Resonant pressure sensor and system

Abstract

The embodiment of the present application provides a resonant pressure sensor and system, the resonant pressure sensor comprises a substrate, and a first resonator and a second resonator integrated on the substrate. The first resonator comprises a first base and a first piezoelectric layer, the first base is integrated on the substrate, and the first piezoelectric layer is arranged on the side of the first base away from the substrate. The second resonator comprises a second base and a second piezoelectric layer, the second base is integrated on the substrate, and the second piezoelectric layer is arranged on the side of the second base away from the substrate. The substrate has a first space and a second space arranged at intervals, the first base is suspended in the first space, and the outer circumferential side of the first base is fixedly connected to the substrate through a connecting portion and has a gap between the substrate. The second base is arranged in the second space, and the surface of the side of the second base away from the second piezoelectric layer is in contact with the substrate. The resonant pressure sensor provided by the embodiment of the present application can reduce the interference of the environmental temperature, and the measurement result is more accurate.

Description

Technical Field

[0001] This application relates to the field of sensors, and in particular to a resonant pressure sensor and system. Background Technology

[0002] A pressure sensor is a sensor that senses and measures pressure and converts it into an electrical signal output. It is widely used in railway transportation, intelligent buildings, aerospace, and healthcare, among other fields. MEMS (Microelectromechanical Systems) pressure sensors, with their advantages of small size, high accuracy, good stability, and ease of integration, have gradually replaced traditional pressure sensors, becoming one of the most widely used and fastest-growing sensors in the world today. MEMS pressure sensors can be classified into four types based on their sensing principle: piezoresistive, capacitive, fiber optic, and resonant. Piezoresistive pressure sensors are based on the piezoresistive effect of semiconductor materials. They convert the deformation of a diaphragm under external pressure into a change in resistance through a semiconductor resistance strain gauge, and then measure the pressure by detecting the change in resistance using methods such as a bridge circuit. They have low manufacturing costs and simple structures, but are sensitive to temperature changes and have poor environmental adaptability. Capacitive pressure sensors convert the external pressure acting on a moving electrode into a change in the sensor's capacitance to measure the pressure. They have advantages such as high dynamic response and high temperature stability, but also disadvantages such as difficulty in mass production and nonlinear output. Fiber optic pressure sensors measure pressure by detecting changes in the optical properties of fiber optics under external pressure. They have better temperature stability than piezoresistive pressure sensors and also have the advantages of high temperature resistance and strong electromagnetic interference resistance. However, they have higher production costs and more complex manufacturing and maintenance technologies.

[0003] Resonant pressure sensors measure pressure based on the characteristic that the resonant frequency of a resonant element changes with external pressure. Resonant elements come in various forms, such as beams, tuning forks, and diaphragms of various shapes. Furthermore, various excitation and pickup devices can be used to convert frequency changes into easily detectable and processed electrical signals, offering advantages such as high sensitivity and resolution, small size, low power consumption, and strong anti-interference capabilities. However, temperature is also a significant environmental factor affecting the performance of resonant elements. Temperature changes cause the resonant frequency of the element to shift, interfering with pressure detection. Therefore, reducing the negative impact of ambient temperature on resonant pressure sensors has become a crucial issue for researchers. To address this problem, researchers have proposed using a miniature heater to maintain a constant ambient temperature for the sensor. However, this method consumes a lot of power and is not suitable for pressure sensors that need to be in contact with the external environment. Other solutions have also been proposed, but none have been entirely effective in eliminating ambient temperature interference. Therefore, in existing technologies, ambient temperature significantly interferes with resonant pressure sensors, resulting in inaccurate measurement results. Summary of the Invention

[0004] The resonant pressure sensor and system provided in this application embodiment solve the problem that the ambient temperature has a large interference effect on the resonant pressure sensor in the prior art, resulting in inaccurate measurement results.

[0005] A first aspect of this application provides a resonant pressure sensor, including a substrate and a first resonator and a second resonator integrated on the substrate. The first resonator includes a first substrate and a first piezoelectric layer stacked sequentially, the first substrate being integrated into the substrate, and the first piezoelectric layer being disposed on the side of the first substrate away from the substrate. The second resonator includes a second substrate and a second piezoelectric layer stacked sequentially, the second substrate being integrated into the substrate, and the second piezoelectric layer being disposed on the side of the second substrate away from the substrate.

[0006] The substrate has a first space and a second space spaced apart. A first substrate is suspended in the first space, and the outer periphery of the first substrate is fixedly connected to the substrate by a connecting part, with a gap between them. A second substrate is disposed in the second space, and the surface of the second substrate facing away from the second piezoelectric layer is in contact with the substrate.

[0007] The resonant pressure sensor provided in this application includes a first resonator and a second resonator, both integrated on the same substrate, i.e., monolithic integration. The first resonator detects pressure, while the second resonator detects the effect of ambient temperature on the first resonator. Through signal modulation and calculation, this effect can be eliminated, resulting in an accurate pressure measurement. Furthermore, because the two resonators are monolithically integrated, the consistency of their ambient temperatures is ensured. The ambient temperature detection result of the second resonator can represent the true ambient temperature of the first resonator, ultimately leading to more accurate pressure data.

[0008] Specifically, both the first and second resonators include a substrate and a piezoelectric layer. The substrate is integrated on a base plate to support the piezoelectric layer. The piezoelectric layer is a resonant element whose resonant frequency changes with pressure and is affected by ambient temperature. The piezoelectric layer can be excited to vibrate by an excitation element, and the induced charge generated by this vibration can be detected. The polarity of the induced charge changes periodically over time, forming an output current. When the resonant pressure sensor is subjected to pressure, the pressure value can be calculated based on the output current of the resonator and the linear relationship between the resonant frequency of the piezoelectric layer and the applied pressure.

[0009] For the first resonator, its first substrate is suspended within a first space of the substrate. The first substrate and the substrate are connected by a connecting part, and there is a gap between the outer periphery of the first substrate and the substrate. Alternatively, it can be understood that the surface of the first substrate facing away from the first piezoelectric film does not contact the substrate, but is suspended only from the inner wall of the first space by the connecting part on its outer periphery. Thus, the first piezoelectric layer above the first substrate is also suspended above the first space, and the entire first resonator is suspended on the substrate, allowing it to vibrate freely. This structure reduces the acoustic impedance difference between the first piezoelectric layer and air, reducing energy dissipation and further improving the quality factor of the first resonator, making it more sensitive to pressure. Therefore, the first resonator can successfully complete pressure measurement.

[0010] For the second resonator, its second substrate is disposed in the second space, and the surface of the second substrate facing away from the second piezoelectric film is in contact with the substrate. Therefore, the second substrate and the second piezoelectric layer above it are restricted in their degrees of freedom. The entire second resonator cannot vibrate freely, so its sensitivity to external pressure is very low and can be almost ignored.

[0011] When pressure is applied to the resonant pressure sensor, it only affects the resonant frequency of the first resonator; the resonant frequency of the second resonator remains unchanged. Therefore, the resonant frequency of the second resonator is only affected by ambient temperature, while the resonant frequency of the first resonator is affected by both ambient temperature and pressure. By processing and calculating the output signals of both resonators, and compensating for the pressure data measured by the first resonator using the temperature data measured by the second resonator, an accurate pressure value can be obtained.

[0012] Therefore, the resonant pressure sensor provided in this application embodiment can reduce the interference of ambient temperature and make the measurement results more accurate.

[0013] In one possible implementation, the first space is configured as a perforated structure penetrating the substrate along its thickness direction. The second space is configured as a groove structure with a bottom, wherein the surface of the second substrate facing away from the second piezoelectric layer is in contact with the bottom of the second space, and the outer periphery of the second substrate is in contact with the substrate.

[0014] Using the above scheme, the first substrate of the first resonator is directly embedded in the substrate, and the bottom surface of the first substrate is not obstructed by the substrate at all, allowing the entire first resonator to have a large vibration space. The bottom surface of the second substrate is connected to the bottom of the second space without any gap between them. This restricts the degree of freedom of the second substrate in the thickness direction of the substrate, preventing it from vibrating. The second resonator has high vibration resistance and is therefore insensitive to pressure. Changes in external pressure have no effect on the resonant frequency of the second resonator, and its measured data is only used for temperature compensation. Connecting the outer periphery of the second substrate to the substrate further enhances the mechanical stability of the second substrate on the substrate, making the second resonator completely unable to vibrate and minimizing pressure sensitivity.

[0015] In one possible implementation, the connecting part is suspended in the first space, with one side of the connecting part connected to the inner wall of the first space and the other side connected to the outer peripheral surface of the first base.

[0016] With the above scheme, the connecting part forms a cantilever beam structure between the outer peripheral surface of the first substrate and the inner wall surface of the first space, so that the first substrate is suspended on the substrate, which is beneficial to the vibration of the first resonator.

[0017] In one possible implementation, the connecting portion includes a first connecting portion that extends from one end of the first base in the width direction to the other end, or the first connecting portion extends from one end of the first base in the length direction to the other end.

[0018] The extension direction of the first connecting part can be understood as the length direction of the side of the corresponding first substrate. The side is connected to the substrate through the first connecting part. The first connecting part is relatively long, which strengthens the connection between the first substrate and the substrate. It also has high mechanical strength during vibration, low risk of breakage and damage, and improves the reliability of the resonant pressure sensor.

[0019] In one possible implementation, the connecting portion includes a second connecting portion, the length of which is less than the length and width of the first base. The second connecting portion is shorter than any side of the first base, resulting in a weaker structure, lower mechanical strength, and easier bending and deformation during vibration of the first base, thus reducing vibration resistance.

[0020] In one possible implementation, there are multiple connecting parts, which are distributed circumferentially around the first substrate. There are also multiple gaps, distributed circumferentially around the first substrate, with one gap between adjacent connecting parts. When the excitation voltage is constant, the amplitude of vibration of the first resonator is related to the mechanical strength of the connecting parts. While ensuring reliable connection between the first substrate and the substrate, the more connecting parts there are, the smaller the size of each connecting part can be, resulting in lower mechanical strength and greater flexibility. This reduces the vibration resistance experienced by the first resonator, thereby improving the quality factor and increasing its sensitivity to external pressure. Therefore, using multiple connecting parts to fix the first substrate can improve the pressure sensitivity of the first resonator while ensuring reliable connection. The circumferential distribution of multiple first connecting parts around the first substrate is intended to balance the stress points on the first substrate and improve the consistency of vibration amplitude across different areas.

[0021] In one possible implementation, multiple connecting portions are distributed on both sides of the first base in its length direction and / or on both sides of the first base in its width direction. Multiple gaps are also distributed on both sides of the first base in its length direction and / or on both sides of the first base in its width direction. Distributing the connecting portions on opposite sides or around the first base avoids concentration of connecting portions, resulting in more uniform stress points on the first base, more stable vibration, and a more stable output signal.

[0022] In one possible implementation, multiple connecting parts are symmetrically distributed along the length and / or width of the first base. This symmetrical distribution of the connecting parts ensures a uniform distribution of stress points on opposite sides of the first base, resulting in more reliable mechanical strength during vibration and greater vibration stability.

[0023] In one possible implementation, when the connecting portion includes a first connecting portion, there are two first connecting portions; the two first connecting portions are disposed on both sides of the first base in the length direction of the first base, and each first connecting portion extends from one end to the other end in the width direction of the first base; or, the two first connecting portions are disposed on both sides of the first base in the width direction of the first base, and each first connecting portion extends from one end to the other end in the length direction of the first base.

[0024] By adopting the above scheme, a first connecting part is provided on each of the two opposite sides of the first base, so that the distribution of the first connecting parts is uniform and symmetrical, and the stress points of the first base are uniform.

[0025] In one possible implementation, when the connecting portion includes a second connecting portion, there are multiple second connecting portions; the multiple second connecting portions are distributed on both sides of the first base in its length direction and / or on both sides of the first base in its width direction, and at least two second connecting portions are spaced apart on the same side of the first base.

[0026] With the above scheme, second connecting parts are distributed on both opposite sides of the first base, making the distribution of the second connecting parts uniform and symmetrical, and the stress points of the first base are uniform. By providing multiple second connecting parts at intervals on the same side of the first base, the stress points on the same side of the first base can be distributed, preventing the second connecting parts from breaking or being damaged during vibration.

[0027] In one possible implementation, the cross-section of the connector in the thickness direction of the substrate is rectangular. The connector has a cuboid structure, and the gap between adjacent connectors is a square hole, which has a regular shape and is easy to process.

[0028] In one possible implementation, the first substrate, the connecting portion, and the portion of the substrate connected to the connecting portion are configured as an integral structure, and the second substrate and the portion of the substrate connected to the second substrate are configured as an integral structure. The first substrate, the second substrate, and the connecting portion can all be integrally formed on the substrate, greatly simplifying the structure and manufacturing process of the resonant pressure sensor.

[0029] In one possible implementation, the substrate is a silicon substrate and includes a doped silicon layer, an oxide isolation layer and an undoped silicon layer stacked sequentially. The first substrate, the interconnection portion and the second substrate are all located on the doped silicon layer and are integrated with the doped silicon layer.

[0030] The thickness of the first substrate and the thickness of the connector are both less than the thickness of the doped silicon layer. The surface of the first substrate facing the first piezoelectric layer and the surface of the connector facing the first piezoelectric layer are flush with the surface of the doped silicon layer facing the first piezoelectric layer.

[0031] Using the above scheme, the doped silicon layer can transmit and detect electrical signals, enhance the mechanical strength of the silicon substrate, and ensure the stability of the sensor under pressure. The high chemical stability of the oxide isolation layer can effectively isolate different electrodes or circuit components, preventing leakage and short circuits. The undoped silicon layer provides a mechanical support framework for the sensor, ensuring the overall structural stability of the sensor. The thinner thickness of the first substrate and the connection portion compared to the thickness of the doped silicon layer also weakens the mechanical strength, reducing the vibration resistance of the first resonator, improving the quality factor, and this structure is easy to manufacture.

[0032] In one possible implementation, the first substrate and the interconnect are formed on the substrate by an etching process. The etching process can remove material from a specific area of ​​the material surface to achieve the desired micro / nano structure. The processing method is simple, has few operation steps, and is conducive to mass production.

[0033] In one possible implementation, the first resonator further includes a first excitation element and a first detection element, which are disposed on the side of the first piezoelectric layer opposite to the first substrate. The second resonator further includes a second excitation element and a second detection element, which are disposed on the side of the second piezoelectric layer opposite to the second substrate.

[0034] The first piezoelectric layer and the second piezoelectric layer have the same shape and size, the first excitation element and the second excitation element have the same shape and size, the first detection element and the second detection element have the same shape and size, and the distance between the first excitation element and the first detection element and the distance between the second excitation element and the second detection element are the same.

[0035] In the above scheme, both the first and second resonators include excitation and detection elements, used to excite the piezoelectric layer vibration, detect the induced charge generated by the piezoelectric layer, and output a signal. By setting the first and second resonators to be completely identical, differing only in their mounting method on the substrate, this configuration allows for controllable variables, ensuring that the frequency-temperature characteristics of the first and second resonators are similar. This enables the reduction of the temperature impact on pressure sensing through frequency difference calculation, achieving a more effective temperature compensation function.

[0036] In one possible implementation, the first resonator further includes a first electrode assembly, which includes a first input electrode, a first output electrode, and a first interdigital electrode. The first input electrode and the first output electrode are disposed on a substrate, and the first interdigital electrode is disposed corresponding to the first piezoelectric layer.

[0037] The first interdigital electrode includes two first finger-like structures arranged opposite to each other. The two first finger-like structures are electrically connected to the first input electrode and the first output electrode respectively through a first transmission line. The first input electrode, the first transmission line and the first finger-like structure connected thereto constitute a first excitation element, and the first output electrode, the first transmission line and the first finger-like structure connected thereto constitute a first detection element.

[0038] The second resonator also includes a second electrode assembly, which includes a second input electrode, a second output electrode, and a second interdigital electrode. The second input electrode and the second output electrode are disposed on the substrate, and the second interdigital electrode is disposed corresponding to the second piezoelectric layer.

[0039] The second interdigital electrode includes two opposing second finger-like structures, which are electrically connected to the second input electrode and the second output electrode respectively via a second transmission line; wherein, the second input electrode, the second transmission line and the second finger-like structure connected thereto constitute a second excitation element, and the second output electrode, the second transmission line and the second finger-like structure connected thereto constitute a second detection element.

[0040] Using the above scheme, both resonators employ input voltage via input electrodes and output current signals via output electrodes to detect resonant frequency. Interdigitated electrodes are positioned on the side of the piezoelectric layer facing away from the substrate. Each interdigitated electrode has two finger-like structures (or comb-like structures), and the input and output electrodes are each connected to their respective finger-like structures via transmission lines. Interdigitated electrodes are finger-like or comb-like in-plane periodic patterned electrodes, which can increase the effective length and surface area of ​​the electrodes, improve the capacitance and electrochemical reaction rate between the electrodes, thereby enhancing the sensitivity of the resonant pressure sensor. The finger-like structure of the interdigitated electrodes also enhances the electric field strength, making the electric field distribution on the piezoelectric layer surface more uniform, which helps improve the performance consistency of the piezoelectric layer, reduces local stress concentration, and thus improves the performance and reliability of the piezoelectric layer.

[0041] In one possible implementation, a first isolation structure is provided between the first input electrode, the first output electrode, the first transmission line, and the substrate. A second isolation structure is provided between the second input electrode, the second output electrode, the second transmission line, and the substrate. Both the first and second isolation structures are insulators. The first and second isolation structures can isolate the signals from the electrodes and the transmission line, preventing signal leakage into the substrate.

[0042] In one possible implementation, both the first and second piezoelectric layers are piezoelectric thin films. Piezoelectric thin films can generate significant electrical signals under minute mechanical stress or pressure, enabling high-precision measurements. Furthermore, piezoelectric thin films are highly flexible and relatively thin, which is beneficial for the miniaturization of resonant pressure sensors and facilitates fabrication and mass production.

[0043] In one possible implementation, the temperature frequency coefficient of the first resonator differs from that of the second resonator by less than 1%, and the pressure sensitivity of the second resonator is less than 0.3 Hz / Kpa.

[0044] Using the above scheme, the temperature characteristics of the two resonators are the same or similar, the pressure frequency characteristic of the second resonator is extremely low, and the resonant pressure sensor can work normally and the measurement data is accurate.

[0045] In one possible implementation, there are one or more first resonators and one or more second resonators.

[0046] In one possible implementation, there are multiple first resonators and one or more second resonators, with each set of first and second resonators corresponding to the others. A corresponding set of first and second resonators constitutes a pressure detection component, and multiple pressure detection components are arranged in an array on the substrate.

[0047] By employing an array of multiple first resonators and multiple second resonators, a compact structure is achieved, enabling applications in high-density, high-spatial-resolution pressure detection scenarios. The alternating distribution of the first and second resonators enhances design flexibility and enables high-resolution multimodal detection.

[0048] In one possible implementation, the first resonator is a pressure-sensitive resonator used to measure pressure, exhibiting a highly sensitive response to pressure. The second resonator is a temperature-compensated resonator used to measure the resonant frequency variation caused by temperature.

[0049] The second aspect of this application provides a resonant pressure sensor system, including the resonant pressure sensor provided in any of the above embodiments, and further including a mixer and a filter. The mixer is used to mix the output signal of the first resonator with the output signal of the second resonator to output a mixed signal, and the filter is used to filter the mixed signal and output a pressure sensing signal.

[0050] The resonant pressure sensor system provided in this application embodiment uses a mixer circuit design to perform temperature compensation on the pressure sensing signal, which can achieve a more reliable pressure value output, and the output signal is relatively pure and of high quality. Attached Figure Description

[0051] Figure 1 This is a three-dimensional structural diagram of the resonant pressure sensor according to an embodiment of this application;

[0052] Figure 2 This is an exploded structural diagram of the resonant pressure sensor according to an embodiment of this application;

[0053] Figure 3for Figure 2 A magnified view of part B1 in the middle;

[0054] Figure 4 for Figure 2 A magnified view of part B2 in the middle;

[0055] Figure 5 This is a schematic diagram of the resonant pressure sensor system according to an embodiment of this application.

[0056] Figure 6 The curves showing the frequency shift of the first and second resonators in the resonant pressure sensor according to an embodiment of this application as a function of pressure are shown.

[0057] Figure 7 The curves showing the frequency shift of the first and second resonators in the resonant pressure sensor according to an embodiment of this application as a function of temperature are shown.

[0058] Figure 8 This is a top view schematic diagram of the resonant pressure sensor according to an embodiment of this application;

[0059] Figure 9 This is a bottom view schematic diagram of the resonant pressure sensor according to an embodiment of this application;

[0060] Figure 10a for Figure 8 A schematic diagram of the cross-sectional structure at position C1-C1;

[0061] Figure 10b This is a schematic cross-sectional view of another location of the first resonator in the resonant pressure sensor according to an embodiment of this application.

[0062] Figure 11 for Figure 8 A schematic diagram of the cross-sectional structure at position C2-C2;

[0063] Figures 12a to 12f This is a schematic diagram of the layout of the connection part in the resonant pressure sensor according to an embodiment of this application;

[0064] Figure 13 This is an exploded structural diagram of the first electrode assembly in the resonant pressure sensor according to an embodiment of this application;

[0065] Figure 14 This is an exploded structural diagram of the second electrode assembly in the resonant pressure sensor according to an embodiment of this application;

[0066] Figure 15 This is a schematic diagram of the layout of the first resonator and the second resonator in the resonant pressure sensor according to an embodiment of this application;

[0067] Figure 16This is a schematic diagram of another layout of the first resonator and the second resonator in the resonant pressure sensor of this application embodiment.

[0068] Explanation of reference numerals in the attached figures:

[0069] 100. Resonant pressure sensor;

[0070] 1. First resonator; 11. First substrate; 11a. Top surface; 11b. Bottom surface; 11c. Outer periphery;

[0071] 111. First side; 112. Second side; 113. Third side; 114. Fourth side;

[0072] 12. First piezoelectric layer; 13. First excitation element; 14. First detection element;

[0073] 15. First electrode assembly; 151. First input electrode; 152. First output electrode; 153. First interdigitated electrode; 1531. First finger structure; 154. First transmission line;

[0074] 2. Second resonator; 21. Second substrate; 21a. Top surface; 21b. Bottom surface; 21c. Outer periphery;

[0075] 22. Second piezoelectric layer; 23. Second excitation element; 24. Second detection element;

[0076] 25. Second electrode assembly; 251. Second input electrode; 252. Second output electrode; 253. Second interdigitated electrode; 2531. Second finger structure; 254. Second transmission line;

[0077] 3. Substrate; 31. First space; 31a. Inner wall surface; 32. Second space; 321. Bottom;

[0078] 33. Doped silicon layer; 34. Oxide isolation layer; 35. Undoped silicon layer;

[0079] 41. Connecting part; 411. First connecting part; 412. Second connecting part; 42. Gap;

[0080] 51. First isolation structure; 52. Second isolation structure; 53. First grounding electrode; 54. Second grounding electrode;

[0081] 200. Resonant pressure sensor system; 61. Mixer; 62. Filter;

[0082] 71. First phase shifter; 72. First amplifier; 81. Second phase shifter; 82. Second amplifier;

[0083] Z, the thickness direction of the substrate; X, the length direction of the first substrate; Y, the width direction of the first substrate. Detailed Implementation

[0084] To facilitate understanding, the following is an explanation of the technical terms used in this article:

[0085] Piezoelectric effect: When a piezoelectric material is subjected to an external force, polarization occurs within the material, generating opposite charges on its two surfaces. After the external force is removed, the material returns to its uncharged state. This effect can convert mechanical energy into electrical energy and is commonly used in sensors and energy harvesting devices.

[0086] Inverse piezoelectric effect: When an electric field is applied to a piezoelectric material, the material will undergo mechanical deformation, and the amount of deformation is proportional to the strength of the external electric field.

[0087] Resonant frequency: The resonant frequency is the frequency at which a system's response reaches its maximum value under the action of an external periodic force. At the resonant frequency, the system's impedance is at its minimum, and its energy transfer efficiency is at its highest. The resonant frequency is usually related to the system's mass, stiffness, and damping.

[0088] Characteristic frequency: The frequency of the vibration mode of a system during free vibration. The characteristic frequency is an inherent property of the system and is related to the system's geometry, material properties, and boundary conditions. The characteristic frequency is also called the natural frequency or natural frequency.

[0089] Elastic modulus: The ability of a material to resist deformation during the elastic deformation stage. It reflects the ease with which a material undergoes elastic deformation after being subjected to force.

[0090] Sound wave phase velocity: The speed at which the phase of a sound wave shifts as it propagates through a medium.

[0091] Acoustic impedance: Used to describe the resistance encountered by sound waves when they propagate through a medium. It reflects the medium's ability to absorb, reflect, and transmit sound waves, similar to the electrical impedance in a circuit.

[0092] Quality factor Q: 2π times the ratio of stored energy to energy lost in each cycle in a resonant system. A higher Q value indicates less energy loss and better resonant performance.

[0093] MEMS technology: Microelectromechanical Systems. A high-precision fabrication technology for manufacturing micro-mechanical and electronic components. It combines semiconductor manufacturing processes with microfabrication techniques, enabling the integration of mechanical components, sensors, actuators, and electronic circuits on silicon substrates, glass substrates, or organic materials.

[0094] CMOS technology: Complementary Metal Oxide Semiconductor. It integrates NMOS (N-type Metal Oxide Semiconductor) and PMOS (P-type Metal Oxide Semiconductor) devices on the same silicon substrate. The NMOS and PMOS transistors operate complementaryly in the circuit: when the input signal is high, the NMOS is on and the PMOS is off; when the input signal is low, the NMOS is off and the PMOS is on.

[0095] S0 mode: A symmetrical mode of the Lamb wave, its vibration direction is parallel to the propagation direction, belonging to the transverse vibration mode. It has a high group velocity during propagation and typically reaches the detection point faster than other modes. Furthermore, the S0 mode has low dispersion characteristics, maintaining a stable propagation speed over a wide frequency range. The S0 mode can be excited through specific electrode design and material selection. For example, using symmetrically arranged interdigitated electrodes on piezoelectric materials can effectively excite the S0 mode while suppressing interference from other modes.

[0096] Rayleigh mode: The propagation mode of Rayleigh waves in a resonator. Rayleigh waves are surface waves whose energy is concentrated primarily at the surface of the medium and decays exponentially with increasing depth.

[0097] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0098] Resonant pressure sensors measure pressure based on the characteristic that the resonant frequency of a resonant element changes with external pressure. Resonant elements come in various forms, such as beams, tuning forks, and diaphragms of various shapes. Furthermore, various excitation and pickup devices can be used to convert the resonant frequency change into an electrical signal that is easy to detect and process. They have advantages such as high sensitivity and resolution, small size, low power consumption, and strong anti-interference ability.

[0099] The core of a resonant pressure sensor is the resonator, an acoustic device that operates based on the piezoelectric and inverse piezoelectric effects. Its internal resonant element uses piezoelectric materials, such as piezoelectric thin films. Applying a voltage to the resonator causes the resonant element to undergo mechanical deformation under the inverse piezoelectric effect, driving the entire resonator to vibrate according to specific modes, thus converting electrical energy into mechanical energy. In a two-port resonator, two electromechanical transducers serve as its input and output ports. Applying a voltage to the output port drives the resonant element to vibrate, thus converting electrical energy into mechanical energy. The output port utilizes the direct piezoelectric effect to collect the induced charge generated by the resonant element under strain. The polarity of the induced charge changes periodically over time, eventually forming an output current. The input port for applying the voltage is also called the excitation device, and the output port for collecting the induced charge is also called the detection device.

[0100] The characteristic frequency of a resonant element is sensitive to the plane stress it is subjected to. When the resonant pressure sensor is subjected to external pressure, the resonant element and the excitation device are deformed under pressure. During the stretching process, the basic properties of the resonant element, such as mass, density, thickness and elastic modulus, change. The phase velocity Vp of the sound wave propagating in the sensor and the period λ of the excitation device will both change, which will ultimately manifest as a change in the resonant frequency of the resonant element.

[0101] The expression for the acoustic wave phase velocity Vp is:

[0102]

[0103] Where C is the elastic modulus of the resonant element, and ρ is the density of the resonant element.

[0104] Since the change in the elastic modulus of the resonant element caused by pressure has the greatest impact on the sensitivity of the sensor, the expression for the resonant frequency f of the resonator with respect to the pressure P is:

[0105]

[0106] According to the above formula, the resonant frequency response of the resonator exhibits a linear shift with respect to pressure P. Utilizing this characteristic, the magnitude of the external pressure can be determined simply by measuring the change in the resonant frequency. By analyzing the output current of the resonator, the pressure value can be calculated based on the linear relationship between its resonant frequency and the applied pressure.

[0107] However, temperature is also a significant environmental factor affecting resonator performance. The thermal expansion coefficients of the different layers of materials constituting the resonator differ. When the temperature changes, the thermal mismatch between these layers generates thermal stress, causing a shift in the resonant frequency. Temperature changes can cause a shift in the resonant frequency, interfering with pressure detection. Therefore, reducing the negative impact of ambient temperature on resonant pressure sensors has become a crucial issue for researchers.

[0108] To address this issue, researchers have proposed using miniature heaters to maintain a constant ambient temperature for the sensor. However, this method consumes significant power and is not suitable for contact pressure sensors (i.e., pressure sensors that need to contact external objects). Researchers have also proposed other solutions, but none are entirely effective in eliminating ambient temperature interference. For example, one technique uses a temperature sensor to detect the external temperature and then uses the output data from the temperature sensor to compensate for the pressure sensor signal at a digital or analog level. However, such a detection system increases complexity, requires complex manufacturing processes, and has a relatively large size. Furthermore, since the temperature and pressure sensors are on different chips, when there is a large gradient in ambient temperature, the temperature sensor cannot reflect the true temperature of the environment in which the pressure sensor is located, resulting in measurement inaccuracies. Other techniques, while improving the accuracy of pressure measurements to some extent, are structurally complex, difficult to debug, and unsuitable for contact pressure sensing; they can only be used to measure air pressure.

[0109] Therefore, in the existing technology, ambient temperature has a significant impact on resonant pressure sensors, resulting in inaccurate measurement results.

[0110] To address the aforementioned issues, this application provides a resonant pressure sensor that integrates two resonators onto a single chip. Through a special structural design, one resonator is sensitive to both external pressure and ambient temperature, while the other is only sensitive to ambient temperature. Temperature compensation is applied to the signal from the other resonator using the temperature-sensitive resonator, significantly suppressing interference from ambient temperature on pressure measurement. This structure not only solves the problem of significant interference from ambient temperature in resonant pressure sensors but also offers advantages such as high pressure sensitivity, compact size, low cost, and suitability for mass production, making it a promising candidate for widespread applications.

[0111] The resonant pressure sensor provided in this application embodiment can realize contact pressure measurement, including but not limited to medical blood pressure monitoring, tension blood pressure detection in wearable devices, robotic tactile sensing, digital TCM pulse pillow, independent or array-type pressure measurement, etc. The basic structure and working principle of the resonant pressure sensor in this application embodiment are described below with reference to the accompanying drawings.

[0112] Please see Figures 1 to 4 , Figure 1 This is a three-dimensional structural diagram of the resonant pressure sensor according to an embodiment of this application; Figure 2 This is an exploded structural diagram of the resonant pressure sensor according to an embodiment of this application; Figure 3 for Figure 2 A magnified view of part B1 in the middle; Figure 4 for Figure 2 A magnified view of part B2 in the middle.

[0113] like Figure 1 , Figure 2 As shown, the resonant pressure sensor 100 includes a substrate 3, and a first resonator 1 and a second resonator 2 integrated on the substrate 3. Alternatively, it can be understood that the first resonator 1 and the second resonator 2 are integrated on the same substrate 3, i.e., monolithic integration. Wherein, as... Figure 3 As shown, the first resonator 1 includes a first substrate 11 and a first piezoelectric layer 12 stacked sequentially. The first substrate 11 is integrated into the substrate 3, and the first piezoelectric layer 12 is disposed on the side of the first substrate 11 away from the substrate 3. Figure 4 As shown, the second resonator 2 includes a second substrate 21 and a second piezoelectric layer 22 stacked sequentially. The second substrate 21 is integrated into the substrate 3, and the second piezoelectric layer 22 is disposed on the side of the second substrate 21 away from the substrate 3.

[0114] like Figures 2 to 4 As shown, the substrate 3 has a first space 31 and a second space 32 spaced apart. The first substrate 11 is suspended in the first space 31, and the outer peripheral side 11c of the first substrate 11 is fixedly connected to the substrate 3 through a connecting part 41, with a gap 42 between them. The connecting part 41 can also be understood as an anchor point, meaning that the first substrate 11, together with the first piezoelectric layer 12, is suspended on the substrate 3 by anchoring. The second substrate 21 is disposed in the second space 32, and the surface of the second substrate 21 facing away from the second piezoelectric layer 22 (i.e., Figure 11The bottom surface 21b) of the substrate is in contact with the substrate 3. It should be noted that the second substrate 21 shown in the accompanying drawings completely fills the second space 32, and the second substrate 21 and the substrate 3 are an integral structure with no clear boundary line between them. Therefore, the second space 32 does not actually exist; the dashed line drawn in the figure is an imaginary boundary line between the second substrate 21 and the substrate 3, and the space where the second substrate 21 is located is the second space 32. The resonant pressure sensor 100 provided in this embodiment includes a first resonator 1 and a second resonator 2, both integrated on the same substrate 3, i.e., monolithic integration. The first resonator 1 can be used to detect pressure, and the second resonator 2 can be used to detect the influence of ambient temperature on the first resonator 1. Through signal modulation and calculation, this influence can be eliminated, resulting in an accurate pressure measurement result. Furthermore, since the two resonators are monolithically integrated, the consistency of the ambient temperature of the two is ensured. The result of the second resonator 2 detecting the ambient temperature can represent the true ambient temperature of the first resonator 1, and the final detected pressure data is more accurate.

[0115] Specifically, both the first resonator 1 and the second resonator 2 include a substrate and a piezoelectric layer. The substrate is integrated on the substrate 3 to support the piezoelectric layer. The piezoelectric layer is a resonant element made of piezoelectric material, and its resonant frequency changes with pressure and is affected by ambient temperature. The piezoelectric layer can be excited to vibrate by an excitation device, causing the entire resonator, including the substrate, to vibrate together. The induced charge generated by the vibration of the piezoelectric layer is detected; the polarity of the induced charge changes periodically over time, forming an output current. When the resonant pressure sensor 100 is subjected to pressure, the pressure value can be calculated based on the output current of the resonator and the linear relationship between the resonant frequency of the piezoelectric layer and the applied pressure.

[0116] For the first resonator 1, its first substrate 11 is suspended within the first space 31 of the substrate 3. The first substrate 11 and the substrate 3 are connected by a connecting portion 41, and there is a gap 42 between the outer peripheral side 11c of the first substrate 11 and the substrate 3. Alternatively, it can be understood that the surface of the first substrate 11 facing away from the first piezoelectric film (i.e., the surface facing away from the first piezoelectric film) Figure 10aThe bottom surface 11b) of the first resonator 1 does not contact the substrate 3, but is suspended from the inner wall surface 31a of the first space 31 only through the connecting portion 41 on its outer peripheral side 11c. Thus, the first piezoelectric layer 12 above the first substrate 11 is also suspended above the first space 31, and the entire first resonator 1 is suspended on the substrate 3, allowing it to vibrate freely. This structure reduces the acoustic impedance difference between the first piezoelectric layer 12 and air, reducing energy dissipation and further improving the quality factor Q of the first resonator 1. The quality factor Q reflects the energy storage and loss characteristics of the resonator at a specific frequency; a higher Q value indicates lower energy loss and better resonance performance. The structure of the first resonator 1 suspended on the substrate 3 reduces the vibration resistance of the entire resonant system, resulting in less loss, a higher quality factor Q, and greater sensitivity to pressure. Therefore, the first resonator 1 can successfully complete pressure measurement.

[0117] For the second resonator 2, its second substrate 21 is disposed in the second space 32. The surface of the second substrate 21 facing away from the second piezoelectric film is in contact with the substrate 3. Therefore, the second substrate 21 and the second piezoelectric layer 22 above it are restricted in their degrees of freedom. The entire second resonator 2 cannot vibrate freely, so its sensitivity to external pressure is very low and can be almost ignored.

[0118] When pressure is applied to the resonant pressure sensor 100, it only affects the resonant frequency of the first resonator 1 (since the entire first resonator 1 vibrates together under the drive of the first piezoelectric layer 12, the resonant frequency of the first resonator 1 can also be understood as the resonant frequency of the first piezoelectric layer 12). The resonant frequency of the second resonator 2 (which can be understood as the resonant frequency of the second piezoelectric layer 22) does not change with pressure. Therefore, the change in the resonant frequency of the second resonator 2 is only affected by the ambient temperature, while the change in the resonant frequency of the first resonator 1 is affected by both the ambient temperature and the pressure. By processing and calculating the output signals of the two resonators, and compensating for the pressure data measured by the first resonator 1 using the temperature data measured by the second resonator 2, an accurate pressure value can be obtained.

[0119] Therefore, the resonant pressure sensor 100 provided in this application embodiment can reduce the interference of ambient temperature and make the measurement results more accurate.

[0120] Furthermore, the resonant pressure sensor 100 provided in this application embodiment has numerous advantages:

[0121] Firstly, the resonant pressure sensor 100 mainly relies on the first resonator 1 to measure pressure. The first resonator 1 is set as a suspension structure, which has low vibration resistance, high quality factor, and extremely sensitive response to pressure. It has a wide pressure measurement range and good output linearity.

[0122] Secondly, this monolithic integrated structure has high compactness, which can reduce the size of the resonant pressure sensor 100 and simplify the manufacturing process.

[0123] Third, the temperature data has a good compensation effect on the pressure data, which can effectively improve the accuracy of the resonant pressure sensor 100 in complex environments.

[0124] Fourth, it can be applied to contact pressure measurement scenarios. The temperature change when in contact with an object is also within the monitoring range of the second resonator 2, thus suppressing the influence of the external object temperature on the sensor measurement results.

[0125] Fifth, due to the highly integrated structure of the sensor, it can be made smaller and more precise, making it suitable for use in a variety of complex detection environments and enabling high-resolution detection in complex spaces.

[0126] Sixth, its working principle is based on piezoelectric energy conversion to achieve the mutual conversion of mechanical energy and electrical energy, and it can work normally in an atmospheric environment without the need for additional vacuum packaging. Seventh, it has a simple structure and can be compatible with various processes in production and preparation, such as MEMS process, CMOS process, photolithography process, etc., which makes it easy to carry out large-scale mass production and preparation with low manufacturing cost.

[0127] In summary, the resonant pressure sensor 100 provided in this application embodiment avoids the impact of temperature changes on the normal operation of the device, while also having a relatively simple device structure design, and taking into account the advantages of small size, high sensitivity, good output stability, high process compatibility, and wide applicability.

[0128] Please see Figures 5 to 7 , Figure 5 This is a schematic diagram of the resonant pressure sensor system according to an embodiment of this application. Figure 6 The curves showing the frequency shift of the first and second resonators in the resonant pressure sensor according to an embodiment of this application as a function of pressure are shown. Figure 7 The curves show the frequency shift of the first and second resonators in the resonant pressure sensor of this application as a function of temperature.

[0129] like Figure 5As shown in the illustration, this application also provides a resonant pressure sensor system 200, which includes a resonant pressure sensor 100, a mixer 61, and a filter 62. The mixer 61 mixes the output signal of the first resonator 1 with the output signal of the second resonator 2 to output a mixed signal. Through the design of the mixer circuit, temperature compensation of the pressure sensing signal can be achieved at the hardware level, resulting in a more reliable pressure value output. The filter 62 filters the mixed signal and outputs the pressure sensing signal. Those skilled in the art will understand that the mixer 61 generally outputs a signal in a specific frequency band, but it inevitably contains some signal impurities from other frequency bands. The filter 62 can remove these impurities. For example, the mixer 61 can be designed to output a low-frequency signal, and then a low-pass filter 62 can be used to remove high-frequency impurities, resulting in a purer and higher-quality final output signal.

[0130] like Figure 5 As shown, in one possible implementation, the resonant pressure sensor system 200 may further include a phase shifter and an amplifier. The first phase shifter 71 and the first amplifier 72 are connected to the first resonator 1 to form a sub-circuit system, which modulates and optimizes the output current of the first resonator 1 to output a signal that meets the requirements. The first phase shifter 71 can adjust the phase to form an oscillating loop, and the first amplifier 72 can amplify the signal to output a stable signal. Similarly, the second phase shifter 81 and the second amplifier 82 are connected to the second resonator 2 to form a sub-circuit system, which modulates and optimizes the output current of the second resonator 2 to output a signal that meets the requirements.

[0131] It should be noted that the connection method of the phase shifter, amplifier, and resonator in each subsystem is not limited; they can be connected in parallel or in parallel configurations, etc. The attached diagram is only a schematic diagram, and the specific circuit design should be set according to actual needs. The resonant pressure sensor system 200 may also include more or fewer components than shown in the figure, and this application embodiment does not impose any limitations on this.

[0132] It should be noted that this application does not limit the specific calculation scheme for the final output signal of the resonant pressure sensor system 200. In one possible implementation, the difference between the output signals of the two resonators can be directly calculated to reflect the pressure detection value. For example, the output signal of the first resonator 1 is f1, which is a sinusoidal oscillation signal generated by a closed-loop oscillation circuit composed of the first resonator 1, the first phase shifter 71, and the first amplifier 72. The output signal of the second resonator 2 is f2, which is a sinusoidal oscillation signal generated by a closed-loop oscillation circuit composed of the second resonator 2, the second phase shifter 81, and the second amplifier 82. f1 and f2 are mixed in the mixer 61, and after a series of modulations and processing, the final output pressure sensing signal f is obtained. B fB =f1-f2. This direct difference method is relatively simple, which can simplify the data processing and reduce the amount of calculation, but it also has certain requirements on the pressure frequency characteristics and temperature frequency characteristics of the two resonators.

[0133] In one possible implementation, the two resonators have similar or identical temperature characteristics, while the second resonator (2) exhibits extremely low pressure-frequency characteristics. The temperature-frequency characteristics of a resonator refer to the way its resonant frequency changes with ambient temperature, which can be evaluated using the Temperature Coefficient of Frequency (TCF). TCF is a parameter describing the thermal stability of a resonator, reflecting the degree of frequency drift of a material or device when its temperature changes. It is typically expressed as the average rate of change of the resonant frequency of an object for every 1°C change in temperature within a specific temperature range. The pressure-frequency characteristics of a resonator refer to the way its resonant frequency changes with external pressure, and are usually a linear relationship.

[0134] The statement "The temperature characteristics of the two resonators are the same or similar, and the pressure frequency characteristic of the second resonator 2 is extremely low" can be understood as follows: The second resonator 2, due to its limited degrees of freedom, cannot vibrate and its response to external pressure is very small, even negligible. However, the frequency responses of the two resonators to ambient temperature are very similar. Therefore, the coupling between temperature and pressure can be avoided by performing differential mixing on the output signals of the two resonators. Mixing the output signals of the two resonators removes the influence of temperature on the pressure measurement data while ensuring that the pressure sensitivity of the resonant pressure sensor 100 meets the requirements. Furthermore, the very close resonant frequencies of the two resonators when there is no pressure also reduce the difficulty of the subsequent mixing process.

[0135] In this designation, the first resonator 1 can be understood as a pressure-sensitive resonator, and the second resonator 2 as a temperature-compensated resonator. It's important to note that this naming convention is based on the primary functions of the two resonators and does not imply that the resonators can only respond to temperature or only to pressure. For example, the first resonator 1 is a pressure-sensitive resonator because its primary function is to measure pressure, making it highly sensitive to pressure. However, changes in ambient temperature also affect the resonant frequency of the first resonator 1. The second resonator 2 is a temperature-compensated resonator because its primary function is to measure the resonant frequency variation caused by temperature. The second resonator 2 can respond to temperature changes, but this does not mean that its resonant frequency is unaffected by pressure; rather, the influence of pressure on it is extremely low, negligible.

[0136] One possible implementation is, such as Figure 6As shown, the resonant frequency of the first resonator 1 when not under external pressure is 410.82 MHz (S0 mode), and A1 is its frequency shift curve as a function of pressure. The resonant frequency of the second resonator 2 when not under external pressure is 407.86 MHz (Rayleigh mode), and A2 is its frequency shift curve as a function of pressure. The slope of A1 characterizes the pressure sensitivity of the first resonator 1, which is 24.53 Hz / kPa in the figure. The slope of A3 characterizes the pressure sensitivity of the second resonator 2, which is 0.28 Hz / kPa in the figure. The pressure sensitivity of the second resonator 2 is much lower than that of the first resonator 1 and can be ignored, while the first resonator 1 can measure pressure normally.

[0137] like Figure 7 As shown, A3 is the frequency shift curve of the resonant frequency of the first resonator 1 as a function of pressure. The slope of A3 characterizes the temperature sensitivity of the first resonator 1, i.e., the temperature frequency coefficient (TCF). A4 is the frequency shift curve of the resonant frequency of the second resonator 2 as a function of pressure. The slope of A4 characterizes the temperature sensitivity of the second resonator 2. The TCF of the first resonator 1 is -1294 Hz / ℃, and the TCF of the second resonator 2 is -1286 Hz / ℃. These two values ​​are very close, and A3 and A4 almost overlap. Therefore, the temperature characteristics of the first resonator 1 and the second resonator 2 are similar.

[0138] Figure 6 and Figure 7 The first resonator 1 and the second resonator 2 in the above embodiments meet the condition that "the temperature characteristics of the two resonators are the same or similar, and the pressure frequency characteristic of the second resonator 2 is extremely low". The designed resonant pressure sensor 100 meets the requirements and can compensate for the pressure measurement data by the difference of the mixed signal, and the measurement result is accurate.

[0139] Those skilled in the art will understand that, ideally, the resonant pressure sensor 100 of this application should be designed such that the temperature characteristics of the two resonators are exactly the same (i.e., Figure 7 (A3 and A4 overlap), the pressure sensitivity of the second resonator 2 is 0 (i.e. Figure 6 (The slope of A2 is 0). However, the pressure frequency characteristics and temperature frequency characteristics of the resonator are related to the structure, material, and size of each part of the resonator. Errors in the manufacturing process will cause the final frequency characteristics of the resonator to deviate from the ideal situation, but slight deviations will not have a significant impact on the accuracy of the sensor's measurement results.

[0140] In one possible implementation, the temperature frequency coefficient of the first resonator 1 differs from that of the second resonator 2 by less than 1%, and the pressure sensitivity of the second resonator 2 is less than 0.3 Hz / Kpa. In this case, it can be considered that "the temperature characteristics of the two resonators are the same or similar, and the pressure frequency characteristic of the second resonator 2 is extremely low". The resonant pressure sensor 100 can work normally and the measurement data is accurate.

[0141] The difference between the temperature frequency coefficient of the first resonator 1 and the temperature frequency coefficient of the second resonator 2 can be calculated as a percentage of the absolute values ​​of the two parameters. The calculation method is to select one of the absolute values ​​of the two parameters as a reference value, and the percentage difference = (larger absolute value - smaller absolute value) / reference value × 100%. The reference value can be either the larger or smaller absolute value of the two parameters, and this application embodiment does not limit this.

[0142] by Figure 7 Taking two resonators as an example, the temperature frequency coefficient (TCF) of the first resonator 1 is -1294 Hz / ℃, with an absolute value of 1294. The temperature frequency coefficient (TCF) of the second resonator 2 is -1286 Hz / ℃, with an absolute value of 1286. Calculating the percentage difference between 1294 and 1286, and selecting 1294 as the reference value, the percentage difference is calculated as: (1294 - 1286) / (1294) × 100% = 0.617%. Since 0.617% is less than 1%, the condition is met. Furthermore, Figure 6 The pressure sensitivity of the second resonator 2 is 0.28 Hz / Kpa, which is less than 0.3 Hz / Kpa, thus meeting the requirements. Therefore, it can be determined that the design of the resonant pressure sensor 100 meets the requirements.

[0143] In some possible implementations, the difference between the temperature frequency coefficient of the first resonator 1 and the temperature frequency coefficient of the second resonator 2 can be less than or greater than 1%, for example, 1.2%. The pressure sensitivity of the second resonator 2 can also be greater than 0.3 Hz / Kpa, for example, 0.35 Hz / Kpa. Different application scenarios have different requirements for the accuracy of the resonant pressure sensor 100. As long as it can meet the application requirements of the specific scenario, it is acceptable. This application embodiment does not impose any limitations on this.

[0144] The above text provides a comprehensive explanation of the principle of the resonant pressure sensor 100 in this application from the aspects of basic structure, circuit, and signal processing. The following text will elaborate on the structure of each part of the resonant pressure sensor 100 in order to better understand its specific implementation.

[0145] Please see Figures 8 to 11 , Figure 8 This is a top view schematic diagram of the resonant pressure sensor according to an embodiment of this application; Figure 9 This is a bottom view schematic diagram of the resonant pressure sensor according to an embodiment of this application; Figure 10a for Figure 8 A schematic diagram of the cross-sectional structure at position C1-C1; Figure 10b This is a schematic cross-sectional view of another location of the first resonator in the resonant pressure sensor according to an embodiment of this application. Figure 11 for Figure 8 A schematic diagram of the cross-sectional structure at position C2-C2.

[0146] Understandably, the core reason why the resonant pressure sensor 100 achieves a high pressure response from the first resonator 1 and an extremely low pressure response from the second resonator 2 is that the two resonators are connected to the substrate 3 using different fixing methods. Specifically, the second resonator 2, because its bottom 321 (i.e., the surface of the second substrate 21 facing away from the second piezoelectric layer 22) is fixed, cannot vibrate, resulting in a very small response to external pressure. Meanwhile, the first resonator 1, suspended on the substrate 3, experiences less vibration resistance and has a high degree of spatial freedom, thus allowing it to vibrate normally and respond to external pressure. Therefore, the fixing method of the two resonators on the substrate 3 is particularly important.

[0147] like Figures 8 to 10a As shown, in one possible implementation, the first space 31 is configured as a perforated structure penetrating the substrate 3 along the thickness direction Z of the substrate. Alternatively, it can be understood that the first substrate 11 of the first resonator 1 is directly disposed within the substrate 3. Figure 10a As shown, the first substrate 11 has a top surface 11a and a bottom surface 11b. The top surface 11a is used to support the first piezoelectric layer 12, and the bottom surface 11b is the surface facing away from the first piezoelectric layer 12. With this structure, the bottom surface 11b of the first substrate 11 is not obstructed by the substrate 3, and the entire first resonator 1 has a large vibration space. Figure 10b As shown, in some possible implementations, the first space 31 may not penetrate the substrate 3, but may be configured as a groove with a bottom 321. There is a vibration space between the bottom surface 11b of the first substrate 11 and the bottom 321 of the groove, ensuring that the first substrate 11 will not collide with the substrate 3 when it vibrates. The first space 31 may also be configured with other structures, and the embodiments of this application do not limit this.

[0148] like Figure 11As shown, in one possible implementation, the second space 32 is configured as a groove structure with a bottom 321. The surface of the second substrate 21 facing away from the second piezoelectric layer 22 is in contact with the bottom 321 of the second space 32, and the outer peripheral side 21c of the second substrate 21 is in contact with the substrate 3. The second substrate 21 also has a top surface 21a and a bottom surface 21b. The top surface 21a is used to support the second piezoelectric layer 22, and the bottom surface 21b is the surface facing away from the second piezoelectric layer 22. With this structure, the bottom surface 21b of the second substrate 21 is in contact with the bottom 321 of the second space 32, with no gap 42 between them. This restricts the degree of freedom of the second substrate 21 in the thickness direction Z of the substrate, preventing it from vibrating. The vibration resistance of the second resonator 2 is large, thus it is insensitive to pressure. Changes in external pressure have no effect on the resonant frequency of the second resonator 2, and the measured data is only used for temperature compensation. Furthermore, by also connecting the outer peripheral side 21c of the second substrate 21 to the substrate 3, the mechanical stability of the second substrate 21 on the substrate 3 is further enhanced, making the second resonator 2 completely unable to vibrate and minimizing the pressure sensitivity. This can be understood as making... Figure 6 The slope of S2 is closer to 0. In some possible implementations, the outer periphery 21c of the second substrate 21 may not be in contact with the substrate 3, as long as the bottom 321 of the second substrate 21 is in contact with the substrate 3 and cannot vibrate freely. This application does not limit this.

[0149] It should be noted that the embodiments of this application do not limit the specific shapes of the piezoelectric layer, substrate, first space 31, and second space 32 of each resonator. For example... Figure 8 As shown, in one possible implementation, the first piezoelectric layer 12 and the second piezoelectric layer 22 are both rectangular (or can be understood as having a rectangular cross-section) in a plane perpendicular to the thickness direction Z of the substrate. Correspondingly, the first substrate 11 and the second substrate 21 are also set as rectangular structures, and the first space 31 and the second space 32 are also set as rectangular spaces. In some possible implementations, the first piezoelectric layer 12 and the second piezoelectric layer 22 may also be circular, triangular, irregular, etc., in a plane perpendicular to the thickness direction Z of the substrate. The shapes of the first substrate 11, the second substrate 21, the first space 31, and the second space 32 can be adjusted according to the shape of the piezoelectric layers, and this application embodiment does not limit this.

[0150] like Figure 10aAs shown, in one possible implementation, the connecting part 41 is suspended within the first space 31, with one side of the connecting part 41 connected to the inner wall surface 31a of the first space 31 and the other side connected to the outer peripheral surface of the first base 11. With this structure, the connecting part 41 forms a cantilever beam structure between the outer peripheral surface of the first base 11 and the inner wall surface 31a of the first space 31, allowing the first base 11 to be suspended on the substrate 3, which is beneficial for the vibration of the first resonator 1. It should be noted that the first base 11, substrate 3, and connecting part 41 are integral structures in the accompanying drawings of this application. Therefore, there is no clear boundary line between the connecting part 41 and the first base 11 and substrate 3; the dashed lines shown in the figures are merely imaginary boundary lines for understanding the scheme.

[0151] In one possible implementation, the first substrate 11, the connecting portion 41, and the portion of the substrate 3 connected to the connecting portion 41 are configured as an integral structure, and the second substrate 21 and the portion of the substrate 3 connected to the second substrate 21 are also configured as an integral structure. Alternatively, it can be understood that the first substrate 11, the second substrate 21, and the connecting portion 41 are all integrally formed on the substrate 3, which can greatly simplify the structure and manufacturing process of the resonant pressure sensor 100. In some possible implementations, any component of the first substrate 11, the second substrate 21, and the connecting portion 41 can be a separate structure from the substrate 3. For example, a first space 31 and a second space 32 can be hollowed out on the substrate 3, and then the first substrate 11, the second substrate 21, and the connecting portion 41 can be fixed within the corresponding spaces. This application does not limit this approach.

[0152] It should be noted that the processing method of the first substrate 11 and the connecting portion 41 is not limited in the embodiments of this application. In one possible implementation, the first substrate 11 and the connecting portion 41 are formed on the substrate 3 by an etching process. The etching process is a key process in the fields of semiconductor manufacturing, microelectromechanical systems (MEMS) and micro-nano fabrication. It can remove material from a specific area of ​​the material surface to achieve the desired micro-nano structure. For example, for the first resonator 1, a portion of the substrate 3 corresponding to the first piezoelectric layer 12 can be directly used as the first substrate 11. The substrate 3 at the bottom 321 of the first substrate 11 is hollowed out by an etching process to provide a vibration space. Then, a hole-like structure is processed around the first substrate 11 by an etching process as a gap 42. The structure between adjacent through holes forms the connecting portion 41. For the second resonator 2, the second piezoelectric layer 22 is directly fixed on the substrate 3, and the portion of the substrate 3 corresponding to the second piezoelectric layer 22 serves as the second substrate 21, without any other unnecessary processing steps.

[0153] Those skilled in the art will understand that photolithography and other steps can precede the etching process. Specifically, a layer of photoresist is coated on the material surface, the design pattern is transferred onto the photoresist using photolithography, and then development is performed to expose the material areas to be etched. Etching is then performed to remove the material not protected by the photoresist. By monolithically integrating the first resonator 1 and the second resonator 2 onto a single substrate 3, a single photolithography process can be achieved, reducing multiple steps and greatly simplifying the process.

[0154] The specific type of etching process is not limited. In one possible implementation, deep reactive ion etching (DRIE) is used to fabricate the first substrate 11 and the connection portion 41 on the substrate 3. DRIE, based on inductively coupled plasma (ICP) technology, combines physical bombardment and chemical reaction mechanisms, enabling high-precision, high-selectivity, and high aspect ratio etching. The resonant pressure sensor 100 fabricated using this process exhibits high precision and significantly improved product yield. Besides DRIE, reactive ion etching, physical etching, plasma etching, and laser etching processes can also be used, depending on the specific engineering requirements.

[0155] Those skilled in the art will understand that the connecting part 41 can be considered as an "anchor point," and the way the first resonator 1 is suspended and fixed through the connecting part 41 can also be understood as "anchor point fixing." The structure and distribution of the anchor point (first connecting part 411) play a decisive role in the vibration effect and pressure sensitivity of the first resonator 1. There are many ways to distribute the anchor points, and this application embodiment does not impose specific limitations on this. Several possible solutions are described below with reference to the accompanying drawings.

[0156] Please see Figures 12a to 12f , Figures 12a to 12f This is a schematic diagram of the layout of the connection part in the resonant pressure sensor of this application embodiment.

[0157] It should be noted that, Figures 12a to 12f Only the portion of substrate 3 where the first base 11 and connecting portion 41 are located is shown. The outermost boundary line in the figure does not represent the boundary line of substrate 3. Furthermore, the first base 11, connecting portion 41, and substrate 3 shown in the figure are all integral structures. For ease of understanding, the first connecting portion 411 is represented by shading, and the boundary line between the connecting portion 41 and substrate 3 and first base 11 is represented by dashed lines. These shading and dashed lines do not exist in the actual structure; only the gap 42 represented by the solid line frame is the visible actual structure.

[0158] like Figures 12a to 12fAs shown, in one possible implementation, there are multiple connecting portions 41, which are distributed circumferentially around the first base 11. There are also multiple gaps 42, which are distributed circumferentially around the first base 11, and there is one gap 42 between adjacent connecting portions 41. Specifically, the number of connecting portions 41 can be two, three, four, or more; this embodiment does not limit this.

[0159] It is understandable that, under a constant excitation voltage, the amplitude of vibration of the first resonator 1 is related to the mechanical strength of the connecting portion 41. While ensuring the reliability of the connection between the first substrate 11 and the substrate 3, the more connecting portions 41 there are, the smaller the size of each connecting portion 41 can be, resulting in lower mechanical strength and easier bending and deformation. This reduces the vibration resistance experienced by the first resonator 1, thereby improving the quality factor and making it more sensitive to external pressure. Therefore, using multiple connecting portions 41 to fix the first substrate 11 can improve the pressure sensitivity of the first resonator 1 while ensuring connection reliability. The circumferentially spaced distribution of multiple first connecting portions 411 around the first substrate 11 is to balance the stress points of the first substrate 11 and improve the consistency of vibration at various points. In some possible implementations, only one connecting portion 41 may be provided, or multiple connecting portions 41 may be used, but these multiple connecting portions 41 are not distributed circumferentially along the first substrate, but are concentrated on one side. This embodiment does not limit this.

[0160] It should be noted that the specific distribution location of the plurality of connecting portions 41 is not limited in the embodiments of this application. In one possible implementation, the plurality of connecting portions 41 are distributed on both sides of the first base 11 in its length direction (e.g., Figure 12a , Figure 12c Alternatively, multiple connecting portions 41 may be distributed on both sides in their width direction (e.g., Figure 12b , Figure 12d Alternatively, the first base 11 may have connecting portions 41 distributed on both sides in its length and width directions (e.g., Figure 12e , Figure 12f The connecting parts 41 are distributed on opposite sides or around the first base 11. Correspondingly, the gaps 42 are also distributed on opposite sides or around the first base 11. This can prevent the connecting parts 41 from being concentrated, making the stress points of the first base 11 more uniform, the vibration more stable, and the output signal more stable.

[0161] In one possible implementation, multiple connecting portions 41 are symmetrically distributed along the length direction X and / or the width direction Y of the first base. Alternatively, this can be understood as the number, shape, and size of the connecting portions 41 being the same on both sides of the length direction X of the first base, and their positions corresponding. Similarly, the number, shape, and size of the connecting portions 41 are the same on both sides of the width direction Y of the first base, and their positions corresponding. Correspondingly, multiple gaps 42 are also symmetrically distributed along the length direction X and / or the width direction Y of the first base, meaning that the number, shape, and size of the gaps 42 on opposite sides of the first base 11 are the same, and their positions correspond. Figures 12a to 12f All the schemes shown adopt this symmetrical structure. The symmetrical distribution of the connecting parts 41 makes the force points on both sides of the first base 11 evenly distributed, the mechanical strength during vibration is more reliable, and the vibration is more stable.

[0162] It should be noted that the specific shape of the connecting portion 41 is not limited in this application embodiment. For ease of understanding, the two sides in the length direction X of the first base are defined as the first side 111 and the second side 112, and the two sides in the width direction Y of the first base are defined as the third side 113 and the fourth side 114. In one possible implementation, the connecting portion 41 includes the first connecting portion 411, as shown below. Figure 12a As shown, the first connecting portion 411 extends from one end to the other in the width direction Y of the first substrate. Alternatively, it can be understood that the entire first side 111 and / or the entire second side 112 of the first substrate 11 are connected to the substrate 3 through the first connecting portion 411. In one possible implementation, as... Figure 12b As shown, the first connecting portion 411 extends from one end to the other in the length direction X of the first substrate. Alternatively, it can be understood that the entire third side 113 and / or the entire fourth side 114 of the first substrate 11 are connected to the substrate 3 through the first connecting portion 411.

[0163] The extension direction of the first connecting part 411 can be understood as the length direction of the side of the corresponding first base 11. The side is connected to the substrate 3 through the first connecting part 411. The first connecting part 411 is relatively long, which strengthens the connection between the first base 11 and the substrate 3. It also has high mechanical strength during vibration, low risk of breakage and damage, and improves the reliability of the resonant pressure sensor 100.

[0164] The number and distribution of the first connecting parts 411 are not limited. For example... Figure 12aAs shown, in one possible implementation, there are two first connecting portions 411. These two first connecting portions 411 are disposed on both sides of the first substrate 11 along the length direction X, and each first connecting portion 411 extends from one end to the other along the width direction Y of the first substrate. Alternatively, it can be understood that the first side 111 and the second side 112 are each connected to the substrate 3 through a first connecting portion 411. Figure 12a , Figure 12b As shown, in one possible implementation, there are two first connecting portions 411, which are disposed on both sides of the first substrate 11 in the width direction Y. Each first connecting portion 411 extends from one end to the other in the length direction X of the first substrate. Alternatively, it can be understood that the third side 113 and the fourth side 114 are each connected to the substrate 3 through a first connecting portion 411. By providing one first connecting portion 411 on each of the two opposite sides of the first substrate 11, the distribution of the first connecting portions 411 is uniform and symmetrical, resulting in uniform stress points on the first substrate 11. In some possible implementations, only one connecting portion 41 may be provided; this embodiment does not limit this.

[0165] like Figures 12c to 12f As shown, in one possible implementation, the connecting portion 41 includes a second connecting portion 412, the length of which is less than the length and width of the first base 11. The length direction of the second connecting portion 412 can be understood as the length direction of the side of the corresponding first base 11. For example, Figure 12e The length direction of the second connecting portion 412 above the first side 111 is the same as the length direction of the first side 111, that is, the same as the width direction Y of the first base. The length direction of the second connecting portion 412 on the left side of the third side 113 is the same as the length direction of the third side 113, that is, the same as the length direction X of the first base. The length of the second connecting portion 412 is less than the length and width of the first base 11. It can be understood that the second connecting portion 412 is shorter than any side of the first base 11. Its structure is relatively weak and its mechanical strength is low. It is easy to bend and deform during the vibration of the first base 11, thus reducing the vibration resistance.

[0166] The number and distribution of the first connecting parts 411 are not limited. For example... Figure 12c As shown, in one possible implementation, there are multiple second connecting portions 412, distributed on both sides of the first base 11 along its length direction; that is, the first side 111 and the second side 112 are correspondingly provided with second connecting portions 412. Figure 12d As shown, in one possible implementation, multiple second connecting portions 412 are distributed on both sides of the first base 11 in its width direction. That is, the third side 113 and the fourth side 114 are respectively provided with second connecting portions 412. Figure 12e As shown, in one possible implementation, multiple second connecting portions 412 are distributed on both sides of the length direction X and both sides of the width direction Y of the first base. The second connecting portions 412 are distributed on both opposite sides of the first base 11, making the distribution of the second connecting portions 412 uniform and symmetrical, and ensuring uniform stress points on the first base 11. In some possible implementations, the second connecting portions 412 may only be provided on one side of the length direction X and / or width direction of the first base; this application embodiment does not impose such limitations.

[0167] like Figures 12c to 12f As shown, in one possible implementation, at least two second connecting portions 412 are spaced apart on the same side of the first base 11. For example, Figure 12c Multiple second connecting portions 412 are provided above the first side 111 and below the third side 113. It should be noted that the number of connecting portions 41 in the figure is for illustrative purposes only. Providing multiple second connecting portions 412 at intervals on the same side of the first base 11 can distribute the stress points on the same side of the first base 11, preventing the second connecting portions 412 from breaking or being damaged during vibration. In some possible implementations, only one second connecting portion 412 may be provided on the same side of the first base 11; this embodiment does not limit this.

[0168] like Figures 12a to 12e As shown, in one possible implementation, only the first connecting portion 411 may be provided around the first base 11. For example, Figure 12a A first connecting portion 411 is provided above the first side 111 and below the second side 112. In this structure, there is an elongated gap 42 on the left side of the third side 113 and the right side of the fourth side 114 of the first substrate 11, and the gap 42 extends from one side of the first substrate 11 to the other along the length direction X of the first substrate. If the first substrate 11 and the connecting portion 41 are processed on the substrate 3 by etching, it is only necessary to etch two elongated holes around the area corresponding to the first piezoelectric layer 12, and the processing method is relatively simple. Figure 12b A first connecting part 411 is provided on the left side of the third side 113 and on the right side of the fourth side 114. In this structure, there is a long strip gap 42 above the first side 111 and below the second side 112 of the first base 11. The gap 42 extends from one side of the first base 11 to the other side in the width direction Y of the first base.

[0169] like Figures 12c to 12e As shown, in one possible implementation, only the second connecting portion 412 may be provided around the first base 11. For example, Figure 12cMultiple second connecting portions 412 are provided above the first side 111, and multiple second connecting portions 412 are provided below the second side 112. In this structure, there is an elongated gap 42 on the left side of the third side 113 and the right side of the fourth side 114 of the first base 11. In addition, multiple shorter gaps 42 are distributed above the first side 111 and below the second side 112. Figure 12d Multiple second connecting portions 412 are provided on the left side of the third side 113 and on the right side of the fourth side 114. In this structure, there is an elongated gap 42 above the first side 111 and below the second side 112 of the first base 11. In addition, there are multiple shorter gaps 42 distributed on the left side of the third side 113 and the right side of the fourth side 114. Figure 12e Multiple second connecting parts 412 are distributed on the four sides around the first base 11, and multiple gaps 42 are also distributed on each side.

[0170] like Figure 12f As shown, in one possible implementation, the first connecting portion 411 and the second connecting portion 412 can also be mixed and distributed around the first base 11. For example, multiple second connecting portions 412 are distributed above the first side 111, multiple second connecting portions 412 are also distributed below the second side 112, a first connecting portion 411 is provided on the left side of the third side 113, and a first connecting portion 411 is also provided on the right side of the fourth side 114. In this structure, only multiple shorter gaps 42 are distributed above the first side 111 and below the second side 112. The first connecting portion 411 and the second connecting portion 412 can also be mixed and distributed around the first base 11 in other layout ways, and this application embodiment does not limit this.

[0171] It should be noted that the specific shape of the connecting portion 41 is not limited. In one possible implementation, the cross-section of the connecting portion 41 in the thickness direction Z of the substrate is rectangular. Alternatively, it can be understood that the connecting portion 41 is a cuboid structure. With this structure, the gap 42 between adjacent connecting portions 41 is a square hole, which has a regular shape and is easy to process. In some possible implementations, the connecting portion 41 can also be a cylindrical structure, a prism structure, etc.

[0172] It will be understood by those skilled in the art that the specific structure and material of the substrate 3 are not limited. For example... Figure 2 As shown, in one possible implementation, the substrate 3 is a silicon substrate and includes a doped silicon layer 33, an oxide isolation layer 34 and an undoped silicon layer 35 stacked sequentially. The first substrate 11, the connecting portion 41 and the second substrate 21 are all located on the doped silicon layer 33 and are integrated with the doped silicon layer 33.

[0173] The doped silicon layer 33 alters the electrical properties of the silicon substrate by introducing impurities (such as boron or phosphorus). The doped silicon layer changes its conductivity, making it more suitable for transmitting and detecting electrical signals. Furthermore, the doped silicon layer 33 enhances the mechanical strength of the silicon substrate 3, ensuring the sensor's stability under pressure. The oxide isolation layer 34 exhibits high chemical stability, effectively isolating different electrodes or circuit components and preventing leakage and short circuits. The oxide isolation layer 34 is typically made of silicon dioxide (SiO2), which is chemically stable and protects the silicon substrate 3 from external environmental factors (such as humidity and corrosive gases). It can also withstand high temperatures, making it suitable for operation in high-temperature environments. The undoped silicon layer 35 is the original single-crystal silicon material, i.e., a silicon layer without introduced impurities. The undoped silicon layer 35 provides the mechanical support framework for the sensor, ensuring the overall structural stability of the sensor. Furthermore, the undoped silicon layer 35 has good processing compatibility and is suitable for microfabrication using MEMS processes. Besides silicon, substrate 3 can also be made of other materials, such as semiconductor materials, carbon-based materials, etc., which will not be listed one by one in the embodiments of this application.

[0174] like Figure 10a As shown, in one possible implementation, the thickness of the first substrate 11 and the thickness of the connecting portion 41 are both less than the thickness of the doped silicon layer 33. The surfaces of the first substrate 11 facing the first piezoelectric layer 12 and the connecting portion 41 facing the first piezoelectric layer 12 are flush with the surfaces of the doped silicon layer 33 facing the first piezoelectric layer 12. Using this structure, the structure on the side of the substrate 3 opposite to the first piezoelectric layer 12 can be directly hollowed out, and through-holes can be fabricated on the remaining thin plate-like structure to form components such as the first substrate 11, the connecting portion 41, and the gap 42, greatly simplifying the manufacturing process. The thinner thickness of the first substrate 11 and the connecting portion 41 compared to the thickness of the doped silicon layer 33 also weakens the mechanical strength, reducing the vibration resistance of the first resonator 1 and improving the quality factor Q.

[0175] Those skilled in the art will understand that the specific types of the first piezoelectric layer 12 and the second piezoelectric layer 22 are not limited. In one possible implementation, both the first piezoelectric layer 12 and the second piezoelectric layer 22 are piezoelectric thin films. Piezoelectric thin films can generate significant electrical signals under minute mechanical stress or pressure, enabling high-precision measurements. Furthermore, piezoelectric thin films are highly flexible and relatively thin, which is beneficial for the miniaturization of the resonant pressure sensor 100 and facilitates fabrication. Piezoelectric thin films can be prepared using various film-forming techniques (such as sputtering, chemical deposition, etc.), exhibiting good processability and enabling centralized processing through semiconductor manufacturing processes, thereby achieving large-scale production.

[0176] In one possible implementation, the resonant pressure sensor 100 is a TPoS (Thin Piezoelectric film on Silicon) resonant pressure sensor 100. The TPoS resonant pressure sensor 100 is a sensor based on a piezoelectric film on silicon, using silicon as the substrate 3, and utilizing the piezoelectric effect of the piezoelectric film and the mechanical properties of the silicon substrate to measure pressure. The TPoS resonant pressure sensor 100 combines the high electromechanical conversion efficiency of the piezoelectric film with the low acoustic loss of silicon material, resulting in high electromechanical conversion efficiency, high detection accuracy, high resolution, and high resolution, and exhibiting strong compatibility with MEMS processes. The resonant pressure sensor 100 provided in this application embodiment can also be of other types, specifically related to the structure and materials of the substrate 3, piezoelectric layer, and other components; this application embodiment does not impose any limitations on these aspects.

[0177] It should be noted that the specific material of the piezoelectric film is not limited, and can be, for example, AlN (aluminum nitride), ZnO (zinc oxide), PZT (lead zirconate titanate), PVDF (polyvinylidene fluoride), LiNbO3 (lithium niobate), LiTaO3 (lithium tantalate), etc. In one possible implementation, the thickness of the piezoelectric film is in the range of 0.1 μm to 1 μm, which facilitates production. Preferably, the thickness of the piezoelectric film can be in the range of 0.5 μm to 1 μm, resulting in better quality. The thickness of the piezoelectric film can also be less than 0.1 μm or greater than 1 μm; this application does not impose any limitations on this.

[0178] like Figure 1 As shown, in one possible implementation, the first resonator 1 further includes a first excitation element 13 and a first detection element 14, which are disposed on the side of the first piezoelectric layer 12 facing away from the first substrate 11. The second resonator 2 further includes a second excitation element 23 and a second detection element 24, which are disposed on the side of the second piezoelectric layer 22 facing away from the second substrate 21.

[0179] This can be understood as follows: both the first resonator 1 and the second resonator 2 include excitation elements and detection elements, used to excite the piezoelectric layer to vibrate, detect the induced charge generated by the piezoelectric layer, and output signals. The excitation and detection elements are electromechanical transducers. Applying voltage to the excitation element causes the piezoelectric layer to undergo mechanical deformation under the inverse piezoelectric effect, driving the entire resonator to vibrate according to a specific mode, thus realizing the conversion from electrical energy to mechanical energy. The detection element uses the direct piezoelectric effect to collect the induced charge generated by the piezoelectric layer under strain. The polarity of the induced charge changes periodically over time, ultimately forming an output current. For the first resonator 1, the first piezoelectric layer 12 can vibrate normally under the action of the first excitation element 13. For the second resonator 2, the second piezoelectric layer 22 cannot vibrate normally. Setting the second excitation element 23 allows for the control of variables, such as inputting the same voltage to the first resonator 1 and the second resonator 2, making their initial modes identical. The charge detected by the second detection element 24 is a variable caused by ambient temperature.

[0180] In one possible implementation, the first piezoelectric layer 12 and the second piezoelectric layer 22 have the same shape and size, the first excitation element 13 and the second excitation element 23 have the same shape and size, the first detection element 14 and the second detection element 24 have the same shape and size, and the distance between the first excitation element 13 and the first detection element 14 and the distance between the second excitation element 23 and the second detection element 24 are the same.

[0181] This can be understood as setting the first resonator 1 and the second resonator 2 to be exactly the same, differing only in their fixing method on the substrate 3. This configuration allows for controllable variables, ensuring that the frequency-temperature characteristics of the first resonator 1 and the second resonator 2 are similar. This enables the reduction of temperature's influence on pressure sensing through frequency difference calculation, achieving a more effective temperature compensation function. Furthermore, the identical geometric dimensions ensure that the resonant signal strengths of the two piezoelectric layers are similar when unobstructed by external forces, reducing the design and manufacturing difficulty of the signal interface circuit. In some possible implementations, the structure, materials, and dimensions of the piezoelectric layers, excitation elements, and detection elements in the first resonator 1 and the second resonator 2 may not be entirely identical. Subsequent processing and calculations can eliminate the influence of these differences on the detection results; this application does not impose such limitations.

[0182] Those skilled in the art will understand that excitation and detection elements can be implemented in multiple ways, and the embodiments of this application do not limit the type of their substrate. For example... Figure 1As shown, in one possible implementation, the first resonator 1 further includes a first electrode assembly 15, which includes a first input electrode 151, a first output electrode 152, and a first interdigital electrode 153. The first input electrode 151 and the first output electrode 152 are disposed on the substrate 3, and the first interdigital electrode 153 is disposed correspondingly to the first piezoelectric layer 12. The second resonator 2 further includes a second electrode assembly 25, which includes a second input electrode 251, a second output electrode 252, and a second interdigital electrode 253. The second input electrode 251 and the second output electrode 252 are disposed on the substrate 3, and the second interdigital electrode 253 is disposed correspondingly to the second piezoelectric layer 22.

[0183] Please see Figures 13 to 14 , Figure 13 This is an exploded structural diagram of the first electrode assembly in the resonant pressure sensor according to an embodiment of this application; Figure 14 This is an exploded structural diagram of the second electrode assembly in the resonant pressure sensor according to an embodiment of this application.

[0184] like Figure 13 As shown, the first interdigital electrode 153 includes two first finger-like structures 1531 arranged opposite to each other. The two first finger-like structures 1531 are electrically connected to the first input electrode 151 and the first output electrode 152 respectively through a first transmission line 154. The first input electrode 151, the first transmission line 154 connected thereto, and the first finger-like structures 1531 constitute the first excitation element 13, and the first output electrode 152, the first transmission line 154 connected thereto, and the first finger-like structures 1531 constitute the first detection element 14.

[0185] like Figure 14 As shown, the second interdigital electrode 253 includes two opposing second finger-like structures 2531, which are electrically connected to the second input electrode 251 and the second output electrode 252 respectively via a second transmission line 254. The second input electrode 251, the second transmission line 254 connected thereto, and the second finger-like structure 2531 constitute the second excitation element 23, while the second output electrode 252, the second transmission line 254 connected thereto, and the second finger-like structure 2531 constitute the second detection element 24.

[0186] This can be understood as follows: both resonators use input electrodes to input voltage and output electrodes to detect resonant frequency and output current signals. Interdigitated electrodes are positioned on the side of the piezoelectric layer facing away from the substrate. Each interdigitated electrode has two finger-like structures (or comb-like structures), and the input and output electrodes are each connected to their respective finger-like structures via a transmission line. Interdigitated electrodes are finger-like or comb-like in-plane periodic patterned electrodes, which can increase the effective length and surface area of ​​the electrodes, improve the capacitance and electrochemical reaction rate between the electrodes, thereby enhancing the sensitivity of the resonant pressure sensor 100. The finger-like structure of the interdigitated electrodes also enhances the electric field strength, making the electric field distribution on the piezoelectric layer surface more uniform, which helps improve the performance consistency of the piezoelectric layer, reduces local stress concentration, and thus improves the performance and reliability of the piezoelectric layer.

[0187] For example, Figure 13 The first finger structure 1531 connected to the first input electrode 151 increases the effective length and surface area of ​​the first input electrode 151. The first finger structure 1531 can be regarded as part of the first input electrode 151. The first input electrode 151, together with the first transmission line 154 and the first finger structure 1531 connected thereto, constitute the first excitation element 13. Figure 13 The first finger structure 1531 connected to the first output electrode 152 increases the effective length and surface area of ​​the first output electrode 152. The first finger structure 1531 can be regarded as part of the first output electrode 152. The first output electrode 152, together with the first transmission line 154 and the first finger structure 1531 connected thereto, constitute the first detection element 14. Figure 14 The second excitation element 23 and the second detection element 24 can be understood in the same way, and will not be elaborated here.

[0188] In one possible implementation, the materials for the interdigital electrodes, input electrodes, output electrodes, and transmission lines of each resonator are metals such as silver, copper, gold, aluminum, nickel, or lead, with no specific restrictions. For example... Figure 13 , Figure 14 As shown, in one possible implementation, the input electrodes of each resonator, as well as the first transmission line 154 and the first finger structure 1531 connected thereto, are configured as an integrated structure. Alternatively, the first excitation element 13 can be configured as an integrated structure; similarly, the first detection element 14, the second excitation element 23, and the second detection element 24 can also be integrated structures to reduce manufacturing difficulty. The electrodes, finger structures, and transmission lines can also be separate structures; this application does not limit this.

[0189] In one possible implementation, the thickness of both the first interdigital electrode 153 and the second interdigital electrode 253 is in the range of 0.2 μm to 2 μm, which facilitates processing. In some possible implementations, the thickness of each interdigital electrode may be less than 0.2 μm or greater than 2 μm, and the embodiments of this application do not impose any limitations on this.

[0190] It should be noted that the embodiments of this application do not limit the substrate processing method of the interdigital electrodes. In one possible implementation, the interdigital electrodes can be directly formed on the corresponding piezoelectric layer by chemical deposition. This processing method is simple to operate and has high precision.

[0191] like Figure 1 , Figure 2 As shown, in one possible implementation, a first isolation structure 51 is provided between the first input electrode 151, the first output electrode 152, the first transmission line 154 and the substrate 3. A second isolation structure 52 is provided between the second input electrode 251, the second output electrode 252, the second transmission line 254 and the substrate 3. Both the first isolation structure 51 and the second isolation structure 52 are insulators. The first isolation structure 51 and the second isolation structure 52 can isolate the signals from the electrodes and the transmission line, preventing signal leakage into the substrate 3.

[0192] The substrate shape of each isolation structure is not limited and can be set according to the shape of the electrodes and transmission lines. In one possible implementation, the thickness of the oxide isolation structure is in the range of 0.3μm to 1.5μm, which is easy to process and produces good quality finished products. The thickness of the first isolation structure 51 and the second isolation structure 52 can also be less than 0.3μm or greater than 1.5μm, and this application embodiment does not impose any restrictions on this. In one possible implementation, the first isolation structure 51 and the second isolation structure 52 are made of silicon dioxide. Silicon dioxide has high resistivity and low dielectric constant, good insulation, can effectively prevent signal leakage, and can reduce parasitic capacitance, and is highly compatible with silicon-based manufacturing processes. The first isolation structure 51 and the second isolation structure 52 can also be made of other materials, and this application embodiment does not impose any restrictions on this.

[0193] like Figure 1 As shown, in one possible implementation, two first ground electrodes 53 and two second ground electrodes 54 are also disposed on the substrate 3. The two first ground electrodes 53 are respectively disposed near the first input electrode 151 and the first output electrode 152, realizing a GS (Ground-Signal) electrode structure to reduce signal interference and provide stable signal transmission. Similarly, a GS electrode structure can also be realized between the two second ground electrodes 54 and the second input electrode 251 and the second output electrode 252 to reduce signal interference and provide stable signal transmission. The specific positions of each ground electrode are not limited; the figure is for illustrative purposes only.

[0194] Please see Figures 15 to 16 , Figure 15 This is a schematic diagram of the layout of the first resonator and the second resonator in the resonant pressure sensor according to an embodiment of this application; Figure 16 This is a schematic diagram of another layout of the first resonator and the second resonator in the resonant pressure sensor of this application embodiment.

[0195] Those skilled in the art will understand that the number of the first resonator 1 and the second resonator 2 in the resonant pressure sensor 100 is not limited. In one possible implementation, there may be one or more first resonators 1 and one or more second resonators 2. For example, there may be only one first resonator 1 and one second resonator 2. Alternatively, there may be one first resonator 1 and multiple second resonators 2. Alternatively, there may be multiple first resonators 1 and one second resonator 2. Alternatively, multiple first resonators 1 and multiple second resonators 2 may be provided. The number of the two types of resonators can be flexibly set according to actual needs.

[0196] like Figure 15 As shown, in one possible implementation, there are multiple first resonators 1 and one or more second resonators 2, with each of the multiple first resonators 1 and the multiple second resonators 2 arranged in a one-to-one correspondence. A corresponding set of first resonators 1 and second resonators 2 constitutes a pressure detection component, and multiple pressure detection components are arranged in an array on the substrate 3. The specific number of first resonators 1 and second resonators 2 is not limited, and this embodiment of the application does not impose any limitation on this.

[0197] By employing an array of multiple first resonators 1 and multiple second resonators 2, a compact structure is achieved, enabling applications in high-density, high-spatial-resolution pressure detection scenarios. The alternating distribution of the first resonators 1 and second resonators 2 enhances design flexibility and enables high-resolution multimodal detection. For example, each first resonator 1 detects the pressure at its location, while the corresponding second resonator 2 detects the ambient temperature at that location and compensates for the pressure of the first resonator 1.

[0198] The specific arrangement of the first resonator 1 and the second resonator 2 is not limited. For example... Figure 15 As shown, in one possible implementation, the resonators on the substrate 3 can be divided into two columns, one column consisting entirely of first resonators 1 and the other column consisting entirely of second resonators 2. Alternatively, each column of resonators can consist of alternating arrangements of first resonators 1 and second resonators 2.

[0199] like Figure 16As shown, in one possible implementation, the resonant pressure sensor 100 includes multiple first resonators 1 and one second resonator 2. The specific number of first resonators 1 is not limited; the figure is for illustrative purposes only. When the ambient temperature gradient is small, the pressure at multiple points can be measured using multiple first resonators 1, and temperature compensation can be performed on the data from all the first resonators 1 using a second resonator 2. This structure saves space and reduces manufacturing costs. The multiple first resonators 1 and the second resonator 2 can be arranged in a row, for example... Figure 16 Alternatively, multiple first resonators 1 may be arranged around the second resonator 2, and this application embodiment does not limit this.

[0200] It should be noted that the manufacturing process and specific procedures of the resonant pressure sensor 100 are not limited in the embodiments of this application. In one possible implementation, the resonant pressure sensor 100 is fabricated using MEMS technology, integrating electronic components onto a single chip using micromechanical structures, resulting in a sensor that is small in size, highly accurate, and stable. Specifically, the process may include steps such as design planning, material selection, thin film deposition, photolithography, etching, release and post-processing, packaging, and testing; the embodiments of this application do not limit these steps.

[0201] The above description illustrates the implementation of this application through specific embodiments. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Although the description of this application is presented in conjunction with some embodiments, this does not mean that the features of this application are limited to this embodiment. On the contrary, the purpose of describing the application in conjunction with embodiments is to cover other options or modifications that may be derived based on the claims of this application. To provide a thorough understanding of this application, many specific details will be included in the following description. This application may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of this application, some specific details will be omitted in the description. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0202] It should be noted that in this specification, similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0203] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0204] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0205] The limitations such as symmetry and similarity (e.g., same length, same width, etc.) mentioned in the embodiments of this application are all relative to the current level of technology, rather than absolute and strict definitions in a mathematical sense.

[0206] In the description of this application, it should be understood that "electrical connection" can be understood as physical contact and electrical conduction between components; it can also be understood as the form in which different components in a circuit structure are connected through physical lines that can transmit electrical signals, such as copper foil or wires on a printed circuit board (PCB).

[0207] Relative / Relative Setting: A relative setting with B can refer to A and B being face-to-face. For example, when two components are set relative to each other, these two components overlap in at least a portion of their area along a certain direction.

[0208] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A resonant pressure sensor, characterized in that, Includes a substrate, and a first resonator and a second resonator integrated on the substrate; The first resonator includes a first substrate and a first piezoelectric layer stacked sequentially, the first substrate being integrated into the substrate and the first piezoelectric layer being disposed on the side of the first substrate away from the substrate; the second resonator includes a second substrate and a second piezoelectric layer stacked sequentially, the second substrate being integrated into the substrate and the second piezoelectric layer being disposed on the side of the second substrate away from the substrate. The substrate has a first space and a second space spaced apart. The first substrate is suspended in the first space, and the outer periphery of the first substrate is fixedly connected to the substrate through a connecting part, and there is a gap between the first substrate and the substrate. The second substrate is disposed in the second space, and the surface of the second substrate facing away from the second piezoelectric layer is in contact with the substrate.

2. The resonant pressure sensor according to claim 1, characterized in that, The first space is configured as a hollow structure that penetrates the substrate along the thickness direction of the substrate; The second space is configured as a groove structure with a bottom, the surface of the second substrate facing away from the second piezoelectric layer is in contact with the bottom of the second space, and the outer peripheral side of the second substrate is in contact with the substrate.

3. The resonant pressure sensor as described in claim 1 or 2, characterized in that, The connecting part is suspended in the first space, and one side of the connecting part is connected to the inner wall of the first space, and the other side is connected to the outer peripheral surface of the first base.

4. The resonant pressure sensor as described in any one of claims 1-3, characterized in that, The connecting portion includes a first connecting portion that extends from one end of the first substrate in the width direction to the other end, or the first connecting portion extends from one end of the first substrate in the length direction to the other end.

5. The resonant pressure sensor as described in any one of claims 1-4, characterized in that, The connecting portion includes a second connecting portion, the length of which is less than the length of the first base and the width of the first base.

6. The resonant pressure sensor as described in any one of claims 1-5, characterized in that, The connecting parts are multiple, and the multiple connecting parts are distributed at intervals along the circumference of the first base; There are multiple gaps, which are distributed circumferentially along the first base, and there is one gap between adjacent connecting portions.

7. The resonant pressure sensor as described in claim 6, characterized in that, The plurality of connecting portions are distributed on both sides of the first base in its length direction and / or on both sides of the first base in its width direction; The plurality of gaps are distributed on both sides of the first substrate in its length direction and / or on both sides of the first substrate in its width direction.

8. The resonant pressure sensor as described in claim 7, characterized in that, The plurality of connecting portions are symmetrically distributed along the length direction and / or the width direction of the first base.

9. The resonant pressure sensor as described in claim 8, characterized in that, When the connecting portion includes a first connecting portion, there are two first connecting portions; the two first connecting portions are disposed on both sides of the first base in the length direction of the first base, and each first connecting portion extends from one end to the other end in the width direction of the first base; or, the two first connecting portions are disposed on both sides of the first base in the width direction of the first base, and each first connecting portion extends from one end to the other end in the length direction of the first base.

10. The resonant pressure sensor as described in claim 8, characterized in that, When the connecting portion includes a second connecting portion, there are multiple second connecting portions; the multiple second connecting portions are distributed on both sides of the first base in its length direction and / or on both sides of the first base in its width direction, and at least two second connecting portions are spaced apart on the same side of the first base.

11. The resonant pressure sensor as described in any one of claims 1-10, characterized in that, The cross-section of the connecting portion in the thickness direction of the substrate is rectangular.

12. The resonant pressure sensor as described in any one of claims 1-11, characterized in that, The first substrate, the connecting portion, and the portion of the substrate connected to the connecting portion are configured as an integral structure, and the second substrate and the portion of the substrate connected to the second substrate are configured as an integral structure.

13. The resonant pressure sensor as described in any one of claims 1-12, characterized in that, The substrate is a silicon substrate and includes a doped silicon layer, an oxide isolation layer and an undoped silicon layer stacked sequentially. The first substrate, the connecting portion and the second substrate are all located on the doped silicon layer and are integrated with the doped silicon layer. Wherein, the thickness of the first substrate and the thickness of the connecting portion are both less than the thickness of the doped silicon layer, and the surface of the first substrate facing the first piezoelectric layer and the surface of the connecting portion facing the first piezoelectric layer are both flush with the surface of the doped silicon layer facing the first piezoelectric layer.

14. The resonant pressure sensor as described in claim 13, characterized in that, The first substrate and the connecting portion are formed on the substrate by an etching process.

15. The resonant pressure sensor according to any one of claims 1-14, characterized in that, The first resonator further includes a first excitation element and a first detection element, wherein the first excitation element and the first detection element are disposed on the side of the first piezoelectric layer opposite to the first substrate; The second resonator further includes a second excitation element and a second detection element, the second excitation element and the second detection element being disposed on the side of the second piezoelectric layer opposite to the second substrate; Wherein, the first piezoelectric layer and the second piezoelectric layer have the same shape and size, the first excitation element and the second excitation element have the same shape and size, the first detection element and the second detection element have the same shape and size, and the distance between the first excitation element and the first detection element and the distance between the second excitation element and the second detection element are the same.

16. The resonant pressure sensor as described in claim 15, characterized in that, The first resonator further includes a first electrode assembly, which includes a first input electrode, a first output electrode, and a first interdigital electrode. The first input electrode and the first output electrode are disposed on the substrate, and the first interdigital electrode is disposed corresponding to the first piezoelectric layer. The first interdigital electrode includes two first finger-like structures disposed opposite to each other. The two first finger-like structures are electrically connected to the first input electrode and the first output electrode respectively through a first transmission line. The first input electrode, the first transmission line and the first finger-like structures connected thereto constitute the first excitation element, and the first output electrode, the first transmission line and the first finger-like structures connected thereto constitute the first detection element. The second resonator further includes a second electrode assembly, which includes a second input electrode, a second output electrode, and a second interdigital electrode. The second input electrode and the second output electrode are disposed on the substrate, and the second interdigital electrode is disposed corresponding to the second piezoelectric layer. The second interdigitated electrode includes two second finger-like structures arranged opposite to each other. The two second finger-like structures are electrically connected to the second input electrode and the second output electrode respectively through a second transmission line. The second input electrode, the second transmission line and the second finger-like structure connected thereto constitute the second excitation element, and the second output electrode, the second transmission line and the second finger-like structure connected thereto constitute the second detection element.

17. The resonant pressure sensor as described in claim 16, characterized in that, A first isolation structure is provided between the first input electrode, the first output electrode, the first transmission line and the substrate; A second isolation structure is provided between the second input electrode, the second output electrode, the second transmission line and the substrate; Both the first isolation structure and the second isolation structure are insulators.

18. The resonant pressure sensor as described in any one of claims 1-17, characterized in that, Both the first piezoelectric layer and the second piezoelectric layer are piezoelectric thin films.

19. The resonant pressure sensor as described in any one of claims 1-18, characterized in that, The temperature frequency coefficient of the first resonator differs from that of the second resonator by less than 1%, and the pressure sensitivity of the second resonator is less than 0.3 Hz / Kpa.

20. The resonant pressure sensor according to any one of claims 1-19, characterized in that, The first resonator may be one or more, and the second resonator may be one or more.

21. The resonant pressure sensor as described in claim 20, characterized in that, There are multiple first resonators and one or more second resonators, with each of the multiple first resonators and the multiple second resonators being configured in a one-to-one correspondence. A set of first and second resonators constitutes a pressure detection component, and multiple pressure detection components are arranged in an array on the substrate.

22. The resonant pressure sensor as described in any one of claims 1-21, characterized in that, The first resonator is a pressure-sensitive resonator, and the second resonator is a temperature-compensated resonator.

23. A resonant pressure sensor system, characterized in that, The resonant pressure sensor as described in any one of claims 1-22 further includes a mixer and a filter, wherein the mixer is used to mix the output signal of the first resonator with the output signal of the second resonator to output a mixed signal, and the filter is used to filter the mixed signal and output a pressure sensing signal.

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