Non-invasive voltage sensitive element based on piezoelectric mutual shielding differential structure and preparation method

Abstract

The application provides a non-invasive voltage sensitive element based on a piezoelectric mutual shielding differential structure and a preparation method, and belongs to the technical field of semiconductor preparation. By introducing a group of reference electrode groups which are physically identical to the measurement electrode groups, the object of differential detection is changed from fixed electrodes and movable electrodes to measurement electrode groups and reference electrode groups. The measurement electrode groups are used to pick up the to-be-measured electric field signals and environmental common-mode noise, and the reference electrode groups only pick up the environmental common-mode noise. After difference, the pure to-be-measured signal can be obtained. And because the two groups of electrode groups are prepared synchronously in the same MEMS process, the structural parameters are highly consistent, the common-mode noise presents almost the same amplitude and phase in the outputs of the two groups, and is completely suppressed after difference. Through the full-symmetry design of the measurement electrode groups and the reference electrode groups, not only the external common-mode noise such as environmental temperature drift and mechanical vibration is eliminated, but also the piezoelectric drive signal crosstalk is effectively cancelled out, realizing a multi-level common-mode suppression effect.

Description

Technical Field

[0001] This application relates to the field of semiconductor fabrication technology, and in particular to a non-invasive voltage-sensitive element based on a piezoelectric mutually shielded differential structure and its fabrication method. Background Technology

[0002] Voltage measurement technology is widely used in power system monitoring, industrial automation, aerospace, smart grids, new energy power generation, and electrical equipment condition diagnosis. Non-invasive voltage measurement schemes based on MEMS electric field sensors utilize the capacitive coupling effect between the conductor under test and the sensor to indirectly calculate the conductor voltage by measuring the electric field strength at the sensor's location. Their core sensing element typically uses a MEMS electric field sensor based on the charge induction principle, offering advantages such as high driving force, low driving voltage, and low power consumption. However, existing non-invasive voltage measurement schemes have the following drawbacks: First, although the fixed and movable electrodes work together functionally, they differ in physical structure. The movable electrode can move and is connected to a piezoelectric actuator, while the fixed electrode remains stationary and is fixed to the substrate. This difference in roles leads to inherent asymmetries between the fixed and movable electrodes in terms of geometry, boundary conditions, stiffness distribution, and parasitic capacitance. This inherent structural asymmetry means that common-mode noise, such as temperature drift, mechanical vibration, electromagnetic interference, and drive signal crosstalk, does not present completely consistent amplitude and phase in the two signals. Differential subtraction cannot completely eliminate this common-mode noise, and the residual noise affects measurement accuracy. Second, in existing piezoelectric driven electric field sensors, the piezoelectric driving signal is usually an AC signal, and its frequency is the same as that of the induced signal, which can easily cause crosstalk interference to the measured electric field.

[0003] In summary, the technical problems existing in the relevant technologies need to be improved. Summary of the Invention

[0004] The main objective of this application is to propose a non-invasive voltage-sensitive element based on a piezoelectric mutually shielded differential structure and its fabrication method, which aims to completely suppress common-mode noise, cancel piezoelectric drive signal crosstalk, and improve the common-mode rejection ratio and signal-to-noise ratio.

[0005] To achieve the above objectives, this application proposes a non-invasive voltage-sensitive element based on a piezoelectric mutually shielded differential structure, comprising a substrate layer, an insulating isolation layer, a device layer, and a piezoelectric driving layer; The substrate layer, insulating isolation layer, and device layer are sequentially fixedly connected to form a substrate; the piezoelectric driving layer is deposited on top of the substrate. The device layer includes a measurement electrode group and a reference electrode group with identical physical structures. Both the measurement electrode group and the reference electrode group include movable electrodes. Under the action of the driving voltage, the piezoelectric driving layer generates a vibration displacement perpendicular to the chip plane, driving the connected movable electrodes to move. The measuring electrode group picks up the electric field signal to be measured and the ambient common-mode noise, while the reference electrode group only picks up the ambient common-mode noise. The two sets of signals output by the measuring electrode group and the reference electrode group are processed differentially to obtain the electric field signal to be measured.

[0006] Preferably, the piezoelectric driving layer is mounted above the movable electrode and connected to the movable electrode, and the bottom electrode of the piezoelectric driving layer is grounded through a wire.

[0007] Preferably, the piezoelectric driving layer includes a bottom electrode, a piezoelectric material layer, and a top electrode. An insulating layer is deposited on the device layer, and a bottom electrode is deposited on the insulating layer. Electrical isolation between the device layer and the piezoelectric driving layer is achieved through the insulating layer.

[0008] Preferably, both the measuring electrode group and the reference electrode group are configured to be at least one.

[0009] Preferably, the measuring electrode group includes a first movable electrode and a first fixed electrode. The first movable electrode is connected below the piezoelectric driving layer and is driven by the piezoelectric driving layer to generate reciprocating vibration perpendicular to the sensitive chip substrate. The first fixed electrode is fixedly connected to the substrate layer. The reference electrode group includes a second movable electrode and a second fixed electrode. The second movable electrode is connected below the piezoelectric driving layer and is driven by the piezoelectric driving layer to generate reciprocating vibration perpendicular to the sensitive chip substrate. The second movable electrode has the same physical structure as the first movable electrode. The second fixed electrode is fixedly connected to the substrate layer and has the same physical structure as the first fixed electrode.

[0010] Preferably, both the first fixed electrode and the first movable electrode are induction electrodes, and the first fixed electrode and the first movable electrode are mutual shielding electrodes.

[0011] Preferably, both the first movable electrode and the first fixed electrode adopt a comb-tooth structure and are arranged alternately at equal intervals in the horizontal direction to form a comb-tooth-shaped capacitive sensing structure. The measuring electrode group picks up the external electric field sensing signal through the comb-tooth-shaped capacitive sensing structure and outputs the induced charge signal through the output electrode. The output electrode is electrically connected to the external detection circuit.

[0012] Preferably, the two induced charge signals output from the measuring electrode group and the reference electrode group are converted into voltage signals and amplified by a differential amplifier circuit to obtain the measured value of the electric field strength.

[0013] To achieve the above objectives, this application provides an electric field sensor, which includes a non-invasive voltage-sensitive element and a housing outside the non-invasive voltage-sensitive element. An insulating cover is installed on the top of the housing, and through holes are machined on the insulating cover at positions corresponding to the reference electrode group. I-shaped shielding electrodes are inserted into the through holes, and the shielding electrodes are connected to an external ground signal to shield the reference electrode group from sensing external electric fields.

[0014] To achieve the above objectives, this application also proposes a method for fabricating a non-invasive voltage-sensitive element based on a piezoelectric mutually shielded differential structure, the method comprising: SOI substrates were selected as the wafers for fabrication, and an insulating layer was deposited on the surface of the device layer after cleaning. A bottom electrode is deposited on the insulating layer, and the bottom electrode is patterned. A piezoelectric material layer is deposited on the bottom electrode; A top electrode is deposited on the piezoelectric material layer to obtain a deposited wafer. Photoresist is coated on the surface of the wafer after deposition, and the comb structure of the measurement electrode group and the reference electrode group is etched by etching process until the etching depth reaches the insulating isolation layer at the bottom of the device layer. Photoresist is coated on the back of the wafer, and after photolithography patterning, the measurement electrode group and the reference electrode group are obtained.

[0015] This application offers at least the following advantages: It provides a non-invasive voltage-sensitive element and its fabrication method based on a piezoelectric mutually shielded differential structure. By introducing a reference electrode group with the same physical structure as the measurement electrode group, the differential detection object is transformed from fixed and movable electrodes to the measurement electrode group and the reference electrode group. The measurement electrode group picks up the electric field signal to be measured and environmental common-mode noise, while the reference electrode group only picks up environmental common-mode noise. After differential processing, a pure signal to be measured can be obtained. Furthermore, since the two electrode groups are fabricated synchronously in the same MEMS process, their structural parameters are highly consistent, and the common-mode noise exhibits almost the same amplitude and phase in both outputs, which is completely suppressed after differential processing. Through the fully symmetrical design of the measurement electrode group and the reference electrode group, not only are external common-mode noises such as environmental temperature drift and mechanical vibration eliminated, but crosstalk from the piezoelectric drive signal is also effectively canceled, achieving a multi-level common-mode suppression effect. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a non-invasive voltage-sensitive element based on a piezoelectric mutually shielded differential structure provided in the embodiments of this application; Figure 2 This is a schematic diagram of the piezoelectrically shielded induction unit structure according to an embodiment of this application; Figure 3This is a schematic cross-sectional view of the piezoelectrically shielded induction unit according to an embodiment of this application; Figure 4 This is a schematic diagram of piezoelectric mutual shielding differential detection in an embodiment of this application.

[0017] Figure 5 This is a schematic diagram of the fabrication steps of a non-invasive voltage-sensitive element based on a piezoelectric mutually shielded differential structure provided in the embodiments of this application; The following are explanations of the labels in the figure: Substrate layer 1, Insulating layer 2, Device layer 3, Measurement electrode group 4, Reference electrode group 5, First movable electrode 6, First fixed electrode 7, Second movable electrode 8, Second fixed electrode 9, Piezoelectric drive layer 10, Insulating layer 11, Bottom electrode 12, Piezoelectric material layer 13, Top electrode 14, Output electrode 15, Shielding electrode 16, Housing 17, Insulating cover plate 18. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. In the following description, when referring to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements.

[0019] It is understood that the terms “first,” “second,” etc., used in this application may be used herein to describe various concepts, but unless otherwise stated, these concepts are not limited by these terms. These terms are only used to distinguish one concept from another. For example, without departing from the scope of the embodiments of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the words “if,” “when,” or “in response to a determination” as used herein may be interpreted as “when…” or “when…” or “in response to a determination.”

[0020] As used in this application, the terms "at least one", "multiple", "each", "any", etc., "at least one" includes one, two or more, "multiple" includes two or more, "each" refers to each of the corresponding multiples, and "any" refers to any one of the multiples.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit this application.

[0022] Existing non-invasive voltage measurement schemes have the following drawbacks: First, the fixed and movable electrodes differ in physical structure, resulting in inherent asymmetries in geometry, boundary conditions, stiffness distribution, and parasitic capacitance. This structural asymmetry causes common-mode noise, such as temperature drift, mechanical vibration, electromagnetic interference, and drive signal crosstalk, to exhibit inconsistent amplitudes and phases in the two signals. This noise cannot be completely eliminated after differential subtraction, and the residual common-mode noise affects measurement accuracy. Second, in existing piezoelectric driven electric field sensors, the piezoelectric drive signal is typically an AC signal with the same frequency as the induced signal, which easily generates crosstalk interference to the measured electric field.

[0023] In view of this, this application provides a non-invasive voltage-sensitive element based on a piezoelectric mutually shielded differential structure and its fabrication method. By introducing a reference electrode group with the same physical structure as the measuring electrode group, the object of differential detection is changed from fixed and movable electrodes to the measuring electrode group and the reference electrode group. The measuring electrode group is used to pick up the electric field signal to be measured and environmental common-mode noise, while the reference electrode group only picks up environmental common-mode noise. After differential processing, a pure signal to be measured can be obtained. Furthermore, since the two electrode groups are fabricated synchronously in the same MEMS process, their structural parameters are highly consistent, and the common-mode noise exhibits almost the same amplitude and phase in the two outputs, which is completely suppressed after differential processing. Through the fully symmetrical design of the measuring electrode group and the reference electrode group, not only are external common-mode noises such as environmental temperature drift and mechanical vibration eliminated, but crosstalk of the piezoelectric drive signal can also be effectively canceled, achieving a multi-level common-mode suppression effect.

[0024] Please see Figure 1-4 As shown, one aspect of this application provides a non-invasive voltage-sensitive element based on a piezoelectric mutually shielded differential structure, including a substrate layer 1, an insulating isolation layer 2, a device layer 3, and a piezoelectric driving layer 10; Substrate 1, insulating isolation layer 2 and device layer 3 are sequentially fixedly connected to form a substrate; piezoelectric driving layer 10 is deposited on top of the substrate; Device layer 3 includes a measurement electrode group 4 and a reference electrode group 5 with identical physical structures. Both the measurement electrode group 4 and the reference electrode group 5 include movable electrodes. Under the action of the driving voltage, the piezoelectric driving layer 10 generates a vibration displacement perpendicular to the chip plane, driving the connected movable electrodes to move. The measuring electrode group 4 picks up the electric field signal to be measured and the ambient common-mode noise, while the reference electrode group 5 only picks up the ambient common-mode noise. The two sets of signals output by the measuring electrode group 4 and the reference electrode group 5 are processed differentially to obtain the electric field signal to be measured.

[0025] In this embodiment, the measuring electrode group 4 simultaneously picks up the electric field signal under test and the ambient common-mode noise, while the reference electrode group 5 only picks up the ambient common-mode noise. By performing differential processing on the two sets of output signals again, ambient common-mode noise such as power frequency interference, electromagnetic radiation, and temperature drift can be significantly canceled, effectively suppressing the noise floor and significantly improving the signal-to-noise ratio of the output signal. The measuring electrode group 4 and the reference electrode group 5 have identical physical structures, ensuring a high degree of consistency in their noise response. The differential operation can eliminate common-mode errors to the maximum extent, making the extraction of the signal under test more accurate.

[0026] The piezoelectric driving layer 10 drives the movable electrode to generate a vibration displacement perpendicular to the chip plane. That is, the movable electrode is periodically moved by piezoelectric driving, which converts the weak electric field signal into an AC signal with capacitance change. This achieves high sensitivity detection of weak electric field signals and significantly improves the resolution of voltage / electric field measurement.

[0027] In some embodiments, the piezoelectric drive layer 10 is mounted above and connected to the movable electrode, and the bottom electrode of the piezoelectric drive layer 10 is grounded via a wire.

[0028] It should be noted that the movable electrodes here include the first movable electrode 6 and the second movable electrode 8. The movable electrodes are connected to the piezoelectric driving layer 10 through a support beam formed by MEMS technology, such as a silicon beam or a metal beam. When the piezoelectric driving layer 10 vibrates, it drives the movable electrodes to reciprocate through the support beam. Furthermore, the movement amplitude and resonant frequency of the movable electrodes can be adjusted through the structural design of the support beam, such as its length and thickness, while ensuring the mechanical stability of the device.

[0029] The purpose of mechanically connecting the piezoelectric driving layer 10 with the movable electrode is to transmit the vertical vibration displacement generated by the piezoelectric driving layer 10 under the driving voltage to the movable electrode below without loss, so that it moves up and down synchronously. Through the periodic movement of the movable electrode, the electric field signal to be measured is modulated to a high frequency, effectively avoiding low-frequency noise interference.

[0030] The bottom electrode refers to the electrode in the piezoelectric drive layer 10 that is close to the movable electrode. Grounding this bottom electrode forms an electrical shielding layer, which isolates the drive electric field inside the piezoelectric drive layer 10 from the signal pickup area of ​​the movable electrode below, blocking crosstalk from the piezoelectric drive electric field to the movable electrode area. On the other hand, it can provide a stable reference potential for the piezoelectric drive layer 10, ensuring that the drive and signal pickup processes do not interfere with each other, improving the symmetry of the differential structure, enhancing the common-mode noise suppression effect, and thus significantly improving the signal-to-noise ratio of the measurement signal and the overall measurement accuracy.

[0031] Please see Figure 3As shown, in some embodiments, the piezoelectric driving layer 10 includes a bottom electrode 12, a piezoelectric material layer 13 and a top electrode 14. An insulating layer 11 is deposited on the device layer 3, and the bottom electrode 12 is deposited on the insulating layer 11. The device layer 3 and the piezoelectric driving layer 10 are electrically isolated from each other through the insulating layer 11.

[0032] The piezoelectric material layer 13 can be made of piezoelectric materials such as lead zirconate titanate (PZT), aluminum nitride (AlN), or zinc oxide (ZnO), with a thickness of 0.5-2 μm. The bottom electrode 12, the piezoelectric material layer 13, and the top electrode 14 are deposited sequentially using MEMS technology to form the piezoelectric driving layer 10.

[0033] Electrical isolation between device layer 3 and piezoelectric drive layer 10 is achieved through insulating layer 11, ensuring electrical insulation and non-conduction between the two layers while maintaining mechanical connection or structural support. This achieves electrical separation between the driving function and signal acquisition function. Insulating layer 11 effectively blocks direct coupling and crosstalk between the driving electric field and driving current of piezoelectric drive layer 10 and the electrodes of device layer 3, preventing interference from the driving signal to weak measured electric field signals. It also ensures the potential independence of piezoelectric drive layer 10 and device layer 3, providing a stable dielectric environment for the grounding shielding design of piezoelectric drive layer 10. Furthermore, insulating layer 11 provides mechanical support and stress buffering, improving the stability of the interlayer structure and preventing short circuits and signal distortion caused by electrical conduction between different functional layers. This provides reliable electrical isolation for the symmetrical operation of the differential electrode group and high-precision signal acquisition.

[0034] In some embodiments, both the measuring electrode group 4 and the reference electrode group 5 are configured to be at least one.

[0035] The number of measuring electrode groups 4 and reference electrode groups 5 can be expanded according to actual needs. For example, multiple measuring electrode groups 4 and multiple reference electrode groups 5 can be arranged alternately, and the first fixed electrode 7 and the first movable electrode 6 adopt an interlaced comb structure to improve the effective sensing area and sensitivity.

[0036] Please see Figure 1 As shown, in some embodiments, the measuring electrode group 4 includes a first movable electrode 6 and a first fixed electrode 7. The first movable electrode 6 is connected below the piezoelectric driving layer 10 and is driven by the piezoelectric driving layer 10 to generate reciprocating vibration perpendicular to the sensitive chip substrate. The first fixed electrode 7 is fixedly connected to the substrate layer 1. The reference electrode group 5 includes a second movable electrode 8 and a second fixed electrode 9. The second movable electrode 8 is connected below the piezoelectric driving layer 10 and is driven by the piezoelectric driving layer 10 to generate reciprocating vibration perpendicular to the sensitive chip substrate. The second movable electrode 8 and the first movable electrode 6 have the same physical structure. The second fixed electrode 9 is fixedly connected to the substrate layer 1 and has the same physical structure as the first fixed electrode 7.

[0037] The reference electrode group 5 is physically identical to the measurement electrode group 4; that is, the second fixed electrode 9 has the same geometric dimensions, material properties, and boundary conditions as the first fixed electrode 7; and the second movable electrode 8 has the same geometric dimensions, material properties, and boundary conditions as the first movable electrode 6. Both electrode groups are fabricated synchronously under the same MEMS process conditions, exhibiting highly consistent matching characteristics in dimensions, parasitic parameters, temperature coefficients, and other dimensions. The reference electrode group 5 is used only to pick up environmental common-mode noise, such as temperature drift, mechanical vibration, electromagnetic interference, and piezoelectric drive signal crosstalk.

[0038] In some embodiments, the first fixed electrode 7 and the first movable electrode 6 are both sensing electrodes, and the first fixed electrode 7 and the first movable electrode 6 are mutual shielding electrodes.

[0039] Specifically, both the first movable electrode 6 and the first fixed electrode 7 sense external electric field signals but are not electrically connected to external ground signals. The bottom electrode of the piezoelectric drive layer 10 is electrically connected to the external ground through a wire.

[0040] The first fixed electrode 7 shields the first movable electrode 6, and the first movable electrode 6 shields the first fixed electrode 7, forming a mutually shielded operating mode. Driven by the piezoelectric driving layer 10, the first movable electrode 6 vibrates perpendicular to the sensitive chip substrate, forming mutual shielding with the first fixed electrode 7. That is, when the first movable electrode 6 approaches the first fixed electrode 7, the degree of shielding of the first movable electrode 6 by the first fixed electrode 7 increases, and the amount of induced charge on the surface of the first movable electrode 6 decreases, while the degree of shielding of the first fixed electrode 7 by the first movable electrode 6 decreases, and the amount of induced charge on the surface of the first fixed electrode 7 increases; and vice versa. Thus, induced current signals with a phase difference of 180° are generated on the first fixed electrode 7 and the first movable electrode 6, respectively. The process by which the second movable electrode 8 and the second fixed electrode 9 generate induced current signals with a phase difference of 180° is the same as the process by which the first movable electrode 6 and the first fixed electrode 7 generate induced current signals with a phase difference of 180°, and will not be described again here.

[0041] A sinusoidal AC driving voltage with identical amplitude, frequency, and phase is applied to the top electrode 14 of the piezoelectric driving layer 10 corresponding to the measuring electrode group 4 and the reference electrode group 5. Since the two electrode groups have symmetrical structures and the same driving conditions, the first movable electrode 6 on the measuring side and the second movable electrode 8 on the reference side generate vertical vibrations with the same frequency, phase, and synchronization under the action of the piezoelectric effect. The amplitude of their movements and the timing of their vibrations are completely matched.

[0042] The two induced signals output from the first fixed electrode 7 and the first movable electrode 6 of the measuring electrode group 4 are differentially processed with a 180° phase difference to obtain a measurement differential signal containing the information of the electric field to be measured and residual common-mode noise. The two reference signals output from the second fixed electrode 9 and the second movable electrode 8 of the reference electrode group 5 are differentially processed to obtain a reference differential signal containing only common-mode noise. By performing a second differential processing on the measurement differential signal and the reference differential signal, the residual common-mode noise component in the measurement differential signal can be eliminated, resulting in a high signal-to-noise ratio output signal that is only proportional to the magnitude of the electric field to be measured.

[0043] Please see Figure 2 As shown, in some embodiments, both the first movable electrode 6 and the first fixed electrode 7 adopt a comb-tooth structure and are arranged alternately at equal intervals in the horizontal direction to form a comb-tooth-shaped capacitive sensing structure. The measuring electrode group 4 picks up the external electric field sensing signal through the comb-tooth-shaped capacitive sensing structure and outputs the induced charge signal through the output electrode 15. The output electrode 15 is electrically connected to the external detection circuit.

[0044] The interlaced comb structure can significantly increase the effective sensing area between electrodes, improving the electric field sensing sensitivity and signal strength; the equidistant arrangement ensures uniform electric field distribution and stable capacitance parameters, reducing errors caused by structural asymmetry; the sensing signal is stably led out to the external detection circuit through the output electrode 15, realizing reliable signal transmission.

[0045] In some embodiments, the two induced charge signals output from the measuring electrode group 4 and the reference electrode group 5 are converted into voltage signals and amplified by a differential amplifier circuit to obtain the measured value of the electric field strength.

[0046] The measuring electrode group 4 outputs an induced charge signal containing the measured electric field signal and common-mode noise, while the reference electrode group 5 outputs an induced charge signal containing only common-mode noise. These two induced charge signals are input to a differential amplifier circuit, which first converts the induced charge signal into a voltage signal, then amplifies the differential voltage signal, and finally outputs an electrical signal proportional to the external electric field strength. The measured value of the electric field strength is then calculated from this signal. By converting and amplifying the weak induced charge signal into a standard voltage signal, the signal-to-noise ratio, measurement sensitivity, and measurement accuracy are significantly improved, ensuring the accuracy and reliability of the electric field strength measurement results.

[0047] Please see Figure 4 As shown, this application embodiment provides an electric field sensor, which includes a non-invasive voltage-sensitive element and a housing 17 outside the non-invasive voltage-sensitive element. An insulating cover plate 18 is installed on the top of the housing 17. A through hole is machined on the insulating cover plate 18 at the position corresponding to the reference electrode group 5. I-shaped shielding electrodes 16 are inserted into the through hole. The shielding electrodes 16 are connected to the external ground signal and are used to shield the reference electrode group 5 from sensing the external electric field.

[0048] Please refer to Figure 4 , in an actual electric field measurement process, under the action of an external electric field E to be measured that is perpendicular to the plane of the sensor, under the mutual shielding effect of the first movable electrode 6 and the first fixed electrode 7 of the measurement electrode group 4, periodically varying charges are generated on the electrode surfaces. For the reference electrode group 5, since the shielding electrode 16 is connected to the ground, electric field shielding is provided for the second movable electrode 8 and the second fixed electrode 9 of the reference electrode group 5, and the charges on the surfaces of these two electrodes do not change with the variation of the external electric field E.

[0049] The material of the insulating cover plate 18 includes but is not limited to insulating materials such as silicon oxide and aluminum oxide.

[0050] It should be noted that in the embodiment of the present application, the I-shaped distributed shielding electrode 16 is not entirely inserted into the through hole, but is inserted as shown in the appended Figure 4 drawing, that is, the vertical part of the I-shape is inserted into the through hole, and the horizontal parts of the I-shape are respectively located above and below the insulating cover plate 18. By inserting the shielding electrode 16 into the insulating cover plate 18 above the position where the reference electrode group 5 is located, electric field shielding for the reference electrode group 5 is achieved.

[0051] Please refer to Figure 5 , in another aspect of the embodiment of the present application, a preparation method of a non-intrusive voltage sensitive element based on a piezoelectric mutual-shielding differential structure is provided, and the preparation method comprises: Step 1: selecting an SOI substrate as a wafer for preparation, cleaning the wafer, and depositing an insulating layer 11 on the surface of the device layer 3; after selecting an SOI substrate as the wafer for preparation and removing contaminants on the wafer surface through a standard cleaning process, a thermal oxidation process is used to deposit a layer of silicon oxide, i.e., the insulating layer 11, on the surface of the device layer 3, and the thickness is 100-500 nm.

[0052] Step 2: depositing a bottom electrode 12 on the insulating layer 11, and performing patterning processing on the bottom electrode 12; the bottom electrode 12 is deposited on the insulating layer 11 through processes such as physical vapor deposition (PVD) or electron beam evaporation, the material of the bottom electrode 12 can be selected from composite metal layers such as Pt / Ti and Au / Cr, and the thickness is 100-300 nm. Patterning processing is performed on the bottom electrode 12 through photolithography and etching processes.

[0053] Step 3: Deposit a piezoelectric material layer 13 on the bottom electrode 12. The material of the piezoelectric material layer 13 can be lead zirconate titanate (PZT), aluminum nitride (AlN), or zinc oxide (ZnO). For PZT, it can be deposited using the sol-gel method or magnetron sputtering, with a thickness of 0.5-2 μm. The deposited PZT film needs to be annealed to complete perovskite crystallization. For AlN, it can be deposited using reactive magnetron sputtering. The piezoelectric material layer 13 is patterned using photolithography and etching processes, with wet etching or dry etching methods being acceptable.

[0054] Step four: Deposit the top electrode 14 on the piezoelectric material layer 13 to obtain the deposited wafer; deposit the top electrode 14 on the piezoelectric material layer 13 by PVD or electron beam evaporation. The material of the top electrode 14 can be metals such as Pt or Au, and the thickness is 100-300 nm. Pattern the top electrode 14 through photolithography and etching processes to form the upper and lower electrode structures of the piezoelectric driving layer 10.

[0055] Step 5: Photoresist is coated onto the deposited wafer surface. The comb-like structure of the measurement electrode group 4 and reference electrode group 5 is etched using an etching process, with the etching depth extending to the insulating isolation layer 2 at the bottom of device layer 3. Photoresist is then coated onto the SOI wafer surface, and the pattern of the comb-like electrodes is defined using photolithography. Specifically, a high aspect ratio etching process (DRIE / deep reactive ion etching) is used to etch the comb-like structure of the measurement electrode group 4 and reference electrode group 5. The etching depth is precisely controlled to extend to the insulating isolation layer 2 at the bottom of the device layer, using the insulating isolation layer 2 as the etching termination layer to ensure uniform thickness and depth of the comb-like electrodes. The measurement electrode group 4 and reference electrode group 5 are fabricated simultaneously in the same process step to ensure high consistency in their structural parameters, such as comb tooth spacing, width, depth, and length.

[0056] Step six: Photoresist is coated on the back side of the wafer. After photolithographic patterning, the measurement electrode group 4 and reference electrode group 5 are obtained. Photoresist is coated on the back side of the wafer, and the area of ​​substrate layer 1 to be removed is defined by photolithographic patterning. A deep silicon etching process is used to completely etch the substrate layer 1 on the back side of the measurement electrode group 4 and reference electrode group 5 structures, leaving only the device layer 3 and the insulating isolation layer 2. A dry etching process, such as hydrofluoric acid vapor phase etching, is used to remove the exposed insulating isolation layer 2 at the bottom of the device layer 3, separating the movable electrode from the substrate and fixed support structure, thus achieving mechanical release of the movable electrode and allowing it to vibrate freely.

[0057] Backside etching removes substrate layer 1, eliminating its parasitic capacitance and electrical interference to the electrodes of device layer 3, and reducing measurement noise. Removing the insulating isolation layer 2 allows for complete release of the movable electrode, enabling it to vibrate freely under piezoelectric actuation, providing the necessary conditions for mechanical modulation of the electric field signal. This process ensures electrical isolation and mechanical separation between the movable and fixed electrodes, avoiding failures such as adhesion and short circuits, and improving device yield and long-term stability.

[0058] In steps five and six, the movable electrodes of the measuring electrode group 4 and the movable electrodes of the reference electrode group 5 are fabricated simultaneously on the same device layer and released through the same etching step to ensure that the thickness, size and stiffness parameters of the two sets of movable electrodes are completely consistent.

[0059] This application provides a non-invasive voltage-sensitive element based on a piezoelectric mutually shielded differential structure and its fabrication method. By introducing a reference electrode group with the same physical structure as the measuring electrode group, the object of differential detection is changed from fixed and movable electrodes to the measuring electrode group and the reference electrode group. The measuring electrode group is used to pick up the electric field signal to be measured and environmental common-mode noise, while the reference electrode group only picks up environmental common-mode noise. After differential processing, a pure signal to be measured can be obtained. Furthermore, since the two electrode groups are fabricated synchronously in the same MEMS process, their structural parameters are highly consistent, and the common-mode noise exhibits almost the same amplitude and phase in the two outputs, which is completely suppressed after differential processing. Through the fully symmetrical design of the measuring electrode group and the reference electrode group, not only are external common-mode noises such as environmental temperature drift and mechanical vibration eliminated, but crosstalk of the piezoelectric drive signal can also be effectively canceled, achieving a multi-level common-mode suppression effect.

[0060] Furthermore, this application organically combines the advantages of piezoelectrically shielded differential structures with the requirements of non-invasive voltage measurement. It retains the advantages of low operating voltage and high charge induction efficiency of piezoelectrically shielded differential structures while addressing their shortcomings in non-invasive voltage measurement applications through a fully symmetrical reference electrode group and package optimization. The sensing element of this application is fabricated using mature MEMS processing technology, offering strong process compatibility and enabling low-cost, high-consistency mass production to meet the application requirements of wide-area deployment and distributed monitoring.

[0061] The embodiments described in this application are for the purpose of more clearly illustrating the technical solutions of the embodiments of this application, and do not constitute a limitation on the technical solutions provided by the embodiments of this application. As those skilled in the art will know, with the evolution of technology and the emergence of new application scenarios, the technical solutions provided by the embodiments of this application are also applicable to similar technical problems.

[0062] Those skilled in the art will understand that the technical solutions shown in the figures do not constitute a limitation on the embodiments of this application, and may include more or fewer steps than shown, or combine certain steps, or different steps.

[0063] Those skilled in the art will understand that all or some of the steps in the methods disclosed above, as well as the functional modules / units in the systems and devices, can be implemented as software, firmware, hardware, or suitable combinations thereof.

[0064] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0065] The preferred embodiments of the present application have been described above with reference to the accompanying drawings, but this does not limit the scope of the claims of the present application. Any modifications, equivalent substitutions, and improvements made by those skilled in the art without departing from the scope and substance of the embodiments of the present application shall be within the scope of the claims of the present application.

Claims

1. A non-invasive voltage-sensitive element based on a piezoelectric mutually shielded differential structure, characterized in that, It includes a substrate layer, an insulating isolation layer, a device layer, and a piezoelectric drive layer; The substrate layer, insulating isolation layer, and device layer are sequentially fixedly connected to form a substrate; the piezoelectric driving layer is deposited on top of the substrate. The device layer includes a measurement electrode group and a reference electrode group with identical physical structures. Both the measurement electrode group and the reference electrode group include movable electrodes. Under the action of the driving voltage, the piezoelectric driving layer generates a vibration displacement perpendicular to the chip plane, driving the connected movable electrodes to move. The measuring electrode group picks up the electric field signal to be measured and the ambient common-mode noise, while the reference electrode group only picks up the ambient common-mode noise. The two sets of signals output by the measuring electrode group and the reference electrode group are processed differentially to obtain the electric field signal to be measured.

2. The non-invasive voltage-sensitive element based on a piezoelectric mutually shielded differential structure according to claim 1, characterized in that, The piezoelectric drive layer is mounted above the movable electrode and connected to the movable electrode. The bottom electrode of the piezoelectric drive layer is grounded through a wire.

3. The non-invasive voltage-sensitive element based on a piezoelectric mutually shielded differential structure according to claim 1, characterized in that, The piezoelectric driving layer includes a bottom electrode, a piezoelectric material layer, and a top electrode. An insulating layer is deposited on the device layer, and a bottom electrode is deposited on the insulating layer. Electrical isolation between the device layer and the piezoelectric driving layer is achieved through the insulating layer.

4. The non-invasive voltage-sensitive element based on a piezoelectric mutually shielded differential structure according to claim 1, characterized in that, Both the measuring electrode group and the reference electrode group are configured to be at least one.

5. The non-invasive voltage-sensitive element based on a piezoelectric mutually shielded differential structure according to claim 1, characterized in that, The measuring electrode group includes a first movable electrode and a first fixed electrode. The first movable electrode is connected below the piezoelectric driving layer and is driven by the piezoelectric driving layer to generate reciprocating vibration perpendicular to the sensitive chip substrate. The first fixed electrode is fixedly connected to the substrate layer. The reference electrode group includes a second movable electrode and a second fixed electrode. The second movable electrode is connected below the piezoelectric driving layer and is driven by the piezoelectric driving layer to generate reciprocating vibration perpendicular to the sensitive chip substrate. The second movable electrode has the same physical structure as the first movable electrode. The second fixed electrode is fixedly connected to the substrate layer and has the same physical structure as the first fixed electrode.

6. The non-invasive voltage-sensitive element based on a piezoelectric mutually shielded differential structure according to claim 5, characterized in that, Both the first fixed electrode and the first movable electrode are sensing electrodes, and the first fixed electrode and the first movable electrode are mutual shielding electrodes.

7. The non-invasive voltage-sensitive element based on a piezoelectric mutually shielded differential structure according to claim 6, characterized in that, Both the first movable electrode and the first fixed electrode adopt a comb-tooth structure and are arranged alternately at equal intervals in the horizontal direction to form a comb-tooth-shaped capacitive sensing structure. The measuring electrode group picks up the external electric field sensing signal through the comb-tooth-shaped capacitive sensing structure and outputs the induced charge signal through the output electrode. The output electrode is electrically connected to the external detection circuit.

8. The non-invasive voltage-sensitive element based on a piezoelectric mutually shielded differential structure according to claim 1, characterized in that, The two induced charge signals output from the measuring electrode group and the reference electrode group are converted into voltage signals by a differential amplifier circuit and amplified to obtain the measured value of the electric field strength.

9. An electric field sensor, characterized in that, The electric field sensor includes a non-invasive voltage-sensitive element based on a piezoelectric mutually shielded differential structure as described in any one of claims 1-8, and a housing outside the non-invasive voltage-sensitive element. An insulating cover plate is installed on the top of the housing. Through holes are machined on the insulating cover plate at positions corresponding to the reference electrode group. I-shaped shielding electrodes are inserted into the through holes. The shielding electrodes are connected to an external ground signal to shield the reference electrode group from sensing external electric fields.

10. A method for fabricating a non-invasive voltage-sensitive element based on a piezoelectrically shielded differential structure, applicable to the non-invasive voltage-sensitive element based on a piezoelectrically shielded differential structure as described in any one of claims 1-8, characterized in that, The preparation method includes: SOI substrates were selected as the wafers for fabrication, and an insulating layer was deposited on the surface of the device layer after cleaning. A bottom electrode is deposited on the insulating layer, and the bottom electrode is patterned. A piezoelectric material layer is deposited on the bottom electrode; A top electrode is deposited on the piezoelectric material layer to obtain a deposited wafer; Photoresist is coated on the surface of the wafer after deposition, and the comb structure of the measurement electrode group and the reference electrode group is etched by etching process until the etching depth reaches the insulating isolation layer at the bottom of the device layer. Photoresist is coated on the back of the wafer, and after photolithography patterning, the measurement electrode group and the reference electrode group are obtained.

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