Resonant MEMS electric field sensor based on Lamb wave A0 mode

Abstract

The invention relates to the technical field of micro electro mechanical systems and the technical field of electric field detection, in particular to a resonant MEMS electric field sensor based on a Lamb wave A0 mode, which comprises a substrate, an electric field sensitive resonator main body, an input metal transmission line, an output metal transmission line, an input metal electrode disc and an output metal electrode disc, the main body of the electric field sensitive resonator is suspended on the substrate, and the pair of long-strip-shaped anchor points are connected with the substrate, so that the mechanical constraint of the substrate on the free vibration of the electric field sensitive resonator is reduced, and the leakage of acoustic energy is reduced. In an electric field sensitive resonator body, performance is improved through a multiple structural design. The ratio of the area of the interdigital electrode to the area of the piezoelectric film is controlled to be 25%, and the interdigital electrode is arranged at a central strain concentration position and is matched with the piezoelectric film with a periodic groove structure and a piston electrode structure with a widened tail end, so that an A0 mode can be effectively excited, and the contact area of the piezoelectric film and a to-be-measured electric field is increased. According to the invention, the electric field sensitivity and the anti-interference capability are improved.

Description

Technical Field

[0001] The present invention relates to the technical fields of Micro-Electro-Mechanical Systems (MEMS) and electric field detection, and particularly to a resonant MEMS electric field sensor based on the Lamb wave A0 mode. Background Art

[0002] With the rapid development of the Internet of Things (IoT), smart grid, and Industry 4.0, the demand for high-precision electric field sensors is increasing day by day. Such sensors play a crucial role in power system detection (such as partial discharge detection), aerospace, industrial safety, biomedicine, electric field imaging, and environmental electromagnetic field assessment. Electrostatic discharge and lightning effects are one of the main causes of major safety accidents such as fires in oil and gas storage and transportation and the failure of military electronic equipment. Traditional electric field measurement devices generally use exposed movable mechanical structures, which are easily subject to mechanical collisions and generate triboelectricity, leading to discharge risks and severely restricting their reliability in dangerous working conditions such as dust-rich or oil and gas environments.

[0003] With the development of MEMS micro-nano processing technology, resonant MEMS sensors based on piezoelectric materials have received extensive attention due to their advantages such as low power consumption, small size, no exposed movable structure, and easy integration. MEMS microfabrication technology is a cross-scale manufacturing method based on semiconductor manufacturing processes, which can precisely construct functional structures from micrometers to nanometers and achieve heterogeneous integration, thereby manufacturing integrated and miniaturized sensor devices.

[0004] According to different working principles, MEMS electric field sensors are mainly divided into three types: charge type, capacitive type, and resonant type. Among them, the charge type MEMS electric field sensor outputs an induced current by periodically shielding or exposing the sensing electrode and using the flow of induced charges, but its sensitivity is low and it is easily interfered by environmental temperature and parasitic capacitance. The capacitive MEMS electric field sensor uses an external electric field to cause deformation of the capacitive structure and indirectly measures the electric field strength by measuring the capacitance value, but its structure is complex and requires an additional DC drive signal, increasing the power consumption. In contrast, the resonant MEMS electric field sensor is based on the frequency modulation effect of the resonator. When an external electric field is applied to the surface of the piezoelectric material, due to the inverse piezoelectric effect, strain will be generated in the piezoelectric thin film, changing the effective stiffness of the material and causing the natural frequency to shift. By detecting the frequency change, the resonant MEMS sensor can convert the external electric field signal into an electrical signal that is easy to detect, and has advantages such as no need for DC bias, strong anti-noise ability, and simple structure. However, limited by materials and structures, its sensitivity and the measurement accuracy of the DC electric field in the spatial longitudinal direction still need to be improved. Summary of the Invention

[0005] The object of the present invention is to propose a piezoelectric resonant electric field sensor based on the A0 mode of Lamb wave, aiming at the problems of complex structure, weak anti-noise ability and low sensitivity in the existing electric field sensors. The sensor adopts a Thin-film Piezoelectric-on-Silicon (TPoS) structure, and utilizes the high strain sensitivity characteristic of the asymmetric fundamental mode (A0 mode) of Lamb wave in the thickness direction of the resonator. By designing the shape of the anchor points and the electrode coverage of the resonant unit, accurate measurement of the DC electric field in the spatial longitudinal (Z-axis) direction is realized.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A piezoelectric resonant electric field sensor based on the A0 mode of Lamb wave, comprising a substrate, an electric field-sensitive resonator body, an input metal transmission line, an output metal transmission line, an input metal electrode disk and an output metal electrode disk;

[0008] The substrate is composed of two closely attached single-crystalline silicon layers, and a second isolation oxide layer with full coverage is embedded between the two single-crystalline silicon layers to form a sandwich-like laminated structure. A through hole penetrating the upper and lower single-crystalline silicon layers and the middle second isolation oxide layer is provided in this structure to form a hollow area;

[0009] The electric field-sensitive resonator body is located in the hollow area and is suspended. Its two ends are connected to the substrate through an anchor point respectively; the electric field-sensitive resonator body is composed of an input interdigital electrode, an output interdigital electrode, a piezoelectric thin film and a heavily doped single-crystalline silicon layer arranged from top to bottom in sequence;

[0010] One end of the input metal transmission line is connected to the input interdigital electrode, and the other end is connected to the input metal electrode disk; one end of the output metal transmission line is connected to the output interdigital electrode, and the other end is connected to the output metal electrode disk;

[0011] The input metal electrode disk and the output metal electrode disk are both arranged on the upper surface of the substrate. A grounding metal disk is provided on each side of the input metal electrode disk, and a grounding metal disk is also provided on each side of the output metal electrode disk.

[0012] Furthermore, both the input metal transmission line and the output metal transmission line are composed of a transmission section and a transition section; the transmission section is located on the upper surface of the substrate layer, one end of which is connected to one end of the transition section, and the other end is connected to the metal electrode disk; the transition section is located on the upper surface of the piezoelectric thin film, and the other end of the transition section is connected to the interdigital electrode.

[0013] Furthermore, a first isolation oxide layer electrically isolated from the substrate is provided under all the metal electrode disks and the transmission sections of the metal transmission lines.

[0014] Furthermore, the materials of the first isolation oxide layer and the second isolation oxide layer are both silicon dioxide, and their thicknesses are both 0.3 μm to 1.5 μm.

[0015] Further, the input interdigital electrode and the output interdigital electrode both adopt the same polygonal metal sheet, are arranged on the piezoelectric thin film in a symmetric and alternating manner, and the overall size is smaller than that of the piezoelectric thin film. The width of the electrode strip is widened at the ends of the input interdigital electrode and the output interdigital electrode to form a piston structure.

[0016] Further, the input interdigital electrode and the output interdigital electrode are located at the central strain concentration position of the piezoelectric thin film, and can more effectively excite the A0 mode of the electric field sensitive resonator.

[0017] Further, the piezoelectric thin film under the gap between the input interdigital electrode and the output interdigital electrode is selectively etched, so that a periodic groove structure is formed on the surface of the piezoelectric thin film in contact with the interdigital electrode.

[0018] Further, the total area of the input interdigital electrode and the output interdigital electrode is 25% of the total area of the piezoelectric thin film, which enables a larger contact area between the piezoelectric thin film and the electric field to be measured while ensuring the normal excitation of the A0 mode, and improves the electric field measurement sensitivity.

[0019] Further, the piezoelectric thin film is a rectangular piezoelectric material thin film deposited by a vacuum sputtering coating method. Further, the materials of the metal transmission line, the metal electrode pad, and the interdigital electrode are metals such as gold, silver, copper, aluminum, nickel, or platinum, and the thickness is 0.2 μm to 2 μm; the materials selected for the piezoelectric thin film include but are not limited to LiNbO3, PZT, AlN, ZnO, PVDF, LiTaO3, and other piezoelectric materials, and the thickness is 0.1 μm to 1 μm.

[0020] Further, the anchor points are strip-shaped structures at the connection between the resonator main body and the substrate, and the electric field sensitive resonator main body is fixed to the hollowed area of the substrate through these anchor points.

[0021] After adopting the above technical solution, the present invention has the following beneficial effects:

[0022] 1. The piezoelectric resonant electric field sensor in the present invention realizes the mutual conversion between electrical energy and mechanical energy by exciting the normal operation and signal output of the electric field sensitive resonator through the direct / inverse piezoelectric effect of the piezoelectric thin film material. This device does not require an additional DC voltage drive during operation, nor does it require vacuum packaging, and can operate under normal atmospheric pressure. It has the advantages of direct frequency output and low power consumption. At the same time, it does not require the processing of complex movable mechanical structures, so it is convenient for large-scale batch processing and manufacturing, and the manufacturing cost is relatively low.

[0023] 2. The present invention hollows out the silicon substrate and performs coordinated optimization with the A0 mode, that is, the electric field sensitive resonator body is suspended above the substrate and is connected to the substrate only through a pair of long strip anchor points, which greatly reduces the mechanical constraint of the substrate on the free vibration of the electric field sensitive resonator. At the same time, the significant acoustic impedance difference between the resonator body and the air is used to effectively reduce the leakage of acoustic energy. The A0 mode has the characteristic of thickness-direction strain sensitivity and has a high sensing sensitivity for the vertical electric field (Z axis).

[0024] 3. The present invention controls the ratio of the area of ​​the interdigital electrodes to the area of ​​the piezoelectric film to 25% in the main body of the electric field sensitive resonator, and locates the interdigital electrodes at the central strain concentration position of the piezoelectric film. While achieving effective excitation of the required mode (A0), the contact area between the piezoelectric film and the electric field to be measured is increased, the coupling effect between the electric field to be measured and the resonator is strengthened, and the electric field sensitivity is greatly improved. At the same time, the piezoelectric film under the gap between the input and output interdigital electrodes is etched, so that the piezoelectric film forms a periodic groove structure in the direction perpendicular to the interdigital electrodes, and is no longer a rectangular film of a single thickness. This method makes the electric field intensity at the groove of the piezoelectric film more concentrated, which can greatly improve the electric field sensitivity. In addition, by widening the ends of the input and output interdigital electrodes to form a piston structure, the equivalent load mass of the region is increased and the acoustic wave phase velocity is reduced, which greatly reduces the generation of stray modes. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of a three-dimensional structure of a piezoelectric resonant electric field sensor based on the Lamb wave A0 mode provided in an embodiment;

[0026] Figure 2 A schematic diagram of a three-dimensional decomposition structure of a piezoelectric resonant electric field sensor based on the Lamb wave A0 mode provided in an embodiment;

[0027] Figure 3 A schematic diagram of a top view of a piezoelectric resonant electric field sensor based on the Lamb wave A0 mode provided in an embodiment;

[0028] Figure 4 A schematic diagram of the structure of a piezoelectric resonant electric field sensor based on the Lamb wave A0 mode provided in an embodiment when viewed from above;

[0029] Figure 5 A graph showing the shift of the resonant frequency of the piezoelectric resonant electric field sensor based on the Lamb wave A0 mode as the electric field strength in the vertical direction (Z axis) changes, provided in the embodiment;

[0030] Figure 6 A schematic diagram of a BB' cross section of a piezoelectric resonant electric field sensor based on the Lamb wave A0 mode provided in an embodiment;

[0031] Figure 7 Schematic diagram of the decomposed structure of the input interdigital electrode and the output interdigital electrode of the piezoelectric resonant electric field sensor based on the Lamb wave A0 mode provided for the embodiment;

[0032] Figure 8 Vibration displacement diagram of the A0 mode of the B-B' cross-section of the piezoelectric resonant electric field sensor based on the Lamb wave A0 mode provided for the embodiment (excluding the substrate part);

[0033] Figure 9 Curve graph of the change in electric field sensitivity of the piezoelectric resonant electric field sensor based on the Lamb wave A0 mode provided for the embodiment under different top interdigital electrode coverage rates;

[0034] Figure 10 Vibration strain diagram of the A0 mode of the B-B' cross-section of the piezoelectric resonant electric field sensor based on the Lamb wave A0 mode provided for the embodiment (excluding the substrate part);

[0035] Reference numerals:

[0036] 1. Electric field sensitive resonator body; 2. Input interdigital electrode; 201. Input metal electrode disk; 202. Input metal transmission line; 203. First ground electrode disk; 204. First electrode widening area; 3. Output interdigital electrode; 301. Output metal electrode disk; 302. Output metal transmission line; 303. Second ground electrode disk; 304. Second electrode widening area; 4. Piezoelectric thin film; 5. First isolation oxide layer; 6. Heavily doped single crystal silicon layer; 7. Substrate; 701. Second isolation oxide layer. Detailed implementation manners

[0037] Hereinafter, the term "comprising" or "may comprise" that may be used in various embodiments of the present invention indicates the presence of the invented functions, operations or elements, and does not limit the addition of one or more functions, operations or elements. In addition, as used in various embodiments of the present invention, the terms "comprising", "having" and their cognates are only intended to represent specific features, numbers, steps, operations, elements, components or combinations of the foregoing items, and should not be construed as first excluding the existence of one or more other features, numbers, steps, operations, elements, components or combinations of the foregoing items or the possibility of adding one or more features, numbers, steps, operations, elements, components or combinations of the foregoing items.

[0038] In various embodiments of the present invention, the expression "or" or "at least one of A or / and B" includes any combination or all combinations of the recited words. For example, the expression "A or B" or "at least one of A or / and B" may include A, may include B, or may include both A and B.

[0039] Expressions (such as "first", "second", etc.) used in various embodiments of the present invention may modify various constituent elements in the various embodiments, but do not limit the corresponding constituent elements. For example, the above expressions do not limit the order and / or importance of the elements. The above expressions are only for the purpose of distinguishing one element from other elements. For example, the first user device and the second user device indicate different user devices, although both are user devices. For example, without departing from the scope of the various embodiments of the present invention, the first element may be referred to as the second element, and similarly, the second element may also be referred to as the first element.

[0040] It should be noted that: if it is described that one constituent element is "connected" to another constituent element, the first constituent element may be directly connected to the second constituent element, and a third constituent element may be "connected" between the first constituent element and the second constituent element. Conversely, when one constituent element is "directly connected" to another constituent element, it can be understood that there is no third constituent element between the first constituent element and the second constituent element.

[0041] The terms used in the various embodiments of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the various embodiments of the present invention. As used herein, the singular form is intended to also include the plural form unless the context clearly indicates otherwise. Unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the various embodiments of the present invention pertain. The terms (such as those defined in a commonly used dictionary) will be interpreted as having the same meaning as the contextual meaning in the relevant technical field and will not be interpreted as having an idealized meaning or an overly formal meaning unless clearly defined in the various embodiments of the present invention.

[0042] To make the purpose, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with embodiments and drawings. The illustrative embodiments and descriptions thereof of the present invention are only for explaining the present invention and do not serve as a limitation to the present invention. The technical solutions of the present invention will be described in detail below in conjunction with the drawings.

[0043] Embodiment 1

[0044] For ease of understanding, the following will first explain the professional technical terms that appear in this article:

[0045] Acoustic impedance: It is used to measure the magnitude of the resistance encountered by sound waves when propagating in different media, reflecting the obstructive effect of the medium on sound waves, similar to the obstructive effect of resistance on electric current. When sound waves propagate from one medium to another medium with a large difference in acoustic impedance (such as silicon and air), strong reflection phenomena of sound waves will occur.

[0046] Piston structure: It is a special structural design for interdigital electrodes. The core idea of the design is to change the phase velocity of sound waves in this region by increasing the equivalent mass load in the end region of the electrodes, thereby suppressing the spurious modes excited by the interdigital electrodes in the resonator.

[0047] Spurious mode: The non-ideal vibration mode of the resonator excited by the interdigital electrodes, which will interfere with the frequency response of the resonator and affect the normal operation of the resonator.

[0048] Phase velocity: When a sound wave propagates in a medium, it is the propagation speed of the phase of the wave.

[0049] Direct piezoelectric effect: When a piezoelectric material is subjected to an external force in a certain direction, due to the asymmetry of the crystal structure of the piezoelectric material, it will be polarized, and charges with opposite polarities will be generated on the surface of the piezoelectric material.

[0050] Inverse piezoelectric effect: When an alternating electric field is applied to the surface of a piezoelectric material, the phenomenon that the material undergoes mechanical deformation, and the magnitude of the deformation is closely related to the applied electric field strength.

[0051] As Figures 1-4 shown, the piezoelectric resonant electric field sensor based on the Lamb wave A0 mode provided in this embodiment includes a substrate 7 and an electric field-sensitive resonator body 1, an input metal electrode disk 201 and an input metal transmission line 202, an output metal electrode disk 301 and an output metal transmission line 302, a first grounding electrode disk 203 and a second grounding electrode disk 303 integrated on the substrate 7.

[0052] The substrate 7 is composed of two closely attached single-crystalline silicon layers. A second isolation oxide layer 701 is sandwiched between the two single-crystalline silicon layers to form a sandwich-like laminated structure. And a through hole penetrating the upper and lower single-crystalline silicon layers and the middle second isolation oxide layer 701 is provided in this structure to form a hollow area.

[0053] The electric field-sensitive resonator body 1 is located in the hollow area and is suspended. Each of its two ends is connected to the substrate 7 through an anchor point. The electric field-sensitive resonator body 1 is composed of an input interdigital electrode 2, an output interdigital electrode 3, a piezoelectric thin film 4, and a heavily doped single-crystalline silicon layer 6 arranged in sequence from top to bottom.

[0054] One end of the input metal transmission line 202 is connected to the input interdigital electrode 2, and the other end is connected to the input metal electrode disk 201. One end of the output metal transmission line 302 is connected to the output interdigital electrode 3, and the other end is connected to the output metal electrode disk 301. The input metal transmission line 202 and the output metal transmission line 302 are both composed of a transmission section and a transition section, the transmission section is located on the upper surface of the substrate layer, and the transition section is located on the upper surface of the piezoelectric film. One end of the transmission section in the input metal transmission line 202 is connected to one end of the transition section, and the other end is connected to the input electrode disk 201, and the other end of the transition section is connected to the input interdigital electrode 2. One end of the transmission section in the output metal transmission line 302 is connected to one end of the output transmission line transition section, and the other end is connected to the output electrode disk 301, and the other end of the output transmission line transition section is connected to the output interdigital electrode 3.

[0055] The input metal electrode disk 201 and the output metal electrode disk 301 are both disposed on the upper surface of the substrate 7 , and a first grounding electrode disk 203 is disposed on both sides of the input metal electrode disk 201 , and a second grounding electrode disk 303 is also disposed on both sides of the output metal electrode disk.

[0056] A first isolation oxide layer 5 electrically isolated from the substrate 7 is provided below all metal electrode disks and the transmission sections of the metal transmission lines.

[0057] In this embodiment, the piezoelectric film 4 is a rectangular piezoelectric material film deposited by a vacuum sputtering coating method. The anchor point is a long strip structure at the connection between the resonator body and the substrate, which reduces the constraint effect of the substrate on the freely vibrating resonator body. At the same time, the difference in acoustic impedance between the resonator body and the air is used to make the sound wave reflect at the boundary of the resonator, and the sound wave energy is concentrated in the resonator body. The total area of ​​the input fork finger electrode 2 and the output fork finger electrode 3 is 25% of the total area of ​​the piezoelectric film. While ensuring that the A0 mode can be normally excited, there is a larger contact area between the piezoelectric film and the electric field to be measured, which enhances the coupling effect between the electric field to be measured and the resonator body, and improves the electric field measurement sensitivity. At the same time, the entire fork finger electrode is located at the central strain concentration position of the piezoelectric film 4, and the strain concentration position is the position where the strain size in the A0 mode vibration strain diagram is significantly different from the surrounding position, such as Figure 10In the black position shown in the figure, setting the interdigital electrodes at the strain concentration position of the piezoelectric thin film can more effectively excite the electric field sensitive resonator according to the vibration shape of the A0 mode, reducing unnecessary energy loss. And by etching the piezoelectric thin film under the gap between the input interdigital electrodes and the output interdigital electrodes, a periodic groove structure is formed in the piezoelectric thin film along the direction perpendicular to the interdigital electrodes, enhancing the electric field concentration degree in the groove area. A larger strain can be generated in the piezoelectric thin film, improving the electric field sensitivity. First electrode widening area 204 and second electrode widening area 304 are respectively set at the ends of the input and output interdigital electrodes to form a piston structure, increasing the equivalent mass load brought by the electrodes in this area and thus reducing the phase velocity of the Lamb wave in this area. At this time, the acoustic impedance difference at the original electrode ends changes, reducing the generation of spurious modes. It should be noted that there are various ways to obtain the central strain concentration position of the piezoelectric thin film 4. In this embodiment, it is obtained through simulation.

[0058] The resonator adopting the TPoS structure is a two-port acoustic device capable of realizing the mutual conversion between mechanical energy and electrical energy. When a voltage is applied to the input interdigital electrodes 2 to generate excitation, the piezoelectric thin film 4 will be affected by the electric field generated by the input interdigital electrodes 2. At this time, due to the effect of the inverse piezoelectric effect, mechanical strain is generated in the piezoelectric material, and then the entire resonator is driven to vibrate according to a specific vibration mode, realizing the conversion from electrical energy to mechanical energy. Similarly, the output interdigital electrodes 3 located on the piezoelectric thin film 4 will collect the periodic induced charges generated by the piezoelectric thin film 4 due to strain under the action of the direct piezoelectric effect, and finally output through the output metal transmission line 302 and the output metal electrode pad 301.

[0059] As Figure 4 shown, the electric field sensor shown in the present invention is realized by detecting the natural resonance frequency of the electric field sensitive resonator body. When there is no external electric field in space, the natural frequency of the resonator is determined by its geometric dimensions and the material characteristics of the resonator itself. The expression of its natural frequency f0 is:

[0060]

[0061] In the formula, t is the thickness of the resonator, C0 is the total elastic stiffness coefficient of the resonator, ρ0 is the total density of the resonator, and V p is the phase velocity of the acoustic wave propagation. When an electric field in the same direction as the thickness direction (Z-axis) is applied to the resonator, the piezoelectric response to the thickness direction in the piezoelectric material will be excited. The expression of the excited longitudinal strain ε z is:

[0062] ε z = d 33 E z

[0063] where d 33 is the component of the piezoelectric constant matrix of the piezoelectric material in the thickness direction (Z axis), E z is the magnitude of the applied Z-axis electric field strength, and the longitudinal strain ε z The longitudinal prestress σ z , thereby modulating the total elastic stiffness coefficient of the resonator, which ultimately causes the natural resonant frequency of the resonator to shift. The expression of the frequency shift Δf is:

[0064]

[0065] C1=∫σ z ·ε z dV=E z ∫σ z ·d 33 dV

[0066] Where C1 is the elastic stiffness coefficient after being modulated by the longitudinal electric field, and f1 is the natural resonant frequency value after the longitudinal electric field acts. According to the above formula, it can be found that the frequency response of the electric field sensitive resonator shows a linear shift with the applied electric field strength. Therefore, the resonant frequency of the resonator shows a linear change with the applied electric field strength. (See Figure 5 ), the strength of the external electric field can be determined by measuring the change in the resonant frequency of the entire resonator.

[0067] like Figure 8 As shown in the figure, Lamb wave is an elastic guided wave propagating in a free boundary thin plate. Its propagation direction is parallel to the plate surface and its energy is confined to the plate. The A0 mode is one of the basic modes of Lamb wave propagation. Its characteristics are that the displacement is anti-symmetrically distributed along the plate thickness direction, the center plane displacement is zero, and the upper and lower surface displacement amplitudes are the largest. The A0 mode is sensitive to changes in the strain distribution in the thickness direction and can produce a frequency shift response to small disturbances caused by the electric field in the thickness direction.

[0068] like Figure 6 , 7 As shown in Figures 9 and 9, the present invention adopts the optimal ratio of the surface interdigital electrodes to the piezoelectric film area. Compared with the resonator structure in which the interdigital electrodes are arranged on the top of the traditional piezoelectric film, the structure can greatly improve the sensitivity of the resonator to the external electric field, increase the coupling effect between the external electric field and the resonator, and ensure the normal excitation of the A0 mode. The top interdigital electrode coverage η is defined as:

[0069]

[0070] Where S IDT is the top interdigital electrode area, S Piezo is the area of ​​the piezoelectric film.

[0071] Compared with the traditional piezoelectric thin-film resonator structure with uniform thickness, in the present invention, the piezoelectric thin film in the gap region between the input interdigital electrode and the output interdigital electrode is etched to form a periodic groove structure, so that the external electric field is concentrated in the groove region, greatly enhancing the strain generated by the external electric field in the piezoelectric thin film and thus improving the electric field sensitivity.

[0072] Generally speaking, this piezoelectric resonant electric field sensor based on the Lamb wave A0 mode realizes the detection of the external electric field strength without the need to process complex mechanical movable structures, and at the same time has the advantages of not requiring vacuum packaging and having relatively high sensitivity.

[0073] The above embodiments are only illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. A piezoelectric resonant electric field sensor based on the Lamb wave A0 mode, characterized in that It includes a substrate, an electric field-sensitive resonator body, an input metal transmission line, an output metal transmission line, an input metal electrode pad, and an output metal electrode pad; The substrate is composed of two closely adhered single-crystalline silicon layers. A second isolation oxide layer is sandwiched and fully covered between the two single-crystalline silicon layers to form a sandwich-like laminated structure. A through-hole that penetrates the upper and lower single-crystalline silicon layers and the middle second isolation oxide layer is provided in this structure to form a hollow area; The electric field-sensitive resonator body is located in the hollow area and is suspended. Both ends of it are connected to the substrate through an anchor point respectively; The electric field-sensitive resonator body is composed of an input interdigital electrode, an output interdigital electrode, a piezoelectric thin film, and a heavily doped single-crystalline silicon layer arranged in sequence from top to bottom; One end of the input metal transmission line is connected to the input interdigital electrode, and the other end is connected to the input metal electrode pad; One end of the output metal transmission line is connected to the output interdigital electrode, and the other end is connected to the output metal electrode pad; Both the input metal electrode pad and the output metal electrode pad are arranged on the upper surface of the substrate. A grounding metal pad is provided on each side of the input metal electrode pad, and a grounding metal pad is also provided on each side of the output metal electrode pad.

2. The piezoelectric resonant electric field sensor based on the Lamb wave A0 mode according to claim 1, characterized in that, Both the input metal transmission line and the output metal transmission line are composed of a transmission section and a transition section; The transmission section is located on the upper surface of the substrate layer. One end of it is connected to one end of the transition section, and the other end is connected to the metal electrode pad; The transition section is located on the upper surface of the piezoelectric thin film, and the other end of the transition section is connected to the interdigital electrode.

3. A piezoelectric resonant electric field sensor based on the A0 mode of Lamb wave according to claim 1, characterized in that Below all the metal electrode pads and the transmission sections of the metal transmission lines, a first isolation oxide layer that is electrically isolated from the substrate is provided.

4. A piezoelectric resonance electric field sensor based on the Lamb wave A0 mode according to claim 2, characterized in that, The materials of both the first isolation oxide layer and the second isolation oxide layer are silicon dioxide, and their thicknesses are both 0.3μm - 1.5μm.

5. A piezoelectric resonant electric field sensor based on the Lamb wave A0 mode according to claim 1, characterized in that, Both the input interdigital electrode and the output interdigital electrode adopt the same polygonal metal sheet, and are arranged on the piezoelectric thin film in a symmetric and alternating manner with an overall size smaller than that of the piezoelectric thin film.

6. The piezoelectric resonant electric field sensor based on the Lamb wave A0 mode according to claim 1, characterized in that, The input interdigital electrode and the output interdigital electrode are located at the central strain concentration position of the piezoelectric thin film.

7. The piezoelectric resonant electric field sensor based on the Lamb wave A0 mode according to claim 1, characterized in that, The total area of the input interdigital electrode and the output interdigital electrode is 25% of the total area of the piezoelectric thin film.

8. A piezoelectric resonant electric field sensor based on the Lamb wave A0 mode according to any one of claims 1, characterized in that, The anchor point is a strip-like structure at the connection between the resonator body and the substrate.

9. A piezoelectric resonant electric field sensor based on the A0 mode of Lamb wave according to any one of claims 1-8, characterized in that, The materials of the metal transmission line, the metal electrode pad, and the interdigital electrode are gold, silver, copper, aluminum, nickel, or platinum. The thicknesses of the metal transmission line, the metal electrode pad, and the interdigital electrode are all 0.2μm - 2μm; The thickness of the piezoelectric thin film is 0.1μm - 1μm.

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