Magnetic field sensor, preparation method and electronic device

Abstract

The embodiment of the invention provides a magnetic field sensor, a preparation method and an electronic device. The magnetic field sensor comprises a substrate, a piezoelectric layer and a top electrode layer. The substrate is provided with a cavity which is opened on two opposite surfaces of the substrate; the first surface of the piezoelectric layer is arranged on the substrate and covers the cavity to form a suspended piezoelectric area, and the first surface of the piezoelectric layer at least crosses an opening formed by the cavity to be in contact with the substrate; the top electrode layer is arranged on the second surface of the piezoelectric layer and at least partially covers the suspended piezoelectric area, the top electrode layer is configured to be fed with an electrical signal in operation and generate an electric field in the piezoelectric layer to excite acoustic waves, and the top electrode layer has magnetism and generates magnetostriction under the action of an external magnetic field to change a response value of the electrical signal, the second surface of the piezoelectric layer is opposite to the first surface. According to the magnetic field sensor, the detection sensitivity can be improved while the device stability is improved.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to a magnetic field sensor, a preparation method thereof, and an electronic device. Background Art

[0002] A magnetic field sensor is a sensor used to detect the presence, direction, and intensity of a magnetic field, and is widely used in various fields, including navigation, positioning, scientific research, industrial automation, medical devices, etc.

[0003] However, existing magnetic field sensors, especially in resonant magnetic field sensors based on bulk acoustic waves, have problems such as complex preparation processes, thin film stress, and poor device stability. Summary of the Invention

[0004] At least one embodiment of the present disclosure provides a magnetic field sensor, including a substrate, a piezoelectric layer, and a top electrode layer. Wherein, the substrate has a cavity that opens on two opposite surfaces of the substrate; a first surface of the piezoelectric layer is disposed on the substrate and covers the cavity, forming a suspended piezoelectric region, wherein the first surface of the piezoelectric layer at least crosses the opening formed by the cavity and contacts the substrate; the top electrode layer is disposed on a second surface of the piezoelectric layer and at least partially covers the suspended piezoelectric region, and is configured to be fed with an electrical signal during operation, generate an electric field in the piezoelectric layer to excite acoustic waves, the top electrode layer has magnetism and undergoes magnetostriction under the action of an external magnetic field to change the response value of the electrical signal, wherein the second surface of the piezoelectric layer is opposite to the first surface.

[0005] For example, in a magnetic field sensor provided by at least one embodiment of the present disclosure, the top electrode layer includes a first top electrode and a second top electrode, the first top electrode and the second top electrode are separately disposed on the second surface of the piezoelectric layer, and respectively at least partially cover the suspended piezoelectric region.

[0006] For example, in a magnetic field sensor provided by at least one embodiment of the present disclosure, a part of the first top electrode extends beyond the suspended piezoelectric region to form a first terminal, and a part of the second top electrode extends beyond the suspended piezoelectric region to form a second terminal; wherein, the first terminal and the second terminal are configured to receive the electrical signal and output the response value of the electrical signal.

[0007] For example, in a magnetic field sensor provided by at least one embodiment of the present disclosure, the top electrode layer includes a magnetic material part and a conductive part; or the top electrode layer is a conductive magnetic material layer.

[0008] For example, a magnetic field sensor provided by at least one embodiment of the present disclosure further includes: a bottom electrode layer disposed on a first surface of the piezoelectric layer and located in the cavity, overlapping with the suspended piezoelectric region.

[0009] For example, in a magnetic field sensor provided by at least one embodiment of the present disclosure, the bottom electrode layer is a non-magnetic conductive layer or a conductive layer with magnetism, and in the case where the bottom electrode layer is a conductive layer with magnetism, the bottom electrode layer is a conductive magnetic material layer or includes a magnetic material part and a conductive part.

[0010] For example, in a magnetic field sensor provided by at least one embodiment of the present disclosure, the magnetic field sensor includes a magnetic layer, and a ratio of a thickness of the magnetic layer to a thickness of the piezoelectric layer is equal to a ratio of a sound velocity of the acoustic wave in the magnetic layer to a sound velocity of the acoustic wave in the piezoelectric layer, and the magnetic layer includes a magnetic material part and / or a conductive magnetic material layer in the magnetic field sensor.

[0011] For example, in a magnetic field sensor provided by at least one embodiment of the present disclosure, the magnetic field sensor includes a magnetic layer, and the thickness of the magnetic layer is the same as the thickness of the piezoelectric layer, and the magnetic layer includes a magnetic material part and / or a conductive magnetic material layer in the magnetic field sensor.

[0012] At least one embodiment of the present disclosure further provides an electronic device, and the electronic device includes the magnetic field sensor provided by any embodiment of the present disclosure.

[0013] For example, in an electronic device provided by at least one embodiment of the present disclosure, the electronic device further includes: a readout circuit configured to receive and analyze a response value of an electrical signal to obtain a magnetic field strength measurement value.

[0014] For example, in an electronic device provided by at least one embodiment of the present disclosure, the electronic device further includes: a signal application circuit configured to apply an electrical signal to the magnetic field sensor.

[0015] At least one embodiment of the present disclosure further provides a method for manufacturing a magnetic field sensor, including: providing a substrate; forming a piezoelectric layer on one side of the substrate, wherein the substrate is disposed on a first surface of the piezoelectric layer; forming a top electrode layer on a second surface of the piezoelectric layer, wherein the top electrode layer is configured to be fed an electrical signal during operation to generate an electric field in the piezoelectric layer to excite acoustic waves, the top electrode layer has magnetism and undergoes magnetostriction under the action of an external magnetic field to change a response value of the electrical signal, and the second surface of the piezoelectric layer is opposite to the first surface; removing a part of the substrate to form a cavity having openings on two opposite surfaces of the substrate, the first surface of the piezoelectric layer is disposed on the substrate and covers the cavity to form a suspended piezoelectric region; wherein the first surface of the piezoelectric layer at least crosses the opening formed by the cavity and contacts the substrate.

[0016] For example, in a manufacturing method provided by at least one embodiment of the present disclosure, the forming the piezoelectric layer on one side of the substrate includes: directly growing the piezoelectric layer on the substrate, or transferring and bonding the piezoelectric layer to the substrate.

[0017] For example, a manufacturing method provided by at least one embodiment of the present disclosure further includes: forming a bottom electrode layer on the first surface of the piezoelectric layer, wherein the bottom electrode layer overlaps with the suspended piezoelectric region and is located in the cavity. Description of the Drawings

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings in the following description only relate to some embodiments of the present disclosure and do not limit the present disclosure.

[0019] Figure 1 A schematic structural diagram of a magnetic field sensor provided by at least one embodiment of the present disclosure;

[0020] Figure 2A Another schematic structural diagram of a magnetic field sensor provided by at least one embodiment of the present disclosure;

[0021] Figure 2B Corresponding to Figure 2A The exemplary structural diagram of the magnetic field sensor shown;

[0022] Figure 3A An exemplary partial structural schematic top view of a magnetic field sensor provided by at least one embodiment of the present disclosure;

[0023] Figure 3B Corresponding to Figure 3A The exemplary structural diagram of the magnetic field sensor shown;

[0024] Figure 4 Schematic block diagram of an electronic device provided by at least one embodiment of the present disclosure;

[0025] Figure 5 Schematic flowchart of a method for manufacturing a magnetic field sensor provided by at least one embodiment of the present disclosure;

[0026] Figure 6 Schematic flowchart of a manufacturing process of a magnetic field sensor provided by at least one embodiment of the present disclosure;

[0027] Figure 7 Schematic diagram of a manufacturing process of a magnetic field sensor provided by at least one embodiment of the present disclosure; and

[0028] Figure 8 Schematic curve graph showing the change of the admittance of a magnetic field sensor with the elastic modulus of a magnetic material provided by at least one embodiment of the present disclosure. Detailed implementation manners

[0029] In order to make the objectives, technical solutions and advantages of the embodiments of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present disclosure. Obviously, the described embodiments are some but not all of the embodiments of the present disclosure. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of the present disclosure without creative efforts shall fall within the scope of protection of the present disclosure.

[0030] Unless otherwise defined, the technical terms or scientific terms used in the present disclosure shall have the ordinary meanings understood by those of ordinary skill in the art to which the present disclosure belongs. The "first", "second" and similar terms used in the present disclosure do not denote any order, quantity or importance, but are only used to distinguish different components. The terms such as "including" or "comprising" mean that the elements or items appearing before this word cover the elements or items listed after this word and their equivalents, without excluding other elements or items. The terms such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms such as "upper", "lower", "left" and "right" are only used to represent relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0031] The following describes the present disclosure through several specific embodiments. To keep the following description of the embodiments of the present disclosure clear and concise, detailed descriptions of known functions and known components may be omitted. When any component of the embodiments of the present disclosure appears in more than one drawing, the component is denoted by the same or similar reference numerals in each drawing.

[0032] The core working region of an acoustic wave resonant magnetic field sensor is generally composed of a composite of a piezoelectric material and a magnetostrictive material, and electrodes are used to lead out signals. This magnetic field sensor is divided into two categories: active magnetic field sensors and passive magnetic field sensors.

[0033] The working principle of an active acoustic wave resonant magnetic field sensor is as follows: By applying an electrical signal, the inverse piezoelectric effect of the piezoelectric material is used to generate acoustic waves and excite acoustic resonance. Under the action of the external magnetic field to be measured, the acoustic performance of the magnetostrictive material changes, thereby affecting parameters such as the resonant frequency of the device. The magnitude of the magnetic field is sensed by detecting the change in the resonant frequency or related electrical parameters. Currently, active acoustic wave resonant magnetic field sensors can be divided into magnetic field sensors based on surface acoustic wave (SAW) resonant structures and magnetic field sensors based on bulk acoustic wave (BAW) resonant structures according to the type of acoustic wave.

[0034] The working principle of a passive acoustic resonant magnetic field sensor is as follows: Under the action of an external alternating magnetic field, the magnetic material generates periodic deformation due to the magnetostrictive effect, causing acoustic resonance of the piezoelectric-ferromagnetic composite structure, and then generating an electrical signal output through the piezoelectric effect of the piezoelectric material. The magnitude of the external magnetic field to be measured is sensed by detecting the magnitude of the output electrical signal. Passive acoustic resonant magnetic field sensors are mainly based on the 31 bulk acoustic wave tensile resonance mode, and the main device configurations include MEMS cantilever beams or nanoplate resonator structures (Nanoplate resonator, NPR).

[0035] A surface acoustic wave resonator excites surface acoustic waves by fabricating interdigital electrodes on a piezoelectric substrate. A resonant magnetic field sensor based on surface acoustic waves requires further depositing a magnetic material layer above the piezoelectric material and the interdigital electrodes to achieve the sensing ability for the magnetic field.

[0036] However, the structure of the above-mentioned surface acoustic wave-based resonant magnetic field sensor usually causes the following problems. The frequency of the surface acoustic wave depends on the surface wave velocity of the overall composite structure. However, with the change of the elastic modulus of the magnetic material, the change of the surface wave velocity is generally small. This is because the surface acoustic wave is mainly concentrated in the range of about one wavelength depth on the surface of the composite material, while the ferromagnetic material is usually very thin in comparison, so the interaction between the acoustic wave and the magnetic material is small. To make the surface wave velocity dominated by the ferromagnetic material to obtain the best sensitivity, the thickness of the ferromagnetic material generally needs to reach at least the micron level, which is not feasible in practice.

[0037] Since the planar interdigital electrode structure is above the piezoelectric material, an insulating layer needs to be introduced between the magnetic thin film and the piezoelectric substrate during the preparation of the metal magnetic material to prevent the magnetic metal thin film from short-circuiting the interdigital electrodes, resulting in the device being unable to work. However, due to the presence of the periodic interdigital electrodes, a periodic step will appear on the magnetic thin film, and the flatness is poor, which will have a great impact on the soft magnetic properties of the thin film. If a relatively flat magnetic thin film is desired, an additional thin film mechanical chemical polishing process needs to be introduced, which will greatly increase the process complexity of the device and reduce the device consistency. On the other hand, the introduction of the insulating layer will further weaken the interaction between the acoustic wave and the magnetic material, reducing the detection sensitivity of the sensor device.

[0038] Bulk acoustic wave resonators can be divided into film bulk acoustic resonators (FBAR) and solid mounted resonators (SMR). By applying an excitation electric field to the electrodes on the upper and lower surfaces of the piezoelectric thin film, bulk acoustic waves are excited and resonate in the thickness direction of the thin film. The resonant frequency is determined by the sound velocity and the thin film thickness. The resonant magnetic field sensor based on bulk acoustic waves (usually a film bulk acoustic resonator) can directly prepare a magnetic material layer on the basis of the electrode, or directly replace the electrode with a conductive magnetic material layer. Therefore, there is no short-circuit problem in the above-mentioned magnetic material layer or conductive magnetic material layer, and there is no need to introduce additional processes to make the thin film flat, and the device consistency is good. Moreover, since there is no substrate in the working area of the magnetic field sensor, the interaction between the acoustic wave and the magnetic material is stronger.

[0039] However, bulk acoustic wave resonators usually have problems such as complex fabrication processes, thin film stress, and poor device stability. In terms of structure, a thin film bulk acoustic wave resonator forms a suspended electrode-piezoelectric layer-electrode three-layer structure by removing the substrate or sacrificial layer under the piezoelectric material, and the fabrication process is complex and difficult; a thin film bulk acoustic wave resonator usually uses an air cavity under the device to achieve acoustic isolation, which has a high mechanical quality factor and a small device size, but the suspended structure makes the device have poor device stability, and the presence of stress after substrate release often causes the thin film device to bend, thereby introducing an undesired magnetocrystalline anisotropy in the magnetic thin film.

[0040] In terms of the fabrication process, the bulk acoustic wave resonators fabricated by conventional processes often operate in the thickness extension mode due to material limitations. However, the magnetic domains of general magnetic materials are arranged in the plane, and the acoustic vibration along the thickness direction (out-of-plane) is orthogonal to the magnetization direction (in-plane) of the thin film material, which often leads to weak interaction between the acoustic wave and the magnetic material, resulting in low sensitivity of the device to the magnetic field.

[0041] At least one embodiment of the present disclosure provides a magnetic field sensor, a fabrication method thereof, and an electronic device. The magnetic field sensor includes a substrate, a piezoelectric layer, and a top electrode layer. The substrate has a cavity that is open on two opposite surfaces of the substrate; a first surface of the piezoelectric layer is disposed on the substrate and covers the cavity, forming a suspended piezoelectric region, wherein the first surface of the piezoelectric layer at least crosses the opening formed by the cavity and contacts the substrate; the top electrode layer is disposed on a second surface of the piezoelectric layer and at least partially covers the suspended piezoelectric region, and is configured to be fed an electrical signal during operation to generate an electric field in the piezoelectric layer to excite an acoustic wave. The top electrode layer has magnetism and undergoes magnetostriction under the action of an external magnetic field to change the response value of the electrical signal, wherein the second surface of the piezoelectric layer is opposite to the first surface.

[0042] The magnetic field sensor provided by at least one embodiment of the present disclosure adopts a multi-sided fixed (such as fully fixed) suspended magnetoelectric heterojunction thin film structure, which can greatly improve the device stability; and it simplifies the electrode configuration, thereby greatly reducing the fabrication process complexity. At the same time, the bulk acoustic wave configuration enables this structure to have enhanced magnetic field sensitivity.

[0043] The manufacturing method of the above embodiments includes: providing a substrate; forming a piezoelectric layer on one side of the substrate, wherein the substrate is disposed on the first surface of the piezoelectric layer; forming a top electrode layer on the second surface of the piezoelectric layer, wherein the top electrode layer is configured to be fed with an electrical signal during operation, generate an electric field in the piezoelectric layer to excite acoustic waves, the top electrode layer has magnetism and magnetostriction occurs under the action of an external magnetic field to change the response value of the electrical signal, and the second surface of the piezoelectric layer is opposite to the first surface; removing a part of the substrate to form a cavity that is open on two opposite surfaces of the substrate, and the first surface of the piezoelectric layer is disposed on the substrate and covers the cavity to form a suspended piezoelectric region; wherein, the first surface of the piezoelectric layer contacts the substrate at least across the opening formed by the cavity.

[0044] The manufacturing method provided by at least one embodiment of the present disclosure, compared with the traditional bulk acoustic wave resonator, does not require simultaneously leading out the top electrode and the bottom electrode for external electrical connection. Therefore, it is not necessary to use a patterning etching process for the piezoelectric layer to lead out the bottom electrode, and it is not necessary to pattern the bottom electrode either. Therefore, the required manufacturing process of the manufacturing method provided by at least one embodiment of the present disclosure is simple.

[0045] Embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings, but the present disclosure is not limited to these specific embodiments.

[0046] Figure 1 is a schematic structural diagram of a magnetic field sensor provided by at least one embodiment of the present disclosure.

[0047] As Figure 1 shown, the magnetic field sensor 100 includes a substrate 110, a piezoelectric layer 120, and a top electrode layer 130.

[0048] As Figure 1 shown, the substrate 110 has a cavity that is open on two opposite surfaces of the substrate 110. That is to say, the cavity inside the substrate 110 penetrates from one surface of the substrate (such as Figure 1 the front surface in Figure 1 ) to the other surface (such as the back surface in

[0049] ). Figure 1 Figure 1 As Figure 1 shown, the first surface (such as Figure 1 the lower surface in Figure 1 ) of the piezoelectric layer 120 is opposite to the second surface (such as the upper surface in

[0050] ), the first surface of the piezoelectric layer 120 contacts the substrate 110 ( Figure 1 the upper surface in Figure 1 ), and the second surface of the piezoelectric layer 120 contacts the top electrode layer 130 ( Figure 1 the lower surface in ).

[0050] As Figure 1As shown, the first surface of the piezoelectric layer is disposed on the substrate 110 and covers the cavity, forming a suspended piezoelectric region. The first surface of the piezoelectric layer 120 contacts the substrate 110 through an opening formed by at least spanning the cavity (i.e., from one side of the cavity to the other opposite side). For example, the suspended piezoelectric region is a three-dimensional region, including the region where the first surface of the piezoelectric layer 120 does not contact the substrate 110 (i.e., Figure 1 the shaded region in), the corresponding region in the second surface of the piezoelectric layer 120 for this region, and the piezoelectric layer body therebetween.

[0051] As Figure 1 shown, the top electrode layer 130 is disposed on the second surface of the piezoelectric layer 120 and at least partially covers the suspended piezoelectric region. The top electrode layer 130 is configured to be fed an electrical signal during operation, for example, through a wire (not shown in the figure), to generate an electric field in the piezoelectric layer 120 to excite acoustic waves. The top electrode layer 130 has magnetism and undergoes magnetostriction under the action of an external magnetic field to change the response value of the electrical signal.

[0052] For example, as Figure 1 shown, the layers of materials overlapping with the suspended piezoelectric region can be referred to as suspended magnetoelectric heterojunction thin films. For example, as Figure 1 shown, the top electrode layer partially covering the suspended piezoelectric region and the piezoelectric layer body in the suspended piezoelectric region can be referred to as suspended magnetoelectric heterojunction thin films. The above magnetic field sensor generates an electric field by applying an electrical signal, utilizes the inverse piezoelectric effect of the piezoelectric layer 120 to generate an electric field, excites acoustic waves and generates acoustic resonance. Under the action of an external magnetic field to be measured, the magnetic material in the top electrode layer 130 undergoes magnetostriction, thereby affecting parameters such as the resonance frequency of the device. The magnitude of the external magnetic field to be measured is sensed by detecting the change in the resonance frequency or related electrical parameters.

[0053] The inverse piezoelectric effect refers to that when an electric field is applied in the polarization direction of the piezoelectric layer, the piezoelectric material in the piezoelectric layer will generate mechanical deformation or mechanical pressure in a certain direction. This mechanical deformation will cause the vibration of the material, thereby exciting acoustic waves. This effect is the reverse process of the direct piezoelectric effect, that is, the conversion between electrical energy and mechanical energy (i.e., acoustic waves). For example, as Figure 1 shown, the magnetic field sensor 100 can generate a transverse electric field in the top electrode layer 130, generating acoustic vibration modes such as transverse profiles and thickness shear.

[0054] Magnetostriction (also known as the magnetostriction effect) refers to that under the action of an external magnetic field, a magnetic material will generate deformation, resulting in a change in the Young's modulus of the magnetic material, also called the ΔE effect. The change in the Young's modulus will affect the resonance frequency of the acoustic resonator, and the change in this resonance frequency will be reflected in the electrical parameters of the magnetic field sensor such as the electromechanical coupling coefficient.

[0055] AsFigure 1 As shown, the magnetic field sensor provided by at least one embodiment of the present disclosure is an acoustic resonator, and its operating frequency is affected by the periodic length of the top electrode layer 130 and the equivalent sound velocity, specifically satisfying the following formula:

[0056]

[0057] where 𝑓 𝑟𝑒𝑠 represents the operating frequency of the magnetic field sensor, represents the equivalent sound velocity of the magnetic field sensor, and 𝜆 represents the periodic length of the top electrode layer. The equivalent sound velocity of the magnetic field sensor is jointly affected by the piezoelectric layer, the top electrode layer, etc.

[0058] As Figure 1 shown, in at least one embodiment of the present disclosure, the top electrode layer 130 includes a first top electrode 130a and a second top electrode 130b. The first top electrode 130a and the second top electrode 130b are separately disposed on the second surface of the piezoelectric layer 120 and respectively at least partially cover the suspended piezoelectric region. For example, as shown in the figure, the first top electrode 130a and the second top electrode 130b are respectively located on two opposite sides of the cavity.

[0059] For example, the first top electrode 130a and the second top electrode 130b can be two opposite rectangles or interdigital structures. It should be noted that the first top electrode and the second top electrode can be of any shape or structure, and the present disclosure does not impose any restrictions on them.

[0060] As Figure 1 shown, in at least one embodiment of the present disclosure, a part of the first top electrode 130a extends beyond the suspended piezoelectric region to form a first terminal, and a part of the second top electrode 130b extends beyond the suspended piezoelectric region to form a second terminal. For example, the first terminal and the second terminal are opposite to each other and are configured to receive an electrical signal and output a response value of the electrical signal. Subsequently, the magnetic field intensity measurement value can be obtained through the response value of the electrical signal. For example, the first terminal can receive an electrical signal, the second terminal can be grounded, and an external circuit is used to receive the electrical signal and read the response value of the electrical signal. For example, when receiving an electrical signal, the externally applied electrical signal can be an alternating current signal, and the corresponding signal application circuit is an alternating current signal application circuit; for example, the external signal reading circuit can read the response value of the electrical signal.

[0061] As Figure 1 shown, in some examples, the top electrode layer 130 can include a magnetic material part and a conductive part. For example, the first top electrode 130a and the second top electrode 130b can include a magnetic material part and a conductive part.

[0062] In some other examples, the top electrode layer 130 can be a layer of a magneto-conductive material. For example, the first top electrode 130a and the second top electrode 130b can be layers of a magneto-conductive material.

[0063] For example, in the case where the top electrode layer 130 includes a magnetic material portion and a conductive portion, the top electrode layer 130 can be a composite structure of a conductive material and a magnetic material. For example, the composite structure can be a stacked structure or an intercalated structure formed by combining a conductive layer and a magnetic material layer. In the above composite structure, the combination manner and the number of layers of the conductive layer and the magnetic material layer are not limited. For example, in the case where the top electrode layer 130 can be a layer of a magneto-conductive material, the magneto-conductive material layer can be a single-layer or multi-layer structure.

[0064] For example, the magneto-conductive material layer can be composed of a magnetic material capable of conducting electricity. The magnetic material capable of conducting electricity can include Metglas, FeGaB, FeGaC, magnetostrictive alloy (Tb-Dy-Fe), nickel (Ni), iron (Fe), iron gallium (FeGa), cobalt iron (CoFe), cobalt ferrite (CoFeO), nickel iron (NiFe), iron aluminum (FeAl), or yttrium iron garnet (YIG), etc. The embodiments of the present disclosure are not limited thereto.

[0065] For example, the substrate material can include silicon (Si) with different crystal orientations, glass, silicon oxide (SiO x ), silicon carbide (SiC), silicon nitride (SiN), diamond, or sapphire, etc. The embodiments of the present disclosure are not limited thereto.

[0066] For example, the piezoelectric layer can be a piezoelectric thin film bonded or directly grown on the substrate; the piezoelectric thin film material can include aluminum nitride (AlN), scandium-doped aluminum nitride (AlScN), zinc oxide (ZnO), gallium nitride (GaN), lead zirconate titanate (PZT), lithium niobate (LiNbO3) with different tangents, or lithium tantalate (LiTaO3), etc. The embodiments of the present disclosure are not limited thereto.

[0067] For example, the piezoelectric layer (i.e., the lower surface of the piezoelectric layer) is connected to the substrate, and a multi-side fixed structure can be formed. When the substrate only penetrates through a pair of opposite surfaces (such as the upper surface and the lower surface), the four sides (i.e., 360 degrees) of the piezoelectric layer are connected to the substrate, forming a fully fixed boundary condition, which can be regarded as being fully fixed by the substrate. And a suspended structure is formed due to selective etching of the substrate in a partial area of the piezoelectric layer, which is called a suspended piezoelectric region. The magnetoelectric heterojunction thin film (i.e., the suspended magnetoelectric heterojunction thin film) integrated on this suspended piezoelectric region can be regarded as a fully fixed support structure (hereinafter referred to as a fully fixed structure).

[0068] The magnetic field sensor provided by at least one embodiment of the present disclosure is different from the magnetic field sensors with traditional structures (such as traditional thin film bulk acoustic resonators or NanoPlate Resonator (NPR) structures, etc.). The periphery of the suspended magnetoelectric heterojunction thin film of the present disclosure can be fixed on multiple sides (such as fully fixed), and the acoustic vibration region can be defined by the boundary of the composite layer of the electrode with a certain thickness and the magnetic material.

[0069] Therefore, the magnetic field sensor provided by at least one embodiment of the present disclosure has extremely strong mechanical stability, is compatible with a variety of high-performance piezoelectric thin film materials, and can be extended to actual complex application scenarios.

[0070] Figure 2A It is a schematic structural diagram of another magnetic field sensor provided by at least one embodiment of the present disclosure. Figure 2B It corresponds to that provided by at least one embodiment of the present disclosure. Figure 2A The exemplary structural diagram of the magnetic field sensor shown. Figure 2A and Figure 2B The embodiments of Figure 1 Compared with the magnetic field sensor 100, a bottom electrode layer 240 is added, and it is a two-side fixed structure.

[0071] Figure 2A and Figure 2B They are schematic diagrams of different angles of the embodiment of the magnetic field sensor 200.

[0072] As Figure 2A and Figure 2B shown, the magnetic field sensor 200 includes a substrate 210, a piezoelectric layer 220, a top electrode layer 230, and a bottom electrode layer 240. The top electrode layer 230 includes a first top electrode 230a and a second top electrode 230b.

[0073] As Figure 2A and Figure 2B shown, the bottom electrode layer 240 is disposed on the first surface of the piezoelectric layer 220 and is located in the cavity, overlapping with the suspended piezoelectric region.

[0074] As Figure 2A and Figure 2B shown, for example, the substrate 210 has a cavity that opens on two opposite surfaces (such as the upper surface and the lower surface) of the substrate 210; the first surface (such as the lower surface) of the piezoelectric layer 220 is disposed on the substrate 210 and covers the cavity, forming a suspended piezoelectric region, wherein the first surface of the piezoelectric layer 220 at least crosses the opening formed by the cavity and contacts the substrate 210.

[0075] As Figure 2A and Figure 2BAs shown, for example, in addition to being penetrated (i.e., the above-mentioned cavity) on two opposite surfaces (such as the upper surface and the lower surface), the other two opposite surfaces (such as the front surface and the back surface) of the substrate 210 can also be penetrated, so that the two sides of the substrate 210 and the piezoelectric layer 220 are in contact with each other, forming a structure fixed on both sides.

[0076] As Figure 2A and Figure 2B shown, for example, the top electrode layer 230 is disposed on the second surface (such as the upper surface) of the piezoelectric layer 220 and at least partially covers the suspended piezoelectric region, and is configured to be fed an electrical signal during operation, generating an electric field in the piezoelectric layer 220 to excite acoustic waves. The top electrode layer 230 has magnetism and undergoes magnetostriction under the action of an external magnetic field to change the response value of the electrical signal. The second surface of the piezoelectric layer 220 is opposite to the first surface.

[0077] As Figure 2A and Figure 2B shown, for example, the top electrode layer 230 includes a first top electrode 230a and a second top electrode 230b. The first top electrode 230a and the second top electrode 230b are separately disposed on the second surface of the piezoelectric layer 220 and at least partially cover the suspended piezoelectric region respectively.

[0078] For example, the first top electrode 230a partially extends beyond the suspended piezoelectric region to form a first terminal (not shown in the figure), and the second top electrode 230b partially extends beyond the suspended piezoelectric region to form a second terminal (not shown in the figure); the first terminal and the second terminal are configured to receive an electrical signal and output the response value of the electrical signal.

[0079] Similarly as Figure 2A and Figure 2B shown, for example, the bottom electrode layer 240 is disposed on the first surface of the piezoelectric layer 220 and is located in the cavity, overlapping with the suspended piezoelectric region. For example, the upper and lower surfaces of the bottom electrode layer 240 can completely coincide with the suspended piezoelectric region.

[0080] [[ID=!27]] Figure 3A FIG. is a schematic top view of an exemplary partial structure of another magnetic field sensor provided by at least one embodiment of the present disclosure. Figure 3B This is provided for at least one embodiment of the present disclosure corresponding to Figure 3A The exemplary structural diagram of the magnetic field sensor shown. Figure 3A and Figure 3B Are schematic diagrams of different angles of an embodiment of the magnetic field sensor 300.

[0081] As Figure 3BAs shown, the magnetic field sensor 300 includes a substrate 310, a piezoelectric layer 320, a top electrode layer 330, and a bottom electrode layer 340. The top electrode layer 330 includes a first top electrode 330a and a second top electrode 330b.

[0082] As Figure 3A and Figure 3B shown, the bottom electrode layer 340 is disposed on the first surface of the piezoelectric layer 220 and is located in the cavity, overlapping with the suspended piezoelectric region.

[0083] As Figure 3A and Figure 3B shown, for example, the substrate 310 only has a cavity that opens on two opposite surfaces (such as the upper surface and the lower surface) of the substrate 310; the first surface (such as the lower surface) of the piezoelectric layer 320 is disposed on the substrate 310 and covers the cavity, forming a suspended piezoelectric region, wherein the first surface of the piezoelectric layer 320 contacts the substrate 310 at least across the opening formed by the cavity.

[0084] For example, as Figure 3A shown, the bottom electrode layer 340 may not completely coincide with the suspended piezoelectric region. For example, the bottom electrode layer 340 may be a wedge-shaped body, that is, the upper surface area of the bottom electrode layer 340 is larger than the lower surface area.

[0085] As Figure 3B shown, the four sides (i.e., 360 degrees) of the piezoelectric layer 320 are all connected to the substrate 310. The top electrode layer 330 - piezoelectric layer 320 - bottom electrode layer 340 form a suspended magnetoelectric heterojunction thin film at the suspended piezoelectric region. The substrate 310 can support it to form a fully fixed structure for the suspended magnetoelectric heterojunction thin film.

[0086] First, the fully fixed structure greatly enhances the mechanical stability of the suspended magnetoelectric heterojunction thin film; second, the fully fixed structure can effectively prevent the warping of the suspended magnetoelectric heterojunction thin film due to stress after release, improving the uniformity and stability of the device; finally, the structure proposed in at least one embodiment of the present disclosure is based on a whole layer of piezoelectric thin film material on the substrate. Therefore, various high-performance and low-stress piezoelectric thin film materials can be used, such as transferred single-crystal lithium niobate, lithium tantalate thin films, or quasi-single-crystal aluminum nitride materials grown on the substrate, etc. Traditional thin film bulk acoustic resonators often grow piezoelectric materials on patterned electrodes and are not compatible with the above high-performance or low-stress piezoelectric materials.

[0087] For example, in at least one embodiment of the present disclosure, the bottom electrode layer may be a non-magnetic conductive layer or a magnetic conductive layer.

[0088] For example, in the case where the bottom electrode layer is a non-magnetic conductive layer, the bottom electrode layer may be a metal electrode, such as titanium (Ti), aluminum (Al), copper (Cu), platinum (Pt), molybdenum (Mo), gold (Au), silver (Ag), etc. or their alloys. The embodiments of the present disclosure are not limited thereto.

[0089] For example, in the case where the bottom electrode layer is a conductive layer with magnetism, the bottom electrode layer may be a magneto-conductive material layer, or the bottom electrode layer may include a magnetic material part and a conductive part. Examples of the above magneto-conductive material layer and the magnetic material part and the conductive part can refer to the relevant descriptions of the above top electrode layer, and will not be elaborated here.

[0090] The magnetic field sensor provided by at least one embodiment of the present disclosure can apply an electrical signal and ground respectively through the first top electrode and the second top electrode. By using the bottom electrode layer, an electric field in the thickness direction (z direction) can be introduced into the piezoelectric layer. Among them, the electric field directions below the first top electrode and the second top electrode are opposite. Therefore, when the magnetic field sensor structure provided by at least one embodiment of the present disclosure is adopted, an electric field excitation in the thickness direction can be applied under the condition that the electrical signal is not connected to the bottom electrode layer and only connected to the top electrode layer, greatly reducing the complexity of the manufacturing process. Under the electric field excitation in the thickness direction, the piezoelectric layer generates the inverse piezoelectric effect and excites body acoustic waves, forming an acoustic resonance in the thickness direction at the suspended piezoelectric region. Since the electric field directions below the first top electrode and the second top electrode are opposite, the generated mechanical displacements are also opposite.

[0091] The electrode layer of the magnetic field sensor (including the top electrode layer and the bottom electrode layer, and the top electrode layer and the bottom electrode layer may be magneto-conductive material layers, or include a magnetic material part and a conductive part) and the piezoelectric layer form an acoustic resonance cavity. Since the above resonance cavity is a structure formed by alternately stacking different materials, it is also called a multi-layer heterojunction. Thus, through appropriate thickness design, various high-order acoustic resonances (high-order resonance modes) can be generated. The magnetic field sensor structure proposed by at least one embodiment of the present disclosure supports acoustic resonance modes with different vibration directions propagating in the thickness direction, is compatible with a variety of piezoelectric materials, and can achieve extremely high device performance through the collaborative design of the piezoelectric layer and the magnetic material.

[0092] In the above acoustic resonance cavity, in the case where the bottom electrode layer is a conductive layer with magnetism, the material combinations of the top electrode layer and the bottom electrode layer may include the following cases:

[0093] (1) Both the top electrode layer and the bottom electrode layer are magneto-conductive material layers;

[0094] (2) The top electrode layer is a magneto-conductive material layer, and the bottom electrode layer includes a magnetic material part and a conductive part;

[0095] (3) Both the top electrode layer and the bottom electrode layer include a magnetic material portion and a conductive portion;

[0096] (4) The top electrode layer includes a magnetic material portion and a conductive portion, and the bottom electrode layer is a magneto-conductive material layer.

[0097] In the above examples, the magnetic material portion and / or the magneto-conductive material layer in the magnetic field sensor can be referred to as the magnetic layer of the magnetic field sensor. For example, in case (1), the magnetic layer includes two magneto-conductive material layers at the top and bottom; in case (2), the magnetic layer includes the magneto-conductive material layer at the top and the magnetic material portion at the bottom; in case (3), the magnetic layer includes the magnetic material portion at the top and the magnetic material portion at the bottom; in case (4), the magnetic layer includes the magnetic material portion at the top and the magneto-conductive material layer at the bottom.

[0098] In the above cases, both the top electrode layer and the bottom electrode layer are magnetic, and the thickness of the conductive portion is almost negligible. Thus, the thickness of the magnetic layer can be equivalent to the sum of the thickness of the top electrode layer and the thickness of the bottom electrode layer.

[0099] For example, in at least one embodiment of the present disclosure, the ratio of the thickness of the magnetic layer to the thickness of the piezoelectric layer is equal to the ratio of the sound velocity of the acoustic wave in the magnetic layer to the sound velocity in the piezoelectric layer. For example, in the case where the bottom electrode layer is a magnetic conductive layer, the magnetic layer includes the magnetic material portion and / or the magneto-conductive material layer in the top electrode layer and the bottom electrode layer (specifically, see the above examples), and the thickness of the magnetic layer can be equivalent to the sum of the thickness of the top electrode layer and the thickness of the bottom electrode layer. In the above design, for example, when the bulk acoustic wave velocity of the magnetic layer is a times (usually a < 1) the bulk acoustic wave velocity of the piezoelectric layer, the thickness of the designed magnetic layer is also approximately a times the thickness of the piezoelectric layer. At this time, the resonator excites the second-order bulk acoustic wave mode, and a standing wave period is formed in each of the magnetic layer and the piezoelectric layer. Compared with the first-order bulk acoustic wave resonance mode, the resonance frequency and the electromechanical coupling coefficient of this mode will not be significantly reduced due to the introduction of a thicker magnetic layer, affecting the detection resolution.

[0100] For example, in addition to designing the thicknesses of the piezoelectric layer and the magnetic layer to be proportional to their sound velocities, another design scheme can be to reduce the thickness of the piezoelectric layer. For example, in at least one embodiment of the present disclosure, the thickness of the magnetic layer is the same as the thickness of the piezoelectric layer. For example, in the case where the bottom electrode layer is a magnetic conductive layer, the magnetic layer includes the magnetic material portion and / or the magneto-conductive material layer in the top electrode layer and the bottom electrode layer (specifically, see the above examples), and the thickness of the magnetic layer can be equivalent to the sum of the thickness of the top electrode layer and the thickness of the bottom electrode layer.

[0101] The magnetic field sensor provided by at least one embodiment of the present disclosure, firstly, has a higher quality factor compared to surface acoustic wave mode sensors, and can improve the detection accuracy of the resonant frequency of the sensor. Secondly, bulk acoustic wave resonators often have a higher frequency. The bulk acoustic wave resonance mode adopted makes the sensitivity of the resonant frequency to the magnetostrictive material parameters stronger than that of the traditional surface acoustic wave mode. Therefore, it has a higher detection sensitivity. Thirdly, by reducing the thickness of the piezoelectric layer (for example, making the thickness of the piezoelectric layer equivalent to the thickness of the magnetic layer) and increasing the proportion of the magnetic layer in the entire resonant cavity, the interaction between the magnetic material and the bulk acoustic wave can be improved, thereby improving the sensing sensitivity. Finally, by designing higher-order resonance modes, the frequency can be further increased, thereby enhancing the detection sensitivity of the device to the magnetic field.

[0102] The present disclosure also provides an electronic device, which includes the magnetic field sensor of any one of the above embodiments.

[0103] Figure 4 It is a schematic block diagram of an electronic device provided by at least one embodiment of the present disclosure.

[0104] As Figure 4 shown, the electronic device 400 includes a magnetic field sensor 410. The magnetic field sensor 410 can include, for example, the magnetic field sensor 100, the magnetic field sensor 200, or the magnetic field sensor 300 provided by any one of the above embodiments.

[0105] For example, as Figure 4 shown, in at least one embodiment of the present disclosure, the electronic device 400 further includes a readout circuit 420, which is configured to receive and analyze the response value of the electrical signal to obtain a magnetic field intensity measurement value.

[0106] For example, as Figure 4 shown, the electronic device 400 may further include a signal application circuit 430, which is configured to apply an electrical signal to the magnetic field sensor.

[0107] For example, the signal application circuit 430 can be an alternating current signal application circuit, and can include modules such as signal generation and power amplification.

[0108] For example, the readout circuit 420 can include modules such as sweep frequency generation, mixing and detection, amplitude and phase detection, and digital processing.

[0109] For example, when the electrical signal applied by the signal application circuit, that is, the electrical signal received by the magnetic field sensor, is a broadband signal, that is, a signal with a frequency range change (for example, a sweep signal from low frequency to high frequency) is input, so that it generates a response interacting with the magnetic field. The readout circuit can find the resonant frequency point of the magnetic field sensor and its amplitude change by analyzing the collected signal.

[0110] For another example, when the electrical signal applied by the signal application circuit, i.e., received by the magnetic field sensor, is a fixed-frequency signal, that is, a fixed-frequency signal is input, the resonant frequency of the magnetic field sensor shifts with the change of the magnetic field, resulting in a change in the amplitude or phase of the output signal. The readout circuit can indirectly calculate the magnetic field strength by measuring the amplitude attenuation or phase difference.

[0111] At least one embodiment of the present disclosure further provides a method for manufacturing a magnetic field sensor, and this manufacturing method can be used to manufacture the magnetic field sensor provided in the above at least one embodiment.

[0112] Figure 5 It is a schematic flowchart of a method for manufacturing a magnetic field sensor provided in at least one embodiment of the present disclosure. As Figure 5 shown, this manufacturing method includes steps S501 - S504.

[0113] Step S501: Provide a substrate.

[0114] Step S502: Form a piezoelectric layer on one side of the substrate.

[0115] For example, the substrate can be disposed on the first surface of the piezoelectric layer. For example, a piezoelectric layer can be formed on the upper surface of the substrate, and the lower surface of the piezoelectric layer is in contact with the upper surface of the substrate.

[0116] Step S503: Form a top electrode layer on the second surface of the piezoelectric layer.

[0117] For example, the top electrode layer can be configured to be fed an electrical signal during operation, generate an electric field in the piezoelectric layer to excite acoustic waves, the top electrode layer has magnetism and undergoes magnetostriction under the action of an external magnetic field to change the response value of the electrical signal, and the second surface of the piezoelectric layer is opposite to the first surface.

[0118] Step S504: Remove a part of the substrate to form a cavity that is open on two opposite surfaces of the substrate.

[0119] For example, the first surface of the piezoelectric layer is disposed on the substrate and covers the cavity, forming a suspended piezoelectric region; for example, the first surface of the piezoelectric layer at least spans the opening formed by the cavity and is in contact with the substrate.

[0120] For example, in some embodiments of the manufacturing method of the present disclosure, step S502 further includes directly growing a piezoelectric layer on the substrate or transferring and bonding the piezoelectric layer to the substrate.

[0121] For example, in some embodiments of the manufacturing method of the present disclosure, step S505 can also be included.

[0122] Step S505: Form a bottom electrode layer on the first surface of the piezoelectric layer.

[0123] For example, the bottom electrode layer overlaps with the suspended piezoelectric region and is located in the cavity.

[0124] Figure 6 FIG. is a schematic flow chart of a preparation process of a magnetic field sensor provided by at least one embodiment of the present disclosure, which is Figure 5 a specific process example of the preparation method.

[0125] Figure 7 FIG. is a schematic diagram of a preparation process of a magnetic field sensor provided by at least one embodiment of the present disclosure, which is Figure 5 a specific process example of the preparation method.

[0126] Next, in conjunction with Figure 6 and Figure 7 will be described in further detail with respect to Figure 5 steps S501-S504 in

[0127] As shown in Figure 6 and Figure 7 , first, steps S501 and S502 are performed, that is, a substrate is provided and a piezoelectric layer is formed on one side of the substrate. The technology of preparing a piezoelectric layer on an insulator substrate (Piezoelectric-on-Insulator, POI) is adopted. For example, a layer of piezoelectric thin film material (also referred to as a piezoelectric layer) on a silicon substrate can be prepared by means of growth or bonding transfer. The above process corresponds to Figure 7 "1" in Figure 7 . The cutoff layer in

[0128] is only a specific functional layer that appears during the preparation process and is used to control the process boundary during material growth, transfer, or etching. It does not add any limitation to the working area of the magnetic field sensor. Figure 6 and Figure 7 , second, step S503 is performed, that is, a top electrode layer is prepared. For example, it includes top electrode layer lithography (corresponding to Figure 7 "2" in Figure 7 ), sputtering of the top electrode and the magnetic material, and electrode stripping (corresponding to

[0129] "3" in Figure 6 and Figure 7 ), etc. Figure 7operations such as the "4" in []]. For example, methods such as deep silicon etching, deep reactive ion etching (DRIE), or wet anisotropic etching can be used to pattern and etch from the back of the substrate to completely remove the substrate under the device area (or etch to a stop layer such as silicon oxide, etc.).

[0130] such as Figure 6 and Figure 7 As shown, then, if a stop layer remains at this time, stop layer etching is performed. For example, the stop layer can be further removed by an etching process to expose the lower surface of the piezoelectric layer (corresponding to Figure 7 the "5" in []].

[0131] such as Figure 6 and Figure 7 As shown, finally, step S505 can also be performed, that is, a bottom electrode layer is formed on the first surface of the piezoelectric layer. For example, it includes operations such as bottom electrode growth (i.e., Figure 6 back electrode growth in []]). For example, by deposition film methods such as sputtering and evaporation, the bottom electrode (or / and magnetic material) enters from the back deep hole and is deposited on the lower surface of the piezoelectric layer to form a bottom electrode layer of the suspended piezoelectric region (corresponding to Figure 7 the "6" in []].

[0132] It should be noted that the descriptions of the materials used for the piezoelectric layer, substrate, magnetic material, etc. of the magnetic field sensor provided by the embodiments of the present disclosure should not be construed as a limitation of the present disclosure.

[0133] The manufacturing method of the magnetic field sensor provided by at least one embodiment of the present disclosure, based on the magnetic field sensor structure proposed by the present disclosure and combined with the proposed process scheme, is suitable for using high-quality piezoelectric thin films transferred or deposited on the substrate, avoiding the difficulty of obtaining high-quality piezoelectric thin films in bulk acoustic wave resonators; further, based on the thin film piezoelectric layer on the substrate, release and self-alignment of the bottom suspended electrode are completed through back etching, and the process is simple and fast.

[0134] Figure 8 It is a schematic curve diagram showing the change of the admittance of a magnetic field sensor provided by at least one embodiment of the present disclosure with respect to the elastic modulus of the magnetic material. Figure 8 The abscissa in [] is the frequency (MHz), the ordinate is the admittance amplitude, different curves represent different elastic modulus values, and the peak represents the resonance frequency of the magnetic field sensor.

[0135] such as Figure 8As shown, there are two acoustic modes in the magnetic field sensor within a frequency range, namely the first-order and second-order shear bulk acoustic wave modes. The resonance frequencies of both modes change with the elastic modulus of the magnetic material, with different degrees of change. This change can be detected in various ways. For example, a broadband signal is input into the magnetic field sensor, the frequency response of the magnetic field sensor is read, and the changes in the resonance frequency and amplitude can be obtained through analysis. Another example is to input a fixed-frequency signal into the magnetic field sensor. Under the action of an external magnetic field, due to the shift of the resonance frequency, the admittance value at this frequency point changes, so that the change in the amplitude or phase of the output signal can be read, and the magnetic field strength can be obtained through analysis.

[0136] Due to the high acoustic quality factor of the resonance-type magnetic field sensor based on bulk acoustic waves, the strong interaction between the acoustic wave and the magnetic material, the large change in the admittance of the magnetic field sensor under a fixed-frequency signal, and the high sensitivity, it is suitable for detecting weak magnetic fields.

[0137] Although the present disclosure has been described in detail with general descriptions and specific embodiments above, based on the embodiments of the present disclosure, some modifications or improvements can be made, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present disclosure all fall within the scope claimed by the present disclosure.

[0138] Regarding the present disclosure, the following points need to be noted:

[0139] (1) The drawings of the embodiments of the present disclosure only relate to the structures involved in the embodiments of the present disclosure, and other structures can refer to the general design.

[0140] (2) For the sake of clarity, in the drawings used to describe the embodiments of the present disclosure, the thickness of the layer or region is enlarged or reduced, that is, these drawings are not drawn according to the actual scale.

[0141] (3) Without conflict, the embodiments of the present disclosure and the features in the embodiments can be combined with each other to obtain new embodiments.

[0142] The above is only the specific implementation manner of the present disclosure, but the protection scope of the present disclosure is not limited thereto. The protection scope of the present disclosure should be subject to the protection scope of the claimed rights.

Claims

1. A magnetic field sensor, comprising a substrate, a piezoelectric layer, and a top electrode layer, wherein, the substrate has cavities that open on two opposite surfaces of the substrate; a first surface of the piezoelectric layer is disposed on the substrate and covers the cavities, forming a suspended piezoelectric region, wherein the first surface of the piezoelectric layer at least crosses the openings formed by the cavities and contacts the substrate; the top electrode layer is disposed on a second surface of the piezoelectric layer and at least partially covers the suspended piezoelectric region, and is configured to be fed with an electrical signal during operation, generate an electric field in the piezoelectric layer to excite acoustic waves, the top electrode layer is magnetic and magnetostricts under the action of an external magnetic field to change the response value of the electrical signal, wherein the second surface of the piezoelectric layer is opposite to the first surface.

2. The magnetic field sensor according to claim 1, wherein The top electrode layer includes a first top electrode and a second top electrode, the first top electrode and the second top electrode are separately disposed on the second surface of the piezoelectric layer, and respectively at least partially cover the suspended piezoelectric region.

3. The magnetic field sensor according to claim 2, wherein, The first top electrode partially extends beyond the suspended piezoelectric region to form a first terminal, and the second top electrode partially extends beyond the suspended piezoelectric region to form a second terminal; wherein the first terminal and the second terminal are configured to receive the electrical signal and output the response value of the electrical signal.

4. The magnetic field sensor according to claim 1, wherein The top electrode layer includes a magnetic material portion and a conductive portion; or The top electrode layer is a magneto-conductive material layer.

5. The magnetic field sensor according to any one of claims 1-4, further comprising: a bottom electrode layer, disposed on the first surface of the piezoelectric layer and located in the cavities, overlapping with the suspended piezoelectric region.

6. The magnetic field sensor according to claim 5, wherein, The bottom electrode layer is a non-magnetic conductive layer or a magnetic conductive layer, and in the case where the bottom electrode layer is a magnetic conductive layer, the bottom electrode layer is a magneto-conductive material layer or includes a magnetic material portion and a conductive portion.

7. The magnetic field sensor according to claim 5, wherein, The magnetic field sensor includes a magnetic layer, the ratio of the thickness of the magnetic layer to the thickness of the piezoelectric layer is equal to the ratio of the sound velocity of the acoustic wave in the magnetic layer to the sound velocity in the piezoelectric layer, wherein the magnetic layer includes the magnetic material portion and / or the magneto-conductive material layer in the magnetic field sensor; or. the thickness of the magnetic layer is the same as the thickness of the piezoelectric layer, wherein the magnetic layer includes the magnetic material portion and / or the magneto-conductive material layer in the magnetic field sensor.

8. An electronic device, comprising the magnetic field sensor according to any one of claims 1-7.

9. The electronic device according to claim 8, further comprising: a readout circuit, configured to receive and analyze the response value of the electrical signal to obtain a magnetic field strength measurement value.

10. The electronic device according to claim 8, further comprising: a signal application circuit, configured to apply an electrical signal to the magnetic field sensor.

11. A method for manufacturing a magnetic field sensor, comprising: providing a substrate; forming a piezoelectric layer on one side of the substrate, wherein the substrate is disposed on the first surface of the piezoelectric layer; A top electrode layer is formed on the second surface of the piezoelectric layer. The top electrode layer is configured to be fed with an electrical signal during operation, generate an electric field in the piezoelectric layer to excite acoustic waves. The top electrode layer has magnetism and undergoes magnetostriction under the action of an external magnetic field to change the response value of the electrical signal. The second surface of the piezoelectric layer is opposite to the first surface; Part of the substrate is removed to form a cavity that is open on two opposite surfaces of the substrate. The first surface of the piezoelectric layer is disposed on the substrate and covers the cavity, forming a suspended piezoelectric region; Wherein, the first surface of the piezoelectric layer contacts the substrate at least across the opening formed by the cavity.

12. The preparation method according to claim 11, wherein Forming the piezoelectric layer on one side of the substrate includes: Growing the piezoelectric layer directly on the substrate, or Transfer-bonding the piezoelectric layer to the substrate.

13. The preparation method according to claim 11 further includes: Forming a bottom electrode layer on the first surface of the piezoelectric layer, wherein the bottom electrode layer overlaps with the suspended piezoelectric region and is located in the cavity.

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