Pressure-sensitive unit, pressure sensor, sensor module, and electronic device

Abstract

A pressure sensitive unit, a pressure sensor, a sensor module and an electronic device, the pressure sensitive unit comprising: a substrate provided with a concave cavity, the concave cavity having a first boundary and a second boundary; a piezoelectric resonant part, the piezoelectric resonant part comprising a piezoelectric layer and a substrate, the substrate having a first connecting edge and a second connecting edge, the piezoelectric layer being attached to a surface of the substrate, the first connecting edge being coupled to the first boundary, and the second connecting edge being spaced apart from the second boundary; wherein, under the action of an excitation signal, the piezoelectric resonant part resonates due to the inverse piezoelectric effect of the piezoelectric layer; when an external pressure acts on the piezoelectric resonant part, the piezoelectric layer deforms, the resonant frequency of the piezoelectric resonant part shifts, and the shift amount of the resonant frequency is used to determine the value of the external pressure. The piezoelectric resonant part is connected and fixed to the substrate through the first connecting edge, has the characteristics of higher mechanical stability, not easy to damage, convenient to process, low preparation cost and design complexity, high sensitivity, small size and low power consumption.

Description

Technical Field

[0001] This application relates to the field of sensor technology, and in particular to pressure-sensitive units, pressure sensors, sensor modules, and electronic devices. Background Technology

[0002] A pressure sensor is a sensor that can sense and measure the pressure exerted on an object and convert it into an electrical signal. It has wide applications in aerospace, consumer electronics, automotive, healthcare, and other production and daily life sectors. For example, in the medical field, pressure sensors are widely used to detect pulse pressure waves, providing crucial support for non-invasive cardiovascular health monitoring. Therefore, a pressure sensor is needed to detect external pressure values ​​in various application scenarios. Summary of the Invention

[0003] To address the aforementioned issues, embodiments of this application provide a pressure-sensitive unit, a pressure sensor, a sensor module, and an electronic device, which can be used to detect the value of external pressure in various application scenarios.

[0004] Therefore, the following technical solutions are adopted in the embodiments of this application:

[0005] In a first aspect, embodiments of this application provide a pressure-sensitive unit, comprising: a substrate having a cavity, the cavity having a first boundary and a second boundary; and a piezoelectric resonant portion, the piezoelectric resonant portion including a piezoelectric layer and a substrate, the substrate having a first connecting edge and a second connecting edge, the piezoelectric layer being attached to the surface of the substrate, the first connecting edge being fixedly connected to the first boundary, and the second connecting edge being spaced apart from the second boundary. Under the action of an excitation signal, the piezoelectric resonant portion resonates due to the inverse piezoelectric effect of the piezoelectric layer; when external pressure acts on the piezoelectric resonant portion, the piezoelectric layer deforms, and the resonant frequency of the piezoelectric resonant portion shifts, the amount of which is used to determine the value of the external pressure.

[0006] In this embodiment, the piezoelectric resonator is suspended in the cavity, enabling resonant motion. When external pressure is applied, the resonant frequency shifts due to the deformation of the piezoelectric layer. The magnitude of the external pressure can be obtained from the frequency shift. The piezoelectric resonator is fixed to the substrate via a first connecting edge, resulting in higher mechanical stability and less susceptibility to damage. It is also easier to process, reducing manufacturing costs and design complexity. For example, small or ultra-small pressure-sensitive units can be obtained using photolithography and other processes, thus meeting the needs of complex pressure detection scenarios. The pressure-sensitive unit in this embodiment is highly sensitive; the piezoelectric resonator is extremely sensitive to pressure, causing varying degrees of frequency shift in different resonant modes under different pressure levels. While achieving a small size, the pressure-sensitive unit in this embodiment requires very little driving current, thus exhibiting low power consumption.

[0007] In one possible implementation, the first connecting edge and the first boundary are fixed by at least one first extension structure. The first extension structure is a structure in which the connecting segment of the first connecting edge extends to the first boundary along a preset direction. The connecting segment is a part of the boundary of the first connecting edge, and the preset direction is a direction perpendicular to the first connecting edge and pointing to the first boundary.

[0008] In this implementation, the substrate and the base plate are fixed by one or more first extension structures of the first connecting edge. When fixed by the first extension structure, the same pressure can generate greater stress, resulting in a greater change in the elastic modulus of the piezoelectric layer and a greater deviation in the resonant frequency, thereby improving the pressure sensitivity of the device.

[0009] In one possible implementation, the number of first extension structures is a preset number, which is related to the performance requirements of the pressure-sensitive unit; and / or, the geometric dimensions of the first extension structures are preset dimensions, which are related to the performance requirements of the pressure-sensitive unit.

[0010] In this implementation, the number and geometric dimensions of the first extension structures can be designed according to the performance requirements of the pressure-sensitive unit. For example, the pressure-sensing performance of the pressure-sensitive unit can be adjusted by changing the number of the first extension structures. For instance, with a larger number of first extension structures, the same external pressure can cause greater strain and deformation in the piezoelectric layer, thereby improving the pressure sensitivity of the pressure-sensitive unit. In other words, the sensitivity, stability, and power consumption of the pressure-sensitive unit can be balanced by adjusting the number and dimensions of the first extension structures.

[0011] In one possible implementation, the first connecting edge and the first boundary are fixed by a second extension structure, which is a structure in which the first connecting edge extends to the first boundary along a preset direction, the preset direction being a direction perpendicular to the first connecting edge and pointing towards the first boundary.

[0012] In this implementation, the substrate and the base are fixed together by the entire edge of the first connecting edge. The first connecting edge extends to the first boundary along a preset direction to obtain the second extension structure. The fixing method of the second extension structure has higher mechanical stability, is less prone to damage, and is easier to process, with lower manufacturing cost and design complexity.

[0013] In one possible implementation, the shift in the resonant frequency of the piezoelectric resonator is linearly related to the external pressure.

[0014] In this implementation, the shift in the resonant frequency of the piezoelectric resonator is linearly related to the external pressure, allowing for better calibration of the external pressure based on the resonant frequency shift. This linear relationship ensures that the same external pressure shift results in the same resonant frequency shift, providing the pressure-sensitive unit with stable measurement accuracy, making it suitable for high-precision applications.

[0015] In one possible implementation, the offset of the resonant frequency of the piezoelectric resonator is equal to the product of the external pressure and the pressure coefficient, which is related to the elastic modulus of the piezoelectric layer.

[0016] In this implementation, external pressure causes a change in the elastic modulus of the piezoelectric layer, which in turn causes a change in the resonant frequency. For example, based on the elastic modulus of the piezoelectric layer, a formula can be derived showing that the shift in the resonant frequency equals the product of the external pressure and the pressure coefficient. Furthermore, this formula can serve as the design basis for the piezoelectric layer structure.

[0017] In one possible implementation, the length of the first connecting edge is greater than the length of the second connecting edge; and / or, the ratio of the length of the first connecting edge to the length of the second connecting edge is a preset ratio.

[0018] This implementation provides the size relationship between the fixed boundary (first connecting edge) and the free boundary (second connecting edge) when designing the piezoelectric resonator. Based on practical experience, when the length of the first connecting edge is greater than the length of the second connecting edge—for example, when the ratio of the length of the first connecting edge to the length of the second connecting edge is a preset ratio (e.g., 2)—the overall performance of the pressure-sensitive unit is better, and the balance between sensitivity, mechanical stability, and power consumption is improved.

[0019] In one possible implementation, the base is polygonal in shape, the first connecting edge includes at least two opposite sides of the polygon, and the second connecting edge is any edge other than the first connecting edge.

[0020] In this implementation, the base material is polygonal, such as quadrilateral, hexagon, or octagon. The first connecting edge includes at least two opposite edges of the polygon, which gives the pressure-sensitive unit symmetry and improves its overall performance.

[0021] In one possible implementation, the piezoelectric layer also has a front side, which is the side of the piezoelectric layer opposite to the back side. The aforementioned piezoelectric resonator further includes: an excitation electrode attached to the front side of the piezoelectric layer for loading an excitation signal; and a detection electrode attached to the front side of the piezoelectric layer, forming an interdigitated electrode structure with the excitation electrode, for receiving the electrical signal generated by the resonance of the piezoelectric resonator.

[0022] In this implementation, the excitation electrode is equivalent to the driving electrode, used to drive the resonant motion of the piezoelectric resonator; the detection electrode is equivalent to the vibration pickup unit, used to detect the electrical signal generated by the resonance, and then determine the value of the external pressure based on the resonant frequency. The detection electrode and the excitation electrode form an interdigitated electrode structure. The multi-interdigitated structure in the interdigitated electrode structure can effectively excite the vibration modes of the Lamb wave device, and has the characteristics of compact structure and suitability for miniaturization scenarios.

[0023] In one possible implementation, the first connecting edge is a boundary in the substrate extending along a first direction, which is the direction in which the interdigitated fingers extend longitudinally in the interdigitated electrode structure; or, the first connecting edge is a boundary in the substrate extending along a second direction, which is the direction in which the interdigitated fingers are arranged laterally in the interdigitated electrode structure.

[0024] In this implementation, the relationship between the first connecting edge and the interdigitating direction in the interdigitated electrode structure is provided. The first connecting edge can be a boundary extending along a first direction in the substrate, or it can be a boundary extending along a second direction in the substrate. For example, the first connecting edge can be a boundary extending along the first direction in the substrate. That is, when the first connecting edge is parallel to the interdigitating direction in the interdigitated electrode structure, the performance of the pressure-sensitive unit is better, and the various performance characteristics of the pressure-sensitive unit are further improved.

[0025] In one possible implementation, the pressure-sensitive unit further includes: a first electrode disk and a second electrode disk, respectively attached to a substrate. The first electrode disk is used to receive an externally input excitation signal, and the second electrode disk is used to output an electrical signal generated by the resonance of the piezoelectric resonator. The piezoelectric resonator further includes: a first transmission line and a second transmission line, respectively attached to the surface of the substrate. The two ends of the first transmission line are electrically connected to the excitation electrode and the first electrode disk, respectively, and the two ends of the second transmission line are electrically connected to the detection electrode and the second electrode disk, respectively.

[0026] In this implementation, the electrode disk is used to receive external signals; the transmission line is used to transmit signals between the electrodes and the electrode disk; the electrodes are used to drive the piezoelectric layer to vibrate based on the inverse piezoelectric effect, or to pick up electrical signals generated by resonant deformation from the piezoelectric layer based on the piezoelectric effect. The electrode disk, transmission line, and electrodes form a complete signal transmission path; the first electrode disk, first transmission line, and excitation electrode form a signal transmission path for the excitation signal; the second electrode disk, second transmission line, and detection electrode form a signal transmission path for the detection signal (i.e., the electrical signal generated by resonant deformation). The first and second transmission lines are attached to the surface of the substrate, which can match the structure of the piezoelectric resonator and avoid the free boundaries of the piezoelectric resonator, thereby achieving electrical connection between the electrodes and the electrode disk.

[0027] In one possible implementation, the pressure-sensitive unit further includes: a first isolation oxide layer disposed between the first transmission line, the second transmission line and the substrate, and / or disposed between the first electrode disk, the second electrode disk and the substrate.

[0028] In this implementation, the first isolation oxide layer can effectively achieve electrical isolation between the transmission line (e.g., the first transmission line and the second transmission line) and the substrate. Furthermore, the first isolation oxide layer can also effectively achieve electrical isolation between the electrode disk (e.g., the first electrode disk and the second electrode disk) and the substrate.

[0029] In one possible implementation, the pressure-sensitive unit further includes: a plurality of ground electrode disks attached to the substrate, wherein the plurality of ground electrode disks are disposed outside the first electrode disk and outside the second electrode disk.

[0030] In this implementation, several grounding electrode disks are arranged outside the first electrode disk and outside the second electrode disk, which can effectively form a GSG (Ground-Signal-Ground) electrode structure, and can effectively reduce the loss in the signal transmission process.

[0031] In one possible implementation, the pressure-sensitive unit is obtained by depositing a piezoelectric layer on the wafer and etching the wafer; wherein the substrate, the base, and the connection portion between the substrate and the base are the retained portions after the wafer is etched.

[0032] This implementation provides a fabrication process for a pressure-sensitive unit. In this process, the structure of the pressure-sensitive unit is relatively simple; all structures can be fabricated in a single photolithography process, resulting in higher process reliability.

[0033] In one possible implementation, the wafer is a silicon wafer, which includes a doped silicon layer, a second isolation oxide layer, and a silicon substrate stacked sequentially, with the second isolation oxide layer disposed between the doped silicon layer and the silicon substrate; after the wafer is etched, the substrate includes a doped silicon layer, the substrate includes a doped silicon layer, the second isolation oxide layer, and the silicon substrate, and the connection portion between the substrate and the base includes a doped silicon layer.

[0034] This implementation provides a specific method for fabricating the pressure-sensitive unit. The wafer is a silicon wafer, a common type of SOI (Silicon-on-Insulator) wafer, whose fabrication process is more mature and easier to miniaturize.

[0035] Secondly, embodiments of this application provide a pressure sensor, including: a pressure-sensitive unit according to any one of the first aspects and possible implementations described above; an oscillation circuit electrically connected to the pressure-sensitive unit, wherein the oscillation circuit processes the input signal and outputs an excitation signal, and the piezoelectric resonant part resonates under the action of the excitation signal.

[0036] In this embodiment, the oscillation circuit is powered by a power supply. The oscillation circuit generally includes an amplification module and a phase shifter. The oscillation circuit can process the input signal and output a corresponding excitation signal, thereby causing the pressure-sensitive unit to resonate at the corresponding frequency.

[0037] Thirdly, embodiments of this application provide a sensor module, including: the aforementioned pressure sensor; and a processing module electrically connected to the pressure sensor of the second aspect, used to obtain the value of external pressure based on the offset of the resonant frequency of the aforementioned pressure sensor.

[0038] In this implementation, the processing module (such as a frequency meter) can detect the resonant frequency corresponding to the resonance of the pressure-sensitive unit. For example, when the pressure-sensitive unit is subjected to pressure, the offset data of the resonant frequency is measured by the frequency meter and output to the host computer.

[0039] Fourthly, embodiments of this application provide an electronic device comprising a device body and a pressure sensing device. The pressure sensing device is at least one of the pressure-sensitive unit of any of the first aspect and its possible implementations described above, the pressure sensor of the third aspect described above, and the sensor module of the second aspect described above.

[0040] In this implementation, the electronic device can be any electronic device including the aforementioned pressure-sensitive unit, pressure sensor, and sensor module, such as mobile phones, watches, laptops, remote controls, etc.; wearable devices such as headphones, watches, bracelets, glasses, rings, etc.; and blood pressure detection devices such as medical blood pressure monitoring devices and traditional Chinese medicine pulse pillow devices. Taking the medical field as an example, the electronic device can be a blood pressure monitoring device, in which the pressure sensor can be used to detect human pulse pressure wave information, providing important support for non-invasive monitoring of cardiovascular health; furthermore, the blood pressure data detected by the pressure sensor can accurately locate the position of arteries, thereby improving the effectiveness of diagnostic information and the accuracy of disease detection results.

[0041] The beneficial effects of the second, third, and fourth aspects of the embodiments of this application are described in the first aspect, and will not be repeated here to avoid repetition. Attached Figure Description

[0042] The accompanying drawings used in the embodiments or technical description are briefly introduced below.

[0043] Figure 1a This is a top view of the pressure-sensitive unit provided in the embodiments of this application;

[0044] Figure 1b This is a schematic diagram of the unloaded state of the pressure-sensitive unit provided in the embodiments of this application;

[0045] Figure 1c This is a schematic diagram of the load-bearing state of the pressure-sensitive unit provided in the embodiments of this application;

[0046] Figure 1 is a schematic diagram of a pressure-sensitive unit provided in an embodiment of this application from the front view.

[0047] Figure 2a This is a schematic diagram of the front view of a pressure-sensitive unit provided in an embodiment of this application;

[0048] Figure 2b This is a schematic diagram of a pressure-sensitive unit provided in an embodiment of this application from a first oblique view (back side of the substrate);

[0049] Figure 2c This is a schematic diagram of a pressure-sensitive unit provided in an embodiment of this application from a second oblique view (front side of the substrate);

[0050] Figure 3 This is a schematic diagram of an oblique view of a piezoelectric resonator provided in an embodiment of this application;

[0051] Figure 4This is a schematic diagram of a cross-sectional view of the transmission line location provided in the embodiments of this application;

[0052] Figure 5 This is a schematic diagram of a cross-sectional view of the electrode positions provided in the embodiments of this application;

[0053] Figure 6 This is a schematic diagram of another piezoelectric sensing unit provided in the embodiments of this application;

[0054] Figure 7 This is a schematic diagram of the piezoelectric resonant section of another piezoelectric sensitive unit provided in the embodiments of this application;

[0055] Figure 8 This is a schematic diagram of another piezoelectric sensing unit provided in the embodiments of this application;

[0056] Figure 9 This is a schematic diagram showing the relationship between the resonant frequency and pressure of the pressure-sensitive unit when the connection structure between the substrate and the matrix is ​​different in the embodiments of this application;

[0057] Figure 10 This is a schematic diagram showing the relationship between the resonant frequency and pressure of a pressure-sensitive unit with multiple first extension structures at different positions, as provided in the embodiments of this application.

[0058] Figure 11 This is a schematic diagram showing the relationship between the admittance and resonant frequency of the pressure-sensitive unit when the coupling method between the first connecting edge and the substrate is different in the embodiments of this application.

[0059] Figure 12 This is a schematic diagram of the composition of a pressure sensor and sensor module provided in the embodiments of this application.

[0060] The annotations in the attached figures are explained as follows:

[0061] 100-Pressure-sensitive unit, 110-Substrate, 111-Cavity, 111-1-First boundary, 111-2-Second boundary, 120-Piezoelectric resonator, 121-Piezoelectric layer, 121-1-Back side, 121-2-Front side, Substrate 122, 122-1-Surface, 122-2-First connecting edge, 122-2-1-First extension structure, 122-2-1′-Second extension structure, 22-2-1″-Third extension structure 1, 122-3-Second connecting edge, 123-Excitation electrode, 124-Detection electrode, 125-First transmission line, 126-Second transmission line, 130-First electrode disk, 140-Second electrode disk, 150-First isolation oxide layer, 160-Ground electrode disk. Detailed Implementation

[0062] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0063] In this article, the term "and / or" describes the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three cases: A exists alone, A and B exist simultaneously, and B exists alone. The symbol " / " in this article indicates that the related objects have an "or" relationship; for example, A / B means A or B.

[0064] The terms "first" and "second," etc., used in the specification and claims herein are used to distinguish different objects, not to describe a specific order of objects. For example, "first response message" and "second response message," etc., are used to distinguish different response messages, not to describe a specific order of response messages.

[0065] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0066] In the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more, for example, multiple processing units means two or more processing units, multiple elements means two or more elements, etc.

[0067] In the description of the embodiments of this application, unless otherwise stated, "several" means one or more, for example, several processing units means one or more processing units, and several elements means one or more elements.

[0068] To facilitate understanding of the solutions provided in the embodiments of this application, a brief introduction to some of the terms involved in this solution will be given first.

[0069] Thin-film piezoelectric on silicon (TPoS) is a novel type of resonator with a three-layer structure consisting of a metal electrode, a piezoelectric layer, and a substrate. The operating frequency of a TPoS resonator is determined by the interdigital electrode spacing, i.e., by photolithography, allowing for the design of resonators with multiple frequencies on the same wafer. Furthermore, the floating structure gives TPoS resonators a high quality factor. The aluminum nitride (AlN) process is compatible with traditional complementary metal-oxide-semiconductor (CMOS) processes, thus effectively overcoming limitations such as low quality factor, low resonant frequency, and integration difficulties. From an acoustic perspective, the lowest-order symmetric Lamb wave mode in AlN thin plates has a phase velocity close to 10,000 m / s, exhibiting excellent dispersion characteristics and a moderate electromechanical coupling coefficient.

[0070] Interdigitated electrodes are fingers-like or comb-like electrodes with periodic in-plane patterns. These electrodes are used to generate capacitance related to the electric field penetrating material samples and sensitive coatings. Micro-pitch interdigitated electrodes are one of the most commonly used micro-pitch electrode structures, widely applied in non-destructive testing, electronic communications, chemical testing, and many other fields. Generally, different applications have different requirements for the shape, geometry, fabrication process, material selection, modeling analysis, system integration, and data analysis of interdigitated electrodes; therefore, different applications should be treated differently. Several common interdigitated electrode structures include basic circular and rectangular shapes, and the shape of each interdigitate finger can be a simple rectangle or a circular or rectangular protrusion. Therefore, considering both response time and signal-to-noise ratio, it is necessary to design and optimize the thickness and aspect ratio of the interdigitated electrodes in the sensor. Interdigitated electrode sensors mainly include four structural parameters: the number of interdigitate electrode pairs, the interdigitate width, the gap distance between adjacent interdigitates, and the thickness of the interdigitated electrode. These four parameters have a significant impact on the key performance indicators of interdigitated electrode-based sensors.

[0071] Resonant pressure sensors can achieve resonance of the device structure through various excitation methods and obtain easily processed electrical parameters using a vibration pickup device to represent the resonant frequency. Resonant pressure sensors possess excellent performance characteristics such as high sensitivity, low power consumption, and direct frequency output. Among them, resonant pressure sensors based on piezoelectric mechanisms have attracted widespread attention from researchers due to their compatibility with Complementary Metal-Oxide-Semiconductor (CMOS) processes and wide operating range. The pressure sensor provided in this application is a novel resonant-based pressure sensor that achieves ultra-small size while maintaining high sensitivity, low power consumption, and simple fabrication. For example, the resonant pressure sensor can be a resonant pressure sensor based on the resonance principle applied to Micro-electro-mechanical Systems (MEMS). High-performance MEMS pressure sensors, characterized by small size, high sensitivity, low power consumption, and fast response speed, continue to receive significant attention from researchers.

[0072] Admittance is an important concept in electrical engineering, referring to the ratio of current to voltage response under a unit electromagnetic wave or electromagnetic induction excitation in an AC circuit. In AC circuits, admittance considers not only the resistive component but also the effects of inductance and capacitance. In power electronics, admittance is defined as the reciprocal of impedance, denoted by the symbol Y, and its unit is Siemens (S). Since the value of admittance is equal to the reciprocal of impedance, a larger admittance indicates a smaller impedance, and a smaller admittance indicates a larger impedance.

[0073] Quality Factor (Q-value): Also known as the Q-value, it is a quality indicator representing the ratio of energy stored in an energy storage device (such as an inductor or capacitor) to the energy lost per cycle in a resonant circuit. The Q-value reflects the ability of a device or circuit to store energy at a specific frequency and the magnitude of its losses. For inductors and capacitors, a higher Q-value means lower losses and higher efficiency during operation. In resonant circuits, a high Q-value means better selectivity and a narrower bandwidth for a specific frequency. The Q-value depends not only on the characteristics of the device itself but also on factors such as circuit design and operating frequency.

[0074] A pressure sensor is a sensor that can sense and measure the pressure applied to an object and convert it into an electrical signal. It has wide applications in aerospace, consumer electronics, automotive, healthcare, and other production and daily life sectors. For example, in recent years, pressure sensors have been widely used in wearable devices to detect pulse pressure wave information, providing important support for non-invasive monitoring of cardiovascular health. For tension-based blood pressure measurement and digital pulse diagnosis technology, the main challenge lies in the accurate location of arteries; inaccurate artery location can lead to inaccurate diagnostic information and inaccurate patient test results.

[0075] Therefore, a pressure sensor needs to be designed. For example, in the above exemplary scenario, the pressure data detected by the pressure sensor can accurately locate the position of the artery, thereby improving the effectiveness of diagnostic information and the accuracy of disease detection results.

[0076] In view of this, embodiments of this application provide a pressure sensor. The pressure sensor mainly includes a pressure-sensitive unit and an oscillation circuit. The oscillation circuit generates an excitation signal that causes the pressure-sensitive unit to resonate after signal amplification, phase shifting, and other processing. Driven by the excitation signal, the pressure-sensitive unit resonates; when external pressure is applied to the pressure-sensitive unit, the resonant frequency of the pressure-sensitive unit shifts, and the vibration pickup device detects the data indicating this shift in resonant frequency, thereby obtaining the value of the external pressure.

[0077] The technical solutions of this application will now be described in conjunction with the accompanying drawings. The detailed descriptions and drawings of the following embodiments are used to exemplarily illustrate the principles of this application, but should not be used to limit the scope of this application; that is, this application is not limited to the described embodiments. The technical solutions of the embodiments of this application will be described in detail below with specific examples. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Those skilled in the art will understand that with technological development and the emergence of new scenarios, the technical solutions provided by the embodiments of this application are also applicable to similar technical problems.

[0078] In a pressure sensor, the pressure-sensitive element is a key component. The technical solution for the pressure-sensitive element is described below as an example.

[0079] Figure 1a This is a top view schematic diagram of the pressure-sensitive unit provided in the embodiments of this application. Figure 1aAs shown, the pressure-sensitive unit 100 includes a substrate 110 and a piezoelectric resonator 120. The substrate 110 includes a cavity, and the piezoelectric resonator 120 is connected to the boundary of the cavity in the substrate 110. For example, the connection portion between the piezoelectric resonator 120 and the substrate 110 is as follows... Figure 1a As shown. The piezoelectric resonant part 120 includes a piezoelectric layer.

[0080] The resonance principle of the piezoelectric resonator 120 will be explained by way of example. Driven by an excitation signal, due to the inverse piezoelectric effect of the piezoelectric layer, the piezoelectric layer undergoes mechanical deformation, causing the entire piezoelectric resonator 120 to vibrate according to a specific mode. Simultaneously, charges generated by the piezoelectric layer through the piezoelectric effect are collected, and the polarity of the collected charges changes periodically over time, thereby obtaining the resonant frequency of the piezoelectric resonator. Wherein, Figure 1a The input electrode for the input excitation signal and the output electrode for the output signal generated by the piezoelectric effect are not shown; both are located on the upper surface of the piezoelectric layer.

[0081] Figure 1b This is a schematic diagram of the unloaded state of the pressure-sensitive unit provided in the embodiments of this application. Figure 1b The perspective is Figure 1a The sectional direction of the centerline. For example... Figure 1b As shown, under no-load conditions, the pressure-sensitive unit 100 does not deform. Under the drive of the excitation signal, the pressure-sensitive unit begins to resonate at the initial resonant frequency f0. During the resonance process, the substrate 110 does not move. The substrate 110 is used to fix the piezoelectric resonator 120 and ensure the mechanical properties of the piezoelectric resonator 120.

[0082] Figure 1c This is a schematic diagram of the load-bearing state of the pressure-sensitive unit provided in the embodiments of this application. Figure 1c perspective and Figure 1b The perspectives are the same. For example... Figure 1c As shown, when the load is pressure P, the pressure-sensitive unit 100 deforms, and the resonant frequency of the pressure-sensitive unit 100 changes to the resonant frequency f. Based on the difference between the resonant frequency f and the initial resonant frequency f0, the value of pressure P can be obtained after relevant processing.

[0083] The working principle of the pressure-sensitive unit is illustrated below.

[0084] In this embodiment, the pressure-sensitive unit 100 includes a piezoelectric resonator 120, which comprises a piezoelectric layer and a substrate. When an AC voltage is applied above the piezoelectric layer, surface acoustic waves (SAWs) are excited in the piezoelectric layer due to the inverse piezoelectric effect. The characteristic frequency of the SAW resonance is sensitive to the planar stress within the piezoelectric layer. Under applied external pressure, the piezoelectric layer bends, and its elastic modulus, density, and thickness all change, causing the phase velocity of the SAWs induced by the resonant motion to change accordingly.

[0085] Furthermore, the change in the elastic modulus of the piezoelectric layer 121 caused by external pressure plays a major role in the change of the resonant frequency of the surface acoustic wave. This can be understood as a functional relationship between the elastic modulus C and the external pressure P: C = C(P). Therefore, by differentiating the formula (1) for the phase velocity of the surface acoustic wave, formula (2) is obtained. Here, the elastic modulus is a concept of the effective elastic modulus in contact mechanics.

[0086] For example, the phase velocity of the sound wave V a The expression is shown in Equation (1). In Equation (1), C is the elastic modulus of the piezoelectric layer, and ρ is the density of the piezoelectric layer.

[0087]

[0088] For example, the relationship between the resonant frequency of the piezoelectric layer and the pressure is given by formula (2). In formula (2), P represents the external pressure, and the pressure P in the no-load state is 0. Δf represents the offset of the resonant frequency, such as the difference between the resonant frequency f and the initial resonant frequency f0 mentioned above.

[0089]

[0090] It can be further understood that, as shown in formula (2), the frequency response of the pressure sensor approximately exhibits a linear dependence on pressure. That is, when the external pressure varies within a certain range, the elastic modulus of the piezoelectric layer itself changes relatively little, and the pressure coefficient... This can be understood as a constant, and therefore the relationship between the resonant frequency of the piezoelectric layer and the pressure can be approximated as linear. Thus, the pressure value P can be deduced from the frequency change Δf.

[0091] In other examples, pressure coefficient This can also be understood as a variable that changes with pressure P. Through calibration, the relationship between the resonant frequency of the piezoelectric layer and the pressure is obtained. Then, the pressure value P can be deduced from the frequency change Δf. The calibration method refers to first obtaining the correspondence between pressure P and frequency change Δf through experiments, which is the calibration process; then, when actual pressure is applied, the actual pressure value can be obtained by combining the generated frequency change Δf with the calibrated data.

[0092] Figure 2a , Figure 2b , Figure 2c These are schematic diagrams showing the pressure-sensitive unit provided in this application from the front view, the first oblique view (back side of the substrate), and the second oblique view (front side of the substrate), respectively. Figure 2a , Figure 2b , Figure 2c As shown, this application embodiment provides a pressure-sensitive unit 100, which mainly includes a substrate 110 and a piezoelectric resonator 120.

[0093] Furthermore, the substrate 110 is provided with a cavity 111, and the piezoelectric resonator 120 can be suspended in the cavity 111. Figure 2b In the middle, the hollow area formed by the symmetrical first boundary 111-1 and the symmetrical second boundary 111-2 is the cavity 111.

[0094] Furthermore, the piezoelectric resonator 120 includes a piezoelectric layer 121 and a substrate 122. The piezoelectric layer 121 has a back surface 121-1, which is not shown. It is understood that the piezoelectric layer 121 also has a front surface 121-2, and the back surface 121-1 is the surface opposite to the front surface 121-2 in the piezoelectric layer 121.

[0095] Furthermore, the substrate 122 has a surface 122-1, a first connecting edge 122-2, and a second connecting edge 122-3.

[0096] For example, the piezoelectric layer 121 includes, but is not limited to, AlN, ZnO, PZT, PVDF, LiNbO3, LiTaO3 and other piezoelectric materials, with a thickness between 0.5 μm and 2 μm.

[0097] Furthermore, the back side 121-1 of the piezoelectric layer 121 is attached to the surface 122-1 of the substrate 122, the first connecting edge 122-2 is coupled to the first boundary 111-1, and the second connecting edge 122-3 is spaced apart from the second boundary 111-2, thereby the piezoelectric resonant part 120 is suspended in the cavity 111.

[0098] In this embodiment, the piezoelectric resonator 120 may include a fixed boundary (first connecting edge 122-2) and a free boundary (second connecting edge 122-3). The free boundary is the boundary in the piezoelectric resonator 120 that is not connected to the substrate 110. The fixed boundary is the boundary in the piezoelectric resonator 120 that is fixedly connected to the substrate 110. The fixed boundary and the free boundary can be implemented in any way, and this embodiment does not limit them.

[0099] For example, when the piezoelectric resonator 120 is fixed by two opposing first connecting edges 122-2, the vibration energy attenuates at the fixed boundary, resulting in significant energy loss and a low signal-to-noise ratio. To address this, this application proposes a multi-anchor point design; for instance, multiple through holes are added at the first connecting edge 122-2 on the fixed side to enhance signal strength and further improve sensor sensitivity.

[0100] In this embodiment, the piezoelectric resonator 120 is connected and fixed to the substrate 110 via the first connecting edge 122-2. The fixing method of the first connecting edge 122-2 in this embodiment offers higher mechanical stability, is less prone to damage, and is easier to process, resulting in lower manufacturing costs and design complexity. For example, the fixing method of the first connecting edge 122-2 in this embodiment is easier to process, allowing for the creation of small or ultra-small pressure-sensitive units 100 using photolithography and other processes, thus meeting the needs of complex pressure detection scenarios. The pressure-sensitive unit 100 also features high sensitivity. The piezoelectric resonator 120 is highly sensitive to pressure; different pressure levels cause varying degrees of shift in the resonant frequency of different resonant modes. While achieving a small size, the pressure-sensitive unit 100 requires very little driving current, thus also exhibiting low power consumption.

[0101] Optionally, the length of the first connecting edge 122-2 is greater than the length of the second connecting edge 122-3. Alternatively, the ratio of the length of the first connecting edge 122-2 to the length of the second connecting edge 122-3 can be set to a preset ratio.

[0102] For example, according to the simulation results, the length of the first connecting edge 122-2 is greater than the length of the second connecting edge 122-3. For example, when the ratio of the length of the first connecting edge 122-2 to the length of the second connecting edge 122-3 is a preset ratio (e.g., 2), the overall performance of the pressure sensitive unit 100 is better, and the balance of performance such as sensitivity, mechanical stability, and power consumption is better.

[0103] Optionally, the base 122 has a polygonal shape, and the first connecting edge 122-2 includes at least two opposite sides of the polygon, while the second connecting edge 122-3 is the side other than the first connecting edge 122-2. For example, as shown in FIG2, the base 122 has a quadrilateral shape, such as a rectangle, and the first connecting edge 122-2 is two opposite sides of the rectangle, while the second connecting edge 122-3 is another two opposite sides of the rectangle.

[0104] In other implementations, the base 122 is polygonal in shape, such as hexagonal or octagonal, which will not be elaborated further in this embodiment. The first connecting edge 122-2 includes at least two opposite edges of the polygon. While the pressure-sensitive unit 100 has high mechanical stability, it can also have symmetry, thus improving the overall performance of the pressure-sensitive unit 100.

[0105] For example, the input electrode of the piezoelectric resonator 120 can be as follows: Figure 2c The excitation electrode 123 shown can be, as shown, the output electrode can be as follows: Figure 2c The detection electrode 124 is shown. The excitation electrode 123 is attached to the front side 121-2 of the piezoelectric layer 121, and inputs an excitation signal to the piezoelectric layer 121. The detection electrode 124 is attached to the front side 121-2 of the piezoelectric layer 121, forming an interdigitated electrode structure with the excitation electrode 123. Based on the piezoelectric effect, the resonance of the piezoelectric resonator 120 generates an electrical signal, which is received by the detection electrode 124 and transmitted to the host computer.

[0106] Furthermore, the excitation electrode 123 is equivalent to the driving electrode, driving the resonant motion of the piezoelectric resonator 120. The detection electrode 124 is equivalent to the vibration pickup unit, detecting the electrical signal generated by the resonance. The detection electrode 124 and the excitation electrode 123 form an interdigitated electrode structure. The multi-interdigitated structure in the interdigitated electrode structure can effectively excite the vibration modes of the Lamb wave device, and has the characteristics of compact structure and suitability for miniaturization.

[0107] Optionally, the first connecting edge 122-2 is a boundary extending along a first direction in the substrate 122, where the first direction is the direction in which the interdigitated fingers extend longitudinally in the interdigitated electrode structure, such as... Figure 2c As shown. In other implementations, the first connecting edge 122-2 is the boundary extending along the second direction in the substrate 122, and the second direction is the direction in which the interdigitated electrodes are arranged laterally. According to simulation results, when the first connecting edge 122-2 extends along the first direction, the performance of the pressure-sensitive unit 100 is better, and the various performance characteristics of the pressure-sensitive unit 100 are further improved.

[0108] Optionally, the pressure-sensitive unit 100 further includes a first electrode disk 130, a second electrode disk 140, a first transmission line 125, and a second transmission line 126. For example... Figure 2cAs shown, the first electrode disk 130 and the second electrode disk 140 are respectively attached to the surface of the substrate 110. The first electrode disk 130 is used to receive the excitation signal input from the outside, and the second electrode disk 140 is used to output the electrical signal generated by the resonance of the piezoelectric resonator 120 to the outside. The first transmission line 125 and the second transmission line 126 are respectively attached to the surface 122-1 of the substrate 122. The two ends of the first transmission line 125 are electrically connected to the excitation electrode 123 and the first electrode disk 130, respectively, and the two ends of the second transmission line 126 are electrically connected to the detection electrode 124 and the second electrode disk 140, respectively.

[0109] In this embodiment, the electrode disk receives external signals; the transmission line transmits signals between the electrode and the electrode disk; the excitation electrode 123 drives the piezoelectric layer 121 to vibrate based on the inverse piezoelectric effect; and the detection electrode 124 picks up the electrical signals generated by the resonant deformation from the piezoelectric layer 121 based on the piezoelectric effect.

[0110] Optionally, the first transmission line 125 and the second transmission line 126 are respectively attached to the surface 122-1 of the substrate 122, which can match the structure of the piezoelectric resonator 120 and avoid the free boundary of the piezoelectric resonator 120, thereby realizing the electrical connection between each electrode and the electrode disk.

[0111] For example, the excitation electrode 123, the detection electrode 124, the first electrode disk 130, the second electrode disk 140, the first transmission line 125, and the second transmission line 126 are made of metals such as silver, copper, gold, aluminum, nickel, or lead, with a thickness between 0.5 μm and 2 μm.

[0112] Optionally, in order to effectively achieve electrical isolation between the transmission line, the electrode disk and the substrate 122, a first isolation oxide layer 150 is also provided between the transmission line and the substrate 122.

[0113] For example, a first isolation oxide layer 150 may be disposed between the first transmission line 125, the second transmission line 126, and the substrate 122; this portion of the first isolation oxide layer 150 corresponds to a part of the piezoelectric resonator 120. The first isolation oxide layer 150 may also be disposed between the first electrode disk 130, the second electrode disk 140, and the substrate 110; this portion of the first isolation oxide layer 150 corresponds to a part of the pressure-sensitive unit 100. For example, the material of the first isolation oxide layer 150 is silicon dioxide, and its thickness is between 0.3 μm and 1.5 μm.

[0114] Figure 3 This is a schematic diagram taken from an oblique angle of an embodiment of the present application. To further illustrate the structure of the piezoelectric resonator, combined with... Figure 3 ,right Figure 2a , Figure 2b , Figure 2cThe piezoelectric resonator 120 will be further explained. For example... Figure 3 As shown, in the piezoelectric resonant section 120, one or more of the first extension structures 122-2-1 of the first connecting edge 122-2 form multiple anchor points, and the multiple anchor points are fixedly connected to the first boundary 111-1.

[0115] For example, a plurality of first extension structures 122-2-1 in the first connecting edge 122-2 of the base 122 extend along a preset direction and are connected to the first boundary 111-1. The first extension structure 122-2-1 is a part of the first connecting edge 122-2, and the preset direction is perpendicular to the first connecting edge 122-2 and points to the first boundary.

[0116] In this embodiment, the first connecting edge 122-2 is fixed by multiple first extension structures 122-2-1. Compared to the method of fixing the entire first connecting edge 122-2, the connection of multiple first extension structures 122-2-1 in this implementation can reduce the loss of resonant energy and improve the signal-to-noise ratio of the detection signal.

[0117] Optionally, the number of first extension structures 122-2-1 is a preset number, which is related to the performance requirements of the pressure-sensitive unit 100. Optionally, the geometric dimensions of the first extension structure 122-2-1 are preset dimensions, which are related to the performance requirements of the pressure-sensitive unit 100.

[0118] For example, the number and geometric dimensions of the first extension structures 122-2-1 can be designed according to the performance requirements of the pressure-sensitive unit 100. For instance, by changing the number of the first extension structures 122-2-1, the pressure-sensing performance of the pressure-sensitive unit 100 can be adjusted. When the number of the first extension structures 122-2-1 is large, the same external pressure can cause the piezoelectric layer 121 to produce greater strain and deformation, thereby improving the pressure sensitivity of the pressure-sensitive unit 100. In other words, the sensitivity, stability, and power consumption of the pressure-sensitive unit 100 can be balanced by adjusting the number and dimensions of the first extension structures 122-2-1.

[0119] It should be noted that the sensor performance can be adjusted by changing the number of the first extension structures 122-2-1. Furthermore, a larger number of first extension structures 122-2-1 results in greater stress for the same pressure, leading to a greater change in the elastic modulus of the piezoelectric layer 121 and a larger deviation in the resonant frequency, thus improving the device's pressure sensitivity. However, a greater number of anchor points formed by the first extension structures 122-2-1 results in more acoustic energy leakage through the resonator, causing a decrease in the resonator's quality factor and a weaker resonant signal. This necessitates a higher-gain amplifier in the resonator circuit, increasing power consumption. In other words, the trade-off between pressure sensitivity and interface circuit power consumption can be balanced by adjusting the number and dimensions of the first extension structures 122-2-1.

[0120] Optionally, the pressure-sensitive unit 100 further includes: a plurality of ground electrode disks 160 attached to the substrate 110, wherein the plurality of ground electrode disks 160 are disposed on the outer side of the first electrode disk 130 and the outer side of the second electrode disk 140. One or more ground electrode disks 160 may be configured. For example, the plurality of ground electrode disks 160 disposed on both sides of the first electrode disk 130 and both sides of the second electrode disk 140 can form a GSG (Ground-Signal-Ground) electrode structure, which can effectively reduce signal transmission loss.

[0121] Figure 4 This is a schematic cross-sectional view of the transmission line location provided in an embodiment of this application. For example, using... Figure 2c Taking position A as an example, in the cross-sectional view of position A, the layers stacked in sequence are the second transmission line 126, the first isolation oxide layer 150, and the substrate 122. The first isolation oxide layer 150 can effectively achieve electrical isolation between the second transmission line 126 and the substrate 122.

[0122] Figure 5 This is a schematic cross-sectional view of the electrode positions provided in an embodiment of this application. For example, using... Figure 2c Taking position B as an example, in the cross-sectional view of position B, the layers are, in sequence, detection electrode 124, piezoelectric layer 121, and substrate 122.

[0123] Optionally, this application embodiment also provides a fabrication process for the pressure-sensitive unit 100. In the fabrication process of the pressure-sensitive unit 100, the structure of the pressure-sensitive unit 100 is relatively simple, and the fabrication of all structures can be achieved based on a single photolithography process, resulting in higher process reliability.

[0124] For example, the pressure-sensitive unit 100 is obtained by depositing a piezoelectric layer 121 on a wafer and then etching the wafer; wherein the substrate 110, the base 122, and the connection portion between the substrate 110 and the base are the retained portions after the wafer is etched. For example, the piezoelectric layer 121 is first deposited, and then photolithography and etching are performed on the piezoelectric layer 121; then an electrode layer is deposited, and then photolithography and etching are performed on the electrode layer. The electrode layer includes an input electrode and an output electrode; the input electrode includes an excitation electrode 123, a first transmission line 125, a first electrode disk 130, etc., and the input electrode is an integral structure; the output electrode includes a detection electrode 124, a second transmission line 126, a second electrode disk 140, etc., and the output electrode is an integral structure. After etching the electrode layer, the substrate 122 is photolithographically etched and etched to obtain a groove formed by the second connecting edge 122-3 and the second boundary 111-2 at intervals, and multiple first extension structures 122-2-1 of the first connecting edge 122-2 coupled to the groove formed by the first boundary 111-1, etc.; finally, the back of the substrate is photolithographically etched and etched to obtain a cavity 111 provided on the back of the substrate 110, so that the piezoelectric resonator 120 can be suspended in the cavity 111.

[0125] In one example, a silicon wafer is used as an example of a wafer. A silicon wafer is a common SOI (Silicon-on-Insulator) wafer, with a more mature fabrication process and easier miniaturization. The silicon wafer includes a doped silicon layer, a second isolating oxide layer, and a silicon substrate stacked sequentially. The second isolating oxide layer is disposed between the doped silicon layer and the substrate to achieve electrical isolation between them. After the silicon wafer is etched, the substrate 122 includes the remaining doped silicon layer, and the substrate 110 includes the doped silicon layer, the second isolating oxide layer, and the silicon substrate. The connection portion between the substrate 110 and the base includes the doped silicon layer. Specifically, by providing etch holes, the second connection edge is spaced apart from the second boundary; by providing etch holes, a plurality of first extension structures are spaced apart.

[0126] In this example, the piezoelectric sensing unit is fabricated using a piezoelectric thin film process on silicon-insulating (SOI) wafer. The fabrication process utilizes an SOI wafer as the substrate 110, an aluminum nitride thin film as the piezoelectric layer 121, and aluminum metal as the electrode. The multi-fingered structure effectively excites the vibration modes of the Lamb wave device. Its compact structure is suitable for miniaturization, and its relatively simple design allows for the fabrication of all structures in a single photolithography process, resulting in higher process reliability. The ground electrode is connected to the bulk silicon substrate, and both free boundaries and multiple fixed boundaries are designed to balance sensor performance.

[0127] In this example, a deep reactive ion etching process is used to etch the silicon substrate 110 so that the piezoelectric resonator 120 is suspended on the silicon substrate, thereby further improving the device's quality factor Q.

[0128] In this example, the piezoelectric resonator 120 is fixed to the substrate 110 through one or more first extension structures 122-2-1, achieving a relatively simple device structure while maintaining good mechanical stability. Employing a pressure-sensitive unit 100 based on piezoelectric mechanisms also reduces device fabrication costs and offers advantages such as high sensitivity, low power consumption, small size, easy compatibility with CMOS processes, and direct frequency output.

[0129] Figure 6 This is a schematic diagram of another piezoelectric sensing unit provided in an embodiment of this application. For example... Figure 6 Another piezoelectric sensing unit shown is, with Figures 2a-2c Compared to the piezoelectric sensing unit, the difference lies in the connection between the piezoelectric resonator 120 and the substrate 110; the rest of the structure is the same. For... Figures 2a-2c The structure is the same as that of the piezoelectric sensing unit, and will not be described in detail here.

[0130] like Figure 6 As shown, in another piezoelectric sensing unit, the first connecting edge 122-2 extends to the first boundary 111-1 as a single edge, forming a second extension structure 122-2-1′. Furthermore, the substrate 122 and the substrate 110 are connected via the second extension structure 122-2-1′, rather than via... Figures 2a-2c The first extension structure 122-2-1 is connected in an intermittent manner. The fixing method of the second extension structure 122-2-1′ has the characteristics of higher mechanical stability, less susceptibility to damage, easier processing, lower manufacturing cost and lower design complexity.

[0131] Figure 7 This is a schematic diagram of the piezoelectric resonator of another piezoelectric sensing unit provided in an embodiment of this application. To further illustrate the structure of the piezoelectric resonator of the other piezoelectric sensing unit, [the following is a description of the piezoelectric resonator]. Figure 7 ,right Figure 6 The piezoelectric resonator of another type of piezoelectric sensitive unit will be further explained. For example... Figure 7 As shown, in another piezoelectric sensing unit, the piezoelectric resonator 120 includes a piezoelectric layer 121 and a substrate 122. The piezoelectric layer 121 has a back surface 121-1 (not shown). The substrate 122 has a surface 122-1 (not shown), a first connecting edge 122-2, and a second connecting edge 122-3.

[0132] The first connecting edge 122-2 is a fixed boundary, and it is connected to the first boundary 111-1 through the second extension structure 122-2-1′. The second connecting edge 1226-3 is a free boundary, and it is spaced apart from the second boundary 111-2 to form a groove structure.

[0133] In this embodiment, the piezoelectric resonator 120 is connected and fixed to the substrate 110 through the second extension structure 122-2-1′, which has the characteristics of higher mechanical stability and less susceptibility to damage. It is also easier to process, with lower manufacturing costs and design complexity; for example, it eliminates the need to etch multiple holes to obtain the first extension structure 122-2-1. In other words, the fixing method of the first connecting edge 122-2 in this embodiment is easier to process, and small or ultra-small pressure-sensitive units can be obtained through processes such as photolithography, thereby meeting the requirements of complex pressure detection scenarios. Another pressure-sensitive unit also features high sensitivity. The piezoelectric resonator 120 is very sensitive to pressure; when subjected to different pressure levels, the resonant frequency of different resonant modes will shift to different degrees. This other pressure-sensitive unit achieves a small size while requiring very little driving current; therefore, the pressure-sensitive unit also features low power consumption.

[0134] Figure 8 This is a schematic diagram of another piezoelectric sensing unit provided in an embodiment of this application. Figure 8 Another type of piezoelectric sensing unit is shown, and Figure 6 Compared to the other piezoelectric sensing unit shown, the difference lies in the position of the first connecting edge 122-2 (fixed boundary); the rest are the same, and will not be repeated in the embodiments of this application.

[0135] Specifically, the first connecting edge 122-2 of the base 122 extends along a preset direction, resulting in the following: Figure 8 The third extension structure 122-2-1″ shown is connected to the first boundary 111-1, with a preset direction perpendicular to the first connecting edge 122-2 and pointing towards the first boundary. Figure 6 The other piezoelectric sensing unit shown is different in that the fixed boundary (i.e., the first connecting edge 122-2) of the piezoelectric sensing unit is in the direction where the interdigitated fingers point vertically, and the free boundary (i.e., the second connecting edge 122-3) is in the direction where the interdigitated fingers point parallel to each other.

[0136] For example, according to the simulation results, the first connecting edge 122-2 can be the boundary extending along the second direction in the substrate 122. That is, when the first connecting edge 122-2 is perpendicular to the interdigitated direction in the interdigitated electrode structure, the transmission line distance is shorter, the signal delay is lower, the structure is simpler, the processing cost is lower, and it can have the required sensitivity and mechanical strength.

[0137] To further illustrate the beneficial effects of the technical solutions in the embodiments of this application, related simulation results are also provided as examples. These simulation results are merely illustrative of the beneficial effects of the technical solutions in the embodiments of this application and do not constitute a limitation on the embodiments of this application. For example, the connection method when multiple first extension structures fix the piezoelectric resonator is discussed.

[0138] Figure 9 This is a schematic diagram showing the relationship between the resonant frequency and pressure of the pressure-sensitive unit when the connection structure between the substrate and the substrate provided in the embodiments of this application is different. Taking a rectangular piezoelectric resonator as an example, multiple first extension structures 122-2-1 are provided on two opposite connection sides, and the other two connection sides are spaced apart from the substrate, which is assumed to be pressure-sensitive unit a; multiple second extension structures 122-2-1′ are provided on two opposite connection sides, and the other two connection sides are spaced apart from the substrate, which is assumed to be pressure-sensitive unit b. For pressure-sensitive unit a, a simulation experiment was conducted, and the results are as follows: Figure 9 Curve 1 is shown; for pressure-sensitive unit b, a simulation experiment was conducted, and the results are as follows. Figure 10 Curve 2 is shown in the figure. (Curve 2 is not shown in the figure.)

[0139] It should be noted that, Figure 9 The horizontal axis in the graph represents the pressure generated by external pressure, in kPa; the vertical axis represents the frequency displacement (Hz), indicating the amount of frequency shift. The slope of the curve in the graph represents the shift in resonant frequency caused by a unit load, i.e., the sensitivity. For example, a higher slope indicates a greater shift in resonant frequency caused by a unit load. When determining the load based on the shift in resonant frequency, the load value is more accurate, meaning the sensor has higher sensitivity. In other words, the characteristic frequency of the pressure-sensitive unit 100 is sensitive to the planar stress within the piezoelectric film. Under applied external pressure, the piezoelectric layer 121 bends, and its elastic modulus, density, and thickness all change. The phase velocity of the Lamb wave caused by resonance changes accordingly, and its phase velocity is related to the elastic modulus and density of the piezoelectric layer 121. The change in the elastic modulus of the piezoelectric layer 121 caused by pressure has the greatest impact on the sensitivity of the pressure-sensitive unit 100.

[0140] For pressure-sensitive element a, the frequency response exhibits a linear dependence on pressure. For example, the slope of the curve corresponding to pressure-sensitive element a is 1.87 Hz / kPa; the slope of the curve corresponding to pressure-sensitive element b is 1.7 Hz / kPa (not shown). Simulation results show that the sensitivity of the pressure-sensitive element is higher when multiple first extension structures 122-2-1 are used.

[0141] Figure 10This is a schematic diagram showing the relationship between the resonant frequency and pressure of a pressure-sensitive unit with multiple first extension structures positioned differently, as provided in the embodiments of this application. Taking a rectangular piezoelectric resonator as an example, multiple first extension structures are arranged on the connecting edge parallel to the interdigitated electrode and spaced apart from the substrate on the connecting edge perpendicular to the interdigitated electrode; this is assumed to be pressure-sensitive unit c. Multiple first extension structures are also arranged on the connecting edge perpendicular to the interdigitated electrode and spaced apart from the substrate on the connecting edge parallel to the interdigitated electrode; this is assumed to be pressure-sensitive unit d. For pressure-sensitive unit c, simulation experiments were conducted, and the results are as follows... Figure 10 Curve 3 is shown; for the pressure-sensitive unit d, a simulation experiment was conducted, and the results are as follows. Figure 10 Curve 4 is shown.

[0142] It should be noted that, Figure 10 The horizontal axis represents the pressure generated by external force, in kPa; the vertical axis represents the frequency displacement (Hz), indicating the amount of frequency shift. The slope of the curve in the graph represents the shift in resonant frequency caused by a unit load, i.e., sensitivity. For example, a higher slope indicates a greater shift in resonant frequency caused by a unit load. When determining the load based on the shift in resonant frequency, the load value is more accurate, meaning the sensor has higher sensitivity.

[0143] For example, the slope of the curve corresponding to pressure-sensitive unit c is 3.15 Hz / kPa; the slope of the curve corresponding to pressure-sensitive unit c is 2.42 Hz / kPa. Simulation results show that when the connecting edges of multiple first extension structures are set parallel to the direction of the interdigitated electrodes, the sensitivity of the pressure-sensitive unit is higher.

[0144] Figure 11 This is a schematic diagram showing the relationship between the admittance and resonant frequency of the pressure-sensitive unit when the coupling method between the first connecting edge and the substrate is different according to the embodiments of this application. Taking a rectangular piezoelectric resonator as an example, multiple first extension structures 122-2-1 are provided on the first connecting edge, which serve as the coupling method between the first connecting edge and the substrate. The second connecting edge is spaced apart from the substrate, assuming it is pressure-sensitive unit e. Multiple second extension structures 122-2-1′ are provided on the first connecting edge, which serve as the coupling method between the first connecting edge and the substrate. The second connecting edge is spaced apart from the substrate, assuming it is pressure-sensitive unit f. For pressure-sensitive unit e, a simulation experiment was conducted, and the results are as follows: Figure 11 Curve 5 is shown; for the pressure-sensitive unit f, a simulation experiment was conducted, and the results are as follows. Figure 11 Curve 6 is shown.

[0145] It should be noted that since the admittance is equal to the reciprocal of the impedance, a larger admittance indicates a smaller impedance, and a smaller admittance indicates a larger impedance. Figure 11 The horizontal axis in the graph represents frequency in MHz; the vertical axis represents admittance in dB. Y21 represents the ratio of output current to input voltage. For example, the output current is the output current of the detection electrode 124, and the input voltage is the input voltage of the excitation electrode 123. The larger the extreme value of the curve in the graph, the larger the admittance, the smaller the impedance, and the greater the frequency selectivity of the piezoelectric sensing element. Regarding the frequency selectivity of the piezoelectric sensing element, generally, a piezoelectric sensing element has multiple resonant modes. The admittance is usually set with a threshold. Resonant modes in the piezoelectric sensing element whose admittance exceeds the threshold are usable. When the piezoelectric sensing element has multiple resonant modes (… Figure 11 (Only one resonant mode is shown). The larger the admittance, the more resonant modes the piezoelectric sensing element has, the greater the frequency selectivity of the piezoelectric sensing element, and the larger the Q value.

[0146] For example, in the absence of external pressure, the resonant frequency of pressure-sensitive units e and f is 276.37 MHz. Correspondingly, the extreme value of the curve for pressure-sensitive unit e is -46 dB, and the extreme value of the curve for pressure-sensitive unit f is -51 dB. Simulation results show that using multiple first extension structures (122-2-1) as the first connecting edge coupling method with the substrate results in greater frequency selectivity and a higher Q value for the piezoelectric sensing unit. In other words, by setting multiple first extension structures (122-2-1), the Q value of the sensor can be further improved, thus increasing the frequency selectivity of the sensing unit, allowing for more selectable modes, while simultaneously reducing sensor power consumption and improving sensitivity.

[0147] It should be noted that pressure-sensitive units a to f were obtained by setting different parameters. The parameters of the pressure-sensitive unit include electrode spacing, electrode width, number of electrodes, interdigital distance, and boundary width.

[0148] Figure 12 This is a schematic diagram illustrating the composition of a pressure sensor and sensor module provided in an embodiment of this application. Figure 12 As shown in the figure, this application embodiment provides a pressure sensor, including: the pressure-sensitive unit described above in this application embodiment.

[0149] Optionally, the pressure sensor also includes an oscillation circuit. The oscillation circuit is electrically connected to the pressure-sensitive unit. After processing the input signal, the oscillation circuit outputs an excitation signal, and the piezoelectric resonant section resonates under the action of the excitation signal. When external pressure is applied to the pressure sensor, the pressure sensor can output the pressure value. Under pressure, the piezoelectric layer of the pressure resonant section deforms, and the resonant frequency of the pressure resonant section changes. By acquiring easily processed electrical parameters through a vibration pickup device and performing relevant processing operations, the pressure value can be calculated.

[0150] For example, the oscillation circuit includes an amplification module and a phase shifter, etc., to amplify and phase-shift the electrical signal input from the power supply module, thereby obtaining a suitable excitation signal for the pressure-sensitive unit, so that the pressure-sensitive unit resonates at the corresponding frequency. The oscillation circuit can be implemented by any technical means, which will not be described in detail in the embodiments of this application.

[0151] like Figure 12 As shown in the figure, this application embodiment also provides a sensor module, including the pressure sensor described above.

[0152] Optionally, the sensor module also includes a power supply module. The power supply module provides an electrical signal to the pressure sensor to enable it to operate normally. For example, the power supply module can be a DC regulated power supply, providing voltage signals such as 2.5V or 5V. The power supply module can be implemented using any technical means, which will not be elaborated further in this embodiment.

[0153] Optionally, the sensor module further includes a processing module electrically connected to the pressure-sensitive unit in the pressure sensor, used to obtain the value of the external pressure based on the offset of the resonant frequency of the piezoelectric resonator.

[0154] Furthermore, under pressure, the pressure sensor deforms, and its resonant frequency changes. The processing module detects the current resonant frequency of the pressure sensor and calculates the pressure value based on the change in the resonant frequency. The processing module can be any device or apparatus that processes charge signals to obtain pressure values; that is, the processing module can be implemented using any technical means, which will not be elaborated further in this embodiment.

[0155] Optionally, the processing module includes a frequency counter, which can detect the resonant frequency corresponding to the pressure-sensitive unit when it resonates at a specific frequency. When the pressure-sensitive unit is subjected to pressure input, the resonant frequency shift is measured by the frequency counter and output to the host computer. For example, based on the charge at the resonant frequency f output by the pressure sensor, the frequency counter calculates the frequency calibration value of the resonant frequency f. Exemplarily, the processing module also includes a pressure conversion module, used to calculate the pressure value based on the current frequency calibration value of the resonant frequency f and the initial resonant frequency f0.

[0156] In this embodiment, the pressure sensor is an exemplary application scenario of a piezoelectric sensing unit. Taking the pressure sensor as an example, the pressure sensor in this embodiment reduces design complexity and manufacturing cost while ensuring small size, high sensitivity, and higher mechanical stability. For example, the pressure sensor in this embodiment is a MEMS-based TPOS pressure sensor, which is essentially a MEMS resonator. MEMS pressure sensors are highly sensitive to pressure; different pressure levels will cause varying degrees of shift in the resonant frequency of different resonant modes.

[0157] The pressure sensor described in this application can be used to implement standalone or array-type pressure sensors, applicable to applications such as tension-based blood pressure monitoring in wearable devices or digital TCM pulse pillows. For example, the pressure sensor is a TPoS sensor based on MEMS technology, featuring a fixed structure (the connection structure between the substrate and the base plate). It can be integrated into wearable devices, medical blood pressure monitoring systems, or TCM pulse pillow devices.

[0158] This application provides a resonant pressure sensor based on a fixed structure. Exemplary examples of resonant pressure sensors based on piezoelectric thin films on silicon can achieve high sensitivity and a high quality factor within a small size.

[0159] Optionally, the fixing structure can be a single-sided fully fixed structure, such as multiple second extension structures 122-2-1′, which maintains sensitivity while resulting in a smaller pressure sensor. The fixing structure can also be a multi-anchor structure, such as multiple first extension structures 122-2-1, which can further improve sensor sensitivity. The number of first extension structures 122-2-1 can be adjusted to balance performance requirements in different scenarios. By adjusting the size and number of the first extension structures 122-2-1, the sensor's sensitivity, stability, and power consumption can be balanced.

[0160] In this embodiment, the pressure sensor features high sensitivity and small size, making it suitable for pressure detection applications in industries and aerospace where high reliability is required. Furthermore, its extremely small size allows for applications such as high spatial resolution machine tactile sensing and health monitoring.

[0161] This application also provides an electronic device, which includes a device body and a pressure sensing device. The pressure sensing device is at least one of the aforementioned pressure-sensitive unit, pressure sensor, and sensor module. The electronic device can be any electronic device including the aforementioned pressure-sensitive unit, pressure sensor, and sensor module, such as mobile phones, watches, laptops, remote controls, etc., or wearable devices such as headphones, watches, bracelets, glasses, rings, etc., or blood pressure detection devices such as medical blood pressure monitoring devices and traditional Chinese medicine pulse pillow devices. Taking the medical field as an example, the electronic device can be a blood pressure monitoring device. The pressure sensor can be used to detect human pulse pressure wave information, providing important support for non-invasive monitoring of cardiovascular health; furthermore, the blood pressure data detected by the pressure sensor can accurately locate the position of arteries, thereby improving the effectiveness of diagnostic information and the accuracy of disease detection results.

[0162] The types, quantities, shapes, installation methods, and structures of components in the technical solutions provided in this application are not limited to the above embodiments. All technical solutions implemented under the principles of this application are within the protection scope of this application. Any one or more embodiments or illustrations in the specification, combined in a suitable manner, are within the protection scope of this application.

[0163] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application. Those skilled in the art should understand that although this application has been described in detail with reference to the foregoing embodiments, modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to depart from the spirit and scope of the technical solutions in the embodiments of this application.

Claims

1. A pressure-sensitive unit, characterized in that, include: A substrate having a recessed cavity, the recessed cavity having a first boundary and a second boundary; A piezoelectric resonant part includes a piezoelectric layer and a substrate. The substrate has a first connecting edge and a second connecting edge. The piezoelectric layer is attached to the surface of the substrate. The first connecting edge is fixedly connected to a first boundary. The second connecting edge is spaced apart from the second boundary. Under the action of the excitation signal, the piezoelectric resonant part resonates due to the inverse piezoelectric effect of the piezoelectric layer; when external pressure is applied to the piezoelectric resonant part, the piezoelectric layer deforms, and the resonant frequency of the piezoelectric resonant part shifts. The amount of the resonant frequency shift is used to determine the value of the external pressure.

2. The pressure-sensitive unit according to claim 1, characterized in that, The first connecting edge and the first boundary are fixedly connected by at least one first extension structure. The first extension structure is a structure in which the connecting segment of the first connecting edge extends to the first boundary in a preset direction. The connecting segment is a part of the boundary of the first connecting edge. The preset direction is a direction perpendicular to the first connecting edge and pointing to the first boundary.

3. The pressure-sensitive unit according to claim 2, characterized in that, The number of the first extension structures is a preset number, which is related to the performance requirements of the pressure-sensitive unit; and / or, the geometric dimensions of the first extension structure are preset dimensions, which are related to the performance requirements of the pressure-sensitive unit.

4. The pressure-sensitive unit according to claim 1, characterized in that, The first connecting edge and the first boundary are fixedly connected by a second extension structure. The second extension structure is a structure in which the first connecting edge extends to the first boundary along a preset direction. The preset direction is a direction perpendicular to the first connecting edge and pointing towards the first boundary.

5. The pressure-sensitive unit according to any one of claims 1-4, characterized in that, The offset of the resonant frequency of the piezoelectric resonator is linearly related to the external pressure.

6. The pressure-sensitive unit according to claim 5, characterized in that, The offset of the resonant frequency of the piezoelectric resonant part is equal to the product of the external pressure and the pressure coefficient, which is related to the elastic modulus of the piezoelectric layer.

7. The pressure-sensitive unit according to any one of claims 1-6, characterized in that, The length of the first connecting edge is greater than the length of the second connecting edge; and / or, the ratio of the length of the first connecting edge to the length of the second connecting edge is a preset ratio.

8. The pressure-sensitive unit according to any one of claims 1-7, characterized in that, The base has a polygonal shape, the first connecting edge includes at least two opposite sides of the polygon, and the second connecting edge is the side other than the first connecting edge.

9. The pressure-sensitive unit according to any one of claims 1-8, characterized in that, The piezoelectric layer has a front side, which is the side opposite to the back side of the piezoelectric layer, and the back side is the side of the piezoelectric layer that is attached to the substrate. The piezoelectric resonator further includes: An excitation electrode, attached to the front side of the piezoelectric layer, is used to load the excitation signal; The detection electrode is attached to the front side of the piezoelectric layer and forms an interdigitated electrode structure with the excitation electrode, for receiving the electrical signal generated by the resonance of the piezoelectric resonant part.

10. The pressure-sensitive unit according to claim 9, characterized in that, The first connecting edge is the boundary in the substrate that extends along a first direction, and the first direction is the direction parallel to the direction of the interdigitated electrode structure. Alternatively, the first connecting edge is a boundary in the substrate extending along a second direction, which is the direction perpendicular to the direction of the interdigitated electrode structure.

11. The pressure-sensitive unit according to claim 9 or 10, characterized in that, The pressure-sensitive unit further includes: The first electrode disk and the second electrode disk are respectively attached to the substrate. The first electrode disk is used to receive the excitation signal input from the outside, and the second electrode disk is used to output the electrical signal generated by the resonance of the piezoelectric resonator to the outside. The piezoelectric resonator further includes: A first transmission line and a second transmission line are respectively attached to the surface of the substrate. The two ends of the first transmission line are electrically connected to the excitation electrode and the first electrode disk, respectively, and the two ends of the second transmission line are electrically connected to the detection electrode and the second electrode disk, respectively.

12. The pressure-sensitive unit according to claim 11, characterized in that, Also includes: A first isolation oxide layer is disposed between the first transmission line, the second transmission line, and the substrate; And / or, disposed between the first electrode disk, the second electrode disk and the substrate.

13. The pressure-sensitive unit according to claim 11 or 12, characterized in that, The pressure-sensitive unit further includes: a plurality of grounding electrode disks attached to the substrate, wherein the plurality of grounding electrode disks are disposed outside the first electrode disk and outside the second electrode disk.

14. The pressure-sensitive unit according to any one of claims 1-13, characterized in that, The pressure-sensitive unit is obtained by depositing the piezoelectric layer on the wafer and etching the wafer; wherein the substrate, the base material, and the connection portion of the substrate and the base material are the retained portions after etching the wafer.

15. The pressure-sensitive unit according to claim 14, characterized in that, The wafer is a silicon wafer, which includes a doped silicon layer, a second isolation oxide layer, and a silicon substrate stacked sequentially. The second isolation oxide layer is disposed between the doped silicon layer and the silicon substrate. After the wafer is etched, the substrate includes the doped silicon layer, and the substrate includes the doped silicon layer, the second isolation oxide layer, and the silicon substrate. The connection portion between the substrate and the base includes the doped silicon layer.

16. A pressure sensor, characterized in that, include: The pressure-sensitive unit as described in any one of claims 1-15; An oscillation circuit is electrically connected to the pressure-sensitive unit. The oscillation circuit is used to output the excitation signal, and the piezoelectric resonant part of the pressure-sensitive unit resonates under the action of the excitation signal.

17. A sensor module, characterized in that, include: The pressure sensor as described in claim 16; The processing module is electrically connected to the pressure sensor and is used to obtain the value of the external pressure based on the offset of the resonant frequency of the pressure sensor.

18. An electronic device, characterized in that, It includes a main body and a pressure sensing device, wherein the pressure sensing device is at least one of the pressure sensitive unit as described in any one of claims 1-15, the pressure sensor as described in claim 16, and the sensor module as described in claim 17.

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