JP5540326B2 - Current sensor - Google Patents

Description

  The present invention relates to a current sensor that measures the magnitude of a current, for example, a current sensor that includes a magnetoresistive element (TMR element, GMR element).

  2. Description of the Related Art Conventionally, in a field such as a motor driving technique in an electric vehicle or a hybrid car, a current sensor capable of measuring a motor driving current in a non-contact manner is required. As such a current sensor, a sensor having a magnetoresistive effect element that outputs an output signal by an induced magnetic field from a current to be measured has been proposed (see, for example, Patent Document 1).

  The current sensor described in Patent Literature 1 includes a Wheatstone bridge circuit including four magnetoresistive elements. In this Wheatstone bridge circuit, the current to be measured is measured by the output signals from two pairs of magnetoresistive elements configured to obtain output signals having opposite phases.

JP 2005-529338 A

  By the way, in the current sensor described in Patent Document 1, since the Wheatstone bridge circuit is used for measuring the current to be measured, it is necessary to obtain output signals having different signal strengths from the two pairs of magnetoresistive elements. For this reason, in the current sensor described in Patent Document 1, the magnetization directions of the ferromagnetic pinned layers of the two pairs of magnetoresistive elements are fixed in different directions with respect to the direction in which the induced magnetic field is applied from the current to be measured. The current to be measured can be measured by setting the output signals output from the two pairs of magnetoresistive elements to opposite phases.

  However, in the current sensor described in Patent Document 1, since the magnetization directions of the ferromagnetic pinned layers of the two pairs of magnetoresistive elements are different from each other, the influence of disturbance noise components in which disturbance noise acts on the two pairs of magnetoresistive elements. However, there is a problem that the measurement accuracy decreases. In addition, since the exchange coupling magnetic field between the ferromagnetic pinned layer and the antiferromagnetic layer is used to fix the magnetization direction of the ferromagnetic pinned layer of the magnetoresistive effect element, the operable temperature is limited and the manufacturing is performed. In the process, since a high-temperature annealing process in a magnetic field is required, there is a problem that the manufacturing cost increases.

  The present invention has been made in view of such a point, and an object thereof is to provide a current sensor that is excellent in operational stability at high temperatures and has high measurement accuracy.

  The current sensor of the present invention outputs an output signal by a conductor extending in one direction and an induced magnetic field from a current to be measured that is arranged in parallel along the extending direction of the conductor and flows through the conductor. At least two pairs of magnetoresistive elements, wherein the magnetoresistive element includes a ferromagnetic pinned layer whose magnetization direction is fixed, a nonmagnetic intermediate layer, and a free magnetic layer whose magnetization direction varies with respect to an external magnetic field And the ferromagnetic pinned layer is a self-pinning type in which the first ferromagnetic film and the second ferromagnetic film are antiferromagnetically coupled via an antiparallel coupling film. The at least two pairs of magnetoresistive elements are a pair of magnetoresistive elements disposed along the first section of the conductor and the other disposed along the second section of the conductor. A pair of magnetoresistive effect elements, and the pair of magnetoresistive effects The child and the other pair of the magnetoresistive element, the inductive magnetic field is applied to each other with different intensity, or wherein the induction magnetic field is arranged to be applied from different directions.

  According to this configuration, the output signals output from the pair of magnetoresistive effect elements by the induced magnetic field from the current to be measured and the output signals output from the other pair of magnetoresistive effect elements have different signal intensities. Therefore, by obtaining the differential output between the output signals of a pair of magnetoresistive elements and the output signals of the other pair of magnetoresistive elements, the disturbance noise component of the output signals can be reduced, and the current with high measurement accuracy. A sensor can be realized. In addition, since the current to be measured flows through a conductor extending in one direction, the current sensor can be miniaturized and the interference of the induced magnetic field from the current to be measured can be reduced, so that the measurement accuracy of the current sensor is improved. Further improvement. Furthermore, since the resistance of the conductor when the current to be measured flows can be reduced, the measurement range of the current sensor can be expanded. In addition, since the self-pinned magnetoresistive element is used, the magnetization direction of the pinned magnetic layer can be fixed without using an antiferromagnetic layer, so that a current sensor having excellent operational stability at high temperatures can be realized.

  The current sensor of the present invention includes a first half-bridge circuit including the pair of magnetoresistive elements and a second half-bridge circuit including the other pair of magnetoresistive elements. The magnetization direction of the ferromagnetic pinned layer in each magnetoresistive effect element of the half-bridge circuit is the same as the magnetization direction of the ferromagnetic pinned layer in each magnetoresistive effect element of the second half-bridge circuit. It is preferable. With this configuration, the disturbance noise component in the output signal output from the first half-bridge circuit is equal to the disturbance noise component in the output signal output from the second half-bridge circuit. For this reason, by obtaining the differential outputs of the two pairs of magnetoresistive elements, disturbance noise components can be canceled out, and the measurement accuracy can be further improved.

  In the current sensor of the present invention, the magnetization directions of the ferromagnetic pinned layers of the pair of magnetoresistive effect elements are antiparallel to each other, and the magnetization directions of the ferromagnetic pinned layers of the other pair of magnetoresistive effect elements are It is preferable that they are antiparallel to each other. With this configuration, the output signals output from the pair of magnetoresistive effect elements and the output signals output from the other pair of magnetoresistive effect elements are in opposite phases. For this reason, by obtaining the differential outputs of the two pairs of magnetoresistive elements, the output signals output by the induced magnetic field are added, so that the detection sensitivity of the current sensor can be improved. Note that antiparallel means directions that are 180 ° different from each other and are opposite to each other.

  In the current sensor according to the aspect of the invention, the conductor has a cross-sectional area in a vertical section with respect to the extending direction of the first section and a cross-sectional area in a vertical section with respect to the extending direction of the second section are different. Is preferred. With this configuration, the induced magnetic field applied to the pair of magnetoresistive effect elements and the induced magnetic field applied to the other pair of magnetoresistive effect elements have different magnetic field strengths. The output signal output and the output signal output from the other pair of magnetoresistive elements have different signal strengths. For this reason, the measured current can be measured by using the output signals from the pair of magnetoresistive elements and the output signals of the other pair of magnetoresistive elements.

  In the current sensor of the present invention, the distance between the pair of magnetoresistance effect elements and the first section of the conductor, the other pair of magnetoresistance effect elements and the second section of the conductor, It is preferable that the distance between is different. With this configuration, the induced magnetic field applied to the pair of magnetoresistive effect elements and the induced magnetic field applied to the other pair of magnetoresistive effect elements have different magnetic field strengths. The output signal output and the output signal output from the other pair of magnetoresistive elements have different signal strengths. For this reason, the measured current can be measured by using the output signals from the pair of magnetoresistive elements and the output signals of the other pair of magnetoresistive elements.

  In the current sensor according to the aspect of the invention, it is preferable that the pair of magnetoresistive elements and the other pair of magnetoresistive elements are arranged so that the induction magnetic fields are applied in opposite directions. . With this configuration, the direction in which the induced magnetic field is applied to the pair of magnetoresistive elements disposed on one surface side of the conductor and the other pair of magnetoresistive elements disposed on the other surface side of the conductor The directions in which the induction magnetic field is applied to are opposite to each other. For this reason, since the output signals output from the pair of magnetoresistive elements and the output signals output from the other pair of magnetoresistive elements have different signal strengths and opposite phases, two pairs of magnetoresistive elements Since the disturbance noise component is removed and the output signal from the induced magnetic field is added, a current sensor with high measurement accuracy can be realized.

  According to the present invention, it is possible to provide a current sensor that has excellent operational stability at high temperatures and high measurement accuracy.

It is a schematic plan view showing an example of a current drawing type current sensor. It is a plane schematic diagram of the current sensor according to the first embodiment. It is a schematic diagram which shows the magnetic detection bridge circuit of the current sensor which concerns on the said embodiment. It is a figure which shows the relationship between the to-be-measured current and output signal in the current sensor which concerns on the said embodiment. It is a cross-sectional schematic diagram of the current sensor according to the embodiment. It is a schematic diagram which shows the laminated structure of the magnetoresistive effect element of the current sensor which concerns on the said embodiment. It is explanatory drawing of the manufacturing process of the current sensor which concerns on the said embodiment. It is explanatory drawing of the manufacturing process of the current sensor which concerns on the said embodiment. It is a plane schematic diagram of the current sensor which concerns on 2nd Embodiment. It is a cross-sectional schematic diagram of the current sensor according to the embodiment. It is a cross-sectional schematic diagram of the current sensor which concerns on 3rd Embodiment. It is a cross-sectional schematic diagram of the current sensor which concerns on 4th Embodiment.

  In recent years, further miniaturization of current sensors and improvement of measurement accuracy have been demanded. In order to reduce the size of the current sensor, a current drawing type current sensor that draws a current to be measured into a conductor pattern provided on a substrate and measures the current to be measured has been studied.

  FIG. 1 shows an example of a current draw type current sensor. The current sensor 100 includes a U-shaped conductor 102 in plan view provided on a substrate 101, GMR elements 103a and 103b provided at one end of the conductor 102, and a GMR provided at the other end. Elements 103c and 103d are provided. In the four GMR elements 103a to 103d, the magnetization directions of the ferromagnetic fixed layers are aligned in the same direction (see the arrow in FIG. 1), and form a magnetic field detection bridge circuit. In the current pull-in type current sensor 100, induced magnetic fields applied from opposite directions to each other at one end and the other end of the U-shaped conductor 102 are detected via the four GMR elements 103 a to 103 d.

  In the current pull-in type current sensor 100, in order to measure the current to be measured via the magnetic field detection bridge circuit, the output signals output from the pair of GMR elements 103 a and 103 b at one end of the conductor 102, The output signals output from the other pair of GMR elements 103c and 103d at the other end need to have different signal strengths. For this reason, in the current pull-in type current sensor 100, the conductor 102 is U-shaped, and a current to be measured is passed from one end of the conductor 102 to the other end. The direction in which the current to be measured flows is opposite to the direction in which the current to be measured flows at the other end. As a result, the direction in which the induced magnetic field is applied to the pair of GMR elements 103a and 103b and the direction in which the induced magnetic field is applied to the other pair of GMR elements 103c and 103d are opposite to each other, and thus the pair of GMR elements 103a and 103b. The output signals output from the first and second output signals from the other pair of GMR elements 103c and 103d have different signal intensities, and the current to be measured can be measured by the magnetic field detection bridge circuit.

  In the current pull-in type current sensor 100, since the magnetization directions of the ferromagnetic fixed layers of the four GMR elements 103a to 103d are aligned in the same direction, the same direction with respect to the sensitivity axes of the GMR elements 103a to 103d. Disturbance noise acts from. Therefore, the influence of disturbance noise is canceled by taking the difference value between the output signals output from the pair of GMR elements 103a and 103b and the output signals output from the other pair of GMR elements 103c and 103d. Is possible.

  On the other hand, in the current draw type current sensor 100, the output signals output from the pair of GMR elements 103a and 103b and the output signals output from the other pair of GMR elements 103c and 103d are different from each other. In order to obtain signal strength, it is necessary to form the conductor 102 in a U shape, and there is a problem in that downsizing of the current sensor 100 is limited. In addition, since the current to be measured flows through the conductor 102 curved in a U-shape, interference is generated in the induced magnetic field, the measurement accuracy is lowered, and the resistance of the conductor 102 is increased, resulting in a loss of the current to be measured. Since heat generation occurs, there is a problem that the measurement range of the current to be measured is limited.

  The present inventors paid attention to the magnetic field strength of the induced magnetic field from the current to be measured applied to the magnetoresistive effect element and the application direction of the induced magnetic field. In a current pull-in type current sensor, a conductor extending in one direction is used if an output signal with different signal strength can be obtained from a pair of magnetoresistive elements and another pair of magnetoresistive elements. Even in such a case, the current to be measured can be measured by the magnetic field detection bridge circuit.

  In addition, the present inventors have paid attention to a self-pinned magnetoresistive element that can fix the magnetization direction of the ferromagnetic fixed layer without using an antiferromagnetic layer. Here, the self-pinned structure has a laminated structure including a ferromagnetic pinned layer 32, a nonmagnetic intermediate layer 36, and a free magnetic layer 37 as shown in FIG. A structure having no antiferromagnetic layer under the layer 32 is referred to. The ferromagnetic pinned layer 32 includes a first ferromagnetic film 33, an antiparallel coupling film 34, and a second ferromagnetic film 35, and the second ferromagnetic film 35 faces the nonmagnetic intermediate layer 36. doing. By using the self-pinning type magnetoresistive element as a current pulling type current sensor, the magnetization direction X of the ferromagnetic pinned layer 32 of the plurality of magnetoresistive effect elements provided on the substrate can be fixed in an arbitrary direction. It becomes.

  In the case where at least two pairs of magnetoresistive effect elements are juxtaposed along the extending direction of the conductor extending in one direction, the present inventors also have a pair of magnetoresistive effect elements and another pair of magnetoresistive elements. By disposing the effect elements so that the induction magnetic fields are applied with different intensities, or the induction magnetic fields are applied from different directions, the pair of magnetoresistance effect elements and the other pair of magnetoresistance effect elements are different from each other. It has been found that an output signal of signal strength can be obtained. This makes it possible to measure the current to be measured by the magnetic field detection bridge circuit using the output signals from the pair of magnetoresistive elements and the output signals from the other pair of magnetoresistive elements. Such a configuration can be realized by using at least two pairs of self-pinning type magnetoresistive effect elements in a current drawing type current sensor that draws a current to be measured into a conductor on a substrate.

  Furthermore, the present inventors can reduce the size of the substrate and reduce the size of the current sensor by using a conductor extending in one direction in the current-drawing type current sensor. The inventors have found that interference can be reduced and measurement accuracy can be improved, and that induced electromotive force against an external magnetic field can be suppressed, and the present invention has been completed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
(First embodiment)
FIG. 2 is a schematic plan view of the current sensor 1 according to the first embodiment of the present invention. As shown in FIG. 2, the current sensor 1 according to the present embodiment includes a substrate 11 and four magnetoresistive elements 12 a that are arranged on the substrate 11 and output an output signal by an induced magnetic field from a current to be measured. To 12d and the conductor 13 laminated on the magnetoresistive effect elements 12a to 12d with an insulating layer interposed therebetween. The conductor 13 is provided so as to extend in one direction along the magnetoresistive elements 12a to 12d arranged in parallel on the substrate 11, and electrode pads 13a for drawing a current to be measured from the outside to both ends. 13b is provided. In the current sensor 1 according to the present embodiment, the current to be measured that is drawn from the outside via the electrode pads 13a and 13b and flows through the conductor 13 in one direction includes four magnetoresistive elements 12a to 12d. It measures with the magnetic field detection bridge circuit which becomes.

  In the extending direction D1, the conductor 13 has a first section S1 and a second section S2 having different vertical cross-sectional areas along the height direction D3 orthogonal to the extending direction D1. In the present embodiment, by providing the conductor 13 so that the width dimension L1 on the electrode pad 13a side in the extending direction D1 is relatively larger than the width dimension L2 on the electrode pad 13b side, the conductor 13 electrode pad 13a side is defined as a first section S1 having a relatively large cross-sectional area, and electrode pad 13b side is defined as a second section S2 having a relatively small cross-sectional area.

  The magnetoresistive elements 12 a to 12 d are arranged so as to overlap the conductor 13 along the extending direction D <b> 1 of the conductor 13. In the present embodiment, the magnetoresistive effect elements 12 a to 12 d are arranged in the same plane (see FIG. 5), and the pair of magnetoresistive effect elements 12 a and 12 b extend along the first section S <b> 1 of the conductor 13. The other pair of magnetoresistive elements 12c and 12d are disposed along the second section S2 of the conductor 13. The magnetoresistive effect elements 12a to 12d are output from the pair of magnetoresistive effect elements 12a and 12b and the other pair of magnetoresistive effect elements 12c and 12d by the induced magnetic field from the current to be measured. If the output signals are different in signal strength from each other, it is not always necessary to arrange them in the same plane.

  In the magnetoresistance effect elements 12a to 12d, the sensitivity axes (Pin direction) of the pair of magnetoresistance effects 12a and 12b and the sensitivity axes (Pin direction) of the other pair of magnetoresistance effect elements 12c and 12d are antiparallel to each other ( 180 ° different directions). The pair of magnetoresistive elements 12a and 12b are arranged so that the sensitivity axes (Pin directions) of the magnetoresistive elements 12a and 12b are antiparallel to each other (direction different by 180 °). The magnetoresistive effect elements 12c and 12d are arranged so that the sensitivity axes (Pin directions) of the magnetoresistive effect elements 12c and 12d are antiparallel to each other (a direction different by 180 °). In FIG. 2, arrows attached to the magnetoresistive effect elements 12a to 12d indicate the magnetization directions of the second ferromagnetic films 35 (not shown in FIG. 1, refer to FIG. 6) of the magnetoresistive effect elements 12a to 12d. Represents. At both ends of each of the magnetoresistive effect elements 12a to 12d, a hard bias layer 14 (FIG. 1) that applies a bias magnetic field to the free magnetic layer 37 (not shown in FIG. 1, see FIG. 6) of the magnetoresistive effect elements 12a to 12d. (Not shown, see FIG. 5). Note that the hard bias layer 14 is not necessarily provided.

  The magnetoresistive elements 12a to 12d are GMR elements having a shape (a meander shape) formed by folding a plurality of strip-like long patterns (stripes) arranged so that their longitudinal directions are parallel to each other. preferable.

  Next, connection of the magnetic field detection bridge circuit of the current sensor 1 shown in FIG. 2 will be described. A power supply potential (Vdd) is applied to one terminal of the magnetoresistive effect element 12b and one terminal of the magnetoresistive effect element 12c, respectively, and one terminal of the magnetoresistive effect element 12a and the magnetoresistive effect element 12d. One terminal is supplied with a ground potential (GND1, GND2). In addition, the other terminal of the magnetoresistive effect element 12a and the other terminal of the magnetoresistive effect element 12b are connected to form a first output (Out1), and the other terminal of the magnetoresistive effect element 12c, and The other terminals of the magnetoresistive effect element 12c are connected to form a second output (Out2).

  Since the magnetoresistive effect elements 12a to 12d have a characteristic that the resistance value is changed by applying an induced magnetic field from the current to be measured, the first output (in accordance with the induced magnetic field from the current to be measured ( Out1) and the second output (Out2) change. The potential difference between the first output (Out1) and the second output (Out2) is proportional to the induced magnetic field, and the potential difference (voltage) becomes the output of the current sensor 1.

  FIG. 3 is a schematic diagram showing a magnetic detection bridge circuit in the current sensor according to the present embodiment. In the current sensor 1 according to the present embodiment, as shown in FIG. 3, the magnetization directions (second second) of the ferromagnetic pinned layers 32 of the two magnetoresistive elements 12a and 12b that output the midpoint potential (Out1) are output. The magnetization direction (Pin2) of the ferromagnetic film is 180 ° different from each other (anti-parallel), and the magnetization direction (the first direction) of the ferromagnetic pinned layer 32 of the two magnetoresistive effect elements 12c and 12d that output the midpoint potential (Out2). The magnetization directions of the two ferromagnetic films (Pin2) are 180 ° different from each other (antiparallel). Further, the resistance change rates of the four magnetoresistive elements 12a to 12d are the same. The magnetoresistive elements 12a to 12d preferably exhibit the same rate of change in resistance at the same magnetic field strength when the angle of the applied magnetic field to the ferromagnetic pinned layer 32 is the same.

  In the current sensor 1 according to the present embodiment, the pair of magnetoresistive elements 12a and 12b and the other pair of magnetoresistive elements 12c, 12d, a pair of magnetoresistive elements 12a and 12b constitutes a first half bridge circuit, and another pair of magnetoresistive elements 12c and 12d constitutes a second half bridge circuit.

  As shown in FIG. 3, when a current to be measured is passed through the conductor 13, an induced magnetic field A is applied to each of the four magnetoresistive elements 12a to 12d. Here, in the current sensor 1 according to the present embodiment, the conductor 13 has a cross-sectional area in the first section S1 in the vicinity of the magnetoresistive effect elements 12a and 12b in the second section in the vicinity of the magnetoresistive effect elements 12c and 12d. Since it is larger than the cross-sectional area of the conductor 13 in S2, an induced magnetic field A having a relatively small magnetic field strength is applied to the magnetoresistive elements 12a and 12b. Therefore, from the output signals output from the pair of magnetoresistive elements 12a and 12b constituting the first half bridge circuit and the other pair of magnetoresistive elements 12c and 12d constituting the second half bridge circuit. Since the output signal is different in signal strength, the current to be measured can be measured by the magnetic field detection bridge circuit.

  Here, with reference to FIG. 4, an output signal when an induction magnetic field is applied to the magnetoresistive effect elements 12a to 12d will be described. FIG. 4 is a conceptual diagram showing the correlation between the magnitude of the current to be measured and the output signals from the magnetoresistive elements 12a to 12d. In the figure, the horizontal axis represents the magnitude of the induced magnetic field, and the vertical axis represents the magnitude of the output signal.

  As shown in FIG. 4A, the output signals output from the pair of magnetoresistive effect elements 12a and 12b arranged along the first section S1 of the conductor 13 are in opposite phases and have the same strength (see FIG. 4A). (See dashed line 4A). On the other hand, the output signals output from the other pair of magnetoresistive elements 12c and 12d disposed along the second section S2 of the conductor 13 are in reverse phase with each other, have the same strength, and have a pair of magnetic fields. It becomes relatively large with respect to the output signals output from the resistance effect elements 12a and 12b (see the solid line in FIG. 4A). For this reason, as shown in FIG. 4B, when the current I to be measured having the same magnitude flows, the output signal from the first half bridge circuit including the pair of magnetoresistive elements 12a and 12b and the other There is a difference in signal strength between the output signal from the second half-bridge circuit including the pair of magnetoresistive elements 12c and 12d (see S3). As a result, the current to be measured can be measured by the magnetic field detection bridge circuit.

  As described above, in the current sensor 1 according to the present embodiment, the magnetization directions of the ferromagnetic pinned layers 32 of the magnetoresistive effect elements 12a and 12d are made the same, and the ferromagnetic pinned layers of the magnetoresistive effect elements 12a and 12d are aligned. With respect to the magnetization direction of 32, the magnetization direction of the ferromagnetic fixed layer 32 of the magnetoresistive effect elements 12b and 12c is aligned in an antiparallel direction (a direction different by 180 °). With this configuration, the output signals output from the pair of magnetoresistive elements 12a and 12b by the induced magnetic field A and the output signals output from the other pair of magnetoresistive elements 12c and 12d are reversed in phase, The output signals output from the pair of magnetoresistive elements 12a and 12b due to the disturbance noise B are equal to the output signals output from the other pair of magnetoresistive elements 12c and 12d. Therefore, by obtaining a differential output between the output signals from the pair of magnetoresistive elements 12a and 12b and the output signals from the other pair of magnetoresistive elements 12c and 12d, Since addition and disturbance noise can be canceled, measurement accuracy and detection sensitivity can be improved. Therefore, a current sensor with high detection sensitivity and measurement accuracy can be realized.

  Next, the laminated structure of the current sensor 1 will be described in detail. 5 is a cross-sectional view taken along line VV of the current sensor 1 shown in FIG. As shown in the figure, in the current sensor 1 according to the present embodiment, a magnetic field detection bridge circuit (magnetoresistance effect elements 12 a to 12 d) and a conductor 13 are stacked on the same substrate 11.

  In the current sensor 1 shown in FIG. 5, a silicon oxide film 21 that is an insulating layer is formed on a substrate 11. An aluminum oxide film 22 is formed on the silicon oxide film 21. The aluminum oxide film 22 can be formed by a method such as sputtering. Further, a silicon substrate or the like is used as the substrate 11.

  On the aluminum oxide film 22, the magnetoresistive effect elements 12a to 12d are disposed, and a magnetic field detection bridge circuit is formed. As the magnetoresistive elements 12a to 12d, TMR elements (tunnel type magnetoresistive elements), GMR elements (giant magnetoresistive elements), and the like can be used. Hard bias layers 14 for applying a bias magnetic field to the free magnetic layers 37 of the magnetoresistive effect elements 12a to 12d are provided at both ends of the magnetoresistive effect elements 12a to 12d.

  On the magnetoresistive effect elements 12 a to 12 d and the hard bias layer 14, a conductor 13 (current to be measured) is laminated via an insulating layer 23. The conductor 13 can be formed by photolithography and plating after forming a base material by sputtering or the like.

  On the conductor 13, a magnetic shield 25 that absorbs disturbance noise to the magnetoresistive effect elements 12 a to 12 d through the insulating layer 24 is provided. In addition, electrode pads 13 a and 13 b are formed at both ends of the conductor 13. The electrode pads 13a and 13b can be formed by photolithography and plating after forming an electrode material.

  As the insulating layers 23 and 24, for example, a polyimide layer formed by applying and curing a polyimide material can be used. As a material constituting the magnetic shield 25, a high magnetic permeability material such as an amorphous magnetic material, a permalloy magnetic material, or an iron microcrystalline material can be used.

  A silicon oxide film 26 is laminated on the magnetic shield 25. The silicon oxide film 26 can be formed by a method such as sputtering.

  A contact hole 27 is formed in a predetermined region of the insulating layer 24 and the silicon oxide film 26 (region where the electrode pads 13a and 13b are formed), and the electrode pads 13a and 13b are formed in the contact hole 27. For forming the contact hole 27, photolithography, etching, or the like is used.

In the current sensor 1 having the above configuration, since the magnetic detection bridge circuit is configured by the four magnetoresistive effect elements 12a to 12d having the same film configuration, the zero magnetic field resistance value (R ₀ ) between the elements and the resistance temperature coefficient ( TCR ₀ ) can be eliminated. For this reason, variation in the midpoint potential can be reduced regardless of the environmental temperature, and current measurement can be performed with high accuracy. In addition, the current sensor 1 having the above configuration can be downsized because the conductor 13, the magnetic shield 25, and the magnetic field detection bridge circuit (the magnetoresistive effect elements 12a to 12d) are stacked on the same substrate. . Furthermore, since the current sensor 1 has a configuration without a magnetic core, it can be reduced in size and cost.

  Next, a laminated structure of the current sensor 1 according to the present embodiment will be described with reference to FIG. FIG. 6 is a schematic cross-sectional view showing the laminated structure of the magnetoresistive effect elements 12a to 12d of the current sensor 1 according to the present embodiment.

  As shown in FIG. 6, the magnetoresistive effect elements 12 a to 12 d are stacked on the aluminum oxide film 22. The magnetoresistive effect elements 12a to 12d include a seed layer 31, a ferromagnetic pinned layer 32 (a first ferromagnetic film 33, an antiparallel coupling film 34, and a second ferromagnetic film 35), a nonmagnetic intermediate layer 36, a free layer The magnetic layer 37 and the protective layer 38 are laminated in this order.

  In the magnetoresistive effect elements 12a to 12d, the first ferromagnetic film 33 and the second ferromagnetic film 35 are antiferromagnetically coupled via the antiparallel coupling film 34, so-called self-pinning type. A ferromagnetic pinned layer 32 (SFP: Synthetic Ferri Pinned layer) is formed. In this way, by forming the self-pinned (Bottom-Spin-Value) magnetoresistive effect elements 12a to 12d, in the manufacturing process of the magnetoresistive effect elements 12a to 12d, it is essential in the conventional magnetoresistive effect element. Annealing in a magnetic field for fixing the magnetization direction of a certain ferromagnetic pinned layer 32 becomes unnecessary, and the induced magnetic anisotropy in the stripe longitudinal direction D1 imparted during the formation of the free magnetic layer 37 can be maintained. Thereby, it becomes possible to reduce hysteresis with respect to the detection target direction.

  In the ferromagnetic pinned layer 32, the thickness of the antiparallel coupling film 34 is set to 0.3 nm to 0.45 nm, or 0.75 nm to 0.95 nm, so that the first ferromagnetic film 33 and the second ferromagnetic film 33 Strong antiferromagnetic coupling with the ferromagnetic film 35 can be brought about.

The magnetization amount (Ms · t) of the first ferromagnetic film 33 and the magnetization amount (Ms · t) of the second ferromagnetic film 35 are substantially the same. That is, the difference in magnetization between the first ferromagnetic film 33 and the second ferromagnetic film 35 is substantially zero. For this reason, the effective anisotropic magnetic field of the ferromagnetic fixed layer 32 is large. Therefore, sufficient magnetization stability of the ferromagnetic pinned layer 32 can be ensured without using an antiferromagnetic material. This is because the film thickness of the first ferromagnetic film 33 is t ₁ , the film thickness of the second ferromagnetic film 35 is t _2, and the magnetization per unit volume of both layers and the induced magnetic anisotropy constant are respectively This is because when Ms, K, the effective anisotropic magnetic field of the SFP layer is represented by the following relational expression (1). Therefore, the magnetoresistive effect elements 12a to 12d used in the current sensor 1 according to the present embodiment have a film configuration that does not have an antiferromagnetic layer.
Formula (1)
eff Hk = 2 (K · t ₁ + K · t ₂ ) / (Ms · t ₁ −Ms · t ₂ )

  The Curie temperature (Tc) of the first ferromagnetic film 33 and the Curie temperature (Tc) of the second ferromagnetic film 35 are the same. Thereby, even in a high temperature environment, the difference in magnetization (Ms · t) between the first ferromagnetic film 33 and the second ferromagnetic film 35 becomes zero, and high magnetization stability can be maintained.

  The first ferromagnetic film 33 is preferably made of a CoFe alloy containing 40 atomic% to 80 atomic% of Fe. This is because a CoFe alloy having this composition range has a large coercive force and can stably maintain magnetization with respect to an external magnetic field. The second ferromagnetic film 35 is preferably made of a CoFe alloy containing 0 atomic% to 40 atomic% of Fe. This is because the CoFe alloy having this composition range has a small coercive force and is easily magnetized in an antiparallel direction (a direction different by 180 °) with respect to the direction in which the first ferromagnetic film 33 is preferentially magnetized. is there. As a result, it is possible to further increase Hk represented by the relational expression (1). Further, by limiting the second ferromagnetic film 35 to this composition range, it is possible to increase the resistance change rate of the magnetoresistive effect elements 12a to 12d.

  A magnetic field is applied to the first ferromagnetic film 33 and the second ferromagnetic film 35 in the stripe width direction of the meander shape during the film formation, and the first ferromagnetic film 33 and the second strong film after the film formation are applied. It is preferable that induced magnetic anisotropy is imparted to the magnetic film 35. As a result, the first ferromagnetic film 33 and the second ferromagnetic film 35 are magnetized antiparallel to the stripe width direction. In addition, the magnetization directions (directions in which the magnetization is fixed) of the first ferromagnetic film 33 and the second ferromagnetic film 35 are determined by the magnetic field application direction when the first ferromagnetic film 33 is formed. It is possible to form a plurality of magnetoresistive elements having ferromagnetic pinned layers having different magnetization directions on the same substrate by changing the direction of magnetic field application during the formation of the ferromagnetic film 33.

  The seed layer 31 is made of NiFeCr or Cr. The protective layer 38 is made of T or the like. In the laminated structure, the aluminum oxide film 22 and the seed layer 31 are made of a nonmagnetic material such as at least one element of Ta, Hf, Nb, Zr, Ti, Mo, and W, for example. An underlayer may be provided.

  The antiparallel coupling film 34 of the ferromagnetic pinned layer 32 is made of Ru or the like. The free magnetic layer (free layer) 37 is made of a magnetic material such as a CoFe alloy, a NiFe alloy, or a CoFeNi alloy. The nonmagnetic intermediate layer 36 is made of Cu or the like. Further, it is preferable that a magnetic field is applied to the free magnetic layer 37 in the stripe longitudinal direction D1 during film formation, and induced magnetic anisotropy is imparted to the free magnetic layer 37 after film formation. Thereby, in the magnetoresistive effect elements 12a to 12d, the resistance is linearly changed with respect to the external magnetic field (magnetic field from the current to be measured) in the stripe width direction orthogonal to the stripe longitudinal direction D1, and the hysteresis can be reduced. it can. In such a magnetoresistive effect element, a spin valve configuration is adopted by the ferromagnetic pinned layer 30, the nonmagnetic intermediate layer 36 and the free magnetic layer 37.

As an example of the film configuration of the magnetoresistive effect elements 12a to 12d used in the current sensor 1 according to the present embodiment, for example, NiFeCr (seed layer 31: 5 nm) / Fe ₇₀ Co ₃₀ (first ferromagnetic film 33: 1.65 nm) / Ru (anti-parallel coupling film 34: 0.4 nm) / Co ₉₀ Fe ₁₀ (second ferromagnetic film 35: 2 nm) / Cu (nonmagnetic intermediate layer 36: 2.2 nm) / Co ₉₀ Fe ₁₀ (free magnetic layer 37: 1 nm) / Ni ₈₁ Fe ₁₉ (free magnetic layer 37: 7 nm) / Ta (protective layer 38: 5 nm).

  Next, a method for manufacturing the current sensor 1 according to the embodiment of the present invention will be described. In the method of manufacturing the current sensor 1 according to the present embodiment, first, the first ferromagnetic film 33 and the second ferromagnetic film 35 are anti-bonded on the aluminum oxide film 22 via the anti-parallel coupling film 34. A magnetoresistive effect element 12a to 12 having a self-pinned ferromagnetic fixed layer 32, a nonmagnetic intermediate layer 36, and a free magnetic layer 37 that are ferromagnetically coupled and whose magnetization direction is fixed in a specific direction. 12d of the first laminated film is formed (first forming step), the first laminated film in a region other than the region where the first laminated film is left is removed from the aluminum oxide film 22 (removing step), and the first laminated film is removed. Self-pinning type ferromagnetic pinning in which the first ferromagnetic film 33 and the second ferromagnetic film 35 are antiferromagnetically coupled to the removed aluminum oxide film 22 via the antiparallel coupling film 34. Layer 32, nonmagnetic intermediate layer 36, and free magnetic layer And a 7 to form a second laminated film of the magnetoresistive element 12b to the magnetization direction of the specific direction and the ferromagnetic pinned layer 32 in the antiparallel direction is fixed (second forming step). Thereby, the magnetoresistive effect elements 12 a and 12 b having different magnetization directions of the ferromagnetic pinned layer 32 can be provided close to each other on the same substrate 11. Further, by repeatedly performing the removing step and the second forming step, a plurality of magnetoresistive elements 12a to 12d having different magnetization directions of the ferromagnetic pinned layer 32 can be provided on the same substrate 11 in close proximity.

  7A to 7C and FIGS. 8A to 8C are explanatory diagrams of a method of manufacturing the magnetoresistive effect elements 12a to 12d in the current sensor 1 according to the present embodiment. In the manufacturing method of the current sensor 1 according to the present embodiment, the magnetoresistive effect elements 12b and 12c are formed after the magnetoresistive effect elements 12a and 12d are formed. First, as shown in FIG. 7A, on the aluminum oxide film 22, a seed layer 31, a first ferromagnetic film 33, an antiparallel coupling film 34, a second ferromagnetic film 35, a nonmagnetic intermediate layer 36, a free magnetic layer. A layer 37 and a protective layer 38 are sequentially formed. During the formation of the first ferromagnetic film 33 and the second ferromagnetic film 35, a magnetic field is applied in the meander-shaped stripe width direction. 7A to 7C, the applied magnetic field direction of the first ferromagnetic film 33 (Pin1) is the direction from the back side to the near side of the paper, and the second ferromagnetic film 35 (Pin2) is applied. The direction of the magnetic field is the direction from the front side to the back side of the page. However, for the second ferromagnetic film 35, it is not always necessary to apply a magnetic field in this direction. The same direction as the first ferromagnetic film 33 or no magnetic field may be used. This is because exchange coupling works via the antiparallel coupling film 34 and the magnetization direction is always determined in an antiparallel direction to the first ferromagnetic film 33. In this case, it is important to optimize the film thickness of the antiparallel coupling film 34 and match the Ms · t of the first ferromagnetic film 33 and the second ferromagnetic film 35. During the formation of the free magnetic layer 37, a magnetic field is applied in the longitudinal direction of the meander stripe.

  Next, as shown in FIG. 7B, a resist layer 40 is formed on the protective layer 38, and the resist layer 40 is left on the regions of the magnetoresistive effect elements 12a and 12d by photolithography and etching. Next, as shown in FIG. 7C, the exposed laminated film is removed by ion milling or the like to expose the aluminum oxide film 22 in the region where the magnetoresistive effect elements 12b and 12c are provided.

  Next, as shown in FIG. 8A, after removing the resist layer 40, the seed layer 31, the first ferromagnetic film 33, the antiparallel coupling film 34, and the second ferromagnetic material are formed on the exposed aluminum oxide film 22. A film 35, a nonmagnetic intermediate layer 36, a free magnetic layer 37, and a protective layer 38 are sequentially formed. During the formation of the first ferromagnetic film 33 and the second ferromagnetic film 35, a magnetic field is applied in the meander-shaped stripe width direction. 8A to 8C, for the first ferromagnetic film 33 (Pin1) to be the magnetoresistive effects 12a and 12d, the direction of the applied magnetic field is the direction from the back side to the front side of the page, and the magnetoresistive effect 12b, For the first ferromagnetic film 33 (Pin1) to be 12c, the direction of the applied magnetic field is the direction from the front side of the page toward the back side of the page. In addition, for the second ferromagnetic film 35 (Pin2) that becomes the magnetoresistive effects 12a and 12d, the direction of the applied magnetic field is the direction from the front side to the back side of the paper surface, and the second ferromagnetic film 35 that becomes the magnetoresistive effects 12b and 12c. For the ferromagnetic film 35 (Pin 2), the applied magnetic field direction is the direction from the back side to the front side of the drawing. During the formation of the free magnetic layer 37, a magnetic field is applied in the longitudinal direction of the meander stripe.

  Next, as shown in FIG. 8B, a resist layer 40 is formed on the protective layer 38, and the resist layer 40 is left on the formation regions of the magnetoresistive effect elements 12a, 12b, 12c, and 12d by photolithography and etching. Next, as shown in FIG. 8C, the exposed laminated film is removed by ion milling or the like, and magnetoresistive effect elements 12a, 12b, 12c, and 12d are formed in an arrangement as shown in FIG.

  According to such a current sensor manufacturing method, there is no step in the formation of the magnetoresistive effect elements 12a to 12d. Therefore, the wiring can be easily formed, and the thickness of the wiring can be increased or the through hole can be formed. An additional process becomes unnecessary. Therefore, it is possible to easily manufacture a current sensor in which a plurality of magnetoresistive elements 12a to 12d having different sensitivity axes are provided close to each other on the same substrate 11.

  As described above, since the current sensor 1 according to the above embodiment includes the self-pinned magnetoresistive effect elements 12a to 12d, the magnetization direction of the ferromagnetic pinned layer 32 without providing an antiferromagnetic layer. Can be fixed in any direction, so that the magnetization direction of the ferromagnetic pinned layer 32 of each of the magnetoresistive effect elements 12a to 12d can be set to an arbitrary direction even when four magnetoresistive effect elements are arranged in parallel on the substrate. Can be fixed. As a result, a current-drawing type current sensor using a conductor extending in one direction can be realized, so that the current to be measured flows through the conductor 13 as compared with the case where a conductor having a curved shape is used. The resistance due to the conductor 13 can be reduced, and the loss of the current to be measured and the heat generation due to the flow of the current to be measured can be suppressed. Furthermore, since the direction of the induced magnetic field from the current to be measured can be aligned, it is possible to suppress the interference of the induced magnetic field and the generation of induced electromotive force against the disturbance magnetic field, and a current sensor with a wide measurement range and high measurement accuracy can be obtained. realizable.

  In particular, in the above embodiment, the pair of magnetoresistive elements 12a and 12b are disposed along the first section S1 having a relatively large cross-sectional area of the conductor 13, and the other pair of magnetoresistive elements. Since 12c and 12d are disposed along the second section S2 having a relatively small cross-sectional area, an induced magnetic field applied to the pair of magnetoresistive elements 12a and 12b and another pair of magnetoresistances The effect elements 12c and 12d and the induced magnetic field applied have different magnetic field strengths. Accordingly, the output signals output from the pair of magnetoresistive effect elements 12a and 12b and the output signals output from the other pair of magnetoresistive effect elements 12c and 12d have different signal strengths. The measured current can be measured by the magnetic field detection bridge circuit without using.

  Further, the magnetization direction of the ferromagnetic pinned layer 32 of the pair of magnetoresistive effect elements 12a and 12b and the magnetization direction of the ferromagnetic pinned layer 32 of the other pair of magnetoresistive effect elements 12c and 12d are fixed in the same direction. Therefore, the output signals output from the pair of magnetoresistance effect elements 12a and 12b and the output signals output from the other pair of magnetoresistance effect elements 12c and 12d are in phase due to disturbance noise. Furthermore, due to the current to be measured, the induced magnetic field applied to the pair of magnetoresistive effect elements 12a and 12b and the induced magnetic field applied to the other pair of magnetoresistive effect elements 12c and 12d have different magnetic field strengths. Since the output signals output from the magnetoresistive effect elements 12a and 12b and the output signals output from the other pair of magnetoresistive effect elements 12c and 12d have different signal strengths in the same phase, the differential output is Occur. As a result, an output signal derived from an induced magnetic field from the current to be measured is obtained by a differential output between the output signals of the pair of magnetoresistive effect elements 12a and 12b and the output signals of the other pair of magnetoresistive effect elements 12c and 12d. As a result, disturbance noise components are canceled out, so that a current sensor with high detection sensitivity and high measurement accuracy can be realized.

  Further, in the current sensor according to the above-described embodiment, the magnetic field detection bridge circuit can be configured without using a fixed resistance element, so that offset can be reduced and a conductor extending in one direction can be used. Since the current to be measured can be measured, the area of the substrate can be reduced, and the current sensor can be downsized and the manufacturing cost can be reduced. In addition, since it is possible to configure the magnetoresistive element without using an antiferromagnetic material, it is possible to ensure the stability of the operation of the current sensor 1 even in a high temperature environment and not to use an antiferromagnetic material. Therefore, it is possible to reduce the manufacturing cost because the material cost and the annealing process in the magnetic field are not required.

In the current sensor according to the above embodiment, since the magnetic detection bridge circuit is composed of four magnetoresistive effect elements having the same film configuration, the zero magnetic field resistance value (R ₀ ) and the resistance temperature coefficient between the elements. The deviation of (TCR ₀ ) can be eliminated. For this reason, the variation in the midpoint potential can be reduced regardless of the environmental temperature, and the measurement accuracy of the current to be measured can be improved.

  In the above embodiment, the pair of magnetoresistive elements 12a and 12b are disposed with the region on the electrode pad 13a side of the conductor 13 as the first section S1, and the region on the electrode pad 13b side of the conductor 13 is defined. Although the configuration in which the other pair of magnetoresistive elements 12c and 12d is disposed as the second section S2 has been described, the arrangement of the magnetoresistive elements 12a to 12d is the pair of magnetoresistive elements 12a and 12b and the other pair. As long as the arrangement is such that output signals having different signal strengths are output from the magnetoresistive effect elements 12c and 12d, the magnetoresistive effect elements 12c and 12d can be appropriately changed. For example, both ends of the conductor 13 in the extending direction D1 are respectively set as the first section S1, and the pair of magnetoresistive effect elements 12a and 12b are respectively disposed, and the section between the first sections S1 is set as the second section S2. Another pair of magnetoresistive elements 12c and 12d may be provided. Further, in the extending direction D1 of the conductor 13, the first section S1 and the second section S2 are provided alternately from the electrode pad 13a side to the electrode pad 13b side of the conductor 13, thereby providing a pair of magnetoresistive elements. You may arrange | position 12a, 12b and another pair of magnetoresistive effect elements 12c, 12d.

  Moreover, in the said embodiment, the width dimension L1 of 1st area S1 and the width dimension L2 of 2nd area S2 are made into different magnitude | sizes, and 1st area S1 and 2nd area of mutually different cross-sectional area are set. Although the configuration of the conductor 13 having S2 has been described, a configuration in which the cross-sectional areas of the first section S1 and the second section S2 are made different from each other is a pair of magnetoresistance effect elements 12a and 12b and another pair of magnetoresistance effects. If output signals having different signal intensities are output from the elements 12c and 12d, they can be appropriately changed. For example, the width dimensions L1 and L2 of the conductor 13 are the same, and the dimensions (thicknesses) in the height direction D3 perpendicular to the extending direction D1 and the width direction D2 of the conductor 13 are different from each other. The conductor 13 having the first section S1 and the second section S2 may be used.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. In the following, differences from the current sensor 1 according to the first embodiment will be mainly described to avoid duplication of description. In addition, the same code | symbol is attached | subjected to the component same as the current sensor 1 which concerns on the said 1st Embodiment.

  FIG. 9 is a schematic plan view of the current sensor 2 according to the present embodiment, and FIG. 10 is a schematic cross-sectional view taken along the line XX in FIG. In the current sensor 2 according to the present embodiment, the conductor 51 is provided so as to extend in one direction, and has a uniform width dimension L1. The magnetoresistive elements 12 a to 12 d are arranged in parallel along the extending direction D <b> 1 of the conductor 51.

  In the current sensor 2, a region on the electrode pad 13a side where the pair of magnetoresistive effect elements 12a and 12b are disposed on the substrate 11 and an electrode pad 13b where the other pair of magnetoresistive effect elements 12c and 12d are disposed. The laminated structure differs depending on the region on the side. In the current sensor 2, the pair of magnetoresistive elements 12a and 12b are disposed in the first plane (see F1) in the first section S1, and the other pair of magnetoresistive elements 12c and 12d are second. In the section S2, it is disposed in the second plane (see F2). Therefore, in the current sensor 2, the distance L3 between the pair of magnetoresistance effect elements 12a and 12b and the conductor 13 in the height direction D3 of the conductor 13, and the other pair of magnetoresistance effect elements 12c and 12d. Since the distance L4 between the conductor 13 and the conductor 13 is different from each other, the induced magnetic field applied to the pair of magnetoresistive elements 12a and 12b and the induced magnetic field applied to the other pair of magnetoresistive elements 12c and 12d And have different magnetic field strengths. As a result, the output signals output from the pair of magnetoresistive elements 12a and 12b and the output signals output from the other pair of magnetoresistive elements 12c and 12d have different signal intensities. The current to be measured can be measured by the circuit.

  In the region on the electrode pad 13 a side, a silicon oxide film 21 is provided on the substrate 11, and magnetoresistive effect elements 12 a and 12 b are disposed on the silicon oxide film 21 via an aluminum oxide film 22. Hard bias layers 14 for applying a bias magnetic field to the free magnetic layers 37 of the magnetoresistive effect elements 12a and 12b are provided at both ends of the magnetoresistive effect elements 12a and 12b. An insulating layer 23, an aluminum oxide film 52, an insulating layer 53, a conductor 51, and the like are stacked on the magnetoresistive effect elements 12a and 12b.

  In the region on the electrode pad 13 b side, a silicon oxide film 21, an aluminum oxide film 22, and an insulating layer 23 are stacked in this order on the substrate 11, and the magnetoresistive effect element 12 c is formed on the insulating layer 23 via an aluminum oxide film 52. , 12d are disposed. Hard bias layers 14 for applying a bias magnetic field to the free magnetic layers 37 of the magnetoresistive effect elements 12c and 12d are provided at both ends of the magnetoresistive effect elements 12c and 12d. An insulating layer 53, a conductor 51, and the like are stacked on the magnetoresistive effect elements 12a and 12b. Since the other laminated structure is the same as that of the current sensor 1 according to the first embodiment, the description thereof is omitted.

  As described above, the current sensor 2 has a different stacked structure in the region on the electrode pad 13a side of the conductor 51 and the region on the electrode pad 13b side, and the pair of magnetoresistive effect elements 12a and 12b and the conductor 13 are provided. Is larger than the distance L4 between the other pair of magnetoresistive elements 12c and 12b and the conductor 13. With this configuration, the magnetic field strength of the induced magnetic field applied to the pair of magnetoresistive effect elements 12a and 12b is relative to the magnetic field strength of the induced magnetic field applied to the other pair of magnetoresistive effect elements 12c and 12d. Become smaller. As a result, the output signals output from the pair of magnetoresistive elements 12a and 12b and the output signals output from the other pair of magnetoresistive elements 12c and 12d have different signal strengths. It becomes possible to measure the current to be measured.

(Third embodiment)
Next, a third embodiment of the present invention will be described. In the following, differences from the current sensors 1 and 2 according to the first and second embodiments will be mainly described to avoid duplication of description. In addition, the same code | symbol is attached | subjected to the component same as the current sensor 1 which concerns on the said 1st Embodiment.

  FIG. 11 is a schematic cross-sectional view of the current sensor 3 according to the present embodiment. In the current sensor 3 according to the present embodiment, the conductor 61 includes first and second conductive paths 61a and 61b extending in the same direction, and the first conductive path 61a and the second conductive path 61b. And a third conductive path 61c to be connected. The first and second conductive paths 61a and 61b are provided so as to extend parallel to the surface of the substrate 11, and the relative positions in the height direction D3 orthogonal to the extending direction D1 of the conductor 61 are They are provided differently. In the present embodiment, the first conductive path 61a is the first section S1, and the second conductive path 61b is the second section S2.

  In the present embodiment, the conductor 61 is provided such that the distance between the surface of the substrate 11 and the first conductive path 61a is smaller than the distance between the surface of the substrate 11 and the second conductive path 61b. It is done. An electrode pad 13a is provided on one end side of the first conductive path 61a, and an electrode pad 13b is provided on the other end side of the second conductive path 61b. The other end of the first conductive path 61a and one end of the second conductive path 61b are connected by a third conductive path 61c.

  The magnetoresistive elements 12a to 12d are juxtaposed along the extending direction of the conductor 61, and are arranged in the same plane (see F3). A pair of magnetoresistive elements 12a and 12b are disposed along the first conductive path 61a, and the other pair of magnetoresistive elements 12c and 12d are disposed along the second conductive path 61b. . In the present embodiment, in the height direction D3 orthogonal to the extending direction D1 of the conductor 13, the distance L5 between the pair of magnetoresistive elements 12a and 12b and the first conductor 61a is other than It arrange | positions so that it may become relatively small with respect to the distance L6 between a pair of magnetoresistive effect elements 12c and 12d and the 2nd conductive path 61b. The magnetoresistive effect elements 12a to 12d are output from the pair of magnetoresistive effect elements 12a and 12b and the other pair of magnetoresistive effect elements 12c and 12d by the induced magnetic field from the current to be measured. As long as the output signal is different from the output signal, the configuration is not limited to the configuration in which the output signals are arranged in the same plane.

  Thus, in the current sensor 3 according to the present embodiment, the distance L5 between the pair of magnetoresistive elements 12a and 12b and the first conductive path 61a is equal to the other pair of magnetoresistive elements 12c, Since the distance L6 is smaller than the distance L6 between 12d and the second conductive path 61b, the magnetic field strength of the induced magnetic field applied to the pair of magnetoresistive elements 12a and 12b is different from that of the other pair of magnetoresistive elements 12c. , 12d becomes relatively large with respect to the magnetic field strength of the induction magnetic field applied to 12d. As a result, the output signals output from the pair of magnetoresistive elements 12a and 12b and the output signals output from the other pair of magnetoresistive elements 12c and 12d have different signal strengths. It becomes possible to measure the current to be measured.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described. In the following, differences from the current sensors 1, 2, and 3 according to the first, second, and third embodiments will be mainly described to avoid duplication of description. In addition, the same code | symbol is attached | subjected to the component same as the current sensors 1, 2, and 3 which concern on the said 1st, 2nd and 3rd embodiment.

  FIG. 12 is a schematic cross-sectional view of the current sensor 4 according to the present embodiment. In the current sensor 4 according to the present embodiment, the pair of magnetoresistive elements 12a and 12b and the other pair of magnetoresistive elements 12c and 12d have an application direction of an induced magnetic field from the current I to be measured. It arrange | positions so that it may apply from a mutually reverse direction. In the present embodiment, the pair of magnetoresistive elements 12a and 12b are arranged on the lower surface side in the first section S1 on the electrode pad 13a side of the conductor 13 with respect to the extending direction of the conductor 13 in a sectional view. Then, the other pair of magnetoresistive elements 12c and 12d are disposed on the upper surface side in the second section S2 on the electrode pad 13b side of the conductor 13 with respect to the extending direction of the conductor 13 in a sectional view. With this configuration, the induced magnetic field when the current I to be measured flows through the conductor 13 from the electrode pad 13a side to the electrode pad 13b side is from the front side of the sheet with respect to the pair of magnetoresistive effect elements 12a and 12b. It is applied toward the back side of the paper, and applied to the other pair of magnetoresistive elements 12c and 12d from the back side of the paper toward the front of the paper. As a result, the output signals output from the pair of magnetoresistive elements 12a and 12b and the output signals output from the other pair of magnetoresistive elements 12b are out of phase, so that the current to be measured can be measured. It becomes.

  In the region on the electrode pad 13 a side, a silicon oxide film 21 is provided on the substrate 11, and magnetoresistive effect elements 12 a and 12 b are disposed on the silicon oxide film 21 via an aluminum oxide film 22. Hard bias layers 14 for applying a bias magnetic field to the free magnetic layers 37 of the magnetoresistive effect elements 12a and 12b are provided at both ends of the magnetoresistive effect elements 12a and 12b. On the magnetoresistive effect elements 12a and 12b, the insulating layer 24, the conductor 13, the insulating layer 24, the aluminum oxide film 52, and the silicon oxide film 26 are laminated in this order.

  In the region on the electrode pad 13 b side, a silicon oxide film 21, an aluminum oxide film 22, an insulating layer 23, a conductor 13, and an insulating layer 24 are stacked in this order on the substrate 11, and an aluminum oxide film is formed on the insulating layer 24. The magnetoresistive effect elements 12 c and 12 d are disposed via 52. Hard bias layers 14 for applying a bias magnetic field to the free magnetic layers 37 of the magnetoresistive effect elements 12c and 12d are provided at both ends of the magnetoresistive effect elements 12c and 12d. A silicon oxide film 26 is laminated on the magnetoresistive effect elements 12c and 12d. The other laminated structure is the same as that of the current sensors 1, 2, and 3 according to the first, second, and third embodiments, and thus the description thereof is omitted.

  As described above, in the current sensor 4 according to the present embodiment, the pair of magnetoresistive elements 12a and 12b and the other pair of magnetoresistive elements 12c and 12d apply an induced magnetic field from the current to be measured. It arrange | positions so that a direction may be applied from a mutually reverse direction. With this configuration, an induced magnetic field generated when the current to be measured flows through the conductor 13 is applied to the pair of magnetoresistive effect elements 12a and 12b from the front of the paper to the back of the paper. The pair of magnetoresistive elements 12c and 12d are applied from the back side to the front side. As described above, the direction in which the induction magnetic field is applied to the pair of magnetoresistance effect elements 12a and 12b and the direction in which the induction magnetic field is applied to the other pair of magnetoresistance effect elements 12c and 12d are different from each other. The output signals output from the resistance effect elements 12a and 12b and the output signals output from the other pair of magnetoresistance effect elements 12c and 12d have different signal strengths. As a result, the current to be measured can be detected by the magnetic field detection bridge circuit.

  In addition, this invention is not limited to the said embodiment, It can change and implement variously. In the above embodiment, terms such as “same”, “parallel”, “antiparallel”, “in-phase”, “reverse phase”, etc., are completely “same” as long as they are within the range in which the effects of the present invention are exhibited. ”,“ Parallel ”,“ antiparallel ”,“ in-phase ”, and“ reverse phase ”. Further, in the above embodiment, “anti-parallel” means directions that are 180 ° different from each other and opposite to each other. Furthermore, in the above-described embodiment, the size, shape, and the like illustrated in the accompanying drawings are not limited thereto, and can be appropriately changed within a range in which the effect of the present invention is exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  INDUSTRIAL APPLICABILITY The present invention has the effect of realizing a current sensor that is excellent in operational stability at high temperatures and has high measurement accuracy. It is possible to apply to.

  This application is based on Japanese Patent Application No. 2011-044711 of an application on March 2, 2011. All this content is included here.

Claims (6)

At least two pairs of magnetoresistive effects for outputting an output signal by a conductor extending in one direction and an induced magnetic field from a current to be measured that flows in parallel along the extending direction of the conductor and flows through the conductor Comprising an element,
The magnetoresistive element has a laminated structure including a ferromagnetic fixed layer whose magnetization direction is fixed, a nonmagnetic intermediate layer, and a free magnetic layer whose magnetization direction varies with respect to an external magnetic field. Is a self-pinning type in which the first ferromagnetic film and the second ferromagnetic film are antiferromagnetically coupled via the antiparallel coupling film,
The at least two pairs of magnetoresistive elements are a pair of magnetoresistive elements disposed along the first section of the conductor and another pair disposed along the second section of the conductor. Magnetoresistive effect element, and
The pair of magnetoresistive elements and the other pair of magnetoresistive elements are arranged so that the induced magnetic fields are applied with different strengths or the induced magnetic fields are applied from different directions. A current sensor characterized by that.   A first half-bridge circuit including the pair of magnetoresistive effect elements; and a second half-bridge circuit including the other pair of magnetoresistive effect elements, and each magnetoresistive of the first half-bridge circuit. 2. The magnetization direction of the ferromagnetic pinned layer in the effect element and the magnetization direction of the ferromagnetic pinned layer in each magnetoresistive effect element of the second half-bridge circuit are the same. The current sensor described.   The magnetization directions of the ferromagnetic pinned layers of the pair of magnetoresistance effect elements are antiparallel to each other, and the magnetization directions of the ferromagnetic pinned layers of the other pair of magnetoresistance effect elements are antiparallel to each other. The current sensor according to claim 1 or 2.   2. The conductor according to claim 1, wherein a cross-sectional area of the first section in a vertical section with respect to the extending direction is different from a cross-sectional area of the second section in a vertical section with respect to the extending direction. The current sensor according to claim 3.   The distance between the pair of magnetoresistive elements and the first section of the conductor is different from the distance between the other pair of magnetoresistive elements and the second section of the conductor. The current sensor according to any one of claims 1 to 4, wherein:   The pair of magnetoresistive effect elements and the other pair of magnetoresistive effect elements are arranged so that the induction magnetic fields are applied in directions opposite to each other. The current sensor according to claim 5.

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