Piezoelectric Microphone and Electronic Device

Abstract

The present application discloses a piezoelectric microphone and an electronic device. The piezoelectric microphone includes a substrate and a piezoelectric film. The substrate encloses an inner cavity, and the piezoelectric film is fixed to one side of the substrate to shield the inner cavity. The piezoelectric film includes a piezoelectric layer, a central electrode, and an edge electrode. The central electrode includes a first central electrode, a second central electrode, and a third central electrode that are spaced apart from each other. The three form two capacitive structures, namely a first capacitor and a second capacitor, and then are connected in parallel to form a central sensing unit. The edge electrode also includes a first edge electrode, a second edge electrode, and a third edge electrode that are spaced apart from each other. The three also form two capacitive structures, namely a third capacitor and a fourth capacitor, and then are connected in parallel to form an edge sensing unit. The central sensing unit is electrically connected to the edge sensing unit to output the sensing signal of the piezoelectric microphone. The piezoelectric microphone of the present application has higher sensitivity due to the connection settings between the capacitive structures, thereby improving the sound collection effect of the electronic device of the present application.

Description

Technical Field

[0001] This application relates to the field of electronic technologies, and in particular, to a piezoelectric microphone and an electronic device. Background Art

[0002] In recent years, due to advantages such as small size, low power consumption, and the ability to complete surface mounting processes, micro-electro-mechanical system (MEMS) microphones have quickly replaced traditional electret capacitance microphones (ECMs) and become the mainstream audio pickup devices in electronic equipment. MEMS microphones mainly include two types: capacitive and piezoelectric. Among them, piezoelectric MEMS microphones have greater application prospects due to their outstanding low-power consumption characteristics and advantages such as waterproof and dustproof.

[0003] A piezoelectric microphone utilizes a piezoelectric film layer to vibrate under the action of a sound signal and completes the conversion of the sound signal into an electrical signal by collecting the charges induced by the vibration. The region that can effectively convert the collected charges into an electrical signal is the effective region. However, during the vibration process of the piezoelectric film layer, the stresses formed in each region are different. In some regions, the capacitance is too large and the voltage is too small, while in other regions, it is the opposite, resulting in a limited area of the effective region in the piezoelectric film layer, thereby restricting the sensitivity of the piezoelectric microphone. Summary of the Invention

[0004] The purpose of this application is to provide a piezoelectric microphone and an electronic device including the piezoelectric microphone. The piezoelectric microphone improves the sensitivity of the piezoelectric microphone by setting an electrode structure on the piezoelectric material and optimizing the connection method of the electrode structure.

[0005] In a first aspect, this application relates to a piezoelectric microphone, including a substrate and a piezoelectric film. The substrate is annular and encloses an inner cavity, and the piezoelectric film is fixed to one side of the substrate to shield the inner cavity;

[0006] The piezoelectric film includes 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 at the periphery of the piezoelectric layer;

[0007] In the thickness direction of the piezoelectric film, the center electrode includes a first center electrode, a second center electrode, and a third center electrode that are spaced apart from each other. The third center electrode is located between the first center electrode and the second center electrode. The first center electrode and the third center electrode form a first capacitor, the second center electrode and the third center electrode form a second capacitor, and the first capacitor and the second capacitor are connected in parallel to form a center induction unit;

[0008] The edge electrodes include a first edge electrode, a second edge electrode, and a third edge electrode that are spaced apart from each other. The third edge electrode is located 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.

[0009] The central sensing unit is electrically connected to the edge sensing unit to output the sensing signal of the piezoelectric microphone.

[0010] In the piezoelectric microphone of the present application, due to the shielding of the inner cavity formed by the piezoelectric film on the substrate, the sound signal transmitted from the inner cavity can cause the vibration of the piezoelectric film. Then, the central electrode and the edge electrode provided in the piezoelectric film are used to collect the charges generated by the vibration of the piezoelectric film. Among them, through the parallel connection of the first capacitor and the second capacitor formed by the central electrode, the capacitance value sensed by the central electrode is increased; through the parallel connection of the third capacitor and the fourth capacitor formed by the edge electrode, the capacitance value sensed by the edge electrode is increased. Finally, the central sensing unit and the edge sensing unit are electrically connected, and the induced voltage and / or the induced capacitance obtained can be correspondingly increased. Thereby, the overall sensing sensitivity of the piezoelectric microphone of the present application is improved.

[0011] In addition, based on the fact that the stress directions in the central region and the edge region of the piezoelectric film are opposite, the separately arranged central electrode and edge electrode can respectively collect the induced charges in the above two regions. And for the phenomenon that the charge polarities are opposite in the thickness direction of the piezoelectric film, the central electrode of the present application respectively collects the charges through the first capacitor and the second capacitor, and the edge electrode of the present application respectively collects the charges through the third capacitor and the fourth capacitor, which also achieves the effect of effectively collecting the charges.

[0012] In a possible embodiment, in the thickness direction of the piezoelectric film, the projection of the first central electrode on the second central electrode coincides with the outer shape of the second central electrode, and the projection of the third central electrode on the second central electrode also coincides with the outer shape of the second central electrode.

[0013] In this implementation manner, the areas and shapes of the first central electrode, the second central electrode, and the third central electrode are set to be the same, and the positions of the three are aligned with each other, which is beneficial to controlling the area ratio of the central electrode on the piezoelectric film and avoiding useless areas with low charge collection efficiency in the central electrode.

[0014] A possible embodiment is that in any direction on the plane of the piezoelectric film, the geometric center of the piezoelectric layer is at a first distance L from the edge of the piezoelectric layer, the geometric center of the central electrode is at a first dimension L1 from the edge of the central electrode, and the first dimension L1 satisfies the condition: 50%×L ≥ L1 ≥ 5%×L. Preferably, it can also be controlled that 40%×L ≥ L1 ≥ 20%×L.

[0015] In this implementation, for the case where the area where charges can be effectively collected is limited when the piezoelectric film vibrates under a sound signal, restricting the area ratio of the central electrode on the piezoelectric film can ensure that the effective area of the central electrode corresponds to the piezoelectric film, thus ensuring the effective collection of charges.

[0016] A possible embodiment is that in the thickness direction of the piezoelectric film, 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.

[0017] 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. Therefore, 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.

[0018] A possible embodiment is that in the thickness direction of the piezoelectric film, the projection of the first edge electrode on the second edge electrode coincides with the outer shape of the second edge electrode, and the projection of the third edge electrode on the second edge electrode also coincides with the outer shape of the second edge electrode.

[0019] In this implementation, in a manner similar to that of the central electrode, the areas and shapes of the first edge electrode, the second edge electrode, and the third edge electrode are all the same, and their positions are aligned with each other, which is beneficial to controlling the area ratio of the edge electrodes on the piezoelectric film and avoiding useless areas with low charge collection efficiency in the edge electrodes.

[0020] A possible embodiment is that in any direction on the plane of the piezoelectric film, the geometric center of the piezoelectric layer is at a first distance L from the edge of the piezoelectric layer, the inner edge of the edge electrode is at a second dimension L2 from the outer edge of the edge electrode, and the second dimension L2 satisfies the condition: 50%×L ≥ L2 ≥ 5%×L. Preferably, it can also be controlled that 30%×L ≥ L2 ≥ 10%×L.

[0021] In this implementation manner, for the case where the area where charges can be effectively collected is limited when the piezoelectric film vibrates under a sound signal, a certain limit is also imposed on the area ratio of the edge electrode on the piezoelectric film, so as to ensure that the edge electrode is set corresponding to the effective area of the piezoelectric film and ensure the effective collection of charges.

[0022] In a possible embodiment, in the thickness direction of the piezoelectric film, 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.

[0023] In this implementation manner, 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. Therefore, 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 can be controlled to be equal to the capacitance value of the fourth capacitor.

[0024] In a possible embodiment, in the thickness direction of the piezoelectric film, the first central electrode is flush with the first edge electrode, the second central electrode is flush with the second edge electrode, and the third central electrode is flush with the third edge electrode.

[0025] In this implementation manner, since each layer of electrode structure in the piezoelectric film is formed by a patterning process, setting the first central electrode to be flush with the first edge electrode can complete the patterning of the first edge electrode while patterning the first central electrode. Similarly, setting the second central electrode to be flush with the second edge electrode and setting the third central electrode to be flush with the third edge electrode can also form two electrode structures simultaneously in one patterning process, improving the processability of the piezoelectric microphone.

[0026] In a 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, and the third central electrode is divided into at least two third central sub - electrodes, and the number of the first central sub - electrodes, the second central sub - electrodes, and the third central sub - electrodes is equal;

[0027] One first central sub - electrode and one third central sub - electrode form a first sub - capacitor, one second central sub - electrode and one third central sub - electrode form a second sub - capacitor, and one first sub - capacitor and one second sub - capacitor are connected in parallel to form a central sub - sensing unit;

[0028] A plurality of the central sub - sensing units are connected in series to form the central sensing unit.

[0029] In this implementation manner, dividing the central sensing unit into a plurality of central sub - sensing units can further increase the voltage sensed by the central electrode on the premise of ensuring that the capacitance value sensed by the central electrode does not decrease.

[0030] In a possible embodiment, in the thickness direction of the piezoelectric film, the projection of one of the first central sub - electrodes on the second central sub - electrode corresponding to its position coincides with the outer shape of the second central sub - electrode, and the projection of one of the third central sub - electrodes on the second central sub - electrode corresponding to its position also coincides with the outer shape of the second central sub - electrode.

[0031] In this implementation manner, in the orientation of each of the first central sub - electrodes, the area and shape of the first central sub - electrode and the second and third central sub - electrodes corresponding to its position are the same, which is beneficial to controlling the area ratio of the central sub - electrode on the piezoelectric film and avoiding useless areas with low charge collection efficiency.

[0032] In a possible embodiment, the shapes and areas of the at least two first central sub - electrodes are the same, the shapes and areas of the at least two second central sub - electrodes are the same, and the shapes and areas of the at least two third central sub - electrodes are the same.

[0033] In this implementation manner, controlling the first central electrode to be evenly divided into a plurality of first central sub - electrodes with the same area, and at the same time controlling the second central electrode and the third central electrode to be evenly divided, is beneficial to forming a plurality of central sub - sensing units with the same voltage and capacitance value, and further increasing the voltage and capacitance sensed by the central sensing unit formed after their series connection.

[0034] In a 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 second edge sub - electrodes, and the third edge sub - electrodes is equal;

[0035] 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 a third sub - capacitor and a fourth sub - capacitor are connected in parallel to form an edge sub - sensing unit;

[0036] A plurality of the edge sub - sensing units are connected in series to form the edge sensing unit.

[0037] In this implementation manner, dividing the edge sensing unit into multiple edge sub-sensing units can further increase the voltage sensed by the edge electrode on the premise of ensuring that the capacitance value sensed by the edge electrode does not decrease.

[0038] In a possible embodiment, in the thickness direction of the piezoelectric film, the projection of one of the first edge sub-electrodes on the corresponding second edge sub-electrode coincides with the outer shape of the second edge sub-electrode, and the projection of one of the third edge sub-electrodes on the corresponding second edge sub-electrode also coincides with the outer shape of the second edge sub-electrode.

[0039] In this implementation manner, in the orientation of each of the first edge sub-electrodes, the areas and shapes of the first edge sub-electrode and the corresponding second and third edge sub-electrodes are the same, which is beneficial to controlling the area ratio of the edge sub-electrode on the piezoelectric film and avoiding useless areas with low charge collection efficiency.

[0040] In a possible embodiment, the shapes and areas of the at least two first edge sub-electrodes are the same, the shapes and areas of the at least two second edge sub-electrodes are the same, and the shapes and areas of the at least two third edge sub-electrodes are the same.

[0041] In this implementation manner, controlling the first edge electrode to be evenly divided into multiple first edge sub-electrodes with the same area, and at the same time controlling the second edge electrode and the third edge electrode to be evenly divided, is beneficial to forming multiple edge sub-sensing units with the same voltage and capacitance value, and further increasing the voltage and capacitance sensed by the edge sensing unit formed after their series connection.

[0042] In a possible embodiment, the central sub-sensing unit and the edge sensing unit are electrically connected through a connecting wire.

[0043] In this implementation manner, after the central sub-sensing unit is divided into multiple central sub-sensing units, the connection between the central sub-sensing unit and the edge sensing unit can also be realized through a connecting wire.

[0044] In a possible embodiment, an air vent slit is further provided on the piezoelectric layer, and the air vent slit penetrates through the piezoelectric film in the thickness direction of the piezoelectric film.

[0045] In this implementation manner, the setting of the air vent slit can balance the air pressure on both sides of the piezoelectric film and avoid forming a pressure difference between the relatively closed inner cavity and the outside. Because the thickness-to-diameter ratio is relatively small, the piezoelectric film is relatively sensitive to the pressure difference between the upper and lower sides. The setting of the air vent slit can protect the piezoelectric film from cracking due to the pressure difference between the upper and lower sides during vibration.

[0046] A possible embodiment, the ventilation slit includes opposite first and second ends along its own length direction, and an extension line from the second end to the first end passes through the geometric center of the piezoelectric film.

[0047] In this implementation, setting the extension line of the ventilation slit to pass through the geometric center of the piezoelectric film can better control the resonant frequency of the piezoelectric film and obtain more balanced induced charges in the plane direction of the piezoelectric film.

[0048] A possible embodiment, the first end extends into the center electrode, and / or

[0049] the second end extends into the edge electrode.

[0050] In this implementation, the ventilation slit extending into the center electrode and / or the edge electrode can also partially release the internal stress of the center electrode and / or the edge electrode, and improve the structural stability of the center electrode and / or the edge electrode.

[0051] A possible embodiment, the second end of the ventilation slit completely penetrates the edge electrode.

[0052] In this implementation, by providing the penetration of the edge electrode by the ventilation slit, the edge electrode can be simultaneously segmented. That is, the edge electrode is segmented into multiple edge sub-induction units by using the structure of the ventilation slit, and the manufacturing process of the piezoelectric microphone can be integrated.

[0053] A possible embodiment, the first end and / or the second end is also provided in the shape of a circular hole, and the diameter of the circular hole is greater than the width of the ventilation slit.

[0054] In this implementation, the provision of the circular hole can eliminate the stress concentration phenomenon at the first end and / or the second end, and avoid the generation of cracks at the first end and / or the second end due to stress concentration.

[0055] A possible embodiment, the piezoelectric film includes a plurality of the ventilation slits, and the plurality of ventilation slits are evenly distributed along the circumferential direction of the piezoelectric film.

[0056] In this implementation, the plurality of ventilation slits are evenly distributed along the circumferential direction of the piezoelectric film, that is, the plurality of ventilation slits are distributed on the piezoelectric film in a centrally symmetric manner, which is more conducive to controlling the resonant frequency of the piezoelectric film, and further making the charges collected in each region of the piezoelectric film more balanced.

[0057] A possible embodiment, the width of the ventilation slit is less than or equal to 3 μm.

[0058] In this implementation, the width setting of the ventilation slit can control the influence of the ventilation slit on the resonance frequency of the piezoelectric film, ensuring that the frequency response range of the piezoelectric film is within a preset range.

[0059] In a possible embodiment, the total thickness of the piezoelectric film is between 0.3 μm and 2 μm;

[0060] The thicknesses of 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 are between 0.01 μm and 0.15 μm.

[0061] In this implementation, setting the thickness of the piezoelectric film and the thicknesses of 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 can ensure the thickness ratios of the respective electrodes to the piezoelectric film, thereby ensuring the vibration sensitivity of the piezoelectric film on the premise of using the respective electrodes to improve the structural stability of the piezoelectric film.

[0062] In a possible embodiment, the central sensing unit and the edge sensing unit are connected in series to output the sensing signal of the piezoelectric microphone.

[0063] In this implementation, since the central sensing unit increases the capacitance value it senses through the parallel connection of the first capacitor and the second capacitor, and the edge sensing unit also increases the capacitance value it senses through the parallel connection of the third capacitor and the fourth capacitor, after the central sensing unit and the edge sensing unit are connected in series, the voltage value can also be increased, achieving the effect of simultaneously increasing the sensing capacitance and the sensing voltage.

[0064] In a possible embodiment, the main material of the substrate is a silicon wafer, and an insulating member is further provided 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.

[0065] In this implementation, when the main 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 provided between the substrate and the piezoelectric film to achieve the insulation of the piezoelectric film relative to the substrate.

[0066] In a possible embodiment, the substrate is made of an insulating material.

[0067] In this implementation, the insulating property of the substrate itself blocks the electrical conduction between the substrate and the piezoelectric film, that is, the substrate itself can serve as an insulating structure to achieve the insulation between the piezoelectric film and the substrate.

[0068] Second aspect, an embodiment of the present application provides another piezoelectric microphone, which includes a substrate, a piezoelectric film, and a support layer. The substrate is annular and defines an inner cavity. The piezoelectric film and the support layer are stacked, and both the piezoelectric film and the support layer are fixed to one side of the substrate to shield the inner cavity;

[0069] The piezoelectric film includes a piezoelectric layer, a central electrode, and an edge electrode. The piezoelectric layer is laid in the planar direction of the piezoelectric film. The central electrode is fixed in the middle of the piezoelectric layer, and the edge electrode is fixed at the periphery of the piezoelectric layer;

[0070] In the thickness direction of the piezoelectric film, the central electrode includes a first central electrode and a second central electrode that are spaced apart from each other. The first central electrode and the second central electrode form a central induction unit of a capacitive structure;

[0071] The edge electrode includes a first edge electrode and a second edge electrode that are spaced apart from each other. The first edge electrode and the second edge electrode form an edge induction unit of a capacitive structure;

[0072] The central induction unit and the edge induction unit are connected in series to output an induction signal of the piezoelectric microphone.

[0073] In this implementation, through the shielding of the inner cavity formed by the piezoelectric film and the support layer on the substrate, the sound signal incoming from the inner cavity can cause the vibration of the piezoelectric film and the support layer. At the same time, 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 the charge generated by the excitation of the sound signal can be collected by the piezoelectric film. And through the central induction unit of the capacitive structure formed by the central electrode and the edge induction unit of the capacitive structure formed by the edge electrode, the charge can be collected respectively in the regions where the charge generated by the piezoelectric film is relatively high. The piezoelectric microphone of the present application can increase the voltage value and capacitance value collected by it, thereby improving the overall induction sensitivity of the piezoelectric microphone of the present application.

[0074] In a possible embodiment, in the thickness direction of the piezoelectric film, the projection of the first central electrode on the second central electrode coincides with the outer shape of the second central electrode; and / or

[0075] The projection of the first edge electrode on the second edge electrode coincides with the outer shape of the second edge electrode.

[0076] In this implementation manner, setting the areas and shapes of the first central electrode and the second central electrode to be the same, and setting the areas and shapes of the first edge electrode and the second edge electrode to be the same is beneficial to controlling the area ratio of the central electrode and / or the edge electrode on the piezoelectric film, and avoiding useless areas with low charge collection efficiency in the central electrode and / or the edge electrode.

[0077] In a possible embodiment, in any direction on the plane of the piezoelectric film, the geometric center of the piezoelectric layer is at a first distance L' from the edge of the piezoelectric layer, the geometric center of the central electrode is at a first dimension L1' from the edge of the central electrode, and the first dimension L1' satisfies the condition: L' * 50% ≥ L1' ≥ L' * 5%; and / or

[0078] The inner edge of the edge electrode is at a second dimension L2' from the outer edge of the edge electrode, and the second dimension L2' satisfies the condition: L' * 50% ≥ L2' ≥ L' * 5%.

[0079] In this implementation manner, for the case where the area of the piezoelectric film that can effectively collect charges is limited when the piezoelectric film vibrates under a sound signal, imposing certain restrictions on the area ratio of the central electrode and / or the edge electrode on the piezoelectric film can ensure that the central electrode and / or the edge electrode correspondingly cover the effective area of the piezoelectric film to ensure effective charge collection.

[0080] In a possible embodiment, in the thickness direction of the piezoelectric film, the first central electrode is flush with the first edge electrode, and the second central electrode is flush with the second edge electrode.

[0081] In this implementation manner, since each layer of electrode structure in the piezoelectric film is formed by a patterning process, setting the first central electrode to be flush with the first edge electrode can complete the patterning of the first edge electrode simultaneously when patterning the first central electrode. Similarly, setting the second central electrode to be flush with the second edge electrode can also form two electrode structures simultaneously in a single patterning process, improving the processability of the piezoelectric microphone.

[0082] In a possible embodiment, the first central electrode is divided into at least two first central sub - electrodes, and the second central electrode is also divided into multiple second central sub - electrodes, and the number of the first central sub - electrodes is equal to the number of the second central sub - electrodes;

[0083] One of the first central sub - electrodes and one of the second central sub - electrodes form a central sub - induction unit of a capacitive structure;

[0084] A plurality of the central sub-sensing units are connected in series to form the central sensing unit; and / or

[0085] 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 the number of the second edge sub-electrodes;

[0086] One of the first edge sub-electrodes and one of the second edge sub-electrodes form an edge sub-sensing unit of a capacitive structure;

[0087] A plurality of the edge sub-sensing units are connected in series to form the edge sensing unit.

[0088] In this implementation manner, dividing the central sensing unit into a plurality of central sub-sensing units, and / or dividing the edge sensing electrode into a plurality of edge sub-sensing units can further increase the voltage sensed by the central electrode and / or the edge electrode on the premise of ensuring that the capacitance value sensed by the central electrode and / or the edge electrode does not decrease.

[0089] In a possible embodiment, in the thickness direction of the piezoelectric film, the projection of one of the first central sub-electrodes on the second central sub-electrode corresponding to its position coincides with the outer shape of the second central sub-electrode; and / or

[0090] The projection of one of the first edge sub-electrodes on the second edge sub-electrode corresponding to its position coincides with the outer shape of the second edge sub-electrode

[0091] In this implementation manner, in the orientation of each of the first central sub-electrodes, the area and shape of the first central sub-electrode and the second central sub-electrode corresponding to its position are the same, and / or the area and shape of each of the first edge sub-electrodes and the second edge sub-electrode corresponding to its position are also the same, which is beneficial to controlling the area ratio of the central sub-electrode and / or the edge sub-electrode on the piezoelectric film and avoiding useless areas with low charge collection efficiency.

[0092] In a possible embodiment, an air vent slit is further provided on the piezoelectric layer, and the air vent slit penetrates through the piezoelectric film and the support layer simultaneously in the thickness direction of the piezoelectric film.

[0093] In this implementation manner, the provision of the air vent slit can balance the air pressure on both sides of the piezoelectric film and avoid forming a pressure difference between the relatively closed inner cavity and the outside. Because the thickness-to-diameter ratio is relatively small, the piezoelectric film is relatively sensitive to the pressure difference between the upper and lower sides. The provision of the air vent slit can protect the piezoelectric film from cracking due to the pressure difference between the upper and lower sides during vibration.

[0094] A possible embodiment, the piezoelectric film includes a plurality of the ventilation slits, and the plurality of the ventilation slits are evenly distributed along the circumferential direction of the piezoelectric film.

[0095] In this implementation, the plurality of the ventilation slits are evenly distributed along the circumferential direction of the piezoelectric film, that is, the plurality of the ventilation slits are distributed on the piezoelectric film in a centrosymmetric manner, which is more conducive to controlling the resonance frequency of the piezoelectric film, and further making the charges collected by each region of the piezoelectric film more balanced.

[0096] A 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.

[0097] In this implementation, the main structure of the support layer may include an insulating material. Therefore, by setting the support layer between the piezoelectric film and the substrate, regardless of the material used for the substrate, the insulating property of the support layer can achieve insulation between the piezoelectric film and the substrate, thereby avoiding possible interference of the current on the substrate to the piezoelectric film.

[0098] A possible embodiment, the piezoelectric film is located between the support layer and the substrate, the main material of the substrate is a silicon wafer, an insulating member is further provided 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.

[0099] In this implementation, since the piezoelectric film is located between the support layer and the substrate, on the premise that the main material of the substrate is a silicon wafer, the substrate has conductivity. To avoid possible influence of the current on the substrate on the piezoelectric film, an insulating member is further provided between the piezoelectric film and the substrate to achieve insulation between the piezoelectric film and the substrate.

[0100] In a third aspect, the present application provides an electronic device, the electronic device includes an audio pickup device. The audio pickup device includes a substrate, a post-processing circuit, and the above piezoelectric microphone;

[0101] The substrate is provided with a sound inlet hole, the sound inlet hole is communicated with the inner cavity of the substrate in the piezoelectric microphone, the post-processing circuit is electrically connected to the piezoelectric microphone, and the post-processing circuit is used to process the induction signal of the piezoelectric microphone.

[0102] The audio pickup device mounted on the electronic device of the present application includes the piezoelectric microphone of the first aspect or the second aspect. It can be understood that since the piezoelectric microphone of the first aspect or the second aspect has a higher response sensitivity to sound signals, the sensitivity of the audio pickup device is improved. The electronic device of the present application thus obtains a better sound collection effect. Description of the Drawings

[0103] Figure 1 is a schematic structural diagram of an audio pickup device provided by an embodiment of the present application;

[0104] Figure 2 is Figure 1 a schematic cross-sectional view of the illustrated audio pickup device along A-A;

[0105] Figure 3 is Figure 1 a schematic structural diagram of the illustrated piezoelectric microphone;

[0106] Figure 4 is Figure 3 a schematic cross-sectional view of the illustrated piezoelectric microphone along B-B;

[0107] Figure 5 is Figure 4 a schematic partial cross-sectional view of the piezoelectric film in the illustrated piezoelectric microphone;

[0108] Figure 6 is Figure 5 a vibration mode analysis diagram of the illustrated piezoelectric film in a possible embodiment;

[0109] Figure 7 is Figure 5 a schematic view of the lower surface of the illustrated piezoelectric film;

[0110] Figure 8 is Figure 5 a schematic view of the upper surface of the illustrated piezoelectric film;

[0111] Figure 9 is Figure 5 a schematic partial cross-sectional view of the illustrated piezoelectric film;

[0112] Figure 10 is Figure 5 a schematic circuit connection diagram of the induction unit in a specific embodiment of the illustrated piezoelectric film;

[0113] Figure 11 is Figure 10 a schematic equivalent connection diagram of the illustrated circuit;

[0114] Figure 12 is Figure 5 a schematic circuit connection diagram of the illustrated piezoelectric film in another embodiment;

[0115] Figure 13 is Figure 5 The vibration mode analysis diagram of the piezoelectric film shown in one possible embodiment;

[0116] Figure 14 is Figure 5 The schematic structural diagram of the piezoelectric film shown in another embodiment;

[0117] Figure 15 is Figure 14 The schematic circuit connection diagram of the piezoelectric film shown;

[0118] Figure 16 is Figure 5 The schematic structural diagram of the piezoelectric film shown in yet another embodiment;

[0119] Figure 17 is Figure 16 The schematic circuit connection diagram of the piezoelectric film shown;

[0120] Figure 18 is Figure 5 The schematic structural diagram of the piezoelectric film shown in yet another embodiment;

[0121] Figure 19 is Figure 18 The schematic circuit connection diagram of the piezoelectric film shown in one embodiment;

[0122] Figure 20 is Figure 18 The schematic circuit connection diagram of the piezoelectric film shown in another embodiment;

[0123] Figure 21 is Figure 18 The schematic circuit connection diagram of the piezoelectric film shown in yet another embodiment;

[0124] Figure 22 is Figure 18 The schematic circuit connection diagram of the piezoelectric film shown in yet another embodiment;

[0125] Figure 23 is Figure 5 The schematic structural diagram of the piezoelectric film shown in another embodiment;

[0126] Figure 24 is Figure 5 The schematic structural diagram of the piezoelectric film shown in yet another embodiment;

[0127] Figure 25 is Figure 5 The schematic structural diagram of the piezoelectric film shown in yet another embodiment;

[0128] Figure 26 is Figure 5 The schematic structural diagram of the piezoelectric film shown in another embodiment;

[0129] Figure 27 is Figure 26 Schematic diagram of the structure of another embodiment of the piezoelectric film shown;

[0130] Figure 28 is Figure 27 Schematic diagram of the partial structure of the piezoelectric film shown;

[0131] Figure 29 is Figure 26 Graph of the residual stress change trend of the piezoelectric film shown in a possible embodiment;

[0132] Figure 30a is Figure 26 Schematic diagram of the stress simulation analysis of the piezoelectric film shown in a possible embodiment;

[0133] Figure 30b is the stress simulation analysis diagram of the cantilever beam structure piezoelectric microphone in the prior art;

[0134] Figure 31 is Figure 26 Schematic diagram of the resonance frequency analysis of the piezoelectric microphone shown in a possible embodiment;

[0135] Figure 32 is Figure 26 Schematic diagram of the signal-to-noise ratio analysis of the piezoelectric microphone shown in a possible embodiment;

[0136] Figure 33 is Figure 3 Schematic diagram of the structure of another embodiment of the piezoelectric microphone shown;

[0137] Figure 34 is the schematic diagram of the structure of the piezoelectric microphone provided by another embodiment of the present application;

[0138] Figure 35 is Figure 34 Cross-sectional schematic diagram of the piezoelectric microphone shown along C-C;

[0139] Figure 36 is Figure 35 Cross-sectional schematic diagram of another embodiment of the piezoelectric microphone shown;

[0140] Figure 37 is Figure 34 Schematic diagram of the circuit connection of the piezoelectric microphone shown;

[0141] Figure 38 is Figure 34 Schematic diagram of the structure of yet another embodiment of the piezoelectric microphone shown;

[0142] Figure 39 is Figure 38 Schematic diagram of the circuit connection of the piezoelectric film layer shown;

[0143] Figure 40 is Figure 34 A schematic structural diagram of another embodiment of the piezoelectric microphone shown;

[0144] Figure 41 is Figure 40 A schematic circuit connection diagram of the piezoelectric film layer shown;

[0145] Figure 42 is Figure 34 A schematic structural diagram of another embodiment of the piezoelectric microphone shown;

[0146] Figure 43 is Figure 42 A schematic circuit connection diagram of one embodiment of the piezoelectric film layer shown;

[0147] Figure 44 is Figure 42 A schematic circuit connection diagram of another embodiment of the piezoelectric film layer shown;

[0148] Figure 45 is Figure 34 A schematic structural diagram of another embodiment of the piezoelectric microphone shown. Detailed implementation manners

[0149] Next, the technical solutions in the embodiments of the present application will be described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts belong to the scope of protection of the present application.

[0150] The serial numbers assigned to the components herein, such as "first", "second", etc., are only used to distinguish the described objects and do not have any sequential or technical meanings. And the "connection" mentioned in the present application, unless otherwise specified, includes both direct and indirect connections. In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0151] In this application, unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature may mean that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above" and "over" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under" and "beneath" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply indicates that the horizontal height of the first feature is less than that of the second feature.

[0152] Please refer to Figure 1 the internal structure of an audio pickup device 200 provided by an embodiment of the present application. The audio pickup device 200 is disposed in an electronic device (not shown in the figure) and is used to implement the audio collection 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 there is an electrical connection between the piezoelectric microphone 100 and the post-processing circuit 202. In one implementation, the piezoelectric microphone 100 and the post-processing circuit 202 are electrically connected through a conductive line 204 on the substrate 201. The piezoelectric microphone 100 is used to sense a sound signal and convert the sound signal into an electrical signal for transmission to the post-processing circuit 202. The post-processing circuit 202 is used to perform processing such as amplifying, filtering, analog-to-digital conversion, or equalization on the electrical signal, and then transmit the processed electrical signal to units such as the processor of the electronic device, so as to realize the collection of the sound signal by the audio pickup device 200.

[0153] The electronic device may be products such as a mobile phone, a tablet computer, a laptop computer, a smart speaker, and other smart home appliances. This embodiment is described by taking the electronic device as 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 can be implemented by selecting a part of the area of an existing PCB board inside the electronic device. For example, a part of the area of the main board, the secondary main board, etc. of the electronic device is used to implement it, thereby improving the integration of the electronic device.

[0154] Figure 2 For Figure 1 the schematic cross-sectional view of the audio pickup device 200 shown cut along the A-A line. In Figure 2In an embodiment, a housing 203 is also fixed on the substrate 201. The piezoelectric microphone 100, the post-processing circuit 202 and the housing 203 are all fixed on 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.

[0155] The piezoelectric microphone 100 includes a base 10 and a piezoelectric film 20. The base 10 is fixedly connected to the substrate 201, and the piezoelectric film 20 is fixed on the side of the base 10 away from the substrate 201. The base 10 is annular, and the annular base 10 encloses a cavity 11. The substrate 201 includes a sound inlet hole 2011, and the cavity 11 of the base 10 communicates with the sound inlet hole 2011. In one embodiment, the inner cavity of the sound inlet hole 2011 is aligned with the inner wall of the cavity 11.

[0156] The piezoelectric film 20 has a planar structure. The piezoelectric film 20 covers the base 10 and shields the cavity 11 and the sound inlet hole 2011 communicating with the cavity 11. The piezoelectric film 20 is used to receive the sound signal introduced from the sound inlet hole 2011 and generate vibrations under the excitation of the sound signal. The piezoelectric film 20 collects and converts the charges formed by the vibrations into electrical signals, realizing the function of the piezoelectric microphone 100 for collecting sound signals.

[0157] The base 10 can be prepared from a silicon wafer. In some other embodiments, the base 10 can also be prepared from a material with a silicon main body. In Figure 2 In the schematic illustration, an insulator 30 is also provided between the piezoelectric film 20 and the base 10. The insulator 30 is used to insulate the piezoelectric film 20 relative to the base 10 to prevent the current on the substrate 201 from entering the piezoelectric film 20 and interfering with the collection of sound signals. The insulator 30 is also annularly arranged, and the annular shape of the insulator 30 matches the annular shape of the base 10. The opposite two planes of the annular insulator 30 are respectively bonded to the base 10 and the piezoelectric film 20. In one embodiment, the insulator 30 can be prepared from polysilicon, silicon nitride (Si3N4) or silicon dioxide (SiO2).

[0158] It can be understood that in some other embodiments, the base 10 can also be directly prepared from an insulating material. At this time, the piezoelectric film 20 can be directly fixedly connected to the base 10.

[0159] Figure 3This is a schematic diagram of the structure of the piezoelectric microphone 100 of the present application. The piezoelectric film 20 includes a piezoelectric layer 21 and a plurality of electrodes 22 disposed in the piezoelectric layer 21. In one embodiment, the piezoelectric layer 21 can be prepared from 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 materials of the electrodes 22 can include molybdenum (Mo), titanium (Ti), platinum (Pt), aluminum (Al), gold (Au), etc. Of course, the materials of the piezoelectric layer 21 and the electrodes 22 are only for illustrative purposes, and the actual products are not limited to the above materials and their compounds.

[0160] After the sound signal enters the cavity 11 through the sound inlet hole 2011, the piezoelectric film 20 vibrates under the action of the sound signal, driving each region of the piezoelectric layer 21 to form stress, and thereby generating charges. By collecting the charges through the electrodes 22, the charges generated by the piezoelectric layer 21 can be transmitted to the post-processing circuit 202, and the post-processing circuit 202 amplifies the electrical signal for the backend audio module (not shown in the figure) of the electronic device to process, realizing the function of sound pickup.

[0161] In the piezoelectric microphone 100 provided by the embodiment of the present application, the electrodes 22 disposed on the piezoelectric layer 21 include a central electrode 221 and a peripheral electrode 222, and the central electrode 221 and the peripheral electrode 222 are spaced apart in the plane direction of the piezoelectric film 20. The central electrode 221 is located at the center of the piezoelectric film 20, and the peripheral electrode 222 surrounds the periphery of the central electrode 221 and is located at the edge of the piezoelectric film 20.

[0162] Further, please refer to Figure 4 the cross-sectional schematic diagram of the piezoelectric film 20 in the B-B direction as shown. In the thickness direction of the piezoelectric film 20, the piezoelectric layer 21 has a lower surface 211 close to the cavity 11 and an upper surface 212 opposite to the lower surface 211. It can be understood that the upper surface 212 is located on the side of the piezoelectric layer 21 away from the cavity 11 relative to the lower surface 211. The central electrode 221 includes a central lower electrode 2211 close to the lower surface 211, a central upper electrode 2212 close to the upper surface 212, and a central middle electrode 2213 located between the central lower electrode 2211 and the central upper electrode 2212. It can be understood that the central lower electrode 2211 corresponds to the first central electrode in the claims of the present application, the central upper electrode 2212 corresponds to the second central electrode, and the central middle electrode 2213 corresponds to the third central electrode.

[0163] In one embodiment, in the thickness direction of the piezoelectric film 20, the bottom surface of the central lower electrode 2211 is flush with the lower surface 211 of the piezoelectric layer 21. In other embodiments, it is also possible to set the top surface of the central lower electrode 2211 to be flush with the lower surface 211 of the piezoelectric layer 21, or the bottom surface of the central lower electrode 2211 to be higher than the lower surface 211 of the piezoelectric layer 21, that is, the central lower electrode 2211 is wholly included in the piezoelectric layer 21. For the central upper electrode 2212, in Figure 4 In the illustrated embodiment, the bottom surface of the central upper electrode 2212 is flush with the top surface 212 of the piezoelectric layer 21. It can be understood that in other embodiments, it is also possible to set the top surface of the central upper electrode 2212 to be flush with the upper surface 212 of the piezoelectric layer 21, or the top surface of the central upper electrode 2212 to be lower than the upper surface 212 of the piezoelectric layer 21, that is, the central upper electrode 2212 is also wholly included in the piezoelectric layer 21.

[0164] The central middle electrode 2213 can be disposed at the midpoint position between the central lower electrode 2211 and the central upper electrode 2212. Of course, in other embodiments, the central middle electrode 2213 can also be closer to the central upper electrode 2212 relative to the central lower electrode 2211, or the central middle electrode 2213 can be closer to the central lower electrode 2211 relative to the central upper electrode 2212. And in the thickness direction of the piezoelectric film 20, the central middle electrode 2213 is spaced apart from the central lower electrode 2211 and the central upper electrode 2212 respectively, and there is piezoelectric material of the piezoelectric layer 21 between the central middle electrode 2213 and the central lower electrode 2211, as well as between the central middle electrode 2213 and the central upper electrode 2212.

[0165] For the edge electrode 222, an edge lower electrode 2221, an edge upper electrode 2222 and an edge middle electrode 2223 are also provided in the thickness direction of the piezoelectric film 20. Among them, 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. There is also piezoelectric material of the piezoelectric layer 21 between the edge middle electrode 2223 and the edge lower electrode 2221, as well as between the edge middle electrode 2223 and the edge upper electrode 2222. It can be understood that the edge lower electrode 2221 also corresponds to the first edge electrode in the claims of the present application, the edge upper electrode 2222 corresponds to the second edge electrode, and the edge middle electrode 2223 corresponds to the third edge electrode.

[0166] It can be understood that the bottom surface of the edge lower electrode 2221 can be flush with the lower surface 211. In some other embodiments, the edge lower electrode 2221 can also be arranged such that its top surface is flush with the lower surface 211, or the edge lower electrode 2221 is arranged such that its bottom surface is higher than the lower surface 211; the bottom surface of the edge upper electrode 2222 can be flush with the upper surface 212. In some other embodiments, the edge upper electrode 2222 can also be arranged such that its top surface is flush with the upper surface 212, or the edge upper electrode 2222 is arranged such that its top surface is lower than the upper surface 212.

[0167] The edge middle electrode 2223 can be arranged at the middle position of the distance between the edge lower electrode 2221 and the edge upper electrode 2222. Of course, in some other embodiments, the edge middle electrode 2223 can also be closer to the edge upper electrode 2222 relative to the edge lower electrode 2221, or the edge middle electrode 2223 is closer to the edge lower electrode 2221 relative to the edge upper electrode 2222.

[0168] When manufacturing the piezoelectric film 20, usually first manufacture the lower layer structure of the electrode 22, and after patterning, form the central lower electrode 2211 and the edge lower electrode 2221; then grow a layer of piezoelectric material, and then manufacture the middle layer structure of the electrode 22, and after patterning, form the central middle electrode 2213 and the edge middle electrode 2223; finally, grow a layer of piezoelectric material, and manufacture the upper layer structure of the electrode 22, and after patterning, form the central upper electrode 2212 and the edge upper electrode 2222. Thus, in one embodiment, the edge lower electrode 2221 is also arranged flush with the central lower electrode 2211, the edge upper electrode 2222 is arranged flush with the central upper electrode 2212, and the edge middle electrode 2223 is arranged flush with the central middle electrode 2213, which can simplify the manufacturing process of the piezoelectric film 20.

[0169] Please refer to Figure 5 , Figure 5 is Figure 4 a partial cross-sectional schematic in the cross-sectional view. Among them, in the schematic of Figure 5 , because the edge electrode 222 surrounds the periphery of the central electrode 221, in order to more clearly show the structure of the sensing unit, Figure 5 the edge electrode 222 on one side of the central electrode 221 is shown. In the piezoelectric film 20 of the present application, a first sensing unit 301 and a second sensing unit 302 formed by the central electrode 221, and a third sensing unit 303 and a fourth sensing unit 304 formed by the edge electrode 222 are formed.

[0170] The central middle electrode 2213 and the central lower electrode 2211 form the first induction unit 301 of the capacitive structure. The induced charges formed by the piezoelectric layer 21 are collected by the first induction unit 301 to form the 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 the second induction unit 302 of the capacitive structure. The induced charges formed by the piezoelectric layer 21 are collected by the second induction unit 201 to form the second capacitance C2, and a second voltage V2 is formed between the central middle electrode 2213 and the central upper electrode 2212. It can be understood that the first induction unit 301 can correspond to the first capacitance in the specification of the present application, and the second induction unit 302 can correspond to the second capacitance in the specification of the present application.

[0171] In an embodiment, the central middle electrode 2213 is set at the midpoint position of the distance between the central lower electrode 2211 and the central upper electrode 2212, and the shapes and sizes of the central middle electrode 2213, the central lower electrode 2211, and the central upper electrode 2212 are the same, that is, the areas of the central middle electrode 2213, the central lower electrode 2211, and the central upper electrode 2212 are the same. Or it can be described as that in the thickness direction of the piezoelectric film 20, the projection of the central middle electrode 2213 on the central lower electrode 2211 coincides with the shape of the central lower electrode 2211; 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.

[0172] For the piezoelectric layer 21, the charges generated by its vibration are distributed in a centrosymmetric manner. In the thickness direction of the piezoelectric film 20, there is a central plane B1 at the center of the piezoelectric layer 21. The charge polarity formed by the piezoelectric layer 21 above the central plane B1 is opposite to the charge polarity formed by the piezoelectric layer 21 below the central plane B1. Therefore, when the central middle electrode 2213 is set at the middle position of the distance between the central lower electrode 2211 and the central upper electrode 2212, the central middle electrode 2213 coincides with the central plane B1. At this time, the first voltage V1 induced by the first induction unit 301 and the second voltage V2 induced by the second induction unit 201 are equal in value and opposite to each other, that is, |V1| = |V2|.

[0173] On the other hand, because the shapes and areas of the central lower electrode 2211, the central middle electrode 2213, and the central upper electrode 2212 are the same, the first capacitance C1 induced by the first induction unit 301 and the second capacitance C2 induced by the second induction unit 302 are also equal in value, that is, C1 = C2.

[0174] For the third induction unit 303 and the fourth induction unit 304 formed by the edge electrodes 222, they are similar to the first induction unit 301 and the second induction unit 302 formed by the central electrode 221. Among them, the third induction unit 303 is composed of the edge middle electrode 2223 and the edge lower electrode 2221. The induced charges formed by the piezoelectric layer 21 are collected by the third induction unit 303 to form a third capacitor C3, and a third voltage V3 is formed between the edge middle electrode 2223 and the edge lower electrode 2221; the fourth induction unit 304 is composed of the edge middle electrode 2223 and the edge upper electrode 2222. The induced charges formed by the piezoelectric layer 21 are collected by the fourth induction 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 can be understood that the third induction unit 303 can correspond to the third capacitor in the specification of this application, and the fourth induction unit 304 can correspond to the fourth capacitor in the specification of this application.

[0175] In an embodiment, the edge middle electrode 2223 is also set at the midpoint of the distance between the edge lower electrode 2221 and the edge upper electrode 2222, and the shapes and sizes of the edge middle electrode 2223, the edge lower electrode 2221, and the edge upper electrode 2222 are the same. Thus, for the third induction unit 303 and the fourth induction unit 304, the effects of |V3| = |V4| and C3 = C4 are also formed. Among them, the third voltage V3 and the fourth voltage V4 are equal in value and opposite to each other, while the third capacitor C3 and the fourth capacitor C4 are equal in value.

[0176] For details, please refer to Figure 6 the vibration mode analysis diagram of the piezoelectric film 20 shown in a specific implementation manner. After the piezoelectric film 20 receives a sound signal, it vibrates due to the action of sound pressure. The vibration of the piezoelectric film 20 will generate stress and cause the phenomenon of stress concentration inside it. Through Figure 6 it can be seen that the main regions of stress concentration are distributed in the central region A0 and the edge region A2 of the piezoelectric film 20. That is, the stress generated in the central region A0 and the edge region A2 is relatively large. According to the charge quantity formula:

[0177] Q = Ad 31 δ Formula (1);

[0178] where, d 31is the piezoelectric coefficient of the piezoelectric material in the piezoelectric layer 21; δ is the stress generated in the corresponding area under the action of the sound signal; A is the effective area where the generated stress meets the charge collection requirement. It can be seen that on the piezoelectric film 20, the effective area region where stress concentration can be formed and a relatively large stress can be generated to meet the charge collection requirement is not large, and it is concentrated at the center A0 and the edge A2. In this embodiment, the piezoelectric film 20 is circular, so the central region A0 of the stress concentration is also circular. Since the substrate 10 is in the shape of a ring and the connection between the piezoelectric film 20 and the substrate 10 is fixed in a ring shape, the edge region A2 is also distributed in a ring shape. The transition region A1 between the central region A0 and the edge region A2 has relatively small stress and is in a state where the stress is zero or close to zero. In the case where the effective area region is limited, the sensitivity of the traditional piezoelectric microphone has limitations. For example, the sensitivity of a traditional piezoelectric microphone product is maintained at about -43 dB.

[0179] After the central electrode 221 and the edge electrode 222 are provided, the regions in the piezoelectric film 20 where the induced stress is relatively large can be covered, the sensing area can be increased, and thus the charge collection effect can be improved. At the same time, the stress directions formed in the central region A0 and the edge region A2 are opposite to each other. When the stress formed in the central region A0 is defined as tensile stress, the stress in the edge region A2 is compressive stress; conversely, when the stress in the central region A0 is compressive stress, the stress in the edge region A2 is tensile stress.

[0180] Corresponding to the electrode 22, for the first sensing unit 301 and the third sensing unit 303 at the same plane height, the first sensing unit 301 forms a first voltage V1 due to tensile stress at the central region AO, and the third sensing unit 303 forms a third voltage V3 due to compressive stress at the edge region A2. Therefore, the stress direction of the first sensing unit 301 is opposite to the stress direction of the third sensing unit 303, and the polarities of the first voltage V1 and the third voltage V3 formed thereby are also opposite; there is a similar relationship between the second sensing unit 302 and the fourth sensing unit 304 at the same plane height, that is, the polarities of the second voltage V2 and the fourth voltage V4 are opposite.

[0181] Please refer to Figure 7 the schematic diagram of the lower surface 211 of the piezoelectric film 20 shown, and Figure 8 the schematic diagram of the upper surface 212 of the piezoelectric film 20 shown. The piezoelectric microphone 100 of the present application also has a connection line 23 provided on the piezoelectric film 20. In this embodiment, the connection line 23 is connected between the central lower electrode 2211 and the edge lower electrode 2212, and between the central upper electrode 2212 and the edge upper electrode 2222. Further, please refer to Figure 9Schematic cross-sectional view of the piezoelectric film 20. A first connection terminal 241 and a second connection terminal 242 are respectively provided at the central middle electrode 2213 and the edge middle electrode 2223. The first connection terminal 241 can be used as the ground terminal or the output terminal of the piezoelectric microphone 100, and correspondingly, the second connection terminal 242 can be used as the output terminal or the ground terminal of the piezoelectric microphone 100. The first connection terminal 241 and the second connection terminal 242 are respectively electrically connected to the post-processing circuit 202 at the back end, thereby realizing the electrical connection between the piezoelectric microphone 100 and the post-processing circuit 202.

[0182] Among them, the second connection terminal 242 is provided at the edge middle electrode 2223, and its electrical connection with the post-processing circuit 202 can be directly completed through the conductive line 204 on the substrate 201. The first connection terminal 241 is provided at the central middle electrode 2213. It is necessary to make a via hole 25 (see Figure 8 ) at a position on the piezoelectric layer 21 close to the central middle electrode 2213 to lead out the electrical signal and connect it to the conductive line 204 of the substrate 201 to realize the electrical connection between the first connection terminal 241 and the post-processing circuit 202 at the back end.

[0183] Through the above wiring settings, the circuit connection schematic diagram in the piezoelectric film 20 of the present application can be seen in Figure 10 : The first induction unit 301 (composed of the central middle electrode 2213 and the central lower electrode 2211) and the second induction unit 302 (composed of the central middle electrode 2213 and the central upper electrode 2212) form a parallel connection. At the same time, the third induction unit 303 (composed of the edge middle electrode 2223 and the edge lower electrode 2221) and the fourth induction unit 304 (composed of the edge middle electrode 2223 and the edge upper electrode 2222) also form a parallel connection. Then, the parallel first induction unit 301 and the second induction unit 302 are connected in series with the parallel third induction unit 303 and the fourth induction unit 304, and finally, an electrical signal is output to the post-processing circuit at the back end. Figure 10 In order to clearly represent each induction unit, the central middle electrode 2213 shared by the first induction unit 301 and the second induction unit 302 is separately drawn, and the edge middle electrode 2223 shared by the third induction unit 303 and the fourth induction unit 304 is also separately drawn.

[0184] As mentioned in the previous text, the polarities of the first voltage V1 and the second voltage V2 are opposite, and at the same time, the polarity of the first voltage V1 is also opposite to that of the third voltage V3, that is, the polarities of the second voltage V2 and the third voltage V3 are the same. Therefore, Figure 10 The circuit connection schematic diagram of Figure 11Schematic diagram of equivalent circuit connection: The central upper electrode 2212 is connected to the edge upper electrode 2222, the central lower electrode 2211 is connected to the edge lower electrode 2221, and the central middle electrode 2213 and the edge middle electrode 2223 are respectively connected to the post-processing circuit 202 at the back end as the output terminals of the piezoelectric film 20.

[0185] At this time, for the central electrode 221, its first induction unit 301 and second induction unit 302 are in a parallel structure, forming a central induction unit 401. Correspondingly, the voltage V12 of the central induction unit 401 = |V1| = |V2|, and the capacitance C12 of the central induction unit 401 = C1 + C2; for the edge electrode 222, its third induction unit 303 and fourth induction unit 304 are also in a parallel structure, forming an edge induction unit 402. Correspondingly, the voltage V34 of the edge induction unit 402 = |V3| = |V4|, and the capacitance C34 of the edge induction unit 402 = C3 + C4.

[0186] After the central induction unit 401 and the edge induction unit 402 are connected in series, the induced voltage V sensed by the piezoelectric microphone 100 of the present application is obtained:

[0187] V = V12 + V34 Formula (2);

[0188] At the same time, the induced capacitance C sensed by the piezoelectric microphone 100 of the present application:

[0189]

[0190] Existing traditional piezoelectric microphones usually only set electrode structures covering their edge regions or central regions. Therefore, the induced voltage V' of traditional piezoelectric microphones is usually only V12 or V34, and the capacitance C' sensed by traditional microphones is usually C12 or C34. Through the structural settings 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 settings of the connection methods between the two, the induced voltage V and the induced capacitance C obtained by the piezoelectric film 20 of the present application under the excitation of sound signals are both increased, thereby improving the sensitivity of the piezoelectric microphone 100 of the present application.

[0191] For another embodiment, please refer to Figure 12 , the central electrode 221 and the edge electrode 222 can also be connected in parallel. That is, a first connection end 241 is led out from the central middle electrode 2213 of the central electrode 221, then the central upper electrode 2212 and the central lower electrode 2211 are respectively connected to the edge middle electrode 2223, and finally the edge upper electrode 2222 and the edge lower electrode 2221 are conducted and a second connection end 242 is led out. At this time, the induced voltage V sensed by the piezoelectric microphone 100 of the present application:

[0192]

[0193] Meanwhile, the induced capacitance C sensed by the piezoelectric microphone 100 is:

[0194] C = C12 + C34 Formula (3');

[0195] It can be seen that for the piezoelectric microphone 100 with the central electrode 221 and the edge electrode 222 in parallel, the obtained induced voltage V and induced capacitance C are also larger than those of the traditional piezoelectric microphone. This embodiment is applicable to the case where the voltage requirement for the piezoelectric microphone 100 is relatively low, but the capacitance requirement is relatively high.

[0196] In one embodiment, the total thickness of the piezoelectric film 20 is controlled between 0.3 and 2 μm, while the thicknesses 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 are controlled between 0.01 and 0.15 μm. The thickness of the electrode 22 can increase the overall stiffness of the piezoelectric film 20 while not affecting the vibration sensitivity of the piezoelectric film 20 under sound signals.

[0197] In one embodiment, defining the coverage area of the edge electrode 222 on the plane of the circular piezoelectric layer 21 with a radius R, it is necessary 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 50% of R and greater than or equal to 5% of R. 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 10% - 30% of R.

[0198] Correspondingly, the coverage area of the central electrode 221 on the piezoelectric layer 21 is also defined as the radius of the central electrode 221 being r, and r satisfies the condition: 50% of R ≥ r ≥ 5% of R. Preferably, in this embodiment, the radius r of the central electrode 221 is 20% - 40% of R.

[0199] In other embodiments, if the piezoelectric layer 21 is of a shape other than circular, for the central electrode 221, when the distance from the center of the piezoelectric layer 21 to the edge in any direction is L, the first dimension L1 of the central electrode 221 in this direction also needs to satisfy the condition: 50% of L ≥ L1 ≥ 5% of L. Preferably, it can also be controlled that 40% of L ≥ L1 ≥ 20% of L; and for the edge electrode 222 in this direction, the second dimension L2 from its inner edge to the outer edge also needs to be less than or equal to 50% of L and greater than or equal to 5% of L. Preferably, it can also be controlled that 30% of L ≥ L2 ≥ 10% of L.

[0200] Regarding the coverage area of the central electrode 221 and the edge electrode 222 on the piezoelectric layer 21 respectively, it is also an important factor affecting the sensitivity of the piezoelectric microphone 100. Please refer to Figure 13 As shown, taking the edge electrode 222 as an example in one possible implementation, for the structure of the edge electrode 222 obtained by simulation, the edge area of the edge electrode 222 covering the piezoelectric layer 21 is differentiated from the outside to the inside to obtain the first stress region 01, the second stress region 02, and the third stress region 03. The voltage V of the first stress region 01 01 satisfies:

[0201]

[0202] where, Q 01 is the electric charge generated by the first stress region 01 under the action of a sound signal; C 01 is 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 Figure 13 the schematic illustration, the ε of different stress regions is the same; A 01 is the area of the first stress region 01.

[0203] And the electric charge Q of the first stress region 01 01 then satisfies:

[0204] Q 01 = A 01 d 31 δ 01 Formula (5);

[0205] where, d 31 is the piezoelectric coefficient of the piezoelectric material including the first stress region 01, the second stress region 02, and the third stress region 03; δ 01 is the stress borne by the first stress region 01 under the action of a sound signal. It can be seen that after substituting Formula (5) into Formula (4), the voltage V of the first stress region 01 01 can also be expressed as:

[0206]

[0207] By analogy, the voltage of the second stress region 02 can also be deduced The voltage of the third stress region 03 Since the first stress region 01 is located outside the second stress region 02, the stress in the first stress region 01 is greater than that in the second stress region 02. Similarly, the stress in the second stress region 02 is greater than that in the third stress region 03, that is, δ1>δ2>δ3. Thus, the following relationship can be obtained for the voltages obtained by the coverage of the edge electrode 222 on the above three different stress regions: V 01 >V 02 >V 03 .

[0208] The above analysis is based on the assumption that the edge electrode 222 only covers the first stress region 01, the second stress region 02, or the third stress region 03. In an actual embodiment, in addition to setting the edge electrode 222 to only cover the first stress region 01, the edge electrode 222 can also be set to cover both the first stress region 01 and the second stress region 02 at the same time. At this time, the voltage V sensed by the edge electrode 222 012 can be expressed as:

[0209]

[0210] And since V 01 >V 02 >V 03 , it can be deduced that V 012 <V 01 . Further, the edge electrode 222 can also cover the first stress region 01, the second stress region 02, and the third stress region 03 at the same time. At this time, the voltage V of the edge electrode 222 0123 is expressed as:

[0211]

[0212] Similarly, since V 01 >V 02 >V 03 , it can be deduced that V 0123 <V 012 <V 01 .

[0213] That is to say, for the coverage area of the edge electrode 222 on the piezoelectric layer 21, the smaller the coverage area of the edge electrode 222, the greater the output voltage, but this brings the adverse effect of too small output capacitance. Referring to the formula for the thermal noise spectrum n caused by the dielectric loss of the material:

[0214]

[0215] Where k is the Boltzmann constant; T is the temperature (unit: Kelvin); ω is the operating frequency; C is the capacitance; and tanδ is the tangent of the dielectric loss angle of the piezoelectric material. Since the dielectric loss angle of the piezoelectric material is constant, its tangent value is also a fixed value. At this time, an overly small capacitance C will cause the noise floor output caused by dielectric loss to increase. In addition, the capacitance C of the piezoelectric microphone 100 and the subsequent post-processing circuit 202 will form a series capacitance configuration, 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 will cause the output capacitance of the post-processing circuit 202 to act as a capacitive voltage 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.

[0216] On the other hand, if the coverage area of the edge electrode 222 is too large, it will also reduce the voltage V output by the piezoelectric microphone 100. That is, it is manifested that the piezoelectric microphone 100 only contributes capacitance but not charge, resulting in a decrease in the output voltage V and a reduction 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 requirements and obtain a larger voltage V, it is necessary to limit the coverage area of the edge electrode 222 on the piezoelectric layer 21. When setting the distance from the inner ring edge of the edge electrode 222 to the outer edge of the piezoelectric layer 21 to be less than or equal to 50% of R and greater than or equal to 5% of R; and at the same time setting the radius of the central electrode 221 to be r, then r satisfies the condition: 50% of R ≥ r ≥ 5% of R, it is possible to ensure the coverage of the effective area of the piezoelectric layer 21 by the edge electrode 222 and the central electrode 221.

[0217] For an embodiment, please refer to Figure 14 , in the planar direction of the piezoelectric film 20, the central electrode 221 is further patterned and divided, so 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 can be understood that the central lower unit 2211a can correspond to the first central sub-electrode in the claims of the present application, the central upper unit 2212a can correspond to the second central sub-electrode, and the central middle unit 2213a can correspond to the third central sub-electrode.

[0218] In one embodiment, the shapes and areas of the plurality of central lower units 2211a are equal, that is, the central lower electrode 2211 is evenly divided into a plurality of central lower units 2211a with the same area; the central middle electrode 2213 is evenly divided into a plurality of central middle units 2213a with the same area; and the central upper electrode 2212 is evenly divided into a plurality of central upper units 2212a with the same area. In one embodiment, the dividing lines of the plurality of central lower units 2211a all pass through the geometric center of the piezoelectric film 20.

[0219] In the thickness direction of the piezoelectric film 20, the shape and size of each central lower unit 2211a and the corresponding central middle unit 2213a are equal, and the shape and size of the central middle unit 2212a are also equal to those of the corresponding central upper unit 2212a. Thus, the central lower unit 2211a, the central middle unit 2213a, and the central upper unit 2212a corresponding in the thickness direction of the piezoelectric film 20 form a central sub-sensing unit 403. Multiple central sub-sensing units 403 form the central sensing unit 401. The voltage values and capacitance values sensed by each central sub-sensing unit 403 are respectively the same, and the voltage and capacitance formed after their connection are also larger. In the same connection manner as the central sensing unit 401, in this embodiment, each central sub-sensing unit 403 first connects its own two capacitive structures in parallel, and then connects multiple central sub-sensing units 403 in series, and then connects them in series with the edge sensing unit 402 to form the output voltage V and output capacitance C of the piezoelectric film 20. It can be understood that the two capacitive structures of the central sub-sensing unit 403 itself can correspond to the first sub-capacitance and the second sub-capacitance in the claims of the present application.

[0220] Specifically, please refer to Figure 15 the connection schematic diagram. After conducting the central upper unit 2212a and the central lower unit 2211a of the front-end central sub-sensing unit 403, the central middle unit 2213a of this central sub-sensing unit 403 is simultaneously connected to the central upper unit 2212a and the central lower unit 2211a of the next central sub-sensing unit 403, and after connecting each central sub-sensing unit 403 in sequence, the central middle unit 2212a of the terminal central sub-sensing unit 403 is simultaneously connected to the edge upper electrode 2222 and the edge lower electrode 2221 of the edge sensing unit 402. Finally, the connection line of the central upper unit 2212a and the central lower unit 2211a of the front-end central sub-sensing unit 403 is used as the first connection end 241, and the wire led out from the edge middle electrode 2223 is used as the second connection end 242, which are respectively connected to the subsequent post-processing circuit 202.

[0221] At this time, because a structure with two capacitors connected in parallel is formed inside the multiple central sub-sensing units 403, and then multiple central sub-sensing units 403 are connected in series, the output voltage V12a of the central sensing unit 401 composed of multiple central sub-sensing units 403 to the subsequent post-processing circuit 202 is V12a = 6 * V12; the capacitance of the central sensing unit 401 After connecting the edge sensing unit 402 in series, the output voltage V of the piezoelectric film 20 of the present application can be expressed as:

[0222] V = V12a + V34 = 6 * V12 + V34 Formula (10);

[0223] The capacitance C output by the piezoelectric film 20 can be expressed as:

[0224]

[0225] It can be seen that in this embodiment, by dividing the central electrode 221, the induced voltage V12a of the central induction unit 401 is increased, and then 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 requirements, a larger output voltage V can be obtained, thereby improving the sensitivity of the piezoelectric microphone 100 of the present application.

[0226] For another embodiment, please refer to Figure 16 , in the plane direction of the piezoelectric film 20, the edge electrode 222 is also patterned and divided, so that the edge lower electrode 2221 is divided into at least two edge lower units 2221a, the edge middle electrode 2223 is divided into a plurality of edge middle units 2223a with the same number, and the edge upper electrode 2222 is divided into a plurality of edge upper units 2222a with the same number. In one embodiment, the plurality of edge lower units 2221a can also be set to have the same shape and area, that is, the edge lower electrode 2221 is evenly divided into a plurality of edge lower units 2221a with the same area; the edge middle electrode 2223 is evenly divided into a plurality of edge middle units 2223a with the same area; the edge upper electrode 2222 is evenly divided into a plurality of edge upper units 2222a with the same area. In one embodiment, the extension lines of the dividing lines of the plurality of edge lower units 2221a also pass through the geometric center of the piezoelectric film 20. It can be understood that the edge lower unit 2221a can correspond to the first edge sub-electrode in the claims of the present application, the edge upper unit 2222a can correspond to the second edge sub-electrode, and the edge middle unit 2223a can correspond to the third edge sub-electrode.

[0227] Similarly, in the thickness direction of the piezoelectric film 20, the edge lower unit 2221a, the edge middle unit 2223a, and the edge upper unit 2222a that correspond to each other in position also have the same shape and size, and are combined in parallel to form an edge sub-induction unit 404. A plurality of edge sub-induction units 404 form an edge induction unit 402. In Figure 16 the embodiment, the edge induction unit 402 is composed of 6 edge sub-induction units 404. When the induced voltage of the undivided edge induction unit 402 is V34, the voltage of each edge sub-induction unit 404 is V34; when the induced capacitance of the undivided edge induction unit 402 is C34, the capacitance of each edge sub-induction unit is C34 / 6. The voltage values and capacitance values sensed by each edge sub-induction unit 404 are the same respectively, and the voltage and capacitance formed after their connection are also larger. Please watch synchronously Figure 17Connection schematic diagram. After the edge sub-sensing unit 404 first connects its two capacitance structures in parallel, multiple edge sub-sensing units 404 are connected in series, and then connected in series with the central sensing unit 401 to form the output voltage V and output capacitance C of the piezoelectric film 20. Specifically, the upper edge unit 2222a and the lower edge unit 2221a at the front end of the edge sub-sensing unit 404 are conducted and the first connection end 241 is led out. The middle edge unit 2223a of the edge sub-sensing unit 404 is simultaneously connected to the upper edge unit 2222a and the lower edge unit 2221a of the next edge sub-sensing unit 404. After connecting each edge sub-sensing unit 404 in sequence, the middle edge unit 2223a of the edge sub-sensing unit 404 at the end is set to be simultaneously connected to the central upper electrode 2212 and the central lower electrode 2211 of the central sensing unit 401. Finally, the second connection end 242 is led out by the central middle electrode 2213. The first connection end 241 and the second connection end 242 are respectively connected to the post-processing circuit 202 at the back end. It can be understood that the two capacitance structures of the edge sub-sensing unit 404 itself can correspond to the third sub-capacitance and the fourth sub-capacitance in the claims of the present application.

[0228] and Figure 14 and Figure 15 The connection method of is similar. In this embodiment, the division of the edge sensing unit 402 makes the output voltage V34a of the edge sensing unit 402 = 6 * V34; the capacitance of the edge sensing unit 402 After connecting the central sensing unit 401 in series, the voltage V output by the piezoelectric film 20 of the present application can be expressed as:

[0229] V = V12 + V34a = V12 + 6 * V34 Formula (12);

[0230] The output capacitance C of the piezoelectric film 20 can be expressed as:

[0231]

[0232] With the same effect, in this embodiment, by dividing the edge electrode 222, the induced voltage V34a of the edge sensing unit 402 is increased, and then 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 requirements, a larger output voltage V can be obtained, thereby improving the sensitivity of the piezoelectric microphone 100 of the present application.

[0233] For an embodiment, please refer to Figure 18, the central induction unit 401 is divided into M central sub - induction units 403, and at the same time, the edge induction unit 402 is divided into N edge sub - induction units 404. In this embodiment, two capacitance structures of each central sub - induction unit 403 are connected in parallel, and two capacitance structures of each edge sub - induction unit 404 are also connected in parallel. Then, all the central sub - induction units 403 and all the edge sub - induction units 404 are connected in series one by one to form the output voltage V and output capacitance C of the piezoelectric film 20. It can be understood that, similar to the calculation method of the above - mentioned Figures 14 to 17 embodiment, in Figure 18 , the voltage V output by the piezoelectric film 20 can be expressed as:

[0234] V = V12a + V34a = M * V12+N * V34 Formula (14);

[0235] The capacitance C output by the piezoelectric film 20 can be expressed as:

[0236]

[0237] It can be seen that in this embodiment, the output voltage V of the piezoelectric film 20 is further increased. By matching and selecting the values of M and N through the capacitance value ratio of the edge induction unit 402 and the central induction unit 401, the capacitance C34a of the edge induction unit 402 can be made close to the capacitance C12a of the central induction unit 401, that is, the values of C34a / N2 and C12a / M2 are approximately equal. At this time, the output capacitance C of the piezoelectric film 20 is also relatively large, which can meet the requirements and reduce the signal - to - noise ratio. In Figure 18 the embodiment, the number M of the central sub - induction units 403 is set to 2, and the number N of the edge sub - induction units 404 is set to 6; in another embodiment, the number M of the central sub - induction units 403 is set to 4, and the number N of the edge sub - induction units 404 is set to 9.

[0238] For Figure 18 the schematic diagram of the circuit connection in the embodiment, reference can be made to the schematic diagram in Figures 19 to 22 . In Figure 19In the schematic diagram, after the M central sub-sensing units 403 are connected in series in sequence, they are then connected in series with the N peripheral sub-sensing units 404. Specifically, the upper central unit 2212a and the lower central unit 2211a of the front-end central sub-sensing unit 403 are conducted to lead out a first connection terminal 241. The middle central unit 2213a of this central sub-sensing unit 403 is simultaneously connected to the upper central unit 2212a and the lower central unit 2211a of the next central sub-sensing unit 403. After connecting the M central sub-sensing units 403 in sequence, it is set that the middle central unit 2213a of the terminal central sub-sensing unit 403 is simultaneously connected to the upper peripheral unit 2222a and the lower peripheral unit 2221a of a peripheral sub-sensing unit 404. The middle peripheral unit 2223a of this peripheral sub-sensing unit 404 is simultaneously connected to the upper peripheral unit 2222a and the lower peripheral unit 2221a of the next peripheral sensing unit 404. After connecting the N peripheral sub-sensing units 404 in sequence, it is set that the middle peripheral unit 2223a of the terminal peripheral sub-sensing unit 404 leads out a second connection terminal 242. It can be understood that subsequently, the first connection terminal 241 and the second connection terminal 242 are respectively connected to the subsequent post-processing circuit 202, forming the output voltage V and the output capacitance C of the piezoelectric microphone 100 of the present application.

[0239] While in Figure 20 In the schematic diagram, first, the N peripheral sub-sensing units 404 are connected in series, and then they are connected in series with the M central sub-sensing units 403. Specifically, the peripheral sub-sensing unit 404 is used as the front-end output, and its upper peripheral unit 2222a and lower peripheral unit 2221a are conducted to lead out a first connection terminal 241. The middle peripheral unit 2223a of this peripheral sub-sensing unit 404 is simultaneously connected to the upper peripheral unit 2222a and the lower peripheral unit 2221a of the next peripheral sub-sensing unit 404. After connecting the N peripheral sub-sensing units 404 in sequence, it is set that the middle peripheral unit 2223a of the terminal peripheral sub-sensing unit 404 is simultaneously connected to the upper central unit 2212a and the lower central unit 2211a of a central sub-sensing unit 403. The middle central unit 2213a of this central sub-sensing unit 404 is connected to the upper central unit 2212a and the lower central unit 2211a of the next central sub-sensing unit 403. After connecting the M central sub-sensing units 403 in sequence, it is set that the middle central unit 2213a of the terminal central sub-sensing unit 403 leads out a second connection terminal 242. It can be understood that subsequently, the first connection terminal 241 and the second connection terminal 242 are respectively connected to the subsequent post-processing circuit 202, forming the output voltage V and the output capacitance C of the piezoelectric microphone 100 of the present application.

[0240] It should be noted that in the above embodiments, the connection between each sensing unit is completed through the connection line 23, or the connection line 23 in cooperation with the via 25. Specifically, for the connection and conduction between the central middle unit 2213a and the edge middle unit 2223a in the same plane layer, it can be realized only through the connection line 23; for the connection and conduction between the central middle unit 2213a and the upper edge unit 2222a or the lower edge unit 2221a in different plane layers, it needs to be realized through the connection line 23 in cooperation with the via 25. Since the structures of the connection line 23 and the via 25 are general structures in the art, no detailed description is made herein in this application.

[0241] In Figure 21 and Figure 22 's schematic illustration, M central sub-sensing units 403 and N edge sub-sensing units 404 are cross-connected in series, which can shorten the total length of the connection line 23 and simplify the internal structure of the piezoelectric film 20. Specifically, in Figure 21 's connection schematic illustration, based on M > N, that is, the number M of the central sub-sensing units 403 is greater than the number N of the edge sub-sensing units 404. At this time, the central sub-sensing unit 403 at the front end is also conducted through its central upper unit 2212a and central lower unit 2211a and leads out the first connection end 241. Then, the central middle unit 2213a of this central sub-sensing unit 403 is conducted with the edge middle unit 2223a of an edge sub-sensing unit 404. The upper edge unit 2222a of this edge sub-sensing unit 404 is conducted with the central upper unit 2212a of the next central sub-sensing unit 403, and at the same time, the lower edge unit 2221a of this edge sub-sensing unit 404 is conducted with the central lower unit 2211a of the next central sub-sensing unit 403. The central middle unit 2213a of the next central sub-sensing unit 403 is conducted with the edge middle unit 2223a of the next edge sub-sensing unit 404. In this way, after N central sub-sensing units 403 are successively connected in series with N edge sub-sensing units 404, the remaining (M - N) central sub-sensing units 403 are successively connected in series, and the second connection end 241 is led out at the central middle unit 2213a of the last central sub-sensing unit 403 at the end. It can be understood that subsequently, the first connection end 241 and the second connection end 242 are respectively connected to the subsequent post-processing circuit 202, forming the output voltage V and output capacitance C of the piezoelectric microphone 100 of this application.

[0242] In Figure 22In the connection diagram, it is expanded based on M < N, that is, the number M of the central sub-induction units 403 is less than the number N of the peripheral sub-induction units 404. At this time, the peripheral sub-induction unit 404 at the front end also leads out the first connection terminal 241 through the conduction of the upper unit 2222a and the lower unit 2221a on its edge. Then, the middle unit 2223a on the edge of the peripheral sub-induction unit 404 is conducted with the middle unit 2213a of a central sub-induction unit 403. The upper central electrode 2212a of the central unit 403 is then conducted with the upper unit 2222a on the edge of the next peripheral sub-induction unit 404, and at the same time, the lower central electrode 2211a of the central unit 403 is conducted with the lower unit 2221a on the edge of the next peripheral sub-induction unit 404. The middle unit 2223a on the edge of the next peripheral sub-induction unit 404 is then conducted with the middle unit 2213a of the next central sub-induction unit 403. In this way, after M peripheral sub-induction units 404 are sequentially connected in series with M central sub-induction units 403, the remaining (N - M) peripheral sub-induction units 404 are then sequentially connected in series, and the second connection terminal 241 is led out at the middle unit 2223a on the edge of the last peripheral sub-induction unit 404 at the end. It can be understood that subsequently, the first connection terminal 241 and the second connection terminal 242 are respectively connected to the post-processing circuit 202 at the back end, forming the output voltage V and the output capacitance C of the piezoelectric microphone 100 of the present application.

[0243] It should be noted that in Figure 21 the embodiment, it is also possible to first conduct the upper unit 2222a and the lower unit 2221a on the edge of a peripheral sub-induction unit 404 and lead out the first connection terminal 241, and then after connecting the peripheral sub-induction unit 404 in series with a central sub-induction unit 403, the central sub-induction unit 403 is cross-connected in series with the next peripheral sub-induction unit 404; or in Figure 22 the embodiment, conduct the upper central unit 2212a and the lower central unit 2211a of a central sub-induction unit 403 and lead out the first connection terminal 241, and then realize the cross-series connection of each central sub-induction unit 403 and each peripheral sub-induction unit 404, and the same output voltage V and output capacitance C can be obtained.

[0244] In an embodiment, when each peripheral sub-induction unit 404 is connected to the central sub-induction unit 403, it is connected to the central sub-induction unit 403 that is relatively close to it; correspondingly, each central sub-induction unit 403 is also connected to the peripheral sub-induction unit 404 that is relatively close to it. For example, in Figure 23In the schematic diagram, the number of central sub-sensing units 403 is 6, and the number of edge sub-sensing units 404 is also 6. The connection line 23 disposed between two adjacent central upper units 2212a and edge upper units 2222a extends along the radial direction of the circular central electrode 221 to the edge upper unit 2222a to form conduction. At this time, the distances of the six connection lines 23 are relatively short, and there will be no intersection between the connection lines 23.

[0245] On the other hand, for the shape of the central electrode 221 and the shape of the edge electrode 222, the piezoelectric microphone 100 of the present application is not particularly limited either. The shape of the central electrode 221 can be an axisymmetric shape (such as Figure 24 the ellipse shown), or a centrosymmetric shape (such as Figure 25 the regular polygon shown); the shape of the edge electrode 222 can match the shape of the central electrode 221 and is also a centrosymmetric shape (such as Figure 23 the circular ring shown), or an axisymmetric shape (such as Figure 24 the elliptical ring shown). The edge electrode 222 can also be set to other shapes different from the central electrode 221 (such as Figure 25 the circular ring shown). The specific shapes of the central electrode 221 and the edge electrode 222 can be adjusted arbitrarily according to the installation position of the piezoelectric microphone 100.

[0246] It can be understood that corresponding to the embodiment in which the central electrode 221 and the edge electrode 222 shown in Figure 12 are connected in parallel, in the embodiment in which the central sensing unit 401 is divided into multiple central sub-sensing units 403, the central sensing unit 401 composed of multiple central sub-sensing units 403 and the edge sensing unit 402 can be connected in parallel, which can also improve the sensing sensitivity of the piezoelectric microphone 100. At this time, multiple central sub-sensing units 403 can also be connected in series, or still be connected in parallel; and for the embodiment in which the edge sensing unit 402 is divided into multiple edge sub-sensing units 404, the edge sensing unit 402 composed of multiple edge sub-sensing units 404 and the central sensing unit 401 can be connected in parallel to improve the sensing sensitivity of the piezoelectric microphone 100. It can be understood that multiple edge sub-sensing units 404 can also be connected in series, or be connected in parallel to form the edge sensing unit 402.

[0247] And in Figure 12In an embodiment where the central electrode 221 and the edge electrode 222 shown are connected in parallel, the central sensing unit 401 and the edge sensing unit 402 can also be separated respectively 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. After each central sensing sub-unit 403 is connected in series or parallel, and each edge sensing sub-unit 404 is also connected in series or parallel and then the central sensing unit 401 and the edge sensing unit 402 are connected in parallel, similar beneficial effects to those of the above embodiments can also be achieved.

[0248] The above embodiments all belong to possible implementation manners of the piezoelectric microphone 100 of the present application, and the present application will not elaborate on them one by one here.

[0249] For one embodiment, please refer to Figure 26 , and the piezoelectric microphone 100 of the present application further has a ventilation slit 26 formed in the piezoelectric film 20. The ventilation slit 26 penetrates the piezoelectric film 20 along the thickness direction of the piezoelectric film 20, thereby connecting the inner cavity 11 and the space on the other side of the piezoelectric film 20 relative to the substrate 10. When the piezoelectric microphone 100 of the present application is encapsulated on the substrate 201 of the audio pickup device 200, the ventilation slit 26 can balance the air pressure on both sides of the piezoelectric film 20, avoiding the formation of a pressure difference between the relatively closed inner cavity 11 and the outside. Since the audible working range of the piezoelectric film 20 is usually between 20 Hz and 20 kHz, and the ratio of the thickness to the diameter of the piezoelectric film is small, resulting in the piezoelectric film 20 being relatively sensitive to the pressure difference between the upper and lower sides, the ventilation slit 26 can protect the piezoelectric film 20 from cracking due to the pressure difference between the upper and lower sides during vibration.

[0250] In the planar direction of the piezoelectric film 20, the ventilation slit 26 is preferably arranged on the piezoelectric layer 21. Specifically, the ventilation slit 26 includes a first end 261 and a second end 262 that are opposite to each other along the length direction, the first end 261 is close to the geometric center of the piezoelectric film 20, and the second end 262 extends in a direction away from the geometric center relative to the first end 261. In one embodiment, the extension line of the ventilation slit 26 along its own length direction preferably also passes through the geometric center of the piezoelectric film 20, such as Figure 26 the ventilation slit 26 is arranged along the radius direction of the circular piezoelectric film 20 in

[0251] In Figure 27In the schematic diagram, the ventilation slit 26 can also extend into the edge electrode 222 and / or the central electrode 221. That is, the first end 261 of the ventilation slit 26 can extend into the central electrode 221 and form partial segmentation of the central electrode 221; the second end 262 can extend into the edge electrode 222 and form partial segmentation of the edge electrode 222. It should be noted that the second end 262 can completely penetrate the edge electrode 222. At this time, for the edge electrode 222 that is disconnected into two parts by the ventilation slit 26, the two disconnected parts can be electrically connected by means of a wire, so as to ensure the charge collection of the edge electrode 222; or as Figure 27 shown, the ventilation slit 26 is directly used to segment the edge electrode 222 to form a plurality of upper edge units 2222a, a plurality of middle edge units 2223a, and a plurality of lower edge units 2221a. The first end 261 should not extend to the geometric center position of the piezoelectric film 20, that is, the length of a single ventilation slit 26 in its extending direction is less than the distance between the geometric center of the piezoelectric film 20 and the edge in this direction. As reflected in Figure 27 the embodiment, it can be defined that the length of the ventilation slit 26 is less than the radius of the piezoelectric film 20. Such a setting can avoid damaging the structural stability of the piezoelectric film 20 when the ventilation slit 26 passes through the center of the piezoelectric film 20 and enhance the impact resistance.

[0252] In an embodiment, it is defined that the width of the ventilation slit 26 is less than or equal to 3 μm. Please refer to Figure 28 the schematic diagram. For the first end 261 and / or the second end 262, round holes 263 can also be provided at their end positions. The diameter of the round hole 263 is greater than the width of the ventilation slit 26, thereby avoiding the phenomenon of stress concentration at the first end 261 or the second end 262 and improving the service life of the piezoelectric microphone 100.

[0253] An embodiment, the number of ventilation slits 26 is at least two, and at least two ventilation slits are evenly distributed along the circumferential direction of the piezoelectric film 20. While balancing the air pressure of the piezoelectric microphone 100, the ventilation slits 26 can also play a role in releasing the internal stress of the piezoelectric film 20. 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). These materials are usually grown at temperatures higher than room temperature and are placed in an environment at room temperature for further manufacturing and assembly after growth. Due to the thermal expansion coefficient of the material itself, thermal stress will be generated. The layer structure of the electrode 22 is arranged in the piezoelectric layer 21 made of piezoelectric material, and it has a certain effect of offsetting internal stress through its own deformation. However, for some residual stresses that cannot be offset, their accumulation in the piezoelectric film 20 may cause warping and other phenomena in local areas of the piezoelectric film 20. Residual stress may cause damage to the piezoelectric layer 21 and result in the failure of the piezoelectric microphone 100. Or in extreme environments such as when the piezoelectric microphone 100 drops with an electronic device, the piezoelectric film 20 will also have a large displacement. At this time, it is also easy to cause the effect of residual stress and damage the piezoelectric layer 21.

[0254] Furthermore, since the edge of the piezoelectric film 20 is fixedly connected to the annular base 10 and only the middle region can move, its residual stress is usually distributed in an irregular state in the middle region of the piezoelectric layer 21, which easily causes the resonance frequencies of the piezoelectric film 20 to be inconsistent. Obtained through finite simulation of the piezoelectric film 20 in a possible embodiment Figure 29 The residual stress change trend diagram shows that every 1 MPa of residual stress will cause a resonance frequency drift of 2.26 KHz. After setting at least two ventilation slits 26 evenly distributed in the circumferential direction, the evenly 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 residual stress through a certain deformation.

[0255] Figure 30a and Figure 30b respectively show the stress simulation results of the piezoelectric film 20 in an embodiment of the present application and the piezoelectric microphone structure of the existing cantilever beam structure. In Figure 30a the piezoelectric film 20 of an embodiment of the present application, six evenly distributed ventilation slits 26 are provided. Under the action of the same impact force, the maximum surface displacement of the piezoelectric film 20 of the present application is controlled within 3 μm. While for the piezoelectric microphone with a cantilever beam structure in the prior art, the maximum displacement reaches 18 μm under the action of the same impact force. The stress improvement effect of the ventilation slits 26 on the piezoelectric film 20 is relatively obvious.

[0256] The ventilation slits 26 can also improve the low-frequency response ability of the piezoelectric microphone 100. Such as Figure 31As shown, under the action of the same impact force, the resonance frequency of a piezoelectric film 20 of an embodiment of the present application is significantly better than that of the structure without the ventilation slit 26 after the ventilation slit 26 is provided. And in Figure 32 In the SNR simulation schematic diagram of the piezoelectric microphone 100 shown schematically, in an embodiment of the present application, for the structure of the piezoelectric microphone 100 with the central electrode 221 and the edge electrode 222, after the ventilation slit 26 is provided, under the condition of the same bandwidth, the SNR of the piezoelectric microphone with the existing cantilever beam structure will increase by more than 2 dB.

[0257] Finally, the piezoelectric microphone 100 of the present application can be as Figure 33 shown. An insulating layer 30 is provided on the substrate 10, and a piezoelectric film 20 is provided on the insulating layer 30. The piezoelectric film 20 includes a piezoelectric layer 21 and an electrode 22. A ventilation slit 26 is provided on the piezoelectric layer 20. The electrode 22 includes a central electrode 221 and an edge electrode 222. The central electrode 221 and the edge electrode 222 are arranged at intervals, and the central electrode 221 is divided into multiple parts ( Figure 33 shown as two parts), and the edge electrode 222 is divided into multiple parts ( Figure 33 shown as six parts). A connection line 23 can also be provided between the central electrode 221 and the edge electrode 222 for realizing the electrical connection between the central electrode 221 and the edge electrode 222.

[0258] Figure 34 and Figure 35 schematically shows another piezoelectric microphone 300 involved in the present application. The usage scenario of this piezoelectric microphone 100 is the same as that of the above-mentioned piezoelectric microphone 100. Among them Figure 34 is a schematic structural diagram of another piezoelectric microphone 300 of the present application, Figure 35 is a schematic C-C cross-sectional view of the piezoelectric microphone 300 of the present application. The piezoelectric microphone 300 also includes a substrate 70, and the substrate 10 is also annular and encloses a cavity 11. The piezoelectric microphone 300 further includes a support layer 50 and a piezoelectric film layer 60. Both the support layer 50 and the piezoelectric film layer 60 are in a planar structure and simultaneously cover the substrate 10 to shield the cavity 11. The support layer 50 can be connected between the piezoelectric film layer 60 and the substrate 70, or as Figure 36 shown, the support layer 50 is provided on the side of the piezoelectric film layer 60 away from the substrate 60. And in Figure 36 the schematic piezoelectric microphone 300, an insulating layer 80 also needs to be provided between the piezoelectric film layer 60 and the substrate 60.

[0259] For the structure and material settings of the substrate 70 and the insulating layer 80 in the piezoelectric microphone 300 in this embodiment, reference can be made to the matching settings of the substrate 10 and the insulating layer 30 in the piezoelectric microphone 100. The function of the piezoelectric film layer 60 in this embodiment is similar to that of the piezoelectric film 20 in the piezoelectric microphone 100, and is also used to collect induced charges. In this embodiment, the support layer 50 is used to support the piezoelectric film layer 60 and adjust the position of the central plane B1' of the planar structure jointly formed by the piezoelectric film layer 60 and the support layer 50, so that the piezoelectric friction 60 can collect induced charges and form an induction of the sound signal. The support layer 50 can be prepared from silicon dioxide (SiO2).

[0260] The piezoelectric film layer 60 includes a piezoelectric layer 61 and a plurality of electrodes 62 disposed on the piezoelectric layer 61. The plurality of electrodes 62 includes a central electrode 621 and edge electrodes 622. The central electrode 621 and the edge electrodes 622 are also spaced apart in the planar direction of the piezoelectric film layer 60. The central electrode 621 is located at the central position of the piezoelectric film layer 60, and the edge electrodes 622 surround the periphery of the central electrode 621 and are located at the edge position of the piezoelectric film layer 60.

[0261] In the thickness direction of the piezoelectric film layer 60, the piezoelectric layer 61 has a lower surface 611 close to the cavity 11 and an upper surface 612 opposite to the lower surface 611. The central electrode 621 includes a central lower electrode 6211 close to the lower surface 611 and a central upper electrode 6212 close to the upper surface 612. The edge electrodes 622 also include an edge lower electrode 6221 close to the lower surface 611 and an edge upper electrode 6222 close to the upper surface 612. In one embodiment, the central upper electrode 6212 and the edge upper electrode 6222 are flush, and the central lower electrode 6211 and the edge lower electrode 6221 are flush. It can be understood that the central lower electrode 6211 in this embodiment can correspond to the first central electrode in the claims of this application, the central upper electrode 6212 can correspond to the second central electrode, the edge lower electrode 6221 can correspond to the first edge electrode, and the edge upper electrode 6222 can correspond to the second edge electrode.

[0262] The central lower electrode 6211 and the central upper electrode 6212 form the central induction unit 501 of the capacitive structure, and the edge lower electrode 6221 and the edge lower electrode 6222 form the edge induction unit 502 of the capacitive structure. Due to the function of the support layer 50, the central plane B1' of the planar structure jointly composed of the support layer 50 and the piezoelectric film layer 60 will shift in the direction of the support layer 50. Therefore, when the planar structure vibrates under the action of a sound signal, induced charges will be generated on the central induction unit 501 and the edge induction unit 502. At this time, by connecting the central induction unit 501 and the edge induction unit 502 in series and then connecting them to the backend post-processing circuit 202, the functions of charge collection and electrical signal conversion can also be realized.

[0263] It can be understood that during the vibration of the piezoelectric film layer 60, the stress directions generated in its central region and edge region are opposite, so the voltage V1' of the central induction unit 501 is also opposite to the voltage V2' of the edge induction unit 502. During the process of connecting the central induction unit 501 and the second induction voltage 502 in series, reference can be made to Figure 37 for the schematic diagram:

[0264] A first connection end 641 is led out from the central upper electrode 6212 of the central induction unit 501, then the central lower electrode 6211 of the central induction unit 501 is connected to the edge lower electrode 6221 of the edge induction unit 502, and finally a second connection end 642 is led out from the edge upper electrode 6222 of the edge induction unit 502. The first connection end 641 and the second connection end 642 are respectively connected to the backend post-processing circuit 202 to obtain the output voltage V' and output capacitance C' of the piezoelectric microphone 300.

[0265] Of course, the first connection end 641 and the second connection end 642 can also be respectively led out from the central lower electrode 6211 and the edge lower electrode 6221, and at the same time, the central upper electrode 6212 and the edge upper electrode 6222 are connected, which can also achieve the same effect. A connection line 63 is also provided in the piezoelectric film layer 60 (see Figure 42 ), and further vias (not shown in the figure) can be provided to realize the internal connection conduction of the electrode 62 and the function of leading out the connection end. It can be understood that the vias can be led out from the side of the piezoelectric film layer 60 or from the side of the support layer 50.

[0266] In the piezoelectric microphone 300 of the present application, since the central electrode 621 and the edge electrode 622 respectively cover the central region and the edge region of the piezoelectric layer 61, the electrode 62 can collect induced charges in the effective region where the stress is relatively concentrated in the piezoelectric layer 61, and through the series connection of the central induction unit 501 and the edge induction unit 502, the output voltage V' is increased on the basis of meeting the charge requirement, thereby achieving the effect of improving the sensitivity of the piezoelectric microphone 300.

[0267] Please refer to Figure 38 For the schematic diagram in Figure 38 , in one embodiment, the central electrode 621 can also be cut to form a central sub-induction unit 503 composed of a plurality of central upper units 6212a and a plurality of central lower units 6211a. A plurality of central sub-induction units 503 form a central induction unit 501. At this time, the plurality of central sub-induction units 503 are also connected in series, and then connected in series with the edge induction unit 502, so as to achieve a larger output voltage V'. For the specific connection schematic diagram, please refer to Figure 39 the schematic diagram in Figure 39 . It can be understood that the central lower unit 6211a in this embodiment can correspond to the first central sub-electrode in the claims, and the central upper unit 6212a can correspond to the second central sub-electrode.

[0268] For another embodiment, please refer to Figure 40 Figure 40 , the edge electrode 622 is cut to form an edge sub-induction unit 504 composed of a plurality of edge upper units 6222a and a plurality of edge lower units 6221a. A plurality of edge sub-induction units 504 form an edge induction unit 502. At this time, the plurality of edge sub-induction units 504 are also connected in series, and then connected in series with the central induction unit 501, and the effect of achieving a larger output voltage V' is also achieved. For the specific connection schematic diagram, please refer to Figure 41 the schematic diagram in Figure 41 . It can be understood that the edge lower unit 6221a in this embodiment can correspond to the first edge sub-electrode in the claims, and the edge upper unit 6212a can correspond to the second edge sub-electrode.

[0269] For yet another embodiment, please refer to Figure 42 Figure 42 , while dividing the central induction unit 501 into M central sub-induction units 503, the edge induction unit 502 is divided into N edge sub-induction units 504. At this time, as shown in Figure 43 Figure 43 , after cross-connecting each central sub-induction unit 503 with each edge sub-induction unit 504, the remaining central sub-induction units 503 or edge sub-induction units 504 are connected in series to obtain the effect of a larger output voltage V'; it can also be as shown in Figure 44 Figure 44 , after connecting the M central sub-induction units 503 in series in sequence, and then connecting the N edge sub-induction units 504 in series in sequence, the effect similar to that of the Figure 41 embodiment in Figure 41 can be achieved.

[0270] In an embodiment, when the distance from the center of the piezoelectric layer 61 to the edge in any direction is L', the first dimension L1' of the center electrode 621 in this direction also needs to satisfy the condition: 50% * L' ≥ L1' ≥ 5% * L'. Preferably, it can be further limited that 40% * L' ≥ L1' ≥ 20% * L'; and for the edge electrode 622 in this direction, the second dimension L2' from its inner edge to the outer edge also needs to be less than or equal to 50% * L' and greater than or equal to 5% * L'. Preferably, it can be further limited that 30% * L' ≥ L2' ≥ 10% * L'.

[0271] In an embodiment, the shape of the center electrode 621 and / or the edge electrode 622 can also be an axisymmetric shape or a centrosymmetric shape, and the shapes of the center electrode 621 and the edge electrode 622 can be the same or different.

[0272] Please refer to Figure 45 the embodiment of. In the piezoelectric microphone 300 of the present application, an air vent slit 66 can also be provided to connect the inner cavity 11 and the space on the other side of the piezoelectric film layer 60 relative to the substrate 70. Due to the setting of the support layer 50, the air vent slit 66 needs to penetrate through the piezoelectric film layer 60 and the support layer 50 simultaneously in the thickness direction of the piezoelectric film layer 60. The air vent slit 66 can also play a role in balancing the pressure difference inside and outside the inner cavity 11 and improving the structural stability of the piezoelectric film layer 60.

[0273] Furthermore, the air vent slit 66 is also preferably set to at least two, and at least two air vent slits 66 are circumferentially distributed on the piezoelectric layer 61 in the plane direction of the piezoelectric film layer 60. The air vent slit 66 also includes a first end 661 close to the geometric center of the piezoelectric film layer 60 and a second end 662 extending in a direction away from the geometric center of the piezoelectric film layer 60 relative to the first end 661. In an embodiment, the extension direction of the second end 662 from the first end 661 passes through the geometric center of the piezoelectric film layer 60.

[0274] In an embodiment, the first end 661 can also extend into the center electrode 621, but the first end 661 is not preferably extended to the geometric center position of the piezoelectric film layer 60; the second end 662 can also extend into the edge electrode 622, and the second end 662 can also directly extend into the outer edge of the edge electrode 622.

[0275] In an embodiment, the width of the air vent slit 66 is less than or equal to 3 μm. In an embodiment, at the first end 661 and / or the second end 662, round holes (not shown in the figure) can also be provided. The diameter of the round hole is greater than the width of the air vent slit 66 to avoid stress concentration at the first end 661 or the second end 662.

[0276] The above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application can easily think of changes or substitutions, such as reducing or adding structural members, changing the shape of structural members, etc., which should all be covered within the protection scope of the present application; without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A piezoelectric microphone, characterized in that, It includes a substrate and a piezoelectric film. The substrate is annular and defines an inner cavity, and the piezoelectric film is fixed to one side of the substrate to shield the inner cavity; The piezoelectric film includes a piezoelectric layer, a central electrode, and an edge electrode. The piezoelectric layer is laid in the planar direction of the piezoelectric film. The central electrode is fixed in the middle of the piezoelectric layer, and the edge electrode is fixed at the periphery of the piezoelectric layer; In the thickness direction of the piezoelectric film, the central electrode includes a first central electrode, a second central electrode, and a third central electrode that are spaced apart from each other. The third central electrode is located 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 induction unit; The edge electrode includes a first edge electrode, a second edge electrode, and a third edge electrode that are spaced apart from each other. The third edge electrode is located 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 induction unit; An air vent slit is further provided on the piezoelectric layer, and the air vent slit penetrates the piezoelectric film in the thickness direction of the piezoelectric film; The air vent slit includes a first end and a second end that are opposite to each other in the length direction. The first end is close to the geometric center of the piezoelectric film, and the second end completely penetrates the edge electrode, so that 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, and 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; 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 third sub-capacitor and one fourth sub-capacitor are connected in parallel to form an edge sub-induction unit; Multiple edge sub-induction units are connected in series to form the edge induction unit; The central induction unit is electrically connected to the edge induction unit to output the induction signal of the piezoelectric microphone.

2. The piezoelectric microphone according to claim 1, wherein In any direction on the plane of the piezoelectric film, the geometric center of the piezoelectric layer is at a first distance L from the edge of the piezoelectric layer, and the geometric center of the central electrode is at a first dimension L1 from the edge of the central electrode, and the first dimension L1 satisfies the condition: L*50%≥L1≥L*5%; 3. The piezoelectric microphone according to claim 1, characterized in that, In the thickness direction of the piezoelectric film, 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.

4. The piezoelectric microphone according to claim 1, characterized in that, In any direction on the plane of the piezoelectric film, the geometric center of the piezoelectric layer is at a first distance L from the edge of the piezoelectric layer, the inner edge of the edge electrode is at a second dimension L2 from the outer edge of the edge electrode, and the second dimension L2 satisfies the condition: L * 50% ≥ L2 ≥ L * 5%.

5. The piezoelectric microphone according to claim 1, characterized in that, In the thickness direction of the piezoelectric film, the first central electrode is flush with the first edge electrode, the second central electrode is flush with the second edge electrode, and the third central electrode is flush with the third edge electrode.

6. The piezoelectric microphone according to claim 1, characterized in that, 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 second central sub - electrodes, and the third central sub - electrodes is 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 first sub - capacitor and one second sub - capacitor are connected in parallel to form a central sub - sensing unit; Multiple central sub - sensing units are connected in series to form the central sensing unit.

7. The piezoelectric microphone according to claim 6, characterized in that, In the thickness direction of the piezoelectric film, the projection of one of the first central sub - electrodes on the corresponding second central sub - electrode coincides with the outer shape of the second central sub - electrode, and the projection of one of the third central sub - electrodes on the corresponding second central sub - electrode also coincides with the outer shape of the second central sub - electrode.

8. The piezoelectric microphone according to claim 6, wherein, The shapes and areas of the at least two first central sub - electrodes are the same.

9. The piezoelectric microphone according to claim 1, characterized in that, In the thickness direction of the piezoelectric film, the projection of one of the first edge sub - electrodes on the corresponding second edge sub - electrode coincides with the outer shape of the second edge sub - electrode, and the projection of one of the third edge sub - electrodes on the corresponding second edge sub - electrode also coincides with the outer shape of the second edge sub - electrode.

10. The piezoelectric microphone according to claim 1, characterized in that, The shapes and areas of the at least two first edge sub - electrodes are the same.

11. The piezoelectric microphone according to claim 6, wherein, The central sub - sensing unit and the edge sensing unit are electrically connected through a connecting wire.

12. The piezoelectric microphone according to claim 1, characterized in that, The ventilation slit includes opposite first and second ends along its own length direction, and the extension line from the second end to the first end passes through the geometric center of the piezoelectric film.

13. The piezoelectric microphone according to claim 1, characterized in that, The piezoelectric film includes multiple ventilation slits, and the multiple ventilation slits are evenly distributed along the circumferential direction of the piezoelectric film.

14. The piezoelectric microphone according to claim 1, characterized in that, The width of the ventilation slit is less than or equal to 3μm.

15. The piezoelectric microphone according to any one of claims 1 to 14, characterized in that, The central sensing unit and the edge sensing unit are connected in series to output the sensing signal of the piezoelectric microphone.

16. The piezoelectric microphone according to any one of claims 1 to 14, characterized in that, The main material of the base is a silicon wafer, and an insulating member is further provided between the base and the piezoelectric film. The insulating member is annular, and the shape of the insulating member matches the shape of the base.

17. A piezoelectric microphone, characterized in that, It includes a base, a piezoelectric film, and a support layer. The base is annular and encloses an inner cavity. The piezoelectric film and the support layer are stacked, and both the piezoelectric film and the support layer are fixed on one side of the base to shield the inner cavity; The piezoelectric film includes a piezoelectric layer, a central electrode, and an edge electrode. The piezoelectric layer is laid in the planar direction of the piezoelectric film. The central 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 includes a first central electrode and a second central electrode that are spaced apart from each other. The first central electrode and the second central electrode form a central induction unit of a capacitive structure; The edge electrode includes a first edge electrode and a second edge electrode that are spaced apart from each other. The first edge electrode and the second edge electrode form an edge induction unit of a capacitive structure; An air vent slit is further provided on the piezoelectric layer, and the air vent slit penetrates the piezoelectric film in the thickness direction of the piezoelectric film; The air vent slit includes a first end and a second end that are opposite to each other in the length direction. The first end is close to the geometric center of the piezoelectric film, and the second end completely penetrates the edge electrode, so that the first edge electrode is divided into at least two first edge sub-electrodes, and the second edge electrode is divided into at least two second edge sub-electrodes, and the number of the first edge sub-electrodes is equal to the number of the second edge sub-electrodes; One of the first edge sub-electrodes and one of the second edge sub-electrodes form an edge sub-induction unit of a capacitive structure; A plurality of the edge sub-induction units are connected in series to form the edge induction unit; The central induction unit and the edge induction unit are connected in series to output the induction signal of the piezoelectric microphone.

18. The piezoelectric microphone according to claim 17, characterized in that, In any direction on 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, and the geometric center of the central electrode has a first dimension L1' from the edge of the central electrode, and the first dimension L1' satisfies the condition: L' * 50% ≥ L1' ≥ L' * 5%; 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: L' * 50% ≥ L2' ≥ L' * 5%.

19. The piezoelectric microphone according to claim 17, characterized in that, In the thickness direction of the piezoelectric film, the first central electrode is flush with the first edge electrode, and the second central electrode is flush with the second edge electrode.

20. The piezoelectric microphone according to claim 17, wherein, The first central electrode is divided into at least two first central sub-electrodes, and 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 of the first central sub-electrodes and one of the second central sub-electrodes form a central sub-induction unit of a capacitive structure; A plurality of the central sub-induction units are connected in series to form the central induction unit.

21. The piezoelectric microphone according to claim 20, wherein, In the thickness direction of the piezoelectric film, the projection of one of the first central sub-electrodes on the corresponding second central sub-electrode coincides with the outer shape of the second central sub-electrode; and / or The projection of one of the first edge sub-electrodes on the corresponding second edge sub-electrode coincides with the outer shape of the second edge sub-electrode.

22. The piezoelectric microphone according to claim 17, wherein, The air vent slit penetrates the support layer simultaneously in the thickness direction of the piezoelectric film.

23. The piezoelectric microphone according to claim 17, wherein, The piezoelectric film includes a plurality of the ventilation slits, and the plurality of ventilation slits are uniformly distributed along the circumferential direction of the piezoelectric film.

24. The piezoelectric microphone according to claim 22, characterized in that, The support layer is located between the piezoelectric film and the substrate, and the main material of the support layer is an insulating material.

25. The piezoelectric microphone according to any one of claims 17 to 23, characterized in that, The piezoelectric film is located between the support layer and the substrate. The main material of the substrate is a silicon wafer. An insulating member is further provided 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.

26. An electronic device, characterized in that, It includes an audio pickup device, and the audio pickup device includes a substrate, a post-processing circuit, and a piezoelectric microphone according to any one of claims 1 to 25. The substrate is provided with a sound inlet hole, and the sound inlet hole communicates with the inner cavity of the substrate in the piezoelectric microphone. The post-processing circuit is electrically connected to the piezoelectric microphone, and the post-processing circuit is used to process the induction signal of the piezoelectric microphone.

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