JP2022077691A - Magnetic sensor, magnetoresistive effect element and current sensor - Google Patents

Abstract

To provide a magnetic sensor excellent in perpendicular magnetic field resistance that reduces offset change generated by hysteresis if a free magnetic layer is subjected to a strong magnetic field in a direction perpendicular to a sensitivity axial direction and causes magnetization inversion.SOLUTION: A magnetic sensor 10 comprises magnetoresistive effect elements 11a-11d. The magnetoresistive effect elements 11a-11d each have a fixed magnetic layer, and a free magnetic layer stacked via a nonmagnetic material layer on the fixed magnetic layer. Pairs of magnetoresistive effect elements 11a and 11b, 11c and 11d having the fixed magnetic layers magnetized in a reverse direction (Pin layer magnetization direction) form half bridge circuits 12a, 12b. Each of the magnetoresistive effect elements includes regions 13A and 13B which are applied a reversed bias magnetic field by an antiferromagnetic layer.SELECTED DRAWING: Figure 1

Description

The present invention relates to a magnetic sensor having regions in which the direction of bias magnetization is different in one magnetoresistive effect element, a magnetoresistive effect element, 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. Therefore, there is a demand for a current sensor capable of measuring a large current in a non-contact manner. 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.

The GMR element has a fixed magnetic layer, a non-magnetic material layer, and a free magnetic layer as a basic film structure. The magnetization direction of the fixed magnetic layer is fixed in one direction. The free magnetic layer is laminated on the fixed magnetic layer via a non-magnetic material layer (non-magnetic intermediate layer), and the magnetization direction is changed by an external magnetic field. In a magnetic sensor equipped with a GMR element, the electricity of the GMR element fluctuates depending on the relationship between the magnetization direction of the free magnetic layer that changes due to the application of an induced magnetic field (measured magnetic field) from the measured current and the magnetization direction of the fixed magnetic layer. The current value of the measured current is detected by the resistance value.

The magnetic sensor equipped with the GMR element is provided with a configuration in which a bias magnetic field is applied to the free magnetic layer by the antiferroelectric layer in order to enhance the linear relationship between the electric resistance value of the GMR element and the strength of the external magnetic field. A magnetic sensor has been proposed (see, for example, Patent Document 1). In such a magnetic sensor, a bias magnetic field is applied in a direction orthogonal to the sensitivity axis direction in which an induced magnetic field is applied to each GMR element on the same chip, and the magnetization directions of the free magnetic layers are aligned in the same direction. Therefore, the bulkhausen jump after applying a strong magnetic field is suppressed.

In the magnetic sensor described in the same document, a bias magnetic field is applied to the free magnetic layer by the antiferromagnetic layer so that the magnetization directions of the free magnetic layers of the pair of magnetoresistive elements forming the half-bridge circuit are opposite to each other. Apply. As a result, the resistance to a strong magnetic field is improved, and the decrease in the linearity of the sensor output due to the sticking error at the time of die bonding is suppressed.

Japanese Unexamined Patent Publication No. 2014-63893

However, in the magnetic sensor of the same document, when the magnetization direction of the free magnetic layer is reversed from the bias magnetization direction by receiving a strong magnetic field in the direction orthogonal to the sensitivity axis direction, the offset change of the resistance due to the hysteresis thereafter occurs. There is a problem that it is easy to happen.
An object of the present invention is to provide a magnetic sensor having excellent resistance to orthogonal magnetic fields, in which the offset change of resistance caused by hysteresis is reduced when the free magnetic layer is magnetized and inverted.

The present invention provided to solve the above problems includes, in one embodiment, a plurality of magnetic resistance effect elements, wherein the magnetic resistance effect elements are fixed via a fixed magnetic layer and a non-magnetic material layer, respectively. A half-bridge circuit is formed by the pair of magnetic resistance effect elements having a free magnetic layer laminated on the magnetic layer and the magnetization direction of the fixed magnetic layer is opposite to each other, and the half-bridge circuit is formed. Each of the magnetic resistance effect elements provides a magnetic sensor characterized by having a region to which a bias magnetic field in the opposite direction is applied by exchange coupling with an anti-ferrometric layer.
Since each magnetoresistive sensor has a region to which a bias magnetic field in the opposite direction is applied, it is possible to reduce the offset change after the orthogonal magnetic field is applied. Therefore, the resistance to the magnetic field in the direction orthogonal to the sensitivity axis of the magnetic sensor can be improved.

The antiferromagnetic layer may be laminated on the free magnetic layer. By the exchange bias of the antiferromagnetic layer laminated on the free magnetic layer, a bias magnetic field in the opposite direction can be applied to the free magnetic layer.

It is preferable that the free magnetic layer of the magnetoresistive sensor has the same area of the region to which the bias magnetic field in the opposite direction is applied. Each magnetoresistive sensor may have a meander shape, and the regions to which the bias magnetic field in the opposite direction is applied may be formed adjacent to each other.
With the above configuration, when a strong magnetic field is applied in the direction orthogonal to the sensitivity axis of the magnetic sensor, the region where the magnetization direction reverses from the bias magnetization direction is halved, so the offset change due to the hysteresis of the free magnetic layer can be obtained. Can be reduced.

The antiferromagnetic layer may be provided adjacent to the free magnetic layer.
The magnetic sensor may have a full-bridge circuit including a plurality of the half-bridge circuits formed by the pair of magnetoresistive elements.

As another aspect of the present invention, the magnetic sensor of the present invention is provided, and the magnetic sensor provides a current sensor in which an induced magnetic field of a measured current is a measured magnetic field.
Further, as another aspect of the present invention, the present invention has a fixed magnetic layer and a free magnetic layer laminated on the fixed magnetic layer via a non-magnetic material layer, and the free magnetic layers are each antiferromagnetic. Provided is a magnetoresistive effect element characterized by having a region to which a bias magnetic field in the opposite direction is applied by exchange coupling with a magnetic layer.

Since the present invention can reduce the offset change due to hysteresis after the free magnetic layer is magnetized and inverted by receiving a strong magnetic field in the direction orthogonal to the sensitivity axis, the measurement of the magnetic sensor under strong magnetic field conditions can be performed. Accuracy is improved. Further, by using such a magnetic sensor, it is possible to provide a current sensor with good measurement accuracy under a strong magnetic field condition.

Schematic diagram of the magnetic sensor according to the first embodiment of the present invention Explanatory drawing which shows an example of the region where the bias magnetic field in the opposite direction is applied in each magnetoresistive effect element constituting a half bridge. Explanatory drawing showing another example of the region where the reverse bias magnetic field is applied. Explanatory diagram of the state where an external magnetic field is applied to the magnetic sensor of FIG. 1 at an angle deviated from the sensitivity axis direction. Explanatory diagram of sensitivity change with respect to an external magnetic field at an angle deviated from the sensitivity axis direction Explanatory drawing of manufacturing method of the full bridge magnetic sensor of this invention Schematic diagram of the magnetic sensor according to the second embodiment of the present invention. Explanatory drawing of the process of forming the bias magnetic field application part of the magnetic sensor of FIG. Explanatory drawing schematically showing the laminated structure provided in the magnetoresistive element of the first embodiment. Explanatory drawing of offset of resistance of free magnetic layer due to hysteresis Explanatory drawing of offset of resistance of free magnetic layer due to hysteresis Explanatory drawing schematically showing the laminated structure of the region provided with the free magnetic layer of the magnetoresistive element of the second embodiment. Explanatory drawing schematically showing the laminated structure of the bias magnetic field application part provided with the antiferromagnetic layer which applies a bias magnetic field to a free magnetic layer. A graph showing the amount of offset change after applying a magnetic field in a direction orthogonal to the sensitivity axis to the magnetic sensors of Example 1, Comparative Example 1 and Comparative Example 2. Schematic diagram of a conventional magnetic sensor Explanatory drawing of direction of bias magnetization applied to free magnetic layer of magnetic sensor of FIG. Explanatory diagram of the state where an external magnetic field is applied to the magnetic sensor of FIG. 12 at an angle deviated from the sensitivity axis direction. Explanatory diagram of sensitivity change with respect to an external magnetic field at an angle deviated from the sensitivity axis direction Schematic diagram of a conventional magnetic sensor with improved linearity of sensitivity changes due to angle deviation Explanatory drawing of direction of bias magnetization applied to free magnetic layer of magnetic sensor of FIG. Explanatory diagram of the state where an external magnetic field is applied to the magnetic sensor of FIG. 15 at an angle deviated from the sensitivity axis direction. Explanatory diagram of sensitivity change with respect to an external magnetic field at an angle deviated from the sensitivity axis direction

(First Embodiment)
First, the decrease in linearity that occurs in the conventional magnetic sensor will be described with reference to FIGS. 12 to 17.
FIG. 12 is a schematic diagram of the conventional magnetic sensor 20. As shown in the figure, the magnetic sensor 20 constitutes a full bridge circuit including magnetoresistive elements 21a, 21b, 21c and 21d. In this specification, when the member numbers having letters such as a to d are not distinguished, only the member numbers are used as appropriate. For example, when the magnetoresistive effect elements 21a to 21d are not distinguished, they are referred to as the magnetoresistive effect element 21.
FIG. 13 is an explanatory diagram showing the direction of bias magnetization in the free magnetic layer of the magnetic sensor 20 of FIG.

14A is an explanatory diagram of a state in which an external magnetic field is applied to the magnetic sensor 20 of FIG. 12 at an angle deviated from the sensitivity axis direction, and FIG. 14B is an explanatory diagram of a sensitivity change with respect to an external magnetic field at an angle deviated from the sensitivity axis direction. be. In the graph shown in FIG. 14B, the case where there is a deviation (angle deviation) in the external magnetic field direction with respect to the sensitivity axis direction is shown by a solid line, and the case where there is no angle deviation is shown by a dotted line.

The magnetic sensor 20 may be tilted when the sensor chip provided with the magnetoresistive effect element 21 is attached. In this case, an external magnetic field (induced magnetic field) at an angle deviated from the sensitivity axis direction is applied. The decrease in the linearity of the output of the conventional magnetic sensor 20 due to the angle deviation in the detection direction will be described.

In the magnetoresistive sensor 21, the direction in which the bias magnetic field is applied due to the exchange coupling between the free magnetic layer and the anti-ferrometric layer is orthogonal to the magnetization direction (Pin layer magnetization direction) of the fixed magnetic layer of the magnetoresistive element 21. ing. Therefore, when the angle of the detection direction deviates due to the inclination of the mounting, the direction of the bias magnetization applied to the free magnetic layer of the magnetoresistive sensor 21 intersects diagonally with respect to the application direction of the induced magnetic field. Become.

The bias magnetic field is applied by the pair of magnetoresistive elements 21 so as to be in the same direction (parallel) to each other. Therefore, when an external magnetic field deviated from the sensitivity axis direction of the magnetic sensor 20 is applied, the angular deviation similarly affects the sensitivity of the magnetoresistive effect elements 21a and 21b. As shown in FIG. 14B, both the pair of magnetoresistive element (Posi-GMR) 21a and the magnetoresistive element (Nega-GMR) 21b have a large change in the sensitivity of the external magnetic field in the Y1 (+ Y) direction, and Y2 ( The change in sensitivity of the external magnetic field in the −Y) direction becomes small. This sensitivity change is the same for the pair of magnetoresistive elements 21c and 21d. Therefore, since the influence of the angle deviation differs between the Y1 (+ Y) direction and the Y2 (−Y) direction, the linearity of the output of the magnetic sensor (Bridge) 20 deteriorates due to the angle deviation.

FIG. 15 is a schematic diagram of the conventional magnetic sensor 30 in which the linearity of the output due to the angle deviation is improved. As shown in the figure, the magnetic sensor 30 is in that a bias magnetic field in opposite directions is applied to the magnetoresistive effect elements 31a and 31b and the magnetoresistive effect elements 31c and 31d constituting the pair of half bridges. , It is different from the magnetic sensor 20 of FIG.

FIG. 16 is an explanatory diagram showing the direction of bias magnetization in the free magnetic layer of the magnetic sensor 30 of FIG.
FIG. 17A is an explanatory diagram of a state in which an external magnetic field is applied to the magnetic sensor 30 of FIG. 15 at an angle deviated from the sensitivity axis direction, and FIG. 17B is an explanatory diagram of a sensitivity change with respect to an external magnetic field at an angle deviated from the sensitivity axis direction. be. In the graph shown in FIG. 17B, the case where there is a deviation (angle deviation) in the external magnetic field direction with respect to the sensitivity axis direction is shown by a solid line, and the case where there is no angle deviation is shown by a dotted line.

The magnetoresistive sensor 31 is the same as the magnetoresistive element 21 in that the direction of the bias magnetization applied to the free magnetic layer intersects the induced magnetic field diagonally when an angular deviation in the detection direction occurs. be. However, the magnetic sensor 30 is different from the magnetic sensor 20 in a configuration in which a bias magnetic field is applied so that the pair of magnetoresistive elements 31a and 31b are in opposite directions (antiparallel) to each other. The angular deviation of the external magnetic field has an adverse effect on the sensitivities of the magnetoresistive elements 31a and 31b. Therefore, the influence of the angle of the external magnetic field becomes about the same in the Y1 (+ Y) direction and the Y2 (−Y) direction when the pair of magnetoresistive elements 31a and 31b are averaged. This also applies to the pair of magnetoresistive elements 31c and 31d. Therefore, since the influence of the angle deviation is the same in the Y1 (+ Y) direction and the Y2 (−Y) direction, the output of the magnetic sensor (Bridge) 30 does not deteriorate in linearity due to the angle deviation and becomes good.

As described above, by applying a bias magnetic field in the opposite direction to the pair of magnetoresistive elements, the linearity of the output of the magnetic sensor is improved. However, in order to suppress the multimagnetic domain of the free magnetic layer, when an exchange bias magnetic field is applied by laminating an anti-hydrosteretic layer such as IrMn adjacent to the free magnetic layer, a strong magnetic field in the direction perpendicular to the sensitivity axis is received. When the free magnetic layer is magnetized and inverted, there is a problem that an offset change due to hysteresis is likely to occur. This problem cannot be improved by applying a bias magnetic field in the opposite direction to the pair of magnetoresistive elements. In order to reduce the hysteresis, it is effective to increase the Hex (strength of the exchange bias magnetic field), but there is a problem that the sensitivity of the magnetic sensor is lowered.

The offset that occurs in the free magnetic layer in a magnetoresistive element such as a GMR element (giant magnetoresistive element) used in a current sensor or a magnetic sensor will be described below.
FIG. 8 is an explanatory diagram schematically showing a laminated structure included in the magnetoresistive effect element 11. The magnetoresistive effect element 11 has a structure in which a fixed magnetic layer 111, a non-magnetic material layer 112, and a free magnetic layer 113 are laminated. The resistance value changes depending on the relative relationship between the fixed magnetic layer 111 in which the magnetization direction is fixed and the free magnetic layer 113 in which the magnetization direction is changed by an external magnetic field. The magnetic sensor can detect the direction and strength of the external magnetic field based on the change in the resistance value.

When the domain wall moves inside the free magnetic layer 113, Barkhausen noise is generated. Therefore, as a bias magnetic field for stabilizing the output of the magnetic sensor provided with the magnetoresistive effect element 11, an exchange bias magnetic field using exchange coupling with the antiferromagnetic layer 114 is defined by the magnetization direction of the fixed magnetic layer 111. It is given in the direction orthogonal to the sensitivity axis. By applying a bias magnetic field, the magnetization directions of the soft magnetic materials forming the free magnetic layer 113 can be aligned.

A hard bias magnetic field using a permanent magnet may be used as the bias magnetic field, but the permanent magnet has a problem that the magnetization state is changed by a strong magnetic field exceeding the coercive force and the manufacturing process is complicated. By using the exchange bias magnetic field using the antiferromagnetic layer 114, the strong magnetic field resistance is improved and the manufacturing process is simplified. Further, since the direction of the bias magnetization applied to the free magnetic layer 113 can be controlled by the antiferromagnetic layer 114 by the magnetic field direction at the time of film formation, the area where the reverse bias magnetic field is applied to the same magnetoresistive sensor 11 is equal. Regions can be formed.

When a weak external magnetic field whose magnetization direction is not reversed is applied, the free magnetic layer 113 returns to the initial state before the external magnetic field is applied by returning to the zero magnetic field. However, when a strong external magnetic field in which the magnetization direction is reversed is applied, the free magnetic layer 113 does not return to the initial state even if it is returned to the zero magnetic field. That is, when the magnetization direction of the free magnetic layer 113 is reversed by a strong external magnetic field, even if the external magnetic field is removed and the magnetic field returns to zero, the hysteresis of the free magnetic layer 113 causes a deviation (offset) from the initial state.

9A and 9B are explanatory views illustrating the offset of resistance due to the hysteresis of the free magnetic layer. Both show the RH curve when a magnetic field is applied in the direction orthogonal to the sensitivity axis to the GMR element in which the direction of bias magnetization is opposite (antiparallel). In each figure, the case where the applied magnetic field is changed from the negative magnetic field to the positive magnetic field is shown by a solid line, and the case where the applied magnetic field is changed from a positive magnetic field to a negative magnetic field is shown by a broken line.

As shown in FIGS. 9A and 9B, when a strong external magnetic field is applied to the free magnetic layer in the same direction as the bias magnetic field, which is orthogonal to the sensitivity axis, when the external magnetic field returns to zero, the free magnetic layer is initially set. Return to resistance A. Further, when an external magnetic field is applied in the direction opposite to the bias magnetic field, when the applied external magnetic field (orthogonal magnetic field) is smaller than the inverting magnetic field, if the external magnetic field returns to zero, the free magnetic layer becomes the initial resistance A. return. Therefore, when the magnitude of the external magnetic field is from 0 to less than the inverting magnetic field, the resistance of the free magnetic layer becomes A at the initial stage when the external magnetic field becomes zero.

However, when an external magnetic field equal to or larger than the inverting magnetic field is applied in the opposite direction of the bias magnetic field, the free magnetic layer does not return to the initial state even if the external magnetic field returns to zero. For example, after a saturated magnetic field is applied to the free magnetic layer, the resistance of the free magnetic layer changes due to the hysteresis of the free magnetic layer. Therefore, when the external magnetic field becomes zero after the magnetization reversal occurs in the free magnetic layer, the resistance of the free magnetic layer becomes B due to hysteresis instead of the initial A. As described above, when an external magnetic field equal to or larger than the inverting magnetic field is applied in the opposite direction of the bias magnetic field, 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 is applied and the free magnetic layer is inverted from the initial magnetization direction, an offset occurs in the resistance of the free magnetic layer after the magnetic field becomes zero. In this way, the resistance changes due to the hysteresis, which causes the initial value of the resistance to fluctuate. If the resistance of the free magnetic layer fluctuates due to an offset, the detection accuracy of the magnetic sensor deteriorates. Therefore, it is preferable that the offset of the resistance of the free magnetic layer due to an external magnetic field is small.

FIG. 1 is a schematic diagram of the magnetic sensor 10 according to the present embodiment. As shown in the figure, the magnetic sensor 10 includes magnetoresistive effect elements 11a, 11b, 11c and 11d. The four magnetoresistive elements 11 form a full-bridge circuit in which fixed magnetic layers 111 having different magnetization directions are arranged on the same substrate (1 chip).

Each of the magnetoresistive effect elements 11 has a fixed magnetic layer 111 and a free magnetic layer 113 laminated on the fixed magnetic layer 111 via a non-magnetic material layer 112, and the free magnetic layer 113 has anti-strength. The magnetic layers 114 are laminated (see FIG. 8). In the pair of magnetoresistive elements 11a and 11b, the magnetization direction (Pin layer magnetization direction) of the fixed magnetic layer 111 is opposite (antiparallel), forming a half-bridge circuit 12a. Further, the pair of magnetoresistive elements 11c and 11d also form the half-bridge circuit 12b. The magnetic sensor 10 is a full-bridge circuit composed of a half-bridge circuit 12a and a half-bridge circuit 12b formed by a pair of magnetoresistive elements 11.

The free magnetic layer 113 of the magnetoresistive element 11 forming the half-bridge circuit 12 has regions 13A and 13B to which a bias magnetic field in the opposite direction (antiparallel) is applied by exchange coupling with the antiferromagnetic layer 114, respectively. I have. As described above, the magnetoresistive element 11 constituting the half-bridge circuit 12 includes regions 13A and 13B in which the magnetization directions of the free magnetic layer 113 are antiparallel, respectively. With this configuration, it is possible to reduce the offset generated in the resistance of the free magnetic layer 113 in the magnetoresistive effect element 11 when a large magnetic field is applied in the direction orthogonal to the sensitivity axis. Therefore, the strong magnetic field resistance of the magnetic sensor 10 can be improved.

The magnitude of the bias magnetic field applied to the free magnetic layer 113 is not limited, but by laminating the antiferromagnetic layer 114, it is possible to apply a large bias magnetic field such as 3 mT or more, 4 mT or more, and further 5 mT or more. ..

FIG. 2 is an explanatory diagram showing an example of regions 13A and 13B to which a reverse bias magnetic field is applied in the free magnetic layer 113 of each magnetoresistive effect element 11 constituting the half-bridge circuit 12. FIG. 3 is an explanatory diagram showing another example of the regions 13A and 13B. These figures show the magnetization layout of the magnetoresistive element 11, and schematically show the case where the magnetoresistive element 11 is viewed from above. As shown in the figure, the free magnetic layer 113 (see FIG. 8) included in each magnetoresistive sensor 11 has the same area of regions 13A and 13B to which a bias magnetic field in the opposite direction (antiparallel) is applied.

The magnetoresistive sensor 11 includes regions 13A and 13B to which a bias magnetic field in the opposite direction (antiparallel) is applied. Therefore, when a large external magnetic field is applied in the direction orthogonal to the sensitivity axis, magnetization reversal occurs only in one of the regions 13A and 13B. That is, in the same magnetoresistive effect element 11, the region where the resistance changes due to hysteresis is halved. Therefore, the offset of each magnetoresistive sensor 11 can be reduced by half.

Further, since each magnetoresistive effect element 11 of the magnetic sensor 10 is applied with a bias magnetic field in the opposite direction, when a deviation occurs in the angle in the detection direction, the influence of the deviation is canceled by each magnetoresistive effect element 11. Can be done. Therefore, the sensitivity of each magnetoresistive sensor 11 does not change due to the deviation in angle, and the linearity of the magnetic sensor 10 does not change either.

FIG. 4A is an explanatory diagram of a state in which an external magnetic field is applied to the magnetic sensor 10 at an angle deviated from the sensitivity axis direction, and FIG. 4B is an explanatory diagram of a sensitivity change with respect to an external magnetic field at an angle deviated from the sensitivity axis direction. In the graph shown in FIG. 4B, the case where there is a deviation (angle deviation) in the external magnetic field direction with respect to the sensitivity axis direction is shown by a solid line, and the case where there is no angle deviation is shown by a dotted line.

In the magnetoresistive effect element 11, the magnetization directions of the free magnetic layer intersect diagonally with respect to the application direction of the induced magnetic field, respectively, without being orthogonal to each other. However, since each of the magnetoresistive elements 11 and 11b includes regions 13A and 13B in which bias magnetic fields are applied in opposite directions (antiparallel), the angular deviation of the external magnetic field causes the magnetoresistive elements 11a and 11b. The effect on the sensitivity of is equal. Therefore, as shown in FIG. 4B, the magnetoresistive effect element (Posi-GMR) 11a and the magnetoresistive effect element (Nega-GMR) 11b are sensitive to external magnetic fields in the Y1 (+ Y) direction and the Y2 (-Y) direction. The changes are shown in FIG. 4B. This also applies to the magnetoresistive effect elements 11c and 11d. Therefore, the linearity of the output with the magnetic sensor (Bridge) 10 is improved.

As shown in FIGS. 2 and 3, each magnetoresistive sensor 11 has a meander shape (a shape formed by connecting a plurality of long patterns extending in the X direction so as to be folded back), and vice versa. Regions 13A and 13B to which the bias magnetic field of the direction is applied are formed adjacent to each other.

The areas 13A and 13B to which the bias magnetic field in the opposite direction is applied have the same area. Here, the area refers to the area when viewed in a plan view from the normal direction (Z1 in FIG. 2) of the plane composed of the bias magnetization direction and the sensitivity axis direction. In the present invention, "equal area" means that the ratio of the areas of the regions 13A and 13B is set to such an extent that the resistance change due to hysteresis can be suppressed to half. For example, the ratio of the area of the region 13A to the area of the region 13B may be 1: 0.8 to 1: 1.2, preferably 1: 0.9 to 1: 1.1.

By using the exchange bias magnetic field due to the antiferromagnetic layer 114 instead of the hard bias magnetic field, it becomes possible to clearly define whether the free magnetic layer 113 is the region 13A or the region 13B. Further, the magnetoresistive effect element 11 has a meander shape, and an exchange bias magnetic field is applied by the antiferromagnetic layer 114. Therefore, there is no region in which it is unknown whether it belongs to the region 13A or the region 13B. That is, since the antiferromagnetic layer 114 can strictly control the magnetization direction of the bias magnetic field applied to the free magnetic layer 113, it is possible to make the area of the region 13A equal to the area of the region 13B.

As shown in FIG. 1, the input terminal 15 is connected to one end of the magnetoresistive effect element 11a, and the other end of the magnetoresistive effect element 11a and one end of the magnetoresistive effect element 11b are connected in series to form a magnetoresistive effect element. The other end of 11b is connected to the ground terminal 16. The input terminal 15 is also connected to one end of the magnetoresistive element 11c, the other end of the magnetoresistive element 11c and one end of the magnetoresistive element 11d are connected in series, and the other end of the magnetoresistive element 11d is grounded. It is connected to the terminal 16. The first midpoint potential measuring terminal 17 is connected between the other end of the magnetoresistive effect element 11a and one end of the magnetic resistance effect element 11b, and the second midpoint potential measuring terminal 18 is the magnetic resistance effect element 11c. It is connected between the other end of the magnetic resistance effect element 11d and one end of the magnetoresistive sensor 11d. The magnetic sensor 10 induces the measured current in the sensitivity axis direction flowing through the current line by comparing the potential of the first midpoint potential measuring terminal 17 with the potential of the second midpoint potential measuring terminal 18. Measure the strength and direction of the magnetic field (measured magnetic field).

For the magnetic sensor 10 (see FIG. 1), the conventional magnetic sensor 20 (see FIG. 12), and the conventional magnetic sensor 30 (see FIG. 15) of the present embodiment, after the sensitivity changes due to the angle deviation and the magnetic field orthogonal to the sensitivity axis is applied. The table below summarizes the offset changes in.

In the magnetic sensor 10 of the present embodiment, the magnetoresistive effect elements 11a to 11d each have regions 13A and 13B in which the directions of bias magnetization are antiparallel. Therefore, the influence of the angle deviation and the offset change can be reduced in each magnetoresistive effect element 11. Therefore, the linearity of the output of the magnetic sensor 10 becomes good (◯), and the offset change amount becomes small (〇).

In the conventional magnetic sensor 20, the direction of bias magnetization applied to each magnetoresistive effect element 21a to 21d is the same. Therefore, since the offset change amount of each magnetoresistive effect element is the same, the offset change amount of the magnetic sensor 20 including the bridge circuit is small (◯). However, since the influence of the angle deviation on the magnetic sensor 20 differs depending on the direction of the external magnetic field, the linearity of the output is poor (×).

In the conventional magnetic sensor 30, the direction of the bias magnetization applied to the pair of magnetoresistive effect elements 31a and 31b, and 31c and 31d is antiparallel. Therefore, since the influence of the angle deviation can be canceled by the pair of magnetoresistive effect elements, the linearity of the output of the magnetic sensor 30 is good (◯). However, since the amount of offset change of each magnetoresistive sensor differs depending on the direction of bias magnetization, the amount of offset change of the magnetic sensor 30 including the bridge circuit is large (x).

FIG. 5 is an explanatory diagram of a method for manufacturing a full-bridge magnetic sensor of the present invention. Since the fixed magnetic layer of the magnetoresistive sensor 11 included in the magnetic sensor 10 has a self-pin structure, the fixed magnetic layer can be magnetized by film formation in a magnetic field, and heat treatment in a magnetic field is not required after the film formation. Therefore, it is possible to form a full bridge circuit by arranging magnetoresistive elements 11 having different magnetization directions of the fixed magnetic layer on the same substrate.

As shown in FIG. 5, first, a base layer of the magnetoresistive effect element 11 is formed on the substrate (large step No. 1). For the base layer, for example, Al ₂ O ₃ (alumina) or the like is used. Then, with respect to the region 13B of the magnetoresistive effect elements 11a and 11d, the region 13B of the magnetoresistive effect elements 11b and 11c, the region 13A of the magnetoresistive effect elements 11a and 11d, and the region 13A of the magnetoresistive effect elements 11b and 11c, respectively. An area pattern is formed, the magnetoresistive sensor 11 is formed, and lifted off (large steps No. 2 to 4, 5 to 7, 8 to 10 and 11 to 13).

Subsequently, stripe pattern formation, stripe etching, and stripe resist peeling of the magnetoresistive effect element 11 are performed (large steps No. 14 to 16). Then, electrode pattern formation, electrode film formation, and electrode lift-off are performed (large steps No. 17 to 19). The stripe pattern shown in FIG. 5 corresponds to the regions 13A and 13B shown in FIG.

As described above, in the magnetic sensor of the present embodiment, each magnetoresistive sensor has a region in which the direction of bias magnetization is antiparallel, which is applied by the antiferromagnetic layer laminated on the free magnetic layer. Therefore, it is possible to provide a magnetic sensor in which the sensitivity change of each magnetoresistive sensor due to the angle deviation at the time of mounting is small, the linearity of the output is good, and the amount of offset change after applying a magnetic field orthogonal to the sensitivity axis is small.

The present invention can be implemented as a current sensor including a magnetic sensor whose measured magnetic field is an induced magnetic field of the measured current.

<Second embodiment>
FIG. 6 is a schematic diagram of the magnetic sensor 40 according to the present embodiment. As shown in the figure, the magnetic sensor 40 has a configuration (abutted junction) in which an antiferromagnetic layer to which a bias magnetic field is applied is provided adjacent to a free magnetic layer.

The magnetic sensor 40 includes magnetoresistive effect elements 41a, 41b, 41c and 41d. The four magnetoresistive elements 41 form a full-bridge circuit in which fixed magnetic layers having different magnetization directions are arranged on the same substrate (1 chip). Each of the magnetoresistive effect elements 41. It includes regions 43A and 43B to which a bias magnetic field in the opposite direction (antiparallel) is applied. The regions 43A and 43B are sandwiched between the bias magnetic field application portions 44A and 44B, respectively.

FIG. 10A is an explanatory diagram schematically showing a laminated structure of a region 43 including a free magnetic layer 113 of the magnetoresistive element 41 of the present embodiment. As shown in the figure, the regions 43A and 43B of the magnetic sensor 40 are different from the regions 13A and 13B of the magnetic sensor 10 in that the regions 43A and 43B of the magnetic sensor 40 are not provided with the antiferromagnetic layer 114.

The free magnetic layer 113 in the region 43 is sandwiched by the adjacent bias magnetic field application unit 44, and the bias magnetic field is applied by the bias magnetic field application unit 44. The magnetic fields of the adjacent bias magnetic field application portions 44A and 44B are opposite (antiparallel), and the bias magnetic fields in the opposite directions are applied to the regions 43A and 43B.

FIG. 10B is an explanatory diagram schematically showing a laminated structure of a bias magnetic field application portion 44 including an antiferromagnetic layer 114 that applies a bias magnetic field to the free magnetic layer 113 of the region 43. As shown in the figure, the bias magnetic field application unit 44 has a structure in which the magnetic layer 115 is sandwiched between the antiferromagnetic layer 114. Therefore, the direction of the bias magnetization applied to the free magnetic layer 113 in the region 43 between them can be controlled by the direction of the magnetic field applied when the magnetic layer 115 and the antiferromagnetic layer 114 are formed.

As shown in FIG. 6, in the pair of magnetoresistive effect elements 41a and 41b, the magnetization direction (Pin layer magnetization direction) of the fixed magnetic layer 111 is opposite (antiparallel), forming a half-bridge circuit 42a. .. Further, the pair of magnetoresistive elements 41c and 41d also form the half-bridge circuit 42b.

The bias magnetic field application unit 44 can be implemented, for example, by the following laminated structure. The numbers in parentheses indicate an example of layer thickness (Å).
Protective layer: Ta (30) / Underlayer: NiFeCr (50) / Antiferromagnetic layer: IrMn (80) / Magnetic layer: Fe 30at _% Co _70at% (180-360) / Antiferromagnetic layer: IrMn (80) / Protective layer: Ta (150)

FIG. 7 is an explanatory diagram of a process of forming the bias magnetic field application portion 44 in the magnetic sensor 40, and schematically shows a cross section along the line AA of FIG. As shown in the figure, the bias magnetic field application portion 44A is formed on the substrate 200 by the following steps.
[1] The magnetoresistive effect element 201 is formed on the substrate 200.
[2] The resist 202 is applied to the surface of the magnetoresistive effect element 201.
[3] The bias magnetic field application unit 44A is patterned (the first patterning of the bias magnetic field application unit 44).
[4] Of the exposed magnetoresistive element 201, the portion forming the bias magnetic field application portion 44A is etched (the portion that becomes the region 43A remains on the back side of the drawing of the etched portion).
[5] In a magnetic field (magnetic field), a bias magnetic field application section 44A is formed on the exposed substrate 200 (first bias magnetic field application section 44 film formation). The magnetic field direction of the bias magnetic field application unit 44A is determined by the magnetic field direction at this time (facing toward FIG. 7).
[6] Lift off the resist 202. As a result, the bias magnetic field application portion 44A that applies the bias magnetic field to the free magnetic layer 113 of the region 43A can be formed on the substrate 200.

Subsequently, the bias magnetic field application portion 44B is formed on the substrate 200 by the following steps.
[7] The resist 202 is applied to the surface of the magnetoresistive effect element 201.
[8] The bias magnetic field application unit 44B is patterned on the resist 202 (the second patterning of the bias magnetic field application unit 44).
[9] Of the exposed magnetoresistive element 201, the portion forming the bias magnetic field application portion 44B is etched (the portion that becomes the region 43B remains on the back side of the drawing of the etched portion).
[10] A bias magnetic field application unit 44B is formed on the exposed substrate 200 in a magnetic field (magnetic field) (second bias magnetic field application unit 44 film formation). The magnetic field direction of the bias magnetic field application unit 44B is determined by the magnetic field direction at this time (inward toward FIG. 7).
[11] The resist 202 is lifted off. As a result, the bias magnetic field application portion 44B that applies the bias magnetic field to the free magnetic layer 113 of the region 43B can be formed on the substrate 200.
[12] Anneal.

When the bias magnetic field application portions 44A and 44B of [5] and [10] were formed, the applied magnetic fields were made antiparallel, so that the antiparallel bias magnetic field was applied to one magnetoresistive sensor 41. The region 43A and the region 43B can be formed. Therefore, it is possible to easily manufacture a magnetic sensor having good linearity in which the influence on the output due to the angle deviation at the time of mounting is reduced and the amount of offset change after applying a magnetic field orthogonal to the sensitivity axis is small.

In the above-described embodiment, a magnetic sensor including a giant magnetoresistive element (GMR element) has been described as a magnetoresistive element, but an anisotropic magnetoresistive element (AMR element) and a tunnel magnetoresistive element (TMR element) have been described. ) Etc. can also be used as a magnetoresistive effect element.

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.

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)
Using a GMR element having the following film configuration as the magnetoresistive effect element 11, the magnetic sensor 10 (see FIGS. 1 to 3) according to the first embodiment was manufactured. 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) / NiFe (70)] / Anti-ferrometric layer: IrMn (80) / Protective layer: Ta (100)

(Comparative Example 1)
As the magnetoresistive element 11, a conventional magnetic sensor 20 (see FIG. 12) was manufactured using a GMR element having the same film configuration as that of the first embodiment.
(Comparative Example 2)
As the magnetoresistive element 11, a conventional magnetic sensor 30 (see FIG. 15) was manufactured using a GMR element having the same film configuration as that of the first embodiment.

FIG. 11 is a graph showing the amount of offset change after applying a magnetic field (orthogonal magnetic field, 30 mT, 300 Oe) in a direction orthogonal to the sensitivity axis to the magnetic sensors of Example 1, Comparative Example 1 and Comparative Example 2. The figure compares the amount of offset change of the magnetic sensor after applying a magnetic field of 30 mT in a direction orthogonal to the sensitivity axis (any one direction).

The magnetic sensor 20 of Comparative Example 1 has the same direction of bias magnetization applied to the magnetoresistive effect element. Therefore, the amount of resistance change after the free magnetic layer is inverted does not differ greatly between the four magnetoresistive effect elements constituting the bridge. Therefore, it can be said that the offset change amount is a relatively small value (3.67 mV). However, the magnetic sensor 20 has a problem that the linearity of the output is lowered due to the influence of the angle deviation at the time of mounting.

In the magnetic sensor 20 of Comparative Example 2, the direction of the bias magnetization applied to the set of magnetoresistive sensor constituting the half bridge is opposite. Therefore, after applying an orthogonal magnetic field, a relatively large difference occurs in the amount of resistance change in the magnetoresistive effect elements having different bias magnetization directions. Therefore, the offset change amount is a relatively large value (12.5 mV).

The first embodiment includes a region having the same area to which a bias magnetic field in the opposite direction is applied in the same magnetoresistive sensor. Therefore, the amount of change in resistance (offset change amount) after applying an orthogonal magnetic field per magnetoresistive sensor is about half that of Comparative Example 1 and Comparative Example 2. Further, since the bias magnetic fields in the opposite directions are applied to all four magnetoresistive effect elements constituting the full bridge, the amount of change in resistance is almost the same. Therefore, it is considered that the offset change amount of the magnetic sensor 10 is the smallest value (2.79 mV).

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.

10, 20, 30, 40: Magnetic sensors 11, 11a, 11b, 11c, 11d: Magnetic resistance effect elements 12, 12a, 12b, 42a, 42b: Half bridge circuit 13A, 13B: Region 15: Input terminal 16: Ground terminal 17: First midpoint potential measurement terminal 18: Second midpoint potential measurement terminal 21, 21a, 21b, 21c, 21d, 31, 31a, 31b, 31c, 31d, 41, 41a, 41b, 41c, 41d: Magnetic resistance effect elements 43, 43A, 43B: Regions 44, 44A, 44B: Bias magnetic field application part 111: Fixed magnetic layer 112: Non-magnetic material layer 113: Free magnetic layer 114: Anti-magnetic layer 115: Magnetic layer 200 : Substrate 201: Magnetic resistance effect element 202: Resist

Claims (8)

Equipped with multiple magnetoresistive elements
Each of the magnetoresistive effect elements has a fixed magnetic layer and a free magnetic layer laminated on the fixed magnetic layer via a non-magnetic material layer.
A half-bridge circuit is formed by the pair of magnetoresistive elements in which the magnetization directions of the fixed magnetic layer are opposite to each other.
Each of the magnetoresistive effect elements forming the half-bridge circuit has a region to which a bias magnetic field in the opposite direction is applied by exchange coupling with an antiferromagnetic layer.
Magnetic sensor. The antiferromagnetic layer is laminated on the free magnetic layer.
The magnetic sensor according to claim 1. The free magnetic layer of the magnetoresistive sensor has the same area of the region to which the bias magnetic field in the opposite direction is applied.
The magnetic sensor according to claim 1 or 2. Each magnetoresistive sensor has a meander shape,
The regions to which the bias magnetic field in the opposite direction is applied are formed adjacent to each other.
The magnetic sensor according to claim 3. The magnetic sensor according to claim 1, wherein the antiferromagnetic layer is provided adjacent to the free magnetic layer. It has a full bridge circuit including a plurality of the half bridge circuits formed by the pair of magnetoresistive elements.
The magnetic sensor according to any one of claims 1 to 5. 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 a measured magnetic field. It has a fixed magnetic layer and a free magnetic layer laminated on the fixed magnetic layer via a non-magnetic material layer.
Each of the free magnetic layers is characterized by having a region to which a bias magnetic field in the opposite direction is applied by exchange coupling with the antiferromagnetic layer.
Magneto resistive sensor.

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