CN114339556A

CN114339556A - Piezoelectric microphone and electronic device

Info

Publication number: CN114339556A
Application number: CN202011050430.6A
Authority: CN
Inventors: 于媛媛; 冯志宏; 徐景辉
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2020-09-29
Filing date: 2020-09-29
Publication date: 2022-04-12

Abstract

The application discloses piezoelectric microphone and electronic equipment. The piezoelectric microphone includes a base and a piezoelectric film. The base body encloses an inner cavity, and the piezoelectric film is fixed on one side of the base body to shield the inner cavity. The piezoelectric film comprises a piezoelectric layer, a central electrode and an edge electrode, wherein the central electrode comprises a first central electrode, a second central electrode and a third central electrode which are mutually spaced, the first central electrode, the second central electrode and the third central electrode form a first capacitor structure and a second capacitor structure, and then the first central electrode, the second central electrode and the third central electrode are connected in parallel to form a central sensing unit. The edge electrode also comprises a first edge electrode, a second edge electrode and a third edge electrode which are mutually spaced, the first edge electrode, the second edge electrode and the third edge electrode also form a third capacitor structure and a fourth capacitor structure, and then the third capacitor structure, the second edge electrode and the third capacitor structure are connected in parallel to form an edge sensing unit. The central sensing unit is electrically connected with the edge sensing unit to output a sensing signal of the piezoelectric microphone. This application piezoelectric microphone has possessed higher sensitivity through the connection setting between each electric capacity structure to this application electronic equipment's sound collection effect has been promoted.

Description

Piezoelectric microphone and electronic device

Technical Field

The present application relates to the field of electronic technologies, and in particular, to a piezoelectric microphone and an electronic device.

Background

In recent years, a micro-electro-mechanical system (MEMS) microphone can rapidly replace a conventional Electret Condenser (ECM) microphone due to its advantages of small size, low power consumption, capability of completing a surface mounting process, and the like, and becomes a mainstream audio pickup device in electronic equipment. The MEMS microphone mainly comprises a capacitance type MEMS microphone and a piezoelectric type MEMS microphone, wherein the piezoelectric type MEMS microphone has a wider application prospect due to the outstanding low power consumption characteristic, the advantages of water resistance and dust resistance and the like.

The piezoelectric microphone utilizes the piezoelectric film layer to vibrate under the action of a sound signal, and completes the conversion of the sound signal to an electric signal by collecting electric charges caused by vibration. The area capable of effectively converting the collected electric charges into the electric signals is an effective area, but the stress formed by each area of the piezoelectric film layer in the vibration process is different, the situation that the capacitance is too large and the voltage is too small exists in a part of the areas, and the situation that the area of the effective area in the piezoelectric film layer is limited is avoided in the other part of the areas, so that the sensitivity of the piezoelectric microphone is limited.

Disclosure of Invention

An object of the present application is to provide a piezoelectric microphone and an electronic apparatus including the same. The piezoelectric microphone is provided with the electrode structure on the piezoelectric material, and the connection mode of the electrode structure is optimized, so that the sensitivity of the piezoelectric microphone is improved.

In a first aspect, the present application relates to a piezoelectric microphone, including a substrate and a piezoelectric film, where the substrate is annular and encloses an inner cavity, and the piezoelectric film is fixed on one side of the substrate to shield the inner cavity;

the piezoelectric film comprises a piezoelectric layer, a center electrode and an edge electrode, the piezoelectric layer is laid in the plane direction of the piezoelectric film, the center electrode is fixed in the middle of the piezoelectric layer, and the edge electrode is fixed on the periphery of the piezoelectric layer;

in the thickness direction of the piezoelectric film, the central electrode comprises a first central electrode, a second central electrode and a third central electrode which are spaced from each other, the third central electrode is positioned between the first central electrode and the second central electrode, the first central electrode and the third central electrode form a first capacitor, the second central electrode and the third central electrode form a second capacitor, and the first capacitor and the second capacitor are connected in parallel to form a central sensing unit;

the edge electrode comprises a first edge electrode, a second edge electrode and a third edge electrode which are spaced from each other, the third edge electrode is positioned between the first edge electrode and the second edge electrode, the first edge electrode and the third edge electrode form a third capacitor, the second edge electrode and the third edge electrode form a fourth capacitor, and the third capacitor and the fourth capacitor are connected in parallel to form an edge sensing unit;

the central sensing unit is electrically connected with the edge sensing unit to output a sensing signal of the piezoelectric microphone.

In the piezoelectric microphone, the inner cavity formed by the substrate is shielded by the piezoelectric film, so that the sound signal transmitted from the inner cavity can cause the vibration of the piezoelectric film. And collecting charges generated by vibration of the piezoelectric film by using the central electrode and the edge electrode arranged in the piezoelectric film. The capacitance value sensed by the central electrode is improved by the parallel connection of the first capacitor and the second capacitor formed by the central electrode; the capacitance value sensed by the edge electrode is improved by the parallel connection of the third elevator and the fourth capacitor formed by the edge electrode. And finally, electrically connecting the central sensing unit and the edge sensing unit, and correspondingly improving the obtained sensing voltage and/or the obtained sensing capacitance. Therefore, the overall induction sensitivity of the piezoelectric microphone is improved.

In addition, the central electrode and the edge electrode which are separately arranged can collect the induced charges in the two areas based on the stress directions of the central area and the edge area of the piezoelectric film are opposite. And aiming at the phenomenon that the polarities of the charges in the thickness direction of the piezoelectric film are opposite, the central electrode collects the charges through the first capacitor and the second capacitor respectively, and the edge electrode collects the charges through the third capacitor and the fourth capacitor respectively, so that the effect of effectively collecting the charges is realized.

In one possible embodiment, a projection of the first center electrode on the second center electrode coincides with an outer shape of the second center electrode, and a projection of the third center electrode on the second center electrode also coincides with an outer shape of the second center electrode in a thickness direction of the piezoelectric film.

In this implementation manner, the areas and shapes of the first central electrode, the second central electrode, and the third central electrode are the same, and the three positions are aligned with each other, which is beneficial to controlling the area ratio of the central electrode on the piezoelectric film and avoiding the occurrence of a useless area in the central electrode where the charge collection efficiency is not high.

A possible embodiment, in any one direction of the plane of the piezoelectric membrane, the geometric center of the piezoelectric layer has a first distance L from the edge of the piezoelectric layer, the geometric center of the center electrode has a first dimension L1 from the edge of the center electrode, and the first dimension L1 satisfies the condition: l50% or more and L1 or more and L5% or more. Preferably, L40% or more and L1 or more and L20% or more may be controlled.

In this implementation, when the piezoelectric film is vibrated by an acoustic signal, the area of the central electrode on the piezoelectric film is limited, so as to ensure that the central electrode is disposed corresponding to the effective area of the piezoelectric film, thereby ensuring effective collection of charges.

In one possible embodiment, a distance between the first center electrode and the third center electrode in a thickness direction of the piezoelectric film is equal to a distance between the second center electrode and the third center electrode.

In this implementation, the distance between the first central electrode and the third central electrode affects the capacitance value of the first capacitor, and the distance between the second central electrode and the third central electrode affects the capacitance value of the second capacitor, so that when the distance between the first central electrode and the third central electrode is equal to the distance between the second central electrode and the third central electrode, the capacitance value of the first capacitor can be controlled to be equal to the capacitance value of the second capacitor.

In a possible embodiment, a projection of the first edge electrode on the second edge electrode coincides with an outer shape of the second edge electrode, and a projection of the third edge electrode on the second edge electrode also coincides with an outer shape of the second edge electrode in a thickness direction of the piezoelectric film.

In this implementation manner, in a manner similar to the central electrode, the first edge electrode, the second edge electrode, and the third edge electrode are arranged to have the same area and shape, and the positions of the first edge electrode, the second edge electrode, and the third edge electrode are aligned with each other, which is beneficial to controlling the area ratio of the edge electrode on the piezoelectric film and avoiding the occurrence of a dead area in the edge electrode where the charge collection efficiency is not high.

In one possible embodiment, the geometric center of the piezoelectric layer is a first distance L from the edge of the piezoelectric layer, the inner edge of the edge electrode is a second dimension L2 from the outer edge of the edge electrode, and the second dimension L2 satisfies the condition: l50% or more and L2 or more and L5% or more. Preferably, L30% or more and L2 or more and L10% or more may be controlled.

In this implementation, when the piezoelectric film is vibrated by a sound signal, the area of the edge electrode on the piezoelectric film is limited, so as to ensure that the edge electrode is disposed corresponding to the effective area of the piezoelectric film, thereby ensuring effective collection of charges.

In one possible embodiment, a distance between the first edge electrode and the third edge electrode in a thickness direction of the piezoelectric film is equal to a distance between the second edge electrode and the third edge electrode.

In this implementation, since the distance between the first edge electrode and the third edge electrode affects the capacitance value of the third capacitor, and the distance between the second edge electrode and the third edge electrode affects the capacitance value of the fourth capacitor, when the distance between the first edge electrode and the third edge electrode is equal to the distance between the second edge electrode and the third edge electrode, the capacitance value of the third capacitor and the capacitance value of the fourth capacitor can be controlled to be equal to each other.

In one possible embodiment, the first center electrode is flush with the first edge electrode, the second center electrode is flush with the second edge electrode, and the third center electrode is flush with the third edge electrode in a thickness direction of the piezoelectric film.

In this implementation, since each layer of electrode structure in the piezoelectric film is formed by a patterning process, the first center electrode is disposed flush with the first edge electrode, and patterning of the first edge electrode can be simultaneously completed when the first center electrode is patterned. In a similar way, the second central electrode and the second edge electrode are arranged in a flush manner, and the third central electrode and the third edge electrode are arranged in a flush manner, so that two electrode structures can be formed simultaneously in one patterning process, and the manufacturability of the piezoelectric microphone is improved.

In one possible embodiment, the first central electrode is divided into at least two first central sub-electrodes, the second central electrode is divided into at least two second central sub-electrodes, the third central electrode is divided into at least two third central sub-electrodes, and the number of the first central sub-electrodes, the number of the second central sub-electrodes and the number of the third central sub-electrodes are equal;

one of the first central sub-electrodes and one of the third central sub-electrodes form a first sub-capacitor, one of the second central sub-electrodes and one of the third central sub-electrodes form a second sub-capacitor, and one of the first sub-capacitors and one of the second sub-capacitors are connected in parallel to form a central sub-sensing unit;

a plurality of the central sub-sensing units are connected in series to form the central sensing unit.

In this implementation manner, the central sensing unit is divided into a plurality of central sub-sensing units, so that the voltage sensed by the central electrode can be further increased on the premise of ensuring that the capacitance value sensed by the central electrode is not reduced.

In a possible embodiment, in the thickness direction of the piezoelectric film, a projection of one of the first center sub-electrodes on the second center sub-electrode corresponding to its position coincides with an outer shape of the second center sub-electrode, and a projection of one of the third center sub-electrodes on the second center sub-electrode corresponding to its position also coincides with an outer shape of the second center sub-electrode.

In this implementation manner, in the orientation of each first center sub-electrode, the area and the shape of the first center sub-electrode are the same as those of the second center sub-electrode and the third center sub-electrode corresponding to the first center sub-electrode, which is beneficial to controlling the area ratio of the center sub-electrode on the piezoelectric film and avoiding the occurrence of a useless area with low charge collection efficiency.

In one possible embodiment, the at least two first central sub-electrodes have the same shape and area, the at least two second central sub-electrodes have the same shape and area, and the at least two third central sub-electrodes have the same shape and area.

In this implementation manner, the first central electrode is controlled to be uniformly divided into a plurality of first central sub-electrodes having the same area, and the second central electrode and the third central electrode are also controlled to be uniformly divided, so that a plurality of central sub-sensing units having the same voltage and capacitance values are favorably formed, and the voltage and capacitance sensed by the central sensing units formed after the central sub-sensing units are connected in series are further improved.

In one possible embodiment, the first edge electrode is divided into at least two first edge sub-electrodes, the second edge electrode is divided into at least two second edge sub-electrodes, the third edge electrode is divided into at least two third edge sub-electrodes, and the number of the first edge sub-electrodes, the number of the second edge sub-electrodes and the number of the third edge sub-electrodes are equal;

one of the first edge sub-electrodes and one of the third edge sub-electrodes form a third sub-capacitor, one of the second edge sub-electrodes and one of the third edge sub-electrodes form a fourth sub-capacitor, and one of the third sub-capacitors and one of the fourth sub-capacitors are connected in parallel to form one edge sub-sensing unit;

the edge sub-sensing units are connected in series to form the edge sensing unit.

In this implementation manner, the edge sensing unit is divided into a plurality of edge sub-sensing units, so that the voltage sensed by the edge electrode can be further increased on the premise of ensuring that the capacitance value sensed by the edge electrode is not reduced.

In a possible embodiment, in the thickness direction of the piezoelectric film, a projection of one of the first edge sub-electrodes on the second edge sub-electrode corresponding to the position thereof coincides with the outer shape of the second edge sub-electrode, and a projection of one of the third edge sub-electrodes on the second edge sub-electrode corresponding to the position thereof also coincides with the outer shape of the second edge sub-electrode.

In this embodiment, in the orientation of each of the first edge sub-electrodes, the area and the shape of the second edge sub-electrode and the third edge sub-electrode corresponding to the first edge sub-electrode are the same, which is beneficial to controlling the area ratio of the edge sub-electrode on the piezoelectric film and avoiding the occurrence of useless areas with low charge collection efficiency.

In a possible embodiment, the at least two first edge sub-electrodes have the same shape and area, the at least two second edge sub-electrodes have the same shape and area, and the at least two third edge sub-electrodes have the same shape and area.

In this implementation manner, the first edge electrode is controlled to be uniformly divided into a plurality of first edge sub-electrodes having the same area, and the second edge electrode and the third edge electrode are also controlled to be uniformly divided, so that a plurality of edge sub-sensing units having the same voltage and capacitance values are favorably formed, and the voltage and capacitance sensed by the edge sensing units formed after the edge sub-sensing units are connected in series are further improved.

In a possible embodiment, the central sub-sensing unit and the edge sensing unit are electrically connected through a connection line.

In this implementation, after the central sub-sensing unit is divided into a plurality of central sub-sensing units, the connection between the central sub-sensing unit and the edge sensing unit may also be implemented by a connection line.

In a possible embodiment, the piezoelectric layer is further provided with a vent slit, and the vent slit penetrates through the piezoelectric film along the thickness direction of the piezoelectric film.

In this implementation, the arrangement of the ventilation slit can balance the air pressure on the two sides of the piezoelectric film, so as to avoid the pressure difference between the air pressure and the outside formed in the relatively closed inner cavity. Because the thickness-to-diameter ratio is relatively small, the piezoelectric film is relatively sensitive to the pressure difference between the upper pressure and the lower pressure, and the arrangement of the vent slits can protect the piezoelectric film from being broken due to the pressure difference between the upper pressure and the lower pressure when the piezoelectric film vibrates.

In one possible embodiment, the vent slit includes a first end and a second end opposite to each other along a length direction thereof, and an extension line from the second end to the first end passes through a geometric center of the piezoelectric film.

In this implementation, by disposing the extension line of the ventilation slit to pass through the geometric center of the piezoelectric film, the resonant frequency of the piezoelectric film can be better controlled, and more uniform induced charges can be obtained in the planar direction of the piezoelectric film.

In a possible embodiment, the first end projects into the central electrode, and/or

The second end extends into the edge electrode.

In this implementation, the vent slits extend into the center electrode and/or the edge electrode, and can also partially relieve internal stress of the center electrode and/or the edge electrode, thereby improving structural stability of the center electrode and/or the edge electrode.

In one possible embodiment, the second end of the vent slit extends completely through the edge electrode.

In this embodiment, the edge electrodes can be divided synchronously by providing the ventilation slits through the edge electrodes. Namely, the edge electrode is divided into a plurality of edge sub-sensing units by utilizing the structure of the ventilation slit, and the manufacturing process of the piezoelectric microphone can be integrated.

In a possible embodiment, the first end and/or the second end is further provided in the shape of a circular hole having a diameter larger than the width of the vent slit.

In this implementation manner, the round hole may be disposed to eliminate a stress concentration phenomenon at the first end and/or the second end, and prevent a crack from being generated at the first end and/or the second end due to the stress concentration.

In a possible embodiment, the piezoelectric film includes a plurality of the vent slits, and the vent slits are uniformly distributed along a circumferential direction of the piezoelectric film.

In this implementation manner, the plurality of ventilation slits are uniformly distributed along the circumferential direction of the piezoelectric film, that is, the plurality of ventilation slits are distributed on the piezoelectric film in a centrosymmetric manner, which is more beneficial to controlling the resonant frequency of the piezoelectric film, so that the charges collected by each region of the piezoelectric film are more balanced.

In a possible embodiment, the width of the vent slit is less than or equal to 3 μm.

In this implementation manner, the width of the vent slit may be set to control the influence of the vent slit on the resonant frequency of the piezoelectric film, so as to ensure that the frequency corresponding range of the piezoelectric film is within a preset range.

In one possible embodiment, the total thickness of the piezoelectric film is between 0.3 μm and 2 μm;

the first central electrode, the second central electrode, the third central electrode, the first edge electrode, the second edge electrode and the third edge electrode have a thickness of 0.01-0.15 μm.

In this implementation manner, the thickness of the piezoelectric film, and the thickness of the first center electrode, the second center electrode, the third center electrode, the first edge electrode, the second edge electrode, and the third edge electrode are set, so that the thickness ratio of each electrode to the piezoelectric film can be ensured, and the vibration sensitivity of the piezoelectric film is ensured on the premise that the structural stability of the piezoelectric film is improved by using each electrode.

In a possible embodiment, the central sensing unit is connected in series with the edge sensing unit to output a sensing signal of the piezoelectric microphone.

In this implementation, because the central induction unit has promoted its capacitance value size that senses through the parallelly connected of first electric capacity and second electric capacity, and the edge induction unit has also promoted its capacitance value size that senses through the parallelly connected of third electric capacity and fourth electric capacity, therefore the central induction unit establishes ties with the edge induction unit after, can also promote the size of magnitude of voltage value, reaches the effect that promotes induction capacitance and induced voltage simultaneously.

In a possible embodiment, the substrate is made of a silicon wafer, an insulating member is further disposed between the substrate and the piezoelectric film, the insulating member is annular, and the shape of the insulating member matches the shape of the substrate.

In this implementation, when the host material of the substrate is a silicon wafer, the substrate is a conductor. In order to avoid the influence of the current on the substrate on the charge induction of the piezoelectric film, an insulating member needs to be disposed between the substrate and the piezoelectric film to insulate the piezoelectric film from the substrate.

In a possible embodiment, the substrate is made of an insulating material.

In this implementation, the insulating property of the substrate itself blocks the electrical conduction between the substrate and the piezoelectric film, i.e., the substrate itself can serve as an insulating structure to realize the insulation between the piezoelectric film and the substrate.

In a second aspect, an embodiment of the present application provides another piezoelectric microphone, including a substrate, a piezoelectric film, and a supporting layer, where the substrate is annular and encloses an inner cavity, the piezoelectric film and the supporting layer are stacked, and both the piezoelectric film and the supporting layer are fixed to one side of the substrate to shield the inner cavity;

in the thickness direction of the piezoelectric film, the central electrode comprises a first central electrode and a second central electrode which are spaced from each other, and the first central electrode and the second central electrode form a central sensing unit of a capacitance structure;

the edge electrodes comprise a first edge electrode and a second edge electrode which are mutually spaced, and the first edge electrode and the second edge electrode form an edge sensing unit of a capacitance structure;

the central sensing unit is connected with the edge sensing unit in series to output a sensing signal of the piezoelectric microphone.

In this implementation, the internal cavity formed by the substrate is shielded by the piezoelectric membrane and the supporting layer together, so that an acoustic signal transmitted from the internal cavity can cause vibration of the piezoelectric membrane and the supporting layer. Meanwhile, the support layer can adjust the position of the central plane of the planar structure formed by the piezoelectric film and the support layer, so that electric charges formed by sound signal excitation can be collected through the piezoelectric film. And the central sensing unit of the capacitor structure formed by the central electrode and the edge sensing unit of the capacitor structure formed by the edge electrode can collect charges in areas where the charges generated by the piezoelectric film are relatively high respectively. This application piezoelectric microphone can promote its voltage value and the capacitance value of collecting, has promoted this application piezoelectric microphone's whole sensitivity to this application from this.

In one possible embodiment, a projection of the first center electrode on the second center electrode in a thickness direction of the piezoelectric film coincides with an outer shape of the second center electrode; and/or

The projection of the first edge electrode on the second edge electrode coincides with the outline of the second edge electrode.

In this implementation, the areas and shapes of the first central electrode and the second central electrode are the same, and the areas and shapes of the first edge electrode and the second edge electrode are the same, which is beneficial to controlling the area ratio of the central electrode and/or the edge electrode on the piezoelectric film and avoiding the occurrence of useless areas in the central electrode and/or the edge electrode where the charge collection efficiency is not high.

In one possible embodiment, the geometric center of the piezoelectric layer has a first distance L ' from the edge of the piezoelectric layer, the geometric center of the center electrode has a first dimension L1 ' from the edge of the center electrode, and the first dimension L1 ' satisfies the condition: l50% or more and L1' or more and L5%; and/or

The inner edge of the edge electrode has a second dimension L2 'from the outer edge of the edge electrode, and the second dimension L2' satisfies the condition: l50% or more and L2 or more and L5% or more.

In this implementation manner, when the piezoelectric film is vibrated by an acoustic signal, the area of the piezoelectric film that can effectively collect charges is limited, a certain limitation is imposed on the area of the central electrode and/or the edge electrode on the piezoelectric film, and it can be ensured that the central electrode and/or the edge electrode correspondingly cover the effective area of the piezoelectric film, so as to ensure effective collection of charges.

In one possible embodiment, the first center electrode is flush with the first edge electrode, and the second center electrode is flush with the second edge electrode in a thickness direction of the piezoelectric film.

In this implementation, since each layer of electrode structure in the piezoelectric film is formed by a patterning process, the first center electrode is disposed flush with the first edge electrode, and patterning of the first edge electrode can be simultaneously completed when the first center electrode is patterned. Similarly, the second center electrode and the second edge electrode are arranged in a flush manner, so that two electrode structures can be formed simultaneously in one patterning process, and the manufacturability of the piezoelectric microphone is improved.

In one possible embodiment, the first central electrode is divided into at least two first central sub-electrodes, the second central electrode is also divided into a plurality of second central sub-electrodes, and the number of the first central sub-electrodes is equal to the number of the second central sub-electrodes;

one first central sub-electrode and one second central sub-electrode form a central sub-sensing unit with a capacitance structure;

a plurality of the central sub-sensing units are connected in series to form the central sensing unit; and/or

The first edge electrode is divided into at least two first edge sub-electrodes, the second edge electrode is also divided into a plurality of second edge sub-electrodes, and the number of the first edge sub-electrodes is equal to that of the second edge sub-electrodes;

one first edge sub-electrode and one second edge sub-electrode form an edge sub-sensing unit of a capacitor structure;

In this implementation manner, the central sensing unit is divided into a plurality of central sub-sensing units, and/or the edge sensing electrode is divided into a plurality of edge sub-sensing units, so that the voltage sensed by the central electrode and/or the edge electrode can be further increased on the premise of ensuring that the capacitance value sensed by the central electrode and/or the edge electrode is not reduced.

In one possible embodiment, in the thickness direction of the piezoelectric film, a projection of one of the first center sub-electrodes on the second center sub-electrode corresponding to its position coincides with the outer shape of the second center sub-electrode; and/or

The projection of one first edge sub-electrode on the second edge sub-electrode corresponding to the position of the first edge sub-electrode is coincident with the outline of the second edge sub-electrode

In this implementation manner, in the orientation of each first center sub-electrode, the area and the shape of the first center sub-electrode corresponding to the position of the first center sub-electrode are the same, and/or the area and the shape of each first edge sub-electrode corresponding to the position of the first edge sub-electrode are the same, which is beneficial to controlling the area ratio of the center sub-electrode and/or the edge sub-electrode on the piezoelectric film, and avoiding the occurrence of a useless area with low charge collection efficiency.

In a possible embodiment, the piezoelectric layer is further provided with a vent slit, and the vent slit penetrates through the piezoelectric film and the support layer simultaneously along the thickness direction of the piezoelectric film.

In one possible embodiment, the support layer is located between the piezoelectric film and the substrate, and the main material of the support layer is an insulating material.

In this implementation manner, since the main structure of the support layer may include an insulating material, the support layer is disposed between the piezoelectric film and the base, and when the base is made of any material, the piezoelectric film and the substrate can be insulated due to the insulating property of the support layer, so as to avoid possible interference of current on the substrate with the piezoelectric film.

In a possible embodiment, the piezoelectric film is located between the support layer and the base, the main material of the substrate is a silicon wafer, an insulating member is further disposed between the substrate and the piezoelectric film, the insulating member is ring-shaped, and the shape of the insulating member matches the shape of the substrate.

In this embodiment, since the piezoelectric film is located between the support layer and the base, the base has conductivity on the premise that a main material of the base is a silicon wafer. In order to avoid the influence of the current on the substrate on the piezoelectric film through the substrate, an insulating member is further arranged between the piezoelectric film and the substrate to realize the insulation between the piezoelectric film and the substrate.

In a third aspect, the present application provides an electronic device comprising an audio pickup device. The audio pickup device comprises a substrate, a post-processing circuit and the piezoelectric microphone;

the base plate is provided with a sound inlet hole, the sound inlet hole is communicated with the inner cavity of the base in the piezoelectric microphone, the post-processing circuit is electrically connected with the piezoelectric microphone, and the post-processing circuit is used for processing induction signals of the piezoelectric microphone.

The audio pickup device carried by the electronic equipment comprises the piezoelectric microphone of the first aspect or the second aspect. It is understood that the sensitivity of the audio pickup device is improved because the response sensitivity of the piezoelectric microphone of the first aspect or the second aspect to the sound signal is higher. The electronic equipment also obtains a better sound collection effect.

Drawings

Fig. 1 is a schematic structural diagram of an audio pickup device according to an embodiment of the present disclosure;

FIG. 2 is a schematic cross-sectional view A-A of the audio pickup device of FIG. 1;

fig. 3 is a schematic structural view of the piezoelectric microphone shown in fig. 1;

FIG. 4 is a schematic cross-sectional view of the piezoelectric microphone of FIG. 3 taken along B-B;

FIG. 5 is a schematic partial cross-sectional view of a piezoelectric membrane in the piezoelectric microphone of FIG. 4;

FIG. 6 is a graph illustrating vibrational mode analysis of the piezoelectric film of FIG. 5 in one possible embodiment;

FIG. 7 is a schematic view of the lower surface of the piezoelectric film shown in FIG. 5;

FIG. 8 is a schematic top surface view of the piezoelectric film of FIG. 5;

FIG. 9 is a schematic partial cross-sectional view of the piezoelectric film of FIG. 5;

FIG. 10 is a schematic diagram of the electrical connections of the sensing element in one embodiment of the piezoelectric film of FIG. 5;

FIG. 11 is an equivalent connection schematic of the circuit of FIG. 10;

FIG. 12 is a schematic diagram of electrical connections in another embodiment of the piezoelectric film of FIG. 5;

FIG. 13 is a graph illustrating vibrational mode analysis of the piezoelectric film of FIG. 5 in one possible embodiment;

FIG. 14 is a schematic structural view of another embodiment of the piezoelectric film of FIG. 5;

FIG. 15 is a schematic electrical circuit connection diagram of the piezoelectric film of FIG. 14;

FIG. 16 is a schematic structural view of yet another embodiment of the piezoelectric film of FIG. 5;

FIG. 17 is a schematic electrical circuit connection diagram of the piezoelectric film of FIG. 16;

FIG. 18 is a schematic structural view of yet another embodiment of the piezoelectric film of FIG. 5;

FIG. 19 is a schematic diagram of electrical connections in one embodiment of the piezoelectric film of FIG. 18;

FIG. 20 is a schematic electrical circuit diagram of an alternative embodiment of the piezoelectric film of FIG. 18;

FIG. 21 is a schematic diagram of electrical connections in yet another embodiment of the piezoelectric film of FIG. 18;

FIG. 22 is a schematic diagram of electrical connections in yet another embodiment of the piezoelectric film of FIG. 18;

FIG. 23 is a schematic structural view of another embodiment of the piezoelectric film shown in FIG. 5;

FIG. 24 is a schematic diagram of a further embodiment of the piezoelectric film of FIG. 5;

FIG. 25 is a schematic diagram of a further embodiment of the piezoelectric film of FIG. 5;

FIG. 26 is a schematic diagram of another embodiment of the piezoelectric film of FIG. 5;

FIG. 27 is a schematic diagram of an alternative embodiment of the piezoelectric film of FIG. 26;

fig. 28 is a partial structural view of the piezoelectric film shown in fig. 27;

FIG. 29 is a graph illustrating a trend of residual stress in the piezoelectric film of FIG. 26 in one possible embodiment;

FIG. 30a is a graph of a stress simulation analysis of the piezoelectric film of FIG. 26 in one possible embodiment;

FIG. 30b is a graph of a stress simulation analysis of a prior art cantilever beam structure piezoelectric microphone;

FIG. 31 is a schematic illustration of a resonant frequency analysis of the piezoelectric microphone of FIG. 26 in one possible embodiment;

FIG. 32 is a schematic illustration of a signal to noise ratio analysis of the piezoelectric microphone of FIG. 26 in one possible embodiment;

fig. 33 is a schematic structural view of another embodiment of the piezoelectric microphone shown in fig. 3;

fig. 34 is a schematic structural diagram of a piezoelectric microphone according to another embodiment of the present application;

FIG. 35 is a schematic cross-sectional view of the piezoelectric microphone of FIG. 34 taken along C-C;

FIG. 36 is a cross-sectional schematic view of another embodiment of the piezoelectric microphone shown in FIG. 35;

fig. 37 is a schematic circuit connection diagram of the piezoelectric microphone shown in fig. 34;

FIG. 38 is a schematic structural view of a further embodiment of the piezoelectric microphone of FIG. 34;

FIG. 39 is a schematic electrical circuit connection diagram of the piezoelectric film layer shown in FIG. 38;

FIG. 40 is a schematic structural diagram of yet another embodiment of the piezoelectric microphone of FIG. 34;

FIG. 41 is a schematic electrical circuit connection diagram of the piezoelectric film layer shown in FIG. 40;

FIG. 42 is a schematic diagram of another embodiment of the piezoelectric microphone of FIG. 34;

FIG. 43 is a schematic electrical circuit connection diagram of one embodiment of the piezoelectric film layer of FIG. 42;

FIG. 44 is a schematic electrical connection diagram of another embodiment of the piezoelectric film of FIG. 42;

fig. 45 is a schematic structural view of another embodiment of the piezoelectric microphone shown in fig. 34.

Detailed Description

Technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

The numbering of the components as such, e.g., "first", "second", etc., is used herein only to distinguish the objects as described, and does not have any sequential or technical meaning. The term "coupled", as used herein, includes both direct and indirect coupling, unless otherwise indicated. In the description of the present application, it is to be understood that the terms "upper", "lower", "front", "back", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are used only for convenience in describing the present application and simplifying the description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present application.

In this application, unless expressly stated or limited otherwise, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through intervening media. Also, a first feature "on" or "over" a second feature may be directly or diagonally over the first feature or may simply indicate that the first feature is at a higher level than the second feature. A first feature "under" or "beneath" a second feature may be directly or obliquely under the first feature or may simply mean that the first feature is at a lesser elevation than the second feature.

Please refer to fig. 1, which illustrates an internal structure of an audio pickup device 200 according to an embodiment of the present application. The audio pickup device 200 is disposed in an electronic device (not shown) for implementing an audio capturing function of the electronic device. The audio pickup device 200 includes a substrate 201, a piezoelectric microphone 100, and a post-processing circuit 202. The piezoelectric microphone 100 and the post-processing circuit 202 are both fixed on the substrate 201, the post-processing circuit 202 is located on one side of the piezoelectric microphone 100, and the piezoelectric microphone 100 is electrically connected to the post-processing circuit 202. In one embodiment, the piezoelectric microphone 100 and the post-processing circuit 202 are electrically connected through conductive traces 204 on the substrate 201. The piezoelectric microphone 100 is used for sensing sound signals and converting the sound signals into electric signals to be transmitted to the post-processing circuit 202. The post-processing circuit 202 is configured to perform amplification, filtering, analog-to-digital conversion, or equalization on the electrical signal, and then transmit the processed electrical signal to units such as a processor of the electronic device, so as to realize acquisition of a sound signal by the audio pickup device 200.

The electronic equipment can be products such as mobile phones, tablet computers, notebook computers, intelligent sound equipment and other intelligent household appliances. In this embodiment, the electronic device is a mobile phone as an example. The substrate 201 may be a Printed Circuit Board (PCB) or a ceramic circuit board inside the electronic device. The substrate 201 may be implemented by selecting a part of an area of an existing PCB in the electronic device, for example, by using a part of an area of a PCB such as a main board and a sub-main board of the electronic device, so as to improve an integration level of the electronic device.

Fig. 2 is a schematic cross-sectional view of the audio pickup device 200 shown in fig. 1 taken along line a-a. In the embodiment of fig. 2, a housing 203 is also secured to the substrate 201. The piezoelectric microphone 100, the post-processing circuit 202, and the case 203 are all fixed to the same side of the substrate 201. The housing 203 and the substrate 201 enclose a receiving space for receiving the piezoelectric microphone 100 and the post-processing circuit 202 on the substrate 201 and protecting the piezoelectric microphone 100 and the post-processing circuit 202.

The piezoelectric microphone 100 includes a substrate 10 and a piezoelectric film 20. The substrate 10 is fixedly connected with the substrate 201, and the piezoelectric film 20 is fixed on the side of the substrate 10 away from the substrate 201. The substrate 10 is annular, and the annular substrate 10 surrounds the cavity 11. The substrate 201 includes a sound inlet 2011, and the cavity 11 of the substrate 10 communicates with the sound inlet 2011. In one embodiment, the inner cavity of the sound inlet 2011 is aligned with the inner wall of the cavity 11.

The piezoelectric film 20 is a planar structure, and the piezoelectric film 20 covers the substrate 10 to shield the cavity 11 and the sound inlet 2011 communicating with the cavity 11. The piezoelectric film 20 is configured to receive an acoustic signal transmitted from the sound inlet 2011 and generate vibration when excited by the acoustic signal. The piezoelectric film 20 collects and converts the electric charge formed by vibration into an electric signal, thereby realizing the function of collecting the sound signal by the piezoelectric microphone 100.

The substrate 10 may be made of a silicon wafer, and in other embodiments, the substrate 10 may be made of a material mainly made of silicon. In the illustration of fig. 2, an insulator 30 is also provided between the piezoelectric film 20 and the substrate 10. The insulating member 30 serves to insulate the piezoelectric film 20 from the base 10, so as to prevent the current on the substrate 201 from entering the piezoelectric film 20 and interfering with the collection of the sound signal. The insulator 30 is also provided in an annular shape, and the annular shape of the insulator 30 matches the annular shape of the substrate 10. Opposite flat surfaces of the annular insulating member 30 are bonded to the substrate 10 and the piezoelectric film 20, respectively. In one embodiment, the insulator 30 may be made of polysilicon, silicon nitride (Si3N4), or silicon dioxide (SiO 2).

It is understood that in other embodiments, the substrate 10 may be made of an insulating material, and the piezoelectric film 20 may be fixedly connected to the substrate 10.

Fig. 3 is a schematic diagram of the piezoelectric microphone 100 according to the present application. The piezoelectric film 20 includes a piezoelectric layer 21 and a plurality of electrodes 22 provided in the piezoelectric layer 21. In one embodiment, the piezoelectric layer 21 can be made of a piezoelectric material, which can include one or more of aluminum nitride (AlN), scandium-doped aluminum nitride (AlScN), lead zirconate titanate (PZT), or zinc oxide (ZnO); the electrodes 22 are made of metal, and the material of the motor 22 may include molybdenum (Mo), titanium (Ti), platinum (Pt), aluminum (Al), gold (Au), and the like. Of course, the materials of the piezoelectric layer 21 and the electrode 22 are only examples, and the actual product is not limited to the above materials and their compounds.

After the sound signal enters the cavity 11 through the sound inlet 2011, the piezoelectric film 20 vibrates under the action of the sound signal, so as to drive each region of the piezoelectric layer 21 to form stress, and thus generate charges. The electric charges generated by the piezoelectric layer 21 can be transmitted to the post-processing circuit 202 by collecting the electric charges through the electrodes 22, and the electric signals are amplified by the post-processing circuit 202 and then processed by a rear-end audio module (not shown) of the electronic device, so that a sound pickup function is realized.

In the piezoelectric microphone 100 according to the embodiment of the present application, the electrode 22 disposed on the piezoelectric layer 21 includes the center electrode 221 and the edge electrode 222, and the center electrode 221 and the edge electrode 222 are disposed at an interval in the plane direction of the piezoelectric film 20. The central electrode 221 is located at the central position of the piezoelectric film 20, and the edge electrode 222 is arranged around the central electrode 221 and located at the edge position of the piezoelectric film 20.

Further, please refer to fig. 4 showing a cross-sectional view of the piezoelectric film 20 in the B-B direction. In the thickness direction of the piezoelectric film 20, the piezoelectric layer 21 has a lower surface 211 close to the chamber 11, and an upper surface 212 disposed opposite to the lower surface 211. It will be appreciated that the upper surface 212 is located on the side of the piezoelectric layer 21 remote from the chamber 11 relative to the lower surface 211. The center electrode 221 includes a center lower electrode 2211 near the lower surface 211, a center upper electrode 2212 near the upper surface 212, and a center middle electrode 2213 located between the center lower electrode 2211 and the center upper electrode 2212. It is understood that the center lower electrode 2211 corresponds to the first center electrode, the center upper electrode 2212 corresponds to the second center electrode, and the center middle electrode 2213 corresponds to the third center electrode in the claims of the present application.

In one embodiment, the bottom surface of the central lower electrode 2211 is flush with the lower surface 211 of the piezoelectric layer 21 in the thickness direction of the piezoelectric film 20. In other embodiments, the top surface of the central lower electrode 2211 may be flush with the lower surface 211 of the piezoelectric layer 21, or the bottom surface of the central lower electrode 2211 is higher than the lower surface 211 of the piezoelectric layer 21, i.e., the central lower electrode 2211 is integrally included in the piezoelectric layer 21. Whereas for the center upper electrode 2212, in the embodiment shown in fig. 4, the bottom surface of the center upper electrode 2212 is flush with the top surface 212 of the piezoelectric layer 21. It is understood that in other embodiments, the top surface of the central upper electrode 2212 can be flush with the upper surface 212 of the piezoelectric layer 21, or the top surface of the central upper electrode 2212 is lower than the upper surface 212 of the piezoelectric layer 21, i.e., the central upper electrode 2212 is also entirely contained within the piezoelectric layer 21.

The center middle electrode 2213 can be disposed at a midpoint between the center lower electrode 2211 and the center upper electrode 2212. Of course, the center middle electrode 2213 may also be closer to the center upper electrode 2212 than to the center lower electrode 2211 in other embodiments, or the center middle electrode 2213 may be closer to the center lower electrode 2211 than to the center upper electrode 2212. And in the thickness direction of the piezoelectric film 20, the center middle electrode 2213 is disposed at an interval from the center lower electrode 2211 and the center upper electrode 2212, respectively, and piezoelectric materials of the piezoelectric layer 21 are disposed at intervals between the center middle electrode 2213 and the center lower electrode 2211 and between the center middle electrode 2213 and the center upper electrode 2212.

The edge electrode 222 is also provided with an edge lower electrode 2221, an edge upper electrode 2222, and an edge middle electrode 2223 in the thickness direction of the piezoelectric film 20. The edge lower electrode 2221 is close to the lower surface 211, the edge upper electrode 2222 is close to the upper surface 212, and the edge middle electrode 2223 is located between the edge lower electrode 2221 and the edge upper electrode 2222. The piezoelectric material of the piezoelectric layer 21 is also interposed between the edge middle electrode 2223 and the edge lower electrode 2221, and between the edge middle electrode 2223 and the edge upper electrode 2222. It is understood that the edge lower electrode 2221 also corresponds to the first edge electrode, the edge upper electrode 2222 corresponds to the second edge electrode, and the edge middle electrode 2223 corresponds to the third edge electrode in the claims of the present application.

It is understood that the bottom surface of the edge lower electrode 2221 may be flush with the lower surface 211. In other embodiments, the edge lower electrode 2221 may also be disposed such that its top surface is flush with the lower surface 211, or the edge lower electrode 2221 is disposed such that its bottom surface is higher than the lower surface 211; the bottom surface of the edge top electrode 2222 may then be flush with the top surface 212. In other embodiments, the edge upper electrode 2222 may also be disposed with its top surface flush with the upper surface 212, or the edge upper electrode 2222 may be disposed with its top surface lower than the upper surface 212.

The edge middle electrode 2223 may be disposed at an intermediate position of the distance between the edge lower electrode 2221 and the edge upper electrode 2222. Of course, the edge middle electrode 2223 may be closer to the edge upper electrode 2222 than to the edge lower electrode 2221, or the edge middle electrode 2223 may be closer to the edge lower electrode 2221 than to the edge upper electrode 2222 in other embodiments.

In manufacturing the piezoelectric film 20, the lower layer structure of the electrode 22 is usually manufactured first, and patterned to form the central lower electrode 2211 and the edge lower electrode 2221; then, a layer of piezoelectric material is grown, an intermediate layer structure of the electrode 22 is manufactured, and patterning is performed to form a center middle electrode 2213 and an edge middle electrode 2223; finally, a layer of piezoelectric material is grown, and an upper layer structure of the electrode 22 is formed and patterned to form a center upper electrode 2212 and an edge upper electrode 2222. Thus, in one embodiment, the edge lower electrode 2221 is also flush with the center lower electrode 2211, the edge upper electrode 2222 is flush with the center upper electrode 2212, and the edge middle electrode 2223 is flush with the center middle electrode 2213, which can simplify the manufacturing process of the piezoelectric film 20.

Referring to fig. 5, fig. 5 is a partial cross-sectional view of the cross-sectional view of fig. 4. In the illustration of fig. 5, since the edge electrode 222 is disposed around the periphery of the central electrode 221, the edge electrode 222 on one side of the central electrode 221 is shown in fig. 5 for illustrating the structure of the sensing unit more clearly. In the piezoelectric film 20 of the present application, the first sensing cell 301 and the second sensing cell 302 composed of the center electrode 221, and the third sensing cell 303 and the fourth sensing cell 304 composed of the edge electrode 222 are formed.

The central middle electrode 2213 and the central lower electrode 2211 form a first sensing unit 301 of a capacitance structure, the induced charges formed by the piezoelectric layer 21 are collected by the first sensing unit 301 to form a first capacitance C1, and a first voltage V1 is formed between the central middle electrode 2213 and the central lower electrode 2211; the central middle electrode 2213 and the central upper electrode 2212 form a second sensing unit 302 with a capacitive structure, the induced charges formed by the piezoelectric layer 21 are collected by the second sensing unit 201 to form a second capacitor C2, and a second voltage V2 is formed between the central middle electrode 2213 and the central upper electrode 2212. It is understood that the first sensing unit 301 may correspond to a first capacitor in the present specification, and the second sensing unit 302 may correspond to a second capacitor in the present specification.

In one embodiment, the center middle electrode 2213 is located at the midpoint of the distance between the center lower electrode 2211 and the center upper electrode 2212, and the shapes and sizes of the center middle electrode 2213, the center lower electrode 2211 and the center upper electrode 2212 are the same, i.e. the areas of the center middle electrode 2213, the center lower electrode 2211 and the center upper electrode 2212 are the same. Or described as a projection of the center middle electrode 2213 on the center lower electrode 2211 coincides with the shape of the center lower electrode 2211 in the thickness direction of the piezoelectric film 20; the projection of the central upper electrode 2212 on the central lower electrode 2211 also coincides with the shape of the central lower electrode 2211.

For the piezoelectric layer 21, the charge generated by its vibration is distributed in a centrosymmetric manner. There is a center plane B1 at the center of the piezoelectric layer 21 in the thickness direction of the piezoelectric film 20. The polarity of the charge developed by the piezoelectric layer 21 above the center plane B1 is opposite to the polarity of the charge developed by the piezoelectric layer 21 below the center plane B1. Therefore, when the center middle electrode 2213 is disposed at an intermediate position of the distance between the center lower electrode 2211 and the center upper electrode 2212, the center middle electrode 2213 coincides with the center plane B1. At this time, the first voltage V1 sensed by the first sensing unit 301 and the second voltage V2 sensed by the second sensing unit 201 are equal in value and opposite in direction to each other, i.e., | V1| ═ V2 |.

On the other hand, since the shapes and areas of the central lower electrode 2211, the central middle electrode 2213 and the central upper electrode 2212 are consistent, the first capacitance C1 sensed by the first sensing unit 301 and the second capacitance C2 sensed by the second sensing unit 302 are also equal in value, i.e., C1 is equal to C2.

The third sensing unit 303 and the fourth sensing unit 304 formed by the edge electrode 222 are also similar to the first sensing unit 301 and the second sensing unit 302 formed by the center electrode 221. The third sensing unit 303 is composed of an edge middle electrode 2223 and an edge bottom electrode 2221, the induced charge formed by the piezoelectric layer 21 is collected by the third sensing unit 303 to form a third capacitor C3, and a third voltage V3 is formed between the edge middle electrode 2223 and the edge bottom electrode 2221; the fourth sensing unit 304 is composed of an edge middle electrode 2223 and an edge upper electrode 2222, the induced charges formed by the piezoelectric layer 21 are collected by the fourth sensing unit 304 to form a fourth capacitor C4, and a fourth voltage V4 is formed between the edge middle electrode 2223 and the edge upper electrode 2222. It is understood that the third sensing unit 303 can correspond to a third capacitor in the present specification, and the fourth sensing unit 304 can correspond to a fourth capacitor in the present specification.

In one embodiment, the edge middle electrode 2223 is also positioned at the midpoint of the distance between the edge lower electrode 2221 and the edge upper electrode 2222, and the shape and size of the edge middle electrode 2223, the edge lower electrode 2221, and the edge upper electrode 2222 are the same. Thus, for the third sensing unit 303 and the fourth sensing unit 304, an effect of | V3| ═ V4|, and C3 ═ C4 is also formed. The third voltage V3 and the fourth voltage V4 are equal in value and opposite in value, and the third capacitor C3 and the fourth capacitor C4 are equal in value.

Referring specifically to fig. 6, a diagram of a vibration mode analysis of the piezoelectric film 20 in one implementation is shown. The piezoelectric film 20 vibrates due to the sound pressure after receiving the sound signal. The vibration of the piezoelectric film 20 generates stress and causes a phenomenon of stress concentration in the interior thereof. As can be seen from fig. 6, the main regions of stress concentration are distributed over the central region a0, and the edge region a2 of the piezoelectric film 20. That is, the stress generated at the central region a0 and the edge region a2 is relatively large. According to the formula of the charge quantity:

Q＝Ad₃₁δ equation (1);

wherein d is₃₁Is the piezoelectric coefficient of the piezoelectric material in the piezoelectric layer 21; delta is the stress generated by the corresponding area under the action of the sound signal; a is the effective area where the resulting stress meets the charge collection requirements. It can be seen that on the piezoelectric film 20, the effective area capable of forming stress concentration and generating a large stress satisfying the charge collection requirement is not large, and is concentrated at the positions of the center a0 and the edge a2 thereof. In the present embodiment, the piezoelectric film 20 has a circular shape, and thus the central region a0 where stress is concentrated has a circular shape. Since the substrate 10 is circular, the piezoelectric film 20 and the substrate 10 are connected and fixed in a ring shape, and thus the edge regions a2 are also distributed in a ring shape. While the transition region a1 between the central region a0 and the edge region a2 has relatively low stress, both at or near zero stress. In the case of a limited active area, there is a limitation in the sensitivity of the conventional piezoelectric microphone, for example, the sensitivity of a conventional piezoelectric microphone product is maintained at about-43 dB.

After the center electrode 221 and the edge electrode 222 are provided, a region in which the induced stress is large in the piezoelectric film 20 can be covered, and the sensing area can be increased, thereby improving the charge collection effect. Meanwhile, the directions of the respective stresses formed between the central region a0 and the edge region a2 are opposite to each other, and when the stress formed by the central region a0 is defined as tensile stress, the stress of the edge region a2 is compressive stress; conversely, when the stress formed in the central region a0 is compressive, the stress in the edge region a2 is tensile.

Corresponding to the electrode 22, for the first sensing unit 301 and the third sensing unit 303 located at the same plane height, the first sensing unit 301 forms a first voltage V1 by tensile stress at the central region AO, and the third sensing unit 303 forms a third voltage V3 by compressive stress at the edge region a 2. Therefore, the stress direction of the first sensing cell 301 is opposite to that of the third sensing cell 303, and the polarities of the first voltage V1 and the third voltage V3 formed thereby are also opposite; the second sensing unit 302 and the fourth sensing unit 304, which are also located at the same level, have a similar relationship, i.e. the polarities of the second voltage V2 and the fourth voltage V4 are opposite.

Please refer to fig. 7 for a schematic view of a lower surface 211 of the piezoelectric film 20, and fig. 8 for a schematic view of an upper surface 212 of the piezoelectric film 20. The piezoelectric microphone 100 of the present application is further provided with a connecting wire 23 on the piezoelectric film 20. In the present embodiment, the connecting wires 23 are connected between the center lower electrode 2211 and the edge lower electrode 2212, and between the center upper electrode 2212 and the edge upper electrode 2222. Further, please refer to a cross-sectional view of the piezoelectric film 20 illustrated in fig. 9. A first connection terminal 241 and a second connection terminal 242 are further disposed at the center middle electrode 2213 and the edge middle electrode 2223, respectively, the first connection terminal 241 can be used as a ground terminal or an output terminal of the piezoelectric microphone 100, and the corresponding second connection terminal 242 can be used as an output terminal or a ground terminal of the piezoelectric microphone 100. The first connection end 241 and the second connection end 242 are electrically connected to the post-processing circuit 202 at the rear end, respectively, so as to electrically connect the piezoelectric microphone 100 and the post-processing circuit 202.

The second connecting terminal 242 is disposed at the middle electrode 2223, and the electrical connection with the post-processing circuit 202 can be directly completed through the conductive trace 204 on the substrate 201. The first connection end 241 is disposed at the center middle electrode 2213, and a via 25 (see fig. 8) needs to be formed on the piezoelectric layer 21 near the center middle electrode 2213 to lead out the electrical signal and connect to the conductive trace 204 of the substrate 201, so as to electrically connect the first connection end 241 to the post-processing circuit 202 at the rear end.

Through the above-mentioned wiring arrangement, the circuit connection in the piezoelectric film 20 of the present application can be schematically seen in fig. 10: the first sensing unit 301 (composed of the center middle electrode 2213 and the center lower electrode 2211) and the second sensing unit 302 (composed of the center middle electrode 2213 and the center upper electrode 2212) are connected in parallel, meanwhile, the third sensing unit 303 (composed of the edge middle electrode 2223 and the edge lower electrode 2221) and the fourth sensing unit 304 (composed of the edge middle electrode 2223 and the edge upper electrode 2222) are also connected in parallel, then the first sensing unit 301 and the second sensing unit 302 which are connected in parallel are connected in series with the third sensing unit 303 and the fourth sensing unit 304 which are connected in parallel, and finally, an electric signal is output to a rear-end post-processing circuit. In fig. 10, for the sake of clarity of the respective sensing elements, the center middle electrode 2213 common to the first sensing element 301 and the second sensing element 302 is separately drawn, and the edge middle electrode 2223 common to the third sensing element 303 and the fourth sensing element 304 is also separately drawn.

As mentioned above, the first voltage V1 has a polarity opposite to that of the second voltage V2, and the first voltage V1 also has a polarity opposite to that of the third voltage V3, i.e., the polarity of the second voltage V2 is the same as that of the third voltage V3. Thus, the circuit connection diagram of fig. 10 appears in an actual configuration as the equivalent circuit connection diagram of fig. 11: the center upper electrode 2212 is connected to the edge upper electrode 2222, the center lower electrode 2211 is connected to the edge lower electrode 2221, and the center middle electrode 2213 and the edge middle electrode 2223 are connected to the post-processing circuit 202 at the rear end as output terminals of the piezoelectric film 20, respectively.

At this time, the central electrode 221 has a parallel structure of the first sensing cell 301 and the second sensing cell 302, forming a central sensing cell 401. Accordingly, the voltage V12 ═ V1 ═ V2|, and the capacitance C12 ═ C1+ C2 of the central sensing unit 401; for the edge electrode 222, the third sensing unit 303 and the fourth sensing unit 304 are also in a parallel structure, forming an edge sensing unit 402. Accordingly, the voltage V34 ═ V3 ═ V4|, and the capacitance C34 ═ C3+ C4 of the edge sensing unit 402.

After the center sensing unit 401 and the edge sensing unit 402 are connected in series, the induced voltage V sensed by the piezoelectric microphone 100 of the present application is obtained as follows:

v — V12+ V34 formula (2);

simultaneously, the inductive capacitance C that this application piezoelectric microphone 100 sensed:

the conventional piezoelectric microphone is usually provided with an electrode structure covering only the edge region or the central region, so that the voltage V 'sensed by the conventional piezoelectric microphone is usually only V12 or V34, and the capacitance C' sensed by the conventional microphone is usually C12 or C34. And through the structural arrangement of the central electrode 221 and the edge electrode 222 on the piezoelectric film 20 in the piezoelectric microphone 100 of the present application, and the arrangement of the connection mode of the two, the obtained induced voltage V and the induced capacitance C are both promoted when the piezoelectric film 20 of the present application is excited by a sound signal, and then the sensitivity of the piezoelectric microphone 100 of the present application is promoted.

Referring to fig. 12, the center electrode 221 and the edge electrode 222 may be connected in parallel. That is, the first connection end 241 is led out from the center middle electrode 2213 of the center electrode 221, the center upper electrode 2212 and the center lower electrode 2211 are respectively connected to the edge middle electrode 2223, and finally the second connection end 242 is led out by the edge upper electrode 2222 and the edge lower electrode 2221. The induced voltage V that this application piezoelectric microphone 100 sensed this moment:

meanwhile, the inductive capacitance C sensed by the piezoelectric microphone 100:

c ═ C12+ C34 formula (3');

it can be seen that, for the piezoelectric microphone 100 in which the center electrode 221 is connected in parallel with the edge electrode 222, the induced voltage V and the induced capacitance C obtained are also larger than those of the conventional piezoelectric microphone. This embodiment is suitable for the case where the voltage requirement of the piezoelectric microphone 100 is relatively low, but the requirement for the capacitor is relatively high.

In one embodiment, the total thickness of the piezoelectric film 20 is controlled to be 0.3-2 μm, and the thickness of the central lower electrode 2211 and the edge lower electrode 2221, the central middle electrode 2213 and the edge middle electrode 2223, and the central upper electrode 2212 and the edge upper electrode 2222 is controlled to be 0.01-0.15 μm. The thickness of the electrode 22 may increase the overall stiffness of the piezoelectric film 20 while not affecting the vibration sensitivity of the piezoelectric film 20 to acoustic signals.

In one embodiment, defining the footprint of the edge electrode 222 to the circular piezoelectric layer 21 with a radius R in the plane, it is desirable to keep the distance from the inner ring edge of the edge electrode 222 to the outer edge of the piezoelectric layer 21 less than or equal to R x 50% and greater than or equal to R x 5%. Preferably, in this embodiment, the distance from the inner ring of the edge electrode 222 to the outer edge of the piezoelectric layer 21 is R × 10 to R × 30%.

Correspondingly, the coverage area of the piezoelectric layer 21 by the central electrode 221 is also defined as the radius r of the central electrode 221, and r satisfies the condition: r50% or more and R5% or more. Preferably, in the present embodiment, the radius R of the center electrode 221 is R × 20 to R × 40%.

In other embodiments, if the piezoelectric layer 21 has a shape other than a circular shape, for the central electrode 221, when the center of the piezoelectric layer 21 is separated from the edge of any direction by a distance L, the first dimension L1 of the central electrode 221 in the direction also needs to satisfy the condition: l50% or more and L1 or more and L5% or more. Preferably, L40% or more and L1 or more and L20% or more can be controlled; in this direction, the second dimension L2 of the edge electrode 222 from the inner edge to the outer edge is also required to be less than or equal to L x 50% and greater than or equal to L x 5%. Preferably, L30% or more and L2 or more and L10% or more may be controlled.

The coverage area of each of the center electrode 221 and the edge electrode 222 to the piezoelectric layer 21 is also an important factor affecting the sensitivity of the piezoelectric microphone 100. Referring to fig. 13, in one possible implementation, taking the edge electrode 222 as an example, regarding the simulated structure of the edge electrode 222, the edge area of the piezoelectric layer 21 covered by the edge electrode 222 is divided from the outside to the inside, so as to obtain a first stress area 01, a second stress area 02, and a third stress area 03. Wherein the voltage V of the first stress region 01₀₁Satisfies the following conditions:

wherein Q is₀₁The amount of charge generated by the first stress area 01 under the action of an acoustic signal; c₀₁Is the capacitance value of the first stress region 01; d is the thickness of the first stress region 01; ε is the dielectric constant of the piezoelectric material, for the illustration of FIG. 13, the different stress regions haveEpsilon is the same; a. the₀₁Is the area of the first stress region 01.

And the charge amount Q of the first stress region 01₀₁Then:

Q₀₁＝A₀₁d₃₁δ₀₁formula (5);

wherein d is₃₁Is the piezoelectric coefficient of the piezoelectric material including the first stress region 01, the second stress region 02, and the third stress region 03; delta₀₁Is the stress to which the first stress region 01 is subjected under the influence of the acoustic signal. From this, it can be seen that the voltage V of the first stress region 01 is obtained by substituting the formula (5) into the formula (4)₀₁It can also be expressed as:

by analogy, the voltage of the second stress region 02 can also be derived

Voltage of the third stress region 03

Because the first stress region 01 is located at the outer periphery of the second stress region 02, the stress of the first stress region 01 is greater than that of the second stress region 02. Similarly, the stress in the second stress region 02 is greater than the stress in the third stress region 03, i.e., δ₁>δ₂>δ₃. From this, it can be concluded that the voltages obtained by the coverage of the edge electrode 222 for the three different stress regions described above have the following relationship: v₀₁>V₀₂>V₀₃。

The above analysis is based on the edge electrode 222 covering only the first stress region 01, the second stress region 02 or the third stress region 03, but in practical embodiments, in addition to the edge electrode 222 covering only the first stress region 01, the edge electrode 222 may be arranged to cover both the first stress region 01 and the second stress region 02, in which case the edge electrode 222 may be arranged to cover both the first stress region 01 and the second stress region 02Voltage V sensed by the electrode 222₀₁₂Can be expressed as:

due to V₀₁>V₀₂>V₀₃V can be deduced₀₁₂<V₀₁. Further, the edge electrode 222 can cover the first stress region 01, the second stress region 02 and the third stress region 03 at the same time, and the voltage V of the edge click 222 is applied₀₁₂₃Expressed as:

also due to V₀₁>V₀₂>V₀₃V can be deduced₀₁₂₃<V₀₁₂<V₀₁。

That is, as for the coverage area of the piezoelectric layer 21 by the edge electrode 222, the smaller the coverage area of the edge electrode 222 is, the larger the voltage is outputted, but with the adverse effect that the output capacitance is too small. Formula for the thermal noise spectrum n due to reference material dielectric loss:

wherein k is the boltzmann constant; t is temperature (unit: Kelvin); omega is the working frequency; c is a capacitor; tan δ is a dielectric tangent value of the piezoelectric material. Since the dielectric loss angle of the piezoelectric material is constant, the tangent value thereof is also a fixed value. In this case, too small a capacitance C causes a large noise floor output due to dielectric loss. In addition, the capacitor C of the piezoelectric microphone 100 and the back-end post-processing circuit 202 form a series capacitor, and the post-processing circuit 202 can be regarded as a capacitive voltage divider of the piezoelectric microphone 100. When the capacitance C of the piezoelectric microphone 100 is too small, it may cause the output capacitance of the post-processing circuit 202 to divide as a capacitive divider and reduce the output signal of the post-processing circuit 202. Therefore, the capacitance C of the piezoelectric microphone 100 is generally not less than 0.1 pF.

On the other hand, if the coverage area of the edge electrode 222 is too large, the voltage V output from the piezoelectric microphone 100 is reduced. That is, it appears that the piezoelectric microphone 100 contributes only capacitance and does not contribute electric charge, resulting in a decrease in the output voltage V and a decrease in the output sensitivity. Therefore, for the piezoelectric microphone 100 of the present application, in order to ensure that the output capacitance C meets the requirement and obtain a larger voltage V, the coverage area of the piezoelectric layer 21 by the edge electrode 222 needs to be defined. And the distance from the edge of the inner ring where the edge electrode 222 is disposed to the outer edge of the piezoelectric layer 21 is less than or equal to R x 50% and greater than or equal to R x 5%; and simultaneously, the radius of the central electrode 221 is r, and then r satisfies the condition: after R is more than or equal to 5%, the coverage of the effective area of the piezoelectric layer 21 by the edge electrode 222 and the central electrode 221 can be ensured.

Referring to fig. 14, in the planar direction of the piezoelectric film 20, the central electrode 221 is further patterned and divided, such that the central lower electrode 2211 is divided into at least two central lower units 2211a, the central middle electrode 2213 is divided into a plurality of central middle units 2213a with the same number, and the central upper electrode 2212 is divided into a plurality of central upper units 2212a with the same number. It is understood that the central lower unit 2211a may correspond to a first central sub-electrode, the central upper unit 2212a may correspond to a second central sub-electrode, and the central middle unit 2213a may correspond to a third central sub-electrode in the claims of the present application.

In one embodiment, the shapes and areas of the plurality of central lower cells 2211a are equal, i.e., the central lower electrodes 2211 are equally divided into a plurality of central lower cells 2211a of the same area; the center electrode 2213 is equally divided into a plurality of center cells 2213a having the same area; the center upper electrode 2212 is equally divided into a plurality of center upper units 2212a having the same area. In one embodiment, the parting lines for each of the plurality of central lower elements 2211a pass through the geometric center of the piezoelectric film 20.

In the thickness direction of the piezoelectric film 20, each central lower unit 2211a has the same shape and size as the central middle unit 2213a corresponding to its position, and the central middle unit 2212a also has the same shape and size as the central upper unit 2212a corresponding to its position. Thus, the center lower element 2211a, the center middle element 2213a, and the center upper element 2212a, which correspond in position in the thickness direction of the piezoelectric film 20, form one center sub-sensing element 403. A plurality of central sub-sensing units 403 constitute a central sensing unit 401. The voltage value and the capacitance value sensed by each central sub-sensing unit 403 are respectively the same, and the voltage and the capacitance formed after the connection are also larger. In the same manner as the central sensing unit 401, in this embodiment, each central sub-sensing unit 403 is also connected in parallel with its two capacitor structures, and then the central sub-sensing units 403 are connected in series and then connected in series with the edge sensing unit 402, so as to form the output voltage V and the output capacitor C of the piezoelectric film 20. It is understood that the two capacitance structures of the central sub-sensing unit 403 may correspond to the first sub-capacitance and the second sub-capacitance in the claims of the present application.

Specifically, please refer to the connection diagram of fig. 15. After the center upper element 2212a and the center lower element 2211a of the front center sub-sensing element 403 are turned on, the center middle element 2213a of the center sub-sensing element 403 is simultaneously connected to the center upper element 2212a and the center lower element 2211a of the next center sub-sensing element 403, and after each center sub-sensing element 403 is sequentially connected, the center middle element 2212a of the center sub-sensing element 403 at the end is simultaneously connected to the edge upper electrode 2222 and the edge lower electrode 2221 of the edge sensing element 402. Finally, the connection line between the central upper unit 2212a and the central lower unit 2211a of the front central sub-sensing unit 403 is used as the first connection end 241, and the lead wire led out from the edge middle electrode 2223 is used as the second connection end 242, which are respectively connected to the rear post-processing circuit 202.

At this time, since a structure in which two capacitors are connected in parallel is formed inside the plurality of central sub-sensing units 403, and then the plurality of central sub-sensing units 403 are connected in series, the output voltage V12a of the central sensing unit 401 composed of the plurality of central sub-sensing units 403 becomes 6 × V12 for the post-processing circuit 202 at the rear end; capacitance of the central sensing unit 401

After the edge sensing unit 402 is connected in series, the voltage V output by the piezoelectric film 20 of the present application can be expressed as:

V-V12 a + V34-6 × V12+ V34 formula (10);

the capacitance C output by the piezoelectric film 20 can be expressed as:

it can be seen that in the present embodiment, by dividing the center electrode 221, the induced voltage V12a of the center induction unit 401 is raised, and the output voltage V of the piezoelectric film 20 is raised. On the basis that the output capacitance C of the piezoelectric film 20 meets the requirement, a larger output voltage V can be obtained, and the sensitivity of the piezoelectric microphone 100 of the present application is further improved.

In another embodiment, referring to fig. 16, the edge electrode 222 is also divided into at least two edge lower cells 2221a, the edge middle electrode 2223 is divided into a plurality of edge middle cells 2223a with the same number, and the edge upper electrode 2222 is divided into a plurality of edge upper cells 2222a with the same number by patterning in the plane direction of the piezoelectric film 20. In one embodiment, the edge lower cells 2221a may be arranged to have the same shape and area, that is, the edge lower electrodes 2221 are equally divided into a plurality of edge lower cells 2221a having the same area; the edge center electrodes 2223 are equally divided into a plurality of edge center cells 2223a having the same area; the edge upper electrode 2222 is equally divided into a plurality of edge upper cells 2222a having the same area. In one embodiment, the extension line of the dividing line of the plurality of edge lower units 2221a also passes through the geometric center of the piezoelectric film 20. It is understood that the edge lower cell 2221a may correspond to a first edge sub-electrode, the edge upper cell 2222a may correspond to a second edge sub-electrode, and the edge upper cell 2223a may correspond to a third edge sub-electrode in the claims.

Similarly, in the thickness direction of the piezoelectric film 20, the edge lower cell 2221a, the edge middle cell 2223a, and the edge upper cell 2222a, which are located in correspondence with each other, are also equal in shape and size, and constitute one edge sub-sensing cell 404 by being connected in parallel. The plurality of edge sub-sensing units 404 constitute the edge sensing unit 402. In the embodiment of fig. 16, the edge sensing unit 402 is composed of 6 edge sub-sensing units 404, and when the sensing voltage of the non-separated edge sensing unit 402 is V34, the voltage of each edge sub-sensing unit 404 is V34; when the sensing capacitance of the undivided edge sensing cell 402 is C34, the capacitance of each edge sub-sensing cell is C34/6. The voltage value and the capacitance value sensed by each edge sub-sensing unit 404 are respectively the same, and the voltage and the capacitance formed by the connection are larger. Please synchronously view the connection diagram of fig. 17. After the edge sub-sensing units 404 are connected in parallel, a plurality of edge sub-sensing units 404 are connected in series and then connected in series with the central sensing unit 401, so as to form the output voltage V and the output capacitance C of the piezoelectric film 20. Specifically, the edge upper unit 2222a and the edge lower unit 2221a of the edge sub-sensing unit 404 at the front end are conducted and led out of the first connection terminal 241, the edge middle unit 2223a of the edge sub-sensing unit 404 is simultaneously connected to the edge upper unit 2222a and the edge lower unit 2221a of the next edge sub-sensing unit 404, after each edge sub-sensing unit 404 is sequentially connected, the edge middle unit 2223a of the edge sub-sensing unit 404 at the tail end is simultaneously connected to the center upper electrode 2212 and the center lower electrode 2211 of the center sensing unit 401, and finally the second connection terminal 242 is led out of the center middle electrode 2213. The first connection terminal 241 and the second connection terminal 242 are respectively connected to the post-processing circuit 202 at the rear end. It is understood that the two capacitance structures of the edge sub-sensing unit 404 itself may correspond to the third sub-capacitance and the fourth sub-capacitance in the claims of the present application.

Similar to the connection manner of fig. 14 and fig. 15, the edge sensing unit 402 is divided in this embodiment, so that the output voltage V34a of the edge sensing unit 402 is 6 × V34; capacitance of edge sensing cell 402

After the central sensing unit 401 is connected in series, the piezoelectric film 20 outputsThe voltage V can be expressed as:

V-V12 + V34 a-V12 + 6-V34 formula (12);

the capacitance C output by the piezoelectric film 20 can be expressed as:

similarly, the induced voltage V34a of the edge sensing unit 402 is increased by dividing the edge electrode 222 in this embodiment, and the output voltage V of the piezoelectric film 20 is increased. On the basis that the output capacitance C of the piezoelectric film 20 meets the requirement, a larger output voltage V can be obtained, and the sensitivity of the piezoelectric microphone 100 of the present application is further improved.

Referring to fig. 18, a center sensing unit 401 is divided into M center sub-sensing units 403, and an edge sensing unit 402 is divided into N edge sub-sensing units 404. In this embodiment, each of the central sub-sensing units 403 has two capacitance structures connected in parallel, and each of the edge sub-sensing units 404 has two capacitance structures connected in parallel. Then, all the center sub-sensing cells 403 and all the edge sub-sensing cells 404 are connected in series one by one to form an output voltage V and an output capacitance C of the piezoelectric film 20. It is understood that, similar to the calculation method of the above-described embodiment of fig. 14 to 17, the voltage V output by the piezoelectric film 20 in fig. 18 can be expressed as:

V-V12 a + V34 a-M V12+ N V34 formula (14);

the capacitance C output by the piezoelectric film 20 can be expressed as:

it can be seen that in the present embodiment, the output voltage V of the piezoelectric film 20 is further increased. The capacitance ratio of the edge sensing unit 402 and the central sensing unit 401 is used to match and select the values of M and N, so that the capacitance C34a of the edge sensing unit 402 is close to the capacitance C12a of the central sensing unit 401, i.e. the values of C34a/N2 and C12a/M2 are close to the same value. At this time, the output capacitance C of the piezoelectric film 20 is also large, which can meet the demand and reduce the signal-to-noise ratio. In the embodiment of fig. 18, the number M of the center sub-sensing units 403 is set to 2, and the number N of the edge sub-sensing units 404 is set to 6; in another embodiment, the number M of the center sub-sensing units 403 is set to 4, and the number N of the edge sub-sensing units 404 is set to 9.

For the connection schematic of the circuit in the embodiment of fig. 18, the schematic of fig. 19 to 22 can be referred to. In the schematic of fig. 19, M central sub-sensing units 403 are sequentially connected in series, and then connected in series with N edge sub-sensing units 404. Specifically, the center upper unit 2212a and the center lower unit 2211a of the front center sub-sensing unit 403 are conducted to lead out the first connection terminal 241, the center middle element 2213a of the center sub-sensing element 403 is connected to both the center upper element 2212a and the center lower element 2211a of the next center sub-sensing element 403, and after the M center sub-sensing elements 403 are sequentially connected, the center middle element 2213a of the center sub-sensing element 403 at the end is simultaneously connected to the edge upper element 2222a and the edge lower element 2221a of one edge sub-sensing element 404, the edge middle cell 2223a of the edge sub-sensing cell 404 is simultaneously connected to the edge upper cell 2222a and the edge lower cell 2221a of the next edge sensing cell 404, after the N edge sub-sensing units 404 are sequentially connected, the second connection terminal 242 is led out from the edge middle unit 2223a of the edge sub-sensing unit 404 at the end. As can be understood, the subsequent connection of the first connection terminal 241 and the second connection terminal 242 to the post-processing circuit 202 at the back end respectively forms the output voltage V and the output capacitance C of the piezoelectric microphone 100 of the present application.

In the illustration of fig. 20, the N edge sub-sensing units 404 are connected in series, and then connected in series with the M center sub-sensing units 403. Specifically, the edge sub-sensing unit 404 is used as a front-end output, the edge upper unit 2222a and the edge lower unit 2221a of the edge sub-sensing unit 404 are conducted and led out of the first connection terminal 241, and the edge middle unit 2223a of the edge sub-sensing unit 404 is simultaneously connected to the edge upper unit 2222a and the edge lower unit 2221a of the next edge sub-sensing unit 404. After the N edge sub-sensing units 404 are sequentially connected, the edge middle unit 2223a of the edge sub-sensing unit 404 at the end is simultaneously connected to the center upper unit 2212a and the center lower unit 2211a of one center sub-sensing unit 403, the center middle unit 2213a of the center sub-sensing unit 404 is connected to the center upper unit 2212a and the center lower unit 2211a of the next center sub-sensing unit 403, and after the M center sub-sensing units 403 are sequentially connected, the center middle unit 2213a of the center sub-sensing unit 403 at the end is connected to the second connection terminal 242. As can be understood, the subsequent connection of the first connection terminal 241 and the second connection terminal 242 to the post-processing circuit 202 at the back end respectively forms the output voltage V and the output capacitance C of the piezoelectric microphone 100 of the present application.

It should be noted that in the above embodiments, the connection between the sensing units is accomplished by the connection line 23, or the connection line 23 is matched with the via 25. Specifically, for the connection conduction between the cell 2213a in the center and the cell 2223a in the edge in the same plane layer, it can be realized only by the connection line 23; for connection conduction between, for example, the center cell 2213a and the edge-on cell 2222a or the edge-under cell 2221a in different plane layers, it is necessary to implement through the connection line 23 in cooperation with the via 25. Since the structure of the connection line 23 and the via 25 is a common structure in the art, the present application will not be described in detail herein.

In the schematic diagrams of fig. 21 and 22, the M central sub-sensing units 403 and the N edge sub-sensing units 404 are connected in series and crossed, so as to shorten the total length of the connection line 23 and simplify the internal structure of the piezoelectric film 20. Specifically, in the connection diagram of fig. 21, the expansion is based on M > N, that is, the number M of the center sub-sensing units 403 is greater than the number N of the edge sub-sensing units 404. At this time, the center sub-sensing unit 403 at the front end is also conducted through the center upper unit 2212a and the center lower unit 2211a and led out of the first connection terminal 241, then the center middle unit 2213a of the center sub-sensing unit 403 is conducted with the edge middle unit 2223a of one edge sub-sensing unit 404, the edge upper unit 2222a of the edge sub-sensing unit 404 is conducted with the center upper unit 2212a of the next center sub-sensing unit 403, and simultaneously the edge lower unit 2221a of the edge sub-sensing unit 404 is conducted with the center lower unit 2211a of the next center sub-sensing unit 403. The center cell 2213a of the next center sub-sensing cell 403 is electrically connected to the edge cell 2223a of the next edge sub-sensing cell 404. Thus, after the N central sub-sensing units 403 are sequentially connected in series with the N edge sub-sensing units 404, the remaining (M-N) central sub-sensing units 403 are sequentially connected in series, and a second connection terminal 241 is led out from the unit 2213a in the center of the last central sub-sensing unit 403 at the end. As can be understood, the subsequent connection of the first connection terminal 241 and the second connection terminal 242 to the post-processing circuit 202 at the back end respectively forms the output voltage V and the output capacitance C of the piezoelectric microphone 100 of the present application.

In the connection scheme of fig. 22, the expansion is based on M < N, that is, the number M of the center sub-sensing units 403 is smaller than the number N of the edge sub-sensing units 404. At this time, the edge sub-sensing unit 404 at the front end also leads out the first connection terminal 241 by conducting the edge upper cell 2222a and the edge lower cell 2221a, then the edge middle cell 2223a of the edge sub-sensing unit 404 is conducted with the center middle cell 2213a of one center sub-sensing unit 403, the center upper electrode 2212a of the center middle cell 403 is conducted with the edge upper cell 2222a of the next edge sub-sensing unit 404, and simultaneously the center lower electrode 2211a of the center cell 403 is conducted with the edge lower cell 2221a of the next edge sub-sensing unit 404. The cell 2223a in the edge of the next edge sub-sensing cell 404 is electrically connected to the cell 2213a in the center of the next center sub-sensing cell 403. Thus, after the M edge sub-sensing units 404 are sequentially connected in series with the M center sub-sensing units 403, the remaining (N-M) edge sub-sensing units 404 are sequentially connected in series, and a second connection terminal 241 is led out from the unit 2223a in the edge of the last edge sub-sensing unit 404 at the end. As can be understood, the subsequent connection of the first connection terminal 241 and the second connection terminal 242 to the post-processing circuit 202 at the back end respectively forms the output voltage V and the output capacitance C of the piezoelectric microphone 100 of the present application.

It should be noted that, in the embodiment of fig. 21, the edge upper unit 2222a and the edge lower unit 2221a of one edge sub-sensing unit 404 may be conducted and the first connection end 241 is led out, and then after the edge sub-sensing unit 404 is connected in series with one center sub-sensing unit 403, the center sub-sensing unit 403 is connected in series with the next edge sub-sensing unit 404 in a crossing manner; or in the embodiment of fig. 22, the central upper unit 2212a and the central lower unit 2211a of one central sub-sensing unit 403 are conducted and the first connection end 241 is led out, and then the cross-series connection of each central sub-sensing unit 403 and each edge sub-sensing unit 404 is realized, so that the same output voltage V and output capacitance C can be obtained.

In one embodiment, each edge sub-sensing unit 404, when connected to the center sub-sensing unit 403, is connected to the center sub-sensing unit 403 that is relatively close to the edge sub-sensing unit; accordingly, each center sub-sensing unit 403 is also connected to the edge sub-sensing unit 404, which is relatively close thereto. As shown in fig. 23, the number of the center sub-sensing elements 403 is 6, the number of the edge sub-sensing elements 404 is also 6, and the connection line 23 between the two connected center upper elements 2212a and edge upper elements 2222a extends along the radial direction of the circular center electrode 221 to the edge upper elements 2222a to form conduction. The distance of the six connection lines 23 is relatively short, and no crossing between the connection lines 23 is caused.

On the other hand, the shape of the center electrode 221 and the shape of the edge electrode 222 are not particularly limited, either, in the piezoelectric microphone 100 of the present application. The shape of the center electrode 221 may be axisymmetric (an ellipse as shown in fig. 24) or centrosymmetric (a regular polygon as shown in fig. 25); the shape of the edge electrode 222 may match the shape of the center electrode 221, and may be a circle-symmetrical shape (circular shape as shown in fig. 23) or an axis-symmetrical shape (elliptical ring shape as shown in fig. 24), and the edge electrode 222 may be configured to be different from the remaining shape of the center electrode 221 (circular shape as shown in fig. 25). The specific shape of the center electrode 221 and the edge electrode 222 can be arbitrarily adjusted according to the placement position of the piezoelectric microphone 100.

It can be understood that, corresponding to the embodiment shown in fig. 12 in which the center electrode 221 and the edge electrode 222 are connected in parallel, in the embodiment in which the center sensing unit 401 is divided into a plurality of center sub sensing units 403, the center sensing unit 401 composed of the plurality of center sub sensing units 403 may be connected in parallel with the edge sensing unit 402, and the sensing sensitivity of the piezoelectric microphone 100 may also be improved. At this time, the plurality of central sub-sensing units 403 may also be connected in series, or still connected in parallel; in the embodiment where the edge sensing unit 402 is divided into a plurality of edge sub-sensing units 404, the edge sensing unit 402 composed of a plurality of edge sub-sensing units 404 and the central sensing unit 401 may be connected in parallel to improve the sensing sensitivity of the piezoelectric microphone 100. It is understood that a plurality of edge sub-sensing units 404 may be connected in series or connected in parallel to form the edge sensing unit 402.

In the embodiment shown in fig. 12, in which the central electrode 221 and the edge electrode 222 are connected in parallel, the central sensing unit 401 and the edge sensing unit 402 may be further separated to form a central sensing unit 401 composed of a plurality of central sub-sensing units 403 and an edge sensing unit 402 composed of a plurality of edge sub-sensing units 404. The central sensing subunits 403 are connected in series or in parallel, and the edge sensing subunits 404 are connected in series or in parallel, and then the central sensing unit 401 and the edge sensing unit 402 are connected in parallel, which can also achieve the similar advantages as the above embodiments.

The above embodiments all belong to possible implementation manners of the piezoelectric microphone 100 of the present application, and details of the present application are not repeated herein.

Referring to fig. 26, in an embodiment, the piezoelectric microphone 100 of the present application further includes a vent slit 26 formed on the piezoelectric film 20. The vent slit 26 penetrates the piezoelectric film 20 in the thickness direction of the piezoelectric film 20, thereby communicating the cavity 11 and the space on the other side of the piezoelectric film 20 with respect to the substrate 10. When the piezoelectric microphone 100 of the present application is packaged on the substrate 201 of the audio pickup device 200, because the arrangement of the ventilation slit 26 can balance the air pressure on both sides of the piezoelectric film 20, the pressure difference between the inside of the relatively closed cavity 11 and the outside is avoided. Since the audible range of operation of the piezoelectric film 20 is usually between 20Hz and 20KHz, the thickness and diameter of the piezoelectric film are relatively small, which results in that the pressure difference between the upper and lower sides of the piezoelectric film 20 is relatively sensitive, and the arrangement of the ventilation slit 26 can protect the piezoelectric film 20 from being broken due to the pressure difference between the upper and lower sides when the piezoelectric film 20 vibrates.

The vent slits 26 are preferably provided on the piezoelectric layer 21 in the planar direction of the piezoelectric film 20. Specifically, the vent slit 26 includes a first end 261 and a second end 262 that are opposite in the longitudinal direction, the first end 261 of which is close to the geometric center of the piezoelectric film 20, and the second end 262 of which extends away from the geometric center with respect to the first end 261. In one embodiment, the extension of the vent slit 26 along its length is preferably disposed through the geometric center of the piezoelectric film 20, such as the vent slit 26 disposed along the radius of the circular piezoelectric film 20 in fig. 26.

In the illustration of fig. 27, the vent slits 26 may also extend into the edge electrode 222 and/or the center electrode 221. That is, the first end 261 of the ventilation slit 26 can extend into the central electrode 221 and form a partial division for the central electrode 221; the second end 262 may extend into the edge electrode 222 and form a partial partition of the edge electrode 222. It should be noted that the second end 262 may completely penetrate through the edge electrode 222, and at this time, for the edge electrode 222 that is broken into two parts by the ventilation slit 26, the two broken parts may be electrically connected by a wire, so as to ensure the charge collection of the edge electrode 222; or as shown in fig. 27, the vent slit 26 is directly used to divide the edge electrode 222 to form a plurality of edge-on cells 2222a, a plurality of edge-on cells 2223a, and a plurality of edge-off cells 2221 a. The first end 261 preferably does not extend to the geometric center of the piezoelectric film 20, i.e., the length of the single vent slit 26 in the extending direction is smaller than the distance between the geometric center of the piezoelectric film 20 and the edge in the extending direction. As reflected in the embodiment of fig. 27, it may be defined that the length of the vent slit 26 is less than the radius of the piezoelectric film 20. Such an arrangement can prevent the vent slit 26 from damaging the structural stability of the piezoelectric film 20 when passing through the center of the piezoelectric film 20, and enhance the shock resistance.

In one embodiment, the width of the vent slot 26 is defined to be less than or equal to 3 μm. Referring to the illustration of fig. 28, a circular hole 263 may be further disposed at an end position of the first end 261 and/or the second end 262. The diameter of the circular hole 263 is larger than the width of the ventilation slit 26, so as to avoid the stress concentration at the first end 261 or the second end 262, and improve the service life of the piezoelectric microphone 100.

In one embodiment, the number of the vent slits 26 is at least two, and the at least two vent slits are uniformly distributed along the circumferential direction of the piezoelectric film 20. The vent slit 26 may also act to relieve internal stress of the piezoelectric film 20 while equalizing the air pressure of the piezoelectric microphone 100. As mentioned above, the piezoelectric material of the piezoelectric layer 21 may include aluminum nitride (AlN), scandium-doped aluminum nitride (AlScN), lead zirconate titanate (PZT), or zinc oxide (ZnO), which are typically grown at a temperature higher than room temperature and placed in a room temperature environment after the growth is completed to further fabricate the assembly. Thermal stresses are generated due to the coefficient of thermal expansion of the material itself. The piezoelectric layer 21 made of piezoelectric material is provided with a layer structure of the electrode 22, which has a certain function of offsetting internal stress through self-deformation. However, for the residual stress that cannot be partially cancelled, the accumulation thereof in the piezoelectric film 20 may cause a local area of the piezoelectric film 20 to warp or the like. The residual stress may cause the piezoelectric layer 21 to break, causing the piezoelectric microphone 100 to fail. Or in an extreme environment such as dropping of the piezoelectric microphone 100 with an electronic device, the piezoelectric film 20 may be displaced greatly, which may also easily cause residual stress and damage to the piezoelectric layer 21.

Further, since the edge of the piezoelectric film 20 is fixedly connected to the annular substrate 10, only the middle region can move, and the residual stress is generally distributed in an irregular state in the middle region of the piezoelectric layer 21, which tends to cause the non-uniform resonant frequency of the piezoelectric film 20. The residual stress trend plot of fig. 29 was obtained from a limited simulation of piezoelectric film 20 in one possible embodiment, where a residual stress of 2.26KHz per 1MPa caused a shift in resonant frequency. After at least two ventilation slits 26 are arranged uniformly in the circumferential direction, the uniformly distributed ventilation slits 26 can release the residual stress in the piezoelectric film 20 and allow the piezoelectric layer 21 to improve the influence of the residual stress through certain deformation.

Fig. 30a and 30b respectively illustrate the stress simulation results of the piezoelectric film 20 according to an embodiment of the present application and the piezoelectric microphone structure according to the prior art. In the piezoelectric film 20 of one embodiment of the present application of fig. 30a, six equispaced vent slits 26 are provided. Under the same impact force, the maximum displacement of the surface of the piezoelectric film 20 is controlled within 3 μm. The maximum displacement of the piezoelectric microphone with the cantilever beam structure in the prior art reaches 18 mu m under the same impact force. The stress improvement effect of the vent slit 26 on the piezoelectric film 20 is significant.

The vent slit 26 may also enhance the low frequency response capability of the piezoelectric microphone 100. As shown in fig. 31, under the same impact force, the resonance frequency of the piezoelectric film 20 according to an embodiment of the present application after the vent slit 26 is provided is significantly better than that of the structure without the vent slit 26. In the signal-to-noise ratio simulation of the piezoelectric microphone 100 shown in fig. 32, in an embodiment of the present application, the piezoelectric microphone 100 is configured with the center electrode 221 and the edge electrode 222, and after the vent slit 26 is disposed, the signal-to-noise ratio of the piezoelectric microphone is improved by more than 2dB compared to that of the piezoelectric microphone with the existing cantilever beam structure under the same bandwidth condition.

Finally, the piezoelectric microphone 100 of the present application may be provided with an insulating layer 30 on the substrate 10 and a piezoelectric film 20 on the insulating layer 30, as shown in fig. 33. Wherein the piezoelectric film 20 comprises a piezoelectric layer 21 and an electrode 22. The piezoelectric layer 20 is provided with vent slits 26. The electrode 22 includes a central electrode 221 and an edge electrode 222, the central electrode 221 and the edge electrode 222 are spaced apart, the central electrode 221 is divided into a plurality of portions (two portions shown in fig. 33), and the edge electrode 222 is divided into a plurality of portions (6 portions shown in fig. 33). A connection line 23 may be further disposed between the central electrode 221 and the edge electrode 222 for electrically connecting the central electrode 221 and the edge electrode 222.

Fig. 34 and 35 illustrate another piezoelectric microphone 300 according to the present application, and the usage scenario of the piezoelectric microphone 100 is the same as that of the piezoelectric microphone 100 described above. Fig. 34 is a schematic structural diagram of another piezoelectric microphone 300 of the present application, and fig. 35 is a schematic cross-sectional view of the piezoelectric microphone 300 of the present application in the C-C direction. The piezoelectric microphone 300 also comprises a substrate 70, the substrate 10 also being annular and enclosing a cavity 11. The piezoelectric microphone 300 further includes a support layer 50 and a piezoelectric film layer 60. The support layer 50 and the piezoelectric film 60 are both planar structures and cover the substrate 10 to shield the cavity 11. Wherein the support layer 50 may be connected between the piezoelectric film 60 and the substrate 70, or as shown in fig. 36, the support layer 50 is disposed on a side of the piezoelectric film 60 facing away from the substrate 60. In the piezoelectric microphone 300 shown in fig. 36, the insulating layer 80 is further required to be disposed between the piezoelectric film layer 60 and the substrate 60.

The structure and material arrangement of the substrate 70 and the insulating layer 80 in the piezoelectric microphone 300 in this embodiment can be seen in the matching arrangement of the substrate 10 and the insulating layer 30 in the piezoelectric microphone 100 in each embodiment. The function of the piezoelectric film 60 in this embodiment is similar to that of the piezoelectric film 20 in the piezoelectric microphone 100, and is also used for collecting induced charges. The support layer 50 in this embodiment is used to provide support for the piezoelectric film 60, and adjust the position of the central plane B1' of the planar structure formed by the piezoelectric film 60 and the support layer 50 together, so that the piezoelectric film 60 can collect the induced charges and form the induction of the sound signal. The support layer 50 may be prepared using silicon dioxide (SiO 2).

The piezoelectric film layer 60 includes a piezoelectric layer 61 and a plurality of electrodes 62 disposed on the piezoelectric layer 61, wherein the plurality of electrodes 62 includes a center electrode 621 and an edge electrode 622. The center electrode 621 and the edge electrode 622 are also disposed at an interval in the planar direction of the piezoelectric film 60, wherein the center electrode 621 is located at the center of the piezoelectric film 60, and the edge electrode 622 surrounds the center electrode 621 and is located at the edge of the piezoelectric film 60.

In the thickness direction of the piezoelectric film layer 60, the piezoelectric layer 61 has a lower surface 611 near the cavity 11, and an upper surface 612 opposite to the lower surface 611. The central electrode 621 includes a central lower electrode 6211 proximate the lower surface 611 and a central upper electrode 6212 proximate the upper surface 612. The rim electrode 622 also includes a rim lower electrode 6221 proximate the lower surface 611 and a rim upper electrode 6222 proximate the upper surface 612. In one embodiment, the center upper electrode 6212 is disposed flush with the edge upper electrode 6222 and the center lower electrode 6211 is disposed flush with the edge lower electrode 6221. It is understood that the center lower electrode 6211 in the present embodiment may correspond to a first center electrode, the center upper electrode 6212 may correspond to a second center electrode, the edge lower electrode 6221 may correspond to a first edge electrode, and the edge upper electrode 6222 may correspond to a second edge electrode in the claims of the present application.

The center lower electrode 6211 and the center upper electrode 6212 form a center sensing unit 501 of a capacitive structure, and the edge lower electrode 6221 and the edge lower electrode 6222 form an edge sensing unit 502 of a capacitive structure. Because of the function of the support layer 50, the center plane B1' of the planar structure composed of the support layer 50 and the piezoelectric film layer 60 is shifted toward the support layer 50. Therefore, when the planar structure is vibrated by the sound signal, induced charges are generated on the central sensing unit 501 and the edge sensing unit 502. At this time, the central sensing unit 501 and the edge sensing unit 502 are connected in series and then connected to the back-end post-processing circuit 202, so that the functions of collecting charges and converting electrical signals can be realized.

It can be understood that, because the stress generated in the central region and the stress generated in the edge region are opposite in direction during the vibration of the piezoelectric film layer 60, the voltage V1 'of the central sensing unit 501 is also opposite to the voltage V2' of the edge sensing unit 502. In the process of connecting the central inductive unit 501 and the second inductive voltage 502 in series, see the schematic of fig. 37:

the first connection end 641 is led out from the center upper electrode 6212 of the center sensing unit 501, the center lower electrode 6211 of the center sensing unit 501 is connected to the edge lower electrode 6221 of the edge sensing unit 502, and finally the second connection end 642 is led out from the edge upper electrode 6222 of the edge sensing unit 502. The first connection end 641 and the second connection end 642 are respectively connected to the back-end post-processing circuit 202, so as to obtain the output voltage V 'and the output capacitance C' of the piezoelectric microphone 300.

Of course, the first connection end 641 and the second connection end 642 can also be led out from the center lower electrode 6211 and the edge lower electrode 6221, respectively, and can also communicate the center upper electrode 6212 with the edge upper electrode 6222, respectively, to achieve the same effect. The piezoelectric film layer 60 is also provided with a connecting wire 63 (see fig. 42), and further a via hole (not shown) can be provided to achieve the internal connection conduction of the electrode 62 and the leading-out function of the connecting end. It is understood that the via hole may be led out from the piezoelectric film layer 60 side or from the support layer 50 side.

This application piezoelectric microphone 300 is because central electrode 621 and marginal electrode 622 cover the central region and the marginal area of piezoelectric layer 61 respectively for electrode 62 can produce the effective area that stress is concentrated relatively at piezoelectric layer 61 and collect induced charge, and through the series connection of central induction element 501 and marginal induction element 502, has promoted output voltage V' on the basis of satisfying the electric charge demand, and then has reached the effect that promotes piezoelectric microphone 300 sensitivity.

Referring to the schematic of fig. 38, in one embodiment, the center electrode 621 may also be cut to form a center sub-sensing unit 503 composed of a plurality of center upper units 6212a and a plurality of center lower units 6211 a. A plurality of central sub-sensing units 503 constitute a central sensing unit 501. At this time, a plurality of center sub-sensing units 503 are also connected in series, and then are connected in series with the edge sensing unit 502, so as to achieve a larger output voltage V'. Specific connection schematic can be seen in the schematic of fig. 39. It is understood that the center lower unit 6211a in the present embodiment may correspond to a first center sub-electrode in claims, and the center upper unit 6212a may correspond to a second center sub-electrode.

In another embodiment, referring to fig. 40, the edge electrode 622 is cut to form the edge sub-sensing unit 504 composed of a plurality of upper edge units 6222a and a plurality of lower edge units 6221 a. The plurality of edge sub-sensing units 504 form an edge sensing unit 502. At this time, the edge sub-sensing units 504 are also connected in series and then connected in series with the central sensing unit 501, so as to achieve the effect of a larger output voltage V. For a specific connection, see the schematic of fig. 41. It is to be understood that the lower edge unit 6221a in the present embodiment may correspond to a first edge sub-electrode in the claims, and the upper edge unit 6212a may correspond to a second edge sub-electrode.

In another embodiment, referring to fig. 42, the center sensing unit 501 is divided into M center sub-sensing units 503, and the edge sensing unit 502 is divided into N edge sub-sensing units 504. At this time, as shown in fig. 43, after each center sub-sensing unit 503 and each edge sub-sensing unit 504 are connected in series in a crossing manner, the remaining center sub-sensing units 503 or the remaining edge sub-sensing units 504 are connected in series to obtain a larger output voltage V; as shown in fig. 44, after the M central sub-sensing units 503 are sequentially connected in series, the N edge sub-sensing units 504 are sequentially connected in series, which can achieve the effect similar to the embodiment of fig. 41.

In one embodiment, when the distance between the center of the piezoelectric layer 61 and the edge of any direction is L ', the first dimension L1' of the center electrode 621 in the direction also needs to satisfy the following condition: l ' is 50% or more and L1 ' or more and L ' is 5% or more. Preferably, L ' 40% ≧ L1 ' ≧ L ' 20%; in this direction, the second dimension L2 ' of the edge electrode 622 from the outer edge is also equal to or less than L ' 50% and equal to or greater than L ' 5%. Preferably, L ' 30% ≧ L2 ' ≧ L ' 10% can be defined.

In one embodiment, the shape of the center electrode 621 and/or the edge electrode 622 may also be axisymmetric or centrosymmetric, wherein the shape of the center electrode 621 may be the same as or different from that of the edge electrode 622.

Referring to the embodiment of fig. 45, in the piezoelectric microphone 300 of the present application, a vent slit 66 may also be provided to communicate the cavity 11 with the space on the other side of the piezoelectric film layer 60 with respect to the substrate 70. Because of the arrangement of the support layer 50, the vent slits 66 need to penetrate both the piezoelectric film layer 60 and the support layer 50 in the thickness direction of the piezoelectric film layer 60. The ventilation slit 66 can also achieve the effect of balancing the pressure difference between the inside and the outside of the inner cavity 11, and the structural stability of the piezoelectric film 60 is improved.

Further, it is preferable that at least two vent slits 66 are provided, and the at least two vent slits 66 are circumferentially distributed on the piezoelectric layer 61 in the planar direction of the piezoelectric film layer 60. The vent slot 66 also includes a first end 661 along its length that is proximate to the geometric center of the piezoelectric film layer 60 and a second end 662 that extends away from the geometric center of the piezoelectric film layer 60 relative to the first end 661. In one embodiment, the extending direction of the second end 662 to the first end 661 is disposed through the geometric center of the piezoelectric film layer 60.

In one embodiment, the first end 661 may extend into the central electrode 621, but the first end 661 is not suitable to extend to the geometric center of the piezoelectric film layer 60; the second end 662 may also extend into the edge electrode 622, and the second end 662 may also extend directly into the outer edge of the edge electrode 622.

In one embodiment, the width of the vent slot 66 is less than or equal to 3 μm. In one embodiment, a circular hole (not shown) may be formed at the first end 661 and/or the second end 662. The diameter of the circular hole is larger than the width of the vent slot 66 to avoid stress concentration at the first end 661 or the second end 662.

The above description is only for the specific embodiment of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily think of the changes or substitutions, such as the reduction or addition of structural elements, the change of shape of structural elements, etc., within the technical scope of the present application, and shall be covered by the scope of the present application; the embodiments and features of the embodiments of the present application may be combined with each other without conflict. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. The piezoelectric microphone is characterized by comprising a substrate and a piezoelectric film, wherein the substrate is annular and encloses an inner cavity, and the piezoelectric film is fixed on one side of the substrate to shield the inner cavity;

2. The piezoelectric microphone of claim 1, wherein a geometric center of the piezoelectric layer has a first distance L from an edge of the piezoelectric layer, a geometric center of the center electrode has a first dimension L1 from an edge of the center electrode, and the first dimension L1 satisfies a condition: l50% or more and L1 or more and L5% or more.

3. The piezoelectric microphone according to claim 1 or 2, wherein a distance between the first center electrode and the third center electrode is equal to a distance between the second center electrode and the third center electrode in a thickness direction of the piezoelectric film.

4. The piezoelectric microphone according to any one of claims 1 to 3, wherein, in any one direction of the plane of the piezoelectric film, the geometric center of the piezoelectric layer has a first distance L from the edge of the piezoelectric layer, the inner edge of the edge electrode has a second dimension L2 from the outer edge of the edge electrode, and the second dimension L2 satisfies the condition: l50% or more and L2 or more and L5% or more.

5. The piezoelectric microphone according to any one of claims 1 to 4, wherein the first center electrode is flush with the first edge electrode, the second center electrode is flush with the second edge electrode, and the third center electrode is flush with the third edge electrode in a thickness direction of the piezoelectric film.

6. The piezoelectric microphone according to any one of claims 1 to 5, wherein the first center electrode is divided into at least two first center sub-electrodes, the second center electrode is divided into at least two second center sub-electrodes, the third center electrode is divided into at least two third center sub-electrodes, and the number of the first center sub-electrodes, the second center sub-electrodes, and the third center sub-electrodes is equal;

7. The piezoelectric microphone according to claim 6, wherein a projection of one of the first center sub-electrodes on the second center sub-electrode corresponding to its position coincides with an outer shape of the second center sub-electrode, and a projection of one of the third center sub-electrodes on the second center sub-electrode corresponding to its position also coincides with an outer shape of the second center sub-electrode in a thickness direction of the piezoelectric film.

8. The piezoelectric microphone according to claim 6 or 7, wherein the at least two first center sub-electrodes are identical in shape and area.

9. The piezoelectric microphone according to any one of claims 1 to 8, wherein the first edge electrode is divided into at least two first edge sub-electrodes, the second edge electrode is divided into at least two second edge sub-electrodes, the third edge electrode is divided into at least two third edge sub-electrodes, and the number of the first edge sub-electrodes, the second edge sub-electrodes, and the third edge sub-electrodes is equal;

10. The piezoelectric microphone according to claim 9, wherein a projection of one of the first edge sub-electrodes on the second edge sub-electrode corresponding to its position coincides with an outer shape of the second edge sub-electrode, and a projection of one of the third edge sub-electrodes on the second edge sub-electrode corresponding to its position also coincides with an outer shape of the second edge sub-electrode in a thickness direction of the piezoelectric film.

11. The piezoelectric microphone according to claim 9 or 10, wherein the at least two first edge sub-electrodes are identical in shape and area.

12. The piezoelectric microphone according to any one of claims 6 to 8, wherein the central sub-sensing unit and the edge sensing unit are electrically connected through a connection line.

13. The piezoelectric microphone according to any one of claims 1 to 12, wherein a vent slit is further provided in the piezoelectric layer, the vent slit penetrating the piezoelectric film in a thickness direction of the piezoelectric film.

14. The piezoelectric microphone of claim 13, wherein the vent slit includes a first end and a second end opposite to each other along a length direction thereof, and an extension line from the second end to the first end passes through a geometric center of the piezoelectric film.

15. The piezoelectric microphone according to claim 13, wherein the piezoelectric film includes a plurality of the vent slits, the plurality of vent slits being evenly distributed along a circumferential direction of the piezoelectric film.

16. The piezoelectric microphone of claim 13, wherein the vent slit has a width of less than or equal to 3 μ ι η.

17. The piezoelectric microphone according to any one of claims 1 to 16, wherein the central sensing unit is connected in series with the edge sensing unit to output a sensing signal of the piezoelectric microphone.

18. The piezoelectric microphone according to any one of claims 1 to 17, wherein the substrate is made of a silicon wafer as a main material, an insulating member is further provided between the substrate and the piezoelectric film, the insulating member has a ring shape, and the shape of the insulating member matches the shape of the substrate.

19. The piezoelectric microphone is characterized by comprising a base body, a piezoelectric film and a supporting layer, wherein the base body is annular and encloses an inner cavity, the piezoelectric film and the supporting layer are arranged in a laminated mode, and the piezoelectric film and the supporting layer are fixed on one side of the base body to shield the inner cavity;

20. The piezoelectric microphone of claim 19, wherein the geometric center of the piezoelectric layer is a first distance L ' from the edge of the piezoelectric layer, the geometric center of the center electrode is a first dimension L1 ' from the edge of the center electrode, and the first dimension L1 ' satisfies the condition: l50% or more and L1' or more and L5%; and/or

21. The piezoelectric microphone according to claim 19 or 20, wherein the first center electrode is flush with the first edge electrode and the second center electrode is flush with the second edge electrode in a thickness direction of the piezoelectric film.

22. The piezoelectric microphone according to any one of claims 19 to 21, wherein the first center electrode is divided into at least two first center sub-electrodes, the second center electrode is also divided into a plurality of second center sub-electrodes, and the number of the first center sub-electrodes is equal to the number of the second center sub-electrodes;

23. The piezoelectric microphone according to claim 22, wherein a projection of one of the first center sub-electrodes on the second center sub-electrode corresponding to its position in a thickness direction of the piezoelectric film coincides with an outer shape of the second center sub-electrode; and/or

The projection of one first edge sub-electrode on the second edge sub-electrode corresponding to the position of the first edge sub-electrode is coincident with the outline of the second edge sub-electrode.

24. The piezoelectric microphone according to any one of claims 19 to 23, wherein the piezoelectric layer is further provided with a vent slit that penetrates both the piezoelectric film and the support layer in a thickness direction of the piezoelectric film.

25. The piezoelectric microphone according to claim 24, wherein the piezoelectric film includes a plurality of the vent slits, the plurality of vent slits being evenly distributed along a circumferential direction of the piezoelectric film.

26. The piezoelectric microphone according to any one of claims 19 to 25, wherein the support layer is located between the piezoelectric film and the base, and a main material of the support layer is an insulating material.

27. The piezoelectric microphone according to any one of claims 19 to 25, wherein the piezoelectric film is located between the support layer and the base body, the base body is made of a silicon wafer, an insulating member is further provided between the base body and the piezoelectric film, the insulating member has a ring shape, and the shape of the insulating member matches the shape of the base body.

28. An electronic device comprising an audio pickup device comprising a substrate, a post-processing circuit, and the piezoelectric microphone of any one of claims 1 to 27;