JP5630247B2 - Rotation angle sensor - Google Patents

Description

  The present invention relates to a rotation angle sensor that detects a rotation angle of a detected object based on a change in resistance value of a magnetoresistive effect element in which an intermediate layer is sandwiched between a fixed layer and a free layer.

  Conventionally, for example, as shown in Patent Document 1, a magnetoresistive effect element in which a nonmagnetic layer is sandwiched between two ferromagnetic layers has been proposed. One of the two ferromagnetic layers is a magnetization free layer whose magnetization direction changes with respect to an external magnetic field, and the other is a magnetization fixed layer whose magnetization direction does not change with respect to an external magnetic field. The magnetization free layer has a circular shape, and the magnetization fixed layer has a rectangular shape. The area of the magnetization fixed layer is larger than that of the magnetization free layer.

Japanese Patent Laid-Open No. 11-126933

  By the way, in order to prevent the magnetization direction of the magnetization fixed layer from being changed by the external magnetization, the aspect ratio of the magnetization fixed layer must be increased. However, in the configuration described in Patent Document 1, since the area of the magnetization fixed layer is larger than that of the magnetization free layer, the width and length of the magnetization fixed layer depend on the diameter of the magnetization free layer. It becomes. For this reason, the width of the magnetization fixed layer can only be about the diameter of the magnetization free layer at the shortest, and in order to increase the aspect ratio, the magnetization fixed layer has to be lengthened. As a result, there has been a problem that the size of the magnetization free layer increases and the size of the magnetoresistive element increases.

  In view of the above problems, an object of the present invention is to provide a rotation angle sensor in which an increase in physique is suppressed.

In order to achieve the above object, the invention according to claim 1 is a free layer in which the magnetization direction changes according to the direction of the fixed layer (15) in which the magnetization direction is fixed and the external magnetic field generated by the detection target. A magnetoresistive element (10) having a nonmagnetic intermediate layer (14) sandwiched between the layer (13) and a detected value based on a change in the resistance value of the magnetoresistive element (10) A rotation angle sensor for detecting a rotation angle of a body, wherein an area along a plane orthogonal to the facing direction of the fixed layer (15) and the free layer (13) is larger than that of the fixed layer (15). Is larger, and all of the fixed layer (15) and a part of the free layer (13) face each other through the intermediate layer (14), and the fixed layer (15) is the first fixed layer ( 15a) and a second fixed layer (15b), and the free layer (13) includes a first free layer (13a) and a second free layer (13). ), And the intermediate layer (14) includes a first intermediate layer (14a) and a second intermediate layer (14b), and each of the first fixed layer (15a) and the second fixed layer (15b). The magnetoresistive element (10) includes a first free layer (13a), a first intermediate layer (14a), a first fixed layer (15a), and a magnet. The layer (16), the second fixed layer (15b), the second intermediate layer (14b), and the second free layer (13b) are sequentially stacked in the facing direction, and an area along a plane orthogonal to the facing direction However, the first free layer (13a) is larger than the first fixed layer (15a), and the second free layer (13b) is larger than the second fixed layer (15b). All of the layers (15a) and a part of the first free layer (13a) face each other via the first intermediate layer (14a), and are second fixed. And all (15b), and a part of the second free layer (13b) is faces through the second intermediate layer (14b), the first free layer (13 a) and the second free layer (13b ) Each is characterized by a planar circular shape.

Thus, according to the present invention, all of the fixed layer (15) and a part of the free layer (13) are opposed to each other via the intermediate layer (14). According to this, the aspect ratio of the fixed layer (15) can be determined without depending on the shape of the free layer (13). Therefore, an increase in the size of the fixed layer (15) is suppressed, and an increase in the size of the magnetoresistive effect element (10) is suppressed. As a result, an increase in the size of the rotation angle sensor is suppressed. In the present invention, the area of the free layer (13) is larger than the area of the fixed layer (15). According to this, the external magnetic field can be detected with high sensitivity by the free layer (13) as compared with the configuration in which the area of the fixed layer (15) is larger than the area of the free layer (13). Therefore, the detection accuracy of the rotation angle is improved.

Furthermore, since the present invention has the two free layers (13a, 13b) as described above, the area of the free layer (13) is increased and the external magnetic field is increased compared to the configuration having one free layer. Sensitivity can be detected. Thereby, the detection accuracy of the rotation angle is improved. The free layers (13a, 13b) have a planar circular shape. According to this, the detection range of the external magnetic field is isotropic.

  A magnetic head having the magnetoresistive element (10) according to claim 1 is also conceivable. However, since the magnetization direction of the free layer of the magnetic head is controlled by current, it is not necessary to be highly sensitive to the external magnetic field generated by the detection target. Therefore, when the magnetic head has the magnetoresistive element (10) according to the first aspect, a particularly excellent effect is not achieved. On the other hand, in the present invention, since the magnetoresistive element (10) described above is applied to the rotation angle sensor, the external magnetic field generated by the detection target can be detected with high sensitivity by the free layer (13). , Has an excellent effect.

As described in claim 2, solid fixed layer (15), the free layer (13), an intermediate layer (14), and, there are two respective magnets layer (16), two certain fixed layer (15), intermediate layer (14), the free layer (13), and, by one of the magnet layer (16), a first magnetoresistive element (10a) is formed, two is fixed layer (15), the intermediate layer It is preferable that the second magnetoresistive element (10b) is configured by the other of (14), the free layer (13), and the magnet layer (16).

  Thus, since the 1st magnetoresistive effect element (10a) and the 2nd magnetoresistive effect element (10b) share one free layer (13), each independent free layer is formed. In contrast to the configuration having, the difference in performance due to the manufacturing variation of the free layer is suppressed. Thereby, variation in the resistance values of the two magnetoresistive elements (10a, 10b) is suppressed, and the detection accuracy of the rotation angle is improved.

As described in claim 3 , a half-bridge circuit is configured by the two magnetoresistive elements (10a, 10b). According to this, the rotation angle can be detected by measuring the midpoint potential of the half-bridge circuit. In the case of the configuration described in claim 3 , as described in claim 4 , the magnetization directions of the fixed layers (15) of the two magnetoresistive elements (10a, 10b) constituting the half bridge circuit are reversed. It should be parallel. According to this, as compared with the configuration in which the magnetization directions of the fixed layers (15) of the two magnetoresistive elements (10a, 10b) are parallel, the amount of change in the midpoint potential is increased, and the detection accuracy of the rotation angle is improved. improves.

As described in claim 5 , a full bridge circuit may be constituted by two half bridge circuits. According to this, since the rotation angle can be detected based on the amount of change in the two middle point potentials, the detection accuracy of the rotation angle is improved as compared with the half bridge circuit.

As described in claim 6 , the fixed layer (15) is preferably a planar rectangular shape. According to this, the magnetization direction of the fixed layer (15) is hardly changed by the external magnetic field.

As claimed in claim 7 , the intermediate layer (14) may be insulative. In this case, the magnetoresistive element (10) is a tunnel magnetoresistive element.

It is a figure for demonstrating schematic structure of the rotation angle sensor which concerns on 1st Embodiment, (a) is a top view, (b) shows sectional drawing. It is sectional drawing which shows the manufacturing process of a magnetoresistive effect element, (a) shows a thin film formation process, (b) shows an etching process. It is sectional drawing which shows the manufacturing process of a magnetoresistive effect element, (a) shows an insulating layer formation process, (b) shows a wiring layer formation process. It is a figure for demonstrating the modification of a rotation angle sensor, (a) is a top view, (b) shows sectional drawing. It is a figure for demonstrating schematic structure of the rotation angle sensor which concerns on 2nd Embodiment, (a) is a top view, (b) shows sectional drawing. It is sectional drawing which shows the modification of a rotation angle sensor. It is sectional drawing of the rotation angle sensor which concerns on 3rd Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
1A and 1B are diagrams for explaining a schematic configuration of a rotation angle sensor according to the first embodiment. FIG. 1A is a top view and FIG. 1B is a cross-sectional view. 2A and 2B are cross-sectional views showing a manufacturing process of the magnetoresistive effect element, where FIG. 2A shows a thin film forming process and FIG. 2B shows an etching process. 3A and 3B are cross-sectional views showing the manufacturing process of the magnetoresistive effect element, where FIG. 3A shows an insulating layer forming process and FIG. 3B shows a wiring layer forming process. In FIG. 1A, layers 14, 16, and 18 to be described later are omitted in order to clarify the electrical connection between the two magnetoresistive elements 10a and 10b. Hereinafter, the direction in which the layers 13 to 16 are laminated is referred to as a lamination direction, and a plane orthogonal to the lamination direction is referred to as an orthogonal plane. The stacking direction corresponds to the facing direction described in the claims.

  The rotation angle sensor 100 has a plurality of magnetoresistive elements 10. As shown in FIG. 1, the rotation angle sensor 100 has two magnetoresistive elements 10a and 10b, and the two magnetoresistive elements 10a and 10b constitute a half bridge circuit. The rotation angle sensor 100 is disposed in an external magnetic field generated by a detected object (not shown), and detects a midpoint potential of the half-bridge circuit by detecting a change in the external magnetic field due to the rotational motion of the detected object. The rotation angle of the detection object is detected.

  The magnetoresistive effect element 10 is composed of a plurality of thin film layers laminated on a semiconductor substrate 11 with an oxide film 12 interposed therebetween. As shown in FIG. 1, a free layer 13, an intermediate layer 14, a fixed layer 15, a magnet layer 16, and a wiring layer 17 are sequentially stacked on an oxide film 12, and the magnetoresistive effect element 10 includes layers 13 to 13. It consists of 16. The free layer 13 has a planar circular shape, and the layers 14 to 16 have the same shape, each having a planar rectangular shape. The free layer 13 has a larger area along the orthogonal plane than the layers 14 to 16, and all of the fixed layer 15 faces part of the free layer 13 through the intermediate layer 14. In the free layer 13, an insulating layer 18 is formed outside the laminated region of the intermediate layer 14 and between the two magnetoresistive elements 10 a and 10 b, and a part of the free layer 13 and the layers 14 to 16 are formed. Are covered with an insulating film 18. The wiring layer 17 has upper surfaces of the magnet layer 16 and the insulating film 18 so as to electrically connect the magnet layer 16 of the first magnetoresistive effect element 10a and the magnet layer 16 of the second magnetoresistive effect element 10b. Is formed.

  The free layer 13 and the fixed layer 15 are ferromagnetic materials. The magnetization direction of the free layer 13 is not fixed, and has a property that the magnetization direction is changed by an external magnetic field. The magnetization direction of the fixed layer 15 is fixed by the magnet layer 16 and has a property that the magnetization direction does not vary due to an external magnetic field. The intermediate layer 14 has non-magnetic properties and also has an insulating property. When a voltage is applied between the free layer 13 and the fixed layer 15, the intermediate layer 14 forms a gap between the free layer 13 and the fixed layer 15 by the tunnel effect. A current (tunnel current) flows between them. Thus, the magnetoresistive effect element 10 according to the present embodiment is a tunnel magnetoresistive effect element (TMR).

  The ease of flow of the tunnel current depends on the magnetization directions of the free layer 13 and the fixed layer 15, and flows most easily when the magnetization directions of the free layer 13 and the fixed layer 15 are parallel, and most when the magnetization directions are antiparallel. It is difficult to flow. That is, the resistance value of the magnetoresistive effect element 10 changes smallest when parallel, and the resistance value changes largest when antiparallel. In this embodiment, the magnetization direction of the fixed layer 15 of the first magnetoresistive effect element 10a and the magnetization direction of the fixed layer 15 of the second magnetoresistive effect element 10b are antiparallel, and the magnetoresistive effect element The changes in resistance values 10a and 10b are opposite. That is, when one resistance value of the two magnetoresistive effect elements 10a and 10b decreases, the other resistance value increases, and when one resistance value increases, the other resistance value increases.

  As shown in FIG. 1, a power supply voltage is connected to the free layer 13 of the first magnetoresistance effect element 10a, and a ground is connected to the free layer 13 of the second magnetoresistance effect element 10b. As a result, as indicated by a broken line arrow, a current flows from the first magnetoresistive effect element 10a toward the second magnetoresistive effect element 10b via the wiring layer 17. The midpoint potential of the half bridge circuit is the potential of the wiring layer 17 located between the two magnetoresistive elements 10a and 10b.

  Next, a method for manufacturing the magnetoresistive effect element 10 according to the present embodiment will be described with reference to FIGS. First, the oxide film 12 is formed on the surface of the semiconductor substrate 11 by thermally oxidizing the surface of the semiconductor substrate 11. Thereafter, the semiconductor substrate 11 on which the oxide film 12 is formed is placed in a vacuum chamber, and as shown in FIG. 2A, the free layer 13, the intermediate layer 14, the fixed layer 15, and the magnet layer 16 are formed by sputtering. It forms sequentially on the oxide film 12. The above is a thin film formation process.

  After the thin film forming step, as shown in FIG. 2B, the shape of the free layer 13 is made circular by ion milling so that the planar shape of the layers 14 to 16 is rectangular. Is processed. Thereby, the area of the surface along the orthogonal plane is larger in the free layer 13 than in the layers 14 to 16, and all of the fixed layer 15 faces the part of the free layer 13 through the intermediate layer 14. It becomes composition. The above is the etching process.

  After the etching step, as shown in FIG. 3A, the insulating layer 18 is formed so that the side surfaces of the layers 14 to 16 are covered with the insulating layer 18. The above is the insulating layer forming step.

  After the insulating layer formation step, the wiring layer 17 is formed as shown in FIG. At this time, as shown in FIG. 1B, the wiring layer 17 is connected to the magnet layer 16 and the insulating film 18 so as to electrically connect the magnet layers 16 of the two magnetoresistive elements 10a and 10b. Form on the top surface. The above is the wiring layer forming step.

  Although not shown in the figure after each of the above steps, the magnetoresistive effect element 10 is formed by forming a protective film.

  Next, functions and effects of the rotation angle sensor 100 according to the present embodiment will be described. As described above, all of the fixed layer 15 and a part of the free layer 13 are opposed to each other through the intermediate layer 14. According to this, the aspect ratio of the fixed layer 15 can be determined without depending on the shape of the free layer 13. Therefore, an increase in the size of the fixed layer 15 is suppressed, and an increase in the size of the magnetoresistive effect element 10 is suppressed. As a result, an increase in the physique of the rotation angle sensor 100 is suppressed.

  Further, the area of the free layer 13 is larger than the area of the fixed layer 15. According to this, the external magnetic field can be detected with high sensitivity by the free layer 13 as compared with the configuration in which the area of the fixed layer 15 is larger than the area of the free layer 13. Therefore, the detection accuracy of the rotation angle is improved.

  A magnetic head having the magnetoresistive effect element 10 described in this embodiment is also conceivable. However, since the magnetization direction of the free layer of the magnetic head is controlled by current, it is not necessary to be highly sensitive to the external magnetic field generated by the detection target. Therefore, when the magnetic head has the magnetoresistive effect element 10, a particularly excellent effect is not achieved. On the other hand, in this embodiment, since the magnetoresistive effect element 10 described above is applied to the rotation angle sensor 100, an external magnetic field generated by the detection target can be detected with high sensitivity by the free layer 13. Has an effect.

  In the present embodiment, the magnetization direction of the fixed layer 15 of the first magnetoresistance effect element 10a and the magnetization direction of the fixed layer 15 of the second magnetoresistance effect element 10b are antiparallel. According to this, as compared with the configuration in which the magnetization directions of the fixed layers 15 of the two magnetoresistive elements 10a and 10b are parallel, the amount of change in the midpoint potential is increased, and the detection accuracy of the rotation angle is improved.

  In the present embodiment, an example in which the free layer 13, the intermediate layer 14, the fixed layer 15, the magnet layer 16, and the wiring layer 17 are sequentially stacked on the oxide film 12 is shown. However, the stacking directions of the layers 13 to 17 may be reversed as shown in FIG. That is, the wiring layer 17, the magnet layer 16, the fixed layer 15, the intermediate layer 14, and the free layer 13 may be sequentially stacked on the oxide film 12. 4A and 4B are diagrams for explaining a modification of the rotation angle sensor, in which FIG. 4A is a top view and FIG. 4B is a cross-sectional view.

(Second Embodiment)
Next, a second embodiment of the present invention will be described based on FIG. 5A and 5B are diagrams for explaining a schematic configuration of the rotation angle sensor according to the second embodiment. FIG. 5A is a top view, and FIG. 5B is a cross-sectional view. It corresponds to.

  Since the rotation angle sensor 100 according to the second embodiment is often in common with that according to the first embodiment, the detailed description of the common parts will be omitted below, and different parts will be described mainly. In addition, the same code | symbol shall be provided to the element same as the element shown in 1st Embodiment.

  In the first embodiment, as shown in FIG. 1, the example in which the magnetoresistive effect elements 10 a and 10 b have the free layer 13 independently is shown. On the other hand, the present embodiment is characterized in that the magnetoresistive effect elements 10 a and 10 b share one free layer 13. As shown in FIG. 5, the first magnetic layer is formed by one of the two fixed layers 15 and the intermediate layer 14, the free layer 13, and the magnet layer 16 positioned in the projection region in the stacking direction of the fixed layer 15. The resistance effect element 10a is configured, and the second of the two fixed layers 15 and the intermediate layer 14, the free layer 13, and the magnet layer 16 positioned in the projection region in the stacking direction of the fixed layer 15 are second. The magnetoresistive effect element 10b is configured. According to this, it is suppressed that the difference in the performance by the manufacturing variation of the free layer 13 arises in each of the magnetoresistive effect elements 10a and 10b. Thereby, variation in the resistance values of the two magnetoresistive elements 10a and 10b is suppressed, and the detection accuracy of the rotation angle is improved.

  As shown in FIG. 5, since the two magnetoresistive elements 10a and 10b are electrically connected to each other via the shared free layer 13, the wiring layer 17 is omitted. Therefore, the wiring layer forming step is omitted, and the number of manufacturing steps of the magnetoresistive effect element 10 is reduced. In this case, the power supply voltage is connected to the magnet layer 16 of the first magnetoresistance effect element 10a, and the ground is connected to the magnet layer 16 of the second magnetoresistance effect element 10b.

  In the present embodiment, an example in which the magnetoresistive effect elements 10a and 10b share one free layer 13 has been described. However, when the intermediate layer 14 has an insulating property, as shown in FIG. 6, the magnetoresistive effect elements 10 a and 10 b may share not only the free layer 13 but also the intermediate layer 14. According to this, in the magnetoresistive effect elements 10a and 10b, it is possible to suppress the difference in performance due to the manufacturing variation of the intermediate layer 14 as well as the manufacturing variation of the free layer 13. Therefore, variation in resistance values of the two magnetoresistive effect elements 10a and 10b is suppressed, and detection accuracy of the rotation angle is improved. FIG. 6 is a cross-sectional view showing a modification of the rotation angle sensor.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 7 is a cross-sectional view of a rotation angle sensor according to the third embodiment.

  Since the rotation angle sensor according to the third embodiment is in common with those according to the above-described embodiments, the detailed description of the common parts will be omitted below, and different parts will be described mainly. In addition, the same code | symbol shall be provided to the element same as the element shown to each above-mentioned embodiment.

  In each embodiment, the free layer 13, the intermediate | middle layer 14, and the fixed layer 15 each showed the example which is one layer. On the other hand, this embodiment is characterized in that each of the free layer 13, the intermediate layer 14, and the fixed layer 15 has two layers.

  The free layer 13 has a first free layer 13a and a second free layer 13b, the intermediate layer 14 has a first intermediate layer 14a and a second intermediate layer 14b, and the fixed layer 15 has a first fixed layer. It has the layer 15a and the 2nd fixed layer 15b. As shown in FIG. 7, a first free layer 13 a, a first intermediate layer 14 a, and a first fixed layer 15 a are sequentially stacked on the oxide film 12, and the second layer is interposed above the second via a magnet layer 16. The fixed layer 15b, the second intermediate layer 14b, and the second free layer 13b are sequentially stacked. The area along the orthogonal plane is larger in the first free layer 13a than in the first fixed layer 15a, and larger in the second free layer 13b than in the second fixed layer 15b. Further, all of the first fixed layer 15a faces part of the first free layer 13a through the first intermediate layer 14a, and all of the second fixed layer 15b is second through the second intermediate layer 14b. It faces a part of the free layer 13b.

  According to this, since the area of the free layer 13 is larger than in the configuration in which the free layer 13 is a single layer, the external magnetic field can be detected with high sensitivity. Thereby, the detection accuracy of the rotation angle is improved.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  In each embodiment, the intermediate layer 14 has an insulating property, and the magnetoresistive element 10 is a tunnel magnetoresistive element (TMR). However, the intermediate layer 14 may have conductivity. In this case, the magnetoresistive element 10 is a giant magnetoresistive element (GMR). However, when the magnetoresistive effect element 10 is GMR, structures other than FIG. 6 are established.

  In each embodiment, an example in which a half bridge circuit is configured by two magnetoresistive elements 10a and 10b has been described. However, a full bridge circuit may be configured by connecting two half bridge circuits. According to this, since the rotation angle can be detected based on the amount of change in the two middle point potentials, the detection accuracy of the rotation angle is improved as compared with the half bridge circuit.

DESCRIPTION OF SYMBOLS 10 ... Magnetoresistive effect element 13 ... Free layer 14 ... Intermediate layer 15 ... Fixed layer 16 ... Magnet layer 17 ... Wiring layer 18 ... Insulating layer 100 ... Rotation angle Sensor

Claims (7)

A nonmagnetic intermediate layer (14) is provided between the fixed layer (15) whose magnetization direction is fixed and the free layer (13) whose magnetization direction changes according to the direction of the external magnetic field generated by the detection target. A rotation angle sensor having a sandwiched magnetoresistive effect element (10) and detecting a rotation angle of the detected object based on a change in resistance value of the magnetoresistive effect element (10),
The area along the plane orthogonal to the facing direction of the fixed layer (15) and the free layer (13) is larger in the free layer (13) than in the fixed layer (15),
All of the fixed layer (15) and a part of the free layer (13) are opposed via the intermediate layer (14),
The fixed layer (15) includes a first fixed layer (15a) and a second fixed layer (15b),
The free layer (13) has a first free layer (13a) and a second free layer (13b),
The intermediate layer (14) includes a first intermediate layer (14a) and a second intermediate layer (14b),
The first fixed layer (15a) and the second fixed layer (15b) have a magnet layer (16) for fixing the magnetization direction of each;
The magnetoresistive effect element (10) includes the first free layer (13a), the first intermediate layer (14a), the first fixed layer (15a), the magnet layer (16), the second fixed layer ( 15b), the second intermediate layer (14b), and the second free layer (13b) are sequentially stacked in the facing direction,
The first free layer (13a) is larger in area along the plane perpendicular to the facing direction than the first fixed layer (15a), and the second free layer is larger than the second fixed layer (15b). (13b) is larger,
All of the first fixed layer (15a) and a part of the first free layer (13a) face each other via the first intermediate layer (14a), and all of the second fixed layer (15b). And a part of the second free layer (13b) are opposed to each other through the second intermediate layer (14b),
The rotation angle sensor, wherein each of the first free layer (13a) and the second free layer (13b) has a planar circular shape. Before Symbol fixed layer (15), the free layer (13), said intermediate layer (14), and said magnet layer (16) has two respectively,
Two is the fixed layer (15), said intermediate layer (14), the free layer (13), and, by one of the magnet layer (16), a first magnetoresistive element (10a) is configured And
Two is the fixed layer (15), said intermediate layer (14), the free layer (13), and, by the other of said magnet layer (16), second magnetoresistive element (10b) is configured The rotation angle sensor according to claim 1, wherein the rotation angle sensor is provided. Rotation angle sensor as claimed by two of said magnetoresistive effect element (10a, 10b), the 請 Motomeko 2 you, characterized in that the half-bridge circuit is formed.   The rotation angle sensor according to claim 3, wherein the magnetization directions of the fixed layers 15 of the two magnetoresistive elements (10a, 10b) constituting the half bridge circuit are antiparallel.   The rotation angle sensor according to claim 3 or 4, wherein a full bridge circuit is constituted by the two half bridge circuits.   The rotation angle sensor according to any one of claims 1 to 5, wherein the fixed layer (15) has a planar rectangular shape.   The rotation angle sensor according to any one of claims 1 to 6, wherein the intermediate layer (14) is insulative.

Images