Magnetic field sensor and method for manufacturing a magnetic field sensor, electronic device

Abstract

The application provides a magnetic field sensor, a preparation method thereof and an electronic device. The magnetic field sensor comprises an acoustic resonator and a magnetic field adjustable capacitor array. The magnetic field adjustable capacitor array is connected in series or parallel with the acoustic resonator. The magnetic field adjustable capacitor array comprises a plurality of magnetic field adjustable capacitors connected in parallel. The magnetic field adjustable capacitor comprises a bottom electrode and a magnetostrictive cantilever beam. The magnetostrictive cantilever beam and the bottom electrode are clamped with an air layer. Under an applied magnetic field, the magnetostrictive cantilever beam is bent, the distance between the magnetostrictive cantilever beam and the bottom electrode changes, the capacitance of the magnetic field adjustable capacitor array changes, and the resonance frequency or signal amplitude of the series or parallel system of the magnetic field adjustable capacitor array and the acoustic resonator changes. The application decouples the magnetic material from the acoustic resonator, retains the high sensitivity of the cantilever beam and the high quality factor of the resonator, and can improve the sensitivity of the sensor system to the magnetic field, reduce the noise, and reduce the detection limit.

Description

Technical Field

[0001] This application relates to the field of sensor technology, and in particular to a magnetic field sensor, its preparation method, and an electronic device. Background Technology

[0002] Existing magnetic field sensors (including SQUID (Superconducting Quantum Interference Device), OPM (Optically Pumped Magnetometer), Hall magnetic field sensors, AMR (Anisotropic Magnetoresistance), GMR (Giant Magnetoresistance), TMR (Tunneling Magnetoresistance), etc.) have problems such as high detection limits, high power consumption, difficulty in miniaturization and integration, and limitations between the sensitive area and the measurement limit. They cannot meet the requirements for small-size, highly integrated, highly sensitive, low-detection-limit, and low-power magnetic field sensors. Summary of the Invention

[0003] The purpose of this application is to provide a magnetic field sensor and its preparation method, as well as an electronic device, which can solve at least one of the technical problems mentioned in the prior art.

[0004] One aspect of this application provides a magnetic field sensor. The magnetic field sensor includes an acoustic resonator and a magnetic field adjustable capacitor array. The magnetic field adjustable capacitor array is connected in series or parallel with the acoustic resonator. The magnetic field adjustable capacitor array includes multiple magnetic field adjustable capacitors connected in parallel. Each magnetic field adjustable capacitor includes a bottom electrode and a magnetostrictive cantilever beam. An air layer is sandwiched between the magnetostrictive cantilever beam and the bottom electrode. Under an applied magnetic field, the magnetostrictive cantilever beam bends, changing the distance between the magnetostrictive cantilever beam and the bottom electrode. This changes the capacitance of the magnetic field adjustable capacitor array, causing a change in the resonant frequency or signal amplitude of the series or parallel system of the magnetic field adjustable capacitor array and the acoustic resonator.

[0005] Furthermore, one end of the magnetostrictive cantilever beam is supported and the other end is suspended; or, both ends of the magnetostrictive cantilever beam are supported and the middle is suspended.

[0006] Furthermore, the structure of the magnetostrictive cantilever beam is a bulk magnetostrictive metal or alloy material; or, the structure of the magnetostrictive cantilever beam is a composite material formed by bonding a bulk magnetostrictive metal or alloy material to a substrate; or, the structure of the magnetostrictive cantilever beam is a deposited or bonded magnetostrictive thin film material; or, the structure of the magnetostrictive cantilever beam is a composite material formed by depositing or bonding a magnetostrictive thin film material on a substrate.

[0007] Furthermore, the magnetostrictive material in the magnetostrictive cantilever beam includes one or more of the following magnetostrictive metals and alloys: metallic glass, iron gallium boron, iron gallium carbon, iron cobalt silicon boron, terbium-dysprosium-iron ternary alloy, nickel, iron, iron gallium, cobalt iron, cobalt iron oxygen, cobalt iron boron, nickel iron, iron aluminum, and yttrium iron garnet. The substrate material in the magnetostrictive cantilever beam includes single-crystal and polycrystalline silicon, silicon oxide, silicon carbide, silicon nitride, diamond, or sapphire.

[0008] Furthermore, the acoustic resonator includes a surface acoustic wave resonator, a bulk acoustic wave resonator, or a Lamb wave resonator.

[0009] Furthermore, the piezoelectric layer in the acoustic resonator is a bulk piezoelectric material, or the piezoelectric layer is a piezoelectric thin film material, which is bonded or grown on a substrate to form a composite structure substrate.

[0010] Furthermore, the bulk piezoelectric material includes lead zirconate titanate, lead magnesium niobate-lead titanate, lithium niobate with different tangential orientations, lithium tantalate, or quartz.

[0011] Furthermore, the materials of the piezoelectric thin film include aluminum nitride, zinc oxide, gallium nitride, lead zirconate titanate, lithium niobate or lithium tantalate with different tangential orientations; the materials of the composite structure substrate include silicon, silicon oxide, silicon carbide, silicon nitride, diamond or sapphire.

[0012] Furthermore, the materials of the bottom electrode in the magnetic field adjustable capacitor and the electrodes in the acoustic resonator include titanium, aluminum, copper, platinum, molybdenum, gold, or silver.

[0013] Furthermore, the magnetic field sensor includes multiple adjustable magnetic field capacitors of the same frequency connected in parallel, which enhances the sensitivity of the magnetic field sensor; or, the magnetic field sensor includes multiple adjustable magnetic field capacitors of different frequencies connected in parallel, which adjusts the frequency bandwidth of the sensing magnetic field of the system; or, the magnetic field sensor includes multiple adjustable magnetic field capacitors of the same frequency and multiple adjustable magnetic field capacitors of different frequencies connected in parallel, which adapts to the magnetic field sensing response requirements in different scenarios.

[0014] Another aspect of this application provides an electronic device. The electronic device includes a magnetic field sensor as described above.

[0015] Another aspect of this application provides a method for fabricating a magnetic field sensor. The method includes: Fabricating an acoustic resonator includes: etching a recess on a substrate; filling the recess with a sacrificial layer; sequentially growing a lower electrode, a piezoelectric layer, and a top electrode on the sacrificial layer; and etching away the sacrificial layer to form a cavity. Fabricating a magnetic field-tunable capacitor array includes: growing a bottom electrode on a printed circuit board; cutting a magnetostrictive material to obtain multiple magnetostrictive cantilever beams; mounting and fixing the multiple magnetostrictive cantilever beams at intervals on the printed circuit board, with the multiple magnetostrictive cantilever beams positioned opposite to the bottom electrode, and an air layer sandwiched between the magnetostrictive cantilever beams and the bottom electrode; wherein, under an applied magnetic field, the magnetostrictive cantilever beams bend, the distance between the magnetostrictive cantilever beams and the bottom electrode changes, and the capacitance of the magnetic field-tunable capacitor array changes. The acoustic resonator is connected in series or in parallel with the magnetic field adjustable capacitor array to form a magnetic field sensor.

[0016] Another aspect of this application provides a method for fabricating a magnetic field sensor. The method includes: Fabricating an acoustic resonator includes: etching a recess on a first substrate; filling the recess with a sacrificial layer; sequentially growing a lower electrode, a piezoelectric layer, and an upper electrode on the sacrificial layer; and etching away the sacrificial layer to form a cavity. Fabricating a magnetic field-tunable capacitor array includes: growing a bottom electrode on a second substrate; forming a sacrificial layer on the bottom electrode; forming a magnetostrictive material or a composite magnetostrictive material at intervals on the sacrificial layer; etching away the sacrificial layer to form a plurality of magnetostrictive cantilever beams, wherein the plurality of magnetostrictive cantilever beams are positioned opposite to the bottom electrode, wherein, under an applied magnetic field, the magnetostrictive cantilever beams bend, the distance between the magnetostrictive cantilever beams and the bottom electrode changes, and the capacitance of the magnetic field-tunable capacitor array changes; The acoustic resonator is connected in series or in parallel with the magnetic field adjustable capacitor array to form a magnetic field sensor.

[0017] Furthermore, the first substrate and the second substrate are two different substrates; or, the first substrate and the second substrate are two different regions of the same substrate.

[0018] This application discloses one or more magnetic field sensors and their fabrication methods, as well as electronic devices. These sensors consist of multiple magnetic field adjustable capacitors, each composed of a top magnetostrictive cantilever arm and a bottom electrode, connected in parallel to form an array. By connecting the magnetic field adjustable capacitor array in series or in parallel with a high-resonance-frequency, high-quality-factor acoustic resonator, direct contact between the magnetic material and the resonant device is avoided, thereby improving the sensor's sensitivity and reducing noise and detection limits.

[0019] The magnetic field sensors and their fabrication methods and electronic devices disclosed in this application can significantly improve the sensitivity of magnetic field sensors to magnetic fields by connecting multiple magnetic field adjustable capacitors in parallel to form an array.

[0020] This application discloses one or more magnetic field sensors and their fabrication methods, as well as electronic devices. By decoupling the resonator from the magnetostrictive material, it inherits the high resonant frequency and quality factor of the resonator, suppresses sensor noise, and reduces the sensor's detection limit. This solves the problems of low sensitivity, low quality factor, and high detection limit of existing acoustic resonant magnetic field sensors. This application can meet the detection needs of DC or low-frequency weak magnetic field signals in fields such as aerospace exploration, marine monitoring, geomagnetic exploration, and biomedicine. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a magnetic field sensor according to an embodiment of this application.

[0022] Figure 2 This is a schematic diagram of the structure of a magnetic field adjustable capacitor according to an embodiment of this application.

[0023] Figure 3 This is an MBVD circuit model diagram of a magnetic field sensor based on a series structure of a magnetic field adjustable capacitor and an acoustic resonator according to an embodiment of this application.

[0024] Figure 4 This is a schematic diagram of the structure of a cavity-type thin-film bulk acoustic resonator according to an embodiment of this application.

[0025] Figure 5 This is a schematic diagram of a magnetic field sensor according to another embodiment of this application.

[0026] Figure 6 This is a flowchart illustrating a method for fabricating a magnetic field sensor according to an embodiment of this application.

[0027] Figure 7 This is a flowchart illustrating a method for fabricating a magnetic field sensor according to another embodiment of this application.

[0028] Figure 8 The resonant frequency of a magnetic field sensor according to one embodiment of this application varies with the magnetic field adjustable capacitance. Detailed Implementation

[0029] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses consistent with some aspects of this application as detailed in the appended claims.

[0030] Among non-acoustic resonant magnetic field sensors, SQUID (Superconducting Quantum Interferometer) is essentially a flux sensor that converts magnetic flux into voltage. Its basic principle is based on the superconducting Josephson effect and the phenomenon of magnetic flux quantization. OPM (Optical Pumped Magnetometer) is based on the fact that certain elements can undergo magnetic resonance absorption under specific conditions (called optical pumping absorption), and the frequency of the electromagnetic field absorbed by optical pumping is proportional to the strength of the external magnetic field. The value of the external magnetic field can be obtained from this frequency. Hall magnetic field sensors are magnetic field sensors made using the Hall effect of some semiconductor materials. The Hall effect refers to the phenomenon that when current passes through a conductor located in a magnetic field... When a conductor is in a magnetic field, a potential is generated perpendicular to the direction of the current and the external magnetic field. An AMR (Anisotropic Magnetoresistance) sensor is a magnetic field sensor made by using anisotropic materials to sense changes in the magnetic field based on the magnetoresistance effect. AGMR (Giant Magnetoresistance) magnetic field sensor utilizes the giant magnetoresistance effect of certain magnetic or alloy materials, that is, the phenomenon that the resistance of these materials changes greatly under the action of a certain magnetic field. TMR (Tunnel Magnetoresistance) magnetic field sensor uses the tunnel magnetoresistance effect of magnetic multilayer film materials to sense the magnetic field. The magnetic tunneling resistance effect uses MTJ (Magnetic Tunnel Junction) prepared by multilayer thin film preparation technology as a magnetic sensing element. The general structure of MTJ is a "sandwich" structure of ferromagnetic layer-non-magnetic insulating layer-ferromagnetic layer.

[0031] Acoustic resonant magnetic field sensors are mainly composed of piezoelectric and magnetostrictive materials, operating at the acoustic resonant frequency of the device. They are divided into two categories: active and passive magnetic field sensors. The working principle of passive acoustic resonant magnetic field sensors is that under the action of an external alternating magnetic field, the magnetic material undergoes periodic deformation due to the magnetostrictive effect, causing acoustic resonance of the magnetoelectric composite structure. As a result, due to the piezoelectric effect, the piezoelectric layer generates an electrical signal output. The magnitude of the external magnetic field to be measured is sensed by detecting the magnitude of the output electrical signal. The working principle of active acoustic resonant magnetic field sensors is to sense the magnitude of the magnetic field by detecting changes in the device's resonant frequency or related electrical parameters under the action of the external magnetic field to be measured.

[0032] However, the above-mentioned magnetic field sensors have the following drawbacks: SQUID and OPM have extremely high measurement accuracy and extremely high magnetic field detection limit, approximately fT (fetates), but they are large in size, operate in low-temperature environments, and are difficult to miniaturize and integrate. Hall elements have advantages such as simple principle, small size, low power consumption, high reliability and low cost, but their magnetic field detection limit is limited by physical properties, only μT (micro Tesla), which cannot meet the requirements of high-precision magnetic field measurement. Micro magnetic sensors based on the magnetoresistive effect include AMR, GMR and TMR, which have the advantages of small size and easy integration, but have poor magnetic field detection limit; Fluxgate sensors and induced magnetic field sensors have simple working principles and are easy to manufacture, but there is a serious contradiction between device sensitivity and size, and the magnetic field resolution is relatively poor. Passive magnetic field sensors based on acoustic resonance have high detection sensitivity to external AC magnetic fields at the resonant frequency. However, there is a contradiction in the size of the magnetic thin film material: if the area is too small, the maximum deformation of the film will decrease and the magnetic focusing effect will be weakened, which is not conducive to the detection of magnetic fields; while if the area is too large, the overall intrinsic resonant frequency of the magnetoelectric heterojunction will decrease and the maximum frequency shift under the applied magnetic field will decrease, resulting in a decrease in sensitivity. Active magnetic field sensors based on acoustic resonance (such as surface acoustic wave magnetic field sensors and thin-film bulk acoustic wave magnetic field sensors) combine magnetostrictive thin film materials with acoustic resonators to achieve the detection of DC or low-frequency magnetic fields. However, magnetostrictive thin film materials have disadvantages such as low intrinsic resonant frequency and high loss, which will reduce the resonant frequency and quality factor of the sensor, while increasing noise and raising the detection limit, which is not conducive to magnetic field sensing.

[0033] In view of this, this application proposes an improved magnetic field sensor that can solve at least one of the technical problems mentioned above regarding the magnetic field sensor.

[0034] The magnetic field sensor of this application is connected in series or parallel with an acoustic resonator and a magnetic field adjustable capacitor array, decoupling the magnetic material from the resonator. This retains the high sensitivity of the magnetostrictive cantilever beam structure and the high quality factor of the acoustic resonator, thereby improving the overall sensor system sensitivity, reducing noise, and lowering the detection limit.

[0035] The magnetic field sensor, its fabrication method, and electronic device of this application will now be described in detail with reference to the accompanying drawings. Unless otherwise specified, the features in the following embodiments and implementations can be combined with each other.

[0036] Figure 1 A schematic diagram of a magnetic field sensor 100 according to one embodiment of this application is shown. (As...) Figure 1As shown, a magnetic field sensor 100 according to one embodiment of this application includes an acoustic resonator 110 and a magnetic field adjustable capacitor array 120. The magnetic field adjustable capacitor array 120 is connected in series with the acoustic resonator 110. The magnetic field adjustable capacitor array 120 includes a plurality of magnetic field adjustable capacitors Cs connected in parallel, such as magnetic field adjustable capacitors Cs1, Cs2, ..., Csn.

[0037] Figure 2 A schematic diagram of the structure of a magnetic field adjustable capacitor Cs according to an embodiment of this application is shown. Figure 2 As shown, a magnetic field adjustable capacitor Cs in one embodiment of this application includes a magnetostrictive cantilever beam 121 and a bottom electrode 122, with an air layer 123 sandwiched between the magnetostrictive cantilever beam 121 and the bottom electrode 122.

[0038] Under an applied magnetic field, the magnetostrictive cantilever beam 121 will strain and bend due to the magnetostrictive effect. This changes the distance between the magnetostrictive cantilever beam 121 and the bottom electrode 122, altering the capacitance of the magnetic field-adjustable capacitor array 120. Consequently, the resonant frequency or signal amplitude of the series or parallel system of the magnetic field-adjustable capacitor array 120 and the acoustic resonator 110 changes. Different magnetic field strengths result in different degrees of bending of the magnetostrictive cantilever beam 121, thus achieving magnetic field adjustability of the capacitor and consequently, adjusting the resonant frequency or signal amplitude of the series or parallel system of the magnetic field-adjustable capacitor array 120 and the acoustic resonator 110.

[0039] In one embodiment, one end of the magnetostrictive cantilever beam 121 can be supported, while the other end is suspended. However, it is understood that the structure of the magnetostrictive cantilever beam 121 in this application is not limited to this. In another embodiment, both ends of the magnetostrictive cantilever beam 121 can be supported, with the middle suspended. Any structure that can cause the magnetostrictive cantilever beam 121 to bend relative to the bottom electrode 122 under the action of an external magnetic field is within the protection scope of this application.

[0040] The magnetic field adjustable capacitor array 120 described above is connected in series with the acoustic resonator 110 to form the magnetic field sensor 100 of this application. The acoustic resonator 110 of this application can be equivalently represented by the modified Butterworth-Van Dyke (MBVD) model. Figure 3 This application discloses an MBVD circuit model diagram of a magnetic field sensor 100 based on a series structure of a magnetic field adjustable capacitor array 120 and an acoustic resonator 110, according to one embodiment of this application. Figure 3As shown, the acoustic resonator 110 includes a series resistor Rs and a parallel network connected to the series resistor Rs. The parallel network contains two branches: one is a static parasitic branch consisting of a parallel loss resistor Ro and a static parallel capacitor Co connected in series; the other is a dynamic mechanical vibration branch consisting of an equivalent dynamic resistance Rm, an equivalent dynamic inductance Lm, and an equivalent dynamic capacitance Cm connected in series. These two branches are connected in parallel and together constitute the core equivalent circuit of the acoustic resonator 110.

[0041] Connecting n adjustable magnetic field capacitors in parallel forms an adjustable magnetic field capacitor array 120. The overall capacitance is determined by... Become .

[0042] According to the MBVD model, when the series-connected adjustable capacitor array 120 is not connected in series, the Rm, Lm, and Cm branches of the acoustic resonator 110 resonate, resulting in minimum impedance. The series resonant frequency of the acoustic resonator 110 is... After connecting the acoustic resonator 110 in series with the magnetic field adjustable capacitor array 120, the branch capacitor is... Roughly become The series resonant frequency of the entire system becomes When the magnetic field changes, the capacitance of the adjustable magnetic field capacitor array 120 changes, causing the system's resonant frequency to change. The magnitude of the applied magnetic field can be determined by detecting the change in the resonant frequency of the magnetic field sensor 100, thereby enabling the sensing of weak DC or low-frequency AC magnetic fields.

[0043] The series connection structure of the acoustic resonator 110 and the magnetic field adjustable capacitor array 120 decouples the magnetic material from the acoustic resonator. This avoids the contradiction caused by the size of the magnetic film area in passive sensors based on acoustic resonance, and also avoids the adverse effects of the introduction of the magnetic film on the resonant frequency and quality factor of the device in active sensors based on acoustic resonance. This improves the sensitivity of the sensor system to the magnetic field, reduces noise, and lowers the detection limit.

[0044] like Figure 2 As shown, the capacitor formed by the magnetostrictive cantilever beam 121 and the bottom electrode 122 can be approximated as a parallel-plate capacitor, with a capacitance of... ,in, Indicates the dielectric constant of the medium. The area of ​​the two plates facing each other is the area of ​​the magnetostrictive cantilever beam 121 and the bottom electrode 122 in the magnetic field adjustable capacitor Cs of this application. The distance between the two plates, in the context of the adjustable magnetic field capacitor Cs in this application, refers to the distance between the magnetostrictive cantilever beam 121 and the bottom electrode 122. Because the magnetostrictive cantilever beam 121 bends differently under different magnetic fields, the distance between the magnetostrictive cantilever beam 121 and the bottom electrode 122 varies accordingly. This results in the adjustable magnetic field capacitor Cs having different capacitance values, and consequently, the entire adjustable magnetic field capacitor array 120 having different capacitance values.

[0045] In some embodiments, the magnetic field sensor 100 includes a plurality of adjustable magnetic field capacitors Cs of the same frequency connected in parallel. The parallel connection of these adjustable magnetic field capacitors Cs can improve the sensitivity of the magnetic field sensor 100. The magnetic field sensor 100 of this application forms an adjustable magnetic field capacitor array 120 by connecting a plurality of (e.g., n) adjustable magnetic field capacitors in parallel. Under the same magnetic field change, the change in the overall capacitance is n times greater than the original value, thus significantly improving the overall sensor system's sensitivity to magnetic fields. It is understood that theoretically, the larger the number of adjustable magnetic field capacitors n, the higher the sensitivity of the magnetic field sensor 100. However, in practice, factors such as sensor area and the range of the magnetic field to be measured must be considered comprehensively; therefore, the number of adjustable magnetic field capacitors n cannot be increased indefinitely.

[0046] In other embodiments, the magnetic field sensor 100 includes a parallel connection of multiple adjustable magnetic field capacitors Cs with different frequencies. The parallel connection of the adjustable magnetic field capacitors Cs with different frequencies can be used to adjust the frequency bandwidth of the sensing magnetic field of the system.

[0047] In some other embodiments, the magnetic field sensor 100 includes a parallel connection of multiple magnetic field adjustable capacitors Cs with the same frequency and multiple different frequencies, which can adapt to the magnetic field sensing response requirements in different scenarios.

[0048] In some embodiments, the magnetostrictive cantilever beam 121 can be a bulk magnetostrictive metal or alloy material. In other embodiments, the magnetostrictive cantilever beam 121 can be a composite material formed by bonding a bulk magnetostrictive metal or alloy material to a substrate. In still other embodiments, the magnetostrictive cantilever beam 121 can be a deposited or bonded magnetostrictive thin film material. In yet another embodiment, the magnetostrictive cantilever beam 121 can be a composite material formed by depositing or bonding a magnetostrictive thin film material on a substrate.

[0049] In some embodiments, the magnetostrictive material in the magnetostrictive cantilever beam 121 may be selected from one or more of the following magnetostrictive metals and alloys: Metallic Glass, FeGaB (FeGaB), FeGaC (FeGaC), FeCoSiB (FeCoSiB), Terfenol-D (Tb-Dy-Fe, a terbium-dysprosium-iron ternary alloy), Ni, Fe, FeGa (FeGa), CoFe (CoFe), CoFeO (CoFeO), CoFeB (CoFeB), NiFe (NiFe), FeAl (FeAl), YIG (Yttrium Iron Garnet). The substrate material in the magnetostrictive cantilever beam 121 may include single-crystal and polycrystalline silicon, silicon oxide, silicon carbide, silicon nitride, diamond, or sapphire.

[0050] The acoustic resonator 110 of this application can achieve electro-acoustic-electric signal conversion through electrodes and piezoelectric materials, and has the advantages of small size, low power consumption, high resonant frequency, and high quality factor. In some embodiments, the acoustic resonator 110 of this application may include, but is not limited to, a surface acoustic wave resonator, a bulk acoustic wave resonator, or a Lamb wave resonator. The surface acoustic wave resonator includes a piezoelectric material substrate, interdigitated electrode pairs, and a reflective grid; the bulk acoustic wave resonator includes a substrate, upper and lower electrodes, and a piezoelectric layer. The Lamb wave resonator includes a substrate, a piezoelectric thin film, interdigitated electrode pairs, and a reflective grid. In the magnetic field sensor 100, the material used to form the substrate may include, but is not limited to, Si (silicon), SiO (silicon oxide), SiC (silicon carbide), SiN (silicon nitride), diamond, or sapphire.

[0051] In one embodiment, the piezoelectric layer in the acoustic resonator 110 can be a bulk piezoelectric material. Bulk piezoelectric materials may include, but are not limited to, PZT (lead zirconate titanate), PMN-PT (lead magnesium niobate-lead titanate), LiNbO3 (lithium niobate) with different tangential orientations, LiTaO3 (lithium tantalate), Quartz, etc.

[0052] In another embodiment, the piezoelectric layer in the acoustic resonator 110 can be a piezoelectric thin film material, which is bonded or grown on a substrate to form a composite structure substrate. The materials for the piezoelectric thin film may include, but are not limited to, AlN (aluminum nitride), ZnO (zinc oxide), GaN (gallium nitride), PZT (lead zirconate titanate), LiNbO3 (lithium niobate) with different orientations, and LiTaO3 (lithium tantalate). The materials for the composite structure substrate may include, but are not limited to, Si (silicon), SiO (silicon oxide), SiC (silicon carbide), SiN (silicon nitride), diamond, and sapphire.

[0053] Figure 4A schematic diagram of the structure of a cavity-type thin-film bulk acoustic resonator 410 according to an embodiment of this application is shown. Figure 4 As shown, the cavity-type thin-film bulk acoustic resonator 410 includes a substrate 411, an upper electrode 415, a lower electrode 413, and a piezoelectric layer 414 located between the upper electrode 415 and the lower electrode 413, wherein a cavity 412 is formed between the substrate 411 and the lower electrode 413.

[0054] In some embodiments, the materials of the bottom electrode 122 in the magnetic field adjustable capacitor Cs and the electrodes in the acoustic resonator 110 may include, but are not limited to, Ti (titanium), Al (aluminum), Cu (copper), Pt (platinum), Mo (molybdenum), Au (gold), Ag (silver), etc.

[0055] The above description uses the example of a series connection between a magnetic field adjustable capacitor array 120 and an acoustic resonator 110 to illustrate the magnetic field sensor 100 of this application. However, the structure of the magnetic field sensor 100 of this application is not limited to this. Figure 5 As shown, in some other embodiments, the magnetic field sensor 100 of this application may also adopt a structure in which the magnetic field adjustable capacitor array 120 and the acoustic resonator 110 are connected in parallel, which has the same characteristics as... Figure 1 Similar beneficial technical effects, others Figure 1 Similar features will not be elaborated here.

[0056] Existing passive magnetic field sensors based on acoustic resonance suffer from a contradiction arising from the size of the magnetic thin film: an excessively small area reduces the maximum deformation of the film, weakens the magnetic focusing effect, and is detrimental to magnetic field sensing; while an excessively large area lowers the overall resonant frequency of the magnetoelectric heterojunction, reduces the maximum frequency shift, and decreases sensitivity. To address these issues, the magnetic field sensor 100 of this application separates the magnetostrictive material from the piezoelectric material by connecting the acoustic resonator 110 and the magnetic field adjustable capacitor array 120 in series or parallel. This ensures that changing the area of ​​the magnetic material does not affect the magnetic field sensing performance, thus avoiding the aforementioned contradiction.

[0057] Existing active magnetic field sensors based on acoustic resonance combine magnetostrictive thin film materials with acoustic resonators. However, magnetostrictive thin film materials suffer from drawbacks such as low intrinsic resonant frequency and high loss, which reduces the sensor's resonant frequency and quality factor, while also increasing noise and raising the detection limit, thus hindering magnetic field detection. To address these issues, the magnetic field sensor 100 of this application decouples the magnetic material from the resonator by connecting the acoustic resonator 110 in series or parallel with the magnetic field adjustable capacitor array 120. This avoids the adverse effects of introducing the magnetic thin film on the device's resonant frequency and quality factor, as well as the noise it introduces, thereby improving the sensor system's sensitivity to magnetic fields and lowering the detection limit.

[0058] The sensitivity of existing magnetic field sensors is usually limited by the device structure or fabrication process, making it difficult to improve. The magnetic field sensor 100 of this application improves the sensitivity of the magnetic field sensor 100 by connecting multiple magnetic field adjustable capacitors Cs in parallel to form an array, and the sensitivity of the magnetic field sensor 100 can be improved relatively easily by increasing the number of parallel magnetic field adjustable capacitors Cs.

[0059] This application also provides an electronic device. The electronic device includes the magnetic field sensor 100 as described above.

[0060] The electronic device described in this application can be implemented as, but is not limited to, mobile terminals such as mobile phones, laptops, digital radio receivers, PDAs (personal digital assistants), PADs (tablet computers), PMPs (portable multimedia players), and in-vehicle terminals (e.g., in-vehicle navigation terminals), as well as fixed terminals such as digital TVs and desktop computers. The above-described electronic device is merely an example and should not impose any limitations on the function or scope of use of the electronic device described in this application.

[0061] This application also provides a method for fabricating a magnetic field sensor. The fabrication process of a magnetic field sensor 100 based on a series or parallel structure of a magnetic field adjustable capacitor array 120 and a cavity-type thin-film bulk acoustic resonator 410 will be used as an example below.

[0062] Figure 6 A flowchart illustrating a method for fabricating a magnetic field sensor according to an embodiment of this application is provided. Figure 6 As shown, a method for preparing a magnetic field sensor according to one embodiment of this application may include steps S61 to S63.

[0063] In step S61, an acoustic resonator 110 is fabricated. The acoustic resonator 110 can be, for example, a type of... Figure 4 The cavity-type thin-film bulk acoustic resonator 410 is shown.

[0064] In some embodiments, step S61, which involves preparing the acoustic resonator 110, may further include steps S611 to S614. (Refer to reference) Figure 4 As shown, in step S611, a recess is etched on the substrate 411; in step S612, a sacrificial layer is filled in the recess; in step S613, a lower electrode 413, a piezoelectric layer 414 and an upper electrode 415 are sequentially grown on the sacrificial layer; in step S614, the sacrificial layer is etched away to form a cavity 412.

[0065] In step S62, a magnetic field adjustable capacitor array 120 is prepared.

[0066] In some embodiments, step S62, the preparation of the magnetic field-tunable capacitor array 120, may further include steps S621 to S623. In step S621, a bottom electrode 122 is grown on a printed circuit board; in step S622, magnetostrictive material is cut to obtain a plurality of magnetostrictive cantilever arms 121; in step S623, the plurality of magnetostrictive cantilever arms 121 are mounted and fixed to the printed circuit board at intervals, with the positions of the plurality of magnetostrictive cantilever arms 121 and the bottom electrode 122 opposite to each other, and an air layer 123 is sandwiched between the magnetostrictive cantilever arms 121 and the bottom electrode 122. Under an applied magnetic field, the magnetostrictive cantilever arms 121 bend, the distance between the magnetostrictive cantilever arms 121 and the bottom electrode 122 changes, and the capacitance of the magnetic field-tunable capacitor array 120 changes.

[0067] In step S63, the acoustic resonator 110 is connected in series or in parallel with the magnetic field adjustable capacitor array 120 to form a magnetic field sensor 100.

[0068] Figure 7 A flowchart illustrating a method for fabricating a magnetic field sensor according to another embodiment of this application is provided. Figure 7 As shown, the method for preparing a magnetic field sensor according to another embodiment of this application may include steps S71 to S73.

[0069] In step S71, an acoustic resonator 110 is fabricated. The acoustic resonator 110 can be, for example, a type of... Figure 4 The cavity-type thin-film bulk acoustic resonator 410 is shown.

[0070] In some embodiments, step S71, which involves preparing the acoustic resonator 110, may further include steps S711 to S714. (Refer to reference) Figure 4 As shown, in step S711, a recess is etched on substrate 411 (referred to as the first substrate); in step S712, a sacrificial layer is filled in the recess; in step S713, a lower electrode 413, a piezoelectric layer 414 and an upper electrode 415 are sequentially grown on the sacrificial layer; in step S714, the sacrificial layer is etched away to form a cavity 412.

[0071] In step S72, a magnetic field adjustable capacitor array 120 is prepared.

[0072] In some embodiments, step S72, the fabrication of the magnetic field-tunable capacitor array 120, may further include steps S721 to S724. In step S721, a bottom electrode 122 is grown on a second substrate; in step S722, a sacrificial layer is formed on the bottom electrode 122; in step S723, a magnetostrictive material or a composite magnetostrictive material is formed at intervals on the sacrificial layer; in step S724, the sacrificial layer is etched away to form a plurality of magnetostrictive cantilever beams 121, the plurality of magnetostrictive cantilever beams 121 being positioned opposite to the bottom electrode 122, and an air layer 123 sandwiched between the magnetostrictive cantilever beams 121 and the bottom electrode 122. Under an applied magnetic field, the magnetostrictive cantilever beams 121 bend, the distance between the magnetostrictive cantilever beams 121 and the bottom electrode 122 changes, and the capacitance of the magnetic field-tunable capacitor array 120 changes. In step S73, the acoustic resonator 110 is connected in series or in parallel with the magnetic field adjustable capacitor array 120 to form a magnetic field sensor 100.

[0073] In one embodiment, the first substrate and the second substrate can be two different substrates, i.e., the acoustic resonator 110 and the magnetic field adjustable capacitor array 120 are formed on two different substrates respectively. Alternatively, in another embodiment, the first substrate and the second substrate can also be two different regions of the same substrate, i.e., the acoustic resonator 110 and the magnetic field adjustable capacitor array 120 can be formed on the same substrate.

[0074] Figure 8 This application discloses the variation of the resonant frequency fs of a magnetic field sensor 100 according to one embodiment of the present application with the adjustable magnetic field capacitance Cs. For example... Figure 8 As shown, n represents the number of adjustable magnetic field capacitors Cs in the adjustable magnetic field capacitor array 120. Under the premise of ensuring a large quality factor, the sensitivity of the resonant frequency to the capacitor is directly proportional to the number n of the parallel adjustable magnetic field capacitors Cs. This result proves that this application can significantly improve the sensitivity of the magnetic field sensor 100.

[0075] The magnetic field sensor 100 and its fabrication method and electronic device of this application adopt a series or parallel structure of a magnetic field adjustable capacitor array 120 and an acoustic resonator 110. The magnetic field adjustable capacitor array 120 includes multiple magnetic field adjustable capacitors connected in parallel, which are composed of a top magnetostrictive cantilever arm 121 and a bottom electrode 122. It can measure DC or low-frequency AC magnetic fields by detecting the resonant frequency shift or reflection parameter amplitude change of the overall sensor system under an applied magnetic field; and measure the AC magnetic field at the system's resonant frequency by detecting the signal amplitude of the sensor system under an applied AC magnetic field.

[0076] The magnetic field sensor 100 and its fabrication method, as well as the electronic device of this application, can significantly improve the sensitivity of the magnetic field sensor system by connecting multiple magnetic field adjustable capacitors in parallel.

[0077] The magnetic field sensor 100 and its fabrication method, along with the electronic device described in this application, decouple the resonator from the magnetostrictive material, inheriting the resonator's high resonant frequency and quality factor. This suppresses sensor noise, reduces the sensor's detection limit, and solves the problems of low sensitivity, low quality factor, and high detection limit in existing acoustic resonant magnetic field sensors. This application can meet the detection needs of DC or low-frequency weak magnetic field signals in fields such as aerospace exploration, marine monitoring, geomagnetic exploration, and biomedicine.

[0078] The magnetic field sensor, its preparation method, and electronic device provided in the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the magnetic field sensor, its preparation method, and electronic device in the embodiments of this application. The descriptions of the embodiments above are only for helping to understand the core ideas of this application and are not intended to limit this application. It should be noted that those skilled in the art can make several improvements and modifications to this application without departing from the spirit and principles of this application, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A magnetic field sensor, characterized in that, The system includes an acoustic resonator and a magnetic field adjustable capacitor array. The magnetic field adjustable capacitor array is connected in series or parallel with the acoustic resonator. The magnetic field adjustable capacitor array includes multiple magnetic field adjustable capacitors connected in parallel. Each magnetic field adjustable capacitor includes a bottom electrode and a magnetostrictive cantilever beam. An air layer is sandwiched between the magnetostrictive cantilever beam and the bottom electrode. Under an applied magnetic field, the magnetostrictive cantilever beam bends, and the distance between the magnetostrictive cantilever beam and the bottom electrode changes. This changes the capacitance of the magnetic field adjustable capacitor array, causing a change in the resonant frequency or signal amplitude of the system where the magnetic field adjustable capacitor array and the acoustic resonator are connected in series or parallel.

2. The magnetic field sensor as described in claim 1, characterized in that, The magnetostrictive cantilever beam is supported at one end and suspended at the other end; or, the magnetostrictive cantilever beam is supported at both ends and suspended in the middle.

3. The magnetic field sensor as described in claim 1, characterized in that, The magnetostrictive cantilever beam is constructed of a bulk magnetostrictive metal or alloy material; or, the magnetostrictive cantilever beam is constructed of a composite material formed by bonding a bulk magnetostrictive metal or alloy material to a substrate; or, the magnetostrictive cantilever beam is constructed of a deposited or bonded magnetostrictive thin film material; or, the magnetostrictive cantilever beam is constructed of a composite material formed by depositing or bonding a magnetostrictive thin film material on a substrate.

4. The magnetic field sensor as described in claim 3, characterized in that, The magnetostrictive material in the magnetostrictive cantilever beam includes one or more of the following magnetostrictive metals and alloys: metallic glass, iron gallium boron, iron gallium carbon, iron cobalt silicon boron, terbium-dysprosium-iron ternary alloy, nickel, iron, iron gallium, cobalt iron, cobalt iron oxygen, cobalt iron boron, nickel iron, iron aluminum, and yttrium iron garnet. The substrate material in the magnetostrictive cantilever beam includes single crystal and polycrystalline silicon, silicon oxide, silicon carbide, silicon nitride, diamond, or sapphire.

5. The magnetic field sensor as described in claim 1, characterized in that, The acoustic resonator includes a surface acoustic wave resonator, a bulk acoustic wave resonator, or a Lamb wave resonator.

6. The magnetic field sensor as described in claim 1, characterized in that, The piezoelectric layer in the acoustic resonator is a bulk piezoelectric material, or the piezoelectric layer is a piezoelectric thin film material, which is bonded or grown on a substrate to form a composite structure substrate.

7. The magnetic field sensor as described in claim 6, characterized in that, The bulk piezoelectric material includes lead zirconate titanate, lead magnesium niobate-lead titanate, lithium niobate with different tangential orientations, lithium tantalate, or quartz.

8. The magnetic field sensor as described in claim 6, characterized in that, The materials of the piezoelectric thin film include aluminum nitride, zinc oxide, gallium nitride, lead zirconate titanate, lithium niobate or lithium tantalate with different tangential orientations; the materials of the composite structure substrate include silicon, silicon oxide, silicon carbide, silicon nitride, diamond or sapphire.

9. The magnetic field sensor as described in claim 1, characterized in that, The materials of the bottom electrode in the magnetic field adjustable capacitor and the electrodes in the acoustic resonator include titanium, aluminum, copper, platinum, molybdenum, gold, or silver.

10. The magnetic field sensor as described in claim 1, characterized in that, The magnetic field sensor comprises multiple adjustable magnetic field capacitors of the same frequency connected in parallel. The sensitivity of the magnetic field sensor is improved by connecting these capacitors in parallel; or... The magnetic field sensor comprises multiple adjustable capacitors of different frequencies connected in parallel. The frequency bandwidth of the sensing magnetic field is adjusted by connecting these capacitors in parallel. The magnetic field sensor includes multiple adjustable magnetic field capacitors of the same frequency and multiple adjustable magnetic field capacitors of different frequencies connected in parallel. The parallel connection of multiple adjustable magnetic field capacitors of the same frequency and multiple adjustable magnetic field capacitors of different frequencies is used to adapt to the magnetic field sensing response requirements in different scenarios.

11. An electronic device, characterized in that, Including the magnetic field sensor as described in any one of claims 1 to 10.

12. A method for preparing a magnetic field sensor, characterized in that, include: Fabricating an acoustic resonator includes: etching a recess on a substrate; filling the recess with a sacrificial layer; sequentially growing a lower electrode, a piezoelectric layer, and a top electrode on the sacrificial layer; and etching away the sacrificial layer to form a cavity. Fabricating a magnetic field-tunable capacitor array includes: growing a bottom electrode on a printed circuit board; cutting a magnetostrictive material to obtain multiple magnetostrictive cantilever beams; mounting and fixing the multiple magnetostrictive cantilever beams at intervals on the printed circuit board, wherein the multiple magnetostrictive cantilever beams are positioned opposite to the bottom electrode, and an air layer is sandwiched between the magnetostrictive cantilever beams and the bottom electrode; wherein, under an applied magnetic field, the magnetostrictive cantilever beams bend, the distance between the magnetostrictive cantilever beams and the bottom electrode changes, and the capacitance of the magnetic field-tunable capacitor array changes. The acoustic resonator is connected in series or in parallel with the magnetic field adjustable capacitor array to form a magnetic field sensor.

13. A method for preparing a magnetic field sensor, characterized in that, include: Fabricating an acoustic resonator includes: etching a recess on a first substrate; filling the recess with a sacrificial layer; sequentially growing a lower electrode, a piezoelectric layer, and an upper electrode on the sacrificial layer; and etching away the sacrificial layer to form a cavity. Fabricating a magnetic field-tunable capacitor array includes: growing a bottom electrode on a second substrate; forming a sacrificial layer on the bottom electrode; forming a magnetostrictive material or a composite magnetostrictive material at intervals on the sacrificial layer; etching away the sacrificial layer to form a plurality of magnetostrictive cantilever beams, wherein the plurality of magnetostrictive cantilever beams are positioned opposite to the bottom electrode, wherein, under an applied magnetic field, the magnetostrictive cantilever beams bend, the distance between the magnetostrictive cantilever beams and the bottom electrode changes, and the capacitance of the magnetic field-tunable capacitor array changes; The acoustic resonator is connected in series or in parallel with the magnetic field adjustable capacitor array to form a magnetic field sensor.

14. The preparation method according to claim 13, characterized in that, The first substrate and the second substrate are two different substrates; or, the first substrate and the second substrate are two different regions of the same substrate.

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