JP2016031299A - Magnetic sensor, magnetic detection device, and manufacturing method of magnetic sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a smaller magnetic sensor which has a simple configuration and is capable of stably and accurately measuring an external magnetic field being a measurement object.SOLUTION: The magnetic sensor includes a conductive layer which is formed in a loop shape and has a first pinned layer whose magnetization is fixed in a first direction, and a tunnel junction layer which is formed spaced apart from the first pinned layer; a first tunnel layer formed on the first pinned layer; and a first free layer which is formed on the first tunnel layer and whose direction of magnetization changes according to a magnetic field generated by a coil current caused by a change of an external magnetic field.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a magnetic sensor capable of detecting magnetism with high sensitivity by measuring a change in current flowing through a conductor, and a method of manufacturing the magnetic sensor.

A current sensor used in a conventional magnetic sensor supplies a control current to a U-shaped curved conductor and detects a change in a current magnetic field generated around the curved conductor by a Hall element (see, for example, Patent Document 1). ). In addition, a current sensor used for a conventional magnetic sensor detects a current using a giant magnetoresistive element (hereinafter referred to as a GMR element) that exhibits a giant magnetoresistive effect instead of a hall element. (For example, refer to Patent Document 2).
[Patent Document 1] Japanese Patent Publication No. 7-123090 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-101252 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-6127

  However, a current sensor used in a conventional magnetic sensor using a Hall element or a GMR element cannot measure a minute and precise magnetic field fluctuation. The Hall element and the GMR element cannot be reduced in size sufficiently due to their structures.

  The first aspect of the present invention includes a first pinned layer whose magnetization is fixed in the first direction, and a tunnel junction layer formed apart from the first pinned layer, and in a loop shape Formed on the formed conductive layer, the first tunnel layer formed on the first pinned layer, and the first tunnel layer, the direction of magnetization is generated by the coil current generated by the fluctuation of the external magnetic field A magnetic sensor comprising a first free layer that changes with a magnetic field is provided.

  In the second aspect of the present invention, a step of forming a loop pinned layer on the substrate, a step of forming a tunnel layer on the pinned layer, a step of forming a free layer on the tunnel layer, and a free layer And the first and second tunnel layers spaced apart from each other, a first free layer on the first tunnel layer, and a second free layer on the second tunnel layer Forming a first upper wiring layer on the first free layer, forming a second upper wiring layer on the second free layer, and a first layer on the pinned layer. Forming a second external connection terminal and a second external connection terminal, forming a third external connection terminal on the first upper wiring layer, and forming a fourth external connection terminal on the second upper wiring layer The manufacturing method of the magnetic sensor provided with the process to perform is provided.

  It should be noted that the above summary of the invention does not enumerate all the necessary features of the present invention. In addition, a sub-combination of these feature groups can also be an invention.

An example of the structure of the magnetoresistive effect element 1 is shown. An example of the state of the magnetoresistive effect element 1 is shown. An example of the state of the magnetoresistive effect element 1 is shown. The relationship between the resistance value parallel to the film surface of the magnetoresistive element 1 and the current-induced magnetic field is shown. 1 shows a magnetic sensor 100 according to a first embodiment. FIG. 2 shows a cross-sectional view of the magnetic sensor 100 according to the first embodiment. 1 shows a B cross-sectional view of a magnetic sensor 100 according to Embodiment 1. FIG. FIG. 3 shows a C cross-sectional view of the magnetic sensor 100 according to the first embodiment. FIG. 2 shows a cross-sectional view of the magnetic sensor 100 according to the first embodiment. 1 shows a B cross-sectional view of a magnetic sensor 100 according to Embodiment 1. FIG. FIG. 3 shows a C cross-sectional view of the magnetic sensor 100 according to the first embodiment. 1 is a conceptual circuit diagram of a magnetic sensor 100 according to Embodiment 1. FIG. It is a schematic diagram which shows the magnetic field concerning the free layer 40 when the coil current Ic flows. The magnetic sensor 100 which concerns on Embodiment 2 is shown. FIG. 6 shows a cross-sectional view of the magnetic sensor 100 according to the second embodiment. FIG. 4 is a B cross-sectional view of the magnetic sensor 100 according to the second embodiment. FIG. 4 is a C cross-sectional view of the magnetic sensor 100 according to the second embodiment. 5 shows a magnetic sensor 100 according to a third embodiment. FIG. 6 is a cross-sectional view of the magnetic sensor 100 according to the third embodiment. FIG. 6 shows a B cross-sectional view of a magnetic sensor 100 according to a third embodiment. FIG. 6 shows a C cross-sectional view of a magnetic sensor 100 according to a third embodiment. FIG. 6 shows a D cross-sectional view of a magnetic sensor 100 according to a third embodiment. The circuit conceptual diagram of the magnetic sensor 100 which concerns on Embodiment 3 is shown. The substrate 90 on which the pinned layer 20 is formed is shown. The process of fixing the magnetization of the pinned layer 20 is shown. The process of forming the tunnel layer 30 on the pinned layer 20 is shown. The element separation process of the magnetic sensor 100 is shown. The process of patterning a TMR element is shown. A step of depositing the second insulating film 92 is shown. The magnetic sensor 100 in which the upper wiring layer 60 is formed is shown. An example of the magnetic detection apparatus 200 is shown. An example of the output of the amplifier circuit 95 is shown. An example of the output of the amplitude detection circuit 96 is shown. An example of the output of the frequency detection circuit 97 is shown. An example of the output of the frequency counter 99 is shown.

  Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

  FIG. 1 shows an example of the configuration of the magnetoresistive effect element 1. The magnetoresistive effect element 1 includes a pinned layer 20, a tunnel layer 30 and a free layer 40. The resistance value of the magnetoresistive effect element 1 changes depending on the relative magnetization angle between the pinned layer 20 and the free layer 40. The change in resistance value indicates a change in at least one of a resistance value in the horizontal direction on the film surface of the magnetoresistive effect element 1 and a resistance value in the direction perpendicular to the film surface. The magnetoresistive effect element 1 of this example has a rectangular shape of 1 μm in the X-axis direction and 10 μm in the Y-axis direction. Arrows indicate the direction of magnetization.

  The pinned layer 20 is made of a magnetic material whose magnetization is fixed in a predetermined direction. The pinned layer 20 is formed by a combination of materials such as Co, Fe, and Ni. For example, the magnetization of the pinned layer 20 is fixed in the x-axis direction by forming a magnetoresistive film and then performing heat treatment (annealing) in a magnetic field. A magnetoresistive film refers to a film whose electrical resistance is changed by an external magnetic field or the like.

The tunnel layer 30 is a thin film insulator. The tunnel layer 30 is formed on the pinned layer 20. For example, when the magnetoresistive element 1 is a tunnel magnetoresistive (TMR) element, the tunnel layer 30 is formed of Al ₂ O ₃ , MgO, or the like. A TMR element refers to an element in which an extremely thin insulating film is sandwiched between magnetic thin films. In the TMR element, the resistance of the insulating film changes depending on the magnetization directions of the magnetic thin films at both ends of the insulating film.

  The free layer 40 is a magnetic material whose magnetization direction changes according to an external magnetic field. For example, the free layer 40 is a soft magnetic material formed by a combination of materials such as Co, Fe, and Ni. The free layer 40 is formed on the tunnel layer 30.

  FIG. 2 shows an example of the state of the magnetoresistive effect element 1. The magnetoresistive effect element 1 of this example shows a state in which the easy axis of the free layer 40 is induced in a direction orthogonal to the magnetization direction of the pinned layer 20. The easy magnetization axis refers to a crystal orientation that is easily magnetized in a magnetic material having crystalline magnetic anisotropy.

  FIG. 3 shows an example of the state of the magnetoresistive effect element 1. The magnetoresistive effect element 1 of this example shows a state in which the magnetization of the free layer 40 is induced in the y-axis direction. That is, the magnetization direction of the free layer 40 is orthogonal to the magnetization direction of the pinned layer 20. The magnetization direction of the free layer 40 changes depending on the magnetic field generated by the current flowing through the pinned layer 20.

  FIG. 4 shows the relationship between the resistance value in the direction parallel to the film surface of the magnetoresistive effect element 1 and the current-induced magnetic field. The vertical axis represents the resistance value of the magnetoresistive effect element 1, and the horizontal axis represents the strength of the current-induced magnetic field. The current-induced magnetic field refers to a magnetic field generated due to the current flowing through the pinned layer 20. The direction of the current-induced magnetic field indicates that the fixed magnetization direction of the pinned layer 20 is positive.

  In the state without the current-induced magnetic field, the magnetizations of the pinned layer 20 and the free layer 40 are orthogonal. When a weak current-induced magnetic field is applied in the positive direction, the magnetization of the free layer 40 moves in a direction that is aligned with the magnetization direction of the pinned layer 20. When the magnetization directions are aligned, the influence of the magnetization on the electrons is smaller than when the magnetizations are arranged irregularly, and the resistance value of the magnetoresistive effect element 1 is reduced. When the magnitude of the current-induced magnetic field exceeds a certain level, the magnetization of the free layer 40 is aligned with the magnetization direction of the pinned layer 20. When the magnetization directions are aligned, the resistance value of the magnetoresistive element 1 is saturated.

  When a weak current-induced magnetic field is applied in the negative direction, the magnetization of the free layer 40 moves in the direction opposite to the magnetization direction of the pinned layer 20 and the resistance value of the magnetoresistive element 1 increases. When the magnitude of the current-induced magnetic field exceeds a certain level, the magnetization of the free layer 40 is directed in the direction opposite to the magnetization direction of the pinned layer 20. When the magnetization direction is in the opposite direction, the resistance value of the magnetoresistive effect element 1 is saturated. However, when a stronger current-induced magnetic field is applied, the magnetization of the pinned layer 20 that has been fixed begins to turn negative. That is, since the magnetization directions are aligned, the resistance value of the magnetoresistive element 1 is reduced.

  As described above, by taking the magnetization direction of the pinned layer 20 as the sensitivity axis, the resistance value of the magnetoresistive effect element 1 changes linearly. However, in order to change the resistance value linearly, the absolute value of the current-induced magnetic field needs to be smaller than a predetermined value.

<Embodiment 1>
The magnetic sensor 100 of Embodiment 1 is demonstrated using FIGS. 5-9. FIG. 5 is a layout view of the magnetic sensor 100 as viewed from above. 6A to 6C and FIGS. 7A to 7C are cross-sectional views of the magnetic sensor 100 taken along dotted lines AA ′, dotted lines BB ′, and dotted lines CC ′.

  The magnetic sensor 100 includes a conductive layer 27, a first tunnel layer 31, a first free layer 41, a tunnel junction 35, and a resistance detection circuit 85. The conductive layer 27 includes a first pinned layer 21, an intermediate layer 25, and a wiring layer 26. All the conductive layers 27 in this example are formed of the pinned layer 20. Since the conductive layer 27 is formed in a loop shape, the coil current Ic flows according to the fluctuation of the external magnetic field. The magnetic sensor 100 detects the magnetic field by detecting the coil current Ic flowing through the conductive layer 27. The loop shape may be a closed loop shape, and may be any shape such as a round shape, a square shape, a polygonal shape, a rounded polygonal shape, a concave shape, and a convex shape. The loop shape is not limited to the case where the number of turns is 1, but may be a case where a plurality of turns are provided. The shape of the conductive layer 27 is not limited to the shape of this example, and may be changed as appropriate according to the layout. The magnetic sensor 100 can detect the fluctuation of the external magnetic field input in the vertical direction with respect to the conductive layer 27 formed in a loop shape.

  6A is a cross-sectional view of the magnetic sensor 100 taken along a dotted line AA ′ shown in FIG. The section A corresponds to the section of the first pinned layer 21, the tunnel junction 35, the intermediate layer 25, the wiring layer 26, the first tunnel layer 31, and the first free layer 41. The first tunnel layer 31, the first free layer 41, the first cover layer 51, and the first upper wiring layer 61 are disposed apart from the tunnel junction 35 and the second upper wiring layer 62. . Separation means having a space between each layer. Further, a nonmagnetic material layer such as an insulating film may be provided instead of the space. Note that the first pinned layer 21, the intermediate layer 25, and the wiring layer 26 may be integrally formed as the conductive layer 27 when formed of the same material.

  The tunnel junction 35 is formed on the wiring layer 26. The tunnel junction 35 is electrically connected to the first pinned layer 21. Further, the tunnel junction 35 prevents the coil current Ic from flowing to the second upper wiring layer 62 side.

  FIG. 6B shows a cross-sectional view of the magnetic sensor 100 taken along the dotted line BB ′ shown in FIG. The B cross section corresponds to the cross section of the first upper wiring layer 61 and the wiring layer 26. The first upper wiring layer 61 is formed apart from the wiring layer 26.

  FIG. 6C shows a cross-sectional view of the magnetic sensor 100 along the dotted line CC ′ shown in FIG. 5. The section C corresponds to a sectional view of the first pinned layer 21, the first tunnel layer 31, the first free layer 41, the first cover layer 51, and the first upper wiring layer 61. The first pinned layer 21, the first tunnel layer 31, the first free layer 41, the first cover layer 51, and the first upper wiring layer 61 are stacked in this order. The width of the first pinned layer 21 may be larger than the width of each of the first tunnel layer 31, the first free layer 41, and the first cover layer 51. The width of the first pinned layer 21 refers to the thickness of the first pinned layer 21 in a direction perpendicular to the direction in which the coil current Ic flows.

  FIG. 7A shows a cross-sectional view of the magnetic sensor 100 along the dotted line AA ′ shown in FIG. 5. FIG. 7A shows an example of the tunnel junction 35. The tunnel junction portion 35 of this example includes a second pinned layer 22, a second tunnel layer 32, a second free layer 42, and a second cover layer 52. The second pinned layer 22 is provided in series with the first pinned layer 21 and the coil current Ic flows. FIG. 7B shows a cross-sectional view of the magnetic sensor 100 taken along the dotted line BB ′ shown in FIG. 5. FIG. 7C shows a cross-sectional view of the magnetic sensor 100 taken along the dotted line CC ′ shown in FIG. 7B and 7C are the same as FIGS. 6B and 6C, respectively. Next, the magnetic sensor 100 shown in FIG. 5 will be described with reference to the cross-sectional views of FIGS.

  In the first pinned layer 21, the magnetization is fixed in a predetermined direction. When the first pinned layer 21 is formed of the same material as the wiring layer 26, the first pinned layer 21 may be formed integrally with the wiring layer 26. In this case, the first pinned layer 21 is different from the wiring layer 26 in that the first tunnel layer 31 is formed on the upper portion.

  The intermediate layer 25 connects the first pinned layer 21 and the second pinned layer 22, and the coil current Ic flows. The intermediate layer 25 of this example is formed of the same material as the pinned layer 20. The intermediate layer 25 is not limited to the same material as the pinned layer 20 as long as it is a material that can connect the first pinned layer 21 and the second pinned layer 22.

  The second pinned layer 22 has magnetization fixed in a predetermined direction. The magnetization of the second pinned layer 22 of this example is fixed in the same direction as the first pinned layer 21. When the second pinned layer 22 is formed of the same material as the wiring layer 26, it may be formed integrally with the wiring layer 26. In this case, the second pinned layer 22 differs from the wiring layer 26 in that the second tunnel layer 32 is formed on the upper portion. The first pinned layer 21, the second pinned layer 22, the intermediate layer 25, and the wiring layer 26 may be integrally formed as the conductive layer 27.

  The first tunnel layer 31 is formed on the first pinned layer 21. The first tunnel layer 31 prevents the coil current Ic flowing in the first pinned layer 21 from flowing to the first upper wiring layer 61 side. The first tunnel layer 31 of this example has the same cross-sectional shape of the film surface as the first pinned layer 21. The first tunnel layer 31 may differ from the first pinned layer 21 in the cross-sectional shape of the film surface.

  The first free layer 41 is formed on the first tunnel layer 31. The direction of magnetization of the first free layer 41 changes due to the fluctuation of the external magnetic field generated by the coil current Ic flowing through the first pinned layer 21. The first free layer 41 of this example has the same cross-sectional shape as the first tunnel layer 31 and the film surface.

  The first cover layer 51 protects the upper part of the first free layer 41. The first cover layer 51 is continuously formed on the first free layer 41. The first cover layer 51 is preferably formed of a material having a small resistance value.

  The second tunnel layer 32 is formed on the second pinned layer 22. The second tunnel layer 32 prevents the coil current Ic flowing in the second pinned layer 22 from flowing to the second upper wiring layer 62 side. The second tunnel layer 32 of this example has the same cross-sectional shape of the film surface as the second pinned layer 22. The second tunnel layer 32 may have a cross-sectional shape different from that of the second pinned layer 22.

  The second free layer 42 is formed on the second tunnel layer 32. The direction of magnetization of the second free layer 42 changes due to the fluctuation of the external magnetic field generated by the coil current Ic flowing through the second pinned layer 22. The second free layer 42 in this example has the same cross-sectional shape as the second tunnel layer 32 and the film surface.

  The second cover layer 52 protects the upper part of the second free layer 42. The second cover layer 52 is continuously formed on the second free layer 42. The second cover layer 52 is preferably formed of a material having a small resistance value.

  The first upper wiring layer 61 includes a first external connection terminal 71 connected to the resistance detection circuit 85. The first upper wiring layer 61 is formed apart from the first pinned layer 21.

  The second upper wiring layer 62 includes a second external connection terminal 72 connected to the resistance detection circuit 85. The second upper wiring layer 62 is formed apart from the second pinned layer 22.

  The resistance detection circuit 85 includes a voltmeter VM1, an ammeter IM, and a first constant current source IS1. The resistance detection circuit 85 is connected to the first external connection terminal 71 and the second external connection terminal 72. The first constant current source IS1 supplies a constant current for measurement. The resistance detection circuit 85 detects the resistance value using the voltmeter VM1 and the ammeter IM.

  FIG. 8 is a conceptual circuit diagram of the magnetic sensor 100 according to the first embodiment. The circuit diagram of the magnetic sensor 100 is simply expressed using the first sensor resistance (TMR1), the second sensor resistance (TMR2), and the intermediate layer resistance (RPC). TMR1 indicates a first sensor resistance between layers from the first pinned layer 21 to the first free layer 41. TMR2 indicates a second sensor resistance between the layers from the second pinned layer 22 to the second free layer. RPC indicates the resistance of the intermediate layer 25. TMR1 and TMR2 are connected across the RPC.

  The resistance detection circuit 85 detects the coil current Ic by detecting the resistance value between the first free layer 41 and the second free layer 42. The resistance value between the first free layer 41 and the second free layer 42 indicates the sum of the resistance values of TMR1, RPC, and TMR2. The resistance detection circuit 85 inputs the current Im to the first external connection terminal 71 as a measurement current. Current for measurement flows through TMR1, RPC and TMR2 connected in series. The measurement current returns from the second external connection terminal 72 to the resistance detection circuit 85.

  In this example, TMR1 and TMR2 are each about several kΩ, and RPC is several Ω. Therefore, compared to the voltage drop in TMR1 and TMR2, the voltage drop in the RPC of the intermediate layer 25 can be ignored. Therefore, the magnetic sensor 100 can detect the external magnetic field by measuring the current value of the coil current Ic using the circuit conceptual diagram shown in FIG. In addition, since the coil current Ic does not flow through TMR1 and TMR2, the external magnetic field can be accurately detected. When the coil current Ic flows through the conductive layer 27, a current-induced magnetic field (AC magnetic field) is generated according to the right-handed screw law.

The resistance value detected by the resistance detection circuit 85 is obtained by the following equation.
TMR1 + TMR2 = VM1 / IM
However,
RPC << TMR1 + TMR2
Iin * RPC << VM
Here, VM1 is a voltage value measured by the voltmeter VM1, and IM is a current value measured by the ammeter IM. VM is a voltage value between the first external connection terminal 71 and the second external connection terminal 72. In this example, VM = VM1.

  FIG. 9 is a schematic diagram showing a current-induced magnetic field Bc applied to the free layer 40 when the coil current Ic flows. FIG. 9 shows a cross section C of FIG. 7C. A dotted line indicates a current-induced magnetic field Bc generated by the coil current Ic flowing through the first pinned layer 21.

When the coil current Ic flows through the first pinned layer 21, a current-induced magnetic field Bc is generated around the first pinned layer 21 according to the right-handed screw law. It is considered that a line current having a magnitude I flows through the center point of the first pinned layer 21. The magnitude of the current-induced magnetic field Bc generated at the position of the radius r centering on the line current flowing in the first pinned layer 21 is expressed by the following formula (1).
Bc = (4π * μ ₀ * I) / (2 * r) (1)
Here, μ ₀ represents a vacuum magnetic permeability.

The first pinned layer 21, the first tunnel layer 31, the first free layer 41, and the first cover layer 51 of this example each have a thickness of about several tens of angstroms. For example, the magnitude of the coil current Ic is 1 μA, and the average distance from the first pinned layer 21 to the first free layer 41 is 50 angstroms (5 nm). In this case, when the equation (1) is used, the magnitude of the magnetic field Bc generated at that point is as follows.
Bc = (4 * 3.14 * 10 ⁻⁷ * 1 μA) / (2 * 5 nm)
= 126 μT

  If the magnitude of the magnetic field is on the order, a sensor signal output larger than the noise of the magnetic sensor 100 itself and the noise of the resistance detection circuit 85 can be obtained. That is, the magnetization direction of the first free layer 41 changes according to the fluctuation of the external magnetic field generated by the coil current Ic, and the sensor resistance values TMR1 and TMR2 change. The resistance detection circuit 85 can sense the coil current Ic by detecting the resistance values of TMR1 and TMR2.

  In the conventional magnetic sensor, the alternating current path and the sensor are configured by separate wiring and elements, respectively, and are arranged close to each other, so that the magnetic field generated in the sensor unit is small. Therefore, the conventional magnetic sensor cannot detect the alternating current value or the alternating current frequency due to the noise of the sensor itself or the noise of the detection circuit unless a current of the order of mA is passed. On the other hand, since the magnetic sensor 100 of this example detects the current flowing through the pinned layer 20 immediately below the sensor resistance, it can detect a change in current caused by a small fluctuation of the external magnetic field with high accuracy. That is, the magnetic sensor 100 can detect the fluctuation of the external magnetic field in a very small area. In addition, since the pinned layer 20 and the free layer 40 that detects the current-induced magnetic field are integrated, there is no positional shift due to secular change, and fluctuations in the external magnetic field in a small region can be stably measured over a long period of time. Further, the magnetic sensor 100 of this example can be manufactured inexpensively with a small area without newly adding process steps.

<Embodiment 2>
10 and 11A to 11C show the magnetic sensor 100 according to the second embodiment. The magnetic sensor 100 of this example includes a metal wiring layer 65 instead of the intermediate layer 25 between the first pinned layer 21 and the second pinned layer 22. 11A, 11B, and 11C are cross-sectional views of the magnetic sensor 100 taken along dotted lines AA ′, BB ′, and CC ′. Note that the wiring layer 26 may be formed of the same material as the metal wiring layer 65.

  Since the metal wiring layer 65 can reduce the resistance as compared with the intermediate layer 25, RPC between the first pinned layer 21 and the second pinned layer 22 can be reduced. The metal wiring layer 65 may be formed of the same material as the first upper wiring layer 61 and the second upper wiring layer 62. In this case, the metal wiring layer 65 can be formed in the same process as the first upper wiring layer 61 and the second upper wiring layer 62. Therefore, the magnetic sensor 100 according to the present embodiment can be manufactured without providing a new process step from the manufacturing step according to the first embodiment.

<Embodiment 3>
12 to 14 show the magnetic sensor 100 according to the third embodiment. In the magnetic sensor 100 according to the first embodiment, a region where the current measurement range is limited by RPC occurs. On the other hand, the magnetic sensor 100 of this example can eliminate the resistance of the RPC by pulling out the third external connection terminal 73 and the fourth external connection terminal 74 from the pinned layer 20, respectively.

  FIG. 12 is a layout view of the magnetic sensor 100 as viewed from above. 13A, 13B, 13C, and 13D are cross-sectional views of the magnetic sensor 100 taken along dotted lines AA ′, dotted lines BB ′, dotted lines CC ′, and dotted lines DD ′. The magnetic sensor 100 of this example includes a third pinned layer 23, a third tunnel layer 33, a third free layer 43, a third cover layer 53, a fourth pinned layer 24, a fourth tunnel layer 34, A fourth free layer 44, a fourth cover layer 54, a third upper wiring layer 63, a fourth upper wiring layer 64, a third external connection terminal 73, and a fourth external connection terminal 74 are further provided. The resistance detection circuit 85 of this example further includes a voltmeter VM2.

  The third pinned layer 23 is formed extending from the first pinned layer 21. The third pinned layer 23 may be formed simultaneously with the first pinned layer 21. The other end of the third pinned layer 23 is connected to the third external connection terminal 73.

  The third tunnel layer 33 is formed on the third pinned layer 23. The third tunnel layer 33 prevents the coil current Ic flowing in the third pinned layer 23 from flowing to the third upper wiring layer 63 side. The third tunnel layer 33 in this example is formed on at least a part of the third pinned layer 23.

  The third free layer 43 is formed on the third tunnel layer 33. The third free layer 43 of this example has the same cross-sectional shape of the film surface as the third tunnel layer 33.

  The third cover layer 53 protects the upper part of the third free layer 43. The third cover layer 53 is continuously formed on the third free layer 43.

  The third upper wiring layer 63 includes a third external connection terminal 73 connected to the resistance detection circuit 85. The third upper wiring layer 63 is formed apart from the third pinned layer 23.

  The fourth pinned layer 24 is formed extending from the second pinned layer 22. The fourth pinned layer 24 may be formed simultaneously with the second pinned layer 22. The other end of the fourth pinned layer 24 is connected to the fourth external connection terminal 74.

  The fourth tunnel layer 34 is formed on the fourth pinned layer 24. The fourth tunnel layer 34 prevents the coil current Ic flowing in the fourth pinned layer 24 from flowing to the fourth upper wiring layer 64 side. The fourth tunnel layer 34 in this example is formed on at least a part of the fourth pinned layer 24.

  The fourth free layer 44 is formed on the fourth tunnel layer 34. The fourth free layer 44 of this example has the same cross-sectional shape as the fourth tunnel layer 34 and the film surface.

  The magnetization direction of the third free layer 43 and the fourth free layer 44 is not changed by the current-induced magnetic field Bc. That is, the coil current Ic does not flow through the third pinned layer 23 and the fourth pinned layer 24. The fact that the coil current Ic does not flow means that the magnetization directions of the third free layer 43 and the fourth free layer 44 are not changed by the current-induced magnetic field Bc in addition to the case where the coil current Ic does not flow completely. The case where the coil current Ic flows may be included.

  The fourth cover layer 54 protects the upper part of the fourth free layer 44. The fourth cover layer 54 is continuously formed on the fourth free layer 44.

  The fourth upper wiring layer 64 includes a fourth external connection terminal 74 connected to the resistance detection circuit 85. The fourth upper wiring layer 64 is formed to be separated from the fourth pinned layer 24.

  FIG. 14 is a circuit conceptual diagram of the magnetic sensor 100 according to the third embodiment. Compared to FIG. 8, resistors RS3 and RS4 are further added to the circuit conceptual diagram of the magnetic sensor 100 of this example. RS3 is the sum of the resistance value of the third pinned layer 23 and the resistance value from the third pinned layer 23 to the third free layer 43. RS4 is the sum of the resistance value of the fourth pinned layer 24 and the resistance value from the fourth pinned layer 24 to the fourth free layer 44. RS3 and RS4 are connected across the RPC.

  The resistance detection circuit 85 detects a resistance value between the first free layer 41 and the third free layer 43 and a resistance value between the second free layer 42 and the fourth free layer 44. Thus, the coil current Ic is detected. The resistance value between the first free layer 41 and the third free layer 43 refers to the sum of the resistance values of TMR1 and RS3. The resistance value between the second free layer 42 and the fourth free layer 44 refers to the sum of the resistance values of TMR2 and RS4. The resistance detection circuit 85 causes a detection current to flow from the first external connection terminal 71 to the second external connection terminal 72.

  The voltmeter VM1 is connected in series with TMR1 and RS3, and measures the first sensor resistance TMR1. That is, the voltage measurement circuit loop of the voltmeter VM1 does not incorporate RPC. Therefore, the voltmeter VM1 can measure the first sensor resistance TMR1 without being affected by RPC.

  The voltmeter VM2 is connected in series with TMR2 and RS4, and measures the second sensor resistance TMR2. That is, the voltage measurement circuit loop of the voltmeter VM2 does not incorporate RPC. Therefore, the voltmeter VM2 can measure the second sensor resistance TMR2 without being affected by RPC. Thereby, the resistance detection circuit 85 can eliminate the influence of RPC.

<Manufacturing method>
15A to 15G show an example of a method for manufacturing the magnetic sensor 100. FIG. 15A shows the substrate 90 on which the pinned layer 20 is formed. The substrate 90 in this example is made of silicon. The surface of the substrate 90 in this example is covered with a first insulating film 91. For example, the first insulating film 91 is an insulating film used in a general manufacturing process such as silicon dioxide SiO ₂ . The pinned layer 20 is formed by sputtering. Sputtering for forming the pinned layer 20 may be performed in a state where a magnetic field is applied.

  FIG. 15B shows a process of fixing the magnetization of the pinned layer 20. The magnetization of the pinned layer 20 is fixed by heat treatment in a magnetic field. For example, the magnetic field is directed in a direction in which the magnetization of the pinned layer 20 is fixed.

  FIG. 15C shows a process of forming a TMR element. A tunnel layer 30, a free layer 40 and a cover layer 50 are formed on the pinned layer 20.

  FIG. 15D shows an element separation process of the magnetic sensor 100. The magnetic sensor 100 removes unnecessary portions from the cover layer 50 to the pinned layer 20 using a photolithography process, an ion milling process, or the like. As a result, element-isolated TMR elements are formed.

  FIG. 15E shows a process of patterning the TMR element. In the magnetic sensor 100, the unnecessary free layer 40 and the cover layer 50 are removed by using a photolithography process, an ion milling process, or the like. Note that the tunnel layer 30 may be removed in the same pattern as the unnecessary free layer 40 and the cover layer 50.

  Further, when the metal wiring layer 65 is formed instead of the intermediate layer 25 as in the second embodiment, the pinned layer 20 in the region where the metal wiring layer 65 is formed is removed by using a photolithography process, an ion milling process, or the like. To do. Thereafter, a metal wiring layer 65 is deposited in the region where the pinned layer 20 has been removed. Thereby, the metal wiring layer 65 can be formed instead of the intermediate layer 25.

FIG. 15F shows a step of depositing the second insulating film 92. A second insulating film 92 is formed on the entire surface of the substrate 90. The second insulating film 92 in this example is formed of silicon dioxide SiO ₂ . The second insulating film 92 may be the same material as the first insulating film 91 or a different material.

  FIG. 15G shows the magnetic sensor 100 in which the upper wiring layer 60 is formed. Openings are formed in the pattern of the upper wiring layer 60 on the second insulating film 92 by a photolithography process, an ion milling process, or the like. Thereafter, the upper wiring layer 60 is formed by a metal sputtering and lift-off process. As a result, a lead-out wiring that connects the magnetoresistive effect elements TMR and a connection wiring to the outside are formed. The pinned layer 20 may be connected to a coil having a plurality of turns. In this case, the number of turns of the coil can be adjusted by providing a plurality of wiring layers 26 in the chip of the magnetic sensor 100. The number of turns of the coil is appropriately changed according to the magnitude of fluctuation of the external magnetic field to be measured.

  As described above, the magnetic sensor 100 of this example is manufactured by using the same manufacturing process as the conventional one. Further, the magnetic sensor 100 can stably measure a minute and precise fluctuation of the external magnetic field by detecting the current with higher accuracy than the conventional magnetic sensor, and can be formed in a small size.

  FIG. 16 shows an example of the magnetic detection device 200. The magnetic detection device 200 includes a magnetic sensor 100, a voltage generation circuit 86, an amplification circuit 95, an amplitude detection circuit 96, and a frequency detection circuit 97. The magnetic detection device 200 detects the frequency and amplitude of the external magnetic field by processing the signal detected by the magnetic sensor 100 using a circuit at the subsequent stage.

  The magnetic sensor 100 detects a resistance value (TMR1, TMR2) corresponding to a change in the external magnetic field and outputs a sensor input signal Vin. In the resistance detection circuit 85 of this example, one end of the first constant current source IS1 is connected to the ground potential (GND), and a sensor input signal Vin corresponding to the resistance values (TMR1, TMR2) is output from one end of the ammeter IM. To do. The resistance detection circuit 85 does not connect one end of the first constant current source IS1 to the ground potential, but differentially outputs signals at the ends of the ammeter IM and the first constant current source IS1. May be.

  The voltage generation circuit 86 outputs the reference signal Vref to the amplification circuit 95 at the next stage. The voltage generation circuit 86 includes a second constant current source IS2 and a reference resistor Rref. The reference resistance Rref has a resistance value comparable to the combined resistance value of the magnetic sensor 100 (TMR1 + TMR2 or TMR1 + TMR2 + RPC, etc.). For example, the same level as the combined resistance value of the magnetic sensor 100 is the combined resistance value of the magnetic sensor 100 when the coil current Ic does not flow. The second constant current source IS2 passes a reference current IS2 having a current value approximately equal to the reference current IS1 output from the first constant current source IS1 of the resistance detection circuit 85. Thereby, the voltage generation circuit 86 generates the reference signal Vref of the same level as the sensor input signal Vin, and can secure an operating point.

  The amplifier circuit 95 receives the sensor input signal Vin from the resistance detection circuit 85 and the reference signal Vref from the voltage generation circuit 86. The amplifier circuit 95 outputs an amplified signal Vg obtained by amplifying the difference between the sensor input signal Vin and the reference signal Vref with an amplification factor Gain. When the output of the resistance detection circuit 85 is differential, the resistance detection circuit 85 may differentially amplify the reference signal Vref of the voltage generation circuit 86 as a common voltage.

  The amplitude detection circuit 96 receives the amplified signal Vg from the amplifier circuit 95 and outputs an amplitude signal Va. The amplitude detection circuit 96 includes a diode Dr, a capacitor Cr, and a load resistor Rr. When a forward bias is applied to the diode Dr, charge is stored in the capacitor Cr. Further, when a reverse bias is applied to the diode Dr, the charge stored in the capacitor Cr is released. The amplitude detection circuit 96 is a rectifier that half-wave rectifies the signal input from the amplifier circuit 95. From the amplitude signal Va, the amplitude of the external magnetic field signal can be detected. The external magnetic field signal refers to a signal detected as an external magnetic field input to the magnetic detection device 200.

  The frequency detection circuit 97 receives the amplified signal Vg from the amplifier circuit 95 and outputs a frequency signal Df. The frequency detection circuit 97 includes a comparator 98 and a frequency counter 99. The comparator 98 compares the amplified signal Vg of the amplifier circuit 95 with the ground potential (GND) and outputs a comparator output signal Vc. The frequency counter 99 counts the comparator output signal Vc of the comparator 98 and generates a frequency signal Df.

  FIG. 17A to FIG. 17D show waveform examples of each signal. In this example, an external magnetic field signal whose frequency gradually decreases is input to the magnetic detection device 200. Further, the external magnetic field signal of this example gradually decreases in frequency and gradually decreases in amplitude.

  FIG. 17A shows an example of the output of the amplifier circuit 95. The amplified signal Vg is a signal obtained by amplifying the sensor input signal Vin of the magnetic sensor 100. A solid line indicates the amplified signal Vg. The broken line is a line that roughly connects the maximum value or the minimum value of the amplified signal Vg. The amplified signal Vg in this example gradually decreases in frequency and amplitude.

  FIG. 17B shows an example of the output of the amplitude detection circuit 96. A solid line indicates the amplitude signal Va. The broken line indicates the absolute value of the amplified signal Vg. When the external magnetic field signal detected by the magnetic detection device 200 changes from an external magnetic field signal with a large amplitude to an external magnetic field signal with a small amplitude, the amplitude signal Va of the amplitude detection circuit 96 is matched to the change in the amplitude of the external magnetic field signal. Gradually get smaller.

  FIG. 17C shows an example of the output of the comparator 98. A solid line indicates the output signal Vc, and a broken line indicates the amplified signal Vg. When the amplified signal Vg of the amplifier circuit 95 becomes larger than a predetermined value, the comparator output signal Vc becomes high. On the other hand, when the amplified signal Vg of the amplifier circuit 95 is smaller than a predetermined value, the comparator output signal Vc becomes low. The signal that the comparator 98 compares with the amplified signal Vg is not limited to a signal from the ground potential, and may be an arbitrary signal.

  FIG. 17D shows an example of the frequency signal Df of the frequency counter 99. When the frequency of the external magnetic field signal detected by the magnetic detection device 200 is gradually decreased, the frequency signal Df of the frequency counter 99 is gradually decreased in accordance with the change in the frequency of the external magnetic field.

  As described above, the magnetic detection device 200 can detect changes in the frequency and amplitude of the external magnetic field signal. Since the magnetic detection device 200 includes the magnetic sensor 100, it is possible to detect a change in the external magnetic field in a very small region.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  The order of execution of each process such as operations, procedures, steps, and stages in the apparatus, system, program, and method shown in the claims, the description, and the drawings is particularly “before” or “prior to”. It should be noted that the output can be realized in any order unless the output of the previous process is used in the subsequent process. Regarding the operation flow in the claims, the description, and the drawings, even if it is described using “first”, “next”, etc. for convenience, it means that it is essential to carry out in this order. It is not a thing.

DESCRIPTION OF SYMBOLS 1 ... Magnetoresistive effect element, 20 ... Pinned layer, 21 ... 1st pinned layer, 22 ... 2nd pinned layer, 23 ... 3rd pinned layer, 24 ... 4th pinned layer 25 ... intermediate layer 26 ... wiring layer 30 ... tunnel layer 31 ... first tunnel layer 32 ... second tunnel layer 33 ...・ Third tunnel layer 34... Fourth tunnel layer 35. Tunnel junction 40 .free layer 41 .first free layer 42 .second free Layer, 43... Third free layer, 44... Fourth free layer, 50... Cover layer, 51... First cover layer, 52. ... third cover layer, 54 ... fourth cover layer, 60 ... upper wiring layer, 61 ... first upper wiring layer, 62 ... second upper wiring layer 63, third upper wiring layer, 64, fourth upper wiring layer, 65, metal wiring layer, 71, first external connection terminal, 72, second. External connection terminal, 73 ... third external connection terminal, 74 ... fourth external connection terminal, 85 ... resistance detection circuit, 90 ... substrate, 91 ... first insulating film, 92 ... Second insulating film, 95 ... Amplification circuit, 96 ... Amplitude detection circuit, 97 ... Frequency detection circuit, 98 ... Comparator, 99 ... Frequency counter, 100 ... Magnetic sensor, 200 ... magnetic detection device

Claims (11)

A conductive layer having a first pinned layer in which magnetization is fixed in a first direction and a tunnel junction layer formed apart from the first pinned layer and formed in a loop;
A first tunnel layer formed on the first pinned layer;
A magnetic sensor comprising: a first free layer formed on the first tunnel layer and having a magnetization direction changed by a magnetic field generated by a coil current generated by a change in an external magnetic field. The tunnel junction layer is
A second pinned layer which is provided in series with the first pinned layer, the coil current flows, and the magnetization is fixed in a first direction;
A second tunnel layer formed on the second pinned layer;
The magnetic sensor according to claim 1, further comprising: a second free layer formed on the second tunnel layer and having a magnetization direction changed by a magnetic field generated by a coil current generated by a change in the external magnetic field. A third pinned layer formed extending from the conductive layer;
A fourth pinned layer formed extending from the conductive layer;
A third tunnel layer formed on the third pinned layer;
A fourth tunnel layer formed on the fourth pinned layer;
A third free layer formed on the third tunnel layer, the direction of magnetization of which is not changed by the magnetic field generated by the coil current;
The magnetic sensor according to claim 2, further comprising: a fourth free layer formed on the fourth tunnel layer and having a magnetization direction not changed by a magnetic field generated by the coil current.   The magnetic sensor according to claim 3, wherein the coil current does not flow through the third pinned layer and the fourth pinned layer.   5. The magnetic sensor according to claim 2, further comprising a resistance detection circuit that detects a change in the external magnetic field based on a resistance value between the first free layer and the second free layer. .   By detecting a resistance value between the first free layer and the third free layer and a resistance value between the second free layer and the fourth free layer, the external magnetic field is detected. The magnetic sensor according to claim 3, further comprising a resistance detection circuit that detects fluctuation.   The magnetic sensor according to claim 2, wherein the conductive layer is formed of a pinned layer. A first upper wiring layer formed on the first free layer;
The magnetic sensor according to claim 2, further comprising: a second upper wiring layer formed on the second free layer. A magnetic sensor according to any one of claims 2 to 8,
A resistance detection circuit for detecting a resistance value between the first free layer and the second free layer;
A magnetic detection device comprising: An amplitude detection circuit for detecting the amplitude of the output signal from the output signal of the resistance detection circuit;
The magnetic detection device according to claim 9, further comprising: a frequency detection circuit that detects a frequency of the output signal from the output signal of the resistance detection circuit. Forming a looped pinned layer on the substrate;
Forming a tunnel layer on the pinned layer;
Forming a free layer on the tunnel layer;
Etching the free layer and the tunnel layer to separate the first tunnel layer and the second tunnel layer, the first free layer on the first tunnel layer, and the second tunnel layer Forming a second free layer of
Forming a first upper wiring layer on the first free layer, and forming a second upper wiring layer on the second free layer;
Forming a first external connection terminal and a second external connection terminal on the pinned layer;
Forming a third external connection terminal in the first upper wiring layer and forming a fourth external connection terminal in the second upper wiring layer;
A method of manufacturing a magnetic sensor comprising:

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