CN118794572A - Piezoelectric resonant pressure sensor, pressure compensation system and preparation method - Google Patents

Abstract

The application discloses a piezoelectric resonance type pressure sensor, a pressure compensation system and a preparation method, and relates to the technical field of manufacturing of sensitive elements and sensors in the electronic core industry; the pressure cavity is formed in one side, away from the piezoelectric component, of the resonant component, and pressure received by the pressure cavity can be transmitted to a resonant structure on one side of the resonant cavity; and in the direction that the resonant assembly is away from the piezoelectric assembly, the projection of at least one resonant cavity is positioned outside the projection of the pressure cavity. The piezoelectric resonant pressure sensor has larger bearing capacity, larger pressure detection range and relatively simple structure, and is easier to realize miniaturization and mass production.

Description

Piezoelectric resonant pressure sensor, pressure compensation system and preparation method

Technical Field

The present application relates to the field of sensitive components and sensor manufacturing technology in the core electronics industry, and in particular to a piezoelectric resonant pressure sensor, a pressure compensation system, and a preparation method.

Background Art

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.

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.

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.

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.

Summary of the invention

The present application provides a piezoelectric resonant pressure sensor, a pressure compensation system and a preparation method, which can enable the piezoelectric resonant pressure sensor to have a greater bearing capacity and thus a larger pressure detection range. Also, due to its relatively simple structure, it is easier to achieve miniaturization and mass production.

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:

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

A resonant component is arranged on one side of the piezoelectric component, at least one resonant cavity is arranged inside the resonant component, a pressure cavity is opened on the side of the resonant component away from the piezoelectric component, and the pressure received by the pressure cavity can be transmitted to the resonant structure on one side of the resonant cavity;

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.

The opening of the pressure cavity in the above structure can form a pressure-sensitive film, and the setting of the resonant cavity can form a resonant film. The pressure-sensitive film can be stacked on part of the resonant structure and part of the piezoelectric component to form a film structure with a higher thickness and pressure-sensitive function. At this time, the pressure is directly borne by the thicker pressure-sensitive film, and is transmitted to the resonant film and the piezoelectric component through the side of the resonant cavity and the integrated laminated structure on the entire pressure-sensitive film, and converted into stress on the resonant film and the piezoelectric component. In order to ensure sensitivity, the resonant film and the piezoelectric component 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. And because the structure of the piezoelectric resonant pressure sensor of the present application is integrated into one through the MEMS process, it can be more easily miniaturized and easier to achieve mass production.

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.

In some examples, the resonant component includes the resonant structure and the pressure-sensitive structure connected to each other, the resonant structure is connected to the piezoelectric component, and the pressure-sensitive structure is disposed on a side of the resonant structure away from the piezoelectric component;

A resonant cavity and a pressure cavity are arranged inside the resonant component, and both the resonant cavity and the pressure cavity are opened on the pressure sensitive structure. The resonant cavity is opened on the side of the pressure sensitive structure close to the resonant structure, and is supported by the resonant structure around the resonant cavity, and the resonant cavity can be closed or not. The existence of the resonant cavity is to ensure the normal operation of the resonant structure and provide space for the movement of the resonant structure.

The pressure sensitive structure includes a resonance layer, a buried oxide layer and a substrate layer connected in sequence, the resonance layer is connected to the resonance structure, the resonance cavity is opened in the resonance layer, the resonance structure closes or does not close the opening of the resonance cavity, and the pressure cavity is opened in the substrate layer.

The resonant layer is connected to the resonant structure and is the key part of the resonance effect in the piezoelectric resonant pressure sensor. At least one resonant cavity is provided in the resonant layer, and the resonant cavity, the resonant structure, and the piezoelectric component together constitute a resonant system. When the pressure to be measured acts on the pressure-sensitive structure, the pressure to be measured is transmitted to the resonant film through the anchor point, and then transmitted to the piezoelectric component by the resonant film. During the transmission process, the pressure to be measured is converted into stress on the resonant film and stress on the piezoelectric component in turn. During the transmission process, the pressure to be measured can drive the resonant film to produce resonant changes, or cooperate with the piezoelectric component to use the inverse piezoelectric effect to excite the change in resonant frequency, thereby detecting the specific value of the pressure to be measured.

In some examples, the pressure cavity at least penetrates the substrate layer, and at most penetrates the buried oxide layer, and a pressure-sensitive film is formed in a region of the resonance layer corresponding to the pressure cavity;

At least one of the resonance cavities is located on a 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 resonance structure.

The pressure cavity can penetrate both the substrate layer and the buried oxide layer, forming a channel 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 cavity. During the processing of the pressure cavity, the buried oxide layer can be used to identify the processing depth of the pressure cavity. The pressure cavity can also only penetrate the substrate layer and retain the buried oxide layer.

The pressure chamber may be a unidirectionally open pressure groove, the bottom of the pressure groove may be located at a pressure-sensitive film, the pressure-sensitive film may be a part of the resonance layer, the resonance chamber may be arranged in the peripheral area of the pressure-sensitive film, the pressure-sensitive film may have a high sensitivity characteristic, the pressure-sensitive film may transmit the pressure to be measured received in the pressure chamber to the resonance structure and generate a resonance effect, or utilize a piezoelectric component to perform an inverse piezoelectric effect and make the resonance structure enter a resonance state, and detect the pressure by changing the resonance frequency of the resonance film on the resonance structure, thereby improving the measurement accuracy.

The pressure-sensitive film in the above structure can be used to superimpose the thickness of the resonant structure, and the thicker pressure-sensitive film can be used to sense the pressure. The stress is then transferred to the piezoelectric resonator through the membrane structure shared by the pressure-sensitive film and the piezoelectric bending 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.

In some examples, the resonant structure includes a fixed portion and a resonant film connected to each other, a first side of the fixed portion is connected to the piezoelectric component, and a second side of the fixed portion is connected to the pressure sensitive structure;

The first side of the resonant film is connected to the piezoelectric component, and the second side of the resonant film closes or does not close the opening of the resonant cavity.

The resonant structure may have certain vibration characteristics and energy conversion efficiency. The resonant structure may be specifically composed of a fixed part and a resonant film connected to each other. The resonant structure may produce a resonant frequency effect between the piezoelectric component and the pressure sensitive structure. The pressure to be measured received by the pressure sensitive structure may be converted and applied to the piezoelectric component. Alternatively, the piezoelectric component may utilize the inverse piezoelectric effect to produce a change in the resonant frequency on the resonant film, thereby ensuring the detection of the pressure to be measured.

The fixing part is naturally formed during the processing of the resonance structure, and the fixing part can make the setting of the resonance film more stable and reliable.

The resonant film is the functional part of the resonant structure. The piezoelectric component can use the inverse piezoelectric effect to produce changes in the resonant frequency on the resonant film. The pressure to be measured can act on the pressure-sensitive film and be transmitted to the resonant film and the piezoelectric component through the anchor point, and then converted into stress on the resonant film and the piezoelectric component.

In some examples, the resonant component is formed by processing two SOI wafers, and the two SOI wafers are respectively a first SOI wafer and a second SOI wafer.

The pressure sensitive structure is formed by processing the first SOI wafer, the resonant structure is formed by processing the second SOI wafer, and the first device layer of the second SOI wafer is bonded to the second device layer of the first SOI wafer.

The resonant structure is formed after the second SOI wafer is processed. Specifically, the resonant structure can be processed on the second SOI wafer through precise micromachining technology. For example, the second substrate layer and the second buried oxide layer in the second SOI wafer can be cut off, and the second device layer can be used as the resonant structure. In the specific processing process, the first device layer and the second device layer can be bonded, and then the second substrate layer and the second buried oxide layer can be cut off. This method can ensure the processing accuracy and reduce the process difficulty. When the second SOI wafer has the second substrate layer and the second buried oxide layer, it can have a sufficient thickness to facilitate the bonding of the first device layer and the second device layer.

The thickness of the device layer in the SOI wafer can be strictly controlled. The thickness of the second device layer can be set in advance to the thickness of the resonant structure. The resonant film is part of the resonant structure, so the thickness of the second device layer also corresponds to the thickness of the resonant film.

In some examples, the resonant cavity is provided with at least one, and in a direction of the resonant component away from the piezoelectric component, a projection of at least one of the resonant cavities surrounds an outer side of a projection of the pressure chamber.

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.

In some examples, the piezoelectric component 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 and at least one first electrode structure.

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,

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.

The side of the piezoelectric component facing away from the resonant component 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.

The pressure in the sealed cavity and the pressure in the pressure cavity may have a certain pressure difference, and an absolute pressure or relative pressure sensor can 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 by the piezoelectric resonant pressure sensor is the pressure value received by the pressure cavity. 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 by the piezoelectric resonant pressure sensor needs to be subtracted from the pressure value in the sealed cavity to obtain the pressure value received by the pressure cavity. At this time, the sensor is a relative pressure sensor.

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

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

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

The compensation sensor may be affected by the environment, and the piezoelectric resonant pressure sensor can receive the pressure to be measured and the environmental influence. 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.

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 influence of environmental influences on the measurement results by introducing a compensation sensor.

The pressure compensation system mainly includes two key parts: a piezoelectric resonant pressure sensor and at least one compensation sensor. The piezoelectric resonant pressure sensor is responsible for receiving the pressure to be measured. The piezoelectric resonant pressure sensor will simultaneously detect the sum of the value of the pressure to be measured and the value of the surrounding environment. The compensation sensor can be specifically responsible for being affected by the environment, that is, the atmospheric pressure around the sensor or other external pressures that may affect the measurement results. The corresponding value detected by the compensation sensor is the value of the surrounding environment.

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 two SOI wafers into the piezoelectric resonant pressure sensor, and the method comprises:

Taking a first SOI wafer, and setting the thickness of a first device layer of the first SOI wafer to be the thickness of the pressure sensitive film;

The above steps can accurately control the thickness of the first device layer so that it matches the required pressure-sensitive film thickness. This step is crucial and determines the sensitivity and accuracy of the sensor.

Opening at least one resonant cavity on the first device layer;

The above steps can utilize advanced micro-nano processing technology to open at least one resonant cavity on the first device layer. The existence of the resonant cavity can effectively improve the response speed and stability of the sensor.

Taking a second SOI wafer, and setting the thickness of the second device layer of the second SOI wafer to the thickness of the resonant film;

The above steps can set the thickness of the second device layer to an ideal thickness of the resonant film. This step ensures that the resonant film has sufficient flexibility and mechanical strength to meet the working requirements of the piezoelectric resonant pressure sensor.

turning over the second SOI wafer and bonding the second device layer to the first device layer;

The above steps can make the second device layer tightly bonded to the first device layer. This step utilizes the unique structure and excellent material properties of the SOI wafer to achieve a stable connection between the device layers.

Thinning the second SOI wafer until the second buried oxide layer is removed and the second device layer remains on the second SOI wafer;

The above steps can successfully remove the second substrate layer and the second buried oxide layer by precisely controlling the thinning process, so that only the second device layer remains on the second SOI wafer. This step not only simplifies the structure of the sensor, but also improves its sensitivity. Part of the structure of the second device layer can be used as a resonant film that can cooperate with the resonant cavity.

A piezoelectric component is processed on a side of the second device layer facing away from the first device layer, and an external conductive structure is reserved on the piezoelectric component.

The above steps can process the piezoelectric component on the side of the second device layer away from the first device layer. The existence of the piezoelectric component is the key to realizing the conversion of the sensor electrical signal. At the same time, an external conductive structure can be reserved on the piezoelectric component to connect the output signal of the sensor to the external circuit.

The pressure cavity may be opened on the first substrate layer. After the pressure cavity is processed, external pressure can be received through the pressure cavity, and the formation of the pressure cavity can be used to receive external pressure. When pressure acts on the pressure cavity, an anchor point for pressure transmission can be formed between the pressure cavity and the resonance cavity, and the pressure is transmitted to the resonance film and the piezoelectric component through the anchor point structure, forming stress on the resonance film and the piezoelectric component.

BRIEF DESCRIPTION OF THE DRAWINGS

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.

FIG1 is a schematic diagram of the structure of a piezoelectric resonant pressure sensor in an example of the present application;

FIG2 is a schematic diagram of the structure of a piezoelectric resonant pressure sensor in an example of the present application without a cover;

FIG3 is 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;

FIG4 is a schematic cross-sectional view of the structure of the piezoelectric resonant pressure sensor in FIG3 of an example of the present application when there is no cover in the direction of A-A;

FIG5 is a schematic cross-sectional view of the structure of the piezoelectric resonant pressure sensor in FIG3 of an example of the present application when there is no cover in the B-B direction;

FIG6 is a schematic diagram of the structure of a piezoelectric resonant pressure sensor in an example of the present application without a cover and without a lead electrode and a protective layer;

FIG7 is a schematic diagram of a top view of another structure of a piezoelectric resonant pressure sensor in an example of the present application without a lead electrode and a protective layer;

FIG8 is a schematic diagram of a top view of another structure of a piezoelectric resonant pressure sensor in an example of the present application without lead electrodes and a protective layer;

FIG9 is a schematic diagram of a top view of another structure of a piezoelectric resonant pressure sensor in an example of the present application without lead electrodes and a protective layer;

FIG10 is a schematic diagram of a top view of another structure of a piezoelectric resonant pressure sensor in an example of the present application without a lead electrode and a protective layer;

FIG11 is a schematic diagram of a top view of another structure of a piezoelectric resonant pressure sensor in an example of the present application without lead electrodes and a protective layer;

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

13 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 electrodes and the protective layer;

FIG14 is a schematic diagram of a process for preparing a piezoelectric resonant pressure sensor in an example of the present application;

FIG15 is a schematic structural diagram of a first SOI wafer before processing in an example of the present application;

FIG16 is a schematic diagram of the structure of a first SOI wafer after a resonant cavity is opened in an example of the present application;

FIG17 is a schematic diagram of the structure of a second SOI wafer before processing in an example of the present application;

FIG18 is a schematic diagram of a structure in which a second SOI wafer is inverted and bonded toward a first SOI wafer in an example of the present application;

FIG19 is a schematic diagram of a structure in which a second SOI wafer is inverted and bonded to a first SOI wafer in an example of the present application;

FIG20 is a schematic diagram of a structure in which a second SOI wafer is bonded to a first SOI wafer and a second buried oxide layer and a second substrate layer are removed in an example of the present application;

FIG21 is a schematic diagram of the structure after a piezoelectric component is deposited on the side of the second device layer facing away from the first device layer in an example of the present application;

FIG22 is a schematic diagram of a structure in which a piezoelectric component is deposited on the side of the second device layer facing away from the first device layer and the second electrode layer is etched in an example of the present application;

FIG23 is a schematic diagram of a structure in which a protective structure is provided outside a piezoelectric component in an example of the present application;

FIG24 is a schematic diagram of a structure in which a protective structure is provided on the outer side of a piezoelectric component in an example of the present application and the viewing angle is switched to the B-B direction in FIG3 ;

FIG25 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;

FIG26 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;

FIG27 is a schematic diagram of the structure of a piezoelectric component in an example of the present application when a top layer of metal is deposited after connecting channels are respectively opened on the first electrode layer and the second electrode layer;

FIG28 is a schematic diagram of the structure of a piezoelectric component after patterning the top metal layer in an example of the present application;

FIG29 is a schematic diagram of a structure in which a protective structure is provided on the outer side of a piezoelectric component in an example of the present application and the viewing angle is switched to the direction A-A in FIG3 ;

FIG30 is a schematic diagram of the structure of a resonant component in an example of the present application after a pressure chamber is opened on the side of the resonant component away from the piezoelectric component;

FIG31 is a schematic diagram of the structure of a cover before processing in an example of the present application;

FIG32 is a schematic diagram of the structure of the cover after molding in an example of the present application;

FIG33 is a schematic diagram of the structure after the cover is installed in an example of the present application;

FIG34 is a schematic diagram of the structure of a piezoelectric resonant pressure sensor in an example of the present application when a cover is provided but no protective structure is provided.

Reference numerals:

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. Resonance structure; 211. Fixing part; 212. Resonance film; 220. Pressure sensitive structure; 221. Resonance layer; 2211. Resonance cavity; 2212. Pressure sensitive film; 222. Buried oxide layer; 223. Substrate layer; 2231. Pressure cavity; 230. Oxide layer; 240. Anchor point; 300. First SOI wafer; 310. First device layer; 320. First buried oxide layer; 330. First substrate layer; 400. Second SOI wafer; 410. Second device layer; 420. Second buried oxide layer; 430. Second substrate layer; 500. Cover; 600. Protection structure.

DETAILED DESCRIPTION

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.

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.

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.

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 configurations have emerged. The present application discloses a piezoelectric resonant pressure sensor configuration combining a piezoelectric component and a resonant component.

In order to achieve the above-mentioned purpose, please refer to Figures 1-34. The first aspect of the present application proposes a piezoelectric resonant pressure sensor, which can enable the piezoelectric resonant pressure sensor to have a greater bearing capacity and thus a larger pressure detection range. Also, due to its relatively simple structure, it is easier to achieve miniaturization and mass production.

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.

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.

The piezoelectric resonant pressure sensor 10 uses a thicker pressure sensitive film to sense pressure, and then converts 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 in the pressure measurement range.

The above arrangement enables the piezoelectric resonant pressure sensor to be widely used in the core technology field of the electronics industry.

In the present application, the anchor point 240 refers to the area where the pressure sensitive film is connected to the resonant film. The external pressure acting on the pressure sensitive film can be transmitted to the anchor point 240 during the deformation of the pressure sensitive film, and act on the resonant film through the anchor point 240. During the transmission process, the external pressure can be converted through the anchor point 240 to improve the pressure bearing capacity of the pressure chamber, thereby improving the pressure detection range. The piezoelectric resonator can be a combination of the resonant structure and the piezoelectric component in the present application.

1-5 , in some examples, a 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 . 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. At least one resonant cavity 2211 is arranged inside the resonant component 200. A pressure cavity 2231 is opened on the side of the resonant component 200 away from the piezoelectric component 100. The pressure received by the pressure cavity 2231 can be transmitted to the resonant structure 210 on one side of the resonant structure 210.

In the direction of the resonance component 200 away from the piezoelectric component 100 , the projection of at least one resonance cavity 2211 is outside the projection of the pressure cavity 2231 .

The opening of the pressure cavity 2231 in the above structure can form a pressure-sensitive film 2212, and the setting of the resonant cavity 2211 can form a resonant film 212. The pressure-sensitive film 2212 can be stacked on part of the resonant structure 210 and part of the piezoelectric component 100 to form a film structure with a higher thickness and pressure-sensitive function. At this time, the thicker pressure-sensitive film 2212 directly bears the pressure, and is transmitted to the resonant film 212 and the piezoelectric component 100 through the side of the resonant cavity 2211 and the integrated stacked structure on the entire pressure-sensitive film 2212, and converted into stress on the resonant film 212 and the piezoelectric component 100. In order to ensure sensitivity, the resonant film 212 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. And because the structure of the piezoelectric resonant pressure sensor 10 of the present application is integrated into one through the MEMS process, it can be more easily miniaturized and easier to achieve mass production.

The piezoelectric resonant pressure sensor 10 is mainly composed of a piezoelectric component 100 and a resonant component 200. The piezoelectric component 100 can be used as the core part of the piezoelectric resonant pressure sensor 10 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 selection of the piezoelectric component 100 is crucial to 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, LiNbO ₃ , etc.

The resonant component 200 is located on one side of the piezoelectric component 100, and at least one resonant cavity 2211 may be provided inside the resonant component 200. A pressure cavity 2231 is provided on the other side of the resonant component 200 for receiving external pressure. When pressure acts on the pressure cavity 2231, an anchor point 240 for pressure transmission may be formed between the pressure cavity 2231 and the resonant cavity 2211, and the pressure is transmitted to the resonant film 212 and the piezoelectric component 100 through the anchor point 240 structure, forming stress on the resonant film 212 and the piezoelectric component 100.

In the direction of the resonant component 200 toward the pressure sensitive component, the projection of at least one resonant cavity 2211 is located outside the projection of the pressure cavity 2231. This arrangement cleverly utilizes the interaction between the resonant cavity 2211 and the pressure cavity 2231, 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 2211 can also be partially arranged inside the projection of the pressure cavity 2231.

4 , in some examples, the resonance component 200 includes a resonance structure 210 and a pressure sensitive structure 220 connected to each other. The resonance structure 210 is connected to the piezoelectric component 100 , and the pressure sensitive structure 220 is disposed on a side of the resonance structure 210 away from the piezoelectric component 100 .

The resonant component 200 is composed of a resonant structure 210 and a pressure sensitive structure 220, which are connected to each other. The resonant structure 210 is closely connected to the piezoelectric component 100, and together they constitute the core structure of the sensor. The pressure sensitive structure 220 is arranged on the other side of the resonant structure 210, and is responsible for sensing the change in the pressure to be measured. The above structure enables the sensor to detect pressure by changing the resonant frequency of the resonant component 200 when it is under pressure.

The resonant cavity 2211 is opened on a side of the pressure sensitive structure 220 close to the resonant structure 210, and the resonant structure 210 closes or does not close the opening of the resonant cavity 2211. The pressure cavity 2231 is opened on a side of the pressure sensitive structure 220 away from the resonant structure 210.

A resonant cavity 2211 and a pressure cavity 2231 are provided inside the resonant component 200, and both the resonant cavity 2211 and the pressure cavity 2231 are provided on the pressure sensitive structure 220. The resonant cavity 2211 is provided on a side of the pressure sensitive structure 220 close to the resonant structure 210, and is supported around the resonant cavity 2211 by the resonant structure 210, and the resonant cavity 2211 may be closed or not. The existence of the resonant cavity 2211 is to ensure the normal operation of the resonant structure 210 and to provide space for the movement of the resonant structure 210.

The resonant cavity 2211 is matched with the resonant structure 210. The part of the resonant structure 210 located above the opening of the resonant cavity 2211 can form a resonant film 212. The resonant film 212 is driven by the piezoelectric component 100 to resonate. When the pressure is transmitted to the resonant film 212 and the piezoelectric component 100 through the anchor point 240 structure, stress is formed on the resonant film 212 and the piezoelectric component 100. The stress will cause the resonant frequency of the resonant film 212 to change, and the change is detected by the piezoelectric component 100.

The pressure sensitive structure 220 includes a resonance layer 221, a buried oxide layer 222 and a substrate layer 223 connected in sequence. The resonance layer 221 is connected to the resonance structure 210. The resonance cavity 2211 is opened in the resonance layer 221. The resonance structure 210 is supported around the resonance cavity 2211. The pressure cavity 2231 is opened in the substrate layer 223.

The pressure sensitive structure 220 includes a resonance layer 221, a buried oxide layer 222 and a substrate layer 223 connected in sequence. The resonance layer 221 is connected to the resonance structure 210 and is a key part of the resonance effect in the piezoelectric resonant pressure sensor 10. At least one resonance cavity 2211 is provided in the resonance layer 221, and the resonance cavity 2211, the resonance structure 210 and the piezoelectric component 100 together constitute a resonance system. When the pressure to be measured acts on the pressure sensitive structure 220, the pressure to be measured is transmitted to the resonance film 212 through the anchor point 240, and then transmitted to the piezoelectric component 100 by the resonance film 212. During the transmission process, the pressure to be measured is converted into stress on the resonance film 212 and stress on the piezoelectric component 100 in turn. During the transmission process, the pressure to be measured can drive the resonance film 212 to produce a resonance change, or cooperate with the piezoelectric component 100 to use the inverse piezoelectric effect to excite the change of the resonance frequency, and then detect the specific value of the pressure to be measured, ensure that the piezoelectric detection is carried out normally, and make the accuracy of the piezoelectric detection more accurate.

The pressure chamber 2231 is also a key part of the piezoelectric resonant pressure sensor 10. The pressure chamber 2231 is opened in the substrate layer 223. The function of the pressure chamber 2231 is to provide the sensor with an environment that is 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 2231 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.

3 and 4 , in some examples, the pressure cavity 2231 at least penetrates the substrate layer 223 , the pressure cavity 2231 at most penetrates the buried oxide layer 222 , and a pressure sensitive film 2212 is formed in the region of the resonance layer 221 corresponding to the pressure cavity 2231 ;

At least one resonant cavity 2211 is located around the pressure sensitive film 2212, and the pressure received by the pressure cavity 2231 can act on the pressure sensitive film 2212 and be transmitted to the resonant structure 210. Specifically, the pressure received by the pressure cavity 2231 can be transmitted to the resonant film 212 on the resonant structure 210 through the anchor point 240.

The pressure chamber 2231 penetrates both the substrate layer 223 and the buried oxide layer 222, forming a channel 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 provision of the buried oxide layer 222 can facilitate the processing of the pressure chamber 2231. During the processing of the pressure chamber 2231, the buried oxide layer 222 can be used to identify the processing depth of the pressure chamber 2231. It should be understood that the pressure chamber 2231 can also only penetrate the substrate layer 223 and retain the buried oxide layer 222.

The pressure chamber 2231 may be a unidirectionally opened pressure groove, the bottom of the pressure groove may be located at a pressure-sensitive film 2212, the pressure-sensitive film 2212 may be a part of the resonance layer 221, the resonance chamber 2211 may be arranged in the peripheral area of the pressure-sensitive film 2212, the pressure-sensitive film 2212 may have a high sensitivity characteristic, the pressure-sensitive film 2212 may transfer the pressure to be measured received in the pressure chamber 2231 to the resonance structure 210 and generate a resonance effect, or utilize the piezoelectric component 100 to perform an inverse piezoelectric effect and make the resonance structure 210 enter a resonance state, and detect the pressure by changing the resonance frequency of the resonance film 212 on the resonance structure 210, thereby improving the measurement accuracy.

In the above structure, the pressure sensitive film 2212 can be used to overlap the thickness of the resonant structure 210, and the thicker pressure sensitive film 2212 can be used to sense the pressure. Then, the stress is transferred to the piezoelectric resonator through the membrane structure shared by the pressure sensitive film 2212 and the piezoelectric bending 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.

When the pressure chamber 2231 receives the pressure to be measured, the pressure sensitive film 2212 will be 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 2211 is provided on the peripheral side of the pressure sensitive film 2212.

The region where the resonant structure 210 closes the opening of the resonant cavity 2211 may form a resonant film 212 , and a side of the resonant film 212 facing away from the resonant cavity 2211 is connected to the piezoelectric component 100 .

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.

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.

4 and 5 , in some examples, the resonant structure 210 includes a fixed portion 211 and a resonant film 212 connected to each other, a first side of the fixed portion 211 is connected to the piezoelectric component 100 , and a second side of the fixed portion 211 is connected to the pressure sensitive structure 220 .

The first side of the resonant film 212 is connected to the piezoelectric component 100 , and the second side of the resonant film 212 closes the opening of the resonant cavity 2211 .

The resonant structure 210 may have certain vibration characteristics and energy conversion efficiency. The resonant structure 210 may be specifically formed by interconnecting a fixed portion 211 and a resonant film 212. The resonant structure 210 may generate a resonant frequency effect between the piezoelectric component 100 and the pressure sensitive structure 220. The pressure to be measured received by the pressure sensitive structure 220 may be converted and applied to the piezoelectric component 100. Alternatively, the piezoelectric component 100 may utilize the inverse piezoelectric effect to generate a change in the resonant frequency on the resonant film 212, thereby ensuring the detection of the pressure to be measured.

The fixing portion 211 is naturally formed during the processing of the resonant structure 210 . The fixing portion 211 can make the disposition of the resonant film 212 more stable and reliable.

The resonant film 212 is a functional part of the resonant structure 210. The piezoelectric component 100 can generate a change in the resonant frequency on the resonant film 212 by using the inverse piezoelectric effect. The pressure to be measured can act on the pressure-sensitive film 2212 and be transmitted to the resonant film 212 and the piezoelectric component 100 through the anchor point 240, and then converted into stress on the resonant film 212 and the piezoelectric component 100.

One side of the resonant film 212 is connected to the piezoelectric component 100 , and the other side of the resonant film 212 closes the opening of the resonant cavity 2211 .

In some examples, the pressure sensitive film 2212 can also be formed by thinning the opening position after the pressure sensitive structure 220 opens the pressure cavity 2231. The side of the pressure sensitive film 2212 facing away from the pressure cavity 2231 is connected to the resonant structure 210. The pressure received by the pressure cavity 2231 can act on the pressure sensitive film 2212 and be transmitted to the resonant structure 210.

The setting and optimization of the pressure sensitive structure 220 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 2212 in the pressure sensitive structure 220 can be combined with the resonant film 212 in the resonant structure 210 to achieve accurate perception and response to the pressure to be measured, thereby improving the performance of the piezoelectric resonant pressure sensor 10.

The main functional part of the pressure sensitive structure 220 is the pressure sensitive film 2212 . The pressure sensitive film 2212 is the thinnest part of the pressure sensitive structure 220 that corresponds to the pressure cavity 2231 after the pressure cavity 2231 is formed in the pressure sensitive structure 220 .

The pressure sensitive film 2212 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 resonant cavity 2211, and then transferring the deformation to the resonant film 212, so that stress is generated in the resonant film 212 and the piezoelectric component 100, thereby changing the structural resonant frequency. The change in the resonant frequency can convert the mechanical energy on the resonant film 212 into an electrical signal on the piezoelectric component 100 through the piezoelectric effect, and then the electrical signal is analyzed and judged through an external circuit, and the magnitude of the pressure to be measured can be inferred using the electrical signal.

The vibration characteristics of the resonant film 212 can improve the energy transfer and conversion efficiency in the resonant cavity 2211 by resonance, which can make the detection data more accurate and stable.

The pressure sensitive film 2212 is placed at the position of the pressure chamber 2231, so that the pressure applied by the outside can directly act on the pressure sensitive film 2212. When the pressure sensitive film 2212 is subjected to pressure, the pressure sensitive film 2212 will undergo a slight deformation, and this deformation will then be transmitted to the resonant structure 210 connected to the pressure sensitive film 2212, and then the pressure detection is realized through the cooperation of the resonant cavity 2211, the resonant film 212 and the piezoelectric component 100.

The resonant structure 210 can vibrate when stimulated by external factors. The resonant structure 210 is connected to the pressure sensitive film 2212, so when the resonant film 212 is deformed, it will generate a certain excitation on the resonant structure 210, causing the resonant structure 210 to vibrate. This vibration can be captured by the piezoelectric component 100 and converted into an electrical signal, thereby achieving accurate measurement of pressure.

Correspondingly, the piezoelectric component 100 can output an electrical signal in reverse, thereby causing the resonant film 212 to produce a desired resonant deformation.

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 212 on the resonance structure 210 to vibrate, and the forward piezoelectric effect can be used to detect the frequency parameters of the resonance structure 210.

The arrangement of the pressure sensitive film 2212 combined with the resonant structure 210 also has many advantages. Since the pressure sensitive film 2212 can directly sense the change in the pressure to be measured, this arrangement has higher performance and accuracy. Furthermore, since the resonant structure 210 can generate a certain 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.

In practical applications, the arrangement of the pressure sensitive film 2212 combined with the resonant structure 210 is widely used in various fields. For example, in the field of industrial automation, the arrangement of the pressure sensitive film 2212 combined with the resonant structure 210 can be used to achieve precise pressure control and monitoring, and improve production efficiency and product quality. In automotive electronic systems, the arrangement of the pressure sensitive film 2212 combined with the resonant structure 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 2212 combined with the resonant structure 210 can be used to monitor the patient's vital signs, such as blood pressure and heart rate.

The combination of the pressure sensitive film 2212 and the resonant structure 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.

In some examples, the resonant component 200 is formed by processing two SOI wafers, and the two SOI wafers are respectively a first SOI wafer 300 and a second SOI wafer 400 .

The pressure sensitive structure 220 is formed by processing the first SOI wafer 300 , the resonant structure 210 is formed by processing the second SOI wafer 400 , and the first device layer 310 of the first SOI wafer 300 and the second device layer 410 of the second SOI wafer 400 are bonded.

The manufacture of the resonant component 200 is a relatively important link in the field of micro-nano electromechanical systems. With the continuous advancement of semiconductor technology, the processing technology of the resonant component 200 based on silicon on insulator (SOI) materials has become increasingly mature. The present application can use two SOI wafers to process and form the resonant component 200, which involves the processing and bonding process of the second SOI wafer 400 and the first SOI wafer 300.

SOI material is composed of a silicon film, a silicon dioxide buried layer and a silicon substrate. This structure makes SOI material have unique properties in mechanics, electricity and heat, and is very suitable for manufacturing high-performance resonant components 200. Specifically, the first SOI wafer 300 includes a first device layer 310, a first buried oxide layer 320 and a first substrate layer 330; the second SOI wafer 400 includes a second device layer 410, a second buried oxide layer 420 and a second substrate layer 430. The first device layer 310 can be the resonant layer 221 where the pressure sensitive film 2212 is located. The thickness of the second device layer 410 can be the same as the thickness of the resonant film 212. The resonant film 212 is a part of the resonant structure 210. The corresponding resonant structure 210 is formed by cutting off the second buried oxide layer 420 and the second substrate layer 430 from the second SOI wafer 400 and leaving the second device layer 410 alone.

The thickness of the first device layer 310 may be greater than or less than the thickness of the second device layer 410 . The thickness of the corresponding pressure sensitive film 2212 may be greater than or less than the thickness of the resonant film 212 .

The resonant structure 210 is formed after the second SOI wafer 400 is processed. Specifically, the resonant structure 210 can be processed on the second SOI wafer 400 by precise micro-machining technology. For example, the second substrate layer 430 and the second buried oxide layer 420 in the second SOI wafer 400 can be cut off, and the second device layer 410 can be used as the resonant structure 210. In the specific processing process, the first device layer 310 and the second device layer 410 can be bonded, and then the second substrate layer 430 and the second buried oxide layer 420 can be cut off. This method can ensure the processing accuracy and reduce the process difficulty. When the second SOI wafer 400 has the second substrate layer 430 and the second buried oxide layer 420, it can have a sufficient thickness to facilitate the bonding of the first device layer 310 and the second device layer 410.

The thickness of the device layer in the SOI wafer can be strictly controlled. The thickness of the second device layer 410 can be set in advance to the thickness of the resonant structure 210. The resonant film 212 is a part of the resonant structure 210, so the thickness of the second device layer 410 also corresponds to the thickness of the resonant film 212.

The second SOI wafer 400 may be processed into a resonant structure 210 having a specific shape and size by using advanced photolithography, etching and other technologies.

The first SOI wafer 300 can be processed to form a pressure sensitive structure 220. It also requires the use of advanced micro-machining technology, such as photolithography, etching, etc. Different from the resonant structure 210, the pressure sensitive structure 220 usually has a more complex structure, such as a resonant cavity 2211, a pressure cavity 2231, a pressure sensitive film 2212, etc., to achieve a sensitive response to external pressure. The resonant cavity 2211 can be opened in the first device layer 310, the pressure cavity 2231 can be opened in the first substrate layer 330, and the pressure sensitive film 2212 can be a part of the first device layer 310.

After the processing of the two SOI wafers is completed, bonding is required. During the bonding process, the second device layer 410 of the second SOI wafer 400 and the first device layer 310 of the first SOI wafer 300 are closely attached to each other by precisely controlling the bonding conditions (such as temperature, pressure, time, etc.). The bonded resonant component 200 not only retains the high performance characteristics of the resonant structure 210, but also realizes a sensitive response to external pressure, thereby improving the stability and reliability of the entire system.

During the bonding process between the first device layer 310 and the second device layer 410 , an oxide layer 230 is formed at the bonding location.

The above structure is a processing of SOI material. For example, this processing technology of the resonant component 200 based on SOI material has many advantages. The high mechanical quality factor of SOI material enables the resonant component 200 to have lower mechanical loss and higher energy conversion efficiency. Secondly, the insulating buried layer of SOI material can effectively isolate the electrical interference between the device layer and the substrate, thereby improving the stability of the system. In addition, the low thermal expansion coefficient and low stress characteristics of SOI material help to reduce the thermal drift and mechanical stress changes of the resonant component 200 when the temperature changes, thereby improving the long-term stability of the system.

In some examples, at least one resonant cavity 2211 is provided, and in the direction of the resonant component 200 away from the piezoelectric component 100 , the projection of at least one resonant cavity 2211 surrounds the outside of the projection of the pressure cavity 2231 .

At least one resonant cavity 2211 may be arranged around the projection of the pressure cavity 2231. When at least two resonant cavities 2211 are arranged, more detection points may be provided, thereby improving the accuracy and stability of the measurement. When the pressure changes, the resonant films 212 corresponding to different resonant cavities 2211 may produce corresponding resonant frequency changes, and these resonant films 212 may verify each other, thereby improving the accuracy of the measurement.

In some examples, a cover 500 is disposed on the side of the piezoelectric component 100 away from the resonance component 200, and the cover 500 and the piezoelectric component 100 enclose a sealed cavity. And/or, a protective structure 600 is disposed on the side of the piezoelectric component 100 away from the resonance component 200, and the protective structure 600 covers the surface of the piezoelectric component 100.

The side of the piezoelectric component 100 facing away from the resonant component 200 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.

The pressure in the sealed cavity and the pressure in the pressure cavity 2231 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 2231 by the piezoelectric resonant pressure sensor 10 is the pressure value received by the pressure cavity 2231. 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 2231 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 2231. At this time, the sensor is a relative pressure sensor.

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 resonant component 200. This protective structure 600 may 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.

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.

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.

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.

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:

Where f _r is the resonant frequency, μ _n is the constant 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.

When the pressure chamber 2231 receives the pressure to be detected, the pressure sensitive film 2212 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 2212 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 212.

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.

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.

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:

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.

When the piezoelectric layer 120 is deformed, the portion of the piezoelectric layer 120 close to the resonance component 200 is squeezed by the pressure to be detected, and the portion of the piezoelectric layer 120 away from the resonance component 200 is stretched by the pressure to be detected. On the cross section of the piezoelectric layer 120, the transition layer 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 above-mentioned neutral layer.

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.

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.

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

Among them, Figure 6 is a three-dimensional schematic diagram of a pressure sensitive device (a combination of a piezoelectric component 100, a resonant structure 210, and a pressure sensitive structure 220) on which lead electrodes and an oxide structure layer (protective structure 600) have not yet been deposited, and Figure 7 is a top view corresponding to Figure 6. The resonant cavity 2211 in this embodiment is a square cavity (a cavity with a cubic structure). The figure has four groups of second electrode structures 150, 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. Figures 6 and 7 are illustrative examples of setting four resonant cavities 2211. The present application may also set other numbers of resonant cavities 2211. Figure 8 shows a piezoelectric resonant pressure sensor 10 structure with a circular cavity (a cavity in the shape of a cylinder), and the other structures are similar to Figure 6.

Figure 9 shows the structure of a piezoelectric resonant pressure sensor 10 with a circular ring cavity. Figure 10 shows the structure of a piezoelectric resonant pressure sensor 10 with a beam structure. Figure 11 shows the structure of a piezoelectric resonant pressure sensor 10 with a beam structure and a stress concentration structure.

12 and 13 , in a second aspect, the present application provides a pressure compensation system for a piezoelectric resonant pressure sensor 10 , comprising at least one of the above-mentioned piezoelectric resonant pressure sensors 10 and at least one compensation sensor 20 , wherein the compensation sensor 20 is spaced apart from or integrated with the piezoelectric resonant pressure sensor 10 .

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.

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.

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.

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.

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.

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.

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.

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.

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.

Referring to FIG. 14 , 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 two SOI wafers into a piezoelectric resonant pressure sensor 10, and the method includes:

First, two SOI wafers need to be prepared. SOI wafer is a silicon-based material with a special structure, and its structure from top to bottom is device layer, buried oxide layer 222 and substrate layer 223. This structure makes SOI wafer have excellent mechanical and electrical properties during the preparation process.

Step S100: taking a first SOI wafer 300 , and setting the thickness of the first device layer 310 of the first SOI wafer 300 to be the thickness of the pressure sensitive film 2212 ;

The above steps can accurately control the thickness of the first device layer 310, so that the first device layer 310 matches the required thickness of the pressure sensitive film 2212. This step is crucial and determines the sensitivity and accuracy of the sensor.

Step S200: opening at least one resonant cavity 2211 on the first device layer 310;

The above steps can utilize advanced micro-nano processing technology to open at least one resonant cavity 2211 on the first device layer 310 .

Step S300: taking a second SOI wafer 400, and setting the thickness of the second device layer 410 of the second SOI wafer 400 to be the same as the thickness of the resonant film 212;

The above steps can set the thickness of the second device layer 410 to the ideal thickness of the resonant film 212. This step ensures that the resonant film has sufficient flexibility and mechanical strength to meet the working requirements of the piezoelectric resonant pressure sensor 10.

Step S400: turning over the second SOI wafer 400 and bonding the second device layer 410 to the first device layer 310;

The above steps can make the second device layer 410 tightly bonded to the first device layer 310. This step utilizes the unique structure and excellent material properties of the SOI wafer to achieve a stable connection between the device layers.

Step S500: thinning the second SOI wafer 400 until the second buried oxide layer 420 is removed and the second device layer 410 remains on the second SOI wafer 400;

The above steps can successfully remove the second substrate layer 430 and the second buried oxide layer 420 by precisely controlling the thinning process, so that the second SOI wafer 400 only retains the second device layer 410. This step not only simplifies the structure of the sensor, but also improves its sensitivity. Part of the structure of the second device layer 410 can be used as a resonant film 212 that can cooperate with the resonant cavity 2211.

Step S600 : processing the piezoelectric component 100 on the side of the second device layer 410 away from the first device layer 310 , and reserving an external conductive structure on the piezoelectric component 100 .

Step S700: opening the pressure chamber on the first substrate layer.

The above steps can process the piezoelectric component 100 on the side of the second device layer 410 away from the first device layer 310. The existence of the piezoelectric component 100 is the key to realizing the conversion of the sensor electrical signal. At the same time, an external conductive structure can be reserved on the piezoelectric component 100 to connect the output signal of the sensor to the external circuit. Referring to Figures 15 to 34, a schematic diagram of the preparation process of the piezoelectric resonant pressure sensor 10 is shown.

FIG. 15 is a schematic diagram showing the structure of the first SOI wafer 300 before processing; and FIG. 16 is a schematic diagram showing the structure of the first SOI wafer 300 after the resonant cavity 2211 is opened.

In the manufacturing process of the above-mentioned electric resonant pressure sensor, the SOI wafer, that is, the silicon on insulator wafer, consists of a three-layer structure: silicon substrate, silicon dioxide insulation layer and silicon device layer. This special structure gives the SOI wafer excellent electrical properties and mechanical stability, making it an ideal material for manufacturing high-performance pressure sensors.

FIG. 15 shows the original structure of the first SOI wafer 300 before processing. It can be clearly seen that the three-layer structure of the silicon device layer, the silicon dioxide insulating layer and the silicon substrate are tightly combined to form a complete wafer. As the processing flow progresses, a resonant cavity is opened on the wafer to form a specific resonant structure. As shown in FIG. 16, the opening of the resonant cavity 2211 causes a significant change in the wafer structure, providing a basis for subsequent processing steps.

FIG. 17 is a schematic diagram showing the structure of the second SOI wafer 400 when it is not processed; FIG. 18 is a schematic diagram showing the structure of the second SOI wafer 400 when it is inverted and bonded toward the first SOI wafer 300.

During the processing of the second SOI wafer 400. In FIG17, it can be seen that the second SOI wafer 400 also has a complete three-layer structure. As the processing proceeds, the wafer will be inverted and bonded toward the first SOI wafer 300, as shown in FIG18. The implementation of this step requires high-precision process control to ensure that the two wafers can be accurately aligned and firmly bonded.

19 shows a schematic structural diagram of the second SOI wafer 400 after being inverted and bonded to the first SOI wafer 300; FIG. 20 shows a schematic structural diagram of the second SOI wafer 400 after being bonded to the first SOI wafer 300 and the second buried oxide layer 420 and the second substrate layer 430 are removed.

After bonding, a composite structure consisting of two SOI wafers is obtained. In order to further optimize its performance, the second buried oxide layer and the second substrate layer need to be removed, as shown in Figure 20. This step allows the second device layer to directly contact the first device layer, thereby improving the electrical performance of the overall structure.

Fig. 21 shows a schematic diagram of the structure after the piezoelectric component 100 is deposited on the side of the second device layer 410 away from the first device layer 310; the piezoelectric component 100 is deposited on the side of the second device layer away from the first device layer. The piezoelectric component is the core component of the piezoelectric resonant pressure sensor, and its performance directly determines the accuracy and stability of the sensor.

FIG. 22 shows a schematic structural diagram of the piezoelectric component 100 deposited on the side of the second device layer 410 facing away from the first device layer 310 and the second electrode layer 130 being etched;

After the piezoelectric component is deposited, the second electrode layer needs to be etched to form a specific electrode structure. As shown in Figure 22, the etched electrode structure can be more effectively electrically connected to the piezoelectric component, thereby improving the response speed and sensitivity of the sensor.

FIG. 23 is a schematic structural diagram showing a protective structure 600 disposed outside the piezoelectric assembly 100;

FIG. 24 shows a schematic structural diagram when a protective structure 600 is disposed outside the piezoelectric component 100 and the viewing angle is switched to the B-B direction in FIG. 3 ;

In order to protect the piezoelectric component from the influence of the external environment, it is also necessary to set a protective structure 600 on its outside. The protective structure 600 is usually made of insulating material, which can effectively isolate external impurities such as moisture and dust, thereby extending the service life of the sensor. As shown in Figures 23 and 24, the setting of the protective structure makes the entire sensor structure more stable and reliable.

FIG25 is a schematic diagram of the structure when a connecting channel is provided on the second electrode layer in a piezoelectric component in an example of the present application; FIG26 is a schematic diagram of the structure when a connecting channel is provided on the first electrode layer in a piezoelectric component in an example of the present application; FIG27 is a schematic diagram of the structure when a top layer metal is deposited after connecting channels are provided on the first electrode layer and the second electrode layer in a piezoelectric component in an example of the present application; FIG28 is a schematic diagram of the structure after the top layer metal is patterned on the piezoelectric component 100;

In order to improve the performance and ease of use of the sensor, it is also necessary to open communication channels on the first electrode layer and the second electrode layer of the piezoelectric component and deposit the top metal. This step enables the sensor to connect and communicate with the external circuit more conveniently, thereby realizing real-time monitoring and data processing of the pressure signal. As shown in Figures 25, 26, 27 and 28, after this series of processing steps, a complete and powerful piezoelectric resonant pressure sensor can be obtained.

FIG29 shows a schematic diagram of a structure in which a protective structure 600 is disposed outside the piezoelectric component 100 and the viewing angle is switched to the A-A direction in FIG3 ; FIG30 shows a schematic diagram of a structure in which a pressure chamber 2231 is provided on the side of the resonant component 200 away from the piezoelectric component 100;

Figure 31 shows a schematic diagram of the structure of the cover 500 before processing; Figure 32 shows a schematic diagram of the structure of the cover 500 after forming; and Figure 33 shows a schematic diagram of the structure of the cover 500 after installation. The cover 500 is fixed to the piezoelectric component by bonding, which can be anodic bonding, metal bonding such as Al-Ge, Au-Au, or other bonding methods.

In order to further optimize the performance and use effect of the sensor, a pressure chamber can be opened on the side of the resonant component away from the piezoelectric component, and a cover can be set outside the sensor to protect the internal structure from the influence of the external environment. As shown in Figures 30, 31, 32 and 33, the addition of these additional structures makes the sensor have better stability and reliability in practical applications and can bear more stable external pressure.

FIG. 34 shows a schematic structural diagram of a piezoelectric resonant pressure sensor 10 provided with a cover 500 but without a protective structure 600 .

The manufacturing process of piezoelectric resonant pressure sensors involves multiple complex processing steps and precise process control. The processing of piezoelectric resonant pressure sensors can be completed through the processing of SOI wafers, deposition of piezoelectric components, etching of electrode structures, and setting of protective structures and covers.

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.

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 (10)

1. A piezoelectric resonant pressure sensor, characterized in that it is applied to the core electronic industry, and 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, at least one resonant cavity is arranged inside the resonant component, a pressure cavity is opened on the side of the resonant component away from the piezoelectric component, and the pressure received by the pressure cavity can be transmitted to the resonant structure on one side of the resonant cavity; 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, wherein the resonant component comprises the resonant structure and the pressure sensitive structure connected to each other, the resonant structure is connected to the piezoelectric component, and the pressure sensitive structure is arranged on a side of the resonant structure away from the piezoelectric component; The pressure sensitive structure comprises a resonance layer, a buried oxide layer and a substrate layer connected in sequence, the resonance layer is connected to the resonance structure, the resonance cavity is opened in the resonance layer, the resonance structure closes the opening of the resonance cavity, and the pressure cavity is opened in the substrate layer. 3. The piezoelectric resonant pressure sensor according to claim 2, characterized in that the pressure cavity at least penetrates the substrate layer, and at most penetrates the buried oxide layer, and a pressure-sensitive film is formed in the region of the resonance layer corresponding to the pressure cavity; At least one of the resonance cavities is located on a 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 resonance structure. 4. The piezoelectric resonant pressure sensor according to claim 2, wherein the resonant structure comprises a fixed portion and a resonant film connected to each other, a first side of the fixed portion is connected to the piezoelectric component, and a second side of the fixed portion is connected to the pressure sensitive structure; The first side of the resonant film is connected to the piezoelectric component, and the second side of the resonant film closes or does not close the opening of the resonant cavity. 5. The piezoelectric resonant pressure sensor according to claim 2, wherein the resonant component is formed by processing two SOI wafers, and the two SOI wafers are respectively a first SOI wafer and a second SOI wafer; The pressure sensitive structure is formed by processing the first SOI wafer, the resonant structure is formed by processing the second SOI wafer, and the first device layer of the second SOI wafer is bonded to the second device layer of the first SOI wafer. 6. The piezoelectric resonant pressure sensor as described in claim 1 is characterized in that the resonant cavity is provided with at least one, and in the direction of the resonant component away from the piezoelectric component, the projection of at least one resonant cavity surrounds the outside of the projection of the pressure cavity. 7. The piezoelectric resonant pressure sensor as described in claim 1 is characterized in that the piezoelectric component 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. 8. The piezoelectric resonant pressure sensor according to claim 1, characterized in that a cover is provided on a side of the piezoelectric component 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, comprising: At least one piezoelectric resonant pressure sensor according to any one of claims 1 to 8; and At least one compensation sensor, wherein the compensation sensor is spaced apart from or integrated with the piezoelectric resonant pressure sensor; The compensation sensor may be affected by the environment, and the piezoelectric resonant pressure sensor can receive the pressure to be measured and the environmental influence. 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. 10. A method for preparing a piezoelectric resonant pressure sensor, characterized in that it is applicable to the piezoelectric resonant pressure sensor according to any one of claims 1 to 8; the method is used to process two SOI wafers into the piezoelectric resonant pressure sensor, and the method comprises: Taking a first SOI wafer, and setting the thickness of a first device layer of the first SOI wafer to be the thickness of the pressure sensitive film; Opening at least one resonant cavity on the first device layer; Taking a second SOI wafer, and setting the thickness of the second device layer of the second SOI wafer to the thickness of the resonant film; turning over the second SOI wafer and bonding the second device layer to the first device layer; Thinning the second SOI wafer until the second buried oxide layer is removed and the second device layer remains on the second SOI wafer; A piezoelectric component is processed on a side of the second device layer facing away from the first device layer, and an external conductive structure is reserved on the piezoelectric component.