Piezoelectric resonant pressure sensor and pressure compensation system

Abstract

The utility model discloses a piezoelectric resonant pressure sensor and a pressure compensation system, and relates to the technical field of sensitive element and sensor manufacturing in the electronic core industry, and the piezoelectric resonant pressure sensor comprises a piezoelectric assembly. The resonance assembly is arranged on one side of the piezoelectric assembly, the resonance assembly is made of an SOI wafer, and the SOI wafer comprises a device layer, a buried oxide layer and a substrate layer which are connected in sequence; the device layer is connected with the piezoelectric assembly, at least one resonant cavity is formed in the buried oxide layer, a pressure cavity is formed in the side, away from the device layer, of the substrate layer, and external pressure received by the pressure cavity can be transmitted to a resonant film on the device layer; the projection of at least one resonant cavity is located on the outer side of the projection of the pressure cavity in the direction, deviating from the piezoelectric assembly, of the resonant assembly. According to the piezoelectric resonant pressure sensor, the pressure can be detected through the change of the resonant frequency of the device layer, and the piezoelectric resonant pressure sensor can have higher bearing capacity, so that the piezoelectric resonant pressure sensor can have a larger pressure detection range.

Description

Technical Field

[0001] The present application relates to the technical field of sensitive components and sensor manufacturing in the core electronics industry, and in particular to a piezoelectric resonant pressure sensor and a pressure compensation system. Background Art

[0002] Pressure sensors can convert received pressure signals into electrical signals according to certain rules and output the electrical signals to other devices. They are sensitive components. Pressure sensors are widely used in defense, automobile, petroleum, aerospace, smart hardware and other technical fields, and belong to the core electronic industry technology field.

[0003] With the development of micro-electro-mechanical system (MEMS) technology, pressure sensors can be combined with MEMS technology to realize mass production of pressure sensors and improve the production efficiency of pressure sensors.

[0004] According to different working principles, pressure sensors can be divided into resonant pressure sensors, piezoresistive pressure sensors, capacitive pressure sensors, piezoelectric pressure sensors, piezoelectric resonant pressure sensors, etc. Among them, piezoelectric resonant pressure sensors have the advantages of good stability and high accuracy, and can be used in scenarios with high accuracy requirements and harsh working environments.

[0005] Based on the structure of the existing piezoelectric resonant pressure sensor, the piezoelectric resonant pressure sensor has a relatively complex structure, low detection efficiency and a small detection range. Utility Model Content

[0006] The present application provides a piezoelectric resonant pressure sensor and a pressure compensation system, which can detect pressure by changing the resonant frequency of the device layer, thereby improving the measurement accuracy. Moreover, due to the relatively simple structure, miniaturization and mass production are easier to achieve.

[0007] In a first aspect, the present application provides a piezoelectric resonant pressure sensor for use in the core electronics industry. The piezoelectric resonant pressure sensor comprises:

[0008] A piezoelectric component is directly or indirectly connected to an external circuit;

[0009] A resonant component is arranged on one side of the piezoelectric component, wherein the resonant component is made of an SOI wafer, and the SOI wafer includes a device layer, a buried oxide layer and a substrate layer connected in sequence;

[0010] The device layer is connected to the piezoelectric component, at least one resonant cavity is arranged in the buried oxide layer, a pressure cavity is opened on the side of the substrate layer away from the device layer, and the external pressure received by the pressure cavity can be transmitted to the resonant film on the device layer;

[0011] In the direction of the resonant component away from the piezoelectric component, a projection of at least one of the resonant cavities is located outside a projection of the pressure chamber.

[0012] The piezoelectric resonant pressure sensor is mainly composed of a piezoelectric component and a resonant component, wherein the resonant component is formed by processing an SOI wafer, and the resonant component consists of three parts: a device layer, a buried oxide layer, and a substrate layer. The piezoelectric component can be used as the core part of the piezoelectric resonant pressure sensor to drive the resonator to vibrate and detect the frequency change of the resonator caused by the pressure to be measured. The above driving and detection are based on the piezoelectric effect. The piezoelectric component is connected to the external circuit directly or indirectly to realize signal transmission and processing. The device layer is the main part that generates resonance, and the pressure chamber is used to receive external pressure and transmit the external pressure to the resonant film on the device layer.

[0013] The device layer, the buried oxide layer and the substrate layer are integrated. The device layer can be connected to the piezoelectric component to form the core structure of the sensor (piezoelectric resonator). The buried oxide layer and the substrate layer are both arranged on the other side of the device layer away from the piezoelectric component, responsible for sensing the change of the pressure to be measured. The above structure enables the sensor to detect pressure through the change of the resonant frequency of the device layer when it is under pressure, thereby improving the measurement accuracy.

[0014] The piezoelectric resonant pressure sensor provided in the example of the present application can withstand a larger pressure to be detected, thereby improving the pressure measurement range of the piezoelectric resonant pressure sensor and expanding the measurement range of the piezoelectric resonant pressure sensor, so that the piezoelectric resonant pressure sensor can be widely used in the core technology field of the electronics industry.

[0015] In some examples, the resonant cavity is opened on the buried oxide layer by means of a sacrificial layer.

[0016] The sacrificial layer can reduce the damage to the buried oxide layer and the surrounding layer structure during the opening of the resonant cavity, and the resonant cavity of appropriate size can be obtained through precise control. This setting method can ensure the processing accuracy of the resonant cavity and improve the product yield. And the sacrificial layer can ensure the integrity of the device layer and the substrate layer.

[0017] In some examples, part of the device layer closes or does not close the resonant cavity, and the part of the device layer that closes the resonant cavity is a resonant film.

[0018] The device layer can have certain vibration characteristics and energy conversion efficiency. The device layer can be specifically composed of a fixed part and a resonant film connected to each other. The device layer can generate a resonant frequency effect between the piezoelectric component and the resonant component. When the pressure to be measured is transmitted to the resonant component, it will cause the resonant frequency of the resonant film in the resonant component to change. The piezoelectric component uses the inverse piezoelectric effect to excite the resonant film to vibrate, and at the same time uses the direct piezoelectric effect to detect the resonant frequency change of the resonant film, thereby detecting the value of the pressure to be measured.

[0019] In some examples, the pressure cavity penetrates the substrate layer, and the buried oxide layer forms a pressure-sensitive film in a region corresponding to the pressure cavity;

[0020] At least one of the resonant cavities is located on the peripheral side of the pressure sensitive film, and the pressure received by the pressure cavity can act on the pressure sensitive film and be transmitted to the device layer.

[0021] At least one resonant cavity can be arranged around the projection of the pressure cavity. When at least two resonant cavities are arranged, more detection points can be provided, thereby improving the accuracy and stability of the measurement. When the pressure changes, the resonant films corresponding to different resonant cavities can produce corresponding resonant frequency changes, and these resonant films can verify each other, thereby improving the accuracy of the measurement.

[0022] At least one resonant cavity is located on the peripheral side of the pressure sensitive film, and the pressure received by the pressure cavity can act on the pressure sensitive film and be transmitted to the device layer. Specifically, the pressure received by the pressure cavity can be transmitted to the resonant film on the device layer through the anchor point.

[0023] The pressure chamber can completely penetrate the substrate layer or only partially penetrate the substrate layer. Such a setting can form a channel that is in direct contact with the external environment. When the pressure to be measured changes, the corresponding gas or liquid in the channel will be subjected to the corresponding pressure. The setting of the buried oxide layer can facilitate the processing of the pressure chamber. During the processing of the pressure chamber, the buried oxide layer can be used to identify the processing depth of the pressure chamber.

[0024] In some examples, the pressure sensitive film, the device layer, and the piezoelectric component are stacked on each other and receive external pressure together.

[0025] The above structure can form a thicker pressure-sensitive film. The thicker pressure-sensitive film can directly withstand pressure and transfer stress to the resonant film and piezoelectric components through the integrated laminated structure on the side of the resonant cavity and the entire pressure-sensitive film, and convert it into stress on the resonant film and piezoelectric components. In order to ensure sensitivity, the resonant film and piezoelectric components are usually thin and cannot withstand the axial stress caused by large pressure. The above structure solves this problem, improves the pressure-bearing capacity of the structure, expands the pressure detection range, and ensures the linearity of the structure in the pressure measurement range.

[0026] In some examples, an anchor point for transmitting stress is provided between the resonant cavity and the pressure cavity, and the anchor point is provided on the buried oxide layer. External pressure can act on the pressure sensitive film and be transmitted to the resonant film through the anchor point.

[0027] When pressure acts on the pressure chamber, there is a certain gap between the pressure chamber and the resonance chamber. The solid part of the gap can form an anchor point for pressure transmission. The pressure is transmitted to the resonance film and the piezoelectric component through the anchor point, and then stress is formed on the resonance film and the piezoelectric component.

[0028] In some examples, the thickness of the device layer is a first preset thickness, which is the thickness of the resonant film, and the thickness of the buried oxide layer is a second preset thickness, which is the thickness of the pressure sensitive film.

[0029] The thickness of the device layer can be the same as the thickness of the resonant film. The resonant film is a part of the device layer, and a device layer of corresponding thickness can be processed on the SOI wafer through precise micromachining technology. Similarly, the thickness of the buried oxide layer can be the same as the thickness of the pressure sensitive film. The pressure sensitive film is a part of the buried oxide layer, and a buried oxide layer of corresponding thickness can be processed on the SOI wafer through precise micromachining technology.

[0030] In some examples, a cover is provided on a side of the piezoelectric component facing away from the resonant component, and the cover and the piezoelectric component enclose a sealed cavity; and / or,

[0031] A protection structure is arranged on a side of the piezoelectric component away from the resonance component, and the protection structure covers the surface of the piezoelectric component.

[0032] The side of the piezoelectric component facing away from the device layer is equipped with a cover. The cover and the piezoelectric component together enclose a sealed cavity, which can be set as a vacuum cavity or a cavity with a specific medium, such as nitrogen, ammonia, xenon, etc. This sealing structure ensures that the piezoelectric component is not disturbed by the external environment during operation, such as dust, moisture or other impurities that may affect its performance. This setting not only extends the service life of the piezoelectric component, but also ensures the stability of its performance, thereby improving the reliability and durability of the entire piezoelectric resonant pressure sensor.

[0033] The pressure inside the sealed cavity and the pressure inside the pressure cavity may have a certain pressure difference, and the pressure value received by the pressure cavity can be calculated more accurately by calculating the absolute pressure difference or the relative pressure difference. Among them, the absolute pressure difference refers to when the sealed cavity is a vacuum cavity, the pressure value inside the sealed cavity is zero, and the piezoelectric resonant pressure sensor detects the pressure cavity, that is, the pressure value received by the pressure cavity, and has a faster detection efficiency. The relative pressure difference refers to when the sealed cavity is a cavity with a specific pressure, at which time there is a medium in the sealed cavity and the pressure is maintained at a certain value. The piezoelectric resonant pressure sensor detects the pressure cavity and needs to subtract the pressure value inside the sealed cavity to obtain the pressure value received by the pressure cavity. This sealed cavity has higher adaptability.

[0034] In a second aspect, the present application provides a pressure compensation system for a piezoelectric resonant pressure sensor, comprising:

[0035] At least one piezoelectric resonant pressure sensor as described above; and

[0036] At least one compensation sensor, wherein the compensation sensor is spaced apart from or integrated with the piezoelectric resonant pressure sensor;

[0037] The compensation sensor can receive ambient pressure, and the piezoelectric resonant pressure sensor can receive the pressure to be measured and the ambient pressure. The value of the pressure to be measured can be obtained by subtracting the detection value of the compensation sensor from the detection value of the piezoelectric resonant pressure sensor.

[0038] The compensation sensor can receive the ambient pressure, the piezoelectric resonant pressure sensor can receive the pressure to be measured and the ambient pressure, and the value of the pressure to be measured can be obtained by subtracting the detection value of the compensation sensor from the detection value of the piezoelectric resonant pressure sensor.

[0039] The compensation sensor will be affected by the environment, and the piezoelectric resonant pressure sensor can receive the pressure to be measured and will also be affected by the same environment. The value of the pressure to be measured can be obtained by subtracting the detection value of the compensation sensor from the detection value of the piezoelectric resonant pressure sensor.

[0040] In order to achieve the goal of accurately measuring pressure, a piezoelectric resonant pressure sensor with higher accuracy is set up. This piezoelectric resonant pressure sensor can accurately capture and measure pressure changes in various environments. However, environmental factors themselves may interfere with the sensor, resulting in deviations in the measurement results. In order to solve this problem, the present application proposes a pressure compensation system, which eliminates the interference of environmental influences on the measurement results by introducing a compensation sensor.

[0041] In a third aspect, the present application provides a method for preparing a piezoelectric resonant pressure sensor, which is applicable to the above-mentioned piezoelectric resonant pressure sensor; the method is used to process an SOI wafer into the piezoelectric resonant pressure sensor, and the method comprises:

[0042] Take an SOI wafer, set the thickness of the buried oxide layer to the thickness of the pressure sensitive film, and set the thickness of the device layer to the thickness of the resonance film;

[0043] The above steps are the preparation of materials, which are ready for the subsequent preparation process. Specifically, the SOI wafer has a unique three-layer structure, including a substrate layer, a buried oxide layer, and a device layer. During the preparation process, the thickness of the buried oxide layer and the device layer will be accurately set according to the performance requirements of the sensor. Specifically, the thickness of the buried oxide layer is set to the thickness of the pressure sensitive film, and at the same time, the thickness of the device layer is set to the thickness of the resonant film.

[0044] depositing and processing the piezoelectric component on the device layer;

[0045] The above steps can deposit and process the piezoelectric component on the device layer. The piezoelectric component is the core part of the piezoelectric resonant pressure sensor, and its performance directly affects the overall performance of the sensor. The first electrode layer, the piezoelectric layer, and the second electrode layer can be deposited on the device layer at one time, and a seed layer can be deposited before depositing the first electrode to ensure the quality of the piezoelectric layer.

[0046] At least one resonant cavity is opened on the buried oxide layer by means of a sacrificial layer;

[0047] After the piezoelectric component is processed, at least one resonant cavity can be opened on the buried oxide layer by a sacrificial layer method. The opening of the resonant cavity is important for realizing the resonant characteristics of the piezoelectric resonant pressure sensor, and can reserve a resonant space for the resonant film.

[0048] The pressure chamber is opened on the substrate layer.

[0049] A pressure cavity is opened on the substrate layer, and a cover is bonded on the position of the piezoelectric component, so that a complete piezoelectric resonant pressure sensor can be formed. The opening of the pressure cavity enables the sensor to exchange pressure with the external environment, thereby realizing the measurement of pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions in the present application or the prior art, the drawings required for use in the examples or prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some examples of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0051] Figure 1 This is a schematic diagram of the structure of a piezoelectric resonant pressure sensor in an example of the present application;

[0052] Figure 2 This is a schematic diagram of the structure of a piezoelectric resonant pressure sensor in an example of the present application when there is no cover;

[0053] Figure 3 A schematic diagram of a top view of the structure of a piezoelectric resonant pressure sensor in an example of the present application without a cover;

[0054] Figure 4 For this application, an example Figure 3 Schematic diagram of the cross-sectional view of the structure of the medium-pressure electric resonant pressure sensor in the AA direction when there is no cover;

[0055] Figure 5 For this application, an example Figure 3 Schematic diagram of the cross-sectional view of the structure of the medium-pressure electric resonant pressure sensor in the BB direction when there is no cover;

[0056] Figure 6 It is a schematic diagram of the structure of a piezoelectric resonant pressure sensor in an example of the present application when there is no cover and no lead electrode and protective layer;

[0057] Figure 7 It is a schematic diagram of a top view of another structure of a piezoelectric resonant pressure sensor in an example of the present application, in which lead electrodes and a protective layer are not provided;

[0058] Figure 8 It is a schematic diagram of a top view of another structure of a piezoelectric resonant pressure sensor in an example of the present application, in which lead electrodes and a protective layer are not provided;

[0059] Fig. 9 It is a schematic diagram of a top view of another structure of a piezoelectric resonant pressure sensor in an example of the present application, in which lead electrodes and a protective layer are not provided;

[0060] Fig.10 It is a schematic diagram of a top view of another structure of a piezoelectric resonant pressure sensor in an example of the present application, in which lead electrodes and a protective layer are not provided;

[0061] Fig.11It is a schematic diagram of a top view of another structure of a piezoelectric resonant pressure sensor in an example of the present application, in which lead electrodes and a protective layer are not provided;

[0062] Fig.12 It is a schematic diagram of a top view structure when a piezoelectric resonant pressure sensor in an example of the present application is applied to a pressure compensation system without lead electrodes and a protective layer;

[0063] Fig.13 It is a top view schematic diagram of another structure of the piezoelectric resonant pressure sensor in an example of the present application when it is applied to a pressure compensation system without the lead electrode and the protective layer;

[0064] Fig.14 A schematic diagram of a process for preparing a piezoelectric resonant pressure sensor in an example of the present application;

[0065] Fig.15 This is a schematic diagram of the structure of an unprocessed SOI wafer in an example of the present application;

[0066] Fig.16 This is a schematic diagram of the structure when a piezoelectric component is deposited on a device layer in an SOI wafer in an example of the present application;

[0067] Fig.17 This is a schematic diagram of a structure in which a piezoelectric component is deposited on one side away from the device layer and the second electrode layer is etched in an example of the present application;

[0068] Fig.18 This is a schematic diagram of a structure in which a protective structure is provided on the outside of a piezoelectric component in an example of the present application;

[0069] Fig.19 When a protective structure is set on the outside of the piezoelectric component in an example of the present application and the viewing angle is switched to the Figure 3 Schematic diagram of the structure in the middle BB direction;

[0070] Fig. 20 This is a schematic diagram of a structure in which a connecting channel is provided on the second electrode layer of a piezoelectric component in an example of the present application;

[0071] Fig.21 This is a schematic diagram of a structure in which a connecting channel is provided on the first electrode layer of a piezoelectric component in an example of the present application;

[0072] Fig. 22 This is a schematic diagram of the structure when a top layer of metal is deposited after connecting channels are respectively opened on the first electrode layer and the second electrode layer in a piezoelectric component in an example of the present application;

[0073] Fig.23 A schematic diagram of the structure of a piezoelectric component in an example of the present application after patterning the top metal layer;

[0074] Fig.24 When a protective structure is set on the outside of the piezoelectric component in an example of the present application and the viewing angle is switched to the Figure 3 Schematic diagram of the structure in the AA direction;

[0075] Fig.25 A schematic diagram of the structure of a SOI wafer in an example of the present application in which a resonant cavity is opened by using a sacrificial layer processing method in an oxide buried layer;

[0076] Fig.26 This is a schematic diagram of the structure after a pressure cavity is opened on the side of the substrate layer facing away from the piezoelectric component in an example of the present application;

[0077] Fig. 27 This is a schematic diagram of the structure of the cover before processing in an example of the present application;

[0078] Fig.28 This is a schematic diagram of the structure of the cover after molding in an example of the present application;

[0079] Fig.29 This is a schematic diagram of the structure after the cover is installed in an example of the present application;

[0080] Fig.30 This is a structural schematic diagram of a piezoelectric resonant pressure sensor in an example of the present application when a cover is provided but no protective structure is provided.

[0081] Reference numerals:

[0082] 10. Piezoelectric resonant pressure sensor; 20. Compensation sensor; 100. Piezoelectric component; 110. First electrode layer; 120. Piezoelectric layer; 130. Second electrode layer; 140. First electrode structure; 150. Second electrode structure; 200. Resonance component; 210. Device layer; 211. Resonance film; 220. Buried oxide layer; 221. Resonance cavity; 222. Pressure sensitive film; 230. Substrate layer; 231. Pressure cavity; 240. Anchor point; 500. Cover; 600. Protection structure. DETAILED DESCRIPTION

[0083] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and examples. It should be understood that the specific examples described here are only used to explain the present application and are not used to limit the present application.

[0084] In the piezoelectric resonant pressure sensor of the related art, the piezoelectric resonant pressure sensor can be miniaturized and then applied to micro-electromechanical systems (MEMS), which are micro-systems that integrate micron-level mechanical devices, integrated circuits, sensors, actuators, and signal processing and control circuits on one or more chips. The size of such a system is usually only a few millimeters or even smaller.

[0085] Due to the use of micromachining technology, MEMS technology can mass-produce various micro sensors, actuators, micro components and micro machines. These micro devices have the characteristics of small size, light weight, low power consumption, stable performance, high reliability, high integration, intelligence, large production batch, low cost, and easy large-scale production. Therefore, they are widely used in aviation, aerospace, automobile, biomedicine, environmental monitoring, military and other fields.

[0086] As an important measuring tool, the accuracy and response speed of piezoelectric resonant pressure sensor are crucial for many applications. In recent years, with the increasing demand for miniaturization and mass production, new piezoelectric resonant pressure sensor arrangements have emerged. The present application discloses a piezoelectric resonant pressure sensor arrangement combining a piezoelectric component and a resonant structure.

[0087] To achieve the above purpose, please refer to Figure 1-Figure 30 As shown, the first aspect of the present application proposes a piezoelectric resonant pressure sensor 10, which can make the piezoelectric resonant pressure sensor have a greater tolerance and thus a larger pressure detection range. Also, due to the relatively simple structure, it is easier to achieve miniaturization and mass production.

[0088] The piezoelectric resonant pressure sensor mentioned in the example of this application can be combined with MEMS technology to achieve mass production of piezoelectric resonant pressure sensors and improve the production efficiency of piezoelectric resonant pressure sensors.

[0089] The piezoelectric resonant pressure sensor mentioned in the example of this application can output a corresponding electrical signal based on the received pressure to be detected, and is a sensitive element.

[0090] The piezoelectric resonant pressure sensor 10 can use a thicker pressure-sensitive film 222 to sense pressure, and then convert it into stress on the piezoelectric resonator through the anchor point 240. The piezoelectric stack of the piezoelectric resonator is generally thin and cannot withstand the axial stress caused by a large pressure. The above structure solves this problem, improves the pressure-bearing capacity of the structure, expands the pressure detection range, and ensures the linearity of the structure within the pressure measurement range. At the same time, the anchor point 240 can also be used as a lever to amplify the stress generated by the pressure and improve sensitivity. The above arrangement allows piezoelectric resonant pressure sensors to be widely used in the core technology field of the electronics industry.

[0091] In the present application, the anchor point 240 refers to the area where the pressure sensitive film 222 and the resonant film 211 are connected. The external pressure acting on the pressure sensitive film 222 can be transmitted to the anchor point 240 during the deformation of the pressure sensitive film 222, and act on the resonant film 211 through the anchor point 240. During the transmission process, the external pressure can be dispersed through the anchor point 240, thereby improving the pressure bearing capacity of the pressure chamber 231 and thus improving the pressure detection range. The piezoelectric resonator can be a combination of the device layer 210 and the piezoelectric component 100 in the present application.

[0092] Reference Figures 1 to 5 In some examples, the piezoelectric resonant pressure sensor 10 is applied to the core electronics industry. The piezoelectric resonant pressure sensor 10 includes a piezoelectric component 100 and a resonant component 200 .

[0093] The piezoelectric component 100 is directly or indirectly connected to an external circuit; the resonant component 200 is arranged on one side of the piezoelectric component 100, and the resonant component 200 is made of an SOI wafer, and the SOI wafer includes a device layer 210, a buried oxide layer 220 and a substrate layer 230 connected in sequence; the device layer 210 is connected to the piezoelectric component 100, and at least one resonant cavity 221 is arranged in the buried oxide layer 220, and a pressure cavity 231 is opened on the side of the substrate layer 230 away from the device layer 210, and the external pressure received by the pressure cavity 231 can be transmitted to the device layer 210; in the direction of the resonant component 200 away from the piezoelectric component 100, the projection of at least one resonant cavity 221 is outside the projection of the pressure cavity 231.

[0094] In the above structure, the pressure cavity 231 can be opened on the buried oxide layer 220 or the substrate layer 230, and a pressure sensitive film 222 can be formed. The setting of the resonant cavity 221 can form a resonant film 211 on the device layer 210. The pressure sensitive film 222 can be stacked on part of the device layer 210 and part of the piezoelectric component 100 to form a film structure with a higher thickness and a pressure sensitive function. At this time, the thicker pressure sensitive film 222 directly bears the pressure, and the stress transmitted to the resonant film 211 and the piezoelectric component 100 through the side of the resonant cavity 221 and the integrated stacked structure on the entire pressure sensitive film 222 is converted into stress on the resonant film 211 and the piezoelectric component 100. In order to ensure sensitivity, the resonant film 211 and the piezoelectric component 100 are usually thin and cannot withstand the axial stress caused by a large pressure. The above structure solves this problem, improves the pressure bearing capacity of the structure, expands the pressure detection range, and ensures the linearity of the structure in the pressure measurement range. Furthermore, since the structure of the piezoelectric resonant pressure sensor 10 of the present application is integrated into one body through the MEMS process, it can be more easily miniaturized and mass-produced.

[0095] The piezoelectric resonant pressure sensor 10 is mainly composed of a piezoelectric component 100 and a resonant component 200, wherein the resonant component 200 is formed by processing an SOI wafer, and the resonant component 200 includes three parts: a device layer 210, a buried oxide layer 220, and a substrate layer 230. The piezoelectric component 100 can be used as the core part of the piezoelectric resonant pressure sensor 10, and is used to drive the resonator to vibrate and detect the frequency change of the resonator caused by the pressure to be measured. The above driving and detection are based on the piezoelectric effect. The piezoelectric component 100 is connected to the external circuit directly or indirectly to realize signal transmission and processing. The device layer 210 is the main part that generates resonance, and the pressure chamber 231 is used to receive external pressure and transmit the external pressure to the resonant film 211 on the device layer 210.

[0096] The device layer 210, the buried oxide layer 220 and the substrate layer 230 are integrally arranged. The device layer 210 can be connected to the piezoelectric component 100 to form the core structure (piezoelectric resonator) of the sensor. The buried oxide layer 220 and the substrate layer 230 are both arranged on the other side of the device layer 210 away from the piezoelectric component 100, and are responsible for sensing the change of the pressure to be measured. The above structure can enable the sensor to detect pressure by changing the resonant frequency of the device layer 210 when it is under pressure, thereby improving the measurement accuracy.

[0097] The resonant cavity 221 can be opened on the buried oxide layer 220, and the pressure cavity 231 can be opened on the substrate layer 230. The resonant cavity 221 is arranged on the side of the buried oxide layer 220 away from the device layer 210. The resonant cavity 221 is located around the resonant cavity 221 in the projection space, and the device layer 210 can close or not close the resonant cavity 221. The existence of the resonant cavity 221 is to ensure the normal operation of the device layer 210 and provide space for the movement of the device layer 210. The pressure cavity 231 is used to receive external pressure. When pressure acts on the pressure cavity 231, there is a certain interval between the pressure cavity 231 and the resonant cavity 221, and the solid part of the interval can form an anchor point 240 for pressure transmission. The pressure is transmitted to the resonant film 211 and the piezoelectric component 100 through the anchor point 240, and then stress is formed on the resonant film 211 and the piezoelectric component 100.

[0098] The function of the pressure chamber 231 is to provide the sensor with an environment in direct contact with the pressure to be measured, ensuring that the sensor can accurately sense the change of the pressure to be measured. The setting of the pressure chamber 231 needs to take into account factors such as the use environment, working temperature and pressure range of the sensor to ensure that it has good sealing and stability.

[0099] The resonant cavity 221 is matched with the device layer 210. The part of the device layer 210 located above the opening of the resonant cavity 221 can form a resonant film 211. The resonant film 211 is driven by the piezoelectric component 100 to resonate. When the pressure is transmitted to the resonant film 211 and the piezoelectric component 100 through the anchor point 240 structure, stress is formed on the resonant film 211 and the piezoelectric component 100. The stress will cause the resonant frequency of the resonant film 211 to change, and the change is detected by the piezoelectric component 100.

[0100] The device layer 210, the buried oxide layer 220 and the substrate layer 230 connected in sequence can form the resonant component 200 of the present application. The device layer 210 and the buried oxide layer 220 are the key parts of the resonance effect in the piezoelectric resonant pressure sensor 10. After at least one resonant cavity 221 is opened in the buried oxide layer 220, the resonant cavity 221, the device layer 210 and the piezoelectric component 100 together constitute a resonant system. When the pressure to be measured acts on the resonant component 200, the pressure to be measured is first transmitted to the pressure cavity 231, and then the pressure to be measured is transmitted to the resonant film 211 through the anchor point 240, and then transmitted to the piezoelectric component 100 by the resonant film 211. During the transmission process, the pressure to be measured is converted into stress on the resonant film 211 and stress on the piezoelectric component 100 in turn. When the pressure to be measured is transmitted to the resonance component 200, the resonance frequency of the resonance film 211 in the resonance component 200 will change. The piezoelectric component 100 uses the inverse piezoelectric effect to excite the resonance film 211 to vibrate, and at the same time uses the positive piezoelectric effect to detect the change in the resonance frequency of the resonance film 211, thereby detecting the value of the pressure to be measured, ensuring that the piezoelectric detection is carried out normally, and making the accuracy of the piezoelectric detection more accurate.

[0101] In the direction toward the pressure sensitive component, the projection of at least one resonant cavity 221 is located outside the projection of the pressure cavity 231. This arrangement cleverly utilizes the interaction between the resonant cavity 221 and the pressure cavity 231, so that the sensor can more sensitively capture pressure changes when subjected to pressure, thereby improving the measurement accuracy of the sensor. At least one resonant cavity 221 can also be partially arranged inside the projection of the pressure cavity 231.

[0102] The selection of the piezoelectric component 100 is important for the performance and stability of the sensor, so the selection of materials and processing technology can be carefully considered as needed during the setting and manufacturing process. The signal conversion part of the piezoelectric component 100 can be made of piezoelectric film materials, piezoelectric ceramics, polymer piezoelectric materials, nano piezoelectric materials and other materials to meet the needs of different application scenarios. It can be preferably a piezoelectric film material, which can be AlN, ScAlN, PZT, ZnO, LiNbO3, etc.

[0103] Reference Figure 4In some examples, the resonant cavity 221 is opened on the buried oxide layer 220 by means of a sacrificial layer.

[0104] The sacrificial layer method specifically refers to the process of releasing the sacrificial layer, which uses a removable material as a temporary support or isolation layer. After the main structure is built, this layer of "sacrificial" material is removed to obtain the desired final product. The process of releasing the sacrificial layer usually involves multiple steps, each of which can be precisely controlled to ensure the quality and performance of the final product. First, a suitable sacrificial layer material can be selected, which should have the characteristics of easy processing, good stability, and easy removal. Then, a sacrificial layer structure is formed on the substrate through precise coating, photolithography, etching and other technical means. Next, the required main structure is constructed on the sacrificial layer. This step usually involves the stacking of multiple layers of materials and the construction of fine graphics. After the main structure is built, the critical sacrificial layer removal step is entered. This step can use chemical corrosion, physical stripping or plasma etching to accurately remove the sacrificial layer material from the product without damaging the main structure. This process can be extremely finely controlled to ensure the thoroughness of removal and the integrity of the structure.

[0105] Reference Figure 4 and Figure 5 In some examples, part of the device layer 210 closes or does not close the resonant cavity 221 , and the part of the device layer 210 that closes the resonant cavity 221 is the resonant film 211 .

[0106] The device layer 210 may have certain vibration characteristics and energy conversion efficiency. The device layer 210 may be specifically formed by interconnecting a fixed portion and a resonant film 211. The device layer 210 may be able to excite the resonant film 211 to vibrate by utilizing the inverse piezoelectric effect through the piezoelectric component 100. When the resonant component 200 receives the pressure to be measured, it may cause the resonant frequency of the resonant film 211 in the resonant component 200 to change. The piezoelectric component 100 may excite the resonant film 211 to vibrate by utilizing the inverse piezoelectric effect and at the same time may detect the change in the resonant frequency of the resonant film 211 by utilizing the positive piezoelectric effect, thereby detecting the value of the pressure to be measured, and thereby ensuring the detection of the pressure to be measured.

[0107] The fixing portion is naturally formed during the processing of the device layer 210 , and the fixing portion can make the arrangement of the resonance film 211 more stable and reliable.

[0108] The resonant film 211 is the functional part of the device layer 210. The piezoelectric component 100 can use the inverse piezoelectric effect to excite the resonant film 211 to vibrate. The pressure to be measured can act on the pressure-sensitive film 222 and be transmitted to the resonant film 211 and the piezoelectric component 100 through the anchor point 240, and then converted into stress on the resonant film 211 and the piezoelectric component 100.

[0109] One side of the resonant film 211 is connected to the piezoelectric component 100 , and the other side of the resonant film 211 closes the opening of the resonant cavity 221 .

[0110] In some examples, the pressure cavity 231 may penetrate the substrate layer 230 , and a pressure sensitive film 222 is formed in a region of the buried oxide layer 220 corresponding to the pressure cavity 231 ;

[0111] At least one resonant cavity 221 is located on the peripheral side of the pressure sensitive film 222 . The pressure received by the pressure cavity 231 can act on the pressure sensitive film 222 and be transmitted to the device layer 210 .

[0112] At least one resonant cavity 221 may be arranged around the projection of the pressure cavity 231. When at least two resonant cavities 221 are arranged, more detection points may be provided, thereby improving the accuracy and stability of the measurement. When the pressure changes, the resonant films 211 corresponding to different resonant cavities 221 may produce corresponding resonant frequency changes, and these resonant films 211 may verify each other, thereby improving the accuracy of the measurement.

[0113] At least one resonant cavity 221 is located around the pressure sensitive film 222. The pressure received by the pressure cavity 231 can act on the pressure sensitive film 222 and be transmitted to the device layer 210. Specifically, the pressure received by the pressure cavity 231 can be transmitted to the resonant film 211 on the device layer 210 through the anchor point 240.

[0114] It should be understood that the pressure chamber 231 can completely penetrate the substrate layer 230, or only partially penetrate the substrate layer 230. Such a setting can form a channel that is in direct contact with the external environment. When the pressure to be measured changes, the corresponding gas or liquid in this channel will be subjected to the corresponding pressure. The setting of the buried oxide layer 220 can facilitate the processing of the pressure chamber 231. During the processing of the pressure chamber 231, the buried oxide layer 220 can be used to identify the processing depth of the pressure chamber 231.

[0115] The pressure chamber 231 may be a unidirectionally opened pressure groove, the bottom of the pressure groove may be located at a pressure-sensitive film 222, the pressure-sensitive film 222 may be a part of the device layer 210, the resonance chamber 221 may be arranged in the peripheral area of ​​the pressure-sensitive film 222, the pressure-sensitive film 222 may have a high sensitivity characteristic, the pressure-sensitive film 222 may transfer the pressure to be measured received in the pressure chamber 231 to the device layer 210, and drive the resonant frequency of the device layer 210 to change, the piezoelectric component 100 utilizes the inverse piezoelectric effect to excite the device layer 210 to vibrate, and utilizes the positive piezoelectric effect to detect the change in the resonant frequency of the device layer 210, and then detects the value of the pressure to be measured.

[0116] In the above structure, the pressure-sensitive film 222 can be used to overlap the thickness of the device layer 210, and the thicker pressure-sensitive film 222 can be used to sense the pressure. Then, the stress is transferred to the piezoelectric resonator through the membrane structure (anchor point 240 part) shared by the pressure-sensitive film 222 and the piezoelectric resonator. This solves the problem that the piezoelectric stack of the resonator is generally thin and cannot withstand the axial stress caused by a large pressure, improves the pressure-bearing capacity of the structure, expands the pressure detection range, and ensures the linearity of the structure within the pressure measurement range.

[0117] When the pressure chamber 231 receives the pressure to be measured, the pressure sensitive film 222 is acted upon by force and slightly deformed. In order to amplify the deformation and convert it into a measurable electrical signal, at least one resonant cavity 221 is provided on the circumference of the pressure sensitive film 222.

[0118] The region of the device layer 210 that closes the opening of the resonant cavity 221 may form a resonant film 211 , and a side of the resonant film 211 that faces away from the resonant cavity 221 is connected to the piezoelectric component 100 .

[0119] The above-mentioned resonant frequency change can be detected and recorded by connecting to the corresponding electronic measuring equipment through an external circuit breaker, thereby achieving accurate measurement of the pressure to be measured. In addition, the piezoelectric resonant pressure sensor 10 of the present application can be integrally formed using MEMS technology, which is convenient for mass production.

[0120] In addition, the piezoelectric resonant pressure sensor 10 of the present application also has a wide range of application prospects. It can play a huge role in the fields of industrial automation, aerospace, environmental monitoring, etc. For example, in industrial automation, the piezoelectric resonant pressure sensor 10 can be used to monitor the operating status of mechanical equipment, detect faults in time and issue early warnings; in aerospace, the piezoelectric resonant pressure sensor 10 can be used to measure the changes in air pressure of aircraft or rockets during flight, providing accurate data support for flight control; in environmental monitoring, the piezoelectric resonant pressure sensor 10 can be used to measure key parameters such as atmospheric pressure and water level, providing an important basis for environmental protection and weather forecasting.

[0121] The pressure-sensitive film 222 may also be formed after the pressure cavity 231 is opened in the resonance component 200 and the opening position is thinned. At this time, the pressure-sensitive film 222 may be only a part of the buried oxide layer 220, or it may be the mutual superposition of the buried oxide layer 220 and part of the substrate layer 230. The side of the pressure-sensitive film 222 facing away from the pressure cavity 231 is connected to the device layer 210, and the pressure received by the pressure cavity 231 can act on the pressure-sensitive film 222 and be transmitted to the device layer 210.

[0122] The setting and optimization of the resonance component 200 can improve the performance and accuracy of the piezoelectric resonant pressure sensor 10. In the piezoelectric resonant pressure sensor 10 of the present application, the pressure sensitive film 222 in the resonance component 200 can be combined with the resonance film 211 in the device layer 210 to achieve accurate perception and response to the pressure to be measured, thereby improving the performance of the piezoelectric resonant pressure sensor 10.

[0123] The main functional part of the resonance component 200 is the pressure sensitive film 222 . The pressure sensitive film 222 is the thinnest part of the resonance component 200 that corresponds to the pressure cavity 231 after the pressure cavity 231 is formed in the resonance component 200 .

[0124] The pressure sensitive film 222 can be deformed when subjected to external force, and the force direction will be changed during the deformation process, thereby transferring the deformation to the position of the resonance cavity 221, and then transferring the deformation to the resonance film 211, causing the resonance frequency of the resonance film 211 to change. The piezoelectric component 100 utilizes the inverse piezoelectric effect to excite the resonance film 211 to vibrate, and at the same time utilizes the direct piezoelectric effect to detect the change in the resonance frequency of the resonance film 211, thereby detecting the value of the pressure to be measured.

[0125] The pressure sensitive film 222 is placed at the position of the pressure cavity 231 so that the pressure applied by the outside can directly act on the pressure sensitive film 222. When the pressure sensitive film 222 is subjected to pressure, the pressure sensitive film 222 will undergo a slight deformation, which will then be transmitted to the device layer 210 connected to the pressure sensitive film 222, and then the pressure will be detected through the cooperation of the resonant cavity 221, the resonant film 211 and the piezoelectric component 100.

[0126] The device layer 210 can vibrate when stimulated by the outside world. The device layer 210 is connected to the pressure-sensitive film 222. Therefore, when the resonant film 211 and the pressure-sensitive film 222 are deformed, a certain stress will be generated on the resonant film 211, causing the resonant frequency of the device layer 210 to change. The resonant frequency changes mainly at the position of the resonant film 211 on the device layer 210. The resonant cavity 221 reserves enough space for the vibration of the resonant film 211. This change can be captured by the piezoelectric component 100 and converted into an electrical signal, thereby achieving accurate measurement of pressure.

[0127] In the present application, the pressure detection can be realized by utilizing the forward and reverse piezoelectric effects of the piezoelectric film material in the piezoelectric component 100. The reverse piezoelectric effect can be used to reversely drive the resonance film 211 on the device layer 210 to vibrate, and the forward piezoelectric effect can be used to detect the frequency parameters of the device layer 210.

[0128] The arrangement of the pressure sensitive film 222 combined with the device layer 210 also has many advantages. Since the pressure sensitive film 222 can directly sense the change of the pressure to be measured, this arrangement has higher performance and accuracy. Furthermore, since the device layer 210 can produce a change in vibration frequency after being pressurized, this arrangement can effectively reduce the influence of interference signals and improve the accuracy of measurement. In addition, the above arrangement also has good stability and reliability, and can operate stably for a long time in harsh environments.

[0129] In practical applications, the arrangement of the pressure sensitive film 222 combined with the device layer 210 is widely used in various fields. For example, in the field of industrial automation, the arrangement of the pressure sensitive film 222 combined with the device layer 210 can be used to achieve precise pressure control and monitoring, improve production efficiency and product quality. In automotive electronic systems, the arrangement of the pressure sensitive film 222 combined with the device layer 210 can be used to monitor the pressure and temperature of the tire, thereby improving driving safety and comfort. In medical equipment, the arrangement of the pressure sensitive film 222 combined with the device layer 210 can be used to monitor the patient's vital signs, such as blood pressure and heart rate.

[0130] The combination of the pressure sensitive film 222 and the device layer 210 is an efficient, accurate and stable pressure sensing technology, which can improve the performance and accuracy of traditional pressure sensitive devices and provide better technical support for various application fields.

[0131] In some examples, the pressure sensitive film 222 , the device layer 210 , and the piezoelectric assembly 100 are stacked on top of each other and receive external pressure together.

[0132] The above structure can form a thicker pressure sensitive film 222. The thicker pressure sensitive film 222 can directly bear the pressure, and the stress on the resonance film 211 and the piezoelectric component 100 is transferred to the resonance film 211 and the piezoelectric component 100 through the integrated laminated structure on the side of the resonance cavity 221 and the entire pressure sensitive film 222, and converted into stress on the resonance film 211 and the piezoelectric component 100. In order to ensure sensitivity, the resonance film 211 and the piezoelectric component 100 are usually thin and cannot withstand the axial stress caused by large pressure. The above structure solves this problem, improves the pressure bearing capacity of the structure, expands the pressure detection range, and ensures the linearity of the structure in the pressure measurement range.

[0133] In some examples, an anchor point 240 for transmitting stress is provided between the resonant cavity 221 and the pressure cavity 231 . The anchor point 240 is provided on the buried oxide layer 220 . External pressure can act on the pressure sensitive film 222 and be transmitted to the resonant film 211 through the anchor point 240 .

[0134] When pressure acts on the pressure chamber 231, there is a certain gap between the pressure chamber 231 and the resonance chamber 221. The solid part of the gap can form an anchor point 240 for pressure transmission. The pressure is transmitted to the resonance film 211 and the piezoelectric component 100 through the anchor point 240, and then stress is formed on the resonance film 211 and the piezoelectric component 100.

[0135] Specifically, when the pressure to be measured acts on the resonant component 200, the pressure first directly acts on the pressure sensitive film 222, and then is transmitted to the resonant film 211 through the anchor point 240. The resonant film 211 can be deformed when subjected to pressure. The pressure to be measured is converted into stress on the film during the process of being transmitted to the resonant film 211.

[0136] Next, the stress on the resonant film 211 is further transmitted to the piezoelectric component 100. The piezoelectric component 100 is a device that can convert mechanical stress into an electrical signal, and this conversion process is achieved by using the piezoelectric effect. During the transmission process, the pressure to be measured is again converted into stress on the piezoelectric component 100, thereby generating an electrical signal related to the pressure to be measured.

[0137] During the transmission of the pressure to be measured, the resonance frequency of the resonant film 211 will change. The piezoelectric component 100 uses the inverse piezoelectric effect to excite the resonance film 211 to vibrate, and uses the direct piezoelectric effect to detect the change in the resonance frequency of the resonant film 211, thereby detecting the value of the pressure to be measured. The inverse piezoelectric effect refers to the phenomenon that piezoelectric materials deform under the action of an electric field. The piezoelectric component 100 can be stimulated to resonate by applying an electric field, thereby further detecting the pressure to be measured.

[0138] In some examples, the thickness of the device layer 210 is a first preset thickness, which is the thickness of the resonant film 211 , and the thickness of the buried oxide layer 220 is a second preset thickness, which is the thickness of the pressure sensitive film 222 .

[0139] The thickness of the device layer 210 can be the same as that of the resonant film 211. The resonant film 211 is a part of the device layer 210. The device layer 210 of corresponding thickness can be processed on the SOI wafer by precise micro-machining technology. Similarly, the thickness of the buried oxide layer 220 can be the same as that of the pressure sensitive film. The pressure sensitive film 222 is a part of the buried oxide layer 220. The buried oxide layer 220 of corresponding thickness can be processed on the SOI wafer by precise micro-machining technology.

[0140] The thicknesses of the device layer 210 and the buried oxide layer 220 in the SOI wafer can be strictly controlled. The thickness of the device layer 210 can be set to a first preset thickness, and the thickness of the buried oxide layer 220 can be set to a second preset thickness.

[0141] In the present application, the opening positions of the pressure chamber 231 and the resonance chamber 221 in the SOI wafer are staggered, rather than being on the same horizontal line. The staggered positions can be used as anchor points 240 for transmitting stress, and the stress received on the pressure-sensitive film 222 can be better transmitted to the resonance film 211 through the anchor points 240. In the process of transmitting the pressure to be measured to the resonance component 200, the resonance frequency of the resonance film 211 in the resonance component 200 will change. The piezoelectric component 100 uses the inverse piezoelectric effect to excite the resonance film 211 to vibrate, and at the same time uses the positive piezoelectric effect to detect the change in the resonance frequency of the resonance film 211, thereby detecting the specific value of the pressure to be measured, ensuring that the piezoelectric detection is carried out normally, and making the accuracy of the piezoelectric detection more accurate.

[0142] In some examples, a cover 500 is disposed on a side of the piezoelectric component 100 facing away from the resonance component 200, and the cover 500 and the piezoelectric component 100 form a sealed cavity; and / or,

[0143] A protection structure 600 is disposed on the side of the piezoelectric component 100 facing away from the resonance component 200 . The protection structure 600 covers the surface of the piezoelectric component 100 .

[0144] The side of the piezoelectric component 100 facing away from the device layer 210 is provided with a cover 500. The cover 500 and the piezoelectric component 100 together enclose a sealed cavity, which can be set as a vacuum cavity or a cavity with a specific medium, such as nitrogen, ammonia, xenon, etc. This sealing structure ensures that the piezoelectric component 100 is not disturbed by the external environment during operation, such as dust, moisture or other impurities that may affect its performance. This setting not only extends the service life of the piezoelectric component 100, but also ensures the stability of its performance, thereby improving the reliability and durability of the entire piezoelectric resonant pressure sensor 10.

[0145] The pressure in the sealed cavity and the pressure in the pressure cavity 231 may have a certain pressure difference, and an absolute pressure or relative pressure sensor may be formed by calculating the absolute pressure difference or the relative pressure difference. Among them, the absolute pressure difference means that when the sealed cavity is a vacuum cavity, the pressure value in the sealed cavity is zero, and the detection value of the pressure cavity 231 by the piezoelectric resonant pressure sensor 10 is the pressure value received by the pressure cavity 231. At this time, the sensor is an absolute pressure sensor. The relative pressure difference means that the sealed cavity is a cavity with a specific pressure. At this time, there is a medium in the sealed cavity and the pressure is maintained at a certain value. The detection value of the pressure cavity 231 by the piezoelectric resonant pressure sensor 10 needs to be subtracted from the pressure value in the sealed cavity to obtain the pressure value received by the pressure cavity 231. At this time, the sensor is a relative pressure sensor.

[0146] In addition to the cover 500, some arrangements may also provide a protective structure 600 on the side of the piezoelectric component 100 that is away from the device layer 210. This protective structure 600 can cover the surface of the piezoelectric component 100 to provide additional protection for the piezoelectric component 100. This arrangement is mainly intended to cope with some extreme working environments, such as high temperature, high pressure or strong electromagnetic fields. Under these environments, the piezoelectric component 100 may be severely damaged, resulting in degradation of its performance or failure. The presence of the protective structure 600 can resist these adverse factors to a certain extent and protect the piezoelectric component 100 from damage. By reasonably selecting materials, the protective structure 600 can also have functions such as temperature compensation.

[0147] In general, both the cover 500 and the protective structure 600 are used to protect the piezoelectric component 100 and ensure that it can work stably and reliably in a harsh working environment. The cover 500 and the protective structure 600 may also be provided at the same time as needed.

[0148] The piezoelectric component 100 may include a first electrode layer 110, a piezoelectric layer 120 and a second electrode layer 130 from bottom to top. The second electrode layer 130 may be partially etched, leaving only a partial structure to match the first electrode layer 110. At least one first electrode structure 140 may penetrate the piezoelectric layer 120 and be connected to the first electrode layer 110, and the first electrode structure 140 is not in contact with the second electrode layer 130. The second electrode structure 150 may be connected to the second electrode layer 130.

[0149] When any of the second electrode structures 150 receives a voltage, stress is generated in the piezoelectric layer 120 based on the inverse piezoelectric effect of the piezoelectric layer 120. At this time, since the neutral layer of the piezoelectric layer 120 deviates from the geometric center position of the piezoelectric layer 120, the piezoelectric layer 120 will be deformed, and the deformation of the piezoelectric layer 120 drives the entire piezoelectric resonator to deform.

[0150] When an alternating voltage having the same resonant frequency as the piezoelectric resonator is applied to any second electrode structure 150, the entire structure will resonate, and the resonant frequency is:

[0151]

[0152] In the formula, f r is the resonant frequency, μ n are the constants set when solving the Bessel function, t is the thickness, r is the radius, E is the Young's modulus, ρ is the density, and δ is the Poisson's ratio.

[0153] When the pressure chamber 231 receives the pressure to be detected, the pressure sensitive film 222 will be deformed and generate working stress under the action of the pressure to be detected. The anchor point 240 can transmit the deformation and working stress of the pressure sensitive film 222 to the piezoelectric resonator, specifically to the piezoelectric layer 120. During the transmission process of the anchor point 240, the anchor point 240 can change the direction of action of the pressure to be detected, thereby reducing the possibility of damage to the resonant film 211.

[0154] The piezoelectric resonator may be provided with at least two second electrode structures 150, and when one of the second electrode structures 150 drives the piezoelectric layer 120 to vibrate, the other second electrode structure 150 detects the vibration of the piezoelectric resonator. The second electrode structure 150 that receives the voltage may be a driving electrode, and the second electrode structure 150 that detects the vibration may be a detection electrode.

[0155] Due to the positive piezoelectric effect of the piezoelectric film material, the detection electrode will generate an electrical signal, which can be used to detect the resonant frequency of the piezoelectric resonator.

[0156] Assume that the working stress generated by the pressure to be detected on the piezoelectric resonator is σ, and the resonant frequency of the piezoelectric resonator is:

[0157]

[0158] From the above formula, it can be seen that the pressure value can be determined when the frequency change of the piezoelectric resonator is detected.

[0159] When the piezoelectric layer 120 is deformed, the portion of the piezoelectric layer 120 close to the device layer 210 is squeezed by the pressure to be detected, and the portion of the piezoelectric layer 120 away from the device layer 210 is stretched by the pressure to be detected. On the cross section of the piezoelectric layer 120, the buried oxide layer 220 between the stretched portion of the piezoelectric layer 120 and the squeezed portion of the piezoelectric layer 120, which is neither stretched nor compressed and has almost zero stress, is the neutral layer mentioned above.

[0160] Compared with the resistance detection type piezoelectric sensor which needs to set up a Wheatstone bridge and the capacitance detection type pressure sensor which needs to set up a capacitance bridge, the piezoelectric resonant pressure sensor 10 provided in the example of the present application does not require the setting of an additional detection circuit, has a simpler structure, and has a lower manufacturing cost.

[0161] In some examples, the piezoelectric assembly includes at least one piezoelectric detection structure, which can be directly or indirectly connected to the external circuit, and one piezoelectric detection structure is arranged at a position corresponding to each resonant cavity. Each piezoelectric detection structure includes a group of second electrode structures 150 and at least one first electrode structure 140.

[0162] The shape and pattern of the piezoelectric detection structure corresponding to the surface of the piezoelectric component 100 can be set as needed. Figures 7 to 11 The schematic diagrams show five configurations of the piezoelectric component 100 facing away from the resonant component 200. The piezoelectric component 100 of the present application is not limited to the above five configurations.

[0163] in, Figure 6 It is a three-dimensional schematic diagram of a pressure sensitive device (a combination of a piezoelectric component 100 and a resonant component 200) before the lead electrodes and the oxide structure layer (protective structure 600) are deposited. Figure 7 For Figure 6 In the corresponding top view, the resonant cavity 2211 in this embodiment is a square cavity (a cavity with a cubic structure). In this figure, four groups of second electrode structures 150 are provided, and each group of second electrode structures 150 includes an excitation electrode (driving electrode) and a detection electrode. Each group of second electrode structures 150 corresponds to a resonant cavity 2211. Figure 6 and Figure 7 In the figure, four resonant cavities 2211 are used as an example for illustrative description. The present application may also set other numbers of resonant cavities 2211. Figure 8 The piezoelectric resonant pressure sensor 10 structure with a circular cavity (a cylindrical cavity) is shown in FIG. Figure 6 similar.

[0164] Fig. 9 FIG. 2 shows the structure of a piezoelectric resonant pressure sensor 10 having a circular ring cavity. Fig.10 2 shows the structure of a piezoelectric resonant pressure sensor 10 having a beam structure. Fig.11 , a piezoelectric resonant pressure sensor 10 having a beam structure and a stress concentration structure is shown.

[0165] Reference Fig.12 and Fig.13 In a second aspect, the present application provides a pressure compensation system for a piezoelectric resonant pressure sensor 10, comprising:

[0166] At least one piezoelectric resonant pressure sensor 10 as described above; and

[0167] At least one compensation sensor 20, the compensation sensor 20 and the piezoelectric resonant pressure sensor 10 are spaced apart or integrally arranged;

[0168] The compensation sensor 20 can receive the ambient pressure, and the piezoelectric resonant pressure sensor 10 can receive the pressure to be measured and the ambient pressure. The value of the pressure to be measured can be obtained by subtracting the detection value of the compensation sensor 20 from the detection value of the piezoelectric resonant pressure sensor 10.

[0169] The compensation sensor 20 can receive the ambient pressure, and the piezoelectric resonant pressure sensor 10 can receive the pressure to be measured and the ambient pressure. The value of the pressure to be measured can be obtained by subtracting the detection value of the compensation sensor 20 from the detection value of the piezoelectric resonant pressure sensor 10.

[0170] The compensation sensor 20 will be affected by the environment, and the piezoelectric resonant pressure sensor 10 can receive the pressure to be measured and will also be affected by the same environment. The detection value of the piezoelectric resonant pressure sensor 10 minus the detection value of the compensation sensor 20 can obtain the value of the pressure to be measured.

[0171] In order to achieve the goal of accurately measuring pressure, a piezoelectric resonant pressure sensor 10 with higher accuracy is provided, which can accurately capture and measure pressure changes in various environments. However, environmental factors themselves may interfere with the sensor, resulting in deviations in the measurement results. In order to solve this problem, the present application proposes a pressure compensation system, which eliminates the interference of environmental influences on the measurement results by introducing a compensation sensor 20.

[0172] The pressure compensation system mainly includes two key parts: a piezoelectric resonant pressure sensor 10 and at least one compensation sensor 20. The piezoelectric resonant pressure sensor 10 is responsible for receiving the pressure to be measured. The piezoelectric resonant pressure sensor 10 will simultaneously detect the sum of the value of the pressure to be measured and the interference value of the surrounding environment. The compensation sensor 20 can be specifically responsible for detecting the interference value after being affected by the environment, that is, the atmospheric pressure around the sensor or other external pressure that may affect the measurement result. The corresponding value detected by the compensation sensor 20 is the value affected by the surrounding environment. The above-mentioned environmental influencing factors include but are not limited to interference factors such as temperature and vibration.

[0173] In order to accurately measure the target pressure, the value of the pressure to be measured can be obtained by subtracting the value of the pressure to be measured from the value of the pressure to be measured from the value of the pressure to be measured, thereby obtaining an accurate value of the pressure to be measured.

[0174] The above two sensors can be set in two ways: interval setting or integrated setting. In the interval setting, the piezoelectric resonant pressure sensor 10 and the compensation sensor 20 are placed in different positions to ensure that the two sensors receive corresponding pressures respectively. For example, the piezoelectric resonant pressure sensor 10 can measure the addition value (the directions of the two forces are the same) or subtraction value (the directions of the two forces are opposite) of the pressure value to be measured and the environmental interference value. The pressure value to be measured and the environmental interference value are both detections of the sensor in a specific direction, and the direction of the force is generally the same or opposite. The compensation sensor 20 can measure the interference value of the environmental influence alone. This setting method can obtain a more accurate pressure value to be measured through simple calculations.

[0175] In an integrated setup, the two sensors are integrated into the same device. This setup can make the environmental influences on the two sensors more consistent, further improving measurement accuracy.

[0176] Regardless of the setting method, the measurement data of the piezoelectric resonant pressure sensor 10 and the compensation sensor 20 will be sent to a processing unit. Taking the example that the piezoelectric resonant pressure sensor 10 can measure the sum of the pressure value to be measured and the environmental interference value, in this processing unit, the detection value of the piezoelectric resonant pressure sensor 10 will be subtracted from the detection value of the compensation sensor 20, so as to obtain the accurate pressure value to be measured. In this way, the compensation system can eliminate the influence of environmental influence on the measurement results and improve the accuracy and reliability of the measurement.

[0177] It is worth noting that the above pressure compensation system is not only applicable to static pressure measurement, but also to dynamic pressure measurement. For example, in the field of aerospace, an aircraft will experience various complex airflow pressure and temperature changes during flight. This pressure compensation system can ensure that the piezoelectric resonant pressure sensor 10 on the aircraft can accurately measure the internal pressure, thereby providing important protection for flight safety.

[0178] The pressure compensation system also has a wide range of application prospects. In the medical field, the pressure compensation system can be used to monitor the patient's blood pressure, intracranial pressure and other physiological parameters, providing an important basis for diagnosis and treatment. In the field of environmental monitoring, the pressure compensation system can be used to measure environmental parameters such as atmospheric pressure and underwater pressure, providing data support for environmental protection and climate change research.

[0179] In a third aspect, the present application provides a method for preparing a piezoelectric resonant pressure sensor 10, which is applicable to the above-mentioned piezoelectric resonant pressure sensor 10; the following processing method can be completed by MEMS processing equipment. The method is used to process an SOI wafer into a piezoelectric resonant pressure sensor 10, and the SOI wafer can be processed into a resonant component 200 alone. The above method includes:

[0180] Step 100: Take an SOI wafer, set the thickness of the buried oxide layer 220 to be the same as the thickness of the pressure sensitive film 222, and set the thickness of the device layer 210 to be the same as the thickness of the resonance film 211;

[0181] The above steps are the preparation of materials, which are ready for the subsequent preparation process. Specifically, the SOI wafer has a unique three-layer structure, including a substrate layer 230, a buried oxide layer 220, and a device layer 210. During the preparation process, the thickness of the buried oxide layer 220 and the device layer 210 will be accurately set according to the performance requirements of the sensor. Specifically, the thickness of the buried oxide layer 220 is set to the thickness of the pressure sensitive film 222, and at the same time, the thickness of the device layer 210 is set to the thickness of the resonance film 211.

[0182] Step 200: depositing and processing the piezoelectric component 100 on the device layer 210;

[0183] The above steps can deposit and process the piezoelectric component 100 on the device layer 210. The piezoelectric component 100 is the core part of the piezoelectric resonant pressure sensor 10, and its performance directly affects the overall performance of the sensor. The first electrode layer 110, the piezoelectric layer 120, and the second electrode layer 130 can be deposited on the device layer 210 at one time, and a seed layer can be deposited before depositing the first electrode to ensure the quality of the piezoelectric layer 120.

[0184] Step 300: Opening at least one resonant cavity 221 on the buried oxide layer 220 by means of a sacrificial layer;

[0185] After the piezoelectric component 100 is processed, at least one resonant cavity 221 can be opened on the buried oxide layer 220 by a sacrificial layer method. The opening of the resonant cavity 221 is important for realizing the resonant characteristics of the piezoelectric resonant pressure sensor 10, and can reserve a resonant space for the resonant film 211.

[0186] Step 400 : Open a pressure chamber 231 on the substrate layer 230 .

[0187] A pressure cavity 231 is formed on the substrate layer 230, and a cover 500 is bonded to the position of the piezoelectric component 100, so that a complete piezoelectric resonant pressure sensor 10 can be formed. The pressure cavity 231 enables the sensor to exchange pressure with the external environment, thereby realizing pressure measurement.

[0188] Through the above series of processing steps, a piezoelectric resonant pressure sensor 10 with sufficient performance can be prepared. The sensor has the advantages of high precision, high sensitivity, good stability, etc., and can meet the pressure measurement requirements in various complex environments. In addition, the preparation method also has the characteristics of simple operation and low cost.

[0189] This application Figures 14 to 30The complete process of preparing the piezoelectric resonant pressure sensor 10 in an example of the present application is shown in detail. Through these diagrams, the specific operation and structural changes of each step can be clearly seen, so as to have a deeper understanding of the preparation process of the piezoelectric resonant pressure sensor 10.

[0190] Specifically, Fig.14 The schematic diagram of the process of preparing the piezoelectric resonant pressure sensor 10 is shown; as can be seen from the figure, the preparation process mainly includes the steps of SOI wafer processing, piezoelectric component 100 deposition, electrode layer etching, protection structure 600 setting, connecting channel opening, top metal deposition and patterning, and cover 500 processing. These steps are interrelated and together constitute the preparation process of the piezoelectric resonant pressure sensor 10.

[0191] Fig.15 The schematic diagram of the structure of an unprocessed SOI wafer is shown; the SOI wafer is composed of a substrate layer 230, a buried oxide layer 220 and a device layer 210, which provides a basis for the subsequent deposition of the piezoelectric component 100.

[0192] Fig.16 The schematic diagram of the structure of the piezoelectric component 100 when deposited on the device layer 210 in the SOI wafer is shown; the piezoelectric material is deposited on the device layer 210 through a specific process method to form the preliminary structure of the piezoelectric component 100.

[0193] Fig.17 A schematic diagram of the structure is shown in which the piezoelectric component 100 is deposited on one side away from the device layer 210 and the second electrode layer 130 is etched; through the etching process, the second electrode layer 130 is processed into a specific shape and size to meet the performance requirements of the piezoelectric resonant pressure sensor 10.

[0194] Fig.18 It shows a structural schematic diagram when a protective structure 600 is arranged outside the piezoelectric component 100; Fig.19 The protective structure 600 is set outside the piezoelectric component 100 and the viewing angle is switched to the Figure 3 Schematic diagram of the structure in the BB direction; the setting of the protection structure 600 can effectively protect the piezoelectric component 100 from the influence of the external environment and improve the stability and reliability of the sensor.

[0195] Fig. 20 It shows a schematic structural diagram of a piezoelectric component 100 in which a communication channel is provided on the second electrode layer 130; Fig.21 The schematic diagram shows the structure of the piezoelectric component 100 when a connecting channel is opened on the first electrode layer 110; the opening of the connecting channel helps to achieve the connection between the piezoelectric component 100 and the external environment, which is convenient for the signal transmission and detection of the sensor. The steps corresponding to the above two figures can prepare for the deposition of the top metal.

[0196] Fig. 22 It shows a schematic structural diagram of the piezoelectric component 100 in which a top metal is deposited after connecting channels are respectively opened on the first electrode layer 110 and the second electrode layer 130; Fig.23 A schematic diagram of the structure of the piezoelectric component 100 after patterning the top metal layer is shown; through deposition and patterning processes, the top metal layer is processed into a specific shape and size to enhance the conductivity and signal transmission capability of the sensor.

[0197] Fig.24 The protective structure 600 is set outside the piezoelectric component 100 and the viewing angle is switched to the Figure 3 Schematic diagram of the structure in the AA direction; Fig.25 The schematic diagram of the structure when the buried oxide layer 220 in the SOI wafer is processed by a sacrificial layer to open a resonant cavity 221 is shown; Fig.26 It shows a schematic structural diagram after a pressure cavity 231 is opened on the side of the substrate layer 230 away from the piezoelectric component 100;

[0198] Fig. 27 shows a schematic structural diagram of the cover 500 before processing; Fig.28 shows a schematic structural diagram of the cover 500 after being formed; Fig.29 shows a schematic structural diagram of the cover 500 after installation; Fig.30 This is a schematic diagram of the structure of a piezoelectric resonant pressure sensor 10 in an example of the present application when a cover 500 is provided but no protective structure 600 is provided. Figures 24 to 30 In FIG. 1 , a schematic diagram of the structure of the buried oxide layer 220 in the SOI wafer using a sacrificial layer processing method to open a resonant cavity 221, opening a pressure cavity 231 on the side of the substrate layer 230 away from the piezoelectric component 100, and processing and installing the cover 500 is shown. The completion of these steps enables the piezoelectric resonant pressure sensor 10 to have a complete structure and function.

[0199] Through detailed interpretation and analysis of the above figures, the preparation process of the piezoelectric resonant pressure sensor 10 can be more comprehensively understood, so as to ensure that the sensor has excellent performance and stability.

[0200] The same or similar numbers in the drawings of this application correspond to the same or similar parts; in the description of this application, it should be understood that if the terms "upper", "lower", "left", "right", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings. This is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as a limitation on this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0201] The above are only preferred examples of the present application and are not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A piezoelectric resonant pressure sensor, characterized in that: Applied to the core electronics industry, the piezoelectric resonant pressure sensor comprises: A piezoelectric component is directly or indirectly connected to an external circuit; A resonant component is arranged on one side of the piezoelectric component, wherein the resonant component is made of an SOI wafer, and the SOI wafer includes a device layer, a buried oxide layer and a substrate layer connected in sequence; The device layer is connected to the piezoelectric component, at least one resonant cavity is arranged in the buried oxide layer, a pressure cavity is opened on the side of the substrate layer away from the device layer, and the external pressure received by the pressure cavity can be transmitted to the resonant film on the device layer; In the direction of the resonant component away from the piezoelectric component, a projection of at least one of the resonant cavities is located outside a projection of the pressure chamber.

2. The piezoelectric resonant pressure sensor according to claim 1, characterized in that: The resonant cavity is opened on the buried oxide layer by means of a sacrificial layer.

3. The piezoelectric resonant pressure sensor according to claim 1, characterized in that: Part of the device layer closes or does not close the resonant cavity, and the part of the device layer that closes the resonant cavity is the resonant film.

4. The piezoelectric resonant pressure sensor according to claim 3, characterized in that: The pressure cavity penetrates the substrate layer, and the buried oxide layer forms a pressure sensitive film in a region corresponding to the pressure cavity; At least one of the resonant cavities is located on the peripheral side of the pressure sensitive film, and the pressure received by the pressure cavity can act on the pressure sensitive film and be transmitted to the device layer.

5. The piezoelectric resonant pressure sensor according to claim 4, characterized in that: The pressure sensitive film, the device layer and the piezoelectric component are stacked on each other and receive external pressure together.

6. The piezoelectric resonant pressure sensor according to claim 4, characterized in that: An anchor point for transmitting stress is arranged between the resonant cavity and the pressure cavity, and the anchor point is arranged on the buried oxide layer. External pressure can act on the pressure sensitive film and be transmitted to the resonant film through the anchor point.

7. The piezoelectric resonant pressure sensor according to claim 4, characterized in that: The thickness of the device layer is a first preset thickness, which is the thickness of the resonant film; the thickness of the buried oxide layer is a second preset thickness, which is the thickness of the pressure sensitive film.

8. The piezoelectric resonant pressure sensor according to any one of claims 1 to 7, characterized in that: A cover is provided on a side of the piezoelectric component facing away from the resonant component, and the cover and the piezoelectric component enclose a sealed cavity; and / or, A protection structure is arranged on a side of the piezoelectric component away from the resonance component, and the protection structure covers the surface of the piezoelectric component.

9. A pressure compensation system for a piezoelectric resonant pressure sensor, characterized in that: include: At least one piezoelectric resonant pressure sensor according to any one of claims 1 to 8; as well as, At least one compensation sensor, wherein the compensation sensor is spaced apart from or integrated with the piezoelectric resonant pressure sensor; The compensation sensor can receive ambient pressure, and the piezoelectric resonant pressure sensor can receive the pressure to be measured and the ambient pressure. The value of the pressure to be measured can be obtained by subtracting the detection value of the compensation sensor from the detection value of the piezoelectric resonant pressure sensor.

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