoresistive sensor increases to the negative side, which adversely affects the measurement accuracy of the magnetoresistive sensor. There is a risk. Further, when a strong magnetic field is applied to the magnetic shield, there is also a problem that the resistance of the magnetoresistive effect element deviates from a predetermined value due to the hysteresis of the free magnetic layer.

In view of the present situation, the present invention is a magnetic sensor including a magnetic shield and a magnetic resistance effect element, and the residual magnetic shield applied in a direction parallel to the sensitivity axis of the magnetic resistance effect element due to a magnetic field applied to the magnetic sensor. It is an object of the present invention to provide a magnetic sensor having high resistance to a quadrature magnetic field applied in a direction orthogonal to the sensitivity axis of a magnetic resistance effect element while suppressing the influence of magnetization. It is also an object of the present invention to provide a current sensor including such a magnetic sensor.

The present invention provided to solve the above problems, in one embodiment, comprises a plurality of magnetic resistance effect elements having a sensitivity axis in a first direction and a plurality of magnetic resistance effect elements spaced apart from each other. A magnetic sensor including a magnetic shield that attenuates the strength of the magnetic field to be measured applied to the magnetic resistance effect element, wherein the magnetic shield is a magnetic attraction that protrudes toward the main body and the magnetic resistance effect element. The main body portion has a portion having a portion and has a shape having a length in a second direction orthogonal to the first direction in a plan view, and overlaps with all of the plurality of the magnetic resistance effect elements to absorb the suction. A magnetic sensor characterized in that magnetic portions are provided at both ends in the second direction, and the tip portions thereof are provided at positions separated from the plurality of magnetic resistance effect elements in a plan view. be. With this configuration, the magnetic attraction portion of the magnetic shield absorbs the orthogonal magnetic field in the direction orthogonal to the sensitivity axis, so that the magnetic sensor has high resistance to the orthogonal magnetic field.

The effect of the recirculation magnetic field due to the residual magnetization of the magnetic shield is that the plurality of the magnetoresistive effect elements are provided at equal distances from the pair of ends of the magnetic shield located in the first direction in a plan view. It is preferable from the viewpoint of suppressing.

Each of the plurality of magnetoresistive elements is a GMR element having a meander shape, and the fact that a bias magnetic field is applied to the free magnetic layer of the GMR element causes bulkhausen noise due to the movement of the magnetic domain wall inside the free magnetic layer. It is preferable from the viewpoint of suppressing.

The magnetic sensor may further include a magnetic equilibrium coil and measure the strength of the magnetic field to be measured based on the current flowing through the magnetic equilibrium coil. In this case, the magnetic equilibrium coil is a spiral coil, and it may be preferable that the coil is located between the magnetoresistive sensor and the magnetic shield.

As another aspect of the present invention, the magnetic sensor is provided, and the magnetic sensor provides a current sensor in which the induced magnetic field of the measured current is the measured magnetic field.

According to the present invention, it is possible to reduce the influence of the orthogonal magnetic field in the direction orthogonal to the sensitivity axis on the magnetoresistive effect element while suppressing the influence of the residual magnetization of the magnetic shield generated in the direction parallel to the sensitivity axis. Therefore, a magnetic sensor is provided in which the measurement accuracy of the magnetoresistive effect element is unlikely to decrease. Further, a current sensor using such a magnetic sensor is also provided.

It is a top view which conceptually shows the structure of the magnetic sensor which concerns on one Embodiment of this invention. It is sectional drawing by V1-V1 line of FIG. It is a top view which conceptually shows the structure of the magnetic sensor which concerns on another Embodiment of this invention. FIG. 3 is a cross-sectional view taken along the line V2-V2 of FIG. It is sectional drawing which shows typically the laminated structure which a GMR element has. It is a graph which shows the external magnetic field resistance of the magnetic sensor in an Example. It is a graph which shows the external magnetic field resistance of the magnetic sensor in the comparative example. It is explanatory drawing explaining the offset of the resistance of a free magnetic layer due to hysteresis.

An offset generated in the free magnetic layer of a GMR element (giant magnetoresistive element) used as a magnetoresistive element of a magnetic field detection device such as a current sensor or a geomagnetic sensor will be described.

FIG. 5 is a cross-sectional view schematically showing a laminated structure included in the GMR element. As shown in the figure, the GMR element 30 has a configuration in which a fixed magnetic layer 31, a non-magnetic layer 32, and a free magnetic layer 33 are laminated. The resistance value changes depending on the relative relationship between the fixed magnetic layer 31 in which the magnetization direction is fixed and the free magnetic layer 33 in which the magnetization direction changes due to an external magnetic field. By detecting this change in resistance value, the direction and strength of the external magnetic field can be detected.

When the magnetic domain wall moves inside the free magnetic layer 33 formed of the soft magnetic material, Barkhausen noise is generated. Therefore, a bias magnetic field for stabilizing the output of the current sensor provided with the GMR element 30 and an exchange bias magnetic field using an exchange coupling magnetic field with the antiferromagnetic layer 34 are applied in a direction orthogonal to the sensitivity axis. By applying a bias magnetic field to the free magnetic layer, the magnetization directions of the soft magnetic materials can be aligned. Instead of the exchange bias magnetic field, a permanent magnet may be used to apply a hard bias magnetic field.

If the external magnetic field has a magnitude such that the magnetization direction of the free magnetic layer is not reversed, the free magnetic layer 33 returns to the initial state before the external magnetic field is applied by returning to the zero magnetic field without the external magnetic field. However, when a strong external magnetic field is applied and the magnetization direction of the free magnetic layer 33 is reversed from the initial magnetization direction, the free magnetic layer 33 cannot return to the initial state even if it returns to the zero magnetic field. That is, when the magnetization direction of the free magnetic layer 33 is reversed from the initial magnetization direction due to a strong external magnetic field, even if the strong external magnetic field is removed and the magnetic field returns to zero, the free magnetic layer 33 does not return to the initial state due to the hysteresis. , A deviation (offset) from the initial state occurs.

FIG. 8 is an explanatory diagram illustrating the offset of the resistance due to the hysteresis of the free magnetic layer. As shown in the figure, when the external magnetic field applied in the direction orthogonal to the sensitivity axis with respect to the free magnetic layer is smaller than the inversion magnetic field B, when the external magnetic field returns to zero, the free magnetic layer is arrowed along the solid line. It changes in the direction of (1) and returns to the initial state A. Therefore, when the magnitude of the external magnetic field is from 0 to less than the inverting magnetic field B, the resistance of the free magnetic layer becomes the initial resistance when the external magnetic field becomes zero.

However, when an external magnetic field of inverting magnetic field B or higher is applied to the free magnetic layer, the free magnetic layer does not return to the initial state A even if the external magnetic field returns to zero. For example, when the saturated magnetic field C is applied to the free magnetic layer, when the external magnetic field becomes zero, the free magnetic layer changes in the direction of the arrow (2) along the broken line, and the state D after the saturated magnetic field C is applied. Will be. As described above, when the magnitude of the external magnetic field is equal to or larger than the inversion magnetic field B, the resistance of the free magnetic layer deviates from the initial value due to the hysteresis of the free magnetic layer.

As described above, when an external magnetic field larger than the inverting magnetic field B is applied and the free magnetic layer is inverted from the initial magnetization direction, the resistance of the free magnetic layer is offset after becoming a zero magnetic field. The offset of the resistance of the free magnetic layer fluctuates depending on the magnitude of the external magnetic field, and fluctuates in the range indicated by the white arrow in FIG. When the resistance of the free magnetic layer fluctuates due to an external magnetic field, the accuracy of the magnetic sensor decreases.

Therefore, in order to improve the accuracy of the magnetic sensor, a magnetic shield that attenuates an external magnetic field is used. Since the external magnetic field applied to the GMR element by the magnetic shield becomes small, the inverted magnetic field B in which the free magnetic layer is inverted shifts to the high magnetic field side, and the range in which the accuracy of the magnetic sensor can be maintained satisfactorily becomes wide.

From the viewpoint of attenuating the external magnetic field, the magnetic shield is preferably provided at a position close to the magnetoresistive element such as the GMR element. However, if the distance between the magnetic shield and the magnetoresistive sensor is short, the influence of the recirculation magnetic field due to the residual magnetization of the magnetic shield becomes large, which leads to a decrease in the accuracy of the magnetic sensor. Therefore, the magnetic sensor of the present invention is provided with a magnetic absorption unit that absorbs an external magnetic field (orthogonal magnetic field) at a position distant from the magnetoresistive sensor in a direction orthogonal to the sensitivity axis of the magnetoresistive sensor in a plan view. With this configuration, a magnetic shield is provided at a position far away from the magnetoresistive effect element to reduce the influence of the recirculation magnetic field, and the reversal magnetic field in the direction orthogonal to the sensitivity axis can be shifted to the high magnetic field side.

FIG. 1 is a plan view conceptually showing the structure of a magnetic sensor according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line V1-V1 of FIG.

As shown in FIGS. 1 and 2, the magnetic sensor 1 according to an embodiment of the present invention includes four magnetoresistive elements (magnetoresistive elements 11 to 14) and a magnetic shield 15.

Each of the four magnetoresistive elements of the magnetic sensor 1 according to the embodiment of the present invention has a meander shape (a shape formed by connecting a plurality of long patterns extending in the X1-X2 direction so as to be folded back). It is equipped with a giant magnetoresistive effect element (GMR element). The sensitivity axis direction P of each magnetoresistive effect element (magnetic resistance effect element 11 to 14) is represented by an arrow in FIG. 1, and has a sensitivity axis in the Y1-Y2 direction (first direction). .. Here, having a sensitivity axis in the Y1-Y2 direction means having a sensitivity axis direction P toward the same side (parallel direction) or the opposite side (anti-parallel direction) along the Y1-Y2 direction. As shown in FIG. 1, the sensitivity axial direction P (first direction) of the magnetoresistive effect element 11 and the magnetoresistive element 14 faces the Y2 side in the Y1-Y2 direction, and the magnetoresistive effect element 12 and the magnetoresistive element 13 face. The sensitivity axis direction P of is set to face the Y1 side in the Y1-Y2 direction.

The wiring 5 connected to the input terminal 5a is connected to one end of the magnetoresistive element 11, and the other end of the magnetoresistive element 11 and one end of the magnetoresistive element 12 are connected in series to form the magnetoresistive element 12. The other end of the is connected to the ground terminal 6a via the wiring 6. The wiring 5 connected to the input terminal 5a branches in the middle and is also connected to one end of the magnetoresistive sensor 13, and the other end of the magnetoresistive element 13 and one end of the magnetoresistive element 14 are connected in series. The other end of the magnetoresistive sensor 14 is connected to the ground terminal 6a via the wiring 6. The first midpoint potential measuring terminal 7a is connected by a wiring 7 between the other end of the magnetoresistive effect element 11 and one end of the magnetoresistive effect element 12, and the second midpoint potential measuring terminal 8a is a magnetic resistance. It is connected by a wiring 8 between the other end of the effect element 13 and one end of the magnetoresistive effect element 14. By comparing the potential of the first midpoint potential measuring terminal 7a with the potential of the second midpoint potential measuring terminal 8a, the induced magnetic field (measured magnetic field) of the measured current Io flowing through the current line 40 The strength and orientation can be measured.

FIG. 2 is obtained by cutting the magnetic sensor 1 at a plane whose normal is the direction along the short axis direction (Y1-Y2 direction) of a plurality of long patterns constituting the meander shape of the magnetoresistive effect element 11. It is a cross-sectional view. The Y1-Y2 direction (first direction), which is one of the normal directions, is the sensitivity axis direction P (direction on the Y1-Y2 direction Y2 side) of the magnetoresistive effect element 11. From the magnetoresistive element 11 to the magnetoresistive element 14, the magnetoresistive element 14 is formed on the substrate 29 and is covered with an insulating layer IM made of an insulating material (alumina, silicon nitride or the like is mentioned as a specific example).

The magnetic shield 15 is arranged on the magnetoresistive effect element 14 (Z1-Z2 direction Z1 side) from the magnetoresistive effect element 11 so as to be separated from these four magnetoresistive effect elements. In this specification, for convenience of explanation, the Z1 side of the four magnetoresistive elements in the Z1-Z2 direction is referred to as "upper", and the Z2 side in the Z1-Z2 direction is referred to as "lower". The separation distance between the magnetic shield 15 and the four magnetoresistive elements is adjusted by the thickness of the insulating layer IM located between them.

In the magnetic sensor 1 according to the embodiment of the present invention, the magnetic shield 15 attenuates the strength of the measured magnetic field applied from the magnetoresistive element 11 to the magnetoresistive element 14, and is shown in FIG. As described above, the main body 150 having a rectangular shape having a length in the second direction (X1-X2 direction) orthogonal to the first direction (Y1-Y2 direction) in a plan view (viewed from the Z1-Z2 direction). It has four magnetic resistance effect elements 15P protruding toward the element side (Z1-Z2 direction Z2 side). As shown in FIG. 2, the magnetic attraction portions 15P are provided at both ends of the main body portion 150 in the X1-X2 direction (second direction). The magnetic shield 15 is made of a soft magnetic material.

As shown in FIGS. 1 and 2, the main body 150 is a rectangle having a length in the X1-X2 direction (second direction) orthogonal to the Y1-Y2 direction (first direction) in a plan view. It overlaps with all four magnetoresistive effect elements. The tip portion 15PE, which is the tip of the magnetic attraction portion 15P on the Z2 side in the Z1-Z2 direction, is provided at a position separated from the four magnetoresistive elements in the X1-X2 direction in a plan view.

Since the magnetic attraction portion 15P is provided, the distance between the forming surface of the four magnetoresistive elements on the substrate 29 and the magnetic shield 15 is four magnetisms rather than the distance D1 directly above the four magnetoresistive elements. The distance D2 outside the resistance effect element is smaller. Therefore, the external magnetic field M in the X1-X2 direction orthogonal to the sensitivity axis direction P is absorbed from the tip portion 15PE of the magnetic attraction portion 15P and guided to the magnetic shield 15, and the magnetic shield 15 is used as the path of the external magnetic field M. be able to. Therefore, the influence of the external magnetic field M on the four magnetoresistive effect elements can be suppressed. Further, since the distance D1 is larger than that without the magnetic attraction portion 15P, the influence of the residual magnetization of the magnetic shield 15 on the four magnetoresistive effect elements in the sensitivity axial direction P (Y1-Y2 direction) can be suppressed. Can be done.

Examples of the above-mentioned distance D1 without limitation include 5 μm or more and 13 μm or less, and 8 μm or more and 10 μm or less may be preferable. Further, examples of the above-mentioned distance D2 without limitation include 4 μm or more and 10 μm or less, and 5 μm or more and 8 μm or less may be preferable.

Since the main body 150 has a second direction (X1-X2 direction) as a longitudinal direction, it is difficult to magnetize in the first direction (Y1-Y2 direction), which is short, due to the shape magnetic anisotropy effect, but it is external. When the magnetic field is strong, remanent magnetization may occur in the first direction (Y1-Y2 direction). Even in such a case, the distance D1 between the main body 150 and the four magnetoresistive elements can be increased to suppress the influence of the residual magnetization, so that the magnetic sensor 1 has good measurement accuracy.

As shown in FIG. 1, it is preferable that the four magnetoresistive effect elements are provided at positions where the distances from the pair of ends 15E and 15E located in the Y1-Y2 direction of the magnetic shield 15 are equal. With this configuration, the influence of the magnetic field based on the residual magnetization of the magnetic shield 15 on the four magnetoresistive effect elements can be made equal. The "distance from the terminal 15E" means the distance from the terminal 15E to the center point of each magnetoresistive sensor in the Y1-Y2 direction.

In a plan view (when viewed from the Z1-Z2 direction), all four magnetoresistive effect elements overlap with the main body 150 of the magnetic shield 15. That is, in a plan view, the magnetic absorption portion 15P is provided at a position separated from the plurality of magnetoresistive elements in the X1-X2 direction. Therefore, it is possible to suppress the influence of the magnetic attraction portion 15P provided on the magnetic shield 15 on the magnetoresistive effect element 11 and the magnetoresistive effect element 13 at both ends of the four magnetoresistive effect elements.

As an example without limitation of the distance L11 between the magnetic attraction portion 15P and the magnetoresistive element 11 and the distance L13 of the magnetoresistive element 13 in a plan view, 30 μm or more and 300 μm or less can be mentioned, and 50 μm or more and 250 μm or less may be preferable. There are cases where 100 μm or more and 200 μm or less are more preferable. From the viewpoint of equalizing the influence of the magnetic attraction portion 15P, it is preferable that the distance L11 and the distance L13 are equal.

The magnetic shield 15 is made of a soft magnetic material containing iron group elements such as Fe, Co, and Ni. The thickness of the magnetic shield 15 is arbitrarily set within the range in which the magnetic shield 15 has a predetermined magnetic shielding function. An example in which the thickness of the magnetic shield 15 is not limited is 1 μm or more and 50 μm or less, and the thickness of the magnetic shield 15 may be preferably 5 μm or more and 30 μm or less, and more preferably 10 μm or more and 25 μm or less. The width W of the magnetic attraction portion 15P, that is, the distance between both ends in the X1-X2 direction is, for example, 2 μm or more and 15 μm or less, and suppresses the influence of the external magnetic field M orthogonal to the sensitivity axis direction P on the four magnetoresistive elements. From the viewpoint, it is preferably 3 μm or more and 10 μm or less, and more preferably 5 μm or more and 8 μm or less.

As described above, in order to suppress the influence of the residual magnetization of the magnetic shield 15, it is preferable to increase the distance D1 between the magnetic shield 15 and the four magnetoresistive elements. However, if the magnetic shield 15 is provided at a position away from the plurality of magnetoresistive effect elements in order to satisfy this requirement, the function of shielding the external magnetic field of the magnetic shield 15 is deteriorated. Therefore, as described above, magnetic attraction portions 15P extending toward Z2 in the Z1-Z2 direction are provided at both ends of the main body portion 150 in the X1-X2 direction. With this configuration, while shielding the external magnetic field M orthogonal to the sensitivity axis direction P, both ends of the magnetic shield 15 in the X1-X2 directions are positioned far from the plurality of magnetoresistive elements to suppress the influence of residual magnetization. Is possible.

By using the magnetic shield 15 provided with the magnetic attraction portion 15P, the strength of the recirculated magnetic field applied to the four magnetoresistive effect elements is reduced, and the influence of the external magnetic field M orthogonal to the sensitivity axis direction P is suppressed. It is possible to achieve both. As a result, even if a strong magnetic field is applied to the magnetic sensor 1 from the outside and a residual magnetic field is generated in the magnetic shield 15, the external magnetic field M orthogonal to the sensitivity axis direction P is reduced while reducing the influence of the reflux magnetic field generated by the residual magnetic field. It can be expected that the magnetic sensor 1 will suppress the influence of the above and suppress the offset of the resistance of the free magnetic layer.

An oxidation protection layer PL made of tantalum (Ta) or the like is formed on the magnetic shield 15 shown in FIG. 1 (Z1 side in the Z1-Z2 direction).

The method of manufacturing the magnetic shield 15 is arbitrary. As an example without limitation, a base layer is formed by a dry process such as sputtering or a wet process such as electroplating, a resist layer patterned in a predetermined shape is formed on the base layer, and then the exposed base layer is formed. The soft magnetic layer may be formed by electroplating after the step 20 (see FIG. 2) is formed on the portion to be the main body portion 150 using gold or the like.

FIG. 3 is a plan view conceptually showing the structure of the magnetic sensor according to another embodiment of the present invention. FIG. 4 is a sectional view taken along line V2-V2 of FIG. The magnetic sensor 1A shown in FIGS. 3 and 4 includes four magnetoresistive elements and a magnetic shield 15 similar to the magnetic sensor 1 shown in FIG. 1, and further includes four magnetoresistive elements and a magnetic shield 15. A magnetic equilibrium coil (spiral coil) 16 having a spiral shape is provided between the two. In FIG. 3, the outer shape of the magnetic equilibrium coil 16 is shown by a thick broken line. The coil wiring is arranged so as to orbit in the XY plane of the region indicated by the broken line. In FIG. 4, a cross section of a plurality of rotating coil wirings in the magnetic equilibrium coil 16 is shown extending in the X1-X2 direction. The magnetic equilibrium coil 16 is located between the magnetoresistive effect element 11 and the magnetic shield 15, so that an induced magnetic field that cancels an external magnetic field applied in a state of being attenuated by the magnetic shield 15 is generated with a relatively small current. Can be caused by. Therefore, it is possible to operate the magnetically balanced magnetic sensor with low power consumption.

In the above embodiment, the case where the magnetoresistive effect element 14 to the magnetic resistance effect element 11 included in the magnetic sensors 1 and 1A is composed of a GMR element is taken as a specific example, but the present invention is not limited to this. In one example without limitation, the magnetoresistive element is one selected from the group consisting of an anisotropic magnetoresistive element (AMR element), a giant magnetoresistive element (GMR element), and a tunnel magnetoresistive element (TMR element). It consists of the above elements.

When the fixed magnetic layer of each GMR element constituting the magnetic resistance effect element 11 to the magnetic resistance effect element 14 included in the magnetic sensor 1 has a self-pin structure, the fixation of the fixed magnetic layer is performed by film formation in a magnetic field. It can be and does not require heat treatment in a magnetic field after film formation. Therefore, GMR elements having different magnetization directions of the fixed magnetic layer can be arranged on the same substrate, and a full bridge circuit can be configured on one substrate.

The magnetic sensors 1, 1A provided with the magnetoresistive element according to the embodiment of the present invention can be suitably used as a current sensor.

Specific examples of the current sensor according to the embodiment of the present invention include a magnetically proportional current sensor and a magnetically balanced current sensor.

A specific example of the magnetic proportional current sensor is a magnetic proportional current sensor 2 using the magnetic sensor 1 shown in FIGS. 1 and 2. In such a current sensor, the upper part of FIG. 2 (Z1 side in the Z1-Z2 direction). In, the current line 40 through which the measured current Io flows is located so as to extend in the X1-X2 direction (see FIG. 1). The induced magnetic field of the measured current Io, which is the measured magnetic field, is applied to the four magnetoresistive elements in the direction along the sensitivity axis direction P (Y1-Y2 direction). Since a part of the measured magnetic field passes through the magnetic shield 15 having a higher magnetic permeability, the strength of the measured magnetic field substantially applied to the four magnetoresistive effect elements can be reduced. Therefore, it is possible to expand the measurement range of the magnetic sensor 1.

In a preferred example, the magnetic proportional current sensor 2 includes four magnetoresistive effect elements (magnetoresistive element 11 to 14), and has a potential difference according to a measured magnetic field composed of an induced magnetic field of the measured current Io. A magnetic sensor 1 having a magnetic field detection bridge circuit with two outputs is used (see FIG. 1). In the magnetic proportional current sensor 2 using the magnetic sensor 1 having the bridge circuit, the measured current Io is measured by the potential difference output from the magnetic field detection bridge circuit according to the magnetic field to be measured.

A specific example of the magnetically balanced current sensor is a magnetically balanced current sensor 2A using the magnetic sensor 1A shown in FIGS. 3 and 4, and the magnetically balanced current sensor 2A is above FIG. 4 (Z1-Z2). (Direction Z1 side), the current line 40 through which the measured current Io flows is located so as to extend in the X1-X2 direction. The induced magnetic field of the measured current Io, which is the measured magnetic field, is applied to the magnetoresistive effect element 11 in the direction along the sensitivity axial direction P (Y1-Y2 direction). Since a part of the magnetic field to be measured passes through the magnetic shield 15 having a higher magnetic permeability, the strength of the magnetic field to be measured substantially applied to the magnetoresistive sensor 11 can be reduced. Therefore, the amount of current flowing through the magnetic equilibrium coil 16 can be reduced in order to generate an induced magnetic field that cancels the magnetic field due to the measured current Io substantially applied to the four magnetoresistive effect elements. Power saving of the current sensor is realized.

In a preferred example, the magnetic equilibrium current sensor 2A includes four magnetoresistive effect elements (magnetic resistance effect element 11 to 14), and is a measured magnetic field composed of an induced magnetic field from a measured current Io and a measured magnetic field thereof. A magnetic sensor 1A (see FIG. 3) having a magnetic field detection bridge circuit with two outputs that generate a potential difference depending on the induced magnetic field from the magnetic equilibrium coil 16 applied to cancel the measured magnetic field is used. In the magnetic balance type current sensor 2A having this bridge circuit, the measured current Io is measured based on the current flowing through the magnetic balance coil 16 when the potential difference output from the magnetic field detection bridge circuit becomes zero.

The embodiments described above are described for facilitating the understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention. For example, the magnetic attraction portion 15P does not have a shape that protrudes from the main body portion 150 at a right angle to the Z2 side in the Z1-Z2 direction, but a direction in which the tip portion 15PE (see FIG. 2) is separated from the plurality of magnetoresistive effect elements (X1-X2 direction). It may have a structure protruding in the Z1-Z2 direction Z2 side so as to be located on the X1 side or the X2 side of the above.

Hereinafter, the present invention will be described in more detail with reference to Examples and the like, but the scope of the present invention is not limited to these Examples and the like.

(Example 1)
A magnetic balance type magnetic sensor having a structure similar to the cross-sectional structure shown in FIG. 2 was manufactured. The magnetoresistive element was a GMR element having the following film configuration. The numbers in parentheses indicate the layer thickness (Å).
Underlayer: NiFeCr (42) / Fixed magnetic layer: Fe 60at _% Co _40at% (19) / Non-magnetic material layer: Ru (3.6) / Fixed magnetic layer: Co _90at% Fe _10at% (24) / Non-magnetic Material layer: Cu (20) / Free magnetic layer: [Co 90at _% Fe 10at _% (10) / Ni _82.5at% Fe _17.5at% (70)] / Anti-ferrometric layer: IrMn (80) / Protective layer : Ta (100)
The magnetic shield is provided with magnetic absorbing portions having a width of W100 μm at a position 150 μm away from the magnetoresistive effect element on both sides of the main body in the X1-X2 direction in a plan view (when viewed from the Z1-Z2 direction). The distance between the substrate and the main body was 9 μm, and the distance between the substrate and the end of the magnetic attraction portion was 6.5 μm.

(Comparative Example 1)
A magnetic sensor having the same structure as that of the first embodiment but having a shape in which the magnetic shield does not have a magnetic absorbing portion was manufactured.

(Measurement Example 1) Measurement of offset fluctuation amount For each of the magnetic sensor manufactured by the example and the magnetic sensor manufactured by the comparative example, the external magnetic field (strez magnetic field) applied in the direction orthogonal to the sensitivity axis is ± XmT (X is 5 to 30, 5 to 20 every 1 mT, 20 to 30 every 5 mT), while changing the external magnetic field so that the absolute values of the positive and negative external magnetization applied alternately gradually increase, the magnetic sensor The amount of offset fluctuation of the output of was measured.
The measurement results for the magnetic sensors (3 each) of the examples and the comparative examples are shown in FIGS. 6 and 7.

As shown in FIG. 6, in the magnetic sensor according to the embodiment, the external magnetic field was offset at ± 16 mT. On the other hand, as shown in FIG. 7, in the magnetic sensor according to the comparative example, the external magnetic field was offset at ± 13 mT. That is, by providing the magnetically absorbing portion on the magnetic shield, the resistance to an external magnetic field in the direction orthogonal to the sensitivity axis is improved by 3 mT. This is because the magnetic shield is provided with a magnetic absorption part, which improves the function of attenuating the external magnetic field in the direction orthogonal to the sensitivity axis, and reduces the external magnetic field reaching the free magnetic layer of the magnetoresistive sensor. As a result, it is presumed that the external magnetic field in which the magnetization direction of the free magnetic layer is reversed has increased.

The magnetic sensor provided with the magnetoresistive effect element according to the embodiment of the present invention is suitably used as a component of a current sensor of infrastructure equipment such as a columnar transformer and a component of a current sensor of an electric vehicle, a hybrid car, or the like. sell.

1,1A: Magnetic sensor 2: Magnetic proportional current sensor (current sensor)
2A: Magnetically balanced current sensor (current sensor)
5, 6, 7, 8: Wiring 5a: Input terminal 6a: Ground terminal 7a: First midpoint potential measurement terminal 8a: Second midpoint potential measurement terminal 11, 12, 13, 14: Magnetic resistance effect Element 15: Magnetic shield 15E: End 15P: Magnetic absorption part 15PE: Tip part 150: Main body part 16: Magnetic equilibrium coil 20: Step 29: Substrate 30: GMR element 31: Fixed magnetic layer 32: Non-magnetic layer 33: Free Magnetic layer 34: Anti-ferrometric layer 40: Current line IM: Insulation layer Io: Measured current M: External magnetic field P: Sensitivity axis direction PL: Oxidation protection layer D1: Magnetic shield and substrate directly above the four magnetic resistance effect elements Distance D2: Distance between the magnetic shield outside the four magnetic resistance effect elements and the substrate L11, L13: Distance between the magnetic attraction part and the magnetic resistance effect element W: Width of the magnetic absorption part

Claims (7)

A plurality of magnetoresistive elements provided on the substrate and having a sensitivity axis in the first direction, an insulating layer provided on the magnetoresistive element, and applied to the magnetoresistive element provided on the insulating layer. A magnetic sensor equipped with a magnetic shield that attenuates the strength of the magnetic field under test.
The magnetic shield has a main body portion and a magnetic absorption portion projecting toward the magnetoresistive effect element.
The main body has a shape having a length in a second direction orthogonal to the first direction in a plan view, and overlaps with all of the plurality of magnetoresistive elements.
The magnetic attraction portions are not provided at both ends in the first direction, but are provided at both ends in the second direction, and the tip portions thereof are a plurality of the magnetoresistive elements in a plan view. It is located away from the
The distance D1 between the main body directly above the magnetoresistive sensor and the substrate and the distance D2 between the magnetic attraction portion outside the magnetoresistive element and the substrate satisfy D1> D2.
A magnetic sensor featuring. The magnetic sensor according to claim 1, wherein the plurality of magnetoresistive sensor elements are provided at equal distances from each pair of ends of the magnetic shield located in the first direction in a plan view. The magnetic sensor according to claim 1 or 2, wherein each of the plurality of magnetoresistive elements is a GMR element having a meander shape. The magnetic sensor according to claim 3, wherein a bias magnetic field is applied to the free magnetic layer of the GMR element. The magnetic sensor according to any one of claims 1 to 4, further comprising a magnetic equilibrium coil and measuring the strength of the measured magnetic field based on a current flowing through the magnetic equilibrium coil. The magnetic sensor according to claim 5, wherein the magnetic balancing coil is a spiral coil and is located between the magnetoresistive sensor and the magnetic shield. The magnetic sensor according to any one of claims 1 to 6, wherein the magnetic sensor uses an induced magnetic field of a measured current as the measured magnetic field.

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