Magnetic sensor

Abstract

To improve sensibility compared with a case where widths in a short direction of a sensing element are the same from one end to the other end in a longitudinal direction in a magnetic sensor using a magnetic impedance effect.SOLUTION: A magnetic sensor includes: a nonmagnetic substrate; and a sensing element that is provided on the substrate, is composed of a soft magnetic material, has a longitudinal direction and a short direction, has uniaxial magnetic anisotropy in a direction crossing the longitudinal direction, has a smaller width of a center portion in the longitudinal direction than those of both ends in the longitudinal direction, and senses a magnetic field by a magnetic impedance effect.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a magnetic sensor.

Background Art

[0002] As a conventional technique described in a publication, there is a magnetic impedance effect element including a magnetosensitive portion composed of a plurality of soft magnetic films imparted with uniaxial anisotropy (see Patent Document 1). The magnetosensitive portion of this magnetic impedance effect element has a rectangular shape with the same width in the short side direction from one end to the other end in the longitudinal direction.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a magnetic sensor including a sensing element having a longitudinal direction and a short side direction and sensing a magnetic field by a magnetic impedance effect, when the width in the short side direction of the sensing element is equal from one end to the other end in the longitudinal direction, the sensitivity may be insufficient. An object of the present invention is to improve the sensitivity in a magnetic sensor using a magnetic impedance effect as compared with a case where the width in the short side direction of a sensing element is equal from one end to the other end in the longitudinal direction.

Means for Solving the Problems

[0005] The magnetic sensor to which the present invention is applied includes a non-magnetic substrate, and is provided on the substrate, made of a soft magnetic material, having a longitudinal direction and a short side direction, having uniaxial magnetic anisotropy in a direction intersecting the longitudinal direction, and having a smaller width at the central portion in the longitudinal direction than both end portions in the longitudinal direction. Using the change in impedance in a magnetic field range where the absolute value is smaller than the magnetic field at which the impedance takes a maximum value in a curve representing the relationship between the magnetic field and impedance, It includes a sensing element that senses changes in a magnetic field due to the magneto-impedance effect, and the ratio of the width of the sensing element at both longitudinal ends to the width of the sensing element at the central portion in the longitudinal direction is in the range of 100:68 to 100:78. Also, the sensing element can be characterized in that the width in the short-side direction continuously decreases from both longitudinal ends to the central portion in the longitudinal direction. Also, it can be characterized in that it includes a plurality of the sensing elements arranged with a gap in the short-side direction, and a connecting portion that connects the longitudinal ends of the sensing elements adjacent in the short-side direction and whose width in the short-side direction becomes narrower as it approaches the sensing element along the longitudinal direction.

Advantages of the Invention

[0006] According to the present invention, in a magnetic sensor using the magneto-impedance effect, the sensitivity can be improved as compared with the case where the width in the short-side direction of the sensing element is equal from one end to the other end in the longitudinal direction.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIGS. 1 and 2 are diagrams for explaining an example of the magnetic sensor 1 to which the present embodiment is applied. FIG. 1 is a plan view, and FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1. As shown in FIG. 2, the magnetic sensor 1 to which the present embodiment is applied includes a thin film magnet 20 composed of a hard magnetic material (hard magnetic layer 103) provided on a non-magnetic substrate 10, and a soft magnetic material (lower soft magnetic layer 105a, upper soft magnetic layer 105b) laminated facing the thin film magnet 20. And a sensing unit 30 composed of a conductor layer (high conductivity layer 106) having higher conductivity than the soft magnetic layer 105 and sensing a magnetic field. In the following description, when the two-layer soft magnetic layers (lower soft magnetic layer 105a and upper soft magnetic layer 105b) are not distinguished from each other, they are simply referred to as the soft magnetic layer 105. The cross-sectional structure of the magnetic sensor 1 will be described in detail later.

[0009] Here, a hard magnetic material is a material with a so-called large coercive force that, when magnetized by an external magnetic field, retains the magnetized state even when the external magnetic field is removed. On the other hand, a soft magnetic material is a material with a so-called small coercive force that is easily magnetized by an external magnetic field but quickly returns to a state where there is no magnetization or the magnetization is small when the external magnetic field is removed.

[0010] In this specification, elements (such as the thin film magnet 20) constituting the magnetic sensor 1 are represented by two-digit numbers, and layers (such as the hard magnetic layer 103) processed on the elements are represented by three-digit numbers. And the number of the layer processed on the element is indicated in parentheses with respect to the number of the element. For example, in the case of the thin film magnet 20, it is denoted as the thin film magnet 20 (hard magnetic layer 103). In the figure, it is denoted as 20(103). The same applies to other cases.

[0011] The planar structure of the magnetic sensor 1 will be described with reference to Fig. 1. The magnetic sensor 1 has a rectangular planar shape as an example. Here, the sensing part 30 and the yoke 40 formed on the uppermost part of the magnetic sensor 1 will be described. The sensing part 30 includes a plurality of sensing elements 31 having a strip shape with a longitudinal direction and a lateral direction in the planar shape, a connecting part 32 that serially connects adjacent sensing elements 31 in a zigzag manner, and a terminal part 33 to which an electric wire for current supply is connected. Here, eight sensing elements 31 are arranged in the lateral direction with a gap therebetween so that the longitudinal directions are parallel. In the magnetic sensor 1 of the present embodiment, the sensing element 31 is a magnetic impedance effect element.

[0012] The connecting part 32 is provided between the longitudinal ends of adjacent sensing elements 31 and serially connects the adjacent sensing elements 31 in a zigzag manner. In the magnetic sensor 1 shown in Fig. 1, since eight sensing elements 31 are arranged in parallel, there are seven connecting parts 32. Note that the planar shapes of the sensing element 31 and the connecting part 32 will be described in detail later.

[0013] The terminal parts 33 are respectively provided at two ends of the sensing element 31 not connected by the connecting part 32. The terminal part 33 includes a lead-out part that leads out from the sensing element 31 and a pad part to which an electric wire for supplying current is connected. The lead-out part is provided to provide two pad parts in the lateral direction of the sensing element 31. The pad part may be provided continuously to the sensing element 31 without providing the lead-out part. The pad part may have any size as long as it can connect an electric wire. Since there are eight sensing elements 31, the two terminal parts 33 are provided on the right side in Fig. 1. When the number of sensing elements 31 is odd, the two terminal parts 33 may be provided separately on the left and right.

[0014] Then, the sensing element 31, the connecting part 32, and the terminal part 33 of the sensing part 30 are integrally formed by two layers of soft magnetic layers 105 (lower soft magnetic layer 105a, upper soft magnetic layer 105b) and a high conductive layer 106. Since the soft magnetic layer 105 and the high conductive layer 106 are conductive, current can flow from one terminal part 33 to the other terminal part 33. Note that the above-described numerical values such as the length, width, and number of the sensing elements 31 arranged in parallel are merely examples, and may be changed depending on the value of the magnetic field to be sensed (measured), the soft magnetic material used, etc.

[0015] Furthermore, the magnetic sensor 1 includes a yoke 40 provided to face an end portion in the longitudinal direction of the sensing element 31. Here, it includes two yokes 40a and 40b provided to face both end portions in the longitudinal direction of the sensing element 31, respectively. When not distinguishing between the yokes 40a and 40b, they are denoted as the yoke 40. The yoke 40 guides magnetic field lines to the end portion in the longitudinal direction of the sensing element 31. For this reason, the yoke 40 is configured to include a soft magnetic material (soft magnetic layer 105) through which magnetic field lines easily pass. In this example, the sensing portion 30 and the yoke 40 are composed of two layers of soft magnetic layers 105 (lower soft magnetic layer 105a, upper soft magnetic layer 105b) and a high-conductivity layer 106. Note that when magnetic field lines sufficiently pass in the longitudinal direction of the sensing element 31, the yoke 40 may not be provided.

[0016] From the above, the size of the magnetic sensor 1 is several mm square in planar shape. Note that the size of the magnetic sensor 1 may be other values.

[0017] Next, with reference to FIG. 2, the cross-sectional structure of the magnetic sensor 1 will be described in detail. The magnetic sensor 1 is configured by laminating, in this order, a thin film magnet 20 composed of an adhesion layer 101, a control layer 102, and a hard magnetic layer 103, a dielectric layer 104, a sensing portion 30 composed of a soft magnetic layer 105 and a high-conductivity layer 106, and a yoke 40 on a non-magnetic substrate 10.

[0018] The substrate 10 is a substrate made of a non-magnetic material, and examples thereof include oxide substrates such as glass and sapphire, semiconductor substrates such as silicon, or metal substrates such as metals such as aluminum, stainless steel, and nickel-plated metal. The adhesion layer 101 is a layer for improving the adhesion of the control layer 102 to the substrate 10. As the adhesion layer 101, an alloy containing Cr or Ni is preferably used. Examples of the alloy containing Cr or Ni include CrTi, CrTa, NiTa, etc. The thickness of the adhesion layer 101 is, for example, 5 nm to 50 nm. If there is no problem with the adhesion of the control layer 102 to the substrate 10, it is not necessary to provide the adhesion layer 101. In this specification, the composition ratio of the alloy containing Cr or Ni is not shown. The same applies hereinafter.

[0019] The control layer 102 is a layer that controls so that the magnetic anisotropy of the thin film magnet 20 composed of the hard magnetic layer 103 is likely to be expressed in the in-plane direction of the film. As the control layer 102, Cr, Mo, or W or an alloy containing them (hereinafter, referred to as an alloy containing Cr, etc. constituting the control layer 102) is preferably used. Examples of the alloy containing Cr, etc. constituting the control layer 102 include CrTi, CrMo, CrV, CrW, etc. The thickness of the control layer 102 is, for example, 10 nm to 300 nm.

[0020] The hard magnetic layer 103 constituting the thin film magnet 20 is preferably made of an alloy containing Co as a main component and either one or both of Cr and Pt (hereinafter, referred to as a Co alloy constituting the thin film magnet 20). Examples of the Co alloy constituting the thin film magnet 20 include CoCrPt, CoCrTa, CoNiCr, CoCrPtB, etc. Note that Fe may be contained. The thickness of the hard magnetic layer 103 is, for example, 1 μm to 3 μm.

[0021] The alloy containing Cr or the like that constitutes the control layer 102 has a bcc (body-centered cubic) structure. Therefore, the hard magnetic material (hard magnetic layer 103) that constitutes the thin film magnet 20 is preferably an hcp (hexagonal close-packed) structure that easily crystallizes on the control layer 102 composed of an alloy containing Cr or the like having a bcc structure. When the hard magnetic layer 103 having an hcp structure is crystallized on the bcc structure, the c-axis of the hcp structure is likely to be oriented in the plane. Therefore, the thin film magnet 20 composed of the hard magnetic layer 103 is likely to have magnetic anisotropy in the in-plane direction. Note that the hard magnetic layer 103 is a polycrystal composed of aggregates with different crystal orientations, and each crystal has magnetic anisotropy in the in-plane direction. This magnetic anisotropy is derived from crystal magnetic anisotropy. In order to promote the crystal growth of the alloy containing Cr or the like that constitutes the control layer 102 and the Co alloy that constitutes the thin film magnet 20, it is preferable to heat the substrate 10 to 100°C to 600°C. By this heating, the alloy containing Cr or the like that constitutes the control layer 102 becomes likely to crystallize, and the hard magnetic layer 103 having an hcp structure is likely to be crystal-oriented so as to have an easy magnetization axis in the plane. That is, magnetic anisotropy is likely to be imparted in the plane of the hard magnetic layer 103.

[0022] The dielectric layer 104 is composed of a non-magnetic dielectric and electrically insulates between the thin film magnet 20 and the sensing unit 30. Examples of the dielectric that constitutes the dielectric layer 104 include oxides such as SiO2, Al2O3, and TiO2, or nitrides such as Si3N4 and AlN. Further, the thickness of the dielectric layer 104 is, for example, 0.1 μm to 30 μm.

[0023] Uniaxial magnetic anisotropy is imparted to the sensing element 31 of the sensing unit 30 in a direction intersecting the longitudinal direction, for example, in the short-side direction orthogonal to the longitudinal direction (that is, the width direction of the sensing element 31). Note that the direction intersecting the longitudinal direction may have an angle exceeding 45° with respect to the longitudinal direction. As the soft magnetic material (lower soft magnetic layer 105a, upper soft magnetic layer 105b) constituting the sensing part 30, it is preferable to use an amorphous alloy in which a high melting point metal such as Nb, Ta, or W is added to an alloy mainly composed of Co (hereinafter referred to as the Co alloy constituting the sensing part 30). Examples of the Co alloy constituting the sensing part 30 include CoNbZr, CoFeTa, and CoWZr. The thickness of the soft magnetic material (lower soft magnetic layer 105a, upper soft magnetic layer 105b) constituting the sensing element 31 is, for example, 0.2 μm to 2 μm respectively. In the example shown in FIG. 2, the thickness of the lower soft magnetic layer 105a and the thickness of the upper soft magnetic layer 105b are equal to each other, but they may be different from each other. Here, although the sensing element 31, the connecting part 32, and the terminal part 33 of the sensing part 30 are made of the same material, they may be made of different materials from each other. For example, a material with higher conductivity than the sensing element 31 may be used for the connecting part 32 and the terminal part 33. In this case, the resistance in the connecting part 32 and the terminal part 33 can be reduced.

[0024] As the conductor (high-conductivity layer 106) constituting the sensing element 31, it is preferable to use a metal or alloy with high conductivity, and more preferably a metal or alloy with high conductivity and non-magnetic properties. Specifically, as the conductor (high-conductivity layer 106) constituting the sensing element 31, it is preferable to use a metal such as aluminum, copper, or silver. The thickness of the conductor (high-conductivity layer 106) constituting the sensing element 31 is, for example, 10 nm to 500 nm. The thickness of the conductor (high-conductivity layer 106) constituting the sensing element 31 can be changed depending on the type of Co alloy constituting the sensing element 31 used as the soft magnetic layer 105, the conductor used as the high-conductivity layer 106, and the like.

[0025] The adhesion layer 101, the control layer 102, the hard magnetic layer 103, and the dielectric layer 104 are processed so that their planar shape is rectangular (see Fig. 1). Among the exposed side surfaces, on two opposing side surfaces, the thin film magnet 20 has an N pole ((N) in Fig. 2) and an S pole ((S) in Fig. 2). Note that the line connecting the N pole and the S pole of the thin film magnet 20 is oriented in the longitudinal direction of the sensing element 31. Here, being oriented in the longitudinal direction means that the angle formed by the line connecting the N pole and the S pole and the longitudinal direction is less than 45°. Note that the smaller the angle formed by the line connecting the N pole and the S pole and the longitudinal direction, the better.

[0026] In the magnetic sensor 1, the magnetic flux lines emerging from the N pole of the thin film magnet 20 once exit the magnetic sensor 1. Then, some of the magnetic flux lines pass through the sensing element 31 via the yoke 40a and exit to the outside again via the yoke 40b. Then, the magnetic flux lines that have passed through the sensing element 31 return to the S pole of the thin film magnet 20 together with the magnetic flux lines that have not passed through the sensing element 31. That is, the thin film magnet 20 applies a magnetic field (a bias magnetic field Hb described later) in the longitudinal direction of the sensing element 31. Note that when the N pole and the S pole of the thin film magnet 20 are collectively referred to as both poles without distinguishing between the N pole and the S pole, they are referred to as magnetic poles.

[0027] As shown in Fig. 1, the yoke 40 (yokes 40a and 40b) is configured such that its shape as viewed from the surface side of the substrate 10 becomes narrower as it approaches the sensing portion 30. This is to concentrate the magnetic field (collect the magnetic flux lines) in the sensing portion 30. That is, the magnetic field in the sensing portion 30 is strengthened to further improve the sensitivity. Note that it is not necessary to narrow the width of the portion of the yoke 40 (yokes 40a and 40b) facing the sensing portion 30.

[0028] Here, the distance between the yoke 40 (yokes 40a and 40b) and the sensing portion 30 may be, for example, 1 μm to 100 μm.

[0029] Next, the planar shape of the sensing element 31 will be described in detail. FIG. 3 is an enlarged view of part III in FIG. 1. Note that the ratio of the longitudinal direction to the lateral direction of the sensing element 31 shown in FIG. 3 is not necessarily accurate. The plurality of sensing elements 31 have the same planar shape as each other. Each sensing element 31 has a strip shape having a longitudinal direction and a lateral direction. Further, in each sensing element 31, the width in the lateral direction is different between both ends in the longitudinal direction and the central portion in the longitudinal direction. In the description of the present embodiment, the width in the lateral direction of the sensing element 31 may be simply referred to as "the width of the sensing element 31" or the like.

[0030] As shown in FIG. 3, in the present embodiment, the width D2 of the sensing element 31 at the central portion in the longitudinal direction is smaller than the width D1 of the sensing element 31 at both ends in the longitudinal direction. Specifically, in each sensing element 31, the width in the lateral direction continuously decreases from both ends in the longitudinal direction toward the central portion in the longitudinal direction.

[0031] Furthermore, as shown in FIG. 3, each sensing element 31 extends along the longitudinal direction and has two long side portions 31a and 31b facing each other in the lateral direction. In each sensing element 31, the distance between the two long side portions 31a and 31b becomes narrower from both ends in the longitudinal direction toward the central portion in the longitudinal direction. In this example, the long side portion 31a of each sensing element 31 has a curved shape that is concave toward the long side portion 31b so that the distance from one end to the other end in the longitudinal direction continuously changes with respect to the long side portion 31b. Similarly, the long side portion 31b of each sensing element 31 has a curved shape that is concave toward the long side portion 31a so that the distance from one end to the other end in the longitudinal direction continuously changes with respect to the long side portion 31a.

[0032] The length in the longitudinal direction of each sensing element 31 is not particularly limited, but is, for example, about 0.5 mm to 3 mm. Further, the width (D1, D2) in the lateral direction of each sensing element 31 is not particularly limited, but is, for example, about 10 μm to 300 μm. In this embodiment, although it also varies depending on the length in the longitudinal direction of the sensing element 31 and the like, the ratio (D1:D2) of the width D1 of the sensing element 31 at both ends in the longitudinal direction to the width D2 of the sensing element 31 at the central portion in the longitudinal direction is preferably in the range of 100:60 to 100:90. When the width D2 of the sensing element 31 at the central portion in the longitudinal direction is excessively smaller than the width D1 of the sensing element 31 at both ends in the longitudinal direction, the resistance when supplying current to the sensing portion 30 may become high. Also, when the width D1 of the sensing element 31 at both ends in the longitudinal direction and the width D2 of the sensing element 31 at the central portion in the longitudinal direction are approximated, it becomes difficult to obtain the effect of improving the sensitivity described later.

[0033] Subsequently, with reference to FIGS. 1 and 3 described above, the planar shape of the connection portion 32 will be described in detail. As shown in FIG. 3, each connection portion 32 has an extension portion 321 extending along the short side direction. Here, when simply referring to the short side direction or the long side direction, it refers to the short side direction or the long side direction of the sensing element 31. Also, each connection portion 32 has a tapered portion 322 extending in the longitudinal direction from the extension portion 321 and connecting the longitudinal end of the sensing element 31 and the extension portion 321. And the connection portion 32 connects the longitudinal ends of the two sensing elements 31 arranged side by side in the short side direction by the extension portion 321 and the two tapered portions 322.

[0034] The extension portion 321 has a strip-shaped shape extending along the short side direction. And as shown in FIG. 3, the extension portion 321 protrudes in the short side direction with respect to the two sensing elements 31 to be connected. Incidentally, the length of the extension portion 321 in the short side direction is longer than the length obtained by combining the widths of the two sensing elements 31 in the short side direction and the interval between the two sensing elements 31 in the short side direction. Also, it is preferable that the width of the extension portion 321 in the longitudinal direction is larger than the width D1 of the sensing element 31 at both ends in the longitudinal direction. Thereby, compared with the case where the width of the extension portion 321 in the longitudinal direction is smaller than the width D1 of the sensing element 31 at both ends in the longitudinal direction, the resistance when supplying current to the sensing portion 30 becomes lower.

[0035] The tapered portion 322 has a so-called tapered shape in which the width in the short side direction becomes narrower as it approaches the end of the sensing element 31 along the longitudinal direction. Additionally, the tapered portion 322 has two side portions 322a and 322b that extend along the longitudinal direction. And in the tapered portion 322, as it approaches the end of the sensing element 31 along the longitudinal direction, the distance between the two side portions 322a and 322b becomes narrower. Also, in this example, the inclination angles θa and θb formed between each of the side portions 322a and 322b of the tapered portion 322 and the longitudinal direction are 135 degrees. The inclination angles θa and θb vary depending on, for example, the length in the short side direction of the extending portion 321 and the width in the short side direction of the sensing element 31, etc., but can be in the range of, for example, 110 degrees or more and 150 degrees or less.

[0036] In the magnetic sensor 1 of the present embodiment, since the connection portion 32 has the tapered portion 322, it becomes easier to guide the magnetic flux lines to the longitudinal end of the sensing element 31. As a result, in the magnetic sensor 1 of the present embodiment, the magnetic field is concentrated on the sensing element 31 and the magnetic flux density becomes high. Thereby, compared with the case where the connection portion 32 does not have the tapered portion 322, the sensitivity of the magnetic sensor 1 can be improved.

[0037] (Operation of the magnetic sensor 1) Subsequently, the operation of the magnetic sensor 1 of the present embodiment will be described while comparing it with a conventional magnetic sensor (hereinafter simply referred to as the conventional magnetic sensor) whose shape of the sensing element 31 is different from that of the magnetic sensor 1 of the present embodiment. FIG. 4 is a diagram showing the shape of the sensing element 31 in the magnetic sensor 1 (see FIG. 1) and the conventional magnetic sensor, and the magnetic field strength in the sensing element 31 of the magnetic sensor 1 and the conventional magnetic sensor. In FIG. 4, the sensing element 31 and the magnetic field strength of the magnetic sensor 1 of the present embodiment are shown as "Example", and the shape and magnetic field strength of the sensing element 31 of the conventional magnetic sensor are shown as "Comparative Example". Also, in FIG. 4, when an external magnetic field of a predetermined magnitude is applied to the sensing element 31 of the magnetic sensor 1 and the conventional magnetic sensor, the magnetic field strength in the sensing element 31 is shown as a distribution along the longitudinal direction.

[0038] Here, FIG. 4 is obtained by simulation using a computer. Specifically, for the magnetic sensor 1 of the present embodiment having the shapes shown in FIGS. 1 to 3, the sensing portion 30 and the yoke 40 are made of a two-layer soft magnetic layer 105 (lower soft magnetic layer 105a, upper soft magnetic layer 105b) composed of Co 85 Nb 12 Zr3, and a high conductor layer 106 made of Ag with a thickness of 300 nm. In the magnetic sensor 1 of the embodiment, the width D1 of the sensing element 31 at both longitudinal ends is 95 μm, the width D2 of the sensing element 31 at the central portion in the longitudinal direction is 65 μm, and the length along the longitudinal direction of the sensing element 31 is 2 mm. In the magnetic sensor 1 of the embodiment, as shown in FIG. 3 and the like, the long sides 31a and 31b of the sensing element 31 have a curved shape, and the width of the sensing element 31 continuously changes from one end in the longitudinal direction to the other end in the longitudinal direction. Then, when an external magnetic field of 10 Oe is applied along the longitudinal direction to the sensing element 31, the magnetic field strength in the sensing element 31 is calculated by simulation.

[0039] Regarding the conventional magnetic sensor 2, it was made in the same manner as the magnetic sensor 1 of the present embodiment except that the width of the sensing element 31 in the short direction was made constant at 80 μm from one end to the other end in the longitudinal direction. Then, when an external magnetic field of 10 Oe is applied to the sensing element 31, the magnetic field strength applied to the sensing element 31 is calculated by simulation.

[0040] As shown in FIG. 4, the magnetic sensor 1 of the present embodiment, in which the width D2 of the sensing element 31 at the central portion in the longitudinal direction is smaller than the width D1 of the sensing element 31 at both longitudinal ends, has a magnetic field strength in the sensing element 31 that is uniform along the longitudinal direction as compared with the conventional magnetic sensor in which the width of the sensing element 31 is equal from one end to the other end in the longitudinal direction. Specifically, in a conventional magnetic sensor, the magnetic field strengths at both ends in the longitudinal direction of the sensing element 31 are extremely larger than the magnetic field strength at the central portion in the longitudinal direction. In contrast, in the magnetic sensor 1 of the present embodiment, the difference in magnetic field strength between both ends in the longitudinal direction and the central portion in the longitudinal direction of the sensing element 31 is smaller compared to the conventional magnetic sensor.

[0041] Subsequently, as the operation of the magnetic sensor 1 of the present embodiment, the relationship between the magnetic field applied in the longitudinal direction of the sensing element 31 in the sensing unit 30 and the impedance of the sensing unit 30 will be described while comparing with a conventional magnetic sensor. FIGS. 5(a) to 5(b) are diagrams for explaining the relationship between the magnetic field applied in the longitudinal direction of the sensing element 31 and the impedance of the sensing unit 30 for the magnetic sensor 1 of the present embodiment and a conventional magnetic sensor. Note that FIG. 5(b) is an enlarged view of the VB portion in FIG. 5(a).

[0042] In FIGS. 5(a) to 5(b), the horizontal axis represents the magnetic field H and the vertical axis represents the impedance Z. The impedance Z of the sensing unit 30 is measured by passing a high-frequency current between two terminal portions 33. FIGS. 5(a) to 5(b) are the results of measuring the magnetic sensor 1 of the present embodiment and a conventional magnetic sensor by passing a 100 MHz high-frequency current between the terminal portions 33 of the sensing unit 30. In FIGS. 5(a) to 5(b), the magnetic sensor 1 of the present embodiment is shown as "Example 1" to "Example 4", and the conventional magnetic sensor is shown as "Comparative Example". Note that the constituent materials and shapes of the magnetic sensors 1 of Examples 1 to 4 whose characteristics are shown in FIGS. 5(a) to 5(b) are the same as those of the magnetic sensor 1 of the present embodiment whose characteristics are shown in FIG. 4, except for the width of the sensing element 31. Also, the constituent materials and shapes of the conventional magnetic sensors of the Comparative Example whose characteristics are shown in FIGS. 5(a) to 5(b) are the same as those of the conventional magnetic sensor whose characteristics are shown in FIG. 4.

[0043] In the magnetic sensors 1 of Examples 1 to 4, the widths of the sensing element 31 (the width D1 of the sensing element 31 at both longitudinal ends and the width D2 of the sensing element 31 at the longitudinal center) are different from each other. Specifically, in the magnetic sensor 1 of Example 1, the width D1 of the sensing element 31 at both longitudinal ends was 85 μm, and the width D2 of the sensing element 31 at the longitudinal center was 75 μm. Also, in the magnetic sensor 1 of Example 2, the width D1 of the sensing element 31 at both longitudinal ends was 90 μm, and the width D2 of the sensing element 31 at the longitudinal center was 70 μm. Furthermore, in the magnetic sensor 1 of Example 3, the width D1 of the sensing element 31 at both longitudinal ends was 95 μm, and the width D2 of the sensing element 31 at the longitudinal center was 65 μm. Still further, in the magnetic sensor 1 of Example 4, the width D1 of the sensing element 31 at both longitudinal ends was 100 μm, and the width D2 of the sensing element 31 at the longitudinal center was 60 μm.

[0044] As shown in FIGS. 5(a) to 5(b), in the magnetic sensor 1 (and the conventional magnetic sensor), the impedance Z of the sensing portion 30 increases, decreases, and changes as the absolute value of the magnetic field H increases in the positive or negative direction with the case where the magnetic field H is 0 (H = 0) as a boundary. Also, the amount of change in the impedance Z with respect to the change in the magnetic field H (that is, the slope of the graph) differs depending on the magnitude of the magnetic field H. Therefore, if a portion where the change amount ΔZ of the impedance Z is steep (that is, a portion where ΔZ / ΔH is large) with respect to the change amount ΔH of the applied magnetic field H is used, a weak change in the magnetic field H can be extracted as the change amount ΔZ of the impedance Z. In other words, in the magnetic sensor 1, by applying to the sensing element 31 a magnetic field H (hereinafter sometimes referred to as the bias magnetic field Hb) in the longitudinal direction of the sensing element 31 by the thin film magnet 20 such that ΔZ / ΔH becomes the largest, the change amount ΔH of the magnetic field H in the vicinity of the bias magnetic field Hb can be measured with high precision.

[0045] In the following description, the slope ΔZ / ΔH of the graph at the bias magnetic field Hb (that is, the maximum ΔZ / ΔH) is denoted as S maxIt may be expressed as. Also, the magnetic field H at which the impedance Z takes the maximum value may be expressed as the anisotropic magnetic field Hk. Further, the difference between the minimum value and the maximum value of the impedance Z in the graph (the maximum value of the change amount ΔZ of the impedance Z) is defined as the change amount ΔZ max It may be expressed as.

[0046] Table 1 shows the anisotropic magnetic field Hk, the change amount ΔZ max and S max (=ΔZ / ΔH) values obtained based on the relationship between the magnetic field H and the impedance Z of the magnetic sensor 1 of the present embodiment (Examples 1 to 4) and the conventional (comparative example) magnetic sensor shown in FIGS. 5(a) to 5(b).

[0047]

Table 1

[0048] Here, in the magnetic sensor 1 that measures the change amount ΔH of the magnetic field H based on the relationship between the magnetic field H and the impedance Z, the larger S max , the higher the sensitivity. Also, according to the relationship between the magnetic field H and the impedance Z shown in FIGS. 5(a) to 5(b), the smaller the anisotropic magnetic field Hk, or the larger the change amount ΔZ max , the steeper the change amount ΔZ of the impedance Z becomes, and S max tends to increase. That is, in the magnetic sensor 1, the smaller the anisotropic magnetic field Hk, or the larger the change amount ΔZ max , the better the sensitivity, which is preferable.

[0049] As shown in Table 1, in the magnetic sensors 1 of Examples 1 to 4, the anisotropic magnetic field Hk is smaller compared to the magnetic sensor of the comparative example. Also, in the magnetic sensors 1 of Examples 1, 2, and 4, the change amount ΔZ max is larger compared to the magnetic sensor of the comparative example. And in the magnetic sensors 1 of Examples 1 to 4, S max has increased compared to the magnetic sensor of the comparative example. As described above, in the magnetic sensor 1 of the present embodiment, the width D2 of the sensing element 31 at the central portion in the longitudinal direction is smaller than the width D1 of the sensing element 31 at both end portions in the longitudinal direction, so that the magnetic field tends to gather in the sensing element 31 and the magnetic field strength becomes uniform. As a result, in the magnetic sensor 1 of the present embodiment, compared with the case where the width of the sensing element 31 is constant from one end to the other end in the longitudinal direction, S max increases and the sensitivity can be improved.

[0050] (Manufacturing method of magnetic sensor 1) Next, an example of the manufacturing method of the magnetic sensor 1 will be described. Figs. 6(a) to (e) are diagrams for explaining an example of the manufacturing method of the magnetic sensor 1. Figs. 6(a) to (e) show the steps in the manufacturing method of the magnetic sensor 1. And the steps proceed in the order of Figs. 6(a) to (e). Figs. 6(a) to (e) are representative steps and may include other steps. Figs. 6(a) to (e) correspond to the cross-sectional view taken along the line II-II of Fig. 1 shown in Fig. 2.

[0051] As described above, the substrate 10 is a substrate made of a non-magnetic material, such as an oxide substrate such as glass or sapphire, a semiconductor substrate such as silicon, or a metal substrate such as a metal with aluminum, stainless steel, nickel plating, etc. applied thereto. On the substrate 10, linear grooves or linear irregularities with a curvature radius Ra of, for example, 0.1 nm to 100 nm may be provided using a polishing machine or the like. Note that the direction of the lines of the linear grooves or linear irregularities is preferably provided in the direction connecting the N pole and the S pole of the thin film magnet 20 formed by the hard magnetic layer 103. By doing so, crystal growth in the hard magnetic layer 103 is promoted in the groove direction. Therefore, the easy axis of magnetization of the thin film magnet 20 formed by the hard magnetic layer 103 tends to be more oriented in the groove direction (the direction connecting the N pole and the S pole of the thin film magnet 20). That is, magnetization of the thin film magnet 20 becomes easier.

[0052] Here, the substrate 10 is described as glass with a diameter of about 95 mm and a thickness of about 0.5 mm as an example. When the planar shape of the magnetic sensor 1 is several millimeters square, a plurality of magnetic sensors 1 are manufactured collectively on the substrate 10 and later divided (cut) into individual magnetic sensors 1. In FIGS. 6(a) to 6(e), attention is paid to one magnetic sensor 1 marked in the center, and a part of the magnetic sensors 1 adjacent to the left and right is shown together. Note that the boundary between adjacent magnetic sensors 1 is indicated by a dashed line.

[0053] As shown in FIG. 6(a), after cleaning the substrate 10, a adhesion layer 101, a control layer 102, a hard magnetic layer 103, and a dielectric layer 104 are sequentially formed (deposited) on one surface of the substrate 10 (hereinafter referred to as the surface), to form a laminate.

[0054] First, the adhesion layer 101, which is an alloy containing Cr or Ni, the control layer 102, which is an alloy containing Cr or the like, and the hard magnetic layer 103, which is a Co alloy constituting the thin film magnet 20, are sequentially and continuously formed (deposited). This film formation can be performed by a sputtering method or the like. By moving the substrate 10 so as to face a plurality of targets formed of each material in turn, the adhesion layer 101, the control layer 102, and the hard magnetic layer 103 are sequentially laminated on the substrate 10. As described above, in the formation of the control layer 102 and the hard magnetic layer 103, the substrate 10 may be heated to, for example, 100°C to 600°C in order to promote crystal growth.

[0055] In addition, in the film formation of the adhesion layer 101, the substrate 10 may or may not be heated. In order to remove moisture or the like adsorbed on the surface of the substrate 10, the substrate 10 may be heated before forming the adhesion layer 101.

[0056] Next, a dielectric layer 104, which is an oxide such as SiO2, Al2O3, TiO2, or a nitride such as Si3N4, AlN, etc., is formed (deposited). The film formation of the dielectric layer 104 can be performed by a plasma CVD method, a reactive sputtering method, or the like.

[0057] Then, as shown in Fig. 6(b), a pattern (resist pattern) 111 made of photoresist with openings at the portions where the sensing part 30 is formed and the portions where the yokes 40 (yokes 40a, 40b) are formed is formed by a known photolithography technique. In this embodiment, by controlling the shape of the resist pattern 111, the planar shapes of the above-described sensing element 31 and connection part 32 can be realized.

[0058] Then, as shown in Fig. 6(c), a high-conductivity layer 106, which is a conductor with higher conductivity compared to the lower soft magnetic layer 105a and the soft magnetic layer 105, which are Co alloys constituting the sensing part 30, and an upper soft magnetic layer 105b, which is a Co alloy constituting the sensing element 31, are sequentially formed (deposited). The soft magnetic layers 105 (lower soft magnetic layer 105a, upper soft magnetic layer 105b) and the high-conductivity layer 106 can be formed, for example, using a sputtering method.

[0059] As shown in Fig. 6(d), the resist pattern 111 is removed, and the soft magnetic layers 105 (lower soft magnetic layer 105a, upper soft magnetic layer 105b) and the high-conductivity layer 106 on the resist pattern 111 are removed (lifted off). Thereby, the sensing part 30 and the yokes 40 (yokes 40a, 40b) are formed by the soft magnetic layers 105 (lower soft magnetic layer 105a, upper soft magnetic layer 105b) and the high-conductivity layer 106. That is, the sensing part 30 and the yokes 40 are simultaneously formed by the film formation of the soft magnetic layers 105 and the high-conductivity layer 106.

[0060] After this, uniaxial magnetic anisotropy is imparted to the soft magnetic layer 105 in the short-side direction of the sensing element 31 (see Fig. 2) of the sensing part 30. The imparting of uniaxial magnetic anisotropy to the soft magnetic layer 105 can be performed, for example, by heat treatment (heat treatment in a rotating magnetic field) at 400°C in a rotating magnetic field of 3 kG (0.3 T) and subsequent heat treatment (heat treatment in a static magnetic field) at 400°C in a static magnetic field of 3 kG (0.3 T). At this time, the same uniaxial magnetic anisotropy is also imparted to the soft magnetic layer 105 constituting the yoke 40. However, the yoke 40 only needs to play a role as a magnetic circuit, and uniaxial magnetic anisotropy does not necessarily need to be imparted.

[0061] Next, the hard magnetic layer 103 constituting the thin film magnet 20 is magnetized. The magnetization of the hard magnetic layer 103 can be performed by applying a magnetic field larger than the coercive force of the hard magnetic layer 103 until the magnetization of the hard magnetic layer 103 reaches saturation in a static magnetic field or a pulsed magnetic field.

[0062] Thereafter, as shown in FIG. 6(e), the plurality of magnetic sensors 1 formed on the substrate 10 are divided (cut) into individual magnetic sensors 1. That is, as shown in the plan view of FIG. 1, the substrate 10, the adhesion layer 101, the control layer 102, the hard magnetic layer 103, the dielectric layer 104, the soft magnetic layer 105, and the high conductive layer 106 are cut so that the planar shape becomes a quadrangle. Then, the magnetic poles (N pole and S pole) of the thin film magnet 20 are exposed on the side surface of the divided (cut) hard magnetic layer 103. Thus, the magnetized hard magnetic layer 103 becomes the thin film magnet 20. This division (cut) can be performed by a dicing method, a laser cutting method, or the like.

[0063] Note that, before the step of dividing the plurality of magnetic sensors 1 in FIG. 6(e) into individual magnetic sensors 1, the adhesion layer 101, the control layer 102, the hard magnetic layer 103, the dielectric layer 104, the soft magnetic layer 105, and the high conductive layer 106 between the adjacent magnetic sensors 1 on the substrate 10 may be etched and removed so that the planar shape becomes a quadrangle (the planar shape of the magnetic sensor 1 shown in FIG. 1). Then, the exposed substrate 10 may be divided (cut). Further, after the step of forming the laminate in FIG. 6(a), the adhesion layer 101, the control layer 102, the hard magnetic layer 103, and the dielectric layer 104 may be processed so that the planar shape becomes a quadrangle (the planar shape of the magnetic sensor 1 shown in FIG. 1). Note that the manufacturing methods shown in FIGS. 6(a) to 6(e) have simplified processes compared to these manufacturing methods.

[0064] In this way, the magnetic sensor 1 is manufactured. Note that the imparting of uniaxial magnetic anisotropy to the soft magnetic layer 105 and / or the magnetization of the thin film magnet 20 may be performed for each magnetic sensor 1 or a plurality of magnetic sensors 1 after the step of dividing the magnetic sensors 1 in FIG. 6(e) into individual magnetic sensors 1.

[0065] In the case where the control layer 102 is not provided, after forming the hard magnetic layer 103, it is necessary to heat it to 800°C or higher to promote crystal growth, thereby imparting in-plane magnetic anisotropy. However, in the case of the magnetic sensor 1 to which the present embodiment is applied and which includes the control layer 102, since crystal growth is promoted by the control layer 102, crystal growth at a high temperature such as 800°C or higher is not required.

[0066] In addition, the uniaxial magnetic anisotropy can be imparted to the sensing element 31 by using the magnetron sputtering method during the deposition of the soft magnetic layer 105, which is a Co alloy constituting the sensing portion 30, instead of performing the heat treatment in the rotating magnetic field and the heat treatment in the static magnetic field as described above. In the magnetron sputtering method, a magnetic field is formed using a magnet, and electrons generated by discharge are confined to the surface of the target. As a result, the collision probability between electrons and gas is increased to promote gas ionization, and the film deposition rate is improved. Due to the magnetic field formed by the magnet used in this magnetron sputtering method, uniaxial magnetic anisotropy is imparted to the soft magnetic layer 105 simultaneously with the deposition of the soft magnetic layer 105. By doing so, the process of imparting uniaxial magnetic anisotropy performed by the heat treatment in the rotating magnetic field and the heat treatment in the static magnetic field can be omitted.

[0067] As described above, the embodiments of the present invention have been described, but various modifications may be made as long as they do not depart from the spirit of the present invention. In the magnetic sensor 1 described above, the long side portions 31a and 31b of the sensing element 31 have a curved shape such that the width of the sensing element 31 continuously changes from one end to the other end in the longitudinal direction. However, the present invention is not limited to this. For example, if the width D2 of the sensing element 31 at the central portion in the longitudinal direction is smaller than the width D1 of the sensing element 31 at both ends in the longitudinal direction, the width of the sensing element 31 may linearly change from one end to the center in the longitudinal direction, and the long side portions 31a and 31b of the sensing element 31 may be bent at the central portion.

[0068] In addition, in the magnetic sensor 1 described above, although the width D2 of the sensing element 31 at the central portion in the longitudinal direction is smaller than the width D1 of the sensing element 31 at both end portions in the longitudinal direction in all of the plurality of sensing elements 31, it is not limited to this. When the magnetic sensor 1 has a plurality of sensing elements 31, it is sufficient that the width D2 of the sensing element 31 at the central portion in the longitudinal direction is smaller than the width D1 of the sensing element 31 at both end portions in the longitudinal direction in at least one sensing element 31.

[0069] Furthermore, in the magnetic sensor 1 described above, the connecting portion 32 has a tapered portion 322 whose width in the short side direction becomes narrower as it approaches the end portion of the sensing element 31 along the longitudinal direction, but it is not limited to this. The connecting portion 32 may be composed of, for example, only a rectangular extending portion 321 that extends along the short side direction without having the tapered portion 322. However, from the viewpoint of increasing the magnetic flux density in the sensing element 31 and improving the sensitivity, it is preferable that the connecting portion 32 has the tapered portion 322.

[0070] Furthermore, in the magnetic sensor 1 described above, the sensing element 31, the connecting portion 32, and the terminal portion 33 of the sensing portion 30 are composed of a two-layer soft magnetic layer 105 (lower soft magnetic layer 105a, upper soft magnetic layer 105b) and a high conductive layer 106, but it is not limited to this. The sensing element 31, the connecting portion 32, or the terminal portion 33 of the sensing portion 30 may be composed of, for example, a single-layer soft magnetic layer.

Explanation of Reference Numerals

[0071] 1... Magnetic sensor, 20... Thin film magnet, 30... Sensing portion, 31... Sensing element, 31a, 31b... Long side portions, 32... Connecting portion, 33... Terminal portion, 40, 40a, 40b... Yoke, 101... Adhesive layer, 102... Control layer, 103... Hard magnetic layer, 104... Dielectric layer, 105... Soft magnetic layer, 105a... Lower soft magnetic layer, 105b... Upper soft magnetic layer, 106... High conductive layer, 321... Extending portion, 322... Tapered portion

Claims

Claim 1 A non-magnetic substrate, a sensing element provided on the substrate, made of a soft magnetic material, having a longitudinal direction and a lateral direction, having uniaxial magnetic anisotropy in a direction intersecting the longitudinal direction, having a smaller width at the central portion in the longitudinal direction than at both ends in the longitudinal direction, and using a change in impedance in a magnetic field range having an absolute value smaller than a magnetic field at which the impedance takes a maximum value in a curve representing the relationship between the magnetic field and the impedance to sense a change in the magnetic field by the magneto-impedance effect; and a magnetic sensor, characterized in that a ratio of a width of the sensing element at both ends in the longitudinal direction to a width of the sensing element at the central portion in the longitudinal direction is in a range of 100:68 to 100:

78. Claim 2 The magnetic sensor according to claim 1, characterized in that the sensing element has a width in the lateral direction that continuously decreases from both ends in the longitudinal direction to the central portion in the longitudinal direction. Claim 3 a plurality of the sensing elements arranged in the lateral direction with a gap therebetween; and a connecting portion that connects end portions in the longitudinal direction of the sensing elements adjacent to each other in the lateral direction and has a width in the lateral direction that becomes narrower as it approaches the sensing element along the longitudinal direction. The magnetic sensor according to claim 1 or 2.

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