JP5631378B2 - Magnetic field detection method - Google Patents

Description

  The present invention relates to a magnetic field detection device and a magnetic field detection method for detecting a magnetic field applied from the outside using a magnetoresistance effect.

  In addition to the Hall element, a magnetoresistive effect element is known as a magnetic field detection element for detecting a magnetic field applied from the outside. The magnetoresistive effect element includes an AMR (Anisotropic Magneto-Resistance) element utilizing a magnetoresistive effect of a metal, a GMR (Giant Magneto-Resistance) element utilizing a giant magnetoresistive effect, and a TMR (TMR using a tunnel magnetoresistive effect). Tunnel Magneto-Resistance) element. In particular, GMR elements and TMR elements that can obtain a larger MR ratio than others are drawing attention.

  Japanese Patent Publication No. 8-21166 (Patent Document 1) discloses a GMR element and a TMR element having a spin valve structure. A magnetoresistive effect element having a spin valve structure has a first thin film layer (free layer) and a second thin film layer (fixed layer) of ferromagnetic material partitioned by a nonmagnetic thin film layer. When the applied magnetic field is 0, the magnetization direction of the first thin film layer of the ferromagnetic material is set to be orthogonal to the magnetization direction of the second thin film layer of the ferromagnetic material. The magnetization direction of the thin film layer is fixed. In order to fix the magnetization direction of the second thin film layer, a high electrical resistance antiferromagnetic thin film layer is deposited in direct contact with the ferromagnetic second thin film layer. As an alternative structure, the antiferromagnetic thin film layer may be a ferromagnetic layer having high coercivity and high electrical resistance.

  Further, in the magnetoresistive effect element disclosed in Japanese Patent Application Laid-Open No. 2005-236134 (Patent Document 2), a fixed layer having a magnetization direction fixed in a fixed direction, an external magnetic field that changes according to an external magnetic field, and the external A stacked body is provided that includes a free layer having a magnetization direction parallel to the magnetization direction of the pinned layer when the magnetic field is 0, and an intermediate layer sandwiched between the pinned layer and the free layer. The magnetoresistive element further includes a bias current line extending in the magnetization direction of the permanent magnet or the pinned layer in order to apply a bias magnetic field in a direction orthogonal to the magnetization direction of the pinned layer. By applying a bias magnetic field having an appropriate strength, the resistance change of the read current with respect to the external magnetic field can be made linear.

Japanese Examined Patent Publication No. 8-21166 JP-A-2005-236134

  However, when a current line is installed adjacent to the magnetoresistive effect element and a bias magnetic field is applied, it is necessary to provide an insulating film in order to maintain electrical insulation between the current line and the magnetoresistive effect element. The insulating properties and durability of the insulating film are improved as the thickness of the insulating film is increased.

  On the other hand, the magnetic field H generated at a distance r from the uniform current I is given by H = I / (2πr) according to Ampere's law. Here, π is the circumference ratio. Therefore, the thicker the insulating film, the larger the distance r between the current line and the magnetoresistive effect element. Therefore, in order to keep the bias magnetic field constant, it is necessary to increase the current I flowing through the current line.

  For the above reason, the current required to apply a desired bias magnetic field to the magnetoresistive effect element increases as the film thickness is increased in order to further improve the insulation and durability of the insulating film. For this reason, there exists a problem that the power consumption of a magnetic field detection apparatus will increase.

  The present invention has been made to solve such problems. An object of the present invention is to provide a magnetic field detection device and a magnetic field detection method with low power consumption and high magnetic field detection accuracy.

  In summary, the present invention is a magnetic field detection device for detecting an external magnetic field, and includes one or a plurality of detection elements, a bias current supply unit, a measurement unit, and a calculation unit. Each of the one or more detection elements includes a first ferromagnetic film whose magnetization direction changes according to an external magnetic field, a second ferromagnetic film whose magnetization direction is constant, and a space between these ferromagnetic films. A tunnel magnetoresistive element including a tunnel insulating film sandwiched between layers. The bias current supply unit has a film surface on one of the first and second ferromagnetic films in order to change the magnetization direction of the first ferromagnetic film for each of the one or more detection elements. Supply directional bias current. The measurement unit measures the electrical characteristics of the detection element according to the change in the magnetization direction of the first ferromagnetic film in each of the one or more detection elements. The calculation unit calculates an external magnetic field based on the electrical characteristics of each of the one or more detection elements measured by the measurement unit.

  According to the present invention, since a bias current flows through one electrode of the tunnel magnetoresistive effect element, a bias magnetic field can be applied to the tunnel magnetoresistive effect element with less power consumption than when a separate bias current wiring layer is provided. Can be applied. Further, the magnetic field detection accuracy can be improved by changing the magnitude of the bias magnetic field in accordance with the external magnetic field.

It is a top view which shows typically the structure of the magnetic field detection apparatus 1 by Embodiment 1 of this invention. It is a perspective view which shows typically the structure of the magnetic field detection apparatus 1 of FIG. It is sectional drawing which follows the III-III line of FIG. 3 is a cross-sectional view illustrating in detail a configuration of a joint portion of the detection element 10. It is a figure which shows the relationship between the external magnetic field Hex and element resistance R in case the external magnetic field Hex and the bias magnetic field Hb are parallel. It is a figure which shows the relationship between the external magnetic field Hex and element resistance in case the external magnetic field Hex and the bias magnetic field Hb are perpendicular | vertical. It is a figure for demonstrating the relationship between the direction of the external magnetic field Hex and the bias magnetic field Hb, and a magnetization direction. It is a figure for demonstrating operation | movement of the magnetic field detection apparatus 1 of FIG. It is a flowchart which shows the detection procedure of the external magnetic field Hex by the magnetic field detection apparatus 1 of FIG. 6 is a diagram for explaining a method of detecting an external magnetic field Hex according to the first modification of the first embodiment. FIG. 10 is a flowchart showing a procedure for detecting an external magnetic field Hex according to the first modification of the first embodiment. 6 is a cross-sectional view showing a configuration of a TMR element according to a second modification of the first embodiment. FIG. 6 is a cross-sectional view showing a configuration of a TMR element according to a third modification of the first embodiment. FIG. It is a top view which shows typically the structure of the magnetic field detection apparatus 2 by Embodiment 2 of this invention. It is a perspective view which shows typically the structure of the principal part of the magnetic field detection apparatus 2 of FIG. It is a top view which shows typically the structure of 2 A of magnetic field detection apparatuses by the modification of Embodiment 2 of this invention. It is a perspective view which shows typically the structure of the principal part of the magnetic field detection apparatus 2A of FIG. It is a top view which shows typically the structure of the magnetic field detection apparatus 3 by Embodiment 3 of this invention. It is a figure for demonstrating operation | movement of the magnetic field detection apparatus 3 of FIG. It is a flowchart which shows the detection procedure of the external magnetic field Hex by the magnetic field detection apparatus 3 of FIG. 18, FIG. It is a top view which shows typically the structure of 3 A of magnetic field detection apparatuses by the modification 1 of Embodiment 3 of this invention. It is a figure for demonstrating a structure and operation | movement of the magnetic field detection apparatus 3B by the modification 2 of Embodiment 3 of this invention. It is a top view which shows typically the structure of the magnetic field detection apparatus 4 by Embodiment 4 of this invention. It is a figure for demonstrating operation | movement of the magnetic field detection apparatus 4A by Embodiment 4 of this invention. It is a flowchart which shows the detection procedure of the external magnetic field Hex by the magnetic field detection apparatus 4A of FIG. It is a top view which shows typically the structure of the magnetic field detection apparatus 5 by Embodiment 5 of this invention. It is the flowchart which showed the procedure which detects the direction of the external magnetic field Hex by the magnetic field detection apparatus 5 of FIG. It is a top view which shows typically the structure of 5 A of magnetic field detection apparatuses by the modification of Embodiment 5 of this invention. It is a figure which shows typically the structure of the rotation angle sensor 6 by Embodiment 6 of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

[Embodiment 1]
(Configuration of magnetic field detection device 1)
FIG. 1 is a plan view schematically showing a configuration of a magnetic field detection apparatus 1 according to Embodiment 1 of the present invention.

FIG. 2 is a perspective view schematically showing a configuration of the magnetic field detection device 1 of FIG.
3 is a cross-sectional view taken along line III-III in FIG. Hereinafter, the configuration of the magnetic field detection apparatus 1 will be described with reference to FIGS. In the following description, the directions of the coordinate axes are represented by the X-axis direction, the Y-axis direction, and the Z-axis direction. When written simply as X-axis direction, Y-axis direction, or Z-axis direction, it means both the + direction and-direction, and when displaying the direction by distinguishing + direction and-direction, + X direction, -X direction It shall be described with a reference numeral.

  The magnetic field detection device 1 includes a detection element 10 that detects a magnetic field, a voltage source 21, a resistance element 22, a differential amplifier circuit 23, a reference voltage source 24, a control unit 25, and a current as a bias current supply unit. Source 31. Here, the voltage source 21, the resistance element 22, the differential amplifier circuit 23, and the reference voltage source 24 constitute a measurement unit 20 for measuring the resistance value of the detection element 10.

  The detection element 10 is a tunnel magnetoresistive effect element (TMR element) formed on the substrate 40, and includes an upper electrode 18 located at the upper part and a lower electrode 17 located at the lower part with the insulating layer 14 in between. The upper electrode 18 of the detection element 10 is connected to the wiring layer 43 through a conductive portion 46 formed in the contact hole. The wiring layer 43 is electrically connected to the measurement unit 20 formed on the substrate 40. FIG. 2 shows a MOS (Metal-Oxide Semiconductor) transistor 29 as a representative of the semiconductor elements constituting the measurement unit 20.

  Further, the lower electrode 17 of the detection element 10 is connected to the wiring layer 41 via a conductive portion 44 formed in the contact hole, and is connected to the wiring layer 42 via a conductive portion 45 formed in the contact hole. The The wiring layer 41 is connected to the current source 31 and the wiring layer 42 is connected to the ground GND. FIG. 2 shows a MOS transistor 39 as a representative of the semiconductor elements constituting the current source 31. The conductive portion 44 and the conductive portion 45 formed in the contact hole are provided on both sides in the Y-axis direction across the joint portion of the detection element 10.

  The wiring layers 41 to 43 may be formed of a conductive material, but are preferably formed of a wiring material used in a silicon integrated circuit or the like. For example, it is made of a material such as Al, AlSi, AlSiCu, AlCu. The conductive portions 44 to 46 formed in the contact holes may be formed of a conductive material, but preferably include conductive materials including W, Ti, Co, Si, Ta, Mo, Ru, Pt, Au, and the like. Formed of a metallic material.

  FIG. 4 is a cross-sectional view showing in detail the configuration of the joint of the detection element 10. Referring to FIG. 4, detection element 10 includes, in order from the substrate side, nonmagnetic conductor 11, antiferromagnetic layer 12, ferromagnetic layer (fixed layer) 13, insulating layer 14, ferromagnetic layer (free layer) 15, And the nonmagnetic conductor 16 is laminated | stacked and formed. The nonmagnetic conductor 11, the antiferromagnetic layer 12, and the ferromagnetic layer 13 are included in the lower electrode 17, and the ferromagnetic layer (free layer) 15 and the nonmagnetic conductor 16 are included in the upper electrode.

  The magnetization direction of the ferromagnetic layer (pinned layer) 13 is fixed in one direction by exchange coupling with the antiferromagnetic layer 12. On the other hand, the magnetization direction of the ferromagnetic layer (free layer) 15 changes according to the external magnetic field. The resistance of the magnetoresistive element having such a spin valve structure changes according to the angle formed by the magnetization direction of the ferromagnetic layer (pinned layer) 13 and the magnetization direction of the ferromagnetic layer (free layer) 15. In other words, the element resistance changes as the magnetization direction of the ferromagnetic layer (free layer) 15 changes due to the influence of the external magnetic field. For this reason, the external magnetic field can be detected by the element resistance.

  In general, in the TMR element, the resistance is the minimum value when the magnetization direction of the free layer and the magnetization direction of the pinned layer are parallel, and the resistance is the maximum value when the magnetization direction of the free layer and the magnetization direction of the pinned layer are antiparallel. It becomes. In the case of a TMR element, the thickness of each layer is 1/100 or less with respect to the pattern size of the element and is strongly influenced by shape anisotropy. Therefore, it is very difficult to change the magnetization direction in the direction perpendicular to the substrate 40 (Z-axis direction in FIGS. 1 to 3), and the magnetization direction of the ferromagnetic layer (free layer) 15 is limited to the in-plane direction of the substrate. Further, when an external magnetic field is applied in the direction perpendicular to the substrate 40, the change in the magnetization direction of the ferromagnetic layer (free layer) 15 can be ignored, and as a result, the change in element resistance can also be ignored.

The structure of the above TMR element is, for example, IrMn as the antiferromagnetic layer 12, NiFe or CoFe as the ferromagnetic layer (fixed layer) 13, Al ₂ O ₃ as the insulating layer 14, and NiFe as the ferromagnetic layer (free layer) 15. Can be configured. In addition, FeMn, IrMn, and PtMn can be used as the antiferromagnetic layer 12. Further, as the ferromagnetic layers 13 and 15, a metal containing Co, Ni, Fe such as Co, Ni, Fe such as Co, Fe, CoFe alloy, CoNi alloy, CoFeNi alloy, an alloy such as NiMnSb, Co ₂ MnGe, or the like is used. Can do. There is no particular limitation as long as it is a material capable of obtaining desired performance as a TMR element. The insulating layer 14 used as the tunnel insulating film may be an insulator of a nonmagnetic layer. For example, a metal oxide such as Ta ₂ O ₅ , SiO ₂ , MgO, fluoride, or the like can be used for the insulating layer 14.

  Unlike the first embodiment, the ferromagnetic layer (free layer) 15 is included in the lower electrode, and the ferromagnetic layer (fixed layer) 13 and the antiferromagnetic layer 12 are included in the upper electrode. You can also Further, the ferromagnetic layer (free layer) 15 may be a single magnetic layer as shown in FIG. 4, or may have a structure in which two or more kinds of magnetic layers are laminated unlike FIG. .

  Moreover, each said layer is formed by DC magnetron sputtering, for example. In addition, each layer may be formed by a molecular beam epitaxy (MBE) method, various sputtering methods, a chemical vapor deposition (CVD) method, a vapor deposition method, or the like.

  The above element structure is produced, for example, by photolithography patterning and etching. In this case, after forming the laminated film, a desired pattern is formed by a photoresist using photolithography. Thereafter, the element shape is obtained by ion milling or reactive ion etching using the patterned photoresist as a mask. Note that electron beam lithography may be used instead of photolithography, or focused ion beam processing may be used.

  The configuration of the measurement unit 20 will be described with reference to FIGS. 1 to 3 again. The resistance element 22 and the voltage source 21 in FIG. 1 are connected in series between the wiring layer 43 and the wiring layer 42. The wiring layer 43 is connected to the + terminal of the differential amplifier circuit 23. On the other hand, the reference voltage Vref is applied to the negative terminal of the differential amplifier circuit 23 by the reference voltage source 24. The differential amplifier circuit 23 amplifies the difference between the voltage Vd1 of the connection node Nd1 of the resistance element 22 and the detection element 10 and the reference voltage Vref and outputs the amplified difference to the control unit 25.

  By configuring a half bridge composed of the detection element 10 and the resistance element 20 as described above, the output voltage Vout having a magnitude corresponding to the resistance value between the upper electrode 18 and the lower electrode 17 of the detection element 10 is controlled. Is output to the unit 25.

  The control unit 25 is configured by a computer and includes a calculation unit 26 and a storage unit 27. The computing unit 26 calculates the magnitude of the unknown external magnetic field based on the output voltage Vout of the differential amplifier circuit 23. A specific calculation method will be described later with reference to FIGS. The storage unit 27 stores data necessary for processing of the arithmetic unit 26 such as an output of the differential amplifier circuit 23. The control unit 25 controls the operation of the voltage source 21 and the current source 31. Note that, unlike the case of the first embodiment, the arithmetic unit 26 may be configured by an analog circuit using an operational amplifier or the like.

  The current source 31 is connected between the wiring layer 41 and the wiring layer 42. By applying a bias current Ib in the Y-axis direction to the lower electrode 17 by the current source 31, a bias magnetic field Hb in the X-axis direction is applied to the junction of the detection element 10.

  In the magnetic field detection apparatus 1 according to the first embodiment, since the bias magnetic field Ib can be applied in addition to the unknown external magnetic field, it becomes possible to adjust the sensitivity of the magnetic field as will be described later, reducing the measurement error and accurately. An external magnetic field can be detected. Further, since the bias current Ib is passed through the lower electrode 17 closest to the ferromagnetic layer (free layer) 15, it is possible to apply a magnetic field to the TMR element with a slight current, and power consumption can be saved.

  For example, consider applying a bias magnetic field Hb of 20 Oe to the detection element 10. In this case, in order to pass a current through a wiring provided via a 0.1 μm insulating film in order to protect the detection element 10, a bias current Ib of 1 mA is required according to Ampere's law.

  On the other hand, when a current is passed through the lower electrode 17 of the detection element 10, the bias current Ib can be reduced. For example, since the specific resistance of the nonmagnetic conductor 11 is sufficiently smaller than the specific resistance of the other layers (the antiferromagnetic layer 12 and the ferromagnetic layer 13) constituting the lower electrode 17, the bias current Ib flowing through the lower electrode 17 is Consider a case where the current mainly flows through the nonmagnetic conductor 11. In this case, if the total thickness of the antiferromagnetic layer 12 and the ferromagnetic layer 13 is 10 nm, the bias current Ib mainly flows through the nonmagnetic conductor 11 formed at a position 10 nm below the insulating layer 14. Therefore, a bias magnetic field Hb of approximately 20 Oe as in the above case can be obtained with a bias current Ib of 0.1 mA, and power consumption can be reduced. In particular, there is a remarkable effect when a large current is applied as in a reference element described later.

(Operation of Magnetic Field Detection Device 1)
Next, the operation of the magnetic field detection device 1 will be described.

  In the magnetic field detection device 1 of the first embodiment, the magnetization direction of the ferromagnetic layer (free layer) 15 in FIG. 4 is determined by the external magnetic field Hex and the bias magnetic field Hb. Further, the resistance value of the detection element 10 (TMR element) changes according to the angle formed by the magnetization direction of the ferromagnetic layer (free layer) 15 and the magnetization direction of the ferromagnetic layer (fixed layer) 13.

  First, the case where the direction of the external magnetic field Hex and the direction of the bias magnetic field Hb are parallel or antiparallel (when the direction of the external magnetic field Hex and the direction of the bias current Ib are perpendicular) will be described. In this case, by generating a bias magnetic field Hb having an appropriate magnitude according to the external magnetic field Hex, the range of the external magnetic field Hex that can be measured by the detection element 10 (TMR element) can be shifted.

  FIG. 5 is a diagram illustrating a relationship between the external magnetic field Hex and the element resistance R when the external magnetic field Hex and the bias magnetic field Hb are parallel to each other.

  Referring to FIG. 5, detection element 10 (TMR element) has a linear region within the range of −Hk to Hk (Hk: saturation magnetic field) when there is no bias magnetic field Hb (broken line in FIG. 5). In the saturation region where the external magnetic field Hex is Hex ≦ −Hk or Hex ≧ Hk, the magnetization direction of the free layer and the magnetization direction of the pinned layer are parallel or antiparallel, and the element resistance R does not depend on the external magnetic field Hex. When the change amount of the element resistance R in the linear region of −Hk to Hk is ΔR, and the average value of the maximum value and the minimum value of the element resistance R is Rm, the maximum value of the element resistance R is expressed as Rm + ΔR / 2. The minimum value of the element resistance R is expressed as Rm−ΔR / 2. In order to obtain the largest resistance change ΔR, the magnetization direction of the pinned layer is parallel or antiparallel to the direction of the external magnetic field Hex, and the magnetization direction of the free layer when the external magnetic field Hex is 0 is the magnetization direction of the pinned layer. It is desirable to be vertical.

  Here, for example, when measuring the magnitude of the external magnetic field Hex, it is desirable that the magnitude of the external magnetic field Hex and the resistance value R, that is, the external magnetic field Hex and the detection signal are in a proportional relationship. Therefore, when measuring the magnitude of the external magnetic field Hex, a range (-Hk to Hk) in which the detection element 10 (TMR element) is a linear region is a measurable range. At this time, by applying the bias magnetic field Hb in a direction antiparallel to the external magnetic field Hex, the linear region of the detection element 10 (TMR element) moves to a range of (−Hk−Hb) to (+ Hk−Hb). . That is, the measurable range of the magnetic field detection device 1 is shifted by the bias magnetic field Hb.

  As described above, the magnetic field detection device 1 generates the bias magnetic field Hb by supplying the bias current Ib having an appropriate magnitude according to the fluctuation range of the external magnetic field Hex to be measured. On the other hand, a minute alternating current component can be detected.

  Next, a case where the direction of the external magnetic field Hex and the direction of the bias magnetic field Hb are perpendicular (when the direction of the external magnetic field Hex and the direction of the bias current Ib are parallel or anti-parallel) will be described. In this case, the bias magnetic field Hb functions to hold the magnetization vector of the free layer in the direction of the bias magnetic field Hb. That is, since the magnetization vector of the free layer is prevented from changing its direction by the bias magnetic field Hb, the response (sensitivity) of the magnetization vector of the free layer to the external magnetic field Hex is lowered. As a result, as the bias magnetic field Hb increases, the rate of change (dR / dHex: sensitivity) of the resistance value R of the detection element 10 (TMR element) with respect to the external magnetic field Hex decreases.

  FIG. 6 is a diagram illustrating the relationship between the external magnetic field Hex and the element resistance when the external magnetic field Hex and the bias magnetic field Hb are perpendicular to each other.

  Referring to FIG. 6, detection element 10 (TMR element) has a linear region within the range of −Hk to Hk (Hk: saturation magnetic field) when there is no bias magnetic field Hb (broken line in FIG. 6). On the other hand, when the bias magnetic field Hb is generated by the bias current Ib, the linear region of the detection element 10 (TMR element) is expanded from −Hkb to Hkb (Hkb: saturation magnetic field when the bias magnetic field Hb is received) (FIG. 6 solid line).

  As in the case of FIG. 5, when measuring the magnitude of the external magnetic field Hex, the range in which the detection element 10 (TMR element) is a linear region is the measurable range. Therefore, by applying the bias magnetic field Hb, the measurable range of the magnetic field detection device 1 is expanded by Hkb / Hk times.

  Thus, when the direction of the external magnetic field Hex and the direction of the bias magnetic field Hb are perpendicular, the magnetic field detection device is selected by selecting an appropriate bias magnetic field Hb according to the amount of fluctuation of the external magnetic field Hex to be measured. 1 can expand the measurement range and detect the external magnetic field Hex in a wider range.

  Next, when the direction of the external magnetic field Hex and the direction of the bias magnetic field Hb are perpendicular (when the direction of the external magnetic field Hex and the direction of the bias current Ib are parallel or antiparallel), and the free layer is saturated. explain. In this case, regardless of the magnitude of the external magnetic field, the resistance value of the detection element 10 (TMR element) is determined by the angle formed by the magnetization vector of the fixed layer and the magnetization vector of the free layer. That is, the resistance value R is expressed by equation (1) as an angle θ between the magnetization vector of the pinned layer and the magnetization vector of the free layer.

R = Rm + (ΔR / 2) × cos θ (1)
FIG. 7 is a diagram for explaining the relationship between the direction of the external magnetic field Hex and the bias magnetic field Hb and the magnetization direction.

  Referring to FIG. 7, the direction of magnetization vector Mp of the pinned layer is fixed in the Y-axis direction. Further, an external magnetic field Hex is applied in the Y-axis direction and a bias current is caused to flow in the Y-axis direction, whereby a bias magnetic field Hb in the X-axis direction is applied to the upper electrode 18 including the free layer. As a result, the direction of the magnetization vector Mf of the free layer coincides with the direction of the combined magnetic field H of the external magnetic field Hex and the bias magnetic field Hb. As a result, the element resistance R is determined by the angle θ formed by the magnetization vector Mp of the pinned layer and the magnetization vector Mf of the free layer as shown in the above equation (1).

  Here, if a magnetic field of a certain level or more is applied to the free layer by the bias magnetic field Hb as described above, the hysteresis of the element resistance R with respect to the magnetic field can be made extremely small. The reason for this is as follows.

  In general, hysteresis can be explained by magnetic domain generation / annihilation and domain wall movement. In a state where almost no magnetic field is applied, the formation of magnetic domains results in a hysteresis because the free energy of the system becomes smaller. On the other hand, if the spin of the free layer is set to a single magnetic domain as much as possible by applying a bias magnetic field Hb of a certain level or more, the magnetization process can be substantially only the rotation of the magnetization vector. As a result, hysteresis can be suppressed.

  The direction of the magnetization vector of the free layer is also affected by shape anisotropy. In the case of FIGS. 1 and 7, the shape of the upper electrode 18 including the free layer is a square for simplicity. On the other hand, the shape of the upper electrode 18 can be circular in order to suppress the influence of shape anisotropy.

  Or, conversely, the shape of the upper electrode 18 is rectangular, and the influence of shape anisotropy can be increased by making the long side considerably longer than the short side. As a result, the magnetization directions of the magnetic domains formed in the free layer are roughly aligned, so that the influence of hysteresis can be suppressed.

(External magnetic field detection procedure by the magnetic field detection device 1)
Hereinafter, a specific procedure for detecting the magnitude of the external magnetic field Hex by the magnetic field detection device 1 will be described. In the following example, the direction of the external magnetic field Hex and the direction of the bias magnetic field Hb are perpendicular (when the direction of the external magnetic field Hex and the direction of the bias current Ib are parallel or antiparallel).

  FIG. 8 is a diagram for explaining the operation of the magnetic field detection device 1 of FIG. FIG. 8 shows a magnetic field generator 32 for generating the bias magnetic field Hb. In the case of the first embodiment, the magnetic field generator 32 is the lower electrode 17 of the detection element 10. The magnetic field generator 32 generates a bias magnetic field Hb in the detection element 10. Even when a current line for supplying the bias current Ib is provided independently of the lower electrode 17 as the magnetic field generator 32, the external magnetic field Hex can be detected by the following procedure.

  Referring to FIG. 8, the direction of external magnetic field Hex is the X-axis direction, and the direction of bias magnetic field Hb is the X-axis direction. At this time, the direction of the bias current Ib is the Y-axis direction. The direction of the magnetization vector Mp of the pinned layer is set to the X-axis direction (parallel or antiparallel to the direction of the external magnetic field Hex). The direction of the magnetization vector Mf of the free layer is set to the Y-axis direction using shape anisotropy when neither the external magnetic field Hex nor the bias magnetic field Hb is applied. That is, the direction of the magnetization vector Mf of the free layer is set to be orthogonal to the direction of the magnetization vector Mp of the pinned layer.

  In principle, the unknown external magnetic field Hex can be measured by the following method if the magnetization direction of the free layer is an arbitrary fixed direction, for example, a 45 degree direction between the X-axis direction and the Y-axis direction. is there. However, as shown in the above equation (1), the magnetic tunnel resistance is determined by the cosine (cos θ) of the angle θ formed by the magnetization direction of the free layer and the magnetization direction of the pinned layer. Therefore, by making the magnetization direction of the free layer when the magnetic field is zero the Y-axis direction, the magnetization direction of the pinned layer and the magnetization direction of the free layer are orthogonal (θ = 90 °) to respond to the magnetic field. It is preferable because the property becomes almost linear and good.

  FIG. 9 is a flowchart showing a procedure for detecting the external magnetic field Hex by the magnetic field detection apparatus 1 of FIG. Hereinafter, the procedure for detecting the external magnetic field Hex will be described with reference to FIGS. It is assumed that the storage unit 27 of the control unit 25 stores measurement results obtained by measuring a plurality of known external magnetic fields Hex in the same procedure as described below.

  When neither the external magnetic field Hex nor the bias magnetic field Hb is applied at Step S101 in FIG. 9 (Hex = 0, Hb = 0), the control unit 25 outputs the output voltage Vout (1) of the differential amplifier circuit 23. Is A / D (Analog to Digital) converted and stored in the storage unit 27.

In the next step S102, an unknown external magnetic field Hex is applied to the magnetic field detection device 1.
In the next step S103, the control unit 25 determines an initial value of the bias current Ib based on the output voltage Vout (2) of the differential amplifier circuit 23 at this time. Specifically, the control unit 25 selects, as an initial value, the value of the bias current Ib set when a similar output voltage is obtained from the measurement results for known external magnetic fields stored in the storage unit 27. To do.

  In the next step S <b> 104, the control unit 25 supplies the initial value of the bias current Ib determined in step S <b> 103 by the current source 31 to the lower electrode 17. As a result, a bias magnetic field Hb is generated. The control unit 25 performs A / D conversion on the output voltage Vout (3) of the differential amplifier circuit 23 at this time and stores it in the storage unit 27.

  In the next step S104, the control unit 25 determines whether or not the absolute value of the difference between the output voltage Vout (1) stored in step S101 and the output voltage Vout (3) stored in step S104 is within a predetermined threshold value. Determine. If the predetermined threshold is exceeded (NO in step S105), the process proceeds to step S106. In step S106, the control unit 25 changes the value of the bias current Ib so that the absolute value of the difference between the output voltage Vout (1) and the output voltage Vout (3) becomes small. Thereafter, steps S104 and S105 are executed again.

  On the other hand, when the absolute value of the difference between the output voltage Vout (1) and the output voltage Vout (3) is equal to or smaller than the predetermined threshold value (YES in step S105), the control unit 25 advances the process to step S107. In step S107, the control unit 25 calculates the magnitude of the external magnetic field Hex by multiplying the current value of the bias current Ib by a preset conversion coefficient K0.

  Here, the conversion coefficient K0 can be obtained by K0 = Hex0 / Ib0, where Ib0 is the value of the bias current Ib obtained when the same processing as described above is performed on the known external magnetic field Hex0. . Preferably, a plurality of bias currents Ib are respectively determined for a plurality of known external magnetic fields by the same procedure as described above, and a conversion coefficient obtained by a ratio between each external magnetic field and the corresponding bias current is stored in the storage unit 27 in advance. Remember. Then, the conversion coefficient to be actually used may be determined by selecting the case closest to the bias current Ib obtained for the unknown external magnetic field Hex. Alternatively, the conversion factor to be actually used may be determined by interpolating a plurality of conversion factors stored in the storage unit 27 based on the bias current obtained from the unknown external magnetic field Hex.

(Summary)
As described above, according to the magnetic field detection device 1 of the first embodiment, since the bias current Ib flows through the lower electrode 17 that is one electrode of the detection element 10 (TMR element), a separate bias current wiring layer is provided. Compared to the case, the bias magnetic field Hb can be applied to the detection element 10 (TMR element) with less power consumption. Further, by changing the magnitude of the bias magnetic field Hb in accordance with the external magnetic field Hex, the linear region of the detection element 10 (TMR element) can be shifted and the magnetic field sensitivity can be changed, thereby detecting the magnetic field. Accuracy can be improved.

[Variation 1 of Embodiment 1]
FIG. 10 is a diagram for explaining a method of detecting the external magnetic field Hex according to the first modification of the first embodiment. A magnetic field detection apparatus 1A of Modification 1 of FIG. 10 further includes a magnetic field generation unit 35 that applies a bias magnetic field Hb0 in the Y-axis direction in addition to the magnetic field generation unit 32 that applies the bias magnetic fields Hb1 and Hb2 in the X-axis direction. This is different from the magnetic field detection device 1 of FIG. In FIG. 10, the direction of the unknown external magnetic field Hex is the X-axis direction, and the direction of the magnetization vector Mp of the pinned layer is the X-axis direction (parallel or antiparallel to the direction of the external magnetic field Hex). The other configuration of the magnetic field detection device 1A of FIG. 10 is the same as that of the magnetic field detection device 1 of FIG. 8, and therefore, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  The magnetic field generator 35 can be realized, for example, by arranging a permanent magnet in the vicinity of the detection element 10 (TMR element). The bias magnetic field Hb0 by the magnetic field generator 35 is set to be equal to or higher than the saturation magnetic field Hk (see FIGS. 5 and 6) of the free layer. As described with reference to FIG. 7, since a single magnetic domain is formed by this, the hysteresis of the element resistance R can be made extremely small.

  In a state where the external magnetic field Hex is not applied, the magnetization direction Mf of the free layer and the magnetization direction Mp of the pinned layer are approximately orthogonal by applying the bias magnetic field Hb0. When the external magnetic field Hex is applied in this state, as described with reference to FIG. 7, the element resistance R is determined by the magnetization vector Mp of the fixed layer and the magnetization vector Mf of the free layer according to the above equation (1). It depends on the angle θ made. Therefore, if the angle θ is calculated from the measured element resistance R according to the equation (1), the magnitude of the external magnetic field Hex can be obtained by Hex = Hb0 / tan θ.

  In the first modification, the control unit 25 further changes the bias current Ib to two values in a state where the external magnetic field Hex is not applied, and thereby the + X direction and the −X direction (the magnetization direction Mp of the pinned layer). The known bias magnetic fields Hb1 and Hb2 are generated in parallel and anti-parallel to. And the control part 25 measures the element resistance corresponding to those bias magnetic fields Hb1 and Hb2. As a result, Rm and ΔR in the above equation (1) can be obtained.

  Subsequently, an unknown external magnetic field Hex is applied in a state where the bias current Ib does not flow. The control unit 25 measures the element resistance R at this time, and uses the measured element resistance R and the Rm and ΔR calculated when the bias current Ib is passed, to calculate the angle θ of the above-described equation (1). calculate. By using the calculated angle θ, the magnitude of the unknown external magnetic field can be measured with higher accuracy. In this case, since the measurement result is corrected by one detection element 10, the circuit area can be reduced. Further, since correction can be performed using the same element, for example, a change in sensitivity due to temperature can be corrected more accurately.

  FIG. 11 is a flowchart showing a procedure for detecting the external magnetic field Hex according to the first modification of the first embodiment. Hereinafter, a specific measurement procedure will be described with reference to FIG.

  In step S151, the control unit 25 applies a known bias magnetic field Hb0 in the + Y direction by the magnetic field generation unit 35. The bias magnetic field Hb0 is always applied during the measurement period of the following steps S152, S153, and S155.

  In the next step S152, the control unit 25 supplies a predetermined bias current Ib (1) to the detection element 10 by the current source 31. In a state where the combined magnetic field of the bias magnetic field Hb1 generated by the bias current Ib (1) and the bias magnetic field Hb0 is applied to the detection element 10, the control unit 25 outputs the output voltage Vout ( 1) is A / D converted and stored in the storage unit 27.

  In the next step S153, the control unit 25 supplies the bias current Ib (2) having a magnitude different from that in step S152 to the detection element 10 by the current source 31. In a state where the combined magnetic field of the bias magnetic field Hb2 generated by the bias current Ib (2) and the bias magnetic field Hb0 is applied to the detection element 10, the control unit 25 outputs the output voltage Vout ( 2) is A / D converted and stored in the storage unit 27.

  In the next step S154, the calculation unit 26 of the control unit 25 calculates Rm and ΔR of the above-described equation (1) based on the output voltages Vout (1) and Vout (2). Specifically, first, the calculation unit 26 uses the output voltages Vout (1) and Vout (2), the resistance value of the resistance element 22, and the output voltage of the voltage source 21 to detect the detection element in the case of step S152. The element resistance R (1) of 10 and the element resistance R (2) of the detection element 10 in the case of step S153 are calculated. Next, the calculation unit 26 calculates the angle θ (referred to as θ1) in the above-described equation (1) in the case of Step S152 and the case of Step S153 from the magnitudes of the bias magnetic fields Hb1 and Hb2 and the magnitude of the bias magnetic field Hb0. The angle θ (referred to as θ2) in the equation (1) in FIG. And the calculating part 26 calculates Rm and (DELTA) R according to Formula (1) from calculated element resistance R (1), R (2) and angle (theta) 1, (theta) 2.

  In the next step S155, the control unit 25 outputs the output voltage Vout (3) of the differential amplifier circuit 23 when the unknown external magnetic field Hex is applied in a state where the bias current Ib is not supplied to the detection element 10. A / D converted and stored in the storage unit 27. During this time, a synthetic magnetic field of the bias magnetic field Hb0 and the unknown external magnetic field Hex is applied to the detection element 10.

  In the next step S156, the calculation unit 26 of the control unit 25 uses the Rm and ΔR calculated in step S154 and the output voltage Vout (3) measured in step S155 to determine the magnitude of the unknown external magnetic field Hex. calculate. Specifically, first, the calculation unit 26 uses the output voltage Vout (3), the resistance value of the resistance element 22, and the output voltage of the voltage source 21 to use the element resistance R ( 3) is calculated. Next, using the calculated element resistance R (3) and Rm and ΔR calculated in step S154, the calculation unit 26 calculates an angle θ (referred to as θ3) according to the equation (1). And the calculating part 26 calculates | requires the magnitude | size of the external magnetic field Hex by Hex = Hb0 / tan (theta) 3 using calculated angle | corner (theta) 3. In this way, it is possible to measure the external magnetic field Hex with more accurate sensitivity correction by temperature.

  As a method for generating the bias magnetic field Hb0, a permanent magnet as described in the first modification may be used, or a method in which a bias current is supplied using the lower electrode of the detection element 10 (TMR element) may be used. Alternatively, a method may be used in which a current is passed through a separately manufactured wiring.

  Further, as a method of generating the bias magnetic fields Hb1 and Hb2, a method of flowing the bias current Ib using the lower electrode of the detection element 10 as in Modification 1 may be used, or a method of using a movable permanent magnet. There may be.

[Modification 2 of Embodiment 1]
FIG. 12 is a cross-sectional view showing a configuration of the TMR element according to the second modification of the first embodiment. Referring to FIG. 12, the TMR element according to Modification 2 is different from the TMR element of FIG. 4 in that it includes a ferromagnetic layer 12A having a large coercive force instead of antiferromagnetic layer 12 of FIG. In other respects, the configuration of the TMR element in FIG. 12 is the same as the configuration of the TMR element in FIG. 4, and therefore, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  The magnetization direction of the ferromagnetic layer (fixed layer) 13 can be fixed in one direction also by providing the ferromagnetic layer 12A having a large coercive force adjacent to the ferromagnetic layer 12A as shown in FIG.

[Modification 3 of Embodiment 1]
FIG. 13 is a cross-sectional view showing a configuration of a TMR element according to the third modification of the first embodiment. Referring to FIG. 13, the TMR element according to Modification 3 includes a ferromagnetic layer (fixed layer) 13 shown in FIG. 4 by two ferromagnetic layers 13A and 13C and a nonmagnetic layer 13B sandwiched between them. This is different from the TMR element shown in FIG. In other respects, the configuration of the TMR element in FIG. 12 is the same as the configuration of the TMR element in FIG. 4, and therefore, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  In the pinned layer 13 of FIG. 13, the two ferromagnetic layers 13A and 13C stacked with the thin nonmagnetic layer 13B interposed therebetween are antiferromagnetically coupled to each other. The pinned layer 13 having such a structure is called a SAF (Synthetic Anti-Ferroelectric) structure, and can further stabilize the magnetization of the pinned layer 13. The nonmagnetic layer 13B can be formed using a nonmagnetic material such as Ru or Cu.

[Embodiment 2]
In the second embodiment, a TMR element is used as a reference element in addition to a detection element for detecting a magnetic field.

  When it can be considered that a bias magnetic field Hb larger than the external magnetic field Hex is applied, the direction of the bias magnetic field Hb and the direction of magnetization of the pinned layer are made parallel or antiparallel, thereby reducing the resistance of the TMR element to the minimum resistance Rmin. Alternatively, the maximum resistance Rmax can be fixed. Such a TMR element can be used in place of the resistance element 22 of FIG. 1 as a reference element. That is, a plurality of TMR elements having the same characteristics are prepared, some of which are used as detection elements that generate a resistance corresponding to the external magnetic field Hex, and other TMR elements are used as reference elements. Then, by obtaining the external magnetic field Hex from the difference between the resistance values of the detection element and the reference element, it is possible to accurately obtain the external magnetic field Hex by compensating for the change in the resistance value of the TMR element that changes depending on the ambient temperature. Hereinafter, a specific description will be given with reference to FIGS. 14 and 15.

  FIG. 14 is a plan view schematically showing the configuration of the magnetic field detection device 2 according to the second embodiment of the present invention.

  FIG. 15 is a perspective view schematically showing a configuration of a main part of the magnetic field detection device 2 of FIG.

  The magnetic field detection device 2 includes a reference element 50 that is a TMR element instead of the resistance element 22 of FIG. That is, the magnetic field detection device 2 includes a detection element 10 that detects a magnetic field, a voltage source 21, a reference element 50 that is used as a resistance element, a voltage amplification circuit 23A, a control unit 25A, and a current as a bias current supply unit. Sources 31, 33. Here, the voltage source 21 and the voltage amplification circuit 23 </ b> A constitute a measurement unit 20 </ b> A for measuring the resistance value of the detection element 10.

  The detection element 10 is a TMR element formed on the substrate 40, and includes an upper electrode 18 located at the upper part and a lower electrode 17 located at the lower part with the insulating layer 14 in between. As in the first embodiment, the upper electrode 18 includes a ferromagnetic layer (free layer), and the lower electrode 17 includes a ferromagnetic layer (fixed layer). The upper electrode 18 of the detection element 10 is connected to the wiring layer 43 through a conductive portion 46 formed in the contact hole. The lower electrode 17 of the detection element 10 is connected to the wiring layer 41 via a plurality of conductive portions 44 respectively formed in a plurality of contact holes, and has a plurality of conductive portions 45 formed respectively in the plurality of contact holes. Thus, the wiring layer 42 is connected. A large number of conductive portions 44 and 45 formed in the contact hole are provided in parallel in order to reduce parasitic resistance and make the current distribution on the lower electrode 17 uniform. The conductive portion 44 and the conductive portion 45 are provided on both sides in the Y-axis direction across the joint portion of the detection element 10. Since the detailed configuration of the joint of detection element 10 is the same as that of the first embodiment, description thereof will not be repeated.

  The reference element 50 is a TMR element formed on the substrate 40, and includes an upper electrode 58 positioned on the upper side and a lower electrode 57 positioned on the lower side with the insulating layer 54 interposed therebetween. Similar to the detection element 10, the upper electrode 58 includes a ferromagnetic layer (free layer), and the lower electrode 57 includes a ferromagnetic layer (fixed layer). The direction of the magnetization vector Mp of the pinned layer is fixed in the Y-axis direction. The upper electrode 58 of the reference element 50 is connected to the wiring layer 63 via a conductive portion 66 formed in the contact hole. The lower electrode 57 of the reference element 50 is connected to the wiring layer 61 through a plurality of conductive portions 64 formed in a plurality of contact holes, and has a plurality of conductive portions 65 formed in the plurality of contact holes, respectively. Thus, the wiring layer 62 is connected. A large number of conductive portions 64 and 65 formed in the contact hole are provided in parallel in order to reduce parasitic resistance and make the current distribution on the lower electrode 57 uniform. The conductive portion 64 and the conductive portion 65 are provided on both sides in the Y-axis direction across the joint portion of the reference element 50. Since the detailed configuration of the joint portion of reference element 50 is the same as that of detection element 10, description thereof will not be repeated.

  The wiring layer 43 of the detection element 10 and the wiring layer 63 of the reference element 50 are integrally formed. Thereby, the reference element 50 and the detection element 10 are electrically connected in series between the node Nd3 and the ground GND in this order.

  Further, as shown in FIG. 14, the lower electrodes 17 and 57 of the detection element 10 and the reference element 50 are formed so that the width of the lower electrode is narrow in the vicinity of the junction of the TMR element, and the other parts are wide. Is preferred. The reason for this is as follows.

  When measuring the resistance value of the TMR element, if the voltage drop due to the lower electrodes 17 and 57 becomes so large that it cannot be ignored as compared with the voltage drop due to the junction resistance, the measurement accuracy of the resistance value of the TMR element deteriorates. Therefore, it is necessary to reduce the resistance of the lower electrodes 17 and 57. For this reason, increasing the film thickness of the laminated film constituting the lower electrode increases the roughness of the laminated film. As a result, the roughness of the interface with the tunnel insulating film provided on the lower electrode is increased. For example, the MR ratio is decreased due to an increase in leakage current, or a shift to the magnetic field-resistance characteristic is caused by nail coupling. Alternatively, in the direction detection of the rotating magnetic field described later, there arises a problem that the deviation of the resistance characteristic of the TMR element from the sine curve becomes large.

  Therefore, it is necessary to increase the wiring width of the lower electrode in order to reduce the resistance of the lower electrodes 17 and 57. However, increasing the wiring width to the vicinity of the junction of the TMR element contributes to the formation of the bias magnetic field Hb. Since current components other than the current component immediately below the junction increase, it is not preferable. Therefore, the width of the lower electrode is narrow in the vicinity of the junction of the TMR element.

  Next, the configuration of the measurement unit 20A will be described. The voltage source 21 is connected between the wiring layer 62 and the wiring layer 42. Thereby, a constant voltage is applied to the reference element 50 and the detection element 10 connected in series. A Zener diode or the like may be used as means for applying the constant voltage.

  The input node of the voltage amplification circuit 23A is connected to the wiring layers 43 and 63 that are integrally formed. The voltage amplification circuit 23A amplifies the voltage Vd1 at the connection node Nd1 between the reference element 50 and the detection element 10 and outputs the amplified voltage Vd1 to the control unit 25 as the output voltage Vout. Similarly to the first embodiment, the voltage amplifier circuit 23A can be configured by a differential amplifier circuit and a reference voltage source. By configuring a half bridge composed of the detection element 10 and the reference element 50 in this way, the output voltage Vout having a magnitude corresponding to the resistance value between the upper electrode 18 and the lower electrode 17 of the detection element 10 is controlled by the control unit. To 25A.

  The control unit 25 </ b> A is configured by a computer and includes a calculation unit 26 and a storage unit 27. The computing unit 26 calculates the magnitude of the unknown external magnetic field based on the output voltage Vout of the voltage amplification circuit 23A. Since the specific calculation method is the same as that in the first embodiment, description thereof will not be repeated. The storage unit 27 stores the output voltage of the voltage amplification circuit 23A and the like. Further, the control unit 25A controls the operation of the voltage source 21 and the current sources 31, 33 and the like.

  The current source 31 is connected between the wiring layer 41 and the wiring layer 42. The current source 31 generates a bias magnetic field in the X-axis direction at the junction of the detection element 10 by flowing a bias current in the Y-axis direction through the lower electrode 17. The current source 33 is connected between the wiring layer 61 and the wiring layer 62. The current source 33 generates a bias magnetic field Hb in the Y-axis direction at the junction of the reference element 50 by flowing a bias current Ib in the X-axis direction through the lower electrode 57.

  The measurement unit 20A and the current sources 31 and 33 are preferably provided on the same substrate as the detection element 10 and the reference element 50 (TMR element) from the viewpoint of improving the influence of external noise and resistance to surge. Alternatively, it may be mounted in the form of a chip component on another substrate such as an epoxy resin substrate or a ceramic substrate and electrically connected, for example, by wire bonding.

  Next, the operation of the magnetic field detection device 2 will be described. When the external magnetic field Hex changes, the magnetization direction of the free layer changes and the angle formed with the magnetization direction of the pinned layer changes, so that the resistance of the detection element 10 changes. At this time, a bias current is supplied to the lower electrode 17 so that the detection element 10 generates a bias magnetic field of about 10 Oe, for example. As described in the first embodiment, the bias magnetic field has effects such as hysteresis reduction.

  On the other hand, a bias current Ib in the X-axis direction is supplied to the lower electrode 57 of the reference element 50, and a magnetic field of, for example, 100 Oe is generated. As a result, the reference element 50 is used as a reference resistance so that the magnetization direction of the free layer of the reference element 50 is always kept substantially constant with respect to the magnetization direction of the pinned layer regardless of the external magnetic field. Regarding the resistance of the TMR element, the angle θ between the magnetization direction of the pinned layer and the magnetization direction of the free layer has the relationship of the above-described equation (1). It is preferable to be parallel or antiparallel to the surface. As a result, the resistance of the reference element 50 exhibits the maximum resistance or the minimum resistance of the TMR element, and is thus less susceptible to the influence of an external magnetic field. For this reason, in the second embodiment, the magnetization direction Mp of the lower electrode 57 of the reference element 50 is set to the Y-axis direction. By using the reference element 50, it is possible to accurately determine the external magnetic field Hex by compensating for the change in the resistance value of the TMR element that varies depending on the ambient temperature.

[Modification of Embodiment 2]
FIG. 16 is a plan view schematically showing a configuration of a magnetic field detection device 2A according to a modification of the second embodiment of the present invention.

  FIG. 17 is a perspective view schematically showing a configuration of a main part of the magnetic field detection device 2A of FIG. 16 and 17, the magnetic field detection device 2 </ b> A includes a wiring layer 47 connected to the lower electrode 17 near the joint of the detection element 10 via a plurality of conductive parts 48, and a lower part near the joint of the reference element 50. 14 and 14 differs from the magnetic field detection device 2 in that it further includes a wiring layer 67 connected to the electrode 57 via a plurality of conductive portions 68. Further, in the magnetic field detection device 2, the voltage source 21 is connected between the wiring layers 42 and 62, whereas in the magnetic field detection device 2A, the voltage source 21 is connected between the wiring layers 47 and 67. Also in this point, the magnetic field detection device 2A of the modified example is different from the magnetic field detection device 2. In other respects, magnetic field detection device 2A is similar to magnetic field detection device 2 in FIGS. 14 and 14, and therefore the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  As shown in FIGS. 16 and 16, in this modification, voltage detection is performed near the junction of the lower electrodes 17 and 57, that is, near the midpoint of the conductive portions 44 and 45 and near the midpoint of the conductive portions 64 and 65. Wiring layers 47 and 48 are further provided. Thereby, the influence of the voltage drop due to the resistance of the lower electrodes 17 and 57 can be suppressed, and the junction resistance of the TMR element can be measured more precisely.

[Embodiment 3]
FIG. 18 is a plan view schematically showing the configuration of the magnetic field detection device 3 according to the third embodiment of the present invention. The magnetic field detection device 3 according to the third embodiment has a bridge formed by two detection elements 10A and 10B and two reference elements 50A and 50B.

  Referring to FIG. 18, the magnetic field detection device 3 includes detection elements 10A and 10B that detect a magnetic field, reference elements 50A and 50B used as resistance elements, voltage sources 21A and 21B, a differential amplifier circuit 23, A control unit 25B and current sources 31A, 31B, 33A, and 33B as bias current supply units are included. Here, the voltage sources 21A and 21B and the differential amplifier circuit 23 constitute a measurement unit 20A for measuring the resistance values of the detection elements 10A and 10B.

  The detection element 10A is a TMR element formed on a substrate, and includes an upper electrode 18A located at the upper part and a lower electrode 17A located at the lower part with the insulating layer 14A interposed therebetween. The detection element 10B is a TMR element formed on a substrate, and includes an upper electrode 18B located at the upper part and a lower electrode 17B located at the lower part with the insulating layer 14B interposed therebetween. As in the case of the first embodiment, the upper electrodes 18A and 18B include a ferromagnetic layer (free layer), and the lower electrodes 17A and 17B include a ferromagnetic layer (fixed layer). Since the detailed configuration of the joint portion of detection elements 10A and 10B is the same as that of the first embodiment, description thereof will not be repeated.

  The reference element 50A is a TMR element formed on a substrate, and includes an upper electrode 58A located on the upper side and a lower electrode 57A located on the lower side with the insulating layer 54A interposed therebetween. The reference element 50B is a TMR element formed on a substrate, and includes an upper electrode 58B positioned at the upper part and a lower electrode 57B positioned at the lower part with the insulating layer 54B interposed therebetween. Similar to the detection elements 10A and B, the upper electrodes 58A and 58B include a ferromagnetic layer (free layer), and the lower electrodes 57A and 57B include a ferromagnetic layer (fixed layer). Since the detailed configuration of the joint portion of reference elements 50A and 50B is the same as that of detection elements 10A and 10B, description thereof will not be repeated.

  The upper electrode 18A of the detection element 10A and the upper electrode 58A of the reference element 50A are connected to the connection node Nd1. Thus, reference element 50A and detection element 10A are electrically connected in series between node Nd3 and ground GND in this order. The potential Vd1 of the connection node Nd1 is input to the − terminal of the differential amplifier circuit 23.

  The upper electrode 18B of the detection element 10B and the upper electrode 58B of the reference element 50B are connected to the connection node Nd2. Thus, reference element 50B and detection element 10B are electrically connected in series between node Nd4 and ground GND in this order. The potential Vd2 of the connection node Nd2 is input to the + terminal of the differential amplifier circuit 23. The differential amplifier circuit 23 amplifies the potential difference between the connection nodes Nd1 and Nd2 and outputs the amplified difference to the control unit 25B.

  The voltage source 21A is connected to one end of the lower electrode 57A of the reference element 50A and one end of the lower electrode 17A of the detection element 10A. Thereby, a constant voltage is applied to the reference element 50A and the detection element 10A connected in series. The voltage source 21B is connected to one end of the lower electrode 57B of the reference element 50B and one end of the lower electrode 17B of the detection element 10B. Thereby, a constant voltage is applied to the reference element 50B and the detection element 10B connected in series.

  The current sources 31A and 31B are connected to both ends of the lower electrodes 17A and 17B of the detection elements 10A and 10B, respectively, and supply a bias current in the Y-axis direction to the lower electrodes 17A and 17B. As a result, a bias magnetic field in the X-axis direction is generated at the junction between the detection elements 10A and 10B. The current sources 33A and 33B are connected to both ends of the lower electrodes 57A and 57B of the reference elements 50A and 50B, respectively, and supply a bias current in the X-axis direction to the lower electrodes 57A and 57B. As a result, a bias magnetic field in the Y-axis direction is generated at the junction between the reference elements 50A and 50B.

  The control unit 25B is configured by a computer and includes a calculation unit 26 and a storage unit 27. The computing unit 26 calculates the magnitude of the unknown external magnetic field based on the output voltage Vout of the differential amplifier circuit 23. A specific calculation method will be described later with reference to FIGS. The storage unit 27 stores the output of the differential amplifier circuit 23 and the like. Further, the control unit 25A controls operations of the voltage sources 21A and 21B and the current sources 31A, 31B, 33A and 33B.

  FIG. 19 is a diagram for explaining the operation of the magnetic field detection device 3 of FIG. FIG. 19 shows magnetic field generators 32A, 32B, 34A, 34B for generating the bias magnetic field Hb. In the third embodiment, the magnetic field generators 32A and 32B are the lower electrodes 17A and 17B of the detection elements 10A and 10B, respectively. The magnetic field generators 34A and 34B are the lower electrodes 57A and 57B of the reference elements 50A and 50B, respectively. Bias magnetic field Hb is generated in TMR elements 10A, 10B, 50A, and 50B by magnetic field generators 32A, 32B, 34A, and 34B, respectively.

  When the current lines for supplying the bias current Ib are provided in the vicinity of the junction by Al wiring or the like as the magnetic field generators 32A, 32B, 34A, 34B without using the lower electrodes 17A, 17B, 57A, 57B. However, the external magnetic field Hex can be detected by the following procedure.

  In the case of FIG. 19, the direction of the external magnetic field Hex is the X-axis direction, and the direction of the bias magnetic field Hb of the detection elements 10A and 10B is also the X-axis direction. At this time, the direction of the bias current Ib supplied to the detection elements 10A and 10B is the Y-axis direction. The direction of the bias magnetic field Hb of the reference elements 50A and 50B is the Y-axis direction, and the direction of the bias current Ib supplied to the reference elements 50A and 50B at this time is the X-axis direction.

  Furthermore, the direction of the magnetization vector Mp of the pinned layer of the detection elements 10A and 10B is defined as the X direction, and the direction of the magnetization vector Mp of the pinned layer of the reference elements 50A and 50B is defined as the Y direction. When neither the external magnetic field Hex nor the bias magnetic field Hb is applied, the direction of the magnetization vector Mp of the free layer of the detection elements 10A and 10B is the Y direction, and the magnetization vector Mp of the free layer of the reference elements 50A and 50B Let the direction be the Y direction. By flowing a bias current Ib to the lower electrodes 57A and 57B by the current sources 33A and 33B, the magnetization direction of the free layer of the reference elements 50A and 50B is the same as the magnetization direction of the pinned layer when the external magnetic field Hex is not applied. Parallel or anti-parallel to it.

  FIG. 20 is a flowchart showing a procedure for detecting the external magnetic field Hex by the magnetic field detection device 3 of FIGS. 18 and 19. Hereinafter, the procedure for detecting the external magnetic field Hex will be described with reference to FIGS. 19 and 20.

  In step S201 in FIG. 20, the control unit 25B causes the current sources 33A and 33B to pass a bias current Ib through the lower electrodes of the reference elements 50A and 50B through 57A and 57B. Thus, a sufficiently large bias magnetic field Hb (for example, 100 Oe) is generated in the reference elements 50A and 50B, and the magnetization directions of the free layer and the fixed layer of the reference elements 50A and 50B are fixed in antiparallel.

  In the next step S202, the control unit 25B causes a bias current Ib to flow through the lower electrodes 17A and 17B of the detection elements 10A and 10B by the current sources 31A and 31B. Thereby, a sufficiently large bias magnetic field Hb (for example, 100 Oe) is generated in the detection elements 10A and 10B, and the magnetization directions of the free layer and the fixed layer of the detection elements 10A and 10B are made antiparallel.

  In the next step S203, the storage unit 27 of the control unit 25B stores the output voltage Vout of the differential amplifier circuit 23. The output voltage Vout at this time is the minimum output voltage Vmin. Further, the storage unit 27 stores a voltage slightly larger than the minimum output voltage Vmin as the minimum measurement voltage VLL. The minimum measurement voltage VLL is the lower limit output voltage Vout when the external magnetic field Hex is measured in the linear region of the TMR element.

  In the next step S204, the control unit 25B causes a bias current Ib to flow through the lower electrodes 17A and 17B of the detection elements 10A and 10B by the current sources 31A and 31B. Thereby, a sufficiently large bias magnetic field Hb (for example, 100 Oe) is generated in the detection elements 10A and 10B, and the magnetization directions of the free layer and the fixed layer of the detection elements 10A and 10B are made parallel.

  In the next step S205, the storage unit 27 of the control unit 25B stores the output voltage Vout of the differential amplifier circuit 23. The output voltage Vout at this time is the maximum output voltage Vmax. Further, the storage unit 27 stores a voltage slightly smaller than the maximum output voltage Vmax as the maximum measured voltage VHL. The maximum measurement voltage VHL is the upper limit output voltage Vout when the external magnetic field Hex is measured in the linear region of the TMR element. Preferably, the minimum measurement voltage VLL and the maximum measurement voltage VHL can be determined by recording the output voltage Vout of the differential amplifier circuit 23 while gradually changing the bias current Ib.

In the next step S206, a known external magnetic field Hex is applied to the magnetic field detection device 3.
In the next step S207, the control unit 25B acquires the output voltage Vout of the differential amplifier circuit 23 while changing the bias current Ib supplied to the detection elements 10A and 10B by the current sources 31A and 31B. Then, the control unit 25B searches for an optimal setting value of the bias current Ib in which the output voltage Vout is between the minimum measurement voltage VLL and the maximum measurement voltage VHL. When the output voltage Vout is between the minimum measurement voltage VLL and the maximum measurement voltage VHL, the detection elements 10A and 10B are operating in the linear region.

  In the next step S208, the storage unit 27 of the control unit 25B stores the set value of the appropriate bias current Ib searched in step S207 in association with the external magnetic field Hex at that time. Further, the storage unit 27 stores magnetic field sensitivity (Hex / Vout) calculated from the output voltage Vout obtained with the external magnetic field Hex and the bias current Ib.

  The above steps S206 to S208 are repeatedly executed for a predetermined number of known external magnetic fields Hex (NO in step S209). When the above measurement for a predetermined number of known external magnetic fields Hex is completed (YES in step S209), the process proceeds to step S210.

In step S210, an unknown external magnetic field Hex is applied to the magnetic field detection device 3.
In the next step S211, the control unit 25B supplies the smallest set value of the bias current Ib stored in the storage unit 27 by the current sources 31A and 31B to the detection elements 10A and 10B. Then, the output voltage Vout of the differential amplifier circuit 23 at that time is acquired.

  In next step S212, the control unit 25B determines whether or not the acquired output voltage Vout is in a linear region between the minimum measurement voltage VLL and the maximum measurement voltage VHL. If the output voltage Vout is not in the linear region (NO in step S212), the setting value is changed to another bias current Ib in step S213, and steps S211 and S212 are executed again. On the other hand, if the output voltage Vout is in the linear region (YES in step S212), the process proceeds to step S214.

  In step S214, the calculation unit 26 of the control unit 25B calculates the magnitude of the external magnetic field Hex from the output voltage Vout using the magnetic field sensitivity corresponding to the current setting value of the bias current Ib.

  In the next step S215, after the external magnetic field Hex is detected in S214, the control unit 25B is applied to the lower electrodes 17A and 17B of the detection elements 10A and 10B by the current sources 31A and 31B in a state where the external magnetic field Hex is not applied. A bias current Ib is supplied. Thereby, a sufficiently large bias magnetic field Hb (for example, 100 Oe) is generated in the detection elements 10A and 10B, and the magnetization directions of the free layer and the fixed layer of the detection elements 10A and 10B are made antiparallel.

  In the next step S216, the storage unit 27 of the control unit 25B stores the output voltage Vout of the differential amplifier circuit 23. The output voltage Vout at this time is the minimum output voltage Vmin.

  In the next step S217, the control unit 25B causes a bias current Ib to flow through the lower electrodes 17A and 17B of the detection elements 10A and 10B by the current sources 31A and 31B. Thereby, a sufficiently large bias magnetic field Hb (for example, 100 Oe) is generated in the detection elements 10A and 10B, and the magnetization directions of the free layer and the fixed layer of the detection elements 10A and 10B are made parallel.

  In the next step S218, the storage unit 27 of the control unit 25B stores the output voltage Vout of the differential amplifier circuit 23. The output voltage Vout at this time is the maximum output voltage Vmax.

  In the next step S219, the calculation unit 26, the minimum output voltage Vmin (1) in step S203, the maximum output voltage Vmax (1) in step S204, the minimum output voltage Vmin (2) in step S216, and the maximum output in step S218. Temperature correction of the magnitude of the unknown external magnetic field Hex calculated in step S214 is performed using the voltage Vmax (2). Specifically, the calculation unit 26 multiplies the external magnetic field Hex in step S214 by (Vmax (2) −Vmin (2)) / (Vmax (1) −Vmin (1)) to obtain a final temperature correction. The subsequent external magnetic field Hex is calculated. Thus, detection of the unknown external magnetic field Hex is completed.

  By the above procedure, a magnetic field can be measured with good accuracy in a wide magnetic field range. It is also possible to correct changes in sensitivity due to temperature. Further, according to the above detection procedure, a magnetic field in which the direction of application of the magnetic field is approximately constant can be measured with high sensitivity, and therefore, for example, the magnetic field detection device 3 can be used as a direct current and alternating current sensor. . Preferably, the bias current Ib supplied from the current sources 31A, 31B, 33A, and 33B is flowed immediately before obtaining the output voltage Vout of the differential amplifier circuit 23, and is cut off after obtaining the output voltage Vout. The power consumption of the detection device 3 can be further reduced. In the reference elements 50A and 50B described above, the magnetization directions of the free layer and the pinned layer are antiparallel, but may be set parallel to each other.

[Modification 1 of Embodiment 3]
FIG. 21 is a plan view schematically showing a configuration of a magnetic field detection device 3A according to the first modification of the third embodiment of the present invention. The magnetic field detection device 3A in FIG. 21 is different from the magnetic field detection device 3 in FIG. 18 in that the voltage source 21B is not included. In the magnetic field detection device 3A, the node Nd3 and the node Nd4 are connected to apply a constant voltage to the detection element 10B and the reference element 50B connected in series by the voltage source 21A. The operation of the voltage source 21A is controlled by the control unit 25C. The magnetic field detection device 3 </ b> A according to the modified example configured as described above has the same effects as the magnetic field detection device 3. In other respects, magnetic field detection device 3A in FIG. 21 is similar to magnetic field detection device 3 in FIG. 18, and therefore the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

[Modification 2 of Embodiment 3]
FIG. 22 is a diagram for explaining the configuration and operation of a magnetic field detection device 3B according to the second modification of the third embodiment of the present invention. The magnetic field detection device 3B of FIG. 22 differs from the magnetic field detection device 3 of FIG. 19 in that the detection elements 50A and 50B are arranged at positions rotated 90 degrees clockwise from the case of FIG.

  That is, in the case of FIG. 22, the direction of the bias magnetic field Hb of the reference elements 50A and 50B is the X-axis direction, and the direction of the bias current Ib supplied to the reference elements 50A and 50B at this time is the Y-axis direction. Furthermore, when the direction of the magnetization vector Mp of the fixed layer of the reference elements 50A and 50B is the + X direction and neither the external magnetic field Hex nor the bias magnetic field Hb is applied, the magnetization vector Mf of the free layer of the reference elements 50A and 50B Let the direction be -X direction. By flowing a sufficiently large bias current Ib to the lower electrodes 57A and 57B of the reference elements 50A and 50B by the current sources 33A and 33B, the magnetization direction of the free layers of the reference elements 50A and 50B is relative to the magnetization direction of the pinned layer. Parallel or antiparallel. In other respects, the time detection device 3B in FIG. 22 is common to the magnetic field detection device 3 in FIGS. 18 and 19, and therefore, the same or corresponding parts are denoted by the same reference numerals and description thereof is not repeated.

  In general, in order to align the magnetization directions of the magnetic domains in one direction in the fixed layer of the TMR element, the chip on which the fixed layer is formed is annealed while applying a magnetic field. In the case of the magnetic field detection device 3 of FIG. 19, the direction of the magnetization vector Mp of the fixed layer of the reference elements 50A and 50B is different from the direction of the magnetization vector Mp of the fixed layer of the detection elements 10A and 10B. For this reason, it is necessary to mount the detection elements 10A and 10B and the reference elements 50A and 50B as separate magnetic chips after mounting them on separate chips.

  On the other hand, in the magnetic field detection device 3B according to the second modification, the direction of the magnetization vector Mp of the fixed layer of the reference elements 50A and 50B and the direction of the magnetization vector Mp of the fixed layer of the detection elements 10A and 10B Are in the same X-axis direction. Therefore, the reference elements 50A and 50B and the detection elements 10A and 10B can be easily formed on the same substrate.

[Embodiment 4]
In the first to third embodiments, the output current of the current source is variable. In the fourth embodiment, a constant current is supplied from the current source 31, and the detection elements 10 (1), 10 (2), and 10 (3) (referred to collectively as the detection element 10) by resistors provided in the current path. Also, the amount of bias current to be supplied is changed. As a result, a relative magnetic field sensitivity shift can be reduced.

  FIG. 23 is a plan view schematically showing the configuration of the magnetic field detection device 4 according to the fourth embodiment of the present invention. The magnetic field detection device 4 in FIG. 23 corresponds to the magnetic field detection device 2 in FIG. 14, and is an example in which a half bridge circuit is configured by the detection element 10 and the reference element 50.

  Referring to FIG. 23, magnetic field detection device 2 includes detection elements 10 (1), 10 (2), and 10 (3) that detect magnetic fields, resistance elements R 1 to R 6, voltage source 21, and resistance elements. A reference element 50, a differential amplifier circuit 23, a reference voltage source 24, a control unit 25D, and current sources 31 and 33 as bias current supply units are used. Here, the voltage source 21, the differential amplifier circuit 23, and the reference voltage source 24 constitute a measuring unit 20A for measuring the resistance value of the detecting element 10. The detailed configurations of detection elements 10 (1), 10 (2), 10 (3) and reference element 50 are the same as those in the first to third embodiments described above, and therefore description thereof will not be repeated.

  As shown in FIG. 23, one end of the lower electrode 17 (1) of the detection element 10 (1) is connected to the node Nd5, and the other end is connected to the ground node GND via the subordinately connected resistance elements R1 to R3. Is done. One end of the lower electrode 17 (2) of the detection element 10 (2) is connected to the node Nd5, and the other end is connected to the ground node GND via the cascaded resistance elements R4 and R5. One end of the lower electrode 17 (3) of the detection element 10 (3) is connected to the node Nd5, and the other end is connected to the ground node GND via the resistance element R6. Current source 31 is connected between node Nd5 and ground node GND. Therefore, when a constant current is supplied from the current source 31, different bias currents flow through the detection elements 10 (1), 10 (2), and 10 (3).

  On the other hand, the upper electrodes 18 (1), 18 (2), and 18 (3) of the detection elements 10 (1), 10 (2), and 10 (3) are connected to the node Nd 1 through the switch 71. The node Nd1 is connected to the upper electrode 58 of the reference element 50. The voltage source 21 is connected between one end (node Nd3) of the lower electrode 57 of the reference element 50 and the node Nd5. In this case, by switching the switch 71, a constant voltage is applied from the voltage source 21 to any one of the detection elements 10 (1), 10 (2), and 10 (3) and the detection element 50. Switching of the switch 71 is controlled by the control unit 25D.

  The differential amplifier circuit 23 amplifies the difference voltage between the voltage Vd1 at the node Nd1 and the reference voltage Vref output from the reference voltage source 24, and outputs the amplified voltage to the control unit 25D as the output voltage Vout. The control unit 25D detects the external magnetic field Hex based on the output voltage Vout. Since the procedure for detecting external magnetic field Hex is the same as that in the first embodiment, description thereof will not be repeated.

  Here, as the resistance elements R1 to R6, off-the-shelf resistance elements may be externally attached, or the resistance elements may be formed in the substrate. Alternatively, the lower electrode 17 may be manufactured to have different lengths and widths to replace the resistance element. When the resistance is increased by increasing the length of the lower electrode 17, the length of the lower electrode 17 on the ground node GND side opposite to the node Nd5 to which the voltage source 21 is connected is increased. . This is because the parasitic resistance at the time of measuring the element resistance is not increased.

  FIG. 24 is a diagram for explaining the operation of the magnetic field detection apparatus 4A according to the fourth embodiment of the present invention. A magnetic field detection device 4A in FIG. 24 corresponds to the magnetic field detection device 3 in FIGS. 18 and 19, and includes detection elements 10A (1) to 10A (3), 10B (1) to 10B (3) and a reference element. This is an example in which a full bridge circuit is configured by 50A and 50B. Hereinafter, the detection elements 10A (1) to 10A (3) are collectively referred to as the detection element 10A, and the detection elements 10B (1) to 10B (3) are collectively referred to as the detection element 10B.

  The magnetic field detection device 4A of FIG. 24 includes magnetic field generation units 32A (1) to 32A (3) connected in parallel instead of the magnetic field generation unit 32A of FIG. 19, and includes magnetic fields connected in parallel instead of the magnetic field generation unit 32B. The generators 32B (1) to 32B (3) are included. Further, the magnetic field detection device 4A includes detection elements 10A (1) to 10A (3) connected in parallel instead of the detection element 10A of FIG. 19, and includes detection elements 10B (1) connected in parallel instead of the detection element 10B. ) -10B (3). The detection elements 10A (1) to 10A (3), 10B (1) to 10B (3) are generated by the magnetic field generators 32A (1) to 32A (3) and 32B (1) to 32B (3), respectively. A bias magnetic field Hb is received.

  Further, the voltage at the junction of the detection elements 10A (1) to 10A (3) is switched to the switch 71A and applied to the negative terminal of the differential amplifier circuit 23. The voltage at the junction of the detection elements 10B (1) to 10B (3) is switched to the switch 71B and applied to the + terminal of the differential amplifier circuit 23. Switching of the switches 71A and 71B is controlled by the control unit 25E. The other configuration of magnetic field detection device 4A in FIG. 24 is the same as that of magnetic field detection device 3 in FIG. 19, and therefore, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 25 is a flowchart showing a procedure for detecting the external magnetic field Hex by the magnetic field detection device 4A of FIG. Hereinafter, the procedure for detecting the external magnetic field Hex will be described with reference to FIGS. 24 and 25. Note that the flowchart of FIG. 25 is obtained by changing some of the steps in the flowchart of FIG. 20, and therefore, a detailed description of common parts will not be repeated.

  In step S201 of FIG. 25, the control unit 25E causes a sufficiently large bias current Ib to flow through the lower electrodes of the reference elements 50A and 50B by the current sources 33A and 33B. Thereby, the magnetization directions of the free layer and the fixed layer of the reference elements 50A and 50B are fixed in antiparallel.

  In the next step S202, the control unit 25E switches the switches 71A and 71B to flow the bias current Ib to the lower electrodes of the detection elements 10A (3) and 10B (3) where the bias current becomes the largest. Thereby, the magnetization directions of the free layer and the fixed layer of the detection elements 10A and 10B are made antiparallel.

  In the next step S203, the storage unit 27 of the control unit 25E stores the minimum output voltage Vmin and the minimum measured voltage VLL.

  In the next step S204, the control unit 25E supplies a reverse bias current Ib to the lower electrodes of the detection elements 10A (3) and 10B (3) by the current sources 31A and 31B. Thereby, the magnetization directions of the free layers and the fixed layers of the detection elements 10A and 10B are made parallel.

  In the next step S205, the storage unit 27 of the control unit 25E stores the maximum output voltage Vmax and the maximum measured voltage VHL.

In the next step S206, a known external magnetic field Hex is applied to the magnetic field detection device 3.
In the next step S207A, the control unit 25E acquires the output voltage Vout of the differential amplifier circuit 23 while switching the switches 71A and 71B. Then, the control unit 25E searches for a switch switching condition such that the output voltage Vout is between the minimum measurement voltage VLL and the maximum measurement voltage VHL.

  In the next step S208A, the storage unit 27 of the control unit 25E stores the switch switching condition searched in step S207A in association with the external magnetic field Hex at that time. Further, the storage unit 27 stores the magnetic field sensitivity (Hex / Vout) calculated from the external magnetic field Hex and the output voltage Vout obtained under the switch switching condition.

  The above steps S206 to S208 are repeatedly executed for a predetermined number of known external magnetic fields Hex (NO in step S209). When the above measurement for a predetermined number of known external magnetic fields Hex is completed (YES in step S209), the process proceeds to step S210.

In step S210, an unknown external magnetic field Hex is applied to the magnetic field detection device 3.
In the next step S211A, the control unit 25E causes the switches 71A and 71B to bias the detection elements 10A (1) and 10B (1) that have the smallest bias current among the switch switching conditions stored in the storage unit 27. Switch the current supply. Then, the output voltage Vout of the differential amplifier circuit 23 at that time is acquired.

  In next step S212, the control unit 25E determines whether or not the acquired output voltage Vout is in a linear region between the minimum measurement voltage VLL and the maximum measurement voltage VHL. If the output voltage Vout is not in the linear region (NO in step S212), the switch is switched in step S213A, and steps S211 and S212 are executed again. On the other hand, if the output voltage Vout is in the linear region (YES in step S212), the process proceeds to step S214.

  In step S214, the calculation unit 26 of the control unit 25E calculates the magnitude of the external magnetic field Hex from the output voltage Vout using the magnetic field sensitivity corresponding to the current switch switching condition.

  In the next step S215, after the external magnetic field Hex is detected in S214, the control unit 25E uses the current sources 31A and 31B to detect the detection elements 10A (3) and 10B (3) in a state where the external magnetic field Hex is not applied. A bias current Ib is passed through the lower electrode. Thereby, the magnetization directions of the free layer and the fixed layer of the detection elements 10A and 10B are made antiparallel.

  In the next step S216, the storage unit 27 of the control unit 25E stores the minimum output voltage Vmin.

  In the next step S217, the control unit 25E causes the bias current Ib to flow through the lower electrodes of the detection elements 10A (3) and 10B (3) by the current sources 31A and 31B. Thereby, the magnetization directions of the free layers and the fixed layers of the detection elements 10A and 10B are made parallel.

  In the next step S218, the storage unit 27 of the control unit 25E stores the maximum output voltage Vmax.

  In the next step S219, the calculation unit 26, the minimum output voltage Vmin (1) in step S203, the maximum output voltage Vmax (1) in step S204, the minimum output voltage Vmin (2) in step S216, and the maximum output in step S218. Temperature correction of the magnitude of the unknown external magnetic field Hex calculated in step S214 is performed using the voltage Vmax (2). Thus, detection of the unknown external magnetic field Hex is completed.

  With the above procedure, the magnetic field can be measured with a better accuracy than in the case of Embodiment 3 in a wide magnetic field range. Further, as in the case of the third embodiment, a change in sensitivity due to temperature can be corrected.

[Embodiment 5]
The magnetic field detection device 5 according to the fifth embodiment detects the direction of the in-substrate component of the external magnetic field Hex.

  FIG. 26 is a plan view schematically showing the configuration of the magnetic field detection device 5 according to the fifth embodiment of the present invention. The magnetic field detection device 5 in FIG. 26 differs from the magnetic field detection device 3 in FIG. 18 in that detection elements 10C and 10D are provided in place of the reference elements 50A and 50B in FIG. In the magnetic field detection device 5 of FIG. 26, the direction of the magnetization vector Mp of the fixed layer of the detection element 10A is the −X direction, and the direction of the magnetization vector Mp of the fixed layer of the detection element 10B is the + X direction. In the magnetic field detection device 5 of FIG. 26, the direction of the magnetization vector Mp of the fixed layer of the detection element 10C is the + Y direction, and the direction of the magnetization vector Mp of the fixed layer of the detection element 10B is the -Y direction. The control unit 25F detects the direction of the external magnetic field based on the element resistances of these four detection elements 10A to 10D. Since the configuration of other magnetic field detection devices 5 is the same as the configuration of magnetic field detection device 3 in FIG. 18, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 27 is a flowchart showing a procedure for detecting the direction of the external magnetic field Hex by the magnetic field detection device 5 of FIG.

  Referring to FIGS. 26 and 27, in step S301, control unit 25F causes sufficiently large bias current Ib to flow through lower electrodes 17A and 17B of detection elements 10A and 10B by current sources 31A and 31B. Thereby, the magnetization directions of the free layers and the fixed layers of the detection elements 10A and 10B are made parallel. Further, the control unit 25F causes a sufficiently large bias current Ib to flow through the lower electrodes 17C and 17D of the detection elements 10C and 10D by the current sources 33A and 33B. Thereby, the magnetization directions of the free layer and the fixed layer of the detection elements 10C and 10D are made antiparallel.

  In the next step S302, the storage unit 27 of the control unit 25F stores the output voltage Vout of the differential amplifier circuit 23. The output voltage Vout at this time is the minimum output voltage Vmin.

  In the next step S303, the control unit 25F supplies a sufficiently large bias current Ib to the lower electrodes 17A and 17B of the detection elements 10A and 10B by the current sources 31A and 31B. Thereby, the magnetization directions of the free layer and the fixed layer of the detection elements 10A and 10B are made antiparallel. Further, the control unit 25F causes a sufficiently large bias current Ib to flow through the lower electrodes 17C and 17D of the detection elements 10C and 10D by the current sources 33A and 33B. Thereby, the magnetization directions of the free layer and the pinned layer of the detection elements 10C and 10D are made parallel.

  In the next step S304, the storage unit 27 of the control unit 25F stores the output voltage Vout of the differential amplifier circuit 23. The output voltage Vout at this time is the maximum output voltage Vmax.

In the next step S305, an unknown external magnetic field Hex is applied to the magnetic field detection device 5.
In next step S306, the control unit 25F acquires and stores the output voltage Vout of the differential amplifier circuit 23 when a bias current having a predetermined magnitude in consideration of detection sensitivity is supplied from the detection elements 10A to 10D. Store in the unit 27.

  In the next step S307, after detecting the direction of the external magnetic field Hex, the control unit 25F is sufficiently applied to the lower electrodes 17A and 17B of the detection elements 10A and 10B by the current sources 31A and 31B in a state where the external magnetic field Hex is not applied. A large bias current Ib is supplied. Thereby, the magnetization directions of the free layers and the fixed layers of the detection elements 10A and 10B are made parallel. Further, the control unit 25F causes a sufficiently large bias current Ib to flow through the lower electrodes 17C and 17D of the detection elements 10C and 10D by the current sources 33A and 33B. Thereby, the magnetization directions of the free layer and the fixed layer of the detection elements 10C and 10D are made antiparallel.

  In the next step S308, the storage unit 27 of the control unit 25F stores the output voltage Vout of the differential amplifier circuit 23. The output voltage Vout at this time is the minimum output voltage Vmin.

  In the next step S309, the control unit 25F supplies a sufficiently large bias current Ib to the lower electrodes 17A and 17B of the detection elements 10A and 10B by the current sources 31A and 31B. Thereby, the magnetization directions of the free layer and the fixed layer of the detection elements 10A and 10B are made antiparallel. Further, the control unit 25F causes a sufficiently large bias current Ib to flow through the lower electrodes 17C and 17D of the detection elements 10C and 10D by the current sources 33A and 33B. Thereby, the magnetization directions of the free layer and the pinned layer of the detection elements 10C and 10D are made parallel.

  In the next step S310, the storage unit 27 of the control unit 25F stores the output voltage Vout of the differential amplifier circuit 23. The output voltage Vout at this time is the maximum output voltage Vmax.

  In the next step S311, the calculation unit 26, the minimum output voltage Vmin (1) in step S302, the maximum output voltage Vmax (1) in step S304, the minimum output voltage Vmin (2) in step S308, and the maximum output in step S308. Using the voltage Vmax (2), the temperature correction of the output voltage Vout acquired in step S306 is performed. Specifically, the calculation unit 26 multiplies the output voltage Vout acquired in step S306 by (Vmax (2) −Vmin (2)) / (Vmax (1) −Vmin (1)), thereby obtaining a final value. The output voltage Vout after temperature correction is obtained.

  In the next step S312, the calculation unit 26 calculates the direction of the unknown external magnetic field Hex using the output voltage Vout after temperature correction. The principle of calculating the direction of the external magnetic field Hex is as follows.

According to the above equation (1), the resistance values of the detection elements 10A to 10D are R _A , R _B , R _C , and R _D , respectively.
R _A = Rm + (ΔR / 2) × cos θ
R _B = Rm + (ΔR / 2) × cos (θ + 180 °) = Rm− (ΔR / 2) × cos θ
R _C = Rm + (ΔR / 2) × cos (θ + 90 °) = Rm− (ΔR / 2) × sin θ
R _D = Rm + (ΔR / 2) × cos (θ + 270 °) = Rm + (ΔR / 2) × sinθ
It is expressed as Therefore, if the values of Rm and ΔR are obtained in advance, the angle θ can be calculated using R _A and R _C. Here, the values of Rm and ΔR can be calculated using the maximum value and the minimum value of the element resistance.

  By the above method, the magnetic field direction can be detected with high accuracy while correcting the change in sensitivity due to temperature.

[Modification of Embodiment 5]
FIG. 28 is a plan view schematically showing a configuration of a magnetic field detection device 5A according to a modification of the fifth embodiment of the present invention. The magnetic field detection device 5A of FIG. 28 is that the direction of the magnetization vector Mp of the pinned layer of the detection element 10B is the −X direction, and the direction of the magnetization vector Mp of the pinned layer of the detection element 10D is the + Y direction. Different from the magnetic field detection device 5 of FIG. As the direction of the magnetization vector Mp of the pinned layer is sufficient if the detection elements adjacent to each other in the rotation direction in the substrate plane are orthogonal to each other, the magnetic field detection device 5A of FIG. Similar effects can be obtained.

[Embodiment 6]
FIG. 29 is a diagram schematically showing a configuration of the rotation angle sensor 6 according to the sixth embodiment of the present invention. The rotation angle sensor 6 of FIG. 29 is an application of the magnetic field detection device 5 of the fifth embodiment.

  Referring to FIG. 29, rotation angle sensor 6 includes a permanent magnet 81 attached to the tip of rotation shaft 82, detection elements 83 </ b> A to 83 </ b> D formed on substrate 83, and control unit 84. Detection elements 83A to 83D and control unit 84 correspond to magnetic field detection device 5 of the fifth embodiment. The magnetic field detection device 5 can measure the magnetic field application direction with high accuracy when the magnitude of the magnetic field is substantially constant and the direction of the magnetic field changes, such as a rotating magnetic field generated by the rotation of the permanent magnet 81.

  The embodiment disclosed this time must be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1-5 Magnetic field detection apparatus, 10 Detection element (TMR element), 50 Reference element (TMR element), 12 Antiferromagnetic layer, 12A Magnetic layer, 14,54 Tunnel insulating layer, 13 Ferromagnetic layer (pinned layer), 15 Ferromagnetic layer (free layer), 17, 57 Lower electrode, 18, 58 Upper electrode, 20 Measurement unit, 21 Voltage source, 23 Differential amplifier circuit, 24 Reference voltage source, 25 Control unit, 26 Calculation unit, 27 Storage unit , 31, 33 Current source, 32, 34 Magnetic field generator, 40 substrate, 71 switch, Hb bias magnetic field, Ib bias current, Hex external magnetic field, Mf magnetization vector (free layer), Mp magnetization vector (pinned layer).

Claims (2)

A magnetic field detection method for detecting an unknown external magnetic field using a detection element,
The detection element is sandwiched between a first ferromagnetic film whose magnetization direction changes according to the external magnetic field, a second ferromagnetic film whose magnetization direction is constant, and these ferromagnetic films A tunnel magnetoresistive element including a tunnel insulating film,
The magnetic field detection method includes a step of storing a plurality of setting values of a bias magnetic field applied to the detection element in association with a plurality of known external magnetic fields, respectively.
Each of the plurality of set values is set to a value such that the electrical characteristics of the detection element measured in a state where both the bias magnetic field and the corresponding known external magnetic field are applied are within a predetermined optimum range. ,
The magnetic field detection method further includes a step of measuring electrical characteristics of the detection element when a bias magnetic field of any one of the plurality of setting values and the unknown external magnetic field are applied together,
In the measuring step, the setting value of the bias magnetic field is changed until the measured electrical characteristics of the detection element are within the optimum range,
The magnetic field detection method includes:
Calculating the magnitude of the unknown external magnetic field based on the electrical characteristics when the electrical characteristics of the detection element measured in the measuring step are within the optimum range;
Measuring electrical characteristics of the detection element when a correction bias magnetic field is applied in a state where the external magnetic field is not applied before the detection of the external magnetic field;
Measuring the electrical characteristics of the detection element when the correction bias magnetic field is applied in a state where the external magnetic field is not applied after the detection of the external magnetic field;
The step of correcting the magnitude of the unknown external magnetic field calculated in the calculating step using the electrical characteristics of the detection element measured in accordance with the correction bias magnetic field before and after the detection of the external magnetic field. further comprising magnetic field detecting method and. The correction bias magnetic field includes both a magnetic field that makes the magnetization direction of the first ferromagnetic film parallel to the magnetization direction of the second ferromagnetic film, and a magnetic field that makes it antiparallel. 2. The magnetic field detection method according to 1.

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