Piezoelectric resonant sensor and preparation method thereof

Abstract

The invention provides a piezoelectric resonant sensor and a preparation method thereof, and relates to the technical field of sensors and sensor manufacturing. The piezoelectric resonant sensor comprises a substrate and a piezoelectric component. Wherein the substrate is provided with a first side and a second side which are opposite to each other, and an input cavity is formed in the second side; the piezoelectric assembly is connected to the first side of the substrate, one side, facing the substrate, of part of the piezoelectric assembly protrudes in the direction away from the substrate and is matched with the substrate to form a resonant cavity, and the resonant cavity is at least partially opposite to the input cavity. A pressure sensitive film is formed on the part, opposite to the input cavity, of the substrate, and the input cavity is used for receiving to-be-detected pressure and transmitting the to-be-detected pressure to the pressure sensitive film, so that the pressure sensitive film drives the piezoelectric assembly to deform through the cavity wall of the resonant cavity. Therefore, a resonant cavity is naturally formed between the piezoelectric component and the substrate, and an additional middle layer can be avoided, so that the size of the piezoelectric resonant sensor can be reduced, the cost is reduced, and large-scale production is facilitated.

Description

Technical Field

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

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

[0003] According to different working principles, pressure sensors can be divided into piezoelectric resonant sensors, piezoresistive sensors, capacitive sensors, piezoelectric sensors, etc. Among them, piezoelectric resonant sensors have the advantages of good stability and high accuracy, and are widely used in technical fields with high precision requirements and harsh environments, such as aerospace, petroleum, etc.

[0004] Based on the structure of existing piezoelectric resonant sensors, the piezoelectric resonant sensors are large in size and high in cost, which is not conducive to large-scale mass production. Summary of the invention

[0005] The present application provides a piezoelectric resonant sensor and a preparation method, which can reduce the size of the piezoelectric resonant sensor and reduce the cost, and can facilitate large-scale mass production.

[0006] In a first aspect, the present application provides a piezoelectric resonant sensor, comprising a substrate and a piezoelectric component. The substrate has a first side and a second side opposite to each other, and an input cavity is formed on the second side. The piezoelectric component is connected to the first side of the substrate, and a portion of the piezoelectric component protrudes toward one side of the substrate in a direction away from the substrate, and cooperates with the substrate to form a resonant cavity, and the resonant cavity is at least partially opposite to the input cavity.

[0007] A pressure sensitive film is formed on the substrate at a portion opposite to the input cavity. The input cavity is used to receive the pressure to be detected and transmit the pressure to be detected to the pressure sensitive film so that the pressure sensitive film drives the piezoelectric component to deform through the cavity wall of the resonant cavity.

[0008] The present application forms a resonant cavity between the piezoelectric component and the substrate through the special protruding setting of the piezoelectric component, avoids the need to set up an additional intermediate layer to connect the piezoelectric component and the substrate, and grooves are opened in the intermediate layer to form a resonant cavity design, thereby reducing the size of the piezoelectric resonant sensor, reducing costs, and facilitating large-scale production.

[0009] Optionally, the piezoelectric component includes a piezoelectric layer, a bottom electrode and a top electrode. The bottom electrode is connected to the first side, and the bottom electrode protrudes toward the side of the substrate in a direction away from the substrate, and cooperates with the substrate to form a resonant cavity. The piezoelectric layer is connected to the side of the bottom electrode away from the substrate, and the top electrode is connected to the side of the piezoelectric layer away from the bottom electrode. Both the bottom electrode and the top electrode are used to connect to an external circuit.

[0010] The piezoelectric layer is located between the bottom electrode and the top electrode, and can cooperate with the bottom electrode and the top electrode to realize pressure sensing. The bottom electrode is connected to the first side of the substrate, and can cooperate with the substrate to form a resonant cavity through the protrusion on the bottom electrode.

[0011] Optionally, the piezoelectric component includes a first lead electrode for connecting to an external circuit, one end of the first lead electrode is connected to the bottom electrode, and the middle of the first lead electrode passes through the piezoelectric layer so that the other end of the first lead electrode is located on the side of the piezoelectric layer away from the substrate.

[0012] Through the above arrangement, a first lead electrode penetrating the piezoelectric layer can be arranged on the bottom electrode, and the first lead electrode can also extend to the outside of the piezoelectric resonant sensor, so that the bottom electrode can be easily connected to the external circuit through the first lead electrode.

[0013] Optionally, the piezoelectric component further includes a driving electrode and a detecting electrode, both of which are connected to the top electrode and are located on a side of the top electrode away from the piezoelectric layer. Both the driving electrode and the detecting electrode are used to connect to an external circuit so that the driving electrode drives the piezoelectric layer to vibrate, and the detecting electrode detects the vibration of the piezoelectric layer.

[0014] Through the above arrangement, a driving electrode and a detection electrode can be led out from the top electrode to connect different external circuits or different positions of the same external circuit. In this way, the piezoelectric layer can be driven to vibrate by the driving electrode, and the vibration of the piezoelectric layer can be detected by the detection electrode.

[0015] Optionally, the piezoelectric resonant sensor further includes a cover, which is connected to a side of the piezoelectric component away from the substrate, and a projection of the cover covers the resonant cavity along a direction from the piezoelectric component to the substrate.

[0016] The setting of the cover can encapsulate the piezoelectric component, isolate the piezoelectric component and the external environment, reduce the impact of the external environment on the piezoelectric resonant sensor, and then improve the quality factor of the piezoelectric resonant sensor to ensure the working performance of the piezoelectric resonant sensor.

[0017] Optionally, a packaging cavity is provided on the side of the cover facing the substrate, the packaging cavity covers the piezoelectric component, and along the direction from the piezoelectric component to the substrate, the projection of the cavity wall of the packaging cavity covers the resonant cavity. The packaging cavity is a vacuum cavity, and an absorption layer is provided on the cavity wall of the packaging cavity, and the absorption layer is used to absorb the gas released after the cover is connected to the piezoelectric resonant sensor. Alternatively, there is pressure in the packaging cavity.

[0018] That is, the cover can vacuum-encapsulate the piezoelectric resonator so that the piezoelectric resonator can operate in a vacuum environment to form an absolute pressure sensor.

[0019] Alternatively, the piezoelectric resonator is packaged by the cover in a certain pressure environment instead of vacuum packaging, so as to form a relative pressure sensor.

[0020] Optionally, the substrate includes a first substrate layer, an oxide layer, and a second substrate layer that are stacked, the input cavity is arranged on a side of the second substrate layer away from the first substrate layer, and the input cavity penetrates the second substrate layer so that part of the oxide layer is exposed through the input cavity. A pressure-sensitive film is formed on a portion of the first substrate layer that is opposite to the input cavity, and the pressure-sensitive film cooperates with the piezoelectric component to form a resonant cavity.

[0021] In this way, when the input cavity is formed by processing, the processing depth of the input cavity can be guaranteed, and the possibility of damaging the pressure sensitive film during the processing of the input cavity is reduced.

[0022] Optionally, the piezoelectric resonant sensor further includes a protective layer, which is arranged on a side of the piezoelectric component facing away from the substrate.

[0023] In this way, the protective layer can isolate the piezoelectric component from the outside world, play the role of isolating air and moisture. Therefore, the piezoelectric resonant sensor can be kept in a dry state as much as possible, ensuring the working reliability of the piezoelectric resonant sensor.

[0024] In a second aspect, the present application provides a method for preparing a piezoelectric resonant sensor, and the preparation method is used to produce the piezoelectric resonant sensor in the first aspect.

[0025] The preparation method comprises: forming a sacrificial layer on a first side of a substrate; forming a piezoelectric component on the first side of the substrate and the sacrificial layer; setting a release hole on a side of the piezoelectric component away from the sacrificial layer, the release hole penetrating the piezoelectric component; releasing the sacrificial layer through the release hole to form a resonant cavity; and processing an input cavity on a second side of the substrate.

[0026] Optionally, the first side of the substrate includes a first region and a second region that are connected to each other.

[0027] Forming a sacrificial layer on the first side of the substrate includes: forming a supporting layer on the first side of the substrate, the supporting layer covering the first area and the second area, removing a portion of the supporting layer opposite to the first area, and forming a sacrificial layer on a portion of the supporting layer opposite to the second area.

[0028] The beneficial effects of the preparation method provided in the above-mentioned second aspect and each possible design of the above-mentioned second aspect can be referred to the beneficial effects brought about by the above-mentioned first aspect and each possible implementation method of the first aspect, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a cross-sectional schematic diagram of a piezoelectric resonant sensor according to an embodiment of the present application.

[0030] Figure 2 A top view of a piezoelectric resonant sensor without a cover according to an embodiment of the present application.

[0031] Figure 3 for Figure 2 Cross-sectional view at AA in the middle.

[0032] Figure 4 FIG. 1 is a schematic diagram of a piezoelectric resonator according to an embodiment of the present application.

[0033] Figure 5 This is a second schematic diagram of a piezoelectric resonator according to an embodiment of the present application.

[0034] Figure 6 This is the third schematic diagram of the piezoelectric resonator according to the embodiment of the present application.

[0035] Figure 7 This is a fourth schematic diagram of a piezoelectric resonator according to an embodiment of the present application.

[0036] Figure 8 This is a schematic diagram of inputting a pressure to be detected into a piezoelectric resonant sensor according to an embodiment of the present application.

[0037] Fig. 9 This is a schematic diagram of the pressure disassembly of a piezoelectric resonator in the pressure sensitive film transmission according to an embodiment of the present application.

[0038] Fig.10 A step diagram of a method for manufacturing a piezoelectric resonant sensor provided in an embodiment of the present application.

[0039] Fig.11 A schematic diagram of forming a sacrificial layer on a substrate provided in an embodiment of the present application.

[0040] Fig.12 A schematic diagram of forming a support layer on a substrate provided in an embodiment of the present application.

[0041] Fig.13 A schematic diagram of area division of a substrate provided in an embodiment of the present application.

[0042] Fig.14 A step diagram of a method for manufacturing a piezoelectric component provided in an embodiment of the present application.

[0043] Fig.15 A schematic diagram of forming a bottom electrode and a piezoelectric layer provided in an embodiment of the present application.

[0044] Fig.16 A schematic diagram of etching a first conductive hole on a piezoelectric layer provided in an embodiment of the present application.

[0045] Fig.17 A method based on the embodiment of the present application is provided Fig.16 Schematic diagram of processing electrode layers.

[0046] Fig.18 A method based on the embodiment of the present application is provided Fig.17 Schematic diagram of forming the top electrode.

[0047] Fig.19 A schematic diagram of forming a protective layer on a top electrode provided in an embodiment of the present application.

[0048] Fig. 20 A schematic diagram of forming a second conductive via and a third conductive via on a protective layer provided in an embodiment of the present application.

[0049] Fig.21 A method based on the embodiment of the present application is provided Fig. 20 Schematic diagram of forming a metal material layer.

[0050] Fig. 22 A schematic diagram of patterning a metal material layer provided in an embodiment of the present application.

[0051] Fig.23 A method based on the embodiment of the present application is provided Fig. 22 Schematic diagram of setting the release hole.

[0052] Fig.24 A schematic diagram of forming an input cavity on a substrate provided in an embodiment of the present application.

[0053] Fig.25 A schematic diagram of another piezoelectric resonant sensor provided in an embodiment of the present application.

[0054] Fig.26 A schematic diagram of another piezoelectric resonant sensor provided in an embodiment of the present application.

[0055] Fig. 27A schematic diagram of forming a metal layer on a packaging wafer provided in an embodiment of the present application.

[0056] Fig.28 A method based on the embodiment of the present application is provided Fig. 27 Schematic diagram of forming the second bonding ring.

[0057] Fig.29 A schematic diagram of forming a packaging cavity provided in an embodiment of the present application.

[0058] Fig.30 A method based on the embodiment of the present application is provided Fig.29 Schematic diagram of forming an absorption layer.

[0059] Description of reference numerals:

[0060] 100: piezoelectric resonant sensor; 10: substrate; 11: input cavity; 12: pressure sensitive film; 101: first substrate layer; 102: oxide layer; 103: second substrate layer; 104: first region; 105: second region; 20: piezoelectric component; 21: bottom electrode; 22: piezoelectric layer; 23: top electrode; 211: first lead electrode; 231: second lead electrode; 232: driving electrode; 233: detection electrode; 24: metal material Material layer; 241: first bonding ring; 25: piezoelectric resonator; 26: first conductive hole; 27: bottom electrode connection structure; 28: lead electrode body; 29: electrode layer; 30: resonant cavity; 31: sacrificial layer; 32: release hole; 33: support layer; 40: cover; 401: cover wafer; 402: metal layer; 41: packaging cavity; 42: absorption layer; 43: second bonding ring; 50: protective layer; 51: second conductive hole; 52: third conductive hole. DETAILED DESCRIPTION

[0061] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments 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 are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification, claims and drawings of this application are intended to cover non-exclusive inclusions.

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

[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 current limiting module of the present application. For example, in the description of the present application, the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, which are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on 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 "installation", "connection" and "connection" should be understood in a broad sense. For example, the "connection" or "connection" of a mechanical structure can refer to a physical connection. For example, the physical connection can be a fixed connection, such as a fixed connection through a barrier, such as a fixed connection through a screw, bolt or other barrier; the physical connection can also be a detachable connection, such as a mutual snap connection or snap connection; the physical connection can also be an integral connection, such as welding, bonding or integral molding to form a connection for connection. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances. The "connection" or "connection" of a circuit structure can refer to not only a physical connection, but also an electrical connection or a signal connection. For example, it can be a direct connection, that is, a physical connection, or it can be indirectly connected through at least one intermediate element, as long as the circuit is connected, and it can also be the internal connection of two elements; the signal connection can refer to a signal connection through a media medium, such as a radio wave, in addition to a signal connection through a circuit. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0069] It should be understood that the references to "one embodiment" or "an embodiment" throughout the specification mean that the specific features, structures, or characteristics associated with the embodiment are included in at least one embodiment of the present application. Therefore, the references to "in one embodiment" or "in an embodiment" appearing throughout the specification do not necessarily refer to the same embodiment. In addition, these specific features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0070] The resonant pressure sensor indirectly measures the pressure to be detected by measuring the change in the resonant frequency of the structure, and has the advantages of high accuracy and good stability. The measuring structure can be a detection circuit or other structure that can detect the pressure to be detected.

[0071] Existing resonant pressure sensors include electrostatic excitation-resistance detection type resonant pressure sensors, piezoelectric excitation-resistance detection type resonant pressure sensors, electromagnetic drive-electromagnetic detection type resonant pressure sensors, optical drive-optical detection type resonant pressure sensors and piezoelectric excitation-piezoelectric detection type resonant pressure sensors (piezoelectric resonant sensor 100), etc.

[0072] Compared with the electrostatic excitation-resistance detection type resonant pressure sensor, the piezoelectric excitation-resistance detection type resonant pressure sensor, and the electromagnetic drive-electromagnetic detection type resonant pressure sensor, the piezoelectric resonant sensor 100 uses the inverse piezoelectric effect of the piezoelectric material to excite the resonator, and uses the direct piezoelectric effect to detect the vibration of the resonator. This method has the advantages of simple principle and convenient detection, and can also form a closed-loop addition circuit to increase robustness.

[0073] The piezoelectric resonant sensor 100 includes a piezoelectric component 20. During the operation of the piezoelectric resonant sensor 100, the piezoelectric component 20 continuously vibrates with a first vibration frequency. When the piezoelectric resonant sensor receives a pressure to be detected, the piezoelectric component 20 can generate a working stress under the action of the pressure to be detected, so that the piezoelectric component 20 vibrates at a second vibration frequency.

[0074] In this way, the pressure to be detected can be calculated based on the first vibration frequency and the second vibration frequency.

[0075] Based on the above, the embodiment of the present application provides a piezoelectric resonant sensor 100 and a preparation method thereof. The piezoelectric resonant sensor 100 provided in the embodiment of the present application will be described in detail below in conjunction with the accompanying drawings.

[0076] Reference Figure 1 As shown, the present application provides a piezoelectric resonant sensor 100, including a substrate 10 and a piezoelectric component 20. The substrate 10 has a first side and a second side opposite to each other, and an input cavity 11 is formed on the second side of the substrate. The piezoelectric component 20 is connected to the first side of the substrate 10, and a portion of the piezoelectric component 20 protrudes toward one side of the substrate 10 in a direction away from the substrate 10, and cooperates with the substrate 10 to form a resonant cavity 30, and the resonant cavity 30 is at least partially opposite to the input cavity 11.

[0077] A pressure sensitive film 12 is formed on the substrate 10 at a portion opposite to the input cavity 11 . The input cavity 11 is used to receive the pressure to be detected and transmit the pressure to be detected to the pressure sensitive film 12 , so that the pressure sensitive film 12 drives the piezoelectric component 20 to deform through the cavity wall of the resonance cavity 30 .

[0078] In the present application, the piezoelectric resonant sensor 100 includes a substrate 10 and a piezoelectric component 20. The substrate 10 and the piezoelectric component 20 are stacked to support the piezoelectric component 20 and cooperate with the piezoelectric component 20 to detect the pressure to be detected.

[0079] The substrate 10 has a first side and a second side opposite to each other, the first side is connected to the piezoelectric component 20, and the second side is provided with an input cavity 11. In this way, the pressure to be detected can be input to the piezoelectric resonant sensor 100 through the input cavity 11, and after the bottom of the input cavity 11 receives the pressure to be detected, the pressure to be detected can be transmitted to the piezoelectric component 20 through the second side, so that the piezoelectric component 20 can be deformed.

[0080] When the piezoelectric component 20 is deformed based on the pressure to be detected, the vibration frequency of the piezoelectric component 20 will change, thereby facilitating the detection of the pressure to be detected.

[0081] In the embodiment of the present application, since part of the piezoelectric component 20 protrudes in a direction away from the substrate 10 , part of the piezoelectric component 20 is not in contact with the substrate 10 , so that there is a gap between the piezoelectric component 20 and the first side of the substrate 10 .

[0082] In this way, the gap between the piezoelectric component 20 and the substrate 10 can form a resonant cavity 30, so that the resonant cavity 30 can provide a vibration space for the vibration of the piezoelectric component 20, thereby reducing the possibility of damage to the piezoelectric component 20 caused by deformation of the piezoelectric component 20 due to vibration.

[0083] Specifically, when the input cavity 11 has a pressure to be detected, the pressure to be detected can act on the pressure sensitive film 12 opposite to the input cavity 11 , and the pressure sensitive film 12 is deformed by the pressure and generates working stress.

[0084] In the embodiment of the present application, the resonant cavity 30 is at least partially opposite to the input cavity 11 , and therefore, the pressure sensitive film 12 formed at the input cavity 11 is also partially opposite to the resonant cavity 30 .

[0085] Since the resonant cavity 30 is formed between the first side of the substrate 10 and the piezoelectric component 20 , and the pressure sensitive film 12 is formed by the substrate 10 and is opposite to the input cavity 11 on the second side, the pressure sensitive film 12 is essentially formed by a portion of the first side of the substrate 10 .

[0086] Based on this, at least a portion of the pressure sensitive film 12 may be opposite to the resonant cavity 30 and connected to the non-protruding portion of the piezoelectric component 20. The protruding portion and the non-protruding portion of the piezoelectric component 20 may have a transition portion, which extends along the stacking direction of the piezoelectric component 20 and the substrate 10 and may form the cavity wall of the resonant cavity 30.

[0087] Through the above arrangement, when the pressure sensitive film 12 is subjected to pressure, the pressure sensitive film 12 can transfer deformation to other parts of the piezoelectric component 20 through the cavity wall of the resonance cavity 30, so that stress related to the pressure to be detected is generated on the piezoelectric component 20.

[0088] Based on the piezoelectric resonant sensor 100 provided in the above example, the input cavity 11 can receive the pressure to be detected, so that the pressure sensitive film 12 is deformed, and then the pressure sensitive film 12 can drive the piezoelectric component 20 to deform through the cavity wall of the resonant cavity 30, so as to change the vibration frequency of the piezoelectric component 20. In this way, the pressure to be detected can be detected by detecting the vibration frequency of the piezoelectric component 20.

[0089] In summary, the present application can form a resonant cavity 30 between the piezoelectric component 20 and the substrate 10 through the special protruding setting of the piezoelectric component 20, which can avoid the need to set up an additional intermediate layer to connect the piezoelectric component 20 and the substrate 10, and to make grooves in the intermediate layer to form the resonant cavity 30, thereby reducing the size of the piezoelectric resonant sensor 100 and reducing costs, thereby facilitating large-scale production.

[0090] In order to make the purpose and principle of this application clearer, the following analysis is conducted in combination with relevant technologies.

[0091] In the related art, the piezoelectric resonant sensor 100 includes a piezoelectric component, an intermediate layer and a substrate stacked in sequence. The intermediate layer is connected to the substrate in a bonding manner, and a groove is provided on one side of the intermediate layer facing the substrate, and the groove can form a resonant cavity to provide space for the vibration of the piezoelectric component.

[0092] In addition, in the above-mentioned arrangement of the prior art, the intermediate layer can realize the connection between the piezoelectric component and the substrate, and can also serve as an anchor point to transmit and amplify the working stress.

[0093] In the present application, the resonant cavity 30 is formed by the cooperation of the piezoelectric component 20 and the substrate 10, which can reduce the need for an additional intermediate layer, reduce the size of the piezoelectric resonant sensor 100, and simplify the manufacturing process for easy production.

[0094] Furthermore, since the piezoelectric resonant sensor 100 provided in the present application does not have an intermediate layer, the piezoelectric component 20 is directly connected to the substrate 10. In this way, the portion of the piezoelectric component 20 close to the resonant cavity 30 can serve as the cavity wall of the resonant cavity 30 and naturally form an anchor point structure. Similar to the anchor point in the related art, it can also play a role in transmitting and amplifying the working stress.

[0095] Based on the above analysis, the present application can avoid the additional provision of an intermediate layer and an anchor point structure, can reduce the size of the piezoelectric resonant sensor 100, and facilitate the miniaturization of the piezoelectric resonant sensor 100.

[0096] It should be noted that the resonant cavity 30 and the input cavity 11 are at least partially opposite to each other, and the resonant cavity 30 and the input cavity 11 may be arranged in different ways. For example, the resonant cavity 30 and the input cavity 11 may be directly opposite to each other, that is, the geometric centers of the two are located on the same straight line. Of course, the resonant cavity 30 and the input cavity 11 may also be misaligned, that is, there is a distance between the geometric centers of the two.

[0097] Furthermore, the shape of the input cavity 11 may be the same as that of the resonant cavity 30 , for example, the input cavity 11 and the resonant cavity 30 may both be cylindrical chambers, or rectangular chambers, etc. Of course, the shape of the input cavity 11 may also be different from that of the resonant cavity 30 .

[0098] In addition, the input cavity 11 and the resonant cavity 30 may also have different sizes. For example, when the resonant cavity 30 is directly opposite to the input cavity 11, in the stacking direction of the piezoelectric component 20 and the substrate 10, the projection of the resonant cavity 30 falls within the projection range of the input cavity 11. In this case, the resonant cavity 30 is smaller than the input cavity 11. Alternatively, the resonant cavity 30 may also be larger.

[0099] Of course, the projection of the resonant cavity 30 may also coincide with the projection of the input cavity 11 and so on.

[0100] The specific shape, size and position relationship between the resonant cavity 30 and the input cavity 11 are not specifically limited in the present embodiment. As long as at least part of the resonant cavity 30 is opposite to the input cavity 11, the pressure to be detected received by the input cavity 11 can be transmitted to the piezoelectric component 20 through the cavity wall of the resonant cavity 30.

[0101] In addition, one input cavity 11 may be provided, or multiple input cavities 11 may be provided at intervals. Only one resonant cavity 30 may be provided, or multiple resonant cavities 30 may be provided, and this application example does not limit this.

[0102] In some embodiments, Figure 1 As shown, the piezoelectric component 20 may include a piezoelectric layer 22, a bottom electrode 21, and a top electrode 23. The bottom electrode 21 is connected to a first side of the substrate 10, and the bottom electrode 21 protrudes toward a side of the substrate 10 in a direction away from the substrate 10, and cooperates with the substrate 10 to form a resonant cavity 30. The piezoelectric layer 22 is connected to a side of the bottom electrode 21 away from the substrate 10, and the top electrode 23 is connected to a side of the piezoelectric layer 22 away from the bottom electrode 21. Both the bottom electrode 21 and the top electrode 23 are used to connect to an external circuit.

[0103] The piezoelectric component 20 is a multilayer structure consisting of a piezoelectric layer 22, a bottom electrode 21 and a top electrode 23. The piezoelectric layer 22 is located between the bottom electrode 21 and the top electrode 23, and can cooperate with the bottom electrode 21 and the top electrode 23 to detect the pressure to be detected based on the forward and reverse piezoelectric effects.

[0104] The piezoelectric layer 22 can be made of a piezoelectric film material, so that the piezoelectric layer 22 has a piezoelectric effect. In this way, when the piezoelectric layer 22 is under pressure, a potential difference can be generated on the opposite sides of the piezoelectric layer 22. Based on this, the positive piezoelectric effect and the inverse piezoelectric effect of the piezoelectric layer 22 can be used to detect parameters related to the pressure to be detected, such as the magnitude of the pressure to be detected and the direction of the pressure to be detected.

[0105] Specifically, the material of the piezoelectric layer 22 can be aluminum nitride (AlN), scandium-doped aluminum nitride (ScAlN), lead zirconate titanate (PZT), zinc oxide (ZnO), lithium niobate (LiNbO 3 ) etc. The specific material of the piezoelectric layer 22 is not specifically limited in the present embodiment.

[0106] In the present application, the bottom electrode 21 and the top electrode 23 can both be connected to an external circuit to cooperate with the piezoelectric effect of the piezoelectric layer 22 to detect the pressure to be detected.

[0107] The bottom electrode 21 may be directly electrically connected to an external circuit, or may be indirectly connected to an external circuit via a conductive member such as a wire. Similarly, the top electrode 23 may also be directly or indirectly connected to an external circuit.

[0108] In the embodiment of the present application, the piezoelectric layer 22 may have different configurations to cooperate with the substrate 10 to form the resonant cavity 30. The following two configurations are used as examples for illustration.

[0109] Method 1: Figure 2 and Figure 3 As shown, the bottom electrode 21 may be protruding as a whole. That is, the side of the bottom electrode 21 facing the substrate 10 and the side of the bottom electrode 21 facing away from the substrate 10 both protrude in a direction away from the substrate 10 .

[0110] At this time, the side of the bottom electrode 21 facing the substrate 10 can cooperate with the substrate 10 to form a resonant cavity 30 , and the side of the bottom electrode 21 facing away from the substrate 10 can provide a setting position for the piezoelectric layer 22 and the top electrode 23 .

[0111] Thus, when the piezoelectric layer 22 and the top electrode 23 are disposed on the bottom electrode 21 , they are disposed on the central protruding surface. The shapes of the piezoelectric layer 22 and the top electrode 23 may be similar to those of the bottom electrode 21 , both having a portion protruding in a direction away from the substrate 10 .

[0112] In this manner, in the stacking direction of the piezoelectric component 20 and the substrate 10 , the sizes of the bottom electrode 21 , the piezoelectric layer 22 , and the top electrode 23 at different locations are consistent.

[0113] In the second method, the side of the bottom electrode 21 facing the substrate 10 may be protruded, and the protruding part of the bottom electrode 21 cooperates with the substrate 10 to form a resonant cavity 30. The side of the bottom electrode 21 facing away from the substrate 10 may be parallel to the first side of the substrate 10 to form a plane.

[0114] In this way, the piezoelectric layer 22 and the top electrode 23 may be disposed on a plane, and there may be no protruding portions in the piezoelectric layer 22 and the top electrode 23 .

[0115] In this manner, in the stacking direction of the piezoelectric component 20 and the substrate 10, the size of the protruding portion provided in the bottom electrode 21 is smaller than that of other portions.

[0116] Of course, the piezoelectric layer 22 can have other settings, for example, the bottom electrode 21 can be protruding as a whole, the piezoelectric layer 22 has a protruding portion on the side facing the bottom electrode 21, the side of the piezoelectric layer 22 away from the bottom electrode 21 is parallel to the first side of the substrate 10, and so on.

[0117] The embodiment of the present application does not specifically limit the specific configuration of the piezoelectric component 20.

[0118] It should be noted that the external circuit can be a circuit for detecting current, voltage or charge. The embodiment of the present application does not limit the specific type of the external circuit, as long as the external circuit can detect the electrical signal output by the piezoelectric layer 22.

[0119] In addition, in the embodiment of the present application, the top electrode 23 in the present application can be located outside the piezoelectric resonant sensor 100, and when connecting to an external circuit, a structure for connecting to the external circuit can be directly led out from the top electrode 23. The bottom electrode 21 is located between the piezoelectric layer 22 and the substrate 10, and when connecting to an external circuit, it can be connected through the first lead electrode 211.

[0120] For example, Figure 3 As shown, one end of the first lead electrode 211 is connected to the bottom electrode 21 , and the middle of the first lead electrode 211 passes through the piezoelectric layer 22 , so that the other end of the first lead electrode 211 is located on the side of the piezoelectric layer 22 away from the substrate 10 .

[0121] That is, a first lead electrode 211 penetrating the piezoelectric layer 22 may be disposed on the bottom electrode 21 , and the first lead electrode 211 may also extend to the outside of the piezoelectric resonant sensor 100 , so that the bottom electrode 21 is connected to an external circuit through the first lead electrode 211 .

[0122] In order to reduce the possibility of the first lead electrode 211 and the top electrode 23 being connected and conducting and affecting the normal operation of the piezoelectric resonant sensor 100, the top electrode 23 can be patterned by etching or the like to remove part of the top electrode 23 so that the bottom electrode 21 has a part that is not opposite to the top electrode 23.

[0123] As such, the piezoelectric layer 22 is located outside the piezoelectric resonant sensor 100 at the position where the top electrode 23 is removed.

[0124] Through the above arrangement, the first lead electrode 211 can be connected to the portion of the bottom electrode 21 that is not opposite to the top electrode 23, and extend along the side away from the substrate 10, so that the first lead electrode 211 can pass through the piezoelectric layer 22 and be located on the piezoelectric layer 22. Therefore, the first lead electrode 211 can be located outside the piezoelectric resonant sensor 100, which facilitates the connection between the bottom electrode 21 and the external circuit.

[0125] Of course, when the bottom electrode 21 is connected to an external circuit through a conductive member such as a wire, the first lead electrode 211 may not be provided, and a lead hole may be provided on the piezoelectric layer 22. In this way, the wire may extend into the piezoelectric layer 22 through the lead hole and be connected to the bottom electrode 21 below the piezoelectric layer 22.

[0126] The top electrode 23 is a structure on the side of the piezoelectric component 20 facing away from the substrate 10 and is in an exposed state. An external circuit can be directly connected to the exposed portion of the top electrode 23 .

[0127] Alternatively, a second lead electrode 231 may be provided on the top electrode 23, and the second lead electrode 231 may serve as a pad. In this way, an external circuit may be connected to the top electrode 23 through the second lead electrode 231, thereby improving the reliability of the connection between the top electrode 23 and the external circuit.

[0128] In the embodiment of the present application, the bottom electrode 21 and the top electrode 23 can be used to connect different positions of the external circuit. For example, the bottom electrode 21 can be used for grounding to achieve the grounding of the piezoelectric resonant sensor 100. The top electrode 23 can be connected to a position in the external circuit for applying voltage and performing detection.

[0129] Of course, the top electrode 23 may be used for grounding, and the bottom electrode 21 may be connected to a position in an external circuit for applying voltage and performing detection.

[0130] In the following embodiments of the present application, the bottom electrode 21 is grounded, and the top electrode 23 is connected to a position in an external circuit for applying voltage and performing detection for specific description.

[0131] In the case where the top electrode 23 is connected to an external circuit through the second lead electrode 231, the second lead electrode 231 may include a driving electrode 232 and a detection electrode 233, and both the driving electrode 232 and the detection electrode 233 are connected to the top electrode 23. The driving electrode 232 and the detection electrode 233 are both used to connect to an external circuit, so that the driving electrode 232 drives the piezoelectric layer 22 to vibrate, and the detection electrode 233 detects the vibration of the piezoelectric layer 22.

[0132] That is, the top electrode 23 may be extended with a driving electrode 232 and a detecting electrode 233 to connect different external circuits or different positions of the same external circuit, such as Figure 2 and Figure 4 shown.

[0133] In this way, the piezoelectric layer 22 can be driven to vibrate by the driving electrode 232 , and the vibration of the piezoelectric layer 22 can be detected by the detecting electrode 233 .

[0134] In addition, when the top electrode 23 and the second lead electrode 231 (the driving electrode 232 and the detecting electrode 233 ) are connected, the connection may be performed through a conductive member such as a wire.

[0135] like Figure 2 and Figure 3 As shown, after the bottom electrode 21, the piezoelectric layer 22 and the top electrode 23 are arranged on the substrate 10, the bottom electrode 21, the piezoelectric layer 22 and the top electrode 23 can be etched, and the etched bottom electrode 21, the piezoelectric layer 22 and the top electrode 23 can form a piezoelectric resonator 25.

[0136] Of course, the method of forming the piezoelectric resonator 25 is not limited to the etching method, and other methods that can remove materials may also be used.

[0137] Based on this, different parts of the piezoelectric component 20 can be removed to form piezoelectric resonators 25 of different shapes. Figure 4 and Figure 5 , Figure 4 and Figure 5 The piezoelectric resonator 25 shown in FIG. 1 is a cross-shaped structure. Figure 6 , Figure 6 The piezoelectric resonator 25 shown is a straight-line structure. Figure 7 , Figure 7 The piezoelectric resonator 25 shown is a tuning fork structure. The specific shape of the piezoelectric resonator 25 is not specifically limited in the embodiment of the present application.

[0138] When the bottom electrode 21 is connected to the first lead electrode 211 through a wire, and the top electrode 23 is connected to the second lead electrode 231 through a wire, after the piezoelectric resonator 25 is formed, the portion of the piezoelectric component 20 that is not removed can also serve as a supporting bridge for the wires that lead the bottom electrode 21 to the first lead electrode 211 and the top electrode 23 to the second lead electrode 231.

[0139] It should be noted that the driving electrode 232 and the detecting electrode 233 may be connected or not connected. The following description is made by taking the cross-shaped piezoelectric resonator 25 as an example.

[0140] like Figure 5 As shown in the figure, the driving electrode 232 is connected to the detection electrode 233. At this time, in order to make the driving electrode 232 and the detection electrode 233 work normally, the operation of the driving electrode 232 and the detection electrode 233 can be controlled by time division.

[0141] For example, in a certain time period, the driving electrode 232 may be controlled to work in the first half of the time, and the detecting electrode 233 may be controlled to work in the second half of the time.

[0142] like Figure 4 As shown in the figure, the driving electrode 232 and the detecting electrode 233 are not connected. In this way, the mutual influence between the working of the driving electrode 232 and the detecting electrode 233 can be reduced.

[0143] Similarly, when the piezoelectric resonator 25 has other shapes, the driving electrode 232 and the detecting electrode 233 may be connected or not connected.

[0144] In some embodiments, Figure 3 As shown, the piezoelectric resonant sensor 100 further includes a protection layer 50 , which is disposed on a side of the piezoelectric component 20 facing away from the substrate 10 .

[0145] In the case where the piezoelectric component 20 includes a bottom electrode 21 , a piezoelectric layer 22 , and a top electrode 23 that are stacked, the protection layer 50 may be disposed on a side of the top electrode 23 that is away from the piezoelectric layer 22 .

[0146] In this way, the protective layer 50 can isolate the piezoelectric component 20 from the outside world, and play the role of isolating air and moisture. Therefore, the piezoelectric resonant sensor 100 can be kept in a dry state as much as possible, ensuring the working reliability of the piezoelectric resonant sensor 100.

[0147] Furthermore, the protection layer 50 may also play a role in temperature compensation during the operation of the piezoelectric resonant sensor 100 .

[0148] In the embodiment of the present application, the protective layer 50 can be made of a material that is both temperature-compensating and moisture-absorbing, such as silicon dioxide.

[0149] At this time, the bottom electrode 21 , the piezoelectric layer 22 , the top electrode 23 and the protective layer 50 may all be etched, and the etched bottom electrode 21 , the piezoelectric layer 22 , the top electrode 23 and the protective layer 50 may form a piezoelectric resonator 25 .

[0150] When the piezoelectric resonant sensor 100 further includes a protective layer 50, the protective layer is the outer side of the piezoelectric resonant sensor. At this time, the first lead electrode 211 and the second lead electrode 231 can extend to the side of the protective layer 50 away from the substrate 10 for wiring.

[0151] refer to Figure 3 The first lead electrode 211 may include a bottom electrode connection structure 27 and a lead electrode body 28 that are interconnected. The bottom electrode connection structure 27 is used to lead the bottom electrode 21 to the side of the piezoelectric layer 22 away from the substrate, and the lead electrode body 28 is used to lead the bottom electrode connection structure 27 to the side of the protective layer 50 away from the substrate 10.

[0152] Next, please refer to Figure 8 and Fig. 9 , the principle of the piezoelectric resonant sensor 100 is further introduced.

[0153] The piezoelectric resonator 25 itself has a certain resonant frequency. When the driving electrode 232 applies a voltage to the piezoelectric layer 22, the piezoelectric layer 22 can generate stress based on the inverse piezoelectric effect. When an alternating voltage with the same resonant frequency as the piezoelectric resonator 25 is applied to the driving electrode 232, the piezoelectric resonator 25 will resonate, and the resonant frequency (i.e., the aforementioned first vibration frequency) is:

[0154]

[0155] In the formula, f r is the resonant frequency, μ n are the constants set when solving the Bessel function, t is the thickness, r is the radius, E is the Young's modulus, ρ is the density, and δ is the Poisson's ratio.

[0156] When the input cavity 11 receives the pressure to be detected, the pressure sensitive film 12 will be deformed and generate working stress under the action of the pressure to be detected. The anchor structure can transfer the deformation and working stress of the pressure sensitive film 12 to the piezoelectric resonator 25, specifically to the piezoelectric layer 22. In this process, the anchor structure can amplify the working stress by lever principle and improve the measurement range of the piezoelectric resonant sensor 100.

[0157] During the working stress transmission process, the anchor point structure can also change the action direction of the pressure to be detected, thereby reducing the possibility of damage to the pressure sensitive film 12 .

[0158] During the operation of the piezoelectric resonant sensor 100 , the driving electrode 232 can drive the piezoelectric layer 22 to vibrate, and the detecting electrode 233 can generate an electrical signal for detecting the resonant frequency of the piezoelectric resonator 25 based on the positive piezoelectric effect of the piezoelectric film material.

[0159] Assuming that the working stress generated by the pressure to be detected on the piezoelectric resonator 25 is σ, the resonant frequency of the piezoelectric resonator 25 (i.e., the aforementioned second vibration frequency) is:

[0160]

[0161] From the above formula, it can be seen that the pressure value can be determined when the frequency change of the piezoelectric resonator is detected.

[0162] Compared with the resistance detection type piezoelectric sensor which needs to set up a Wheatstone bridge and the capacitance detection type pressure sensor which needs to set up a capacitance bridge, the piezoelectric resonant sensor 100 provided in the embodiment of the present application does not need to set up an additional detection circuit, has a simpler structure, and has a lower manufacturing cost.

[0163] In order to make the principle of the piezoelectric resonant sensor 100 proposed in the present application clearer, the force exerted by the anchor structure on the piezoelectric resonator 25 when the pressure to be detected is input into the input cavity 11 is analyzed as follows.

[0164] refer to Fig. 9 , Fig. 9 When the pressure to be detected is input to the piezoelectric resonant sensor 100, the force acting on the piezoelectric resonator 25 is disassembled and analyzed. As shown in the figure, the force acting on the piezoelectric resonator 25 is mainly divided into two aspects.

[0165] The first is the force on the piezoelectric resonator 25 when the pressure sensitive film 12 moves upward and drives the anchor structure to lift the piezoelectric resonator 25. The second is the force on the piezoelectric resonator 25 when the anchor structure tangentially deforms and squeezes the piezoelectric resonator 25.

[0166] The above two forces act together on the piezoelectric resonator 25, which can cause the resonant frequency of the piezoelectric resonator 25 to change, thereby realizing pressure sensing.

[0167] In some embodiments, Figure 1 As shown, the piezoelectric resonant sensor 100 may further include a cover 40 , which is connected to a side of the piezoelectric component 20 away from the substrate 10 , and a projection of the cover 40 covers the resonant cavity 30 along a direction from the piezoelectric layer 22 to the substrate 10 .

[0168] The setting of the cover 40 can encapsulate the piezoelectric component 20, isolate the piezoelectric component 20 and the external environment, reduce the impact of the external environment on the piezoelectric resonant sensor 100, and further improve the quality factor of the piezoelectric resonant sensor 100, thereby ensuring the working performance of the piezoelectric resonant sensor 100.

[0169] The cover 40 may be made of a silicon wafer, a glass wafer, an inorganic semiconductor material or other amorphous inorganic non-metallic materials.

[0170] It should be noted that, since the projection of the cover 40 covers the resonant cavity 30 , the provision of the cover 40 can also isolate the piezoelectric component 20 from the external environment, thereby reducing the influence of the external environment on the operation of the piezoelectric component 20 .

[0171] When the piezoelectric resonant sensor 100 further includes a cover 40, the side of the piezoelectric layer 22 facing away from the substrate 10 may not be provided with the protective layer 50. Of course, the cover 40 and the protective layer 50 may also be provided at the same time, which is not specifically limited in the present application.

[0172] That is, in the piezoelectric resonant sensor 100 proposed in the present application, only the cover 40 may be provided, only the protective layer 50 may be provided, or both the cover 40 and the protective layer 50 may be provided. Of course, the cover 40 and the protective layer 50 may not be provided, and the present application example does not make any specific limitation on this.

[0173] In some embodiments, Figure 1 As shown, a packaging cavity 41 may be provided on the side of the cover 40 facing the substrate 10 , and the packaging cavity 41 covers part of the piezoelectric component 20 , and the projection of the cavity wall of the packaging cavity 41 covers the resonance cavity 30 along the direction from the piezoelectric component 20 to the substrate 10 .

[0174] The packaging cavity 41 can provide space for the vibration of the piezoelectric component 20 to reduce the possibility that the piezoelectric component 20 may be damaged due to the vibration of the piezoelectric component 20 and the contact with the cover 40 thereon.

[0175] In the embodiment of the present application, the packaging cavity 41 may be a vacuum cavity, and an absorption layer 42 is provided on the cavity wall of the packaging cavity 41 , and the absorption layer 42 is used to absorb the gas released after the cover 40 is connected to the piezoelectric resonant sensor 100 .

[0176] In this way, the cover 40 can vacuum-encapsulate the piezoelectric resonator 25, so that the piezoelectric resonator 25 can work in a vacuum environment. At this time, the piezoelectric resonant sensor 100 is an absolute pressure sensor.

[0177] Alternatively, there is pressure in the packaging cavity 41 .

[0178] That is, the packaging of the piezoelectric resonator 25 by the cover 40 may not be vacuum packaging, but packaging under a certain pressure environment. In this way, there is a certain pressure in the packaging cavity 41, and the piezoelectric resonant sensor 100 is a relative pressure sensor.

[0179] It can be understood that the piezoelectric resonant sensor 100 in the form of a relative pressure sensor can also detect the pressure to be detected.

[0180] In some embodiments, the substrate 10 may include a first substrate layer 101, an oxide layer 102, and a second substrate layer 103 that are stacked, the input cavity 11 is disposed on a side of the second substrate layer 103 that is away from the first substrate layer 101, and the input cavity 11 penetrates the second substrate layer 103 so that a portion of the oxide layer 102 is exposed through the input cavity 11. A pressure-sensitive film 12 is formed on a portion of the first substrate layer 101 that is opposite to the input cavity 11, and the pressure-sensitive film 12 cooperates with the piezoelectric component 20 to form a resonant cavity 30.

[0181] Through the above configuration, the substrate 10 is also a multi-layer structure, and the oxide layer 102 is located between the first substrate layer 101 and the second substrate layer 103 , so that the input cavity 11 and the pressure sensitive film 12 are located on both sides of the oxide layer 102 .

[0182] In this way, when the input cavity 11 is processed and formed, the processing depth of the input cavity 11 can be guaranteed, and the possibility of damaging the pressure sensitive film 12 when processing the input cavity 11 is reduced.

[0183] Specifically, since the input cavity 11 penetrates the second substrate layer 103 and partially exposes the oxide layer 102, when processing the input cavity 11, it can be judged whether the input cavity 11 is processed in place by whether the oxide layer 102 is exposed. If the oxide layer 102 is exposed, it can be considered that the input cavity 11 is processed in place, and the processing of the input cavity 11 can be stopped.

[0184] In addition, the anchor structure, as an intermediate structure between the pressure sensitive film 12 and the piezoelectric resonator 25 , can support the pressure sensitive film 12 when the pressure sensitive film 12 is deformed.

[0185] In this way, the present application can sense the pressure to be detected through the pressure sensitive film 12 , and then transfer and convert it into stress on the piezoelectric resonator 25 through the anchor structure.

[0186] Through the above arrangement, the pressure can be measured without directly measuring the deformation of the pressure sensitive film 12, so that the thickness of the pressure sensitive film 12 can be designed to be larger. Therefore, the pressure sensitive film 12 can withstand a larger pressure, thereby improving the pressure bearing capacity of the piezoelectric resonant sensor 100, expanding the pressure detection range, and ensuring the linearity of the piezoelectric resonant sensor 100 within the pressure measurement range.

[0187] The thickness of the pressure sensitive film 12 is the distance between two opposite ends of the pressure sensitive film 12 in the stacking direction of the piezoelectric component 20 and the substrate 10 .

[0188] In the piezoelectric resonant sensor 100 proposed in the present application, the piezoelectric component 20 is specially protruded to form a resonant cavity 30 between the piezoelectric component 20 and the substrate 10. In this way, it is possible to avoid the need to provide an additional intermediate layer to connect the piezoelectric component 20 and the substrate 10, and to make grooves in the intermediate layer to form the resonant cavity 30, thereby reducing the size of the piezoelectric resonant sensor 100 and reducing costs, thereby facilitating large-scale production.

[0189] In addition, if Fig.10 As shown, the embodiment of the present application also proposes a method for preparing a piezoelectric resonant sensor 100 , and the preparation method is used to produce the piezoelectric resonant sensor 100 in any of the above embodiments.

[0190] The preparation method may specifically include the following steps.

[0191] Step 1001, forming a sacrificial layer on the first side of the substrate. Fig.11 , Fig.11 A schematic diagram showing forming a sacrificial layer 31 on a substrate 10 is shown.

[0192] The substrate 10 may be an SOI wafer. SOI stands for Silicon On Insulator, which is widely used in power devices, pressure sensors and integrated circuit manufacturing.

[0193] The SOI wafer is a sandwich-like structure, including three layers: a device layer at the top, a buried oxide layer (ie, the oxide layer 102 mentioned above) in the middle, and a substrate layer (bulk silicon) at the bottom.

[0194] In this example of the present application, the device layer may be the first side of the substrate 10 , that is, the first substrate layer 101 . The substrate layer may be the second side of the substrate 10 , that is, the second substrate layer 103 .

[0195] In the embodiment of the present application, the sacrificial layer 31 can be formed by a physical deposition process such as sputtering and spin coating, or can also be formed by a chemical vapor deposition process. The specific formation method of the sacrificial layer 31 is not specifically limited in the embodiment of the present application.

[0196] In the present application, the material of the sacrificial layer 31 can be phosphate glass (PSG), silicon dioxide (SiO 2 ) and nickel (Ni) and other materials.

[0197] By selecting the above materials, on the one hand, the sacrificial layer 31 of the above materials has a better supporting effect when the piezoelectric component 20 is subsequently formed. On the other hand, it is also convenient to remove the sacrificial layer 31 to form the resonant cavity 30 later.

[0198] In some embodiments, the first side of the substrate 10 includes a first region 104 and a second region 105 connected to each other. In order to allow the subsequent piezoelectric component 20 to be connected to the substrate 10, the sacrificial layer 31 may be disposed only in the second region 105, and the piezoelectric component 20 may be directly connected to the first region 104 when the piezoelectric component 20 is formed.

[0199] In this configuration, the implementation of step 1001 may include the following steps: forming a support layer 33 on the first side of the substrate 10, the support layer 33 covering the first region 104 and the second region 105. Removing the portion of the support layer 33 opposite to the first region 104, and forming a sacrificial layer 31 with the portion of the support layer 33 opposite to the second region 105.

[0200] Combination Fig.12 , Fig.12 A schematic diagram of forming a support layer 33 on a substrate 10 is shown, and the support layer 33 can then be processed to obtain Fig.11 In order to make the first area 104 and the second area 105 clearer, Fig.13 The sacrificial layer 31 is separated from the substrate 10 so that the first region 104 and the second region 105 are exposed.

[0201] That is, the support layer 33 may be formed entirely on the first side of the substrate 10 , and then a portion of the support layer 33 may be removed, and the remaining support layer 33 may be used as a sacrificial layer 31 to support the subsequent formation of the piezoelectric component 20 .

[0202] The support layer 33 on the first region 104 may be removed by a process capable of removing materials, such as physical etching and chemical etching, to form a sacrificial layer 31 .

[0203] Of course, the sacrificial layer 31 may also be directly formed on the portion of the substrate 10 opposite to the second region 105 to simplify the process flow.

[0204] However, the process of forming a material layer at a partial position on a certain plane is not yet mature. In order to reduce the difficulty of forming the sacrificial layer 31 and improve the pass rate of the sacrificial layer 31, the sacrificial layer 31 can be formed by first depositing a supporting layer 33 and then etching the supporting layer 33.

[0205] Step 1002 , forming a piezoelectric component on a first side of a substrate and a sacrificial layer.

[0206] In the embodiment of the present application, the piezoelectric component 20 can be formed by a physical deposition process such as sputtering and spin coating, or can also be formed by a chemical vapor deposition process. The specific formation method of the piezoelectric component 20 is not specifically limited in the embodiment of the present application.

[0207] It should be noted that the deposition mentioned in the subsequent description of this application may refer to physical deposition and chemical deposition, and a suitable manufacturing process may be selected according to the properties of the actual material.

[0208] In some embodiments, Fig.14 As shown, step 1002 may specifically include the following steps.

[0209] Step 10021: forming a bottom electrode on the side of the substrate where the sacrificial layer is disposed.

[0210] Step 10022: Form a piezoelectric layer on the bottom electrode.

[0211] For details of step 10021 and step 10022, please refer to Fig.15 The structure shown.

[0212] The material of the piezoelectric layer 22 can be AlN, ScAlN, PZT, ZnO, LiNbO 3 Etc., the specific material of the piezoelectric layer 22 is not specifically limited in the embodiment of the present application.

[0213] In addition, in order to ensure the quality of the deposited piezoelectric layer 22 , a seed layer may be deposited on the side of the substrate 10 where the sacrificial layer 31 is disposed before depositing the bottom electrode 21 .

[0214] Step 10023: Etching a first conductive hole penetrating the piezoelectric layer on the piezoelectric layer. Fig.16 .

[0215] Step 10024: forming an electrode layer on the piezoelectric layer. Fig.17 .

[0216] Step 10025: Patterning the electrode layer. For details, please refer to Fig.18 .

[0217] The patterning process in this step is used to retain two electrode layers 29. One of them is the electrode layer 29 in the first conductive hole 26 and near the first conductive hole 26, which can form a bottom electrode connection structure 27. The other is separated from the bottom electrode connection structure 27 to form a top electrode 23.

[0218] The patterning process may be to remove the electrode layer 29 that is not required to be retained by etching or the like.

[0219] Step 10026: deposit a protective layer, and perform a planarization process on the side of the protective layer facing away from the substrate. Fig.19 .

[0220] Among them, the planarization treatment can adopt CMP (Chemical Mechanical Polishing) and other technologies.

[0221] Step 10027: Etching a second conductive hole and a third conductive hole on the protective layer. Fig. 20 .

[0222] The second conductive via 51 and the third conductive via 52 both penetrate the protective layer 50. The second conductive via 51 is opposite to at least a portion of the bottom electrode connection structure 27. The third conductive via 52 is opposite to at least a portion of the top electrode 23.

[0223] It should be noted that the number of the second conductive vias 51 and the number of the third conductive vias 52 can be multiple, such as 2, 3, 4, 5, etc. The number of the second conductive vias 51 and the number of the third conductive vias 52 can be different.

[0224] Of course, the number of the second conductive via 51 and the third conductive via 52 may also be one.

[0225] Step 10028: depositing a metal material layer on the protective layer. Fig.21 .

[0226] Step 10029: Patterning the metal material layer. For details, please refer to Fig. 22 .

[0227] The patterning process in this step is used to retain two metal material layers 24. One of them is the electrode layer at and near the second conductive hole 51, which can form the lead electrode body 28. The lead electrode body 28 is connected to the bottom electrode connection structure 27, and the two form the first lead electrode 211.

[0228] The other is the electrode layer at the third conductive hole 52 and near the third conductive hole 52 , where the second lead electrode 231 can be formed.

[0229] The patterning process may be to remove the metal material layer 24 that is not required to be retained by etching or the like.

[0230] In the case where the piezoelectric resonant sensor 100 further includes a cover 40, in this step, on the basis of retaining the above two metal material layers 24, one more metal material layer is retained to form a first bonding ring 241 for subsequent connection with the cover 40, such as Fig. 22 shown.

[0231] Step 1003, a release hole is provided on the side of the piezoelectric component away from the sacrificial layer, the release hole penetrates the piezoelectric component, and the sacrificial layer is released through the release hole to form a resonant cavity. Fig.23 .

[0232] Since the release hole 32 penetrates the piezoelectric component 20 , the provision of the release hole 32 can expose the sacrificial layer 31 below the piezoelectric component 20 . In this way, the sacrificial layer 31 can be released through the release hole 32 .

[0233] After the sacrificial layer 31 is released, the resonant cavity 30 can be formed at the original position of the sacrificial layer 31 , so that the position of the piezoelectric component 20 close to the resonant cavity 30 forms the cavity wall of the resonant cavity 30 .

[0234] It should be noted that the sacrificial layer 31 may be removed in different ways, such as chemical dissolution, plasma etching, heat treatment, and electrochemical dissolution, etc. In practical applications, a suitable way may be selected to remove the sacrificial layer 31 .

[0235] It should also be noted that, in this step, the piezoelectric resonator 25 can also be formed simultaneously through the release hole 32 .

[0236] That is, in addition to releasing the sacrificial layer 31 , the release holes 32 can also be used as the etched portion of the piezoelectric component 20 by setting the shape, position and number of the release holes 32 , and the remaining portion can form the piezoelectric resonator 25 .

[0237] In other words, after the piezoelectric component 20 is etched to form the piezoelectric resonator 25, the sacrificial layer 31 may be released by partially etching.

[0238] Of course, the etching of the piezoelectric component 20 and the release of the hole 32 can also be divided into two steps, and the present application does not make any specific limitation on this.

[0239] In step 1004, an input cavity is fabricated on the second side of the substrate. Fig.11 shows a schematic diagram of the structure of the substrate when it is not processed, Fig.24 The schematic diagram of the input cavity processed on the substrate is shown. For details, please refer to Fig.11 and Fig.24 .

[0240] The material on the second side of the substrate 10 can be removed by physical etching, chemical etching or other processes that can remove the material, and the removed portion can form the input cavity 11 .

[0241] As a preferred method, dry etching may be used.

[0242] It should be noted that step 1004 is to process the second side of the substrate 10, which is located on a different side from steps 1001 to 1003. Therefore, step 1004 can also be performed before step 1001, and the specific order of these steps is not specifically limited in the embodiment of the present application.

[0243] In the present application, the substrate 10 is an SOI wafer having an oxide layer 102 therein. When processing the input cavity 11 , the depth of the input cavity 11 can be determined based on the oxide layer 102 , thereby controlling the thickness of the pressure sensitive film 12 .

[0244] The piezoelectric resonant sensor 100 can be formed according to the method provided by the above steps 1001 to 1004 .

[0245] In order to simplify the manufacturing process of the piezoelectric resonant sensor 100 , step 1002 may also be simplified.

[0246] For example, by eliminating step 10026 and step 10027, a piezoelectric resonant sensor 100 without the protective layer 50 is obtained. Fig.25 shown.

[0247] Alternatively, steps 10026 to 10029 may be omitted, and the top electrode 23 and the metal material layer 24 may be combined into one layer, which may further simplify the processing flow. Fig.26 shown.

[0248] In step 10024 , the material of the electrode layer 29 may be consistent with the material of the metal material layer 24 .

[0249] In the embodiment of the present application, the piezoelectric resonant sensor 100 may further include a cover 40 . In this case, the method for manufacturing the piezoelectric resonant sensor 100 may further include the following steps.

[0250] Step 1005 , take the capping wafer and form a second bonding ring on one side of the capping wafer.

[0251] This step may specifically include depositing a metal layer 402 on one side of the capping wafer 401 , and then etching the metal layer 402 , so that a portion of the metal layer 402 that is retained can form a second bonding ring 43 . Fig. 27 4 shows a schematic diagram of forming a metal layer 402 on a capping wafer 401. Fig.28 Schematic diagram showing etching the metal layer 402 to form the second bonding ring 43, for details, please refer to Fig. 27 and Fig.28 .

[0252] In this step, the metal may be Ge metal. At this time, the metal material layer 24 forming the first bonding ring 241 may be Al metal. In this way, the first bonding ring 241 and the second bonding ring 43 may be bonded by Al-Ge bonding.

[0253] Of course, the first bonding ring 241 and the second bonding ring 43 may also be made of other materials, such as Au-Si bonding, silicon-silicon bonding, etc., or bonded by other bonding methods, such as anodic bonding, fusion bonding, etc.

[0254] Step 1006, processing a packaging cavity on the capping wafer. The packaging cavity and the second bonding ring are located on the same side of the wafer. Fig.29 .

[0255] The material of the capping wafer 401 may be removed by physical etching, chemical etching or other processes that can remove the material, and the removed portion may form a packaging cavity 41 .

[0256] Step 1007, forming an absorption layer on the cavity wall of the packaging cavity. Fig.30 .

[0257] The absorption layer 42 may be formed on the cavity wall of the packaging cavity 41 by deposition.

[0258] The absorption layer 42 may specifically be zirconium-vanadium-iron alloy (ZrVFe), zirconium (Zr), titanium-molybdenum alloy (TiMo), etc. The specific material of the absorption layer 42 is not specifically limited in the embodiment of the present application.

[0259] It should be noted that the packaging cavity 41 has a cavity wall opposite to the piezoelectric component 20, and the absorption layer 42 can be arranged on the cavity wall of the packaging cavity 41 opposite to the piezoelectric component 20. Of course, the absorption layer 42 can also be arranged at other positions, such as a side wall connected to the cavity wall of the packaging cavity 41 opposite to the piezoelectric component 20. The specific arrangement position of the absorption layer 42 is not specifically limited in the embodiment of the present application.

[0260] Step 1008: Bond the first bonding ring to the second bonding ring.

[0261] The specific bonding method between the first bonding ring 241 and the second bonding ring 43 has been explained in step 1005 , and in order to avoid repetition, the present application will not repeat it here.

[0262] It should be noted that the above steps are methods for manufacturing the piezoelectric resonant sensor proposed in this application, but those skilled in the art may delete or adjust the order of some of the above steps as needed.

[0263] 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 sensor, characterized in that: include: A substrate having a first side and a second side opposite to each other, wherein an input cavity is formed on the second side of the substrate; A piezoelectric component connected to a first side of the substrate, a portion of the piezoelectric component protruding toward a side of the substrate in a direction away from the substrate, and cooperating with the substrate to form a resonant cavity, wherein the resonant cavity is at least partially opposite to the input cavity; A pressure-sensitive film is formed on the substrate at a portion opposite to the input cavity. The input cavity is used to receive the pressure to be detected and transmit the pressure to be detected to the pressure-sensitive film so that the pressure-sensitive film drives the piezoelectric component to deform through the cavity wall of the resonant cavity.

2. The piezoelectric resonant sensor according to claim 1, characterized in that: The piezoelectric component includes a piezoelectric layer, a bottom electrode and a top electrode; The bottom electrode is connected to a first side of the substrate, the bottom electrode protrudes toward a side of the substrate in a direction away from the substrate, and cooperates with the substrate to form the resonant cavity; The piezoelectric layer is connected to a side of the bottom electrode facing away from the substrate, and the top electrode is connected to a side of the piezoelectric layer facing away from the bottom electrode; The bottom electrode and the top electrode are both used for connecting to an external circuit.

3. The piezoelectric resonant sensor according to claim 2, characterized in that: The piezoelectric component includes a first lead electrode for connecting to an external circuit, one end of the first lead electrode is connected to the bottom electrode, and the middle of the first lead electrode passes through the piezoelectric layer so that the other end of the first lead electrode is located on the side of the piezoelectric layer away from the substrate.

4. The piezoelectric resonant sensor according to claim 2, characterized in that: The piezoelectric component further includes a driving electrode and a detecting electrode, wherein the driving electrode and the detecting electrode are both connected to the top electrode and are located on a side of the top electrode away from the piezoelectric layer; The driving electrode and the detecting electrode are both used to connect to an external circuit, so that the driving electrode drives the piezoelectric layer to vibrate, and the detecting electrode detects the vibration of the piezoelectric layer.

5. The piezoelectric resonant sensor according to claim 1, characterized in that: The piezoelectric resonant sensor further includes a cover connected to a side of the piezoelectric component away from the substrate, and a projection of the cover along a direction from the piezoelectric component to the substrate covers the resonant cavity.

6. The piezoelectric resonant sensor according to claim 5, characterized in that: A packaging cavity is provided on a side of the cover facing the substrate, the packaging cavity covers the piezoelectric component, and along the direction from the piezoelectric component to the substrate, the projection of the cavity wall of the packaging cavity covers the resonant cavity; The packaging cavity is a vacuum cavity, and an absorption layer is provided on the cavity wall of the packaging cavity, and the absorption layer is used to absorb the gas released after the sealing cover is connected to the piezoelectric resonant sensor; Alternatively, there is pressure in the packaging cavity.

7. The piezoelectric resonant sensor according to claim 1, characterized in that: The substrate comprises a first substrate layer, an oxide layer and a second substrate layer which are stacked, the input cavity is arranged on a side of the second substrate layer away from the first substrate layer, and the input cavity penetrates the second substrate layer so that a part of the oxide layer is exposed through the input cavity; The portion of the first substrate layer opposite to the input cavity forms the pressure sensitive film, and the pressure sensitive film cooperates with the piezoelectric component to form the resonant cavity.

8. The piezoelectric resonant sensor according to claim 1, characterized in that: The piezoelectric resonant sensor further includes a protection layer, which is arranged on a side of the piezoelectric component facing away from the substrate.

9. A method for preparing a piezoelectric resonant sensor, the method being used to produce the piezoelectric resonant sensor according to any one of claims 1 to 8, characterized in that: The preparation method comprises: forming a sacrificial layer on a first side of the substrate; forming the piezoelectric component on the first side of the substrate and the sacrificial layer; A release hole is provided on a side of the piezoelectric component away from the sacrificial layer, wherein the release hole penetrates the piezoelectric component; releasing the sacrificial layer through the release hole to form the resonant cavity; The input cavity is processed on a second side of the substrate.

10. The method for preparing a piezoelectric resonant sensor according to claim 9, characterized in that: The first side of the substrate includes a first region and a second region connected to each other, and forming a sacrificial layer on the first side of the substrate includes: forming a support layer on the first side of the substrate, wherein the support layer covers the first region and the second region; A portion of the support layer opposite to the first region is removed, and a portion of the support layer opposite to the second region forms the sacrificial layer.

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