JP2020012831A - Magnetic sensor and magnetic sensor device - Google Patents

Abstract

To provide a magnetic sensor and a magnetic sensor device capable of suppressing noise and having high sensitivity.SOLUTION: A magnetic sensor according to the present embodiment comprises: a magnetic field detection part having a magnetic layer the length of which in a first direction is 10 times the length in a second direction orthogonal to the first direction or more, and the length of which in a third direction orthogonal to the first direction and the second direction is 1/2 the length in the second direction or less; a first magnetic substance member arranged along the first direction of the magnetic field detection part and the length of which in the third direction is longer than the length of the magnetic layer in the third direction; a first nonmagnetic insulation layer arranged between the magnetic field detection part and the first magnetic substance member and the length of which in the second direction is 1/2 the length of the magnetic layer in the second direction or less; and a circuit for sending a current to the magnetic layer.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a magnetic sensor and a magnetic sensor device.

  Conventionally, as a device for measuring a magnetic field generated from a living body, a biomagnetic measurement device using a SQUID (Superconducting Quantum Interference Device) magnetic sensor has been proposed. In this biomagnetism measuring apparatus, two-dimensional biomagnetic information such as a magnetoencephalogram and a magnetocardiogram can be obtained by arranging a large number of SQUID magnetic sensors and using them for measuring biomagnetism. Since this SQUID magnetic sensor uses superconductivity, it needs to be cooled with a refrigerant such as liquid helium. For this reason, the biomagnetism measuring device using the SQUID magnetic sensor becomes bulky, uses a refrigerant, increases operating costs, increases power consumption, and requires the measurement object (patient) to be restrained.

  Further, a TMR type magnetic sensor (an element using a tunnel magneto-resistance effect) is known. This TMR type magnetic sensor has a large output but a large noise level, and as a result, the SN ratio deteriorates.

  On the other hand, a CIP-GMR type magnetic sensor (an element using an in-plane energized giant magnetoresistance effect CIP-GMR (Current In Plane-Giant Magneto-Resistance)) has been proposed. This CIP-GMR type magnetic sensor has a small noise level due to a small resistance, but has a small output due to a small magnetoresistance change rate. Further, there has been proposed an element which has a configuration in which a magnetic flux concentrator (MFC: Magnetic Flux Concentrator) made of a soft magnetic material is provided in a CIP-GMR type magnetic sensor to improve the output.

  The direction of the magnetic field detected by the CIP-GMR type magnetic sensor is a direction perpendicular to the long axis, and when the magnetization of the magnetization detection layer rotates in that direction, a magnetic charge (magnetic charge) is generated on the side wall surface of the fine wire, so that the magnetic field is detected. A magnetic field is created. This demagnetizing field causes non-linear distortion in the rotation of the magnetization, and the distortion varies depending on the position of the thin wire, which causes a problem of lowering the S / N ratio of the magnetic field detection.

JP 2001-358378 A JP 2004-150994 A

Japanese Journal of Applied Physics 52 (2013) 04CM07 IEEE Transaction on Magnetics, vol.43, No.6 p.2376

  The present embodiment provides a magnetic sensor and a magnetic sensor device that can suppress noise and have high sensitivity.

  In the magnetic sensor according to the present embodiment, the length in the first direction is at least 10 times the length in the second direction orthogonal to the first direction, and the length in the third direction orthogonal to the first direction and the second direction. A magnetic field detection unit having a magnetic layer whose length is equal to or less than の of the length in the second direction; and a magnetic field detection unit disposed along the first direction of the magnetic field detection unit, the magnetic layer having a length in the third direction. A first magnetic member having a length in the third direction longer than a length, and being disposed between the magnetic field detecting section and the first magnetic member; A first non-magnetic insulating layer having a length equal to or less than の of a length in two directions, and a circuit for flowing a current through the magnetic layer;

FIG. 2 is a plan view of the magnetic sensor according to the first embodiment. 2A and 2B are diagrams schematically showing rotation of magnetization in a magnetoresistive layer due to an external magnetic field. FIG. 7 is a diagram illustrating a change in the short axis direction of the magnetization of the magnetoresistive layer with respect to an external magnetic field applied in the short axis direction. The figure which shows operation | movement of a magnetic field converging body typically. FIGS. 5A to 5D are diagrams schematically showing the operation of the magnetic field converging body in the yz plane. FIG. 3 is a schematic diagram of a model used for a simulation for calculating a relationship between a distance between a magnetoresistive layer and a magnetic field converging body and a magnetic field detection sensitivity. The figure which shows the hysteresis curve calculated | required by the simulation when the thickness of a magnetoresistive layer is 10 nm. The figure which shows the hysteresis curve calculated | required by the simulation when the thickness of a magnetoresistive layer is 20 nm. The figure which shows the hysteresis curve calculated | required by the simulation when the thickness of a magnetoresistive layer is 50 nm. The figure showing the simulation result of change of μ_95 to the length of interval gap. The figure showing the simulation result of change of μ_95 normalized to the length of interval gap. The figure which shows the calculation result of the hysteresis loop when the length of the short axis direction of a magnetoresistive layer and a magnetic field converging body is 200 nm. The figure which shows the calculation result of the hysteresis loop when the length of the short axis direction of a magnetoresistive layer and a magnetic field converging body is 200 nm, and the length of a long axis direction is 2000 nm. FIG. 6 is a plan view of a magnetic sensor according to a second embodiment. FIG. 13 is a plan view of a magnetic sensor according to a modification of the second embodiment. FIG. 13 is a plan view of a magnetic sensor according to a third embodiment. 17A and 17B are cross-sectional views of a magnetic field detection unit according to the third embodiment. FIG. 4 is a sectional view showing a first example of a magnetic field detection unit. FIG. 6 is a sectional view showing a second example of the magnetic field detection unit. Sectional drawing which shows the 3rd example of a magnetic field detection part. Sectional drawing which shows the 4th example of a magnetic field detection part. Sectional drawing which shows the 5th example of a magnetic field detection part. Sectional drawing which shows the 6th example of a magnetic field detection part. FIGS. 24A to 24C are plan views illustrating a method for manufacturing a magnetic sensor. 25A to 25C are cross-sectional views illustrating a method for manufacturing a magnetic sensor. 26A and 26B are cross-sectional views illustrating a method for manufacturing a magnetic sensor. FIG. 27 is a diagram showing the shape of the magnetic sensor used for estimating the noise level, and FIG. 27B is a diagram showing the result of estimating the noise level. The figure which shows the magnetic sensor apparatus by 4th Embodiment. FIG. 14 is a diagram showing a magnetic sensor device according to a first modification of the fourth embodiment. FIG. 14 is a diagram showing a magnetic sensor device according to a second modification of the fourth embodiment. The figure which shows one Example of a sensor part.

  Hereinafter, embodiments will be described in detail with reference to the drawings.

(1st Embodiment)
FIG. 1 shows a schematic plan view of the magnetic sensor according to the first embodiment. The magnetic sensor 1 according to the first embodiment includes a magnetic field detecting unit 11, nonmagnetic insulating layers 12a and 12b provided so as to sandwich the magnetic field detecting unit 11, and a magnetic field detecting unit 11 with respect to the nonmagnetic insulating layer 12a. And a magnetic field converging body 13b provided on the side opposite to the magnetic field detecting unit 11 with respect to the nonmagnetic insulating layer 12b. In the first embodiment, a magnetoresistive layer (magnetic layer) 11A is used as a magnetic field detecting unit.

  Non-magnetic insulators 12a and 12b are in contact with the end surface of the long axis (x direction) of the magnetoresistive layer 11A. Further, magnetic field converging members 13a and 13b are in contact with the non-magnetic insulators 12a and 12b, respectively. A detection circuit 16 is connected to the magnetoresistive layer 11A to detect a magnetic field intensity by causing a current to flow in the major axis direction, rotating the magnetization of the magnetoresistive layer 11A by an external magnetic field, and thereby changing the electric resistance at both ends. ing. In FIG. 1, the z direction is the film thickness direction. The direction of the magnetic field to be measured is the direction indicated by reference numeral 17.

  The magnetoresistive layer 11A is formed by a so-called magnetoresistive effect (AMR (Anisotropic Magneto-Resistive)) or an in-plane conduction type giant magnetoresistive effect (CIP (Current In Plane) -GMR (Giant Magneto-resistance)). Measure the magnetic field strength. The phenomenon in which the magnetization in the magnetoresistive layer 11A is rotated by the magnetic field to be measured, which changes the resistance of the magnetoresistive layer 11A is used. In order to effectively use this phenomenon, it is necessary to rotate the magnetization in the magnetoresistive layer 11A while maintaining a uniform magnetization state in the plane. For this reason, it is preferable that the ratio of the length of the short axis direction (y direction) of the magnetoresistive layer 11A to the length of the long axis direction (x direction) is 10 or more.

  With this configuration, when the magnetic anisotropy is not particularly given to the magnetoresistive layer 11A, the magnetization in the magnetoresistive layer 11A is uniformly long axis when the external magnetic field is zero due to the shape magnetic anisotropy. Turn in the direction. When the magnetic anisotropy is given in the short axis direction by cooling in a magnetic field or the like, the magnetization in the magnetoresistive layer 11A is uniformly directed in the short axis direction. If the ratio of the short axis to the long axis of the magnetoresistive layer 11A is less than 10, the shape magnetic anisotropy is weakened, so that the magnetization inside the magnetoresistive layer 11A is difficult to be uniformly oriented in the same direction. Occurs. This undesirably deteriorates the sensitivity of the magnetic field measurement and increases noise.

  The thickness (length in the z direction) of the magnetoresistive layer 11A is preferably equal to or less than の of the length in the short axis direction (y direction). If the thickness is larger than 1/2 of the length in the minor axis direction, the magnetization tends to be directed also in the direction perpendicular to the film surface, and magnetic domains are easily generated. In addition, uniform rotation of magnetization in the film plane does not easily occur. Therefore, the sensitivity of the magnetic field measurement deteriorates and noise increases, which is not preferable.

  The magnetic field converging members 13a and 13b are preferably formed of a soft magnetic material. In the magnetic field converging body 13a, the cross-sectional area of the surface 14 on the magnetoresistive layer 11A side is smaller than the cross-sectional area of the opposing surface 15 thereof. Similarly to the magnetic flux converging body 13a, the cross-sectional area of the magnetic flux converging body 13b on the side of the magnetoresistive layer 11A is smaller than that of the opposing surface. As a method of creating such a difference in cross-sectional area, as shown in FIG. 1, the film thickness of the magnetic field converging bodies 13a and 13b is made constant, and the length of the surface 14 on the side of the magnetoresistive layer 11A in the x direction is adjusted. The length can be smaller than the length of the facing surface 15 in the x direction. Further, the length of the surface 14 on the side of the magnetoresistive layer 11A in the x direction is equal to the length of the opposing surface 15 in the x direction, and the thickness of the surface 14 (the length in the z direction) is made larger than the thickness of the surface 15. It may be thin. Further, these two methods may be combined.

  In the first embodiment shown in FIG. 1, the magnetic field converging bodies 13a and 13b are provided on both sides of the end face on the long axis side of the magnetoresistive layer 11A via the nonmagnetic insulating layers 12a and 12b, but are provided on one side. You may. In this case, the manufacturing process is simplified, but the magnetic field focusing effect is reduced.

  The magnetic field converging bodies 13a and 13b used in the first embodiment are generally used as an MFC (Magnetic Flux Concentrator). That is, the magnetic flux lines arriving at the outermost surface 15 of the magnetic sensor 1 are narrowed down to the opposite surface 14 in the magnetic field converging body 13a, and the magnetic flux density, that is, the magnetic field intensity increases according to the ratio of the cross-sectional area. . The magnetic sensor 1 according to the present embodiment can improve the magnetic field measurement efficiency by using the magnetic field converging bodies 13a and 13b.

  Non-magnetic insulators 12a and 12b are provided between the magnetic field concentrators 13a and 13b and the magnetoresistive layer 11A, respectively.

  If the non-magnetic insulators 12a and 12b are not provided, the magnetic field concentrators 13a and 13b and the magnetoresistive layer 11A conduct, so that the current flowing through the magnetoresistive layer 11A decreases non-uniformly and the detected signal Will deteriorate. Further, since the magnetoresistive layer 11A and the magnetic field converging bodies 13a and 13b are exchange-coupled, the rotation of the magnetization of the magnetoresistive layer 11A due to the external magnetic field is not uniform, and the detection sensitivity is lowered and noise is increased, which is not preferable. Therefore, it is preferable that the nonmagnetic insulators 12a and 12b are nonmagnetic and insulators.

  The length of the non-magnetic insulators 12a and 12b in the major axis direction (x direction) may be the same as or larger than that of the magnetoresistive layer 11A. It is preferable that the length in the short axis direction (y direction) is 50 nm or less, or 1/2 or less of the length of the magnetoresistive layer 11A in the short axis direction. If the length of the nonmagnetic insulators 12a and 12b in the minor axis direction (y direction) is 1 nm or less, it is difficult to form a continuous structure as an insulator, which is not preferable. The thickness (the length in the z direction) of the nonmagnetic insulators 12a and 12b may be the same as or larger than the magnetoresistive layer 11A.

  As long as the magnetic flux converging bodies 13a and 13b do not adversely affect the magnetic flux converging effect of the magnetic field converging bodies 13a and 13b and the rotation of the magnetization of the magnetoresistive layer 11A, the magnetic field converging bodies 13a and 13b and the non-magnetic insulators 12a and 12b or non-magnetic insulating A magnetic material or another non-magnetic material may be provided between the bodies 12a and 12b and the magnetoresistive layer 11A.

  The length (length in the x direction) of the surfaces of the magnetic field converging bodies 13a and 13b on the magnetoresistive layer 11A side may be longer or shorter than the length (length in the x direction) of the magnetoresistive layer 11A. When the length of the magnetic field converging bodies 13a and 13b is long, a part of the converged magnetic flux is lost, and as a result, the magnetic field intensity decreases. However, the influence of the disturbance of the magnetic field at the ends of the magnetic field converging bodies 13a and 13b can be reduced.

  On the other hand, when the length of the magnetic field converging bodies 13a and 13b in the x direction is shorter than the length of the magnetoresistive layer 11A in the x direction, there is an advantage that all the converged magnetic fluxes can be detected. However, since the magnetic field strength in the magnetic sensor 1 is distributed, linearity may be lost. The length of the surface 14 of the magnetic field converging bodies 13a and 13b on the side of the magnetoresistive layer 11A may be determined based on the required specifications of the magnetic sensor 1 to be created.

  The length of the magnetic field converging members 13a and 13b in the y direction is not particularly limited, but is preferably longer than the length of the magnetoresistive layer 11A in the y direction because a realistic convergence effect can be expected.

  The operation of the magnetic sensor 1 according to the present embodiment shown in FIG. 1 that can detect a magnetic field with low noise and high sensitivity will be described below. FIGS. 2A and 2B schematically show rotation of the magnetization 22 in the magnetoresistive layer 21 due to an external magnetic field. FIG. 2A shows the case where the external magnetic field is zero. In this case, the magnetization 22 is uniformly oriented in the longitudinal direction. At this time, no magnetic charges appear on the end face on the long axis side of the magnetoresistive layer 21, that is, on the end face 23 along the long axis.

  FIG. 2B shows a case where an external magnetic field is applied in the short axis direction. At this time, the magnetization 22 rotates as shown in the figure. At this time, a magnetic charge 24 is generated on the end face 23 on the long axis side of the magnetoresistive layer 21. The magnetic charge 24 generates a demagnetizing field, that is, a leakage magnetic field from the magnetic charge 24, thereby changing the direction of the magnetization 22 itself. Since the distribution of the magnetic charge 24, that is, the distribution of the demagnetizing field is local, a magnetic domain is easily formed in the magnetoresistive layer 21, and the rotation state of the magnetization becomes non-uniform. In particular, in the vicinity of the end 25 of the magnetoresistive layer 21, the nonuniformity of the magnetization rotation due to the magnetic charge becomes remarkable.

  When such a phenomenon occurs, the rotation of the magnetization becomes nonlinear with respect to the external magnetic field, and it becomes impossible to measure the magnetic field with high accuracy. This is schematically shown in FIG. FIG. 3 shows a change in the magnetization M in the minor axis direction of the magnetoresistive layer 21 with respect to the external magnetic field H. In the case of an ideal magnetic sensor, as shown in the graph 31, the magnetization M increases linearly with respect to the magnetic field, and does not change after the saturation magnetic field Hk. With such characteristics, the magnetic field strength H and the magnetization M are in a highly accurate proportional relationship in a magnetic field of Hk or less, so that a highly accurate magnetic field measurement can be performed.

  On the other hand, when a magnetic charge is generated and the magnetization rotation becomes non-linear as shown in FIG. 2B, the characteristics are as shown in a graph 32, for example. Since the magnetization M changes nonlinearly with the change in the magnetic field H, the accuracy of the magnetic field measurement deteriorates. In addition, a so-called hysteresis, in which the value of the magnetization M is different from the same value of the magnetic field H when the magnetic field is increased and when the magnetic field is decreased, occurs, and the reproducibility and reliability of the measurement deteriorate.

  In order to prevent such a non-linear phenomenon due to the generation of magnetic charges, a method of increasing the magnetic anisotropy in the major axis direction and relatively reducing the influence of the leakage magnetic field due to the magnetic charges is generally known. However, in this case, the saturation magnetic field Hk increases as shown in the graph 33. In FIG. 3, the saturation magnetic field Hk does not exist in the range shown in the figure, and the change in the magnetization M with respect to the magnetic field H decreases. . As a result, the magnetic field sensitivity decreases.

  As described above, when performing the magnetic field measurement by rotating the magnetization of the magnetoresistive layer 11A, there is a problem that the measurement accuracy is deteriorated by the magnetic charge generated at the long-axis end due to the rotation of the magnetization.

  In the present embodiment, this problem is solved by providing the magnetic field converging bodies 13a and 13b. That is, the magnetic field converging members 13a and 13b are provided on the end face along the long axis of the magnetoresistive layer 11A via the nonmagnetic insulators 12a and 12b. FIG. 4 is a schematic diagram for explaining this part. The magnetization of the magnetoresistive layer 11A is rotated by an external magnetic field to generate a magnetic charge 24a. This magnetic charge 24a is indicated by a symbol “+”. The magnetic field converging body 13 made of a soft magnetic material is provided near the magnetoresistive layer 11A.

  Since the magnetic field converging member 13 is soft magnetic, the leakage magnetic field generated by the magnetic charge 24a of the magnetoresistive layer 11A rotates the magnetization of the surface of the magnetic field converging member 13 on the magnetoresistive layer 11A side, and the magnetic charges in the opposite direction. 24b is generated. This magnetic charge 24b is indicated by the symbol "-". As described above, when the magnetic charges 24a and 24b are generated, magnetic flux lines directly connecting the magnetic charges 24a and 24b are formed, and as a result, a leakage magnetic field (demagnetizing field) that affects the rotation of the magnetization of the magnetoresistive layer 11A is formed. ) Disappears. This means that, when viewed from the magnetoresistive layer 11A, the end of the major axis does not exist, and the magnetoresistive layer 11A looks as if it continues infinitely in the y direction.

  This situation is shown in FIGS. 5 (a) to 5 (d). 5A to 5D show the magnetoresistive layer 11A and the magnetic field converging body 13 in the yz plane. FIG. 5A shows a case where the thickness of the magnetoresistive layer 11A and the magnetic field converging body 13 are the same and the distance is large, and the leakage magnetic field from the magnetic charge 24a is completely absorbed by the magnetic charge 24b of the magnetic field converging body 13. However, some of them leak out and affect their own magnetization 24a.

  If the distance between the magnetoresistive layer 11A and the magnetic field absorber 13 is sufficiently short, as shown in FIG. 5B, the magnetic flux that leaks out and affects its magnetization 24a is reduced, and the demagnetizing field is canceled. can do.

  On the other hand, as shown in FIG. 5C, when the thickness (length in the z direction) of the magnetic field converging body 13 is smaller than the thickness (length in the z direction) of the magnetoresistive layer 11A, the distance between the two is reduced. Even if it is sufficiently small, a demagnetizing field which goes around the magnetoresistive layer 11A itself is generated.

  Conversely, when the thickness (length in the z direction) of the magnetic field converging body 13 is larger than the thickness (length in the z direction) of the magnetoresistive layer 11A, as shown in FIG. As a result, the demagnetizing field can be canceled.

(Relationship between the distance between the magnetoresistive layer and the magnetic field concentrator and the magnetic field detection sensitivity)
Next, the relationship between the distance between the magnetoresistive layer 11A and the magnetic field converging bodies 13a and 13b and the magnetic field detection sensitivity was simulated using the Landau-Lifshitz-Gilbert (LLG) equation. FIG. 6 is a schematic diagram of the model used for the calculation. As the magnetoresistive layer 11A, a model having a width of 100 nm, a length of 1000 nm (major axis / minor axis ratio of 10), and a thickness t of 10, 20, and 50 nm was used as a model. This was divided by a rectangular mesh having one side of 10 nm. Properties of a material, the saturation magnetization Ms assuming using NiFe as the magnetoresistive layer 11A and 800 emu / cc, and a 1kerg / cc magnetic anisotropy Ku _y in the y direction. The calculation was performed with an exchange constant A between meshes of 1 μerg / cm and a Gilbert damping constant α of 1.0. The magnetic field converging bodies 13a and 13b have the same size and the same magnetic characteristics as the magnetoresistive layer 11A, and are arranged on the same plane at a predetermined interval (gap) as shown in FIG. Five types of gaps of 10, 20, 30, 50, and 100 nm were prepared.

  It is difficult to make the magnetic field converging bodies 13a and 13b large in size close to the present embodiment because the calculation time becomes enormous. In order to simulate the rotation of the magnetization of the magnetic field converging bodies 13a and 13b, the magnetization of the magnetic field converging bodies 13a and 13b at the end 10 nm (one mesh) on the opposite side to the magnetoresistive layer 11A is shifted in the x direction. An operation of fixing with a magnetic field of 20 kOe was performed. By this operation, the generation of the leakage magnetic field due to the generation of the magnetic charge on the opposing surfaces of the magnetic field converging bodies 13a and 13b on the side of the magnetoresistive layer 11A is eliminated, and as described above, the magnetic field converging bodies 13a and 13b are infinitely long in the y direction. The magnetization rotation resembles that of a magnetic material. This operation is generally used when simulating the magnetization rotation of the soft magnetic material.

  FIGS. 7 to 9 show the calculated hysteresis loop. The horizontal axis is the applied magnetic field strength, and the vertical axis is the normalized magnetization in the y direction of the magnetoresistive layer 11A. An external magnetic field was applied in the y direction as shown in FIG. The y-direction component of the magnetization of only the central portion (a rectangular portion of 500 nm × 100 nm in the xy plane) of the magnetoresistive layer 11A is plotted. As a result, hysteresis corresponding to an amount directly corresponding to the GMR or AMR output, excluding artificial hysteresis noise caused by the narrow calculation region, is obtained. 7 shows a hysteresis loop when the thickness t shown in FIG. 6 is 10 nm, FIG. 8 shows a hysteresis loop when the thickness t shown in FIG. 6 is 20 nm, and FIG. 9 shows a hysteresis loop when the thickness t shown in FIG. In all cases, the hysteresis loops are almost closed, and relatively linear characteristics are obtained. The magnitude and linearity of the hysteresis improve as the film thickness t decreases. This means that there is almost no magnetization rotation in the film thickness direction of the magnetoresistive layer 11A. Therefore, the film thickness of the magnetoresistive layer 11A is less than half the length of the short axis (= 100 nm). It was shown that in some cases good soft magnetic properties were obtained.

  From each hysteresis loop, a magnetic field H_95 reaching 95% of the saturation magnetization Ms was obtained as an index corresponding to the magnetic field detection sensitivity, and its reciprocal 1 / (H_95) was obtained as μ_95. FIG. 9 schematically shows how to determine the magnetic field H_95. Line 101 is a position where the magnetization becomes 95% of the saturation amount, and the external magnetic field at the magnetization becomes H_95. The smaller the magnetic field H_95, that is, the larger μ_95, the higher the magnetic field detection sensitivity to the magnetic field.

  FIG. 10 shows a change in μ_95 with respect to the size of the gap “gap”. FIG. 11 shows a graph obtained by normalizing the graph shown in FIG. 10 with a value when the interval gap is 100 nm. As can be seen from FIG. 11, μ_95 sharply increases at an interval gap smaller than 50 nm for any film thickness. In particular, when the gap “gap” is smaller than 20 nm, μ_95 increases by 20% or more. This is because, as described with reference to FIGS. 5A to 5D, the distance between the magnetic field converging bodies 13a and 13b and the magnetoresistive layer 11A is shortened, so that the generation of a demagnetizing field is suppressed, and an ideal This is because soft magnetic characteristics can be obtained. From the results of FIGS. 10 and 11, when the distance between the magnetoresistive layer 11A and the magnetic field converging bodies 13a and 13b is 50 nm or less, more preferably 20 nm or less, that is, when the width of the magnetoresistive layer 11A is 1/2 or less. It was found that this effect remarkably appeared. When the distance between the magnetoresistive layer 11A and the magnetic field concentrators 13a and 13b is 0 nm, that is, when the non-magnetic insulators 12a and 12b are eliminated, a shunt of the measurement current occurs as described above, and the magnetization rotation occurs. Since it becomes non-uniform, the SN ratio of the magnetic field detection signal deteriorates, which is not preferable.

  Next, a case was calculated in which the length (width) of the short axis direction (y direction) of the magnetic resistance layer 11A and the magnetic field converging bodies 13a and 13b was 200 nm. FIG. 12 shows the result when the film thickness t = 10 nm. The calculation region of the hysteresis loop is a central portion of the magnetoresistive layer 11A, that is, a rectangular portion of 500 nm × 200 nm in the xy plane. As can be seen from FIG. 12, extreme nonlinearity, that is, a large hysteresis loop appeared, and a hysteresis loop in which the linearity of the magnetization curve was almost lost was obtained. This indicates that, as described above, since the ratio of the short axis to the long axis of the magnetoresistive layer 11A is less than 10, the magnetization inside the magnetoresistive layer 11A is difficult to rotate uniformly. This tendency was the same even when the film thickness t was 20, 50, and 100 nm.

Next, the length (width) of the short axis direction (y direction) of the magnetoresistive layer 11A and the magnetic field converging bodies 13a and 13b is set to 200 nm, and the thickness t is set to 10 nm. FIG. 13 shows the results when the length in the major axis direction (x direction) was 2000 nm. The calculation region of the hysteresis loop was a central portion of the magnetoresistive layer 11A, that is, a rectangular portion of 1000 nm × 200 nm in the xy plane. Since the calculation time is enormous, the interval gap is 10, nm
Only the calculation for the case of 20 nm was performed, and it can be seen that the nonlinearity observed in FIG. 12 has disappeared. From this, it was found that the ratio of the short axis to the long axis of the magnetoresistive layer 11A is preferably 10 or more.

  As described above, according to the first embodiment, it is possible to suppress the nonlinearity of the detection sensitivity, thereby providing a magnetic sensor that suppresses noise and has high sensitivity.

(2nd Embodiment)
Next, a magnetic sensor according to a second embodiment will be described with reference to FIG. FIG. 14 is a plan view of a magnetic sensor 1A according to the second embodiment.

  In general, in the in-plane magnetic sensor, in order to increase the detection output and the SN ratio, the length of the magnetoresistive layer 11A may be increased. However, if the sensor is elongated in one direction, the shape of the sensor becomes elongated, and it becomes difficult to make the sensor small. A magnetic sensor that solves this problem will be described as a second embodiment.

  The magnetic sensor 1A according to the second embodiment has a configuration in which the magnetoresistive layer 11A serving as a magnetic field detecting unit is folded back to form a zigzag shape as shown in FIG. 14 in the magnetic sensor 1 according to the first embodiment shown in FIG. ing. In FIG. 14, the magnetic sensor 1A is folded twice. However, as compared with the case where the magnetic sensor 1A is not folded, there is an advantage that the length of the entire magnetic sensor 1A in the x direction can be reduced to ３.

  Also in the second embodiment, as in the first embodiment, a magnetic sensor capable of detecting a magnetic field with low noise and high sensitivity can be realized. That is, as shown in FIG. 14, the outermost portion of the magnetoresistive layer 11A is provided with nonmagnetic insulators 12a and 12b and magnetic field converging members 13a and 13b made of a soft magnetic material on the end face on the long axis side. The width of the nonmagnetic insulators 12a and 12b, that is, the distance between the magnetoresistive layer 11A and the magnetic field converging bodies 13a and 13b is 50 nm or less (（the length of the short axis of the magnetoresistive layer 11A or less). )And it is sufficient. The requirements to be satisfied by the magnetic field converging bodies 13a and 13b at this time are the same as in the first embodiment.

  The operation of detecting the magnetic field with low noise and high sensitivity is the same as that of the first embodiment. Since the magnetic field converging members 13a and 13b made of a soft magnetic material have the function of canceling the demagnetizing field due to the magnetic charge generated at the end of the magnetoresistive layer 11A, the non-linear rotation of the magnetization is prevented.

As in the first embodiment, the second embodiment can provide a magnetic sensor that suppresses noise and has high sensitivity.

(Modification)
FIG. 15 shows a magnetic sensor according to a modification of the second embodiment. The magnetic sensor 1B according to the first modification is the same as the magnetic sensor 1A according to the second embodiment shown in FIG. 14 except that the three magnetoresistive layers 11Aa, 11Ab, 11Ac, two adjacent magnetoresistive layers 11Aa and 11Ab are connected in series by a conductor 161a, and two adjacent magnetoresistive layers 11Ab and 11Ac are connected in series by a conductor 161b. ing. With such a configuration of the magnetoresistive layer 11A, the configuration is electrically similar to the magnetoresistive layer 11A of the second embodiment shown in FIG.

  As shown in FIG. 14, when the magnetoresistive layer 11A is formed in a zigzag shape, the portion of the magnetoresistive layer 11A having the same direction as the measured magnetic field direction 17 does not rotate or does not rotate with respect to the measured magnetic field. Also performs a non-linear rotation, so that the contribution of the detection sensitivity is small. For this reason, the function as a magnetic sensor can be exhibited without this part. Rather, since the non-linear portion can be eliminated, a magnetic sensor with lower noise can be obtained.

  Also in the case of the modified example shown in FIG. 15, it is possible to realize a magnetic sensor capable of detecting a magnetic field with low noise and high sensitivity as in the second embodiment. That is, the nonmagnetic insulators 12a and 12b and the magnetic field concentrators 13a and 13b made of a soft magnetic material are disposed in this order on the end face on the long axis side of the outermost magnetoresistive layer 11A, and the nonmagnetic insulators 12a and 12b , Ie, the distance between the magnetoresistive layer 11A and the magnetic field converging bodies 13a and 13b may be set to 50 nm or less (（or less of the length of the short axis of the magnetoresistive layer 11A). The requirements to be satisfied by the magnetic field converging members 13a and 13b at this time are the same as in the first embodiment. The operation of detecting a magnetic field with low noise and high sensitivity is the same as that of the first embodiment.

  In addition, the conductors 161a and 161b may be provided on an intermediate form of the magnetoresistive layer 11A shown in FIGS. 14 and 15, for example, on a zigzag magnetoresistive layer, or may be provided under the conductors 161a and 161b. The resistance layer 11A may have a partially connected shape.

  This modification can also provide a magnetic sensor that suppresses noise and has high sensitivity, as in the second embodiment.

(Third embodiment)
FIG. 16 is a plan view of a magnetic sensor according to the third embodiment. The magnetic sensor 1C of the third embodiment differs from the magnetic sensor 1 of the first embodiment shown in FIG. 1 in that the magnetic field detector 11 is arranged linearly in the in-plane direction instead of the strip-shaped magnetoresistive layer 11A. The vertical conduction type GMR elements 171 are connected in series in the in-plane direction, and the entire element is configured to conduct electricity in the in-plane direction. That is, the magnetic sensor 1C according to the third embodiment differs from the magnetic sensor 1 according to the first embodiment shown in FIG. 1 in that the magnetic field detector 11 is electrically connected in series instead of the magnetoresistive layer 11A and arranged in a line. It has a configuration in which a vertical conduction type GMR element 171 is provided. Note that a vertical conduction type TMR element may be used instead of the vertical conduction type GMR element 171. In addition, although the detection sensitivity of the magnetic field is deteriorated, one vertical conduction type GMR element 171 may be used as the magnetic field detection unit 11.

  The vertical conduction type GMR element 171 is disposed in contact with the non-magnetic insulators 12a and 12b at the end faces in the y direction. FIG. 17A shows an xz cross section taken along a dotted line 172 shown in FIG. The vertical conduction type GMR elements 171 are joined in series in the arrangement shown in FIG. FIG. 17B shows a detailed configuration of the xz plane of each of the vertical conduction type GMR elements 171. The vertical conduction type GMR element 171 has a configuration in which a fixed layer 181 made of a magnetic material, a nonmagnetic layer 182, and a free layer 183 made of a magnetic material are stacked in this order.

  Both the pinned layer 181 and the free layer 183 are a magnetic material whose magnetization direction is parallel to the film surface, that is, a magnetic material whose magnetization rotates in the xy plane. The pinned layer 181 is designed so that the magnetization is not easily rotated by an external magnetic field. For this purpose, an antiferromagnetic material (not shown), which is a material having high magnetic anisotropy, is provided below the pinned layer 181 so that its magnetization direction is transmitted to the pinned layer 181 by exchange coupling. Is performed.

  The free layer 183 is a magnetic material having a property that magnetization is easily rotated by a measurement magnetic field. For this purpose, a material having soft magnetism is used. The non-magnetic intermediate layer 182 is selected from a metal or an insulator. When a thin insulator such as MgO is used, the GMR element is generally called a TMR element, but it is preferable to use a TMR element because the resistance change rate is large.

  The operation of the magnetic sensor 1C thus configured to detect a magnetic field with low noise and high sensitivity is the same as that of the first embodiment. The magnetization response to an external magnetic field is the same in the case of the magnetoresistive layer 11A and the case of the free layer 183. For this reason, when the magnetization in the free layer 183 is rotated by the external magnetic field, the magnetic field converging members 13 a and 13 b made of a soft magnetic material have an effect of canceling the demagnetizing field due to the magnetic charge generated at the end of the free layer 183. This prevents non-linear rotation of the magnetization.

  By setting the width of the nonmagnetic insulators 12a and 12b (the distance between the GMR element 171 and the magnetic field concentrators 13a and 13b) to 50 nm or less, or 1/2 or less the length of the short axis of the free layer 183, A magnetic field cancellation effect is obtained.

  If the in-plane arrangement of the vertical conducting GMR element 171 is folded in a zigzag shape and connected in series, the same operation as in the second embodiment can be obtained.

  It is preferable that the material of the free layer 183 be an FeCo alloy or a Heusler alloy because a high spin polarization is obtained and the rate of change in resistance is increased. As a material for the pinned layer 181, alloys such as CoPt and CoPd, or ordered phase alloys such as FePt, CoPt and CoPd, or Co / Pd, Co / Pt and Co / A so-called artificial lattice film in which ultra-thin magnetic layers of Ni or the like are stacked in multiple layers can also be used. Also, a soft magnetic material similar to that of the free layer 183 is used as the material of the pinned layer 181, and an antiferromagnetic layer or a pinning layer having high magnetic anisotropy is provided thereunder, and the pinned layer 181 and the pinning layer are exchange-coupled. You may let it.

  As the nonmagnetic intermediate layer 182, for example, a nonmagnetic metal containing Cu can be used. When a TMR element is used instead of the GMR element, the nonmagnetic intermediate layer 182 can be made of Al-O, Ti-O, MgO, or the like.

(Material of component)
Next, the material of each element constituting the first to third embodiments will be described.

  The magnetoresistive layer 11A as the magnetic field detecting section 11 needs to have good soft magnetic properties, that is, it has a property that magnetization rotates even with a small magnetic field and a magnetic property that shows a large change in magnetoresistance. Detailed configuration requirements of the magnetic field detection unit will be described later.

  The non-magnetic insulators 12a and 12b may be any of non-magnetic insulators used in general devices. In particular, a compound of a metal such as Si—O, Si—N, Al—O, and Mg—O and a gas such as oxygen or nitrogen is generally used. Some Fe oxides have magnetism depending on the composition, but may be used if they have a nonmagnetic composition. In addition, oxides of constituent elements such as the magnetoresistive layer 11, the magnetic field concentrators 13a and 13b, and a protective layer described later may be used.

  The magnetic field converging members 13a and 13b are preferably made of a magnetic material having the same soft magnetic properties as the magnetic resistance layer 11A. For example, by using a material including a NiFe alloy, an FeCo alloy, and a Heusler alloy, excellent soft magnetic characteristics can be obtained.

  As the circuit 16 for detecting a change in resistance, a circuit used for an ordinary magnetic resistance element can be used. For example, if a current can be applied to both ends of the magnetoresistive layer 11A in the major axis direction from a direct current source, and at the same time, if there is a mechanism capable of measuring the voltages at both ends of the magnetoresistive layer 11A, the resistance change is measured. can do. Since the magnetic sensors of the first to third embodiments are high-sensitivity magnetic sensors, it is necessary to use a current source and an amplifier with little noise.

  Underlayers for improving crystallinity, magnetic properties, and the like can be used for the magnetoresistive layer 11A, the nonmagnetic insulators 12a and 12b, and the magnetic field concentrators 13a and 13b, as needed. Further, for the purpose of preventing process damage such as subsequent application of a resist, a protective layer may be deposited continuously after the film formation. The protective layer may be removed during the process or may be left in the magnetic sensor without being removed as long as it does not hinder the operation of the magnetic sensor.

(Magnetic field detector)
Next, an example used as the magnetic field detection unit 11 will be described.

(First example)
As a first example of the magnetic field detector 11 constituting the magnetic sensor of the first or second embodiment, as shown in FIG. 18, a NiFe alloy, FeCo alloy, And a material 211 containing any one of a Heusler alloy and a Heusler alloy. As shown in FIG. 18, the soft magnetic material 211 corresponds to the magnetoresistive layer 11A of the first and second embodiments. In this case, the change in resistance occurs based on a phenomenon called a so-called metal magnetoresistance effect (AMR (Anisotropic Magneto-Resistive)).

  Since the AMR element has a simple structure, an inexpensive and highly reliable magnetic sensor can be manufactured. Further, since the electric resistance is low, the noise is low, and the effect of reducing the noise, which is one of the problems of the high-sensitivity magnetic sensor, can be obtained. However, the sensitivity is not very high because the resistance change rate is small.

(Second example)
As shown in FIG. 19, a second example of the magnetic field detection unit 11 constituting the magnetic sensor according to the first or second embodiment includes a first magnetic layer 221 made of a soft magnetic material, a nonmagnetic conductive layer 222, and a soft magnetic layer. The second magnetic layer 223 made of a body is laminated in this order, and the first magnetic layer 221 and the second magnetic layer 223 can be antiferromagnetically coupled via the nonmagnetic conductive layer 222. . As shown in FIG. 19, a laminated portion of three layers of a first magnetic layer 221, a nonmagnetic conductive layer 222, and a second magnetic layer 223 corresponds to the magnetoresistive layer 11A of the first and second embodiments.

  The magnetic field detector of the second example is called a scissors-type CIP-GMR element. Since the first magnetic layer 221 and the second magnetic layer 223 are antiferromagnetically exchange-coupled, the external magnetic field is zero. Below, the magnetizations of the respective layers are oriented in opposite directions in the major axis direction. When a magnetic field is applied in the short axis direction of the magnetic field detection unit 11, the magnetization of each layer rotates in the short axis direction, and the angle formed by the magnetizations of the two layers 221 and 223 decreases from 180 degrees. This angle change is detected as a change in magnetic resistance.

  As the nonmagnetic conductive layer 222, for example, a nonmagnetic metal containing Cu, Ru, or Ir can be used. To induce antiferromagnetic coupling in the first and second magnetic layers 221 and 223, about 2 nm is used. The thickness may be as follows.

  By subjecting the first magnetic layer 221 and the second magnetic layer 223 to processing such as cooling in a magnetic field, anisotropy may be provided in the minor axis direction. By doing so, even if the external magnetization is zero, the magnetizations of the first and second magnetic layers 221 and 223 have an angle smaller than 180 degrees. This angle becomes even smaller when the measuring magnetic field is applied.

  In general, the CIP-GMR element exhibits the largest magnetoresistance change when the angle between the magnetizations of the respective layers is around 90 degrees. Therefore, the detection sensitivity is improved by the change such that the relative angle of the magnetization approaches 90 degrees, which is preferable. . However, the cost for the process of giving the anisotropy in the short axis direction is increased. Further, there is a possibility that the anisotropy in the short axis direction varies and noise increases.

  It is preferable to use an FeCo alloy or a Heusler alloy for the first magnetic layer 221 and the second magnetic layer 223 because high spin polarization can be obtained and the resistance change rate can be increased.

(Third example)
As a third example of the magnetic field detecting unit 11 constituting the magnetic sensor of the first or second embodiment, as shown in FIG. 20, a fixed layer 231 whose magnetization is fixed in the major axis direction and an external magnetic field are detected. A free layer 233 made of a soft magnetic material whose magnetization rotates and a nonmagnetic conductive layer 232 provided between the pinned layer and the free layer can be laminated. As shown in FIG. 20, the portion of the free layer 233 corresponds to the magnetoresistive layer 11A constituting the magnetic sensor according to the first or second embodiment. In FIG. 20, the state in which the magnetization is fixed in the major axis direction is indicated by an arrow 234.

  Such a configuration is called a spin valve type CIP-GMR element, and the magnetization of the free layer 233 is rotated by the measurement magnetic field, and the angle formed by the magnetization of the fixed layer 231 changes. This angle change is detected as a change in magnetic resistance. As the nonmagnetic conductive layer 232, for example, a nonmagnetic metal containing Cu can be used.

  As a method for fixing the magnetization of the fixed layer 231, a method utilizing crystal magnetic anisotropy or shape magnetic anisotropy is generally used.

  Since the magnetic sensor using the magnetic field detector 11 of the third example has a configuration that is long in the major axis direction, a large shape magnetic anisotropy is provided in the major axis direction, that is, the direction of the arrow 234 shown in FIG. can do.

  By subjecting the free layer 233 to processing such as cooling in a magnetic field, anisotropy may be provided in the minor axis direction. By doing so, the angle formed by the magnetization of the free layer 233 and the pinned layer 231 can be made close to 90 degrees when the external magnetic field is zero, and the largest change in magnetoresistance can be obtained as described above. preferable. However, the cost for the process of giving the anisotropy in the short axis direction is increased. Further, there is a possibility that the anisotropy in the short axis direction varies and noise increases.

  It is preferable to use an FeCo alloy or a Heusler alloy for the free layer 233 and the pinned layer 231 because a high spin polarization is obtained and a resistance change rate is increased. As a method for increasing the crystal magnetic anisotropy of the fixed layer 231, alloys such as CoPt and CoPd, or ordered phase alloys such as FePt, CoPt, and CoPd, or Co / Pd, Co / Pt, and Co / Ni The use of a so-called artificial lattice film in which ultra-thin magnetic layers are stacked in multiple layers is used.

  Next, a method of fixing the magnetization of the fixed layer 231 when the magnetic field detection unit 11 of the third example shown in FIG. 20 is used will be described.

  As a method of directing the magnetization of the pinned layer 231 in one direction (the direction of arrow 234), for example, as shown in FIG. 21, an antiferromagnetic layer 242 is provided below a pinned layer 231 via a Ru layer 241 having a thickness of 2 nm or less. Is provided.

  This is generally called antiferromagnetic material pinning, and exchange-couples the magnetization of the outermost surface of the antiferromagnetic layer 242 and the magnetization of the fixed layer 231. It is difficult to rotate the magnetization in the antiferromagnetic layer 242 by an external magnetic field, and the magnetization of the pinned layer 231 is strongly exchange-coupled to it, so that the magnetization is kept in one direction (the direction of the arrow 234). You. The exchange magnetic field from the antiferromagnetic layer 242 can be aligned in one direction, for example, by performing heat treatment in a magnetic field.

  The Ru layer 241 is used for antiferromagnetic exchange coupling between the magnetization of the outermost surface of the antiferromagnetic layer 242 and the lowermost surface of the fixed layer 231 and for controlling the exchange coupling strength. However, the pinned layer 231 may be directly laminated on the antiferromagnetic layer 242 without using the Ru layer 241. This has the advantage of simplifying the structure. However, it may be difficult to control the exchange coupling, and it may be difficult to obtain a stable exchange coupling magnetic field. Instead of the Ru layer, a Rh layer or a Cu layer may be used.

  As the antiferromagnetic material used for the pinning layer (antiferromagnetic layer) 242, IrMn is preferable because it can stably maintain the antiferromagnetic state.

  Next, the configuration of the first magnetic layer 221 and the second magnetic layer 223 shown in FIG. 19 will be described in detail with reference to FIG. FIG. 22 is a cross-sectional view illustrating an example of the magnetic field detection unit 11.

  As shown in FIG. 22, the first magnetic layer 221 has a structure in which a soft magnetic high electric resistance layer 253a and a soft magnetic low electric resistance layer 251a are laminated via a Ru layer 252a. The soft magnetic high electric resistance layer 253a and the soft magnetic low electric resistance layer 251a are anti-ferromagnetic exchange-coupled via the Ru layer 252a. Further, the second magnetic layer 223 has a structure in which a soft magnetic low electric resistance layer 251b and a soft magnetic high electric resistance layer 253b are stacked via a Ru layer 252b. The soft magnetic low electric resistance layer 251b and the soft magnetic high electric resistance layer 253b are antiferromagnetic exchange-coupled via the Ru layer 252b. The soft magnetic low electric resistance layers 251 a and 251 b are provided on the nonmagnetic conductive layer 232 side.

  Next, the free layer 233 shown in FIG. 21 will be described with reference to FIG. FIG. 23 is a cross-sectional view illustrating an example of the magnetic field detection unit 11. As shown in FIG. 23, the free layer 233 has a structure in which a soft magnetic low electric resistance layer 251 and a soft magnetic high electric resistance layer 253 are laminated via a Ru layer 252. The soft magnetic low electric resistance layer 251 and the soft magnetic high electric resistance layer 253 are antiferromagnetic exchange-coupled via the Ru layer 252.

  The free layer 233 shown in FIG. 20 also has a structure in which the soft magnetic low electric resistance layer 251 and the soft magnetic high electric resistance layer 253 are laminated via the Ru layer 252, as in the case shown in FIG. The structure may be such that the soft magnetic low electric resistance layer 251 and the soft magnetic high electric resistance layer 253 are antiferromagnetic exchange-coupled via the Ru layer 252.

  In the CIP-GMR using the first magnetic layer 221, the second magnetic layer 223, or the free layer 233, conduction electrons are transferred to the nonmagnetic conductive layer 232 and the soft magnetic layers above and below the nonmagnetic conductive layer 232 (the first magnetic layer 221, the second magnetic layer 223). The scattering at the interface with the layer 223 or the free layer 233) causes a change in magnetoresistance. At this time, if the thickness of the soft magnetic layer (first magnetic layer 221, second magnetic layer 223, or free layer 233) is increased, noise due to thermal fluctuation can be reduced, and the sensitivity of the magnetic sensor can be reduced. Can be enhanced.

  However, when the thickness of the soft magnetic layer is increased, a large amount of current also flows inside the soft magnetic layer, and the efficiency of the magnetoresistance change is reduced. Therefore, when the electric resistance of the soft magnetic layer is increased, electrons hardly enter from the interface of the soft magnetic material, and the resistance change rate does not increase. For this reason, a soft magnetic low electric resistance layer having a structure in which the soft magnetic low electric resistance layers 251a, 251b, 251 and the soft magnetic high electric resistance layers 253a, 253b, 253 are laminated via the Ru layers 252a, 252b, 252 is used. If 251a, 251b, and 251 are in contact with the nonmagnetic conductive layer 232, the conduction electrons enter the soft magnetic low electric resistance layers 251a, 251b, and 251 from the interface and are scattered. However, the light is reflected at the interface with the soft magnetic high electric resistance layers 253a, 253b, and 253 and reaches the interface with the nonmagnetic conductive layer 232 again. As a result, the number of scattering increases and the resistance change rate can be increased.

  On the other hand, since the soft magnetic low electric resistance layers 251a, 251b, and 251 are exchange-coupled with the soft magnetic high electric resistance layers 253a, 253b, and 253 via the Ru layer 252, the rotation of magnetization occurs integrally, and thus Therefore, noise due to thermal fluctuation can be reduced.

  By using an FeCo alloy or a Heusler alloy as a material of the soft magnetic low electric resistance layers 251 a, 251 b, and 251, the spin polarization at the interface with the nonmagnetic conductive layer 232 can be increased. Is preferred. In addition, as a material of the soft magnetic high electric resistance layers 253a, 253b, and 253, an amorphous alloy containing CoFeSi, CoFeSiB, CoZrNb, and CoFeB is preferable because good soft magnetic characteristics can be obtained.

(Method of manufacturing magnetic sensor)
Next, a method for manufacturing the magnetic sensor 1 according to the first embodiment will be described with reference to FIGS. 24A to 24C are plan views showing a manufacturing method. FIGS. 25A to 26B are cross-sectional views taken along a cutting line 271 shown in FIGS. 24B and 24C.

  First, as shown in FIG. 25A, an underlayer 282 having desired characteristics, a magnetoresistive layer 11A, and a protective layer 283 are formed on a substrate 281. The underlayer 282 is appropriately used for the purpose of controlling the crystallinity and magnetic properties of the magnetoresistive layer 11A and improving the adhesion. The protective layer 283 is deposited for the purpose of suppressing damage to the magnetoresistive layer 11A during the process or protecting the magnetic sensor after the formation of the magnetic sensor.

  After that, a resist 284 is applied on the protective layer 283, and exposure and development are performed to form a mask pattern made of the resist 284. Using this mask pattern, the protective layer 283, the magnetoresistive layer 11A, and the underlayer 282 are etched and patterned into a desired shape. FIGS. 24A and 25A are a plan view and a cross-sectional view showing the state after the patterning is performed. As shown in FIG. 24A, the magnetoresistive layer 11A is processed into a belt shape. In general, when an etching process is performed through a mask, it is processed into a trapezoidal shape. FIG. 25A shows this state.

  Next, the non-magnetic insulator 12, the magnetic field converging body 13, and the insulating protective layer 285 are formed in this order while leaving the resist after patterning. This state is shown in FIG. The insulating protective layer 285 is deposited in order to suppress damage during a process such as processing of a magnetic field converging body, which will be described later, and to prevent an unintended electrical short circuit.

  After that, the resist 284 is peeled off, and the nonmagnetic insulator 12, the magnetic field converging body 13, and the insulating protective layer 285 deposited on the magnetoresistive layer 11A are removed by a lift-off method. Subsequently, burrs and residues are removed by polishing, and the surface is flattened. This state is shown in FIGS. 24 (b) and 25 (c). As described above, since the patterned magnetoresistive layer 11A has a trapezoidal cross-sectional shape, the nonmagnetic insulator 12, the magnetic field concentrator 13, and the insulating protection layer 285 are deposited on the side walls. After the lift-off, as shown in FIG. 24B, the non-magnetic insulator 12 and the magnetic field converging body 13 appear outside the end of the magnetoresistive layer 11A. In FIG. 24B, the shape of the insulating protective layer 285 is omitted to facilitate the following description.

  Subsequently, a resist 286 is applied again on the magnetic field converging body 13 and the insulating protective film 285 to shape the magnetic field converging body 13. The resist 286 is exposed and developed into a desired shape using a lithography technique to form a resist mask. This state is shown in FIG. An etching process is performed through the resist mask 286, the magnetic field converging body 13 is processed, and the resist mask 286 is removed. This state is shown in FIGS. 24 (c) and 26 (b).

  By using the above processing process, the distance between the magnetoresistive layer 11A and the magnetic field converging body 13 can be controlled by the thickness of the nonmagnetic insulator 12 formed. Thereby, the range of several nm to 50 nm required for the magnetic sensors of the first and second embodiments can be easily controlled. Further, as can be seen from FIGS. 24A to 26B, by providing an appropriate underlayer and a protective layer on the magnetoresistive layer 11A, the thickness of the magnetoresistive layer 11A can be made smaller than that of the magnetic field converging body 13. In addition, since the magnetoresistive layer 11A can be disposed substantially at the center of the magnetic field converging body 13 in the thickness direction, the leakage magnetic field generated from the magnetic charge at the end of the magnetoresistive layer 11A can be effectively reduced. The demagnetizing field can be suppressed to a low level by being absorbed by the magnetic field converging body 13.

  When the magnetoresistive layer 11A is processed into the shape shown in FIG. 14 or FIG. 15, in the process shown in FIG. 24A, it is processed so as to have the shape of the magnetoresistive layer 11A shown in FIG. 14 or FIG. A mask is set, and in the process shown in FIGS. 26A and 26B, a processing mask that allows the magnetic field converging body 13 to be formed only outside the outermost magnetoresistive layer 11A may be used.

  In FIG. 24C, the nonmagnetic insulator 12 is also provided on the end face on the short axis side of the magnetoresistive layer 11A. When connecting a conducting wire for applying a current to the magnetoresistive layer 11A, the nonmagnetic insulator 12 may be avoided or a part thereof may be deleted. The schematic diagram of FIG. 1 schematically shows a state after such measures are taken.

(Estimation of noise level)
Next, the noise level of the magnetic sensor according to the third embodiment was estimated. 27 (a) and 27 (b) show the results. FIG. 27A schematically shows an outline of an assumed magnetic sensor.

This magnetic sensor has a configuration using a CIP-GMR element 171 shown in FIG. The CIP-GMR element 171 has dimensions of 4 μm in width, 800 μm in length, and 15 nm in thickness. The length of the magnetic field converging bodies 13a and 13b on the side of the magnetic field detecting section 11 was 800 μm, the length on the opposite side was 10 mm, the thickness was 600 nm, and the magnification of the magnetic field intensity was 400 times. It is assumed that the resistance R of the magnetic field detector 11 is 4 kΩ (Johnson noise: 〜6 nV), the applied voltage Vb is 1.2 V (0.36 mW), and the resistance change rate (dR / R) is 20%. From the AMR literature value, the noise at 1 Hz (1 / f noise + Johnson noise) was set to 50 nV / Hz ^0.5 .

  As shown in FIGS. 10 and 11, the distance between the magnetic field detection unit 11 and the magnetic field converging body 13 is set to 50 nm or less, that is, 1/2 or less of the length of the magnetic field detection unit 11 in the short axis direction. Thereby, the saturation magnetic field Hk (the reciprocal of the sensitivity) can be reduced to about half. Based on this result, it was assumed that 2 × Hk was reduced to 80, 40, 20, and 10 Oe by gradually reducing the distance between the magnetic field detection unit 11 and the magnetic field converging body 13. In the calculations of FIGS. 10 and 11, the ratio of the long axis to the short axis of the soft magnetic material was 10, but in the present estimation, it was 200, so the reduction rate of the saturation magnetic field Hk is expected to be larger. Not considered. The horizontal axis represents this 2 × Hk, and the vertical axis plots the output voltage per pT (picotesla) and the magnetic field strength at which the signal output matches the noise level, that is, the limit detection magnetic field strength D in FIG. 27B. As can be seen from FIG. 27B, it was found that detection of a magnetic field of less than 1 pT can be expected. This result is, as described above, that the use of the magnetic sensors according to the first to third embodiments achieves a reduction in noise and an increase in sensitivity.

(Fourth embodiment)
Next, the magnetic sensor according to any of the first to third embodiments can be used for a magnetoencephalograph that detects a magnetic field generated by a cranial nerve. This will be described as a fourth embodiment.

  A magnetic sensor device according to a fourth embodiment will be described with reference to FIG. The magnetic sensor device 100 of the fourth embodiment is a magnetoencephalograph, and the diagram on the left side of FIG. 28 schematically shows a state where the magnetoencephalograph 100 is mounted on the head of a human body. The magnetoencephalograph 100 has a configuration in which a plurality of sensor units, for example, about 100 sensor units 301 are installed on a flexible base 302.

  In the sensor unit 301, one magnetic sensor according to any of the first to third embodiments and their modifications may be provided, or a plurality of magnetic sensors may be provided. A plurality of magnetic sensors may constitute a circuit for differential detection or the like, or another sensor such as a potential terminal or an acceleration sensor may be installed at the same time. The magnetic sensor according to any one of the first to third embodiments and their modifications can be made very small as compared with a conventional SQUID magnetic sensor. Coexistence with other sensors is also easy.

  The flexible base 302 is made of, for example, an elastic body such as a silicone resin, and is configured so as to connect the sensor portions 301 in a belt shape and to be in close contact with the head. The base 302 may be formed by processing a continuous film into a hat shape, but a net shape as shown in FIG. 28 is preferable because it has good mounting properties and improves the adhesion to the human body.

  The input / output code 303 of the sensor unit 301 is connected to the sensor drive unit 506 and the signal input / output unit 504 of the diagnostic device 500. The sensor unit 301 performs a predetermined magnetic field measurement based on the power from the sensor driving unit 506 and the control signal from the signal input / output unit 504, and the result is input to the signal input / output unit 504 in parallel. The signal obtained by the signal input / output unit 504 is then sent to a signal processing unit 508, where the signal processing unit 508 performs processing such as noise removal, filtering, amplification, and signal calculation. After that, the signal analysis unit 510 performs signal analysis on these signals, such as extracting a specific signal for magnetoencephalography measurement and adjusting the signal phase. The data for which the signal analysis has been completed is sent to the data processing unit 512. The data processing unit 512 also incorporates image data such as MRI (Magnetic Resonance Imaging) and scalp potential information such as EEG (Electroencephalogram) and performs data analysis such as nerve firing point analysis and inverse problem analysis. The result is sent to the imaging diagnosis unit 516, and imaging is performed to assist diagnosis. These series of operations are controlled by the control mechanism 502, and necessary data such as primary signal data and metadata during data processing are stored in the data server. Note that the data server and the control mechanism may be integrated as shown in FIG.

  In the fourth embodiment shown in FIG. 28, the sensor unit 301 is installed on the head of the human body, but if it is installed on the chest of the human body, the magnetocardiography can be measured. Moreover, if it is installed on the abdomen of a pregnant woman, it can be used for a heart rate test of a fetus.

  The entire magnetic sensor device including the subject is preferably installed in a shield room to prevent geomagnetism and magnetic noise. Alternatively, a mechanism for locally shielding the measurement site of the human body and the sensor unit 301 may be provided. Further, a shield mechanism may be provided in the sensor unit 301, or an effective shield may be performed by signal analysis or data processing.

  In the magnetic sensor 100 shown in FIG. 28, a sensor unit 301 having a high-sensitivity magnetic sensor is installed on a flexible base 302, but is installed on a fixed base like a conventional magnetoencephalograph or magnetocardiograph. It does not matter. The example is shown in FIG. 29 and FIG. FIG. 29 shows an example of a magnetoencephalograph, in which a sensor unit 301 is provided on a hard base 304 having a helmet shape. FIG. 30 shows an example of a magnetocardiograph, in which a sensor section 301 is provided on a flat rigid base 305. In any case, the input and output of signals from the sensor unit 301 and the processing are the same as those in FIG.

(Sensor part)
As an embodiment of the sensor unit 301 in the magnetoencephalograph or the magnetocardiograph, a plurality of magnetic sensors may be connected in a bridge. This embodiment is shown in FIG. The four magnetic field detectors 11 are arranged on a rectangle, and each magnetic field detector 11 is bridge-connected as shown in FIG. 31 to detect a magnetic field in the direction of arrow 17. The upper left and lower right magnetic field detectors 11 in FIG. 31 constitute a magnetic sensor according to any of the first to third embodiments and their modifications. A nonmagnetic insulator 12 is provided so as to sandwich the magnetic field detection unit 11, and a magnetic field converging body 13 is provided on the opposite side of the nonmagnetic insulator 12 from the magnetic field detection unit 11.

  As described above, the magnetic sensor provided with the magnetic field converging body 13 produces an output signal that is orders of magnitude larger than the case where no magnetic field converging body is provided due to the enhancement effect of the measured magnetic field. Therefore, in FIG. 31, the upper left and lower right magnetic field detectors 11 change their resistance according to the measured magnetic field, but the lower left and upper right magnetic field detectors 11 have fixed resistances whose resistance does not substantially change according to the measured magnetic field. Becomes

  When a measurement magnetic field is applied in the configuration of FIG. 31, the upper left and lower right magnetic field detectors 11 of FIG. 31 change, and the voltage detected by the voltage detector 600 obtains an output twice as large as the voltage change of a single unit. be able to. On the other hand, since the detection voltage is not the voltage of the magnetic field detection unit 11 but the potential difference between the right and left blocks 600 in FIG. 31, the noise inherent in the current source 650 is canceled. That is, the output can be increased while suppressing noise.

  Although several embodiments of the present invention have been described, these embodiments are provided by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in other various forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the invention described in the claims and their equivalents.

  1, 1A, 1B, 1C: magnetic sensor, 11: magnetic field detector, 11A: magnetoresistive layer, 12, 12a, 12b: non-magnetic insulator, 13, 13a, 13b ... Magnetic field converging body, 14 ... End face of magnetic field converging body on magnetoresistive layer side, 15 ... End face of magnetic field converging body on opposite side of magnetoresistive layer, 16 ... Detector circuit, 17 ... Measurement magnetic field , 21 ... magnetoresistive layer, 22 ... magnetization in magnetoresistance layer, 23 ... long-axis end face of magnetoresistance layer, 24a, 24b ... magnetic charge generated by rotation of magnetization , 25... End of the magnetoresistive layer, 161 a, 161 b... Conductor, 171... Perpendicularly conducting magnetoresistive element, 181... Fixed layer, 182. ..Free layer, 184... Conducting wire, 211... Magnetoresistive layer, 212... 221: a first magnetic layer made of a soft magnetic material; 222: a nonmagnetic conductive layer; 223: a second magnetic layer made of a soft magnetic material; 231, a fixed layer; Magnetic conductive layer, 233 free layer, 234 long axis direction, 241 Ru layer, 242 antiferromagnetic layer, 251a, 251b soft magnetic low electric resistance layer, 252 ..Ru layer, 253a, 253b: soft magnetic high electric resistance layer, 281: substrate, 282: base layer, 283: protective layer, 284: resist, 285: insulation protection Layer, 286 resist, 301 sensor part, 302 base, 303 input / output code, 304 base, 305 base

Claims (1)

The length of the first direction is at least 10 times the length of the second direction orthogonal to the first direction, and the length of the third direction orthogonal to the first direction and the second direction is the length of the second direction. A magnetic field detector having a magnetic layer that is not more than half the length;
A first magnetic member that is arranged along the first direction of the magnetic field detection unit and has a length in the third direction longer than a length of the magnetic layer in the third direction;
A first non-magnetic insulating layer disposed between the magnetic field detector and the first magnetic member, wherein the length in the second direction is not more than half the length of the magnetic layer in the second direction; When,
A circuit for passing a current through the magnetic layer;
Magnetic sensor provided with.