Piezoelectric resonant pressure sensor and preparation method thereof

Abstract

The invention provides a piezoelectric resonant pressure sensor and a preparation method thereof, relates to the technical field of sensors, and aims to simplify the structure of the piezoelectric resonant pressure sensor and reduce the size of the piezoelectric resonant pressure sensor. The piezoelectric resonant pressure sensor comprises a pressure sensitive assembly and a piezoelectric assembly, and the pressure sensitive assembly is provided with a first surface and a second surface which are oppositely arranged. The pressure sensitive assembly is provided with a pressure cavity penetrating through the second surface, and to-be-detected pressure acts on the cavity wall, close to the first surface, of the pressure cavity. The piezoelectric assembly is arranged on the first surface and is electrically connected with an external circuit through the silicon through hole. The periphery of the piezoelectric assembly is supported on the first surface, and the middle area of the piezoelectric assembly is suspended on the first surface, so that a resonant cavity is formed between the middle area and the first surface. The orthographic projection of the resonant cavity on the second surface is at least partially overlapped with the orthographic projection of the pressure cavity on the second surface.

Description

Technical Field

[0001] The present application relates to the field of sensor technology, and in particular to a piezoelectric resonant pressure sensor and a preparation method thereof. Background Art

[0002] According to different working principles, pressure sensors can be divided into piezoelectric resonant pressure sensors, piezoresistive pressure sensors, capacitive pressure sensors, piezoelectric pressure sensors, etc. Among them, piezoelectric resonant pressure sensors have the advantages of good stability and high accuracy, and are widely used in areas with high accuracy requirements and harsh environments, such as aerospace, petroleum, etc.

[0003] The anchor point of the piezoelectric resonant pressure sensor can transfer the stress of the pressure sensitive film to the resonator, ensuring that the piezoelectric resonant pressure sensor remains stable during operation and improving the accuracy of pressure detection.

[0004] The existing piezoelectric resonant pressure sensor generally uses a support structure as an anchor point, which makes the structure of the piezoelectric resonant pressure sensor more complicated and the size of the piezoelectric resonant pressure sensor larger. Summary of the invention

[0005] The present application provides a piezoelectric resonant pressure sensor and a preparation method thereof, which are used to simplify the structure of the piezoelectric resonant pressure sensor and reduce the size of the piezoelectric resonant pressure sensor.

[0006] In a first aspect, the present application provides an example of a piezoelectric resonant pressure sensor, including a pressure-sensitive component and a piezoelectric component, wherein the pressure-sensitive component has a first surface and a second surface that are arranged opposite to each other. The pressure-sensitive component has a pressure cavity that runs through the second surface, and the pressure to be detected acts on the cavity wall of the pressure cavity close to the first surface. The piezoelectric component is arranged on the first surface, and the piezoelectric component is electrically connected to an external circuit through a silicon via. The piezoelectric component is supported on the first surface on all sides, and the middle area of ​​the piezoelectric component is suspended on the first surface to form a resonant cavity between the middle area and the first surface. The orthographic projection of the resonant cavity on the second surface at least partially overlaps with the orthographic projection of the pressure cavity on the second surface.

[0007] When the above technical solution is adopted, the middle area of ​​the piezoelectric component forms a resonator, and the side cavity wall of the resonant cavity forms an anchor point. There is no need to set up an additional supporting structure as an anchor point between the piezoelectric component and the pressure sensitive component, which can simplify the structure of the piezoelectric resonant pressure sensor and reduce the size of the piezoelectric resonant pressure sensor.

[0008] A pressure-sensitive film is formed between the cavity wall of the pressure cavity close to the first surface and the first surface. The pressure-sensitive film can withstand a large load. When a large pressure to be detected acts on the pressure-sensitive film, the pressure-sensitive film will not undergo a large deformation, thereby improving the pressure-bearing capacity of the pressure-sensitive film, expanding the range of pressures that can be detected by the piezoelectric resonant pressure sensor provided in the embodiment of the present application, improving the scope of application of the piezoelectric resonant pressure sensor provided in the embodiment of the present application, and ensuring the linearity of the piezoelectric resonant pressure sensor within the pressure measurement range.

[0009] In some possible implementations, the piezoelectric component includes a first conductive layer, a piezoelectric layer, and a second conductive layer, the first conductive layer and the second conductive layer are electrically connected to an external circuit through a through silicon via; the first conductive layer and the second conductive layer have different polarities. At least corresponding to the middle region, the first conductive layer, the piezoelectric layer, and the second conductive layer are stacked in sequence from the pressure sensitive component to the piezoelectric component. Moreover, corresponding to the middle region, the first conductive layer, the piezoelectric layer, and the second conductive layer protrude in a direction away from the pressure sensitive component to form a resonant cavity.

[0010] In some possible implementations, at least two through silicon vias are provided on the pressure sensitive component, the first conductive layer is electrically connected to the external circuit through at least one of the through silicon vias, and the second conductive layer is electrically connected to the external circuit through at least another through silicon via.

[0011] In some possible implementations, the piezoelectric resonant pressure sensor further includes a cover disposed on the first surface; a cover space is disposed on a side of the cover facing the first surface, and the piezoelectric component is located in the cover space.

[0012] When the above technical solution is adopted, on the one hand, the piezoelectric component is located in the cover space, and the cover can protect the piezoelectric component and ensure the stability of the working environment of the piezoelectric component, which can not only avoid damage to the piezoelectric component, but also avoid affecting the detection accuracy of the pressure to be detected. On the other hand, it can prevent impurities such as dust and particles from falling on the piezoelectric component and affecting the detection accuracy of the pressure to be detected.

[0013] In some possible implementations, at least two through silicon vias are provided on the cover, the first conductive layer is electrically connected to the external circuit through at least one of the through silicon vias, and the second conductive layer is electrically connected to the external circuit through at least another through silicon via.

[0014] When the above technical solution is adopted, the through silicon via can be set on the pressure sensitive component or on the cover, which enriches the setting positions of the through silicon via and facilitates selection according to actual conditions.

[0015] In some possible implementations, the cover is vacuum connected to the first surface;

[0016] The piezoelectric resonant pressure sensor also includes an air absorber, which is arranged in the cover space, and the air absorber is used to absorb gas after the cover is vacuum-connected to the pressure sensitive component.

[0017] When the above technical solution is adopted, the air getter is used to absorb the gas molecules released from the piezoelectric component, pressure sensitive component and other devices after the cover and the pressure sensitive component are sealed and connected, so that the inside of the piezoelectric resonant pressure sensor is maintained in a vacuum state, so as to ensure the vacuum degree of the vacuum chamber, ensure the measurement accuracy and sensitivity of the piezoelectric resonant pressure sensor, and extend the service life of the piezoelectric resonant pressure sensor.

[0018] In some possible implementations, a through groove is provided on the piezoelectric component, the through groove runs through the middle area and is connected to the resonant cavity.

[0019] In a second aspect, the present application provides an example method for preparing a piezoelectric resonant pressure sensor, comprising:

[0020] providing a first wafer;

[0021] A pressure cavity for receiving a pressure to be detected is formed on the first wafer, wherein the pressure cavity penetrates the substrate layer of the first wafer to obtain a pressure sensitive component;

[0022] A sacrificial layer is formed on the silicon structure layer of the first wafer; the orthographic projection of the sacrificial layer on the silicon structure layer at least partially overlaps with the orthographic projection of the pressure chamber on the silicon structure layer;

[0023] A piezoelectric component is formed on the sacrificial layer and the silicon structure layer, and the piezoelectric component is used to be electrically connected to an external circuit; the sacrificial layer corresponds to the middle area of ​​the piezoelectric component; the piezoelectric component includes a first conductive layer, a piezoelectric layer, and a second conductive layer; at least corresponding to the middle area, the first conductive layer, the piezoelectric layer, and the second conductive layer are stacked in sequence from the pressure sensitive component to the piezoelectric component;

[0024] Performing a first patterning process on the piezoelectric component to form a through groove in a middle region of the piezoelectric component, wherein the through groove penetrates the middle region and one end of the through groove extends to the sacrificial layer;

[0025] The sacrificial layer is released through the through grooves.

[0026] The beneficial effects of the method for preparing the piezoelectric resonant pressure sensor provided in the second aspect can refer to the beneficial effects of the piezoelectric resonant pressure sensor described in the first aspect above, and will not be elaborated here.

[0027] In some possible implementations, forming a piezoelectric component on the sacrificial layer and the silicon structure layer includes:

[0028] forming a first conductive layer on the sacrificial layer and the silicon structure layer;

[0029] forming a piezoelectric layer on the first conductive layer and the silicon structure layer;

[0030] A second conductive layer is formed on the piezoelectric layer and the silicon structure layer to obtain a piezoelectric component.

[0031] In some possible implementations, after forming the piezoelectric component on the sacrificial layer and the silicon structure layer, and before performing a first patterning process on the piezoelectric component to form a through groove in the middle region of the piezoelectric component, the method for preparing the piezoelectric resonant pressure sensor further includes: forming a first bonding ring on the silicon structure layer; the first bonding ring corresponds to the four edges of the silicon structure layer;

[0032] After the sacrificial layer is released through the through groove, the preparation method further comprises:

[0033] Providing a second wafer, on which a second bonding ring is disposed, and the first bonding ring matches the second bonding ring;

[0034] Performing a second patterning process on a side of the second wafer provided with the second bonding ring to obtain a cover space and obtain a cover;

[0035] The first bonding ring and the second bonding ring are bonded, and the piezoelectric component is located in the cover space. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A schematic top view of a piezoelectric resonant pressure sensor provided in an embodiment of the present application Figure 1 .

[0037] Figure 2 for Figure 1 Schematic diagram of the cross section at AA in the middle.

[0038] Figure 3 A schematic diagram of a piezoelectric resonant pressure sensor provided in an embodiment of the present application Figure 1 .

[0039] Figure 4 A schematic diagram of a piezoelectric resonant pressure sensor provided in an embodiment of the present application Figure 2 .

[0040] Figure 5 A schematic diagram of a piezoelectric resonant pressure sensor provided in an embodiment of the present application Figure 3 .

[0041] Figure 6 A schematic top view of a piezoelectric resonant pressure sensor provided in an embodiment of the present application Figure 2 .

[0042] Figure 7 A schematic top view of a piezoelectric resonant pressure sensor provided in an embodiment of the present application Figure 3 .

[0043] Figure 8 A schematic top view of a piezoelectric resonant pressure sensor provided in an embodiment of the present application Figure 4 .

[0044] Fig. 9 A bottom view schematic diagram of a piezoelectric resonant pressure sensor provided in an embodiment of the present application.

[0045] Fig.10 A schematic diagram of the positional relationship between a piezoelectric resonant pressure sensor and a pressure to be detected provided in an embodiment of the present application.

[0046] Fig.11 Taking a piezoelectric resonant pressure sensor provided in an embodiment of the present application as an example, a schematic diagram of disassembling and analyzing the pressure to be detected by the piezoelectric resonant pressure sensor provided in an embodiment of the present application Figure 1 .

[0047] Fig.12 Taking a piezoelectric resonant pressure sensor provided in an embodiment of the present application as an example, a schematic diagram of disassembling and analyzing the pressure to be detected by the piezoelectric resonant pressure sensor provided in an embodiment of the present application Figure 2 .

[0048] Fig.13 A step diagram of a method for preparing a piezoelectric resonant pressure sensor provided in an embodiment of the present application.

[0049] Figures 14 to 34 To prepare a piezoelectric resonant pressure sensor using the method provided in the embodiment of the present application, the following is prepared: Figure 3 Schematic diagram of the structure of the piezoelectric resonant pressure sensor process shown.

[0050] Figure 35 to Figure 55 To prepare a piezoelectric resonant pressure sensor using the method provided in the embodiment of the present application, the following is prepared: Figure 5 Schematic diagram of the structure of the piezoelectric resonant pressure sensor process shown.

[0051] Description of reference numerals:

[0052] 10-pressure sensitive component, 10'-first wafer, 11-pressure chamber, 12-silicon structure layer, 13-buried oxide layer, 14-substrate layer,

[0053] 15'-front third conductive layer, 15-first bonding ring;

[0054] 20-piezoelectric component, 21-first conductive layer, 21'-front first conductive layer, 211-connecting lead, 211'-connecting hole, 22-piezoelectric layer,

[0055] 22'-front piezoelectric layer, 23-second conductive layer, 23'-front second conductive layer, 24-resonant cavity, 25-through groove, 26-connecting lead;

[0056] 30-capping, 30'-second wafer, 31-capping space, 32-second bonding ring, 32'-front fourth conductive layer,

[0057] 40'-front lead electrode layer, 40-lead electrode;

[0058] 50- air suction piece;

[0059] 60-Through Silicon Via;

[0060] 70 - sacrificial layer, 70' - front sacrificial layer. DETAILED DESCRIPTION

[0061] In order to make the purpose, technical solution and advantages of the examples of this application clearer, the technical solution in the examples of this application will be clearly and completely described below in conjunction with the drawings in the examples of this application. Obviously, the described examples are part of the examples of this application, not all of them. Based on the examples in this application, all other examples obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0062] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used in the specification of the application herein are only for the purpose of describing specific examples and are not intended to limit this application; the terms "including" and "having" in the specification, claims and drawings of this application and any variations thereof are intended to cover non-exclusive inclusions.

[0063] Reference to "examples" herein means that a particular feature, structure, or characteristic described in conjunction with the examples may be included in at least one example of the present application. The appearance of the phrase "example" in various locations in the specification does not necessarily refer to the same example, nor is it an independent or alternative example that is mutually exclusive with other examples. It is explicitly and implicitly understood by those skilled in the art that the examples described herein may be combined with other examples.

[0064] The term "and / or" in this article is only a description of the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists, A and B exist at the same time, and B exists. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0065] The directional words appearing in the following description are all directions shown in the figures, and do not limit the specific structure of the piezoelectric resonant pressure sensor of the present application.

[0066] In addition, the terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects rather than to describe a specific order, and may explicitly or implicitly include one or more of the features.

[0067] In the description of the present application, unless otherwise specified, "plurality" means more than two (including two), and similarly, "multiple groups" means more than two groups (including two).

[0068] In the description of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, the "connection" or "connection" of a mechanical structure may refer to a physical connection. For example, the physical connection may be a fixed connection, such as a fixed connection through a barrier, such as a fixed connection through screws, bolts or other barrier; the physical connection may also be a detachable connection, such as a mutual snap-on or snap-fit ​​connection; the physical connection may also be an integral connection, such as a connection formed by welding, bonding or integral molding. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0069] The resonant pressure sensor indirectly measures the pressure to be detected by measuring the change in the resonant frequency of the structure. It has the advantages of high precision and good stability. It is suitable for scenarios with high precision requirements and harsh environments such as aerospace, oil and gas exploration, etc.

[0070] Existing resonant pressure sensors include electrostatic excitation-resistance detection type resonant pressure sensors, piezoelectric excitation-piezoelectric detection type resonant pressure sensors, electromagnetic drive-electromagnetic detection type resonant pressure sensors, optical drive-optical detection type resonant pressure sensors, and quartz material piezoelectric resonant pressure sensors, etc. The measurement structure can be a detection circuit or other structure that can detect the pressure to be detected.

[0071] The anchor point of the piezoelectric resonant pressure sensor can transfer the stress of the pressure sensitive film to the resonator, ensuring that the piezoelectric resonant pressure sensor remains stable during operation and improving the accuracy of pressure detection.

[0072] The existing piezoelectric resonant pressure sensor generally uses a support structure as an anchor point, which makes the structure of the piezoelectric resonant pressure sensor more complicated and the size of the piezoelectric resonant pressure sensor larger.

[0073] In view of the problems existing in the above-mentioned prior art, an embodiment of the present application provides a piezoelectric resonant pressure sensor, which can be combined with MEMS (Micro-Electro-Mechanical Systems) technology to achieve mass production of piezoelectric resonant pressure sensors and improve the production efficiency of piezoelectric resonant pressure sensors.

[0074] In order to enable those skilled in the art to better understand the solution of the present application, the piezoelectric resonant pressure sensor and the preparation method thereof provided in the embodiment of the present application will be clearly and completely described below in conjunction with the accompanying drawings.

[0075] See also Figures 1 to 5 As shown, the piezoelectric resonant pressure sensor provided in the embodiment of the present application includes a pressure sensitive component 10 and a piezoelectric component 20 .

[0076] The pressure sensitive component 10 has a first surface and a second surface that are arranged opposite to each other, and the piezoelectric component 20 is arranged on the first surface. The pressure sensitive component 10 has a pressure cavity 11 that penetrates the second surface, so that the pressure cavity 11 is a cavity with an opening, and the opening end of the pressure cavity 11 is located on the second surface, so that the pressure to be detected enters the pressure cavity 11 and acts on the cavity wall of the pressure cavity 11 close to the first surface, thereby realizing the detection of the pressure to be detected.

[0077] It should be pointed out that a pressure-sensitive film is formed between the cavity wall of the pressure cavity 11 close to the first surface and the first surface, and after the pressure to be detected enters the pressure cavity 11 , it acts on the pressure-sensitive film.

[0078] The pressure-sensitive film can withstand a large load. When a large pressure to be detected acts on the pressure-sensitive film, the pressure-sensitive film will not undergo a large deformation, thereby improving the pressure-bearing capacity of the pressure-sensitive film, expanding the range of pressures that can be detected by the piezoelectric resonant pressure sensor provided in the embodiment of the present application, improving the scope of application of the piezoelectric resonant pressure sensor provided in the embodiment of the present application, and ensuring the linearity of the piezoelectric resonant pressure sensor within the pressure measurement range.

[0079] In a specific implementation, the pressure sensitive component 10 can be processed from an SOI wafer. The structure of the pressure sensitive component 10 can be a cylindrical structure, a rectangular parallelepiped structure, a prismatic structure, etc., which is not specifically limited here.

[0080] When the pressure sensitive component 10 is processed from an SOI wafer, the pressure sensitive component 10 further includes a silicon structure layer 12, a buried oxide layer 13 and a substrate layer 14. Figures 2 to 5As shown. The silicon structure layer 12, the buried oxide layer 13 and the substrate layer 14 are stacked in sequence along the direction from the first surface to the second surface. The buried oxide layer 13 is an oxide layer formed in the bonding process when the silicon structure layer 12 and the substrate layer 14 are bonded, and can be used to accurately control the thickness of the silicon structure layer 12.

[0081] In this case, in the embodiment provided in the present application, the side of the silicon structure layer 12 away from the buried oxide layer 13 forms the first surface of the pressure sensitive component 10 , and the side of the substrate layer 14 away from the buried oxide layer 13 forms the second surface of the pressure sensitive component 10 .

[0082] In this way, the pressure cavity 11 is opened on the substrate layer 14. Specifically, the pressure cavity 11 can penetrate the substrate layer 14 along the direction from the first surface to the second surface. The cavity wall of the pressure cavity 11 close to the first surface is coplanar with the surface of the buried oxide layer 13 close to the substrate layer 14. Thus, at the position corresponding to the pressure cavity 11, a pressure-sensitive film is formed between the surface of the buried oxide layer 13 close to the substrate layer 14 and the first surface.

[0083] It can be further shown that the pressure chamber 11 is a space formed by the side of the buried oxide layer 13 close to the substrate layer 14 and the substrate layer 14 .

[0084] In addition, in the embodiments provided in the present application, the shape of the pressure chamber 11 may be cylindrical, the shape of the pressure chamber 11 may be prismatic, or the shape of the pressure chamber 11 may be irregular. Of course, the present invention is not limited thereto.

[0085] The central axis of the pressure chamber 11 may coincide with the central axis of the pressure sensitive component 10 , or they may be staggered.

[0086] The method of forming the pressure chamber 11 on the substrate layer 14 is not specifically limited here. As an example, dry etching or wet etching can be used to etch the side of the substrate layer 14 away from the buried oxide layer 13 to form the pressure chamber 11. In the embodiment provided in this application, dry etching is preferred.

[0087] The number of the pressure chambers 11 is not specifically limited here. For example, the number of the pressure chamber 11 may be one, and of course, a plurality of pressure chambers 11 may also be arranged at intervals.

[0088] In actual situations, the pressure sensitive component 10 may also only include a pressure sensitive film, in which case the pressure chamber 11 may be a space where the pressure sensitive film is away from the piezoelectric component 20. This is only an example and is not intended to be a specific limitation.

[0089] The pressure to be detected that enters the pressure chamber 11 and acts on the cavity wall of the pressure chamber 11 close to the first surface may be the pressure directly or indirectly applied to the pressure sensitive component 10 by the fluid, and the fluid may be liquid, gas, etc. Of course, the pressure to be detected may also be the pressure that acts on the pressure sensitive component 10 when the external mechanical structure directly contacts the cavity wall of the pressure chamber 11 close to the first surface.

[0090] When the pressure sensitive component 10 is processed from an SOI wafer, the piezoelectric component 20 is disposed on the first surface. Specifically, the piezoelectric component 20 is disposed on the silicon structure layer 12, and the silicon structure layer 12 serves as a supporting layer and can provide a stable supporting force for the piezoelectric component 20.

[0091] In the embodiment provided in the present application, the piezoelectric component 20 may be formed on the first surface by a deposition process.

[0092] As an example, the piezoelectric component 20 is electrically connected to the external circuit through the through silicon via 60. Through silicon via technology can greatly improve the integration of the piezoelectric resonant pressure sensor and reduce the geometric size and weight of the piezoelectric resonant pressure sensor by drilling holes in the device and filling them with conductive materials such as copper, tungsten, and polysilicon.

[0093] In a specific implementation, the through silicon via 60 can be opened on the pressure sensitive component 10, such as Figure 2 shown.

[0094] See also Figures 2 to 5 As shown, the four sides of the piezoelectric component 20 are supported on the first surface, and the middle area of ​​the piezoelectric component 20 is suspended on the first surface, so as to form a resonant cavity 24 between the middle area and the first surface. There is a gap between the middle area of ​​the piezoelectric component 20 and the first surface, and the gap is the resonant cavity 24 described in the embodiment of the present application.

[0095] In this way, the middle area of ​​the piezoelectric component 20 forms the resonator of the piezoelectric resonant pressure sensor provided in the embodiment of the present application, and the part of the piezoelectric component 20 used to surround the side wall of the resonant cavity 24 forms the anchor point of the piezoelectric resonant pressure sensor provided in the embodiment of the present application, one end of the anchor point is supported on the first surface of the pressure sensitive component 10, and the other end of the anchor point is connected to the resonator. The anchor point serves as a bridge between the pressure sensitive component 10 and the resonator, and the resonator is suspended and supported on the pressure sensitive component 10. The anchor point plays the role of connecting the pressure sensitive component 10 and supporting the resonator.

[0096] Furthermore, the orthographic projection of the resonant cavity 24 on the second surface at least partially overlaps with the orthographic projection of the pressure cavity 11 on the second surface. In other words, the orthographic projection of the resonant cavity 24 on the second surface at least partially falls into the orthographic projection of the pressure cavity 11 on the second surface. This ensures that the pressure-sensitive film can be deformed to bend closer to the piezoelectric component 20 when subjected to the pressure to be detected, that is, the resonant cavity 24 can provide deformation space for the pressure-sensitive film.

[0097] At the same time, since the side cavity wall of the resonance cavity 24 forms an anchor point, when the orthographic projection of the resonance cavity 24 on the second surface at least partially overlaps with the orthographic projection of the pressure cavity 11 on the second surface, the pressure sensitive film partially overlaps with the resonance cavity 24, which can ensure that the anchor point is in contact with the pressure sensitive film, and further ensure that the anchor point transfers the stress generated by the pressure to be detected on the pressure sensitive film to the resonator, so that the resonator is subjected to stress, thereby realizing a change in the vibration frequency of the resonator.

[0098] For example, the orthographic projection of the resonant cavity 24 on the second surface may completely fall within the orthographic projection range of the pressure cavity 11 on the second surface. In this case, the geometric center of the orthographic projection of the resonant cavity 24 on the second surface may overlap with the geometric center of the orthographic projection of the pressure cavity 11 on the second surface. In this case, the orthographic projections of the geometric center of the resonant cavity 24, the geometric center of the pressure cavity 11, the geometric center of the pressure sensitive component 10, and the geometric center of the piezoelectric component 20 on the second surface may all overlap, or may not overlap or partially overlap.

[0099] The orthographic projection of the resonance cavity 24 on the second surface may partially fall within the orthographic projection range of the pressure cavity 11 on the second surface. In other words, the orthographic projection of the resonance cavity 24 on the second surface partially overlaps with the orthographic projection of the pressure cavity 11 on the second surface.

[0100] The embodiment of the present application does not specifically limit the positional relationship between the resonance cavity 24 and the pressure cavity 11, as long as it ensures that the orthographic projection of at least part of the resonance cavity 24 on the second surface coincides with the orthographic projection of the pressure cavity 11 on the second surface, thereby ensuring that the pressure to be detected entering the pressure cavity 11 can be transmitted to the resonator through the anchor point and converted into stress on the resonator to cause a change in the vibration frequency of the resonator, and then the pressure to be detected can be detected through the change in the vibration frequency of the resonator.

[0101] In a specific implementation, the shape of the resonance cavity 24 may be the same as the shape of the pressure cavity 11 , or may be different. This is not specifically limited here, and the specific shape shall be subject to the actual situation.

[0102] The number of the resonant cavities 24 may be one or more, and this example of the present application does not limit this.

[0103] In the embodiments provided in this application, the formation method of the resonant cavity 24 is not specifically limited here.

[0104] For example, a groove may be directly provided on one side of the piezoelectric component 20 close to the pressure sensitive component 10. When the piezoelectric component 20 is disposed on the first surface, a resonant cavity 24 is formed between the groove wall of the groove and the first surface.

[0105] Before forming the piezoelectric component 20 on the pressure sensitive component 10 through a deposition process, a sacrificial layer may be first formed on the pressure sensitive component 10, and after the piezoelectric component 20 is formed, the sacrificial layer may be released and removed, and the space occupied by the sacrificial layer is the resonant cavity 24. At the same time, after the sacrificial layer is released and removed, the portion of the piezoelectric component 20 used to surround the side wall of the resonant cavity 24 forms an anchor point.

[0106] It should be noted that, in actual situations, the external circuit includes a detection circuit and a drive circuit. The detection circuit can be a circuit for detecting the magnitude of current, a circuit for detecting the magnitude of voltage, or a circuit for detecting the amount of charge. The embodiment of the present application does not limit the specific type of the detection circuit, as long as the external circuit can detect the electrical signal output by the piezoelectric component 20. The drive circuit is a circuit that drives the resonator of the piezoelectric component 20 to vibrate.

[0107] In the case of the above-mentioned piezoelectric resonant pressure sensor, the resonator has a certain resonant frequency. When the piezoelectric component 20 is connected to the driving circuit, when the frequency of the electrical signal applied to the resonator by the driving circuit is consistent with the resonant frequency, the resonant frequency of the resonator is reached, and the vibration frequency of the resonator is maximum. When the pressure to be detected enters the pressure chamber 11 from the open end of the pressure chamber 11 and acts on the cavity wall of the pressure chamber 11 close to the first surface, the pressure sensitive film is deformed by the pressure to be detected and bends and deforms in the direction close to the piezoelectric component 20. The pressure sensitive film can transfer deformation and stress to the anchor point. Further, the anchor point transfers pressure and deformation to the resonator, causing the vibration frequency of the resonator to change. The detection circuit obtains data such as the size and direction of the pressure to be detected by receiving and analyzing the changes in the vibration frequency of the resonator.

[0108] At the same time, the anchor point can isolate the pressure to be detected and the resonator, preventing the pressure to be detected from directly acting on the resonator, thereby improving the pressure-bearing capacity of the piezoelectric resonant pressure sensor provided in the embodiment of the present application and increasing the range of pressure to be detected that the piezoelectric resonant pressure sensor can measure.

[0109] The setting of the resonant cavity 24 can provide a vibration space for the resonator, reduce the possibility of the resonator causing a large deformation due to vibration, and then causing damage to the piezoelectric component 20, increase the range of pressure to be detected that the piezoelectric resonant pressure sensor can measure, expand the measurement range of the piezoelectric resonant pressure sensor, and expand the scope of application of the piezoelectric resonant pressure sensor.

[0110] Moreover, in the embodiment provided in the present application, the side wall of the resonant cavity 24 forms an anchor point, and there is no need to set an additional support structure as an anchor point between the piezoelectric component 20 and the pressure sensitive component 10, which can simplify the structure of the piezoelectric resonant pressure sensor and reduce the size of the piezoelectric resonant pressure sensor. This solves the problem that the existing piezoelectric resonant pressure sensor has a complex structure and a large size and cannot be miniaturized.

[0111] The pressure-sensitive film provided in the embodiment of the present application can withstand a large load. When a large pressure to be detected acts on the pressure-sensitive film, the pressure-sensitive film will not undergo a large deformation, thereby improving the pressure-bearing capacity of the pressure-sensitive film, expanding the range of pressures to be detected that can be detected by the piezoelectric resonant pressure sensor provided in the embodiment of the present application, and improving the scope of application of the piezoelectric resonant pressure sensor provided in the embodiment of the present application, thereby ensuring the linearity of the piezoelectric resonant pressure sensor within the pressure measurement range.

[0112] In some possible implementations, see Figures 2 to 5 As shown, the piezoelectric component 20 includes a first conductive layer 21 , a piezoelectric layer 22 and a second conductive layer 23 . The first conductive layer 21 and the second conductive layer 23 are electrically connected to an external circuit through a through silicon via 60 .

[0113] The first conductive layer 21 and the second conductive layer 23 have different polarities. The first conductive layer 21 can be electrically connected to an external circuit, and the second conductive layer 23 can be grounded. Of course, it can also be set that the first conductive layer 21 is grounded and the second conductive layer 23 is electrically connected to an external circuit to achieve electrical connection among the first conductive layer 21, the piezoelectric layer 22, and the second conductive layer 23.

[0114] In a specific implementation, the piezoelectric layer 22 is the main functional layer of the piezoelectric component 20 , and can realize the positive piezoelectric effect and the inverse piezoelectric effect in cooperation with the first conductive layer 21 and the second conductive layer 23 , thereby realizing the sensing of the pressure to be detected.

[0115] The piezoelectric layer 22 is a piezoelectric thin film material, and the specific material of the piezoelectric layer 22 can be AlN (aluminum nitride), ScAlN (scandium-doped aluminum nitride), PZT (lead zirconate titanate), ZnO (zinc oxide), LiNbO3 (lithium niobate), etc. The material of the piezoelectric layer 22 is preferably AlN or ScAlN.

[0116] Due to the piezoelectricity of the piezoelectric film material, when the piezoelectric layer 22 receives pressure, an electric potential difference can be generated on the two opposite sides of the piezoelectric layer 22. By utilizing the positive piezoelectric effect and the inverse piezoelectric effect of the piezoelectric layer 22, relevant parameters of the pressure to be detected can be obtained. The relevant parameters may include the numerical size of the pressure to be detected and the direction parameters of the pressure to be detected.

[0117] The first conductive layer 21 and the second conductive layer 23 can both be used as driving electrodes for driving the resonator to vibrate. In the embodiment provided in the present application, the second conductive layer 23 is used as the driving electrode for example.

[0118] When the second conductive layer 23 is a driving electrode, after the second conductive layer 23 is electrically connected to an external circuit, the second conductive layer 23 can drive the piezoelectric layer 22, using the inverse piezoelectric effect of the piezoelectric layer 22 to cause the resonator to vibrate, and at the same time use the direct piezoelectric effect of the piezoelectric layer 22 to detect the vibration of the resonator.

[0119] In a specific implementation, the second conductive layer 23 may include a top electrode, such as Figure 6 The second conductive layer 23 may also include two top electrodes, such as Figure 1 , Figure 7 and Figure 8 Of course, the second conductive layer 23 may also include three, four or more top electrodes, which is not specifically limited here.

[0120] It is worth noting that Figure 6 As shown in Figure 1, the top electrode is in the shape of a cross. Figure 1 As shown in FIG, the top electrode is in a right angle shape, and the two top electrodes are placed together in a cross shape. Figure 7 As shown in FIG. 1 , the top electrode is in a straight line shape, and the two top electrodes are arranged opposite to each other. Figure 8 As shown, the top electrode is in a tuning fork-shaped structure, and the two top electrodes are arranged opposite to each other. The shape and combination of the top electrodes are not limited thereto, and are subject to actual conditions.

[0121] When the second conductive layer 23 includes a top electrode, the top electrode not only functions as a driving electrode, but also functions as a detecting electrode.

[0122] Specifically, when the top electrode is electrically connected to the driving circuit, the resonator can be driven to vibrate, and the top electrode plays the role of a driving electrode. When the top electrode is electrically connected to the detection circuit, the vibration signal of the resonator can be output to obtain data of the pressure to be detected. At this time, the top electrode plays the role of a detection electrode.

[0123] In specific operation, the one top electrode can be set to be alternately electrically connected to the driving circuit and the detection circuit. For example, the one top electrode can be set to be electrically connected to the driving circuit within the first 0.5 second, to be electrically connected to the detection circuit within the second 0.5 second, to be electrically connected to the driving circuit within the third 0.5 second, and to be electrically connected to the detection circuit within the fourth 0.5 second, and the electrical connections between the one top electrode and the driving circuit and the detection circuit are set at this interval.

[0124] When the second conductive layer 23 includes two top electrodes, one top electrode may be provided as a driving electrode electrically connected to a driving circuit, and the other top electrode may be provided as a detecting electrode electrically connected to a detecting circuit.

[0125] When the second conductive layer 23 includes more top electrodes, a portion of the top electrodes may be set as driving electrodes electrically connected to the driving circuit, and another portion of the top electrodes may be set as detecting electrodes electrically connected to the detecting circuit.

[0126] The first conductive layer 21 and the second conductive layer 23 are both made of conductive metals. For example, the first conductive layer 21 and the second conductive layer 23 can be made of Mo, Au, Pt, Al, etc., preferably Mo.

[0127] See also Figure 2 and Figure 3 As shown, at least corresponding to the middle region, the first conductive layer 21, the piezoelectric layer 22 and the second conductive layer 23 are stacked in sequence from the pressure sensitive component 10 to the piezoelectric component 20. Moreover, corresponding to the middle region, the first conductive layer 21, the piezoelectric layer 22 and the second conductive layer 23 protrude in the direction away from the pressure sensitive component 10 to form a resonant cavity 24.

[0128] The thickness of the first conductive layer 21 is uniform, the thickness of the piezoelectric layer 22 is uniform, and the thickness of the second conductive layer 23 is uniform.

[0129] In this case, the piezoelectric component 20 can be formed by a deposition process. Specifically, first, a sacrificial layer is deposited on the first surface, and then a first conductive layer 21, a piezoelectric layer 22, and a second conductive layer 23 are sequentially deposited on the sacrificial layer and the first surface, and then the sacrificial layer is released to form the piezoelectric component 20 provided in the embodiment of the present application. Compared with the traditional mechanical processing method for processing the piezoelectric component 20, it can more efficiently utilize raw materials, improve production efficiency and product quality, and at the same time, it can increase the range of materials that can be used for the piezoelectric component 20.

[0130] It should be noted that the thickness of the first conductive layer 21 is the size of the first conductive layer 21 in the direction from the first surface to the second surface. Similarly, the thickness of the piezoelectric layer 22 is the size of the piezoelectric layer 22 in the direction from the first surface to the second surface. The thickness of the second conductive layer 23 is the size of the second conductive layer 23 in the direction from the first surface to the second surface.

[0131] Based on the above-mentioned piezoelectric resonant pressure sensor, the resonator is a multilayer structure formed by the first conductive layer 21, the piezoelectric layer 22, and the second conductive layer 23, and the resonator is supported on the pressure sensitive component 10 by an anchor point. The resonator has a certain resonant frequency. When the frequency of the voltage applied by the driving circuit is consistent with the resonant frequency, the vibration of the resonator will reach the maximum, that is, resonance, by utilizing the inverse piezoelectric effect of the piezoelectric layer 22. At this time, the resonant frequency is:

[0132]

[0133] In the formula, f r is the resonant frequency, μ n is a constant set when solving the Bessel function, t is the thickness of the resonator, r is the radius of the resonant cavity 24, E is the Young's modulus, ρ is the complex density of the resonator, and δ is the Poisson's ratio.

[0134] It should be noted that when the second conductive layer 23 includes a plurality of top electrodes, a portion of the top electrodes can be set as drive electrodes electrically connected to the drive circuit, and another portion of the top electrodes can be set as detection electrodes electrically connected to the detection circuit. When the drive electrode drives the resonator to vibrate, its vibration will also be detected by the detection electrode. Due to the positive piezoelectric effect of the piezoelectric material, an electrical signal will be generated on the detection electrode, and the electrical signal can be used to detect the resonant frequency of the resonator without the need to arrange an additional detection circuit. However, the pressure sensor in the prior art generally requires an additional detection circuit to be set up. For example, a resistance detection type piezoelectric sensor needs to set up a Wheatstone bridge, and a capacitance detection type pressure sensor needs to set up a capacitance bridge, etc. The components and circuits are relatively complex, which is not conducive to simplifying the structure of the sensor.

[0135] In an alternative approach, see Figure 2 and Figure 3 As shown, at least two through silicon vias 60 are provided on the pressure sensitive component 10 , the first conductive layer 21 is electrically connected to the external circuit through at least one of the through silicon vias 60 , and the second conductive layer 23 is electrically connected to the external circuit through at least another through silicon via 60 .

[0136] One end of the through silicon via 60 disposed on the pressure sensitive component 10 passes through the first surface, and the other end passes through the second surface.

[0137] The number of through silicon vias 60 may be two, three, four or more. The number of through silicon vias 60 for connecting to the second conductive layer 23 may be the same as the number of top electrodes included in the second conductive layer 23, and the number of through silicon vias 60 for connecting to the first conductive layer 21 may be one, two or more, which is not specifically limited here.

[0138] In addition, if Figure 2and Figure 3 As shown, a plurality of lead electrodes 40 are further provided on the pressure sensitive component 10, and the lead electrodes 40 cooperate with the through silicon vias 60. The number of the lead electrodes 40 is not specifically limited here, and the number of the lead electrodes 40 may be the same as the number of the through silicon vias 60, and the lead electrodes 40 may correspond to the through silicon vias 60 one by one, that is, one lead electrode 40 corresponds to one through silicon via 60, and it should be understood that the number of the lead electrodes 40 may also be different from the number of the through silicon vias 60.

[0139] The lead electrode 40 is electrically connected to the first conductive layer 21 and the second conductive layer 23 through the through silicon via 60, so as to electrically connect the first conductive layer 21 and the second conductive layer 23 to an external circuit. Meanwhile, the lead electrode 40 can also be used as a pad for subsequent wire bonding.

[0140] like Fig. 9 As shown, exemplarily, the number of lead electrodes 40 is six, of which four lead electrodes 40 are electrically connected to the second conductive layer 23 through corresponding four through silicon vias 60, of which at least one lead electrode 40 is connected to a driving electrode for driving the resonator to vibrate through a corresponding through silicon via 60, and another at least one lead electrode 40 is connected to a detection electrode for detection through a corresponding through silicon via 60. The other two lead electrodes 40 of the six lead electrodes 40 are electrically connected to the first conductive layer 21 through corresponding two through silicon vias 60.

[0141] The material of the lead electrode 40 is a conductive metal. For example, the material of the lead electrode 40 may be Al, Au, Pt, etc., preferably Al or Au.

[0142] As a possible implementation, see Figures 3 to 5 As shown, the piezoelectric resonant pressure sensor further includes a cover 30 disposed on the first surface. A cover space 31 is disposed on one side of the cover 30 facing the first surface, and the piezoelectric component 20 is located in the cover space 31.

[0143] The cover 30 is provided. On the one hand, the piezoelectric component 20 is located in the cover space 31. The cover 30 can protect the piezoelectric component 20 and ensure the stability of the working environment of the piezoelectric component 20, which can not only avoid damage to the piezoelectric component 20, but also avoid affecting the detection accuracy of the pressure to be detected. On the other hand, it can prevent impurities such as dust and particles from falling on the piezoelectric component 20 and affecting the detection accuracy of the pressure to be detected.

[0144] In a specific implementation, the cover 30 can be fixedly connected to the pressure sensitive component 10 by bonding, welding, clamping, etc., preferably bonding.

[0145] The material of the cover 30 can be silicon or glass, etc., which is not specifically limited here.

[0146] In the embodiment provided in the present application, the cover 30 is made of a silicon wafer or a glass wafer, and the cover 30 and the pressure sensitive component 10 can be bonded together.

[0147] Specifically, see Figures 1 to 4 As shown, a first bonding ring 15 is provided on the first surface of the pressure sensitive component 10, and the first bonding ring 15 corresponds to the periphery of the pressure sensitive component 10. Accordingly, in order to bond the cover 30 to the pressure sensitive component 10, see Figure 3 As shown, a second bonding ring 32 is correspondingly provided on the piezoelectric component 20 , and the first bonding ring 15 and the second bonding ring 32 match each other.

[0148] The material of the first bonding ring 15 may be Al, and the material of the second bonding ring 32 may be Ge. Alternatively, the material of the first bonding ring 15 is Ge, and the material of the second bonding ring 32 is Al, so that the first bonding ring 15 and the second bonding ring 32 are Ge-Al bonded. Of course, the first bonding ring 15 and the second bonding ring 32 may also be melt bonded, Au-Au bonded, or anodic bonded, etc., which is not specifically limited in this application.

[0149] In another optional embodiment, at least two through silicon vias 60 are disposed on the cover 30 , wherein at least one through silicon via 60 is electrically connected to the first conductive layer 21 , and at least another through silicon via 60 is electrically connected to the second conductive layer 23 .

[0150] It should be noted that when the piezoelectric resonant pressure sensor provided in the embodiment of the present application includes a cover 30, the through silicon vias 60 can be disposed on the pressure sensitive component 10, such as Figure 3 The through silicon vias 60 may also be disposed on the cover 30, as shown in FIG. Figure 4 and Figure 5 shown.

[0151] Of course, in a specific implementation, part of the TSVs 60 may be disposed on the pressure sensitive component 10 , and another part of the TSVs 60 may be disposed on the cover 30 .

[0152] See also Figure 4 and Figure 5 As shown, the through silicon vias 60 are all arranged on the cover 30. One end of the through silicon via 60 arranged on the cover 30 passes through a side of the cover 30 close to the pressure sensitive component 10, and the other end passes through a side of the cover 30 away from the pressure sensitive component 10.

[0153] The first conductive layer 21 is electrically connected to an external circuit through at least one through silicon via 60 , and the second conductive layer 23 is electrically connected to an external circuit through at least another through silicon via 60 .

[0154] The number of through silicon vias 60 provided on the cover 30 may be two, three, four or more. The number of through silicon vias 60 for connecting to the second conductive layer 23 may be the same as the number of top electrodes included in the second conductive layer 23, and correspond one to one. The number of through silicon vias 60 for connecting to the first conductive layer 21 may be one, two or more, which is not specifically limited here.

[0155] Likewise, if Figure 4 and Figure 5 As shown, a plurality of lead electrodes 40 are further provided on the pressure sensitive component 10, and the lead electrodes 40 cooperate with the through silicon vias 60. The number of the lead electrodes 40 is not specifically limited here, and the number of the lead electrodes 40 may be the same as the number of the through silicon vias 60, and the lead electrodes 40 may correspond to the through silicon vias 60 one by one, that is, one lead electrode 40 corresponds to one through silicon via 60, and it should be understood that the number of the lead electrodes 40 may be different from the number of the through silicon vias 60.

[0156] The lead electrode 40 is electrically connected to the first conductive layer 21 and the second conductive layer 23 through the through silicon via 60, so as to electrically connect the first conductive layer 21 and the second conductive layer 23 to an external circuit. Meanwhile, the lead electrode 40 can also be used as a pad for subsequent wire bonding.

[0157] It should be noted that see Figure 4 As shown, the silicon through via 60 is arranged on the cover 30, and the material of the second conductive layer 23 can be the same as the material of the first bonding ring 15. In this case, a connecting hole is opened on the piezoelectric layer 22. When the second conductive layer 23 is deposited on the piezoelectric layer 22 and the first surface using a deposition process, part of the metal fills the connecting hole to form a connecting lead 211, and the connecting lead 211 is electrically connected to the first conductive layer 21. In addition, at the position of the silicon through via 60 corresponding to the connecting hole and matching the first conductive layer 21, a connecting lead 26 is formed, one end of the connecting lead 26 is electrically connected to the silicon through via 60, and the other end of the connecting lead 26 is electrically connected to the connecting lead 211, so as to realize the electrical connection between the first conductive layer 21 and the silicon through via 60.

[0158] In addition, see Figure 5 As shown, the silicon through via 60 is provided on the cover 30, and the material of the second conductive layer 23 and the material of the first bonding ring 15 can be different. In this case, similarly, a connecting hole is provided on the piezoelectric layer 22, and when the second conductive layer 23 is deposited on the piezoelectric layer 22 and the first surface by a deposition process, part of the metal fills the connecting hole to form a connecting lead 211, and the connecting lead 211 is electrically connected to the first conductive layer 21.

[0159] At the same time, a connection seat is provided at a position corresponding to the connecting lead 211, and the connection seat is electrically connected to the connecting lead 211. The material of the connection seat, the material of the second conductive layer 23 and the material of the connecting lead 211 are the same.

[0160] Afterwards, a third conductive layer is continuously deposited on the second conductive layer 23 and the first surface, and the third conductive layer is etched to form a connecting lead 26 .

[0161] In this example, not only is a connecting lead 26 provided at the position corresponding to the connection base and the through silicon via 60 matching the first conductive layer 21, one end of the connecting lead 26 is electrically connected to the through silicon via 60, and the other end of the connecting lead 26 is electrically connected to the connection base, so as to realize the electrical connection between the first conductive layer 21 and the through silicon via 60. Moreover, a connecting lead 26 is also provided at the position corresponding to the second conductive layer 23 and the through silicon via 60 matching the second conductive layer 23, such as Figure 5 As shown, one end of the connecting lead 26 is electrically connected to the through silicon via 60 , and the other end of the connecting lead 26 is electrically connected to the second conductive layer 23 , thereby achieving electrical connection between the second conductive layer 23 and the through silicon via 60 .

[0162] As a possible implementation, the cover 30 is connected to the first surface in a vacuum. At this time, a vacuum cavity can be formed between the cover 30 and the first surface, and the piezoelectric component 20 is located in the vacuum cavity. The working environment of the piezoelectric component 20 is a vacuum environment, which increases the value corresponding to the quality factor of the piezoelectric resonant pressure sensor, ensures the working performance of the piezoelectric resonant pressure sensor, and improves the measurement accuracy of the pressure to be detected.

[0163] Further, see Figures 3 to 5 As shown, the piezoelectric resonant pressure sensor provided in the embodiment of the present application further includes an air absorber 50 , which is disposed in the cover space 31 , and is used to absorb gas after the cover 30 is vacuum-connected to the pressure sensitive component 10 .

[0164] In a specific implementation, the getter 50 may be a thin film getter or other structure capable of maintaining a vacuum inside the piezoelectric resonant pressure sensor.

[0165] Specifically, the suction member 50 is used to absorb the gas molecules released from the piezoelectric component 20, the pressure sensitive component 10 and other devices after the cover 30 and the pressure sensitive component 10 are vacuum connected, so that the inside of the piezoelectric resonant pressure sensor is maintained in a vacuum state, so as to ensure the vacuum degree of the vacuum chamber, ensure the measurement accuracy and sensitivity of the piezoelectric resonant pressure sensor, and extend the service life of the piezoelectric resonant pressure sensor.

[0166] The suction member 50 is mounted on the inner wall of the cover 30. The suction member 50 can be arranged on the cavity wall of the vacuum cavity away from the first surface. Of course, the suction member 50 can also be arranged on the side cavity wall of the vacuum cavity, which is not specifically limited here.

[0167] It should be noted that the cover space 31 between the cover 30 and the pressure sensitive component 10 provided in the embodiment of the present application can maintain a vacuum to form a vacuum cavity. Of course, the cover space 31 can also be filled with a medium.

[0168] When the cover space 31 is a vacuum chamber, the piezoelectric resonant pressure sensor provided in the embodiment of the present application is an absolute pressure sensor. The absolute pressure sensor is used to measure absolute pressure and can convert the pressure to be detected into an equivalent electrical signal output.

[0169] When the cover space 31 is filled with a medium, the cover space 31 has a certain pressure value. The piezoelectric resonant pressure sensor provided in the embodiment of the present application is a relative pressure sensor, and the measurement result of the relative pressure sensor is relative to the pressure in the cover space 31.

[0170] Users can select a suitable absolute pressure sensor or relative pressure sensor according to their needs. The present application example does not limit whether the cover space 31 of the piezoelectric resonant pressure sensor is filled with a medium.

[0171] In some embodiments, see Figures 2 to 5 A through groove 25 is formed on the piezoelectric component 20 . The through groove 25 passes through the middle area and is connected to the resonant cavity 24 .

[0172] The number of the through slots 25 may be one, two, three or more, which is not specifically limited here.

[0173] For ease of understanding, the working principle of the piezoelectric resonant pressure sensor provided in the embodiment of the present application is described below in a possible implementation manner. Of course, this is not a specific limitation here.

[0174] After the second conductive layer 23 is connected to the driving circuit, the resonator vibrates, and the vibration frequency of the resonator is set to the resonance frequency through a phase-locked loop or other technology.

[0175] like Fig.10 As shown, the pressure sensitive component 10 inputs the pressure P to be detected through the pressure chamber 11. The pressure P to be detected acts on the pressure sensitive film, which can cause the pressure sensitive film to bend and deform in the direction close to the piezoelectric component 20 and transfer the stress to the anchor point.

[0176] Fig.11 and Fig.12The stress analysis of the anchor point is shown. The stress acting on the anchor point is mainly divided into two aspects. One is that when the pressure sensitive film is subjected to the pressure P to be detected, the pressure sensitive film bends and deforms in the direction close to the piezoelectric component 20, driving the anchor point to move away from the first surface, further lifting the resonator, and generating stress σ1 on the resonator, as shown in Fig.11 As shown. The second is that when the pressure sensitive film is subjected to the pressure to be detected, the anchor point tangentially deforms and stretches the resonator, and the stress σ2 generated on the resonator is as follows: Fig.12 The above two stresses act on the resonator together, causing the resonant frequency of the resonator to change. The detection circuit receives the vibration signal of the resonator and obtains the data of the pressure to be detected according to the change of the vibration signal of the resonator.

[0177] As a possible implementation, see Fig.13 As shown, the present application example provides a method for preparing a piezoelectric resonant pressure sensor, comprising the following steps:

[0178] Step S10, providing a first wafer 10', such as Fig.14 and Fig.35 shown.

[0179] The first wafer 10 ′ may be a cylindrical structure, a rectangular parallelepiped structure, a prismatic structure, etc., which is not specifically limited here.

[0180] When the first wafer 10 ′ may be an SOI wafer, the first wafer 10 ′ includes a silicon structure layer 12 , a buried oxide layer 13 and a substrate layer 14 which are stacked.

[0181] Step S20, forming a pressure chamber 11 for receiving the pressure to be detected on the first wafer 10', the pressure chamber 11 penetrates the substrate layer 14 of the first wafer 10', and obtaining a pressure sensitive component 10, such as Fig.17 and Fig.36 shown.

[0182] A pressure-sensitive film of a piezoelectric resonant pressure sensor is formed between the cavity wall of the pressure cavity 11 close to the silicon structure layer 12 and a surface of the silicon structure layer 12 away from the substrate layer 14 .

[0183] In specific implementation, the pressure chamber 11 can be formed on the substrate layer 14 by an etching process. Specifically, dry etching or wet etching can be used, and dry etching is preferred.

[0184] Step S30, forming a sacrificial layer 70 on the silicon structure layer 12 of the first wafer 10'; the orthographic projection of the sacrificial layer 70 on the silicon structure layer 12 at least partially overlaps with the orthographic projection of the pressure chamber 11 on the silicon structure layer 12, such as Fig.18 , Fig.19 , Fig.37 and Fig.38shown.

[0185] During specific implementation, a deposition process may be used to form the sacrificial layer 70 on the silicon structure layer 12 .

[0186] The material of the sacrificial layer 70 may be PSG (phosphosilicate glass), or other sacrificial layer 70 materials, such as SiO 2 , Ni, etc.

[0187] Step S40, forming a piezoelectric component 20 on the sacrificial layer 70 and the silicon structure layer 12, the piezoelectric component 20 is used to be electrically connected to an external circuit. The sacrificial layer 70 corresponds to the middle region of the piezoelectric component 20. The piezoelectric component 20 includes a first conductive layer 21, a piezoelectric layer 22, and a second conductive layer 23, at least corresponding to the middle region, and the first conductive layer 21, the piezoelectric layer 22, and the second conductive layer 23 are stacked in sequence from the pressure sensitive component 10 to the piezoelectric component 20, see FIG. Figure 20 to Figure 25 as well as Figures 39 to 46 .

[0188] The piezoelectric component 20 may be electrically connected to an external circuit directly or indirectly. In the embodiment provided in the present application, the piezoelectric component 20 is electrically connected to an external circuit through a through silicon via 60 provided on the first wafer 10'.

[0189] The first conductive layer 21 and the second conductive layer 23 are used to be electrically connected to an external circuit, and the polarities of the first conductive layer 21 and the second conductive layer 23 are different. The first conductive layer 21 can be electrically connected to an external circuit, and the second conductive layer 23 can be grounded. Of course, it can also be set that the first conductive layer 21 is grounded, and the second conductive layer 23 is electrically connected to an external circuit.

[0190] The piezoelectric layer 22 is a main functional layer of the piezoelectric component 20 , and can realize the positive piezoelectric effect and the inverse piezoelectric effect in cooperation with the first conductive layer 21 and the second conductive layer 23 , thereby realizing the detection of the pressure to be detected.

[0191] Step S60, performing a first patterning process on the piezoelectric component 20 to form a through groove 25 in the middle region of the piezoelectric component 20, wherein the through groove 25 penetrates the middle region and one end of the through groove 25 extends to the sacrificial layer 70, see Fig.28 and Fig.46 .

[0192] Step S70, releasing the sacrificial layer 70 through the through groove 25, see Fig.29 and Fig.48 .

[0193] When the above technical solution is adopted, a sacrificial layer 70 is formed on the silicon structure layer 12 of the first wafer 10 ′, and after the piezoelectric component 20 is formed, the sacrificial layer 70 is removed.

[0194] The main function of the sacrificial layer 70 is to provide necessary structural support for the subsequent formation of the piezoelectric component 20. Since the sacrificial layer 70 corresponds to the middle area of ​​the piezoelectric component 20, after the sacrificial layer 70 is released and removed through the through groove 25, the middle area of ​​the piezoelectric component 20 is suspended on the silicon structure layer 12. The middle area of ​​the piezoelectric component 20 forms a resonator.

[0195] After the sacrificial layer 70 is removed, there is a gap between the middle area of ​​the piezoelectric component 20 and the silicon structure layer 12, and the gap forms a resonant cavity 24. The size of the space occupied by the sacrificial layer 70 is the size of the resonant cavity 24.

[0196] The part of the piezoelectric component 20 used to surround the side wall of the resonant cavity 24 forms the anchor point of the piezoelectric resonant pressure sensor. One end of the anchor point is supported on the silicon structure layer 12 of the pressure sensitive component 10, and the other end of the anchor point is connected to the resonator. The anchor point serves as a bridge between the pressure sensitive component 10 and the resonator, and the resonator is suspended on the pressure sensitive component 10. The anchor point plays the role of connecting the pressure sensitive film and supporting the resonator.

[0197] When the pressure to be detected enters the pressure chamber 11 from the open end of the pressure chamber 11 and acts on the cavity wall of the pressure chamber 11 close to the silicon structure layer 12, the pressure sensitive film is deformed by the pressure to be detected and bends in the direction close to the piezoelectric component 20. The pressure sensitive film can transfer the deformation and stress to the anchor point, and further, the anchor point transfers the pressure and deformation to the resonator, causing the vibration frequency of the resonator to change. The external power supply receives and analyzes the change in the vibration frequency of the resonator to obtain data such as the size and direction of the pressure to be detected.

[0198] The side cavity wall of the resonant cavity 24 forms an anchor point, and there is no need to set up an additional support structure as an anchor point between the piezoelectric component 20 and the pressure sensitive component 10, which can simplify the structure of the piezoelectric resonant pressure sensor and reduce the size of the piezoelectric resonant pressure sensor.

[0199] Since the orthographic projection of the sacrificial layer 70 on the silicon structure layer 12 at least partially overlaps with the orthographic projection of the pressure cavity 11 on the silicon structure layer 12, after removing the sacrificial layer 70 to form the resonant cavity 24, the orthographic projection of the resonant cavity 24 on the silicon structure layer 12 at least partially overlaps with the orthographic projection of the pressure cavity 11 on the silicon structure layer 12, thereby ensuring that the pressure-sensitive film can be deformed to bend toward the piezoelectric component 20 when subjected to the pressure to be detected, that is, the resonant cavity 24 can provide a deformation space for the pressure-sensitive film.

[0200] Since the side cavity wall of the resonance cavity 24 forms an anchor point, when the orthographic projection of the resonance cavity 24 on the silicon structure layer 12 at least partially overlaps with the orthographic projection of the pressure cavity 11 on the silicon structure layer 12, it can ensure that the anchor point is in contact with the pressure sensitive film, thereby ensuring that the anchor point converts the stress on the pressure sensitive film into stress on the resonator, thereby achieving a change in the vibration frequency of the resonator.

[0201] In a possible implementation, step S40: forming the piezoelectric component 20 on the sacrificial layer 70 and the silicon structure layer 12 includes the following steps:

[0202] Step S401 : forming a first conductive layer 21 on the sacrificial layer 70 and the silicon structure layer 12 .

[0203] Specifically, a deposition process may be used to form the first conductive layer 21 on the sacrificial layer 70 and the silicon structure layer 12 .

[0204] It should be noted that a seed layer should be deposited before depositing the first conductive layer 21 to ensure the quality of the piezoelectric layer 22 .

[0205] Step S402 : forming a piezoelectric layer 22 on the first conductive layer 21 and the silicon structure layer 12 .

[0206] Specifically, the piezoelectric layer 22 may be formed on the first conductive layer 21 and the silicon structure layer 12 by using a deposition process.

[0207] Step S403 : forming a second conductive layer 23 on the piezoelectric layer 22 and the silicon structure layer 12 to obtain a piezoelectric component 20 .

[0208] Specifically, the second conductive layer 23 may be formed on the piezoelectric layer 22 and the silicon structure layer 12 by using a deposition process.

[0209] It should be noted that the second conductive layer 23 may include a top electrode, such as Figure 6 The second conductive layer 23 may also include two top electrodes, such as Figure 1 , Figure 7 and Figure 8 As shown. Of course, the second conductive layer 23 may also include three, four or more top electrodes, which is not specifically limited here. When the second conductive layer 23 includes one top electrode, the one top electrode plays the role of a driving electrode and, at the same time, plays the role of a detection electrode.

[0210] Specifically, when the top electrode is electrically connected to the driving circuit, the resonator can be driven to vibrate, and the top electrode plays the role of a driving electrode. When the top electrode is electrically connected to the detection circuit, the vibration signal of the resonator can be output to obtain data of the pressure to be detected. At this time, the top electrode plays the role of a detection electrode.

[0211] In specific operation, the one top electrode can be set to be alternately electrically connected to the driving circuit and the detection circuit. For example, the one top electrode can be set to be electrically connected to the driving circuit within the first 0.5 second, to be electrically connected to the detection circuit within the second 0.5 second, to be electrically connected to the driving circuit within the third 0.5 second, and to be electrically connected to the detection circuit within the fourth 0.5 second, and the electrical connections between the one top electrode and the driving circuit and the detection circuit are set at this interval.

[0212] When the second conductive layer 23 includes two top electrodes, one top electrode may be provided as a driving electrode electrically connected to a driving circuit, and the other top electrode may be provided as a detecting electrode electrically connected to a detecting circuit.

[0213] When the second conductive layer 23 includes more top electrodes, a portion of the top electrodes may be set as driving electrodes electrically connected to the driving circuit, and another portion of the top electrodes may be set as detecting electrodes electrically connected to the detecting circuit.

[0214] The first conductive layer 21 and the second conductive layer 23 are both made of conductive metal, for example, Mo, Au, Pt, Al, etc., preferably Mo.

[0215] In some embodiments, after step S40: forming a piezoelectric component 20 on the sacrificial layer 70 and the silicon structure layer 12, and before step S50: performing a first patterning process on the piezoelectric component 20 to form a through groove 25 in the middle area of ​​the piezoelectric component 20, the method for preparing a piezoelectric resonant pressure sensor provided in an embodiment of the present application also includes step S50: forming a first bonding ring 15 on the silicon structure layer 12; the first bonding ring 15 corresponds to the four edges of the silicon structure layer 12.

[0216] This facilitates the bonding connection between the pressure sensitive component 10 and the subsequent cover 30 .

[0217] After the sacrificial layer 70 is released through the through groove 25, the preparation method provided in the embodiment of the present application further includes the following steps:

[0218] Step S80 , providing a second wafer 30 ′, on which a second bonding ring 32 is disposed, and the first bonding ring 15 matches the second bonding ring 32 .

[0219] Step S90 , performing a second patterning process on the surface of the second wafer 30 ′ provided with the second bonding ring 32 to obtain a cover space 31 and obtain a cover 30 .

[0220] Step S100 , bonding the first bonding ring 15 and the second bonding ring 32 , and the piezoelectric component 20 is located in the covering space 31 .

[0221] It should be noted that, in the embodiment provided in the present application, the piezoelectric layer 22 may be electrically connected to an external circuit through a through silicon via 60 .

[0222] In a specific implementation, the through silicon vias 60 can be disposed on the pressure sensitive component 10, such as Figure 3 The through silicon vias 60 may also be disposed on the cover 30, as shown in FIG. Figure 4 and Figure 5 Of course, in a specific implementation, part of the through silicon vias 60 can be disposed on the pressure sensitive component 10 , and another part of the through silicon vias 60 can be disposed on the cover 30 .

[0223] The number of through silicon vias 60 may be two, three, four or more. The number of through silicon vias 60 for connecting to the second conductive layer 23 may be the same as the number of top electrodes included in the second conductive layer 23, and the number of through silicon vias 60 for connecting to the first conductive layer 21 may be one, two or more, which is not specifically limited here.

[0224] For ease of understanding, the method for preparing the piezoelectric resonant pressure sensor provided in the embodiment of the present application is described below in a possible implementation manner in conjunction with the accompanying drawings. Of course, this is not a specific limitation here.

[0225] In one example, the piezoelectric resonant pressure sensor is prepared by the method for preparing the piezoelectric resonant pressure sensor provided in the embodiment of the present application. Figure 3 The piezoelectric resonant pressure sensor shown.

[0226] The specific steps are as follows:

[0227] Step S11, providing a first wafer 10'. Fig.14 As shown, the first wafer 10' is provided with at least two through silicon vias 60. The first wafer 10' further comprises a silicon structure layer 12, a buried oxide layer 13 and a substrate layer 14 stacked in sequence, and the through silicon vias 60 penetrate the first wafer 10' from the substrate layer 14 to the silicon structure layer 12.

[0228] Step S12, as Fig.15 As shown, a front lead electrode 40 ′ is deposited on a side of the substrate layer 14 away from the silicon structure layer 12 .

[0229] The material of the front lead electrode 40 ′ is a conductive metal. For example, the material of the lead electrode 40 may be Al, Au, Pt, etc., preferably Al or Au.

[0230] Step S13, patterning the front lead electrode 40' to form a lead electrode 40 electrically connected to the through silicon via 60, such as Fig.16 The lead electrode 40 cooperates with the through silicon via 60 so as to facilitate electrical connection between the through silicon via 60 and an external circuit.

[0231] Step S14, forming a pressure chamber 11 for receiving the pressure to be detected on the first wafer 10', the pressure chamber 11 penetrates the substrate layer 14 of the first wafer 10', and obtaining a pressure sensitive component 10, such as Fig.17 shown.

[0232] Step S15, depositing a front sacrificial layer 70' on the silicon structure layer 12 of the first wafer 10', such as Fig.18 shown.

[0233] Step S16, etching the front sacrificial layer 70' to form a sacrificial layer 70, such as Fig.19 shown.

[0234] Step S17, depositing the first conductive layer 21' on the sacrificial layer 70 and the silicon structure layer 12, such as Fig. 20 shown.

[0235] Step S18, etching the front first conductive layer 21' to form the first conductive layer 21, such as Fig.21 The first conductive layer 21 is electrically connected to at least one through silicon via 60 .

[0236] Step S19, depositing a front piezoelectric layer 22' on the first conductive layer 21 and the silicon structure layer 12, such as Fig. 22 shown.

[0237] Step S110, etching the front piezoelectric layer 22' to form the piezoelectric layer 22, such as Fig.23 shown.

[0238] Step S111, depositing a front second conductive layer 23' on the piezoelectric layer 22 and the silicon structure layer 12, such as Fig.24 shown.

[0239] Step S112, patterning the second conductive layer 23' to obtain the second conductive layer 23, such as Fig.25 The second conductive layer 23 is electrically connected to at least one through silicon via 60 , and at the same time, the first conductive layer 21 is prevented from being electrically connected to the second conductive layer 23 .

[0240] Step S113, depositing a third conductive layer 15' on the second conductive layer 23 and the silicon structure layer 12, such as Fig.26 The material of the front third conductive layer 15' depends on the bonding method of the final cover 30 and the pressure sensitive component 10, preferably Al-Ge bonding, and the material of the front third conductive layer 15' can be Al.

[0241] Step S114, etching the front third conductive layer 15' to obtain the first bonding ring 15, such as Fig. 27 The first bonding ring 15 covers the edges of the silicon structure layer 12 .

[0242] Step S115, etching the piezoelectric component 20 to form a through groove 25. The through groove 25 passes through the middle area of ​​the piezoelectric component 20, and one end of the through groove 25 extends to the sacrificial layer 70. Fig.28 shown.

[0243] Step S116, releasing the sacrificial layer 70, forming the resonant cavity 24, as shown in FIG. Fig.29 shown.

[0244] Step S117, providing a second wafer 30', such as Fig.30 shown.

[0245] Step S118, depositing a front fourth conductive layer 32' on one surface of the second wafer 30', such as Fig.31 shown.

[0246] Step S119, patterning the fourth conductive layer 32' to obtain the second bonding ring 32, such as Fig.32 The second bonding ring 32 matches the first bonding ring 15 .

[0247] Step S120, etching the side of the second wafer 30' provided with the second bonding ring 32 to obtain a covering space 31, such as Fig.33 Specifically, dry etching or wet etching can be used.

[0248] Step S121, preparing the getter 50, such as Fig.34 The getter 50 is disposed in the cover space 31 , and the getter 50 may be a thin film getter or other structure capable of maintaining a vacuum inside the piezoelectric resonant pressure sensor.

[0249] Specifically, the suction member 50 is used to absorb the gas molecules released from the piezoelectric component 20, the pressure sensitive component 10 and other devices after the first wafer 10' and the second wafer 30' are bonded and connected, so that the inside of the piezoelectric resonant pressure sensor is maintained in a vacuum state to ensure the vacuum degree of the vacuum chamber, ensure the measurement accuracy and sensitivity of the piezoelectric resonant pressure sensor, and extend the service life of the piezoelectric resonant pressure sensor.

[0250] Step S122, aligning and bonding the first bonding ring 15 and the second bonding ring 32 in a vacuum environment, so that the first wafer 10' and the second wafer 30' are bonded and connected, and the result is as follows: Figure 3 The piezoelectric resonant pressure sensor shown.

[0251] In another example, the piezoelectric resonant pressure sensor is prepared by the method for preparing the piezoelectric resonant pressure sensor provided in the embodiment of the present application. Figure 5 The piezoelectric resonant pressure sensor shown.

[0252] The specific steps are as follows:

[0253] Step S21, providing a first wafer 10', such as Fig.35 The first wafer 10' comprises a silicon structure layer 12, a buried oxide layer 13 and a substrate layer 14 which are stacked in sequence.

[0254] Step S22, forming a pressure chamber 11 for receiving the pressure to be detected on the first wafer 10', the pressure chamber 11 penetrates the substrate layer 14 of the first wafer 10', and obtaining a pressure sensitive component 10, such as Fig.36 shown.

[0255] Step S23, depositing a front sacrificial layer 70' on the silicon structure layer 12 of the first wafer 10', such as Fig.37 shown.

[0256] Step S24, etching the front sacrificial layer 70' to form a sacrificial layer 70, such as Fig.38 shown.

[0257] Step S25, depositing the first conductive layer 21' on the sacrificial layer 70 and the silicon structure layer 12, such as Fig.39 shown.

[0258] Step S26, etching the front first conductive layer 21' to form the first conductive layer 21, such as Fig.40 shown.

[0259] Step S27, depositing a front piezoelectric layer 22' on the first conductive layer 21 and the silicon structure layer 12, such as Fig.41 shown.

[0260] Step S28, etching the front piezoelectric layer 22' to form a piezoelectric layer 22, such as Fig.42 As shown, the piezoelectric layer 22 is provided with a connecting hole 211 ′.

[0261] Step S29, depositing a front second conductive layer 23' on the piezoelectric layer 22 and the silicon structure layer 12, such as Fig.43 At the same time, when the second conductive layer 23 ′ is deposited on the piezoelectric layer 22 and the silicon structure layer 12 by using a deposition process, part of the metal fills the connecting hole 211 ′ to form a connecting lead 211 , which is electrically connected to the first conductive layer 21 .

[0262] Step S210, patterning the second conductive layer 23' to obtain the second conductive layer 23 as shown in FIG. Fig.44 At the same time, during the process of patterning the front second conductive layer 23 ′, a connection seat is formed at a position corresponding to the connecting lead 211 , and the connection seat is electrically connected to the connecting lead 211 .

[0263] Step S211, depositing a third conductive layer 15' on the second conductive layer 23 and the silicon structure layer 12, such as Fig.45 shown.

[0264] Step S212, etching the front third conductive layer 15' to obtain the first bonding ring 15, such as Fig.46 The first bonding ring 15 covers the edges of the silicon structure layer 12. At the same time, when etching the front third conductive layer 15', connecting leads 26 are formed at the positions corresponding to the connecting holes 211' and on the second conductive layer 23.

[0265] Step S213, etching the piezoelectric component 20 to form a through groove 25. The through groove 25 passes through the middle area of ​​the piezoelectric component 20, and one end of the through groove 25 extends to the sacrificial layer 70. Fig.47 shown.

[0266] Step S214, releasing the sacrificial layer 70, forming the resonant cavity 24, as shown in FIG. Fig.48 shown.

[0267] Step S215, providing a second wafer 30', such as Fig.49 As shown, at least two through silicon vias 60 are disposed on the second wafer 30 ′.

[0268] Step S216, depositing the front lead electrode 40' on one surface of the second wafer 30', such as Fig.50 As shown, the front lead electrode 40 ′ is electrically connected to the through silicon via 60 .

[0269] Step S217, patterning the front lead electrode 40' to form a lead electrode 40 electrically connected to the through silicon via 60, such as Fig.51 The lead electrode 40 cooperates with the through silicon via 60 so as to facilitate electrical connection between the through silicon via 60 and an external circuit.

[0270] Step S218, depositing a front fourth conductive layer 32' on one surface of the second wafer 30', such as Fig.52 As shown, the second wafer 30 ′ has a surface for arranging the lead electrode 40 and a surface for arranging the front fourth conductive layer 32 ′ opposite to each other. The front fourth conductive layer 32 ′ is electrically connected to the through silicon via 60 .

[0271] Step S219, patterning the fourth conductive layer 32', such as Fig.53 As shown, a second bonding ring 32 is obtained. The second bonding ring 32 matches the first bonding ring 15.

[0272] Step S220, etching the side of the second wafer 30' provided with the second bonding ring 32 to obtain a covering space 31, such as Fig.54 Specifically, dry etching or wet etching can be used.

[0273] Step S221, prepare the getter 50, such as Fig.55The air suction member 50 is disposed in the cover space 31 .

[0274] Step S222, align and bond the first bonding ring 15 and the second bonding ring 32 in a vacuum environment, so that the first wafer 10' and the second wafer 30' are bonded and connected, and ... Figure 5 At this time, the first conductive layer 21 is electrically connected to the through silicon via 60 through the connecting lead 211 , the connecting lead 26 and the connecting seat, and the second conductive layer 23 is electrically connected to the through silicon via 60 through the connecting lead 26 .

[0275] Finally, it should be noted that the above embodiments are only specific implementation methods of the present application, but the protection scope of the present application is not limited thereto, and any changes or substitutions within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A piezoelectric resonant pressure sensor, characterized in that: include: A pressure sensitive component having a first surface and a second surface arranged opposite to each other; the pressure sensitive component having a pressure cavity penetrating the second surface, and the pressure to be detected acts on a cavity wall of the pressure cavity close to the first surface; A piezoelectric component is electrically connected to an external circuit through a through silicon via; the four sides of the piezoelectric component are supported on the first surface, and the middle area of ​​the piezoelectric component is suspended on the first surface, so as to form a resonant cavity between the middle area and the first surface; An orthographic projection of the resonance cavity on the second surface at least partially overlaps with an orthographic projection of the pressure cavity on the second surface.

2. The piezoelectric resonant pressure sensor according to claim 1, characterized in that: The piezoelectric component comprises a first conductive layer, a piezoelectric layer, and a second conductive layer, wherein the first conductive layer and the second conductive layer are electrically connected to the external circuit through the through silicon via; the first conductive layer and the second conductive layer have different polarities; At least corresponding to the middle area, the first conductive layer, the piezoelectric layer and the second conductive layer are stacked in sequence from the pressure sensitive component to the piezoelectric component; and, corresponding to the middle area, the first conductive layer, the piezoelectric layer and the second conductive layer protrude in the direction away from the pressure sensitive component to form the resonant cavity.

3. The piezoelectric resonant pressure sensor according to claim 2, characterized in that: At least two through silicon vias are provided on the pressure sensitive component, the first conductive layer is electrically connected to the external circuit through at least one of the through silicon vias, and the second conductive layer is electrically connected to the external circuit through at least another through silicon via.

4. The piezoelectric resonant pressure sensor according to claim 2, characterized in that: The piezoelectric resonant pressure sensor further comprises a cover disposed on the first surface; a cover space is disposed on a side of the cover facing the first surface, and the piezoelectric component is located in the cover space.

5. The piezoelectric resonant pressure sensor according to claim 4, characterized in that: At least two through silicon vias are provided on the cover, the first conductive layer is electrically connected to the external circuit through at least one of the through silicon vias, and the second conductive layer is electrically connected to the external circuit through at least another through silicon via.

6. The piezoelectric resonant pressure sensor according to claim 4, characterized in that: The cover is vacuum connected to the first surface; The piezoelectric resonant pressure sensor further comprises an air suction member disposed in the cover space, and the air suction member is used to absorb gas after the cover is vacuum-connected to the pressure sensitive component.

7. The piezoelectric resonant pressure sensor according to claim 2, characterized in that: A through groove is provided on the piezoelectric component, and the through groove passes through the middle area and is connected with the resonant cavity.

8. A method for preparing a piezoelectric resonant pressure sensor, characterized in that: include: providing a first wafer; forming a pressure chamber on the first wafer for receiving a pressure to be detected; The pressure chamber penetrates the substrate layer of the first wafer to obtain a pressure sensitive component; forming a sacrificial layer on the silicon structure layer of the first wafer; The orthographic projection of the sacrificial layer on the silicon structure layer at least partially overlaps with the orthographic projection of the pressure chamber on the silicon structure layer; A piezoelectric component is formed on the sacrificial layer and the silicon structure layer, and the piezoelectric component is used to be electrically connected to an external circuit; the sacrificial layer corresponds to the middle area of ​​the piezoelectric component; the piezoelectric component includes a first conductive layer, a piezoelectric layer, and a second conductive layer; at least corresponding to the middle area, the first conductive layer, the piezoelectric layer, and the second conductive layer are stacked in sequence from the pressure sensitive component to the piezoelectric component; Performing a first patterning process on the piezoelectric component to form a through groove in a middle region of the piezoelectric component, wherein the through groove penetrates the middle region and one end of the through groove extends to the sacrificial layer; The sacrificial layer is released through the through groove.

9. The method for preparing a piezoelectric resonant pressure sensor according to claim 8, characterized in that: The forming of a piezoelectric component on the sacrificial layer and the silicon structure layer comprises: forming the first conductive layer on the sacrificial layer and the silicon structure layer; forming the piezoelectric layer on the first conductive layer and the silicon structure layer; The second conductive layer is formed on the piezoelectric layer and the silicon structure layer to obtain the piezoelectric component.

10. The method for preparing a piezoelectric resonant pressure sensor according to claim 9, characterized in that: After forming the piezoelectric component on the sacrificial layer and the silicon structure layer, and before performing a first patterning process on the piezoelectric component to form a through groove in the middle area of ​​the piezoelectric component, the method for preparing the piezoelectric resonant pressure sensor further includes: forming a first bonding ring on the silicon structure layer; the first bonding ring corresponds to the four edges of the silicon structure layer; After the sacrificial layer is released through the through groove, the preparation method further includes: Providing a second wafer, on which a second bonding ring is disposed, and the first bonding ring matches the second bonding ring; Performing a second patterning process on a side of the second wafer provided with the second bonding ring to obtain a cover space and obtain a cover; The first bonding ring and the second bonding ring are bonded, and the piezoelectric component is located in the covering space.

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