Resonant magnetic sensor

Abstract

A resonant magnetic sensor (1) for detecting a magnetic field H is provided with: a vibrating element (10) having a vibrating part (21) having a first main surface (12a) and a second main surface (12b) facing the first main surface (12a), an upper electrode (14a) provided on the first main surface (12a) of the vibrating part (21), and a lower electrode (14b) provided on the second main surface (12b) of the vibrating part (21); an upper cover (30) provided on the upper electrode (14a) side of the resonator element (10); a lower cover (50) provided on the lower electrode (14b) side of the resonator element; a magnetic thin film (60) which is provided on the vibrating part (21) of the vibrating element (10); and film magnets (71, 72) that are provided inside an inner space (40) surrounded by the upper cover (30) and the lower cover (50) so as to be separated from the vibrating unit (21), and that apply a magnetic field to the magnetic film (60).

Description

Technical Field

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

[0002] Generally, a magnetic sensor that detects a change in an external magnetic field using the magnetostrictive effect is known. For example, Patent Document 1 discloses a magnetic sensor that vibrates a magnetic thin film (magnetic sensor element) formed on a vibrating body and checks a change in the external magnetic field by using a change in the Young's modulus of the thin film caused by the change in the external magnetic field as a change amount of the resonant frequency. In addition, Patent Document 2 discloses a magnetic sensor that applies a bias magnetic field by laminating a thin film magnet on a magnetic sensor element.

[0003] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2005-90971

[0004] Patent Document 2: International Publication No. 2021 / 245785

[0005] However, in the case of the structure as in Patent Document 1, the sensor sensitivity near zero magnetic field is low, and it is not suitable for sensing a minute magnetic field. In addition, in the case where the structure of Patent Document 2 is assumed to be applied to a resonant magnetic sensor having a vibrating portion, a thin film magnet is provided in the vibrating portion. Thereby, it is considered that the vibration of the vibrating portion is hindered, resulting in deterioration of its characteristics. Summary of the Invention

[0006] The present invention has been made in view of such circumstances, and an object of the present invention is to provide a resonant magnetic sensor with high sensitivity.

[0007] A resonant magnetic sensor according to one aspect of the present invention is a resonant magnetic sensor that detects a magnetic field, and includes: a vibrating element having a vibrating portion, an upper electrode provided on an upper main surface of the vibrating portion, and a lower electrode provided on a lower main surface of the vibrating portion, the vibrating portion having an upper main surface and a lower main surface opposed to the upper main surface; an upper cover provided on the upper electrode side of the vibrating element; a lower cover provided on the lower electrode side of the vibrating element; a magnetic thin film provided on the vibrating portion of the vibrating element; and a thin film magnet provided inside an internal space surrounded by the upper cover and the lower cover so as to be separated from the vibrating portion and applying a magnetic field to the magnetic thin film.

[0008] According to the present invention, a resonant magnetic sensor with high sensitivity can be provided. Brief Description of the Drawings

[0009] Figure 1 It is a perspective view schematically showing a resonant magnetic sensor according to a first embodiment.

[0010] Figure 2 It is a plan view schematically showing the structure of a quartz vibrating element of the resonant magnetic sensor according to the first embodiment.

[0011] Figure 3 is a cross-sectional view schematically showing the resonant magnetic sensor of the first embodiment.

[0012] Figure 4 is a graph showing the sensor sensitivity and the sensor output with respect to the magnetic field applied to the magnetic sensor in the case where no bias magnetic field is applied.

[0013] Figure 5 is a graph showing the sensor sensitivity and the sensor output with respect to the magnetic field applied to the magnetic sensor in the case where a bias magnetic field is applied.

[0014] Figure 6 is a cross-sectional view schematically showing the resonant magnetic sensor of the second embodiment.

[0015] Figure 7 is a cross-sectional view schematically showing the resonant magnetic sensor of the third embodiment.

[0016] Figure 8 is a cross-sectional view schematically showing the resonant magnetic sensor of the fourth embodiment. Detailed Embodiments

[0017] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The drawings of the present embodiment are illustrative, and the dimensions and shapes of each part are schematic dimensions and shapes, and the technical scope of the present invention should not be construed as being limited to this embodiment.

[0018] In each drawing, in order to clarify the mutual relationship of each drawing and facilitate understanding of the positional relationship of each component, there is a case where an orthogonal coordinate system composed of an X-axis, a Y'-axis, and a Z'-axis is conveniently added. The X-axis, the Y'-axis, and the Z'-axis correspond to each other in each drawing. The X-axis, the Y'-axis, and the Z'-axis respectively correspond to the crystallographic axes of the quartz plate described later. The X-axis corresponds to the electric axis (polar axis) of quartz, the Y-axis corresponds to the mechanical axis of quartz, and the Z-axis corresponds to the optical axis of quartz. The Y'-axis and the Z'-axis are axes obtained by rotating the Y-axis and the Z-axis by 35 degrees 15 minutes ± 1 minute 30 seconds around the X-axis from the Y-axis direction to the Z-axis direction, respectively.

[0019] In the following description, the direction parallel to the X-axis is referred to as the "X-axis direction", the direction parallel to the Y'-axis is referred to as the "Y'-axis direction", and the direction parallel to the Z'-axis is referred to as the "Z'-axis direction". In addition, the front-end direction of the arrows of the X-axis, Y'-axis, and Z'-axis is referred to as "positive" or "+(positive)", and the direction opposite to the arrow is referred to as "negative" or "-(negative)". Furthermore, for convenience, the +Y'-axis direction is set as the upward direction, and the -Y'-axis direction is set as the downward direction for description, but the up and down orientations of the quartz vibration element 10 are not limited. In addition, the plane determined by the X-axis and Z'-axis is set as the Z'X plane, and the same applies to the planes determined by other axes.

[0020] <First Embodiment>

[0021] Refer to Figure 1 、 Figure 2 and Figure 3 to describe the structure of the resonant magnetic sensor 1 according to the first embodiment of the present invention. Figure 1 is an exploded perspective view schematically showing the resonant magnetic sensor 1 of the present embodiment. Figure 2 is a top view schematically showing the structure of the quartz vibration element of the resonant magnetic sensor 1 according to the first embodiment. Figure 3 is a cross-sectional view schematically showing the structure of the resonant magnetic sensor 1 according to the first embodiment.

[0022] The resonant magnetic sensor 1 of the present embodiment includes a quartz vibration element 10, an upper cover 30, a lower cover 50, a magnetic thin film 60, and thin film magnets 71 and 72. In the following description, as the resonant magnetic sensor 1, a resonant magnetic sensor having a piezoelectric vibration element that outputs a resonant frequency for detecting a magnetic field is described as an example. In addition, as the piezoelectric vibration element, a quartz vibration element 10 having a quartz crystal blank is described as an example. The quartz wafer 11 is a type of piezoelectric body (piezoelectric wafer) that vibrates according to an applied voltage. In addition, the piezoelectric vibration element is not limited to the quartz vibration element 10, and other piezoelectric bodies such as ceramics can also be used. In addition, the piezoelectric vibration element can also be a MEMS vibration element manufactured using MEMS technology. In addition, the resonant magnetic sensor of the present embodiment is a magnetic sensor in which the resonant frequency of the piezoelectric vibration element changes according to an external magnetic field, and the external magnetic field is detected based on the change in the resonant frequency. In addition, the vibration mode in the resonant magnetic sensor of the present embodiment is not limited to the above piezoelectric type, and for example, an electrostatic type driven by an electrostatic force can also be used.

[0023] The quartz vibration element 10 (an example corresponding to the "vibration element") is an element that vibrates quartz through the piezoelectric effect and converts electrical energy and mechanical energy. The quartz vibration element 10 includes a quartz wafer 11 of the AT cut type. The quartz wafer 11 of the AT cut type is a quartz wafer cut out with the XZ' plane determined according to the X-axis and the Z'-axis as the main plane. The X-axis, Y-axis, and Z-axis are the crystal axes of synthetic quartz crystal, and the Y'-axis and Z'-axis are the axes obtained by rotating the Y-axis and Z-axis by 35 degrees 15 minutes ± 1 minute 30 seconds around the X-axis from the Y-axis to the Z-axis direction.

[0024] In addition, the rotation angles of the Y'-axis and Z'-axis in the quartz wafer 11 of the AT cut type can also be in the range of inclining -5 degrees or more and +15 degrees or less from 35 degrees 15 minutes. In addition, the cutting angle of the quartz wafer 11 can also be applied to different cuts other than the AT cut, such as the BT cut, GT cut, SC cut, etc.

[0025] The quartz vibration element using the AT cut quartz wafer has high frequency stability in a wide temperature range. In addition, the time-varying characteristics of the AT cut quartz vibration element are excellent, and on this basis, it can be manufactured at low cost. And, the AT cut quartz vibration element uses the thickness shear vibration mode as the main vibration.

[0026] The quartz vibration element 10 includes a set of exciting electrodes. An alternating electric field is applied between the set of exciting electrodes. Thereby, the vibrating portion of the quartz wafer 11 vibrates at a specified oscillation frequency through the thickness shear vibration mode, and the resonance characteristics accompanying the vibration are obtained.

[0027] In this way, since the main vibration of the quartz vibration element 10 is the thickness shear vibration mode, for example, by using the quartz wafer 11 of the AT cut, it is possible to easily realize a quartz vibration element that performs thickness shear vibration at a vibration frequency in the MHz band.

[0028] The quartz wafer 11 has a first main surface 12a and a second main surface 12b that are the XZ' plane and face each other. The quartz wafer 11 has a flat plate shape. Therefore, the first main surface 12a and the second main surface 12b of the quartz wafer 11 are flat surfaces respectively. In addition, the quartz wafer 11 is not limited to a flat plate shape. For example, the central portion can also be convex or concave.

[0029] The AT-cut type quartz wafer 11 has a long-side direction extending along the long side parallel to the X-axis direction, a short-side direction extending along the short side parallel to the Z'-axis direction, and a thickness direction extending along the thickness parallel to the Y'-axis direction. When looking down at the first main surface 12a of the quartz wafer 11 (hereinafter, simply referred to as "looking down"), the quartz wafer 11 has a rectangular shape. For example, the quartz wafer 11 can be thinned to a specified thickness by grinding after being joined to the lower cover 50 in a state of having a larger thickness.

[0030] In addition, the planar shape of the quartz wafer 11 is not limited to a rectangular shape. The planar shape of the quartz wafer 11 can also be a polygon, a circle, an ellipse, or a combination thereof.

[0031] The quartz vibration element 10 includes a vibration portion 21, a holding arm 22, and a holding portion 23. The vibration portion 21 has a quartz wafer 11 and a pair of excitation electrodes. The pair of excitation electrodes includes a first excitation electrode 14a (an example corresponding to the "upper electrode") and a second excitation electrode 14b (an example corresponding to the "lower electrode"). The first excitation electrode 14a is provided on the first main surface 12a of the vibration portion 21, and the second excitation electrode 14b is provided on the second main surface 12b of the vibration portion 21. The first excitation electrode 14a and the second excitation electrode 14b are arranged to face each other with the quartz wafer 11 interposed therebetween. When looking down at the first main surface 12a, the first excitation electrode 14a and the second excitation electrode 14b each have a rectangular shape and are arranged to substantially coincide with each other on the XZ' plane.

[0032] In addition, the first excitation electrode 14a and the second excitation electrode 14b are not limited to a rectangular shape and can also be a polygon, a circle, an ellipse, or a combination thereof.

[0033] The quartz vibration element 10 has lead electrodes and connection electrodes (not shown). Through these electrodes, the first excitation electrode 14a is electrically connected to the external electrode 54a, and the second excitation electrode 14b is electrically connected to the external electrode 54b. By applying an alternating electric field to the first excitation electrode 14a and the second excitation electrode 14b via these external electrodes 54a and 54b, the vibration portion 21 (specifically, the portion of the quartz wafer 11 where the first excitation electrode 14a and the second excitation electrode 14b are provided) vibrates in a specified vibration mode.

[0034] The materials of the first excitation electrode 14a, the second excitation electrode 14b, the lead electrodes, and the connection electrodes are, for example, aluminum (Al), molybdenum (Mo), or gold (Au). In addition, each of the above electrodes can also be a laminate composed of a titanium (Ti) layer provided on the side of the quartz wafer 11 and a gold (Au) layer provided on the surface side, for example.

[0035] The quartz vibration element 10 is housed in an internal space 40 formed between an upper lid 30 and a lower lid 50. The internal space 40 formed by the upper lid 30 and the lower lid 50 is hermetically sealed, for example. In addition, the internal space 40 can be hermetically sealed in a vacuum state or in a state filled with a gas such as an inert gas.

[0036] The vibrating portion 21 is a part of the quartz vibration element 10 and is located at the central portion of the internal space 40. In addition, as Figure 3 shown, the vibrating portion 21 has a first main surface 12a and a second main surface 12b opposed to the first main surface 12a. In addition, the vibrating portion 21 has a first exciting electrode 14a provided on the first main surface 12a and a second exciting electrode 14b provided on the second main surface 12b. The first exciting electrode 14a is provided on the surface of the quartz wafer 11 opposed to the upper lid 30, and the second exciting electrode 14b is provided on the surface opposed to the lower lid 50. And a magnetic thin film 60 is provided on the surface of the first exciting electrode 14a opposed to the upper lid 30. In addition, a magnetic thin film 60 may be provided on the surface of the quartz wafer 11 opposed to the upper lid 30, and the first exciting electrode 14a may be provided on the surface of the magnetic thin film 60 opposed to the upper lid 30.

[0037] The holding arm 22 is located in the internal space 40 in the same manner as the vibrating portion 21 and connects the vibrating portion 21 to the holding portion 23. Lead electrodes (not shown) are formed on the holding arm 22, and can lead the first exciting electrode 14a and the second exciting electrode 14b to connection electrodes provided on the holding portion 23.

[0038] The holding portion 23 is configured, for example, as a frame-shaped structure that surrounds the periphery of the vibrating portion 21 in a plan view. In addition, the holding portion 23 is not limited to a frame shape that surrounds the vibrating portion 21 over the entire circumference, and may be provided, for example, at at least a part of the periphery of the vibrating portion. The holding portion 23 is joined to the upper lid 30 and the lower lid 50 in the vertical direction. The holding portion 23 is connected to the holding arm 22. In addition, thin film magnets 71 and 72 are provided on the holding portion 23 to apply a magnetic field H to the magnetic thin film 60 on the vibrating portion 21. As a modification, the thin film magnet 71 may be provided not in the area of the holding portion 23 but on the surface of the holding arm 22 opposed to the upper lid 30.

[0039] A through hole 25 is provided in the vibrating portion 21. Specifically, the through hole 25 is provided in a region between the holding arm 22 and the magnetic thin film 60. The through hole 25 penetrates in the thickness direction of the vibrating portion 21 (in the Figure 3 example shown, it is the Y' axis direction). In addition, the through hole 25 is configured, for example, as a slit shape. In this case, the slit-shaped through hole 25 extends in a direction crossing the direction in which the magnetic thin film 60 and the holding arm 22 are arranged in a plan view of the quartz vibration element 10. In the present embodiment, as Figure 2In this way, the length L1 of the magnetic thin film 60 in the Z'-axis direction, the length L2 of the thin film magnet 71 in the Z'-axis direction, and the length L3 of the through hole in the Z'-axis direction are all of the same degree, but it is not limited thereto. For example, by making L3 longer than L1 or L2, the confinement of the vibration generated in the vibrating portion 21 can be improved. In the present embodiment, an example in which the through hole 25 is provided in the vibrating portion 21 has been described, but it is not necessary to form the through hole 25. In addition, instead of the through hole 25, a concave portion recessed in the Y'-axis direction may be applied.

[0040] The upper cover 30 has an upper surface portion 31 facing the quartz vibration element 10 and a side surface portion 32 extending from the outer periphery of the upper surface portion 31 in the negative Y'-axis direction. The concave portion 35 is formed by the upper surface portion 31 and the side surface portion 32. The upper cover 30 is joined to the upper surface side of the holding portion 23. The size of the upper cover 30 in plan view is the same as or substantially the same as the size of the quartz vibration element 10.

[0041] The internal space 40 is a space formed inside by the upper cover 30 and the lower cover 50, and is formed by the concave portion 35 of the upper cover 30 and the concave portion 55 of the lower cover 50. The vibrating portion 21 and the holding arm 22 are provided in the internal space 40 to constitute the vibration space of the quartz vibration element 10.

[0042] The lower cover 50 has a lower surface portion 51 facing the quartz vibration element 10 and a side surface portion 52 extending from the outer periphery of the lower surface portion 51 in the positive Y'-axis direction. The concave portion 55 is formed by the lower surface portion 51 and the side surface portion 52. The lower cover 50 is joined to the lower surface side of the holding portion 23. In addition, external electrodes 54a and 54b are provided on the side opposite to the surface of the lower cover 50 facing the vibrating portion 21. The external electrodes 54a and 54b are electrically connected to the first connection electrode and the second connection electrode.

[0043] The magnetic thin film 60 is provided on the first excitation electrode 14a of the vibrating portion 21. For example, the magnetic thin film 60 is formed in the same size as the first excitation electrode 14a in plan view. By applying an external magnetic field to the magnetic thin film 60, the Young's modulus of the magnetic thin film 60 changes. By providing the magnetic thin film 60 in the vibrating portion 21, the change in the Young's modulus can be detected as a change in the resonance frequency. In the first embodiment, the magnetic thin film 60 configured to be provided independently of the quartz wafer 11 functions as a magnetic body, but it is not limited thereto. For example, a multiferroic material having functions as a magnetic body and a piezoelectric body may also be used.

[0044] As Figure 2In this way, the thin film magnets 71 and 72 are arranged inside the internal space 40 surrounded by the upper cover 30 and the lower cover 50 so as to be separated from the vibrating portion 21, and are arranged to apply a magnetic field H to the magnetic thin film 60. The thin film magnet 71 is arranged in a region of the holding portion 23 that is connected to the holding arm 22 (an example corresponding to the "first region"), and the thin film magnet 72 is arranged in a region of the holding portion 23 opposite to this region (an example corresponding to the "second region"). These thin film magnets 71 and 72 are arranged on both sides of the magnetic thin film 60 with the magnetic thin film 60 interposed therebetween. Further, as Figure 3 shown, at least a part of the thin film magnets 71 and 72 and at least a part of the magnetic thin film 60 are in the same plane. The thin film magnet 71 has an S pole 71a and an N pole 71b. The S pole 71a is arranged to face the inside of the resonant magnetic sensor 1. The N pole 71b is arranged to face the outside of the resonant magnetic sensor 1. The thin film magnet 72 also has an S pole 72a and an N pole 72b. Different from the thin film magnet 71, the S pole 72a is arranged to face the outside of the resonant magnetic sensor 1, and the N pole 72b is arranged to face the inside of the resonant magnetic sensor 1. By arranging the S pole 71a of the thin film magnet 71 to face the N pole 72b of the thin film magnet 72 with the magnetic thin film 60 interposed therebetween in this way, a magnetic field H is generated from the N pole 72b to the S pole 71a, and the magnetic field H is applied to the magnetic thin film 60. In addition, the positional relationship between the S pole and the N pole of each magnetic thin film magnet can be switched. Further, in the illustrated example, the thin film magnet 71 is arranged in the holding portion 23, but it is not limited thereto. For example, it may be arranged in the holding arm 22. Further, as Figure 2 shown, the thin film magnets 71 and 72 may also be arranged in a portion of the holding portion 23 that extends along the Z'-axis and face each other in the X-axis direction. Or, different from the Figure 2 example shown, the thin film magnets 71 and 72 are arranged in a portion of the holding portion 23 that extends along the X-axis and face each other in the Z'-axis direction.

[0045] When viewed from above in Figure 2 , the length L1 of the magnetic thin film 60 in the Z'-axis direction and the length L2 of the thin film magnet 71 in the Z'-axis direction are of the same order, but it is not limited thereto. For example, by making the length L2 of the thin film magnet 71 in the Z'-axis direction larger than the length L1 of the magnetic thin film 60 in the Z'-axis direction, a uniform magnetic field can be applied to the entire magnetic thin film 60. In addition, the sizes of the thin film magnet 71 and the thin film magnet 72 may be the same.

[0046] Next, with reference to Figure 4 and Figure 5 , the effect of the bias magnetic field will be described. Figure 4is a diagram showing sensor sensitivity and sensor output with respect to a magnetic field applied to the magnetic sensor when no bias magnetic field is applied. Figure 5 FIG. 1 is a diagram showing sensor sensitivity and sensor output relative to a magnetic field applied to a magnetic sensor when a bias magnetic field is applied. Figure 4 as well as Figure 5 In the figure, the horizontal axis represents the magnetic field [mT] applied to the magnetic sensor, and the vertical axis represents the resonant frequency [Hz] of the quartz vibration element and the sensitivity [Hz / mT] of the sensor. Figure 4 In the case of zero magnetic field, the resonance frequency is the highest and the sensor sensitivity is approximately 0. In this case, it is difficult to detect a tiny magnetic field. Figure 5 By applying a bias magnetic field, the sensor sensitivity near the zero magnetic field can be increased. In addition, by detecting in a numerical range with good linearity between the magnetic field and the resonant frequency, it is possible to detect tiny changes in the magnetic field. Figure 4 as well as Figure 5 By applying a bias magnetic field in this manner, it is possible to measure a magnetic field in a numerical range where the sensitivity is low and precise measurement is difficult.

[0047] As described above, according to the resonant magnetic sensor 1 of this embodiment, a magnetic sensor capable of detecting a magnetic field near a zero magnetic field, which is originally less sensitive, with high sensitivity can be provided by applying a bias magnetic field to the magnetic thin film 60. In addition, by providing the thin film magnets 71 and 72 to be separated from the vibration part 21, the magnetic field H can be applied to the magnetic thin film 60 without hindering the vibration characteristics of the quartz vibration element 10.

[0048] Furthermore, by providing the thin film magnets 71 and 72 with the vibrating portion 21 interposed therebetween and with their respective S poles 71 a and N poles 72 b facing each other, the magnetic field H can be applied in parallel to the thin film magnets 71 and 72 . This allows a uniform magnetic field to be applied to the entire magnetic thin film 60 .

[0049] Furthermore, by providing the thin film magnets 71 and 72 in the internal space 40 , the distance between the magnetic thin film 60 and the thin film magnets 71 and 72 can be reduced, so that the design can be simplified and the manufacturing can be realized at low cost.

[0050] The structures of the resin sealing device and the resin sealing method of other modified examples and embodiments of the present invention are described below. In addition, in the following modified examples and embodiments, the same matters as those of the first embodiment are omitted, and only the differences are described. In particular, the same effects brought about by the same structure are not mentioned in sequence.

[0051] <Second embodiment>

[0052] Next, with reference to Figure 6 , the structure of the resonant magnetic sensor 2 of the second embodiment will be described. Figure 6 is a cross-sectional view schematically showing the structure of the resonant magnetic sensor of the second embodiment.

[0053] Different from the first embodiment, in the second embodiment, the upper cover 30 is made of a material with relatively high laser transmissivity. On the side of the upper cover 30 facing the vibrating portion 21, an getter layer 80 is provided at a position that does not overlap with the thin-film magnets 71 and 72 in a top view. The getter layer 80 adsorbs foreign substances generated when trimming the thin-film magnets 71 and 72. Accordingly, after the vibrating portion 21 is sealed by the upper cover 30 and the lower cover 50, the thin-film magnets 71 and 72 can be trimmed by laser via the upper cover 30 to adjust the magnetic field characteristics. And, by adsorbing the foreign substances of the thin-film magnets 71 and 72 generated during trimming by the getter layer 80, deterioration of characteristics caused by foreign substances can be suppressed.

[0054] In this embodiment, it is assumed that laser light enters from the side of the upper cover 30, but it is not limited thereto. For example, when the thin-film magnets 71 and 72 are provided on the side of the quartz vibrating element 10 facing the lower cover 50, laser light can also be irradiated from the side of the lower cover 50 made of a material with relatively high laser transmissivity for trimming. At this time, a getter layer can also be provided on the side of the lower cover 50 facing the vibrating portion 21.

[0055] <Third Embodiment>

[0056] Next, with reference to Figure 7 , the structure of the resonant magnetic sensor 3 of the third embodiment will be described. Figure 7 is a cross-sectional view schematically showing the structure of the resonant magnetic sensor of the third embodiment.

[0057] Different from the first embodiment, in the third embodiment, a magnetic thin film 61 is further provided on the lower surface of the second excitation electrode 14b of the vibrating portion 21. In addition, the magnetic thin film 61 has a magnetostrictive characteristic that is completely opposite to that of the magnetic thin film 60. Accordingly, a magnetostrictive effect of two layers composed of the magnetic thin films 60 and 61 can be obtained, and a magnetic sensor with higher sensitivity can be provided.

[0058] In this embodiment, the thin-film magnets 71 and 72 are provided on the side of the quartz vibrating element 10 facing the upper cover 30, but it is not limited thereto. For example, by providing thin-film magnets on the side of the quartz vibrating element 10 facing the lower cover 50 as well, a uniform magnetic field can be applied to the magnetic thin film 61 in the same manner as the magnetic thin film 60, and more accurate detection can be performed.

[0059] <Fourth Embodiment>

[0060] Next, with reference to Figure 8 , the structure of the resonant magnetic sensor 4 of the fourth embodiment will be described. Figure 8 FIG. is a cross-sectional view schematically showing the structure of the resonant magnetic sensor of the fourth embodiment.

[0061] Differing from the first embodiment, in the fourth embodiment, the arrangement of the thin film magnets is different. Specifically, in the first embodiment, the thin film magnets 71 and 72 are arranged in the holding portion 23 with the magnetic thin film 60 interposed therebetween. In contrast, in the present embodiment, the thin film magnet 73 is provided on the side of the upper cover 30 facing the vibrating portion 21. In this case, the magnetic field H also passes through the magnetic thin film 60 in the positive X-axis direction as Figure 8 , so that a bias magnetic field can be applied. Further, although the thin film magnet 73 is provided on the upper cover 30 in the present embodiment, it is not limited thereto. For example, the thin film magnet may be provided on the side of the lower cover 50 facing the vibrating portion 21.

[0062] Hereinafter, a part or all of the embodiments of the present invention will be appended. In addition, the present invention is not limited to the following appendices.

[0063] <1>

[0064] As described above, according to one aspect of the present invention, there is provided a resonant magnetic sensor that is a resonant magnetic sensor for detecting a magnetic field, including: a vibrating element having a vibrating portion, an upper electrode provided on an upper main surface of the vibrating portion, and a lower electrode provided on a lower main surface of the vibrating portion, the vibrating portion having an upper main surface and a lower main surface opposed to the upper main surface; an upper cover provided on the upper electrode side of the vibrating element; a lower cover provided on the lower electrode side of the vibrating element; a magnetic thin film provided on the vibrating portion of the vibrating element; and a thin film magnet provided inside the internal space surrounded by the upper cover and the lower cover so as to be separated from the vibrating portion and applying a magnetic field to the magnetic thin film.

[0065] According to the above aspect, a highly sensitive magnetic sensor can be provided by applying a bias magnetic field to the magnetic thin film. Further, by providing the thin film magnet so as to be separated from the vibrating portion, a magnetic field can be applied to the magnetic thin film without hindering the vibration characteristics of the vibrating element. And by providing the magnetic thin film and the thin film magnet in the vibration space sealed by the upper cover and the lower cover, compared with the structure in which the thin film magnet is provided outside, the distance between the magnetic thin film and the thin film magnet can be reduced, the design can be simplified, and it can be realized at low cost.

[0066] <2>There is provided the resonant magnetic sensor described in <1>,

[0067] As one aspect, the magnetic thin film and the thin film magnet are located on the same plane.

[0068] According to the above method, a uniform magnetic field can be applied to the entire magnetic thin film.

[0069] <3> provides the resonant magnetic sensor described in <1> or <2>.

[0070] As one mode, the vibrating element has a holding part provided at least partially around the vibrating part in a plan view, and a holding arm connecting the holding part and the vibrating part. The upper cover and the lower cover are respectively connected to the holding part, and the thin film magnet is provided on the holding part or the holding arm.

[0071] <4> provides the resonant magnetic sensor described in <3>.

[0072] As one mode, the holding arm is provided between the vibrating part and the thin film magnet, and a through hole or a recess penetrating in the thickness direction of the vibrating part is provided in the region between the magnetic thin film and the holding arm in the vibrating part.

[0073] According to the above method, the confinement of the vibration generated in the vibrating part can be improved by the through hole or the recess.

[0074] <5> provides the resonant magnetic sensor described in <4>.

[0075] As one mode, the through hole or the recess is formed in a slit shape extending in a direction intersecting with the direction in which the magnetic thin film and the holding arm are arranged in a plan view.

[0076] According to the above method, the confinement of the vibration can be further improved.

[0077] <6> provides the resonant magnetic sensor described in any one of <3> to <5>.

[0078] As one mode, the holding part is provided to surround the vibrating part in a plan view, and the thin film magnet has a first thin film magnet provided in a first region of the holding part and a second thin film magnet provided in a second region of the holding part opposite to the first region with the magnetic thin film interposed therebetween.

[0079] According to the above method, since the first thin film magnet and the second thin film magnet are opposed to each other, a uniform magnetic field can be applied to the vibrating part and the entire magnetic thin film between the first thin film magnet and the second thin film magnet.

[0080] <7> provides the resonant magnetic sensor described in any one of <1> to <6>.

[0081] As one mode, the thin film magnet is provided on at least one of the upper cover and the lower cover.

[0082] <8> provides the resonant magnetic sensor described in any one of <1> to <7>.

[0083] As one mode, the magnetic thin film is provided on at least one of the surface of the upper electrode in the vibrating portion facing the upper cover and the surface of the lower electrode in the vibrating portion facing the lower cover.

[0084] According to the above mode, by providing two layers of magnetic thin films on the upper electrode side and the lower electrode side, a magnetic sensor with higher sensitivity can be provided.

[0085] <9> Provide the resonant magnetic sensor described in any one of <1> to <8>.

[0086] As one mode, at least one of the upper cover and the lower cover is made of a material that can transmit the laser for trimming the thin film magnet.

[0087] According to the above mode, after the vibrating element is sealed by the upper cover and the lower cover, the thin film magnet can be trimmed to adjust the magnetic field characteristics applied by the thin film magnet.

[0088] <10> Provide the resonant magnetic sensor described in any one of <1> to <9>.

[0089] As one mode, a getter layer for adsorbing foreign substances generated during trimming of the thin film magnet is provided in at least one of the regions of the upper cover and the lower cover facing the vibrating portion, and the getter layer is provided at a position that does not overlap with the thin film magnet in a top view.

[0090] According to the above mode, by adsorbing foreign substances generated during trimming of the thin film magnet by the getter layer, it is possible to prevent foreign substances from adhering to the vibrating portion and deteriorating the vibration characteristics.

[0091] In addition, the embodiments described above are embodiments for facilitating the understanding of the present invention, and are not embodiments for limiting the interpretation of the present invention. The present invention can be changed / improved without departing from its gist, and the present invention also includes its equivalents. That is, as long as the features of the present invention are provided, embodiments in which those skilled in the art have appropriately made design changes to each embodiment are also included in the scope of the present invention. For example, each element, its configuration, material, conditions, shape, size, etc. possessed by each embodiment are not limited to the illustrated content and can be appropriately changed. In addition, as long as it is technically feasible, the elements possessed by each embodiment can be combined, and embodiments obtained by combining these elements are also included in the scope of the present invention as long as they include the features of the present invention.

[0092] Description of reference numerals

[0093] 1, 2, 3, 4... Resonant magnetic sensors, 10... Quartz vibration element, 11... Quartz wafer, 12a... First main surface, 12b... Second main surface, 14a... First excitation electrode, 14b... Second excitation electrode, 21... Vibration part, 22... Holding arm, 23... Holding part, 25... Through hole, 30... Upper cover, 31... Upper surface part, 32... Side surface part, 35... Concave part, 40... Internal space, 50... Lower cover, 51... Lower surface part, 52... Side surface part, 54a, 54b... External electrodes, 55... Concave part, 60, 61... Magnetic thin films, 71, 72, 73... Thin film magnets, 71a, 72a, 73a... S poles, 71b, 72b, 73b... N poles, 80... Getter layer, H... Magnetic field, L1... Length of the magnetic thin film along the Z' axis direction, L2... Length of the thin film magnet along the Z' axis direction, L3... Length of the through hole along the Z' axis direction.

Claims

1. A resonant magnetic sensor, which is a resonant magnetic sensor for detecting a magnetic field, wherein, Comprising: A vibration element having a vibrating portion, an upper electrode provided on a first main surface of the vibrating portion, and a lower electrode provided on a second main surface of the vibrating portion, the vibrating portion having the first main surface and the second main surface opposed to the first main surface; An upper cover provided on the upper electrode side of the vibration element; A lower cover provided on the lower electrode side of the vibration element; A magnetic thin film provided on the vibrating portion of the vibration element; and A thin film magnet disposed inside the internal space surrounded by the upper cover and the lower cover so as to be separated from the vibrating portion and applying a magnetic field to the magnetic thin film.

2. The resonant magnetic sensor according to claim 1, wherein The magnetic thin film and the thin film magnet are located on the same plane.

3. The resonant magnetic sensor according to claim 1 or 2, wherein The vibration element has a holding portion provided at least partially around the vibrating portion in a plan view, and a holding arm connecting the holding portion and the vibrating portion, The upper cover and the lower cover are respectively connected to the holding portion, The thin film magnet is provided on the holding portion or the holding arm.

4. The resonant magnetic sensor according to claim 3, wherein The holding arm is provided between the vibrating portion and the thin film magnet, A through hole or a recess penetrating in the thickness direction of the vibrating portion is provided in a region between the magnetic thin film and the holding arm in the vibrating portion.

5. The resonant magnetic sensor according to claim 4, wherein The through hole or the recess is formed in a slit shape extending in a direction intersecting with the direction in which the magnetic thin film and the holding arm are arranged in a plan view.

6. The resonant magnetic sensor according to any one of claims 3 to 5, wherein The holding portion is provided so as to surround the periphery of the vibrating portion in a plan view, The thin film magnet has a first thin film magnet provided in a first region of the holding portion, and a second thin film magnet provided in a second region of the holding portion opposite to the first region with the magnetic thin film interposed therebetween.

7. The resonant magnetic sensor according to any one of claims 1 to 6, wherein The thin film magnet is provided on at least one of the upper cover and the lower cover.

8. The resonant magnetic sensor according to any one of claims 1 to 7, wherein The magnetic thin film is provided on at least one of a surface of the vibrating portion where the upper electrode faces the upper cover and a surface of the vibrating portion where the lower electrode faces the lower cover.

9. The resonant magnetic sensor according to any one of claims 1 to 8, wherein At least one of the upper cover and the lower cover is made of a material capable of transmitting the laser for trimming the thin film magnet.

10. The resonant magnetic sensor according to any one of claims 1 to 9, wherein An getter layer is provided in a region of at least one of the upper cover and the lower cover opposed to the vibrating portion, and the getter layer adsorbs foreign matters generated when trimming the thin film magnet, The getter layer is provided at a position that does not overlap with the thin film magnet in a plan view.

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