WO2024140310A1 - Piezoelectric diaphragm, piezoelectric transducer and preparation method, sound-emitting apparatus, and electronic device - Google Patents

Abstract

A piezoelectric diaphragm (200), a piezoelectric transducer and a preparation method, a sound-emitting apparatus, and an electronic device. The piezoelectric diaphragm (200) comprises a first piezoelectric layer (210) and a second piezoelectric layer (220), which covers one side of the first piezoelectric layer (210), wherein the lower surface of the first piezoelectric layer (210) is provided with a first electrode (230), the upper surface of the second piezoelectric layer (220) is provided with a third electrode (250), and a second electrode (240) is provided between the first piezoelectric layer (210) and the second piezoelectric layer (220); and in a projection direction, the first electrode (230) and the third electrode (250) are respectively disposed on two sides of the second electrode (240) and are both arranged in a manner of being staggered with the second electrode (240). The piezoelectric diaphragm (200) is a base-free composite film structure of a double-layer piezoelectric material and a three-layer electrode material, solves the problem of the flatness and performance of diaphragms being poor, and significantly reduces a driving voltage and a power compared with a design with a base.

Description

Piezoelectric diaphragm, piezoelectric transducer and preparation method, sound-generating device and electronic equipment

This disclosure claims the priority of the Chinese patent application filed with the China Patent Office on December 28, 2022, with application number 202211692977.5, and application name “Piezoelectric diaphragm, piezoelectric transducer and preparation method, sound-generating device and electronic device”, all contents of which are incorporated by reference in this disclosure.

Technical Field

The present application relates to the technical field of acoustic-electric transduction, and more specifically, to a piezoelectric diaphragm, a piezoelectric transducer and a preparation method, a sound-generating device and an electronic device.

Background technique

MEMS piezoelectric transducers are micro-electromechanical devices, which have been widely used in mobile communication devices, computers, medical electronic equipment and other electronic products in recent years. MEMS piezoelectric transducers use diaphragms to sense surrounding sound vibrations and then convert the vibrations into electrical signals.

The diaphragm in a conventional MEMS piezoelectric transducer is mainly composed of a base layer (Base) and a piezoelectric layer (PE). Generally, the thickness and mechanical strength of the base layer are higher than those of the piezoelectric layer. The driving aspect requires a higher voltage and power, a large part of which is consumed on the base layer. This results in excessive power consumption of existing MEMS piezoelectric transducers, which may even exceed traditional dynamic drives. Existing MEMS piezoelectric transducers are based on a structural design in which a single layer of piezoelectric film and a single layer of interdigital electrodes (IDTs) are superimposed on the base layer. There is also the problem that the dispersion and instability of the stress of the piezoelectric film lead to poor flatness and mechanical strength of the diaphragm.

Summary of the invention

The purpose of this application is to provide a new technical solution for a piezoelectric diaphragm, a piezoelectric transducer and a preparation method, a sound-generating device and an electronic device.

In a first aspect, an embodiment of the present application provides a piezoelectric diaphragm. The piezoelectric diaphragm includes a first piezoelectric layer and a second piezoelectric layer covering one side of the first piezoelectric layer, a first electrode is provided on the lower surface of the first piezoelectric layer, a third electrode is provided on the upper surface of the second piezoelectric layer, and a second electrode is provided between the first piezoelectric layer and the second piezoelectric layer;

In the projection direction, the first electrode and the third electrode are respectively arranged on both sides of the second electrode, and are respectively arranged in a staggered manner with respect to the second electrode.

Optionally, the first electrode and the third electrode include a first bus electrode and a A plurality of first interdigitated electrodes on one side of the first bus electrode;

The third electrode includes a third bus electrode and a plurality of third interdigital electrodes disposed on one side of the third bus electrode;

The second electrode includes a second bus electrode and a plurality of second interdigitated electrodes symmetrically arranged on both sides of the second bus electrode;

In the projection direction, the first interdigital electrodes and the third interdigital electrodes are arranged in a one-to-one correspondence, and are respectively arranged in a staggered manner with the second interdigital electrodes to form a fork structure.

Optionally, when a first voltage V1 is applied to the first electrode, a second voltage V2 is applied to the second electrode, and a third voltage V3 is applied to the third electrode, and V3>V2, V1<V2, the electric field between the third electrode and the second electrode is consistent with the polarization direction, and the electric field between the first electrode and the second electrode is opposite to the polarization direction.

Optionally, the second electrode is grounded, and a first voltage V1 is applied to the first electrode, and a third voltage V3 is applied to the third electrode, and when V1<0 and V3>0, the electric field between the third electrode and the second electrode is consistent with the polarization direction, and the electric field between the first electrode and the second electrode is opposite to the polarization direction.

Optionally, the piezoelectric diaphragm has a plurality of slits, and each of the slits penetrates the piezoelectric diaphragm in a thickness direction, and is configured to be able to divide the piezoelectric diaphragm into a plurality of diaphragm petals.

Optionally, the piezoelectric diaphragm is a rectangular or square cantilever diaphragm, comprising a first region and a second region located side by side on one side of the first region, and the slit extends in a horizontal direction from one side edge of the piezoelectric diaphragm to another side edge opposite to the side, so as to divide the piezoelectric diaphragm into a plurality of parallel long strip-shaped diaphragm petals;

The first electrode, the second electrode and the third electrode are layered in the second region along the thickness direction. In the projection direction, the first electrode and the third electrode are distributed in a mirror-symmetrical manner with respect to the second electrode.

Optionally, the first electrode includes a first bus electrode and a plurality of first interdigital electrodes vertically arranged on one side of the first bus electrode;

The second electrode includes a second bus electrode and a plurality of second interdigitated electrodes vertically arranged on both sides of the second bus electrode;

The third electrode includes a third bus electrode and a plurality of third interdigital electrodes vertically arranged on one side of the third bus electrode;

In the projection direction, the first bus electrode and the third bus electrode are located on both sides of the second bus electrode, and the first bus electrode, the second bus electrode and the third bus electrode are all straight and parallel to each other; the first interdigitated electrode and the third interdigitated electrode are arranged in a one-to-one correspondence and are staggered with the second interdigitated electrode, respectively, and the first interdigitated electrode, the second interdigitated electrode and the third interdigitated electrode are all straight.

Optionally, the piezoelectric diaphragm is a rectangular or square cantilever diaphragm, comprising a first area and a second area surrounding the first area; the slit extends from the edge of the piezoelectric diaphragm toward the center in the horizontal direction, so as to divide the piezoelectric diaphragm into a plurality of triangular diaphragm petals;

The first electrode, the second electrode and the third electrode are layered and arranged in the second region along the thickness direction;

In the projection direction, each of the membrane petals has two first electrodes located on both sides that are mirror-symmetrical along the central axis, two third electrodes located in the middle that are mirror-symmetrically arranged are located between the two first electrodes, and between each first electrode and the adjacent third electrode is the second electrode, and the two second electrodes are mirror-symmetrical structures.

Optionally, the first electrode includes a first bus electrode and a plurality of first interdigitated electrodes disposed on one side of the first bus electrode;

The second electrode includes a second bus electrode and a plurality of second interdigitated electrodes disposed on both sides of the second bus electrode;

The third electrode includes a third bus electrode and a plurality of third interdigital electrodes disposed on one side of the third bus electrode;

In the projection direction, the first bus electrode and the third bus electrode are located on both sides of the second bus electrode, and the first bus electrode, the second bus electrode and the third bus electrode are all straight lines, wherein the first bus electrode is inclined along the side of the membrane flap, the second bus electrode is inclined at a set angle relative to the first bus electrode, and the third bus electrode is vertically arranged; the first interdigitated electrode and the third interdigitated electrode are arranged in a one-to-one correspondence and are staggered with the second interdigitated electrode, respectively, and the first interdigitated electrode, the second interdigitated electrode and the third interdigitated electrode are all straight lines.

Optionally, the piezoelectric diaphragm is a circular cantilever diaphragm, comprising a first region and a second region surrounding the periphery of the first region; the slit extends from the edge of the piezoelectric diaphragm toward the center in the horizontal direction, so as to divide the piezoelectric diaphragm into a plurality of fan-shaped diaphragm petals;

The first electrode, the second electrode and the third electrode are layered in the second region along the thickness direction. In the projection direction, the first electrode and the third electrode are distributed in a mirror-symmetrical manner with respect to the second electrode.

Optionally, the first electrode includes a first bus electrode and a plurality of first interdigitated electrodes disposed on one side of the first bus electrode;

The second electrode includes a second bus electrode and a plurality of second interdigitated electrodes disposed on both sides of the second bus electrode;

The third electrode includes a third bus electrode and a plurality of third interdigital electrodes disposed on one side of the third bus electrode;

In the projection direction, the first bus electrode and the third bus electrode are located at the On both sides of the second bus electrode, the first bus electrode, the second bus electrode and the third bus electrode are all straight lines, wherein the first bus electrode and the third bus electrode are respectively arranged obliquely along the side of each of the membrane petals; the first interdigitated electrode and the third interdigitated electrode are arranged in a one-to-one correspondence and are respectively staggered with the second interdigitated electrode, and the first interdigitated electrode, the second interdigitated electrode and the third interdigitated electrode are all arc-shaped.

Optionally, the first piezoelectric layer and the second piezoelectric layer have the same thickness, which is 0.5 μm to 2 μm.

In a second aspect, an embodiment of the present application provides a piezoelectric transducer. The piezoelectric transducer comprises:

a substrate having a back cavity; and

The piezoelectric diaphragm as described in any one of the first aspects, wherein the piezoelectric diaphragm is disposed on one side of the substrate and covers the back cavity;

The first piezoelectric layer faces the substrate, a dielectric layer is provided between the substrate and the first piezoelectric layer, and a region of the dielectric layer opposite to the back cavity is a hollow region.

In a third aspect, an embodiment of the present application provides a method for preparing a piezoelectric transducer as described in the second aspect, the method comprising:

Providing a substrate, covering a dielectric layer on one side of the substrate, and forming a first electrode on the dielectric layer;

Covering the first electrode with a first piezoelectric layer, and forming a second electrode on a surface of the first piezoelectric layer facing away from the first electrode;

Covering the second electrode with a second piezoelectric layer, and forming a third electrode on a surface of the second piezoelectric layer away from the second electrode, so as to obtain a piezoelectric diaphragm;

A through hole is formed at the center of the piezoelectric diaphragm along the thickness direction, and a partial area of the first electrode, the second electrode and the third electrode is exposed by etching;

Disposing an electrical connection structure in the area where the first electrode, the second electrode, and the third electrode are exposed; and

A back cavity is formed on a side of the substrate away from the piezoelectric diaphragm, and a region on the dielectric layer opposite to the back cavity is removed to form a hollow region.

Optionally, the first electrode, the second electrode and the third electrode are formed by first depositing a metal film, and then photolithography and etching to form a set electrode pattern;

The thickness of the metal film is smaller than the thickness of any one of the first piezoelectric layer and the second piezoelectric layer, and the thickness of the first piezoelectric layer and the second piezoelectric layer is controlled to be 0.5 μm to 2 μm.

Optionally, the preparation method further comprises: dividing the piezoelectric diaphragm into a plurality of membrane petals, and making each of the membrane petals have one end fixed to the substrate and the other end suspended above the substrate.

In a fourth aspect, an embodiment of the present application provides a sound-generating device. The sound-generating device comprises:

A packaging structure, wherein a sound hole is provided on the packaging structure; and

At least one piezoelectric transducer as described in the third aspect, wherein the piezoelectric transducer is disposed in the packaging structure.

Optionally, the packaging structure includes a base and a shell, and the shell cover is disposed on the base and encloses the base to form a receiving cavity;

The sound hole is located on the shell and communicated with the accommodating cavity; the side of the substrate away from the piezoelectric diaphragm is arranged on the base, and a through hole communicating with the back cavity is opened on the base.

In a fifth aspect, an embodiment of the present application provides an electronic device, wherein the electronic device comprises the sound-generating device as described in the fourth aspect.

The beneficial effects of this application are:

The embodiment of the present application provides a piezoelectric diaphragm, which is a composite membrane structure of a double-layer piezoelectric material and a three-layer electrode material without a base layer. The problem of diaphragm flatness and poor performance caused by stress gradient is improved by adopting a symmetrical design in the thickness direction; the dual piezoelectric layer design provides bipolar drive and sensor differential signal output, thereby improving the device sensitivity; because the piezoelectric diaphragm does not contain a base layer, but only has a piezoelectric layer and an electrode, it is easy to control the unevenness of the piezoelectric diaphragm, inconsistent performance and yield loss caused by mass production stress and dispersion; the driving voltage and power are greatly reduced compared to the design with a base layer.

Other features and advantages of the present application will become apparent from the following detailed description of exemplary embodiments of the present application with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the application and, together with the description, serve to explain the principles of the application.

FIG1 is a top view of a piezoelectric diaphragm according to an embodiment of the present application;

FIG2 is a side view of a piezoelectric diaphragm according to an embodiment of the present application;

FIG3 is a schematic diagram of the working principle of driving the piezoelectric diaphragm according to an embodiment of the present application;

FIG4 is a schematic diagram of the working principle of the piezoelectric diaphragm according to an embodiment of the present application;

FIG5 is a schematic diagram of the structure of a piezoelectric diaphragm according to an embodiment of the present application;

FIG6 is a second schematic diagram of the structure of the piezoelectric diaphragm according to an embodiment of the present application;

FIG7 is a third schematic diagram of the structure of the piezoelectric diaphragm according to an embodiment of the present application;

FIG8 is a flow chart of a method for preparing a piezoelectric transducer according to an embodiment of the present application;

FIG9 is a schematic diagram of a structure of a sound-generating device according to an embodiment of the present application;

FIG10 is a second structural schematic diagram of the sound-generating device according to an embodiment of the present application;

FIG. 11 is a third schematic diagram of the structure of the sound-generating device according to an embodiment of the present application.

Description of reference numerals:
100, substrate; 110, back cavity; 200, piezoelectric diaphragm; 201, membrane petal; 202, first region;
203, second region; 210, first piezoelectric layer; 220, second piezoelectric layer; 230, first electrode; 240, second electrode; 250, third electrode; 260, electrical connection structure; 270, slit; 280, through hole; 300, dielectric layer; 400, packaging structure; 410, substrate; 411, through hole; 420, housing; 421, acoustic hole; 430, accommodating cavity; 500, ASIC chip.

Detailed ways

Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangement of components and steps, numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present application.

The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the present application, its application, or uses.

Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered as part of the specification.

In all examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

The piezoelectric diaphragm, piezoelectric transducer and preparation method, sound-generating device and electronic device provided in the embodiments of the present application are described in detail below in conjunction with the accompanying drawings.

According to one aspect of the embodiments of the present application, a piezoelectric diaphragm is provided, which can be applied to a MEMS piezoelectric transducer. The MEMS piezoelectric transducer is a micro-electromechanical device, which can be a mechanical sensor.

MEMS technology is an industrial technology that combines microelectronics and micromechanical engineering. The size of MEMS devices is usually less than a few millimeters, and its internal structure is generally in the micrometer or even nanometer range. Here, mechanical sensors are sensors that can detect changes caused by mechanical effects. For example, the mechanical effects here include sound pressure, air pressure, acceleration, deformation caused by stress due to temperature changes, deformation caused by stress due to humidity changes, etc.

The present application embodiment provides a piezoelectric diaphragm 200, as shown in FIG. 1 and FIG. 2, including a first piezoelectric layer 210 and a second piezoelectric layer 220 covering one side of the first piezoelectric layer 210, wherein a first electrode 230 is provided on the lower surface of the first piezoelectric layer 210, and a first electrode 230 is provided on the upper surface of the second piezoelectric layer 220. A third electrode 250 is provided on the surface, and a second electrode 240 is provided between the first piezoelectric layer 210 and the second piezoelectric layer 220;

In the projection direction, the first electrode 230 and the third electrode 250 are respectively disposed on both sides of the second electrode 240 , and are respectively arranged in a staggered manner with respect to the second electrode 240 .

In an embodiment of the present application, the piezoelectric diaphragm 200 does not contain a base layer, and is a composite membrane structure formed by two piezoelectric layers and three electrodes. Specifically, referring to Figures 1 and 2, the thickness of the first piezoelectric layer 210 and the second piezoelectric layer 220 can be designed to be the same, and a first electrode 230, a second electrode 240 and a third electrode 250 are arranged in three layers along the thickness direction; wherein the structures of the first electrode 230 and the third electrode 250 can be the same, for example, both are comb-tooth structures, and more importantly, the orthographic projections of the two on the interface of the two piezoelectric layers (i.e., the first piezoelectric layer 210 and the second piezoelectric layer 220) are staggered about the second electrode 240. The entire piezoelectric diaphragm 200 can form a symmetrical structure in the thickness direction (or longitudinal direction).

The piezoelectric diaphragm 200 will deform under the effect of external sound pressure and sense the sound pressure signal.

Optionally, the first piezoelectric layer 210 and the second piezoelectric layer 220 included in the piezoelectric diaphragm 200 may also be designed to be made of the same piezoelectric material. This, combined with the above-mentioned design of the same thickness, is more conducive to forming a symmetrical structure of the piezoelectric diaphragm 200 in the thickness direction without increasing the difficulty of production.

The first piezoelectric layer 210 and the second piezoelectric layer 220 may be made of piezoelectric material.

The piezoelectric material may be, for example, an AlN-type (specifically, AlN, ScAlN, AlYbN, YInN, etc.) piezoelectric material. Of course, the piezoelectric material may also be a PZT-type (specifically, PZT, PMN-PT, etc.) piezoelectric material. The piezoelectric material may also be a material such as ZnO, which is not limited in the embodiments of the present application.

Optionally, in an embodiment of the present application, the first piezoelectric layer 210 and the second piezoelectric layer 220 may be formed by at least one of sputtering, metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE) and sol-gel spin coating, which is not limited in the embodiment of the present application.

Optionally, the first piezoelectric layer 210 and the second piezoelectric layer 220 are formed by the same process, which can simplify the production process.

In an embodiment of the present application, the formed piezoelectric diaphragm 200 needs to be polarized. Specifically, under an electric field higher than the coercive electric field (such as the first electrode 230 and the third electrode 250 are both high voltage V1, and the second electrode 240 is low voltage V2), this process may be accompanied by an increase in temperature. During the polarization process, the bias voltage/electric field direction E applied to the piezoelectric diaphragm 200 may be the same as or opposite to the polarization direction Pr (the X-axis direction shown in FIG. 2) to generate positive strain or negative strain in the D33 mode, S3 = D33*E3 (here Sx = D33*Ex), where typically D33>0 (D31<0).

In addition, referring to FIG. 3 and FIG. 4 , it can be seen that the piezoelectric diaphragm 200 of the embodiment of the present application includes The dual piezoelectric layer includes a first piezoelectric layer 210 and a second piezoelectric layer 220. The dual piezoelectric layer design can provide a bipolar driving voltage, for example, can be driven in the ±Z axis direction.

An embodiment of the present application provides a piezoelectric diaphragm, which is a composite membrane structure of a double-layer piezoelectric material and a three-layer electrode material without a base layer. The problem of diaphragm flatness and poor performance caused by stress gradient is improved by adopting a symmetrical design in the thickness direction; the dual piezoelectric layers provide bipolar drive and sensor differential signal output, thereby improving the device sensitivity; since the piezoelectric diaphragm does not contain a base layer, but only has a piezoelectric layer and an electrode, it is easy to control the unevenness of the piezoelectric diaphragm, inconsistent performance and yield loss caused by mass production stress and dispersion; the driving voltage and power are greatly reduced compared to the design with a base layer.

In some examples of the present application, referring to FIG1 , the first electrode 230 and the third electrode 250 include a first bus electrode and a plurality of first interdigitated electrodes disposed on one side of the first bus electrode; the third electrode 250 includes a third bus electrode and a plurality of third interdigitated electrodes disposed on one side of the third bus electrode; the second electrode 240 includes a second bus electrode and a plurality of second interdigitated electrodes symmetrically disposed on both sides of the second bus electrode; in the projection direction, the first interdigitated electrodes and the third interdigitated electrodes are arranged one by one, and are staggered with the second interdigitated electrodes to form a fork structure.

In the embodiment of the present application, the first electrode 230 and the third electrode 250 are, for example, comb-shaped electrode patterns, that is, a plurality of interdigitated electrodes are formed on one side of a bus electrode. The electrode pattern shape of the second electrode 240 is different from that of the first electrode 230 and the third electrode 250, and a plurality of interdigitated electrodes are symmetrically arranged on both sides of a bus electrode.

Specifically, the first electrode 230, the second electrode 240 and the third electrode 250 form a staggered arrangement in the thickness direction of the piezoelectric diaphragm 200. Among them, the second electrode 240 is located on the interface between the first piezoelectric layer 210 and the second piezoelectric layer 220, the first electrode 230 is located on the first piezoelectric layer 210, and the third electrode 250 is located on the second piezoelectric layer 220. In terms of distribution, the first interdigitated electrode of the first electrode 230 and the third interdigitated electrode of the third electrode 250 are respectively staggered with the orthographic projection of the second interdigitated electrode of the second electrode 240 in the thickness direction of the piezoelectric diaphragm 200. In this way, the problem of low overall flatness and performance consistency of the piezoelectric diaphragm 200 caused by stress gradient can be improved.

In some examples of the present application, referring to FIG3 , when a first voltage V1 is applied to the first electrode 230, a second voltage V2 is applied to the second electrode 240, and a third voltage V3 is applied to the third electrode 250, and V3>V2, V1<V2, the electric field between the third electrode 250 and the second electrode 240 is consistent with the polarization direction, and the electric field between the first electrode 230 and the second electrode 240 is opposite to the polarization direction.

Optionally, when a first voltage V1 is applied to the first electrode 230, a second voltage V2 is applied to the second electrode 240, and a third voltage V3 is applied to the third electrode 250, and V3<V2, V1>V2, the electric field between the third electrode 250 and the second electrode 240 is equal to the voltage between the electrodes. The polarization direction is opposite to that of the first electrode 230 and the second electrode 240, and the electric field between the first electrode 230 and the second electrode 240 is consistent with the polarization direction.

It should be noted that both the first electrode 230 and the third electrode 250 are comb-tooth structures. In specific use, the first electrode 230 can be directed toward the substrate in the MEMS piezoelectric transducer, or the third electrode 250 can be directed toward the substrate in the MEMS piezoelectric transducer. This is not limited in the present application.

3 , when the piezoelectric diaphragm 200 moves downward, the second piezoelectric layer 220 may have tensile stress, while the first piezoelectric layer 210 has compressive properties. Conversely, when the piezoelectric diaphragm 200 moves upward, the first piezoelectric layer 210 has tensile stress, while the second piezoelectric layer 220 has compressive properties.

In some examples of the present application, referring to FIG. 4 , the second electrode 240 is grounded, and a first voltage V1 is applied to the first electrode 230, and a third voltage V3 is applied to the third electrode 250. When V1 is less than 0 and V3 is greater than 0, the electric field between the third electrode 250 and the second electrode 240 is consistent with the polarization direction, and the electric field between the first electrode 230 and the second electrode 240 is opposite to the polarization direction.

Optionally, please continue to refer to Figure 4, the second electrode 240 is grounded, and a first voltage V1 is applied to the first electrode 230, and a third voltage V3 is applied to the third electrode 250, and when V1>0 and V3<0 are satisfied, the electric field between the third electrode 250 and the second electrode 240 is opposite to the polarization direction, and the electric field between the first electrode 230 and the second electrode 240 is consistent with the polarization direction.

Referring to FIG. 4 , the working principle of the piezoelectric diaphragm of the embodiment of the present application is shown, which is as follows:

E3=(D33/∈3)*T3 (Ex=D33/∈3*Tx; where Tx is the stress on the x-axis).

When the piezoelectric diaphragm 200 moves downward, the second piezoelectric layer 220 generates downward tensile stress, and the first piezoelectric layer 210 is compressed, so a differential signal voltage V3 = -V1> 0 can be generated. When the piezoelectric diaphragm 200 moves upward, the second piezoelectric layer 220 generates upward tensile stress, and the first piezoelectric layer 210 is compressed.

In some examples of the present application, referring to FIGS. 5 to 7 , the piezoelectric diaphragm 200 has a plurality of slits 270 , and each of the slits 270 penetrates the piezoelectric diaphragm 200 in the thickness direction, and is configured to be able to divide the piezoelectric diaphragm 200 into a plurality of membrane petals 201 .

That is to say, the piezoelectric diaphragm 200 may be, for example, a piezoelectric cantilever diaphragm. The piezoelectric diaphragm 200 may be composed of a plurality of diaphragm petals 201 . The diaphragm petal 201 is a part of the piezoelectric diaphragm 200 .

When the piezoelectric diaphragm 200 is applied to a piezoelectric transducer, if the piezoelectric diaphragm 200 includes a plurality of membrane petals 201, one end of each membrane petal 201 is a fixed end that can be fixed to the substrate 100, and the other end is a movable end that can be suspended above the back cavity of the substrate.

Optionally, each active end of the piezoelectric diaphragm 200 may be located on the same plane through a flexible/narrow spring support, thereby reducing the performance difference caused by the deformation of the piezoelectric diaphragm 200 itself.

Optionally, referring to FIG5 , the piezoelectric diaphragm is a rectangular or square cantilever diaphragm, including a first region 202 and a second region 203 located side by side on one side of the first region 202, and the slit 270 extends in a horizontal direction from one side edge of the piezoelectric diaphragm to another side edge opposite to the side, so as to divide the piezoelectric diaphragm into a plurality of mutually parallel long strip-shaped diaphragm petals 201;

The first electrode 230 , the second electrode 240 and the third electrode 250 are layered in the second region 203 along the thickness direction. In the projection direction, the first electrode 230 and the third electrode 250 are distributed in a mirror-symmetrical manner with respect to the second electrode 240 .

For example, each of the membrane petals 201 is a long rectangular strip.

5 , the piezoelectric diaphragm 200 can be divided into four strip-shaped rectangles by three parallel slits.

Please continue to refer to Figure 5, wherein the first electrode 230 includes a first bus electrode and a plurality of first interdigitated electrodes vertically arranged on one side of the first bus electrode; the second electrode 240 includes a second bus electrode and a plurality of second interdigitated electrodes vertically arranged on both sides of the second bus electrode; the third electrode 250 includes a third bus electrode and a plurality of third interdigitated electrodes vertically arranged on one side of the third bus electrode; in the projection direction, the first bus electrode and the third bus electrode are located on both sides of the second bus electrode, and the first bus electrode, the second bus electrode and the third bus electrode are all straight and parallel to each other; the first interdigitated electrode and the third interdigitated electrode are arranged one by one and are staggered with the second interdigitated electrode, respectively, and the first interdigitated electrode, the second interdigitated electrode and the third interdigitated electrode are all straight.

Optionally, referring to FIG6 , the piezoelectric diaphragm is a rectangular or square cantilever diaphragm, including a first region 202 and a second region 203 surrounding the first region 202; the slit 270 extends from the edge of the piezoelectric diaphragm toward the center in the horizontal direction, so as to divide the piezoelectric diaphragm into a plurality of triangular diaphragm petals 201; the first electrode 230, the second electrode 240 and the third electrode 250 are layered in the second region 203 along the thickness direction;

In the projection direction, each of the membrane petals 201 has two first electrodes 230 located on both sides in mirror symmetry along the central axis, between the two first electrodes 230 are two third electrodes 250 located in the middle in mirror symmetry, between each first electrode 230 and the adjacent third electrode 250 is a second electrode 240, and the two second electrodes 240 are mirror symmetric structures.

6 , when the piezoelectric diaphragm 200 is a square cantilever diaphragm, four slits 270 can be used to form each diaphragm petal 201 of the piezoelectric diaphragm 200 into a triangle, and the four diaphragms 201 are symmetrically arranged in pairs.

Please continue to refer to FIG. 6 , wherein the first electrode 230 includes a first bus electrode and a plurality of first interdigitated electrodes disposed on one side of the first bus electrode; the second electrode 240 includes a second bus electrode and a plurality of second interdigitated electrodes disposed on both sides of the second bus electrode; Pole 250 includes a third bus electrode and a plurality of third interdigitated electrodes arranged on one side of the third bus electrode; in the projection direction, the first bus electrode and the third bus electrode are located on both sides of the second bus electrode, and the first bus electrode, the second bus electrode and the third bus electrode are all straight lines, wherein the first bus electrode is inclined along the side of the membrane flap 201, the second bus electrode is inclined at a set angle relative to the first bus electrode, and the third bus electrode is vertically arranged; the first interdigitated electrode and the third interdigitated electrode are arranged one by one and are staggered with the second interdigitated electrode, respectively, and the first interdigitated electrode, the second interdigitated electrode and the third interdigitated electrode are all straight lines.

Referring to FIG. 6 , on each triangular membrane petal 201 , based on the shape of the membrane petal, the electrode patterns of the first electrode 230 and the third electrode 250 are different, but the difference lies in the tilt angle, and both are comb-tooth-shaped structures.

Optionally, referring to FIG7 , the piezoelectric diaphragm is a circular cantilever diaphragm, comprising a first region 202 and a second region 203 surrounding the outer periphery of the first region 202; the slit 270 extends horizontally from the edge of the piezoelectric diaphragm toward the center, so as to divide the piezoelectric diaphragm into a plurality of fan-shaped diaphragm petals 201; the first electrode 230, the second electrode 240 and the third electrode 250 are layered in the second region 203 along the thickness direction, and in the projection direction, the first electrode 230 and the third electrode 250 are mirror-symmetrically distributed with respect to the second electrode 240.

Referring to FIG. 7 , when the piezoelectric diaphragm 200 is a circular cantilever diaphragm, four slits 270 may be used to form each diaphragm petal 201 of the piezoelectric diaphragm 200 into a fan shape.

Please continue to refer to Figure 7, wherein the first electrode 230 includes a first bus electrode and a plurality of first interdigitated electrodes arranged on one side of the first bus electrode; the second electrode 240 includes a second bus electrode and a plurality of second interdigitated electrodes arranged on both sides of the second bus electrode; the third electrode 250 includes a third bus electrode and a plurality of third interdigitated electrodes arranged on one side of the third bus electrode; in the projection direction, the first bus electrode and the third bus electrode are located on both sides of the second bus electrode, and the first bus electrode, the second bus electrode and the third bus electrode are all straight lines, wherein the first bus electrode and the third bus electrode are respectively inclined along the side of each of the membrane petals 201; the first interdigitated electrodes and the third interdigitated electrodes are arranged one by one and are respectively staggered with the second interdigitated electrodes, and the first interdigitated electrodes, the second interdigitated electrodes and the third interdigitated electrodes are all arc-shaped.

It should be noted that, on the piezoelectric diaphragm 200, each diaphragm petal 201 can be controlled individually and independently, or can be mechanically connected at the end of the cantilever through a flexible/narrow spring (not shown).

In addition, the path of forming the slit 270 on the piezoelectric diaphragm 200 can be adjusted according to the specific shape and size of the piezoelectric diaphragm 200, and is not limited to the above examples.

In some examples of the present application, the first piezoelectric layer 210 and the second piezoelectric layer 220 have the same thickness, which ranges from 0.5 μm to 2 μm.

In the embodiment of the present application, the piezoelectric diaphragm 200 itself does not contain a base layer, but includes two piezoelectric layers and three layers of electrodes; wherein the three electrodes are formed on the two piezoelectric layers at intervals in the longitudinal direction. The thickness of each piezoelectric layer should be reasonably controlled, so as to avoid the problem that the thickness of the formed piezoelectric diaphragm 200 is too large, resulting in reduced sensitivity of its vibration and requiring a large assembly space.

In an embodiment of the present application, the thickness of the first piezoelectric layer 210 and the second piezoelectric layer 220 is controlled to be between 0.5 μm and 2 μm, which makes the thickness of the formed piezoelectric diaphragm 200 appropriate, which not only ensures the mechanical strength of the piezoelectric diaphragm 200, but also ensures the sensitivity of the vibration of the piezoelectric diaphragm 200. At the same time, it is suitable for the assembly space of most microphones and will not be difficult to assemble due to excessive thickness.

Optionally, referring to FIG. 8 , the first electrode 230 , the second electrode 240 and the third electrode 250 are respectively led out with an electrical connection structure 260 .

Specifically, the electrical connection structure 260 may be a solder pad or a solder foot, which is used to electrically connect the piezoelectric diaphragm 200 to an external device such as a circuit board.

According to a second aspect of the present application, a piezoelectric transducer is provided, referring to Figures 8 to 11, comprising: a substrate 100 having a back cavity 110 and the piezoelectric diaphragm 200 mentioned above, wherein the piezoelectric diaphragm 200 is arranged on one side of the substrate 100 and covers the back cavity 110; wherein the first piezoelectric layer 210 faces the substrate 100, a dielectric layer 300 is provided between the substrate 100 and the first piezoelectric layer 210, and the area opposite to the dielectric layer 300 and the back cavity 110 is a hollow area.

The material of the substrate 100 is, for example, silicon.

Wherein, the dielectric layer 300 is made of silicon dioxide material.

Optionally, when forming the first electrode 230, a dielectric layer 300 of silicon dioxide material may be first formed on a surface of a substrate 100, and then a relatively thin metal film may be deposited on the dielectric layer 300, and then the first electrode 230 may be formed by photolithography and etching. The thickness of the metal film should be less than the thickness of either the first piezoelectric layer 210 or the second piezoelectric layer 220.

The dielectric layer 300 may be used to separate the substrate 100 from the piezoelectric diaphragm 200 .

It should be noted that the dielectric layer 300 does not cover the back cavity 110 of the substrate 100 , but the area opposite to the back cavity 110 is a hollow area and can be connected to the back cavity 110 .

According to the third aspect of the present application, the present embodiment provides a method for preparing the above-mentioned piezoelectric transducer. The method for preparing the piezoelectric transducer at least comprises the following steps S1 to S6:

Step S1, providing a substrate 100, covering a dielectric layer 300 on one side of the substrate 100, and forming a first electrode 230 on the dielectric layer 300;

Step S2, covering the first piezoelectric layer 210 on the first electrode 230, and forming the second electrode 240 on the surface of the first piezoelectric layer 210 away from the first electrode 230;

Step S3, covering the second piezoelectric layer 220 on the second electrode 240, and forming a third electrode 250 on a surface of the second piezoelectric layer 220 away from the second electrode 240, so as to obtain a piezoelectric diaphragm 200;

Step S4, opening a through hole 280 in the center of the piezoelectric diaphragm 200 along the thickness direction, and exposing a portion of the first electrode 230, the second electrode 240 and the third electrode 250 by etching;

Step S5, disposing an electrical connection structure 260 in the exposed areas of the first electrode 230, the second electrode 240 and the third electrode 250; and

Step S6: forming a back cavity 110 on a side of the substrate 100 away from the piezoelectric diaphragm 200 , and removing a region on the dielectric layer 300 opposite to the back cavity 110 to form a hollow region.

In some examples of the present application, in the above step S1, the step of forming the first electrode 230 includes, for example, the following steps S11 and S12:

Step S11, forming a dielectric layer 300 on one side of the substrate 100; and

Step S12, forming a metal film on the dielectric layer 300, and forming the first electrode 230 through photolithography and etching; wherein the thickness of the metal film is less than the thickness of either the first piezoelectric layer 210 or the second piezoelectric layer 220, and the thickness of the first piezoelectric layer 210 and the second piezoelectric layer 220 is the same, and the thickness is controlled to be 0.5μm to 2μm.

Optionally, the dielectric layer 300 is made of silicon dioxide material.

Optionally, the first electrode 230 is a metal material, and a metal film can be formed on the dielectric layer 300 by deposition, and then a set electrode pattern is formed by photolithography and etching. The thickness of the metal film is, for example, 0.1 um, which is much thinner than the thickness of each piezoelectric layer formed subsequently.

In an embodiment of the present application, optionally, the first electrode 230, the second electrode 240 and the third electrode 250 are first deposited to form a metal film, and then photolithography and etching are performed to form a set electrode pattern; wherein the thickness of the metal film is less than the thickness of either the first piezoelectric layer 210 or the second piezoelectric layer 220, and the thickness of the first piezoelectric layer 210 and the second piezoelectric layer 220 is controlled to be 0.5μm to 2μm.

For example, in the above step S2: a first piezoelectric layer 210 is formed on the substrate 100, and the first electrode 230 is bonded to the lower surface of the first piezoelectric layer 210; at the same time, a second electrode 240 is formed on the upper surface of the first piezoelectric layer 210. In this way, electrodes are formed on two opposite surfaces of the first piezoelectric layer 210. The difference between the formation method of the second electrode 240 and the formation method of the first electrode 230 is that the metal film used to form the second electrode 240 is deposited on the upper surface of the first piezoelectric layer 210 (the first electrode 230 is formed on the dielectric layer 300).

In the above step S3, the surface of the first piezoelectric layer 210 provided with the second electrode 240 is covered with the second piezoelectric layer 220, so that the second electrode 240 is located between the first piezoelectric layer 210 and the second piezoelectric layer 220. At the same time, a third electrode 250 is formed on the surface of the second piezoelectric layer 220 facing away from the first piezoelectric layer 210 (the upper surface of the second piezoelectric layer 220).

That is to say, through step S2 and step S3, the piezoelectric diaphragm 200 forms a composite membrane structure of two piezoelectric layers and three electrodes. At the same time, the first piezoelectric layer 210 and the second piezoelectric layer 220 are symmetrically arranged in the thickness direction, while the first electrode 230, the second electrode 240 and the third electrode 250 are staggered in the thickness direction. Among them, the electrode pattern of the third electrode 250 is the same as that of the first electrode 230, and the electrode pattern of the third electrode 250 is different from that of the second electrode 240.

Optionally, the piezoelectric material used by the first piezoelectric layer 210 and the second piezoelectric layer 220 may be an AlN type (e.g., AlN, ScAlN, AlYbN, YInN, etc.) piezoelectric material, or a PZT type (e.g., PZT, PMN-PT, etc.) piezoelectric material. Of course, the piezoelectric material may also be a material such as ZnO, which is not limited in the embodiments of the present application.

For example, when the first piezoelectric layer 210 and the second piezoelectric layer 220 are both AlN-type piezoelectric films, the metal film material deposited thereon is Moly or TiW, that is, the material of the formed electrode layer is Moly or TiW.

For another example, when the first piezoelectric layer 210 and the second piezoelectric layer 220 are both PZT-type piezoelectric films, the metal film material deposited thereon is Ti and/or Pt, that is, the formed electrode layer material is Ti and/or Pt.

Optionally, the formation method of the first piezoelectric layer 210 and the second piezoelectric layer 220 may include at least one of sputtering, metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE) and sol-gel spin coating, which is not limited in the embodiments of the present application.

It should be noted that the first piezoelectric layer 210 and the second piezoelectric layer 220 may have the same deposition and annealing/polarization conditions.

In some examples of the present application, a portion of the dielectric layer 300 may be removed by etching to form a hollow area, and the hollow area needs to be opposite to the back cavity 110 .

Specifically, the back cavity 110 is formed on the substrate 100 , and the substrate 100 can be etched through by photolithography and DRIE, and then the back dielectric layer 300 is removed by dry etching and/or wet etching to form a hollow area on the dielectric layer 300 .

In some examples of the present application, the preparation method further includes: dividing the piezoelectric diaphragm 200 into a plurality of membrane petals 201 , and making each of the membrane petals 201 have one end fixed to the substrate and the other end suspended above the substrate 100 .

In this way, the piezoelectric diaphragm 200 can be formed into a piezoelectric cantilever diaphragm.

The embodiment of the present application also provides a sound-generating device, see FIGS. 9 to 11 , comprising a packaging structure 400 , on which a sound hole 421 and at least one piezoelectric transducer as described above are provided; wherein the piezoelectric transducer is disposed in the packaging structure 400 .

The sound generating device is, for example, a MEMS microphone.

Among them, the packaging structure 400 includes a base 410 and a shell 420, the shell 420 is covered on the base 410 and encloses the base 410 to form a accommodating cavity 430; the sound hole 421 is located on the shell 420 and is connected to the accommodating cavity 430; the side of the substrate 100 away from the piezoelectric diaphragm 200 is arranged on the base 410, and the base 410 is provided with a through hole 411 connected to the back cavity 110.

The piezoelectric transducer of the embodiment of the present application can be applied to a MEMS microphone, wherein the piezoelectric diaphragm 200 is, for example, a core sound pickup structure, and the back cavity 110 on the substrate 100 is used to provide a vibration space for the piezoelectric diaphragm 200. When the incident sound pressure enters the piezoelectric transducer, the piezoelectric diaphragm 200 converts the incident sound pressure into a voltage signal based on the piezoelectric effect, thereby realizing the reading of the sound signal.

Furthermore, referring to FIG. 11 , an ASIC chip 500 may be provided in the packaging structure for further processing, such as amplifying, the voltage signal output by the piezoelectric MEMS transducer.

The sound hole 421 may be located on the top of the housing 420 , as shown in FIG. 9 . In this case, the sound hole 421 is an upwardly emitting sound hole.

Of course, the sound hole 421 may also be located on the side wall of the housing 420 , as shown in FIG. 10 . In this case, the sound hole 421 is a side-emitting sound hole.

Optionally, referring to Figures 9 and 10, in order to increase the sensitivity or sound pressure level SPL, the piezoelectric transducer is arranged as a repeating unit in an array on a larger substrate 100. Due to the use of bipolar D33 mode drive, it is relatively easy to obtain a large vibration amplitude and sensitivity, which is crucial for lead-free piezoelectric films with low piezoelectric coefficients.

In addition, see Figure 11, which shows a typical bottom port microphone structure, in which the piezoelectric transducer D33 mode of the present application is adopted to enhance the inherent sensitivity of the sensor. The differential output also doubles the sensitivity of the single-ended format, so high SNR signal-to-noise ratio and/or high AOP acoustic overload point or low THD total harmonic distortion can be achieved.

An embodiment of the present application further provides an electronic device, which includes the sound-generating device as described above.

The electronic device includes but is not limited to smart phones, tablet computers, laptop computers, smart wearable devices, etc., and this application does not impose any restrictions on this.

The above embodiments focus on the differences between the various embodiments. As long as the different optimization features between the various embodiments are not contradictory, they can be combined to form a better embodiment. Considering the simplicity of the text, they will not be repeated here.

Although some specific embodiments of the present application have been described in detail by way of example, it should be understood by those skilled in the art that the above examples are only for illustration, not for limiting the scope of the present application. It should be understood by those skilled in the art that the above embodiments may be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims (19)

A piezoelectric diaphragm, characterized in that it comprises a first piezoelectric layer (210) and a second piezoelectric layer (220) covering one side of the first piezoelectric layer (210), a first electrode (230) being provided on the lower surface of the first piezoelectric layer (210), a third electrode (250) being provided on the upper surface of the second piezoelectric layer (220), and a second electrode (240) being provided between the first piezoelectric layer (210) and the second piezoelectric layer (220); In the projection direction, the first electrode (230) and the third electrode (250) are respectively arranged on both sides of the second electrode (240), and are respectively arranged in a staggered manner with respect to the second electrode (240). The piezoelectric diaphragm according to claim 1, characterized in that the first electrode (230) and the third electrode (250) include a first bus electrode and a plurality of first interdigitated electrodes arranged on one side of the first bus electrode; The third electrode (250) comprises a third bus electrode and a plurality of third interdigitated electrodes arranged on one side of the third bus electrode; The second electrode (240) comprises a second bus electrode and a plurality of second interdigitated electrodes symmetrically arranged on both sides of the second bus electrode; In the projection direction, the first interdigital electrodes and the third interdigital electrodes are arranged in a one-to-one correspondence, and are respectively arranged in a staggered manner with the second interdigital electrodes to form a fork structure. The piezoelectric diaphragm according to claim 1 is characterized in that, when a first voltage V1 is applied to the first electrode (230), a second voltage V2 is applied to the second electrode (240), and a third voltage V3 is applied to the third electrode (250), and V3>V2, V1<V2, the electric field between the third electrode (250) and the second electrode (240) is consistent with the polarization direction, and the electric field between the first electrode (230) and the second electrode (240) is opposite to the polarization direction. The piezoelectric diaphragm according to claim 1 is characterized in that the second electrode (240) is grounded, and a first voltage V1 is applied to the first electrode (230), and a third voltage V3 is applied to the third electrode (250), and when V1<0 and V3>0, the electric field between the third electrode (250) and the second electrode (240) is consistent with the polarization direction, and the electric field between the first electrode (230) and the second electrode (240) is opposite to the polarization direction. The piezoelectric diaphragm according to claim 1 is characterized in that the piezoelectric diaphragm has a plurality of slits (270), and each of the slits (270) penetrates the piezoelectric diaphragm in the thickness direction, and is configured to be able to divide the piezoelectric diaphragm into a plurality of membrane petals (201). The piezoelectric diaphragm according to claim 5, characterized in that the piezoelectric diaphragm is a rectangular or square cantilever diaphragm, comprising a first region (202) and a second region (203) located side by side with the first region (202), and the slit (270) extends in a horizontal direction from one side edge of the piezoelectric diaphragm to another side edge opposite to the side, so as to divide the piezoelectric diaphragm into a plurality of mutually parallel long strip-shaped diaphragm petals (201); The first electrode (230), the second electrode (240) and the third electrode (250) are layered in the second region (203) along the thickness direction, and in the projection direction, the first electrode (230) and the third electrode (250) are distributed in a mirror-symmetrical manner with respect to the second electrode (240). The piezoelectric diaphragm according to claim 6, characterized in that the first electrode (230) comprises a first bus electrode and a plurality of first interdigitated electrodes vertically arranged on one side of the first bus electrode; The second electrode (240) comprises a second bus electrode and a plurality of second interdigitated electrodes vertically arranged on both sides of the second bus electrode; The third electrode (250) comprises a third bus electrode and a plurality of third interdigitated electrodes vertically arranged on one side of the third bus electrode; In the projection direction, the first bus electrode and the third bus electrode are located on both sides of the second bus electrode, and the first bus electrode, the second bus electrode and the third bus electrode are all straight and parallel to each other; the first interdigitated electrode and the third interdigitated electrode are arranged in a one-to-one correspondence and are staggered with the second interdigitated electrode, respectively, and the first interdigitated electrode, the second interdigitated electrode and the third interdigitated electrode are all straight. The piezoelectric diaphragm according to claim 5 is characterized in that the piezoelectric diaphragm is a rectangular or square cantilever diaphragm, comprising a first region (202) and a second region (203) surrounding the periphery of the first region (202); the slit (270) extends from the edge of the piezoelectric diaphragm toward the center in the horizontal direction, so as to divide the piezoelectric diaphragm into a plurality of triangular diaphragm petals (201); The first electrode (230), the second electrode (240) and the third electrode (250) are layered and arranged in the second region (203) along the thickness direction; In the projection direction, on both sides of each membrane petal (201), there are two first electrodes (230) which are mirror-symmetrical along the central axis, between the two first electrodes (230) are two third electrodes (250) which are mirror-symmetrically arranged in the middle, and between each first electrode (230) and the adjacent third electrode (250) is the second electrode (240), Furthermore, the two second electrodes (240) are mirror-symmetrical structures. The piezoelectric diaphragm according to claim 8, characterized in that the first electrode (230) comprises a first bus electrode and a plurality of first interdigitated electrodes arranged on one side of the first bus electrode; The second electrode (240) comprises a second bus electrode and a plurality of second interdigitated electrodes arranged on both sides of the second bus electrode; The third electrode (250) comprises a third bus electrode and a plurality of third interdigitated electrodes arranged on one side of the third bus electrode; In the projection direction, the first bus electrode and the third bus electrode are located on both sides of the second bus electrode, and the first bus electrode, the second bus electrode and the third bus electrode are all straight lines, wherein the first bus electrode is inclined along the side of the membrane flap (201), the second bus electrode is inclined at a set angle relative to the first bus electrode, and the third bus electrode is vertically arranged; the first interdigitated electrode and the third interdigitated electrode are arranged in a one-to-one correspondence and are respectively staggered with the second interdigitated electrode, and the first interdigitated electrode, the second interdigitated electrode and the third interdigitated electrode are all straight lines. The piezoelectric diaphragm according to claim 5 is characterized in that the piezoelectric diaphragm is a circular cantilever diaphragm, comprising a first region (202) and a second region (203) surrounding the periphery of the first region (202); the slit (270) extends from the edge of the piezoelectric diaphragm toward the center in the horizontal direction, so as to divide the piezoelectric diaphragm into a plurality of fan-shaped diaphragm petals (201); The first electrode (230), the second electrode (240) and the third electrode (250) are layered in the second region (203) along the thickness direction, and in the projection direction, the first electrode (230) and the third electrode (250) are distributed in a mirror-symmetrical manner with respect to the second electrode (240). The piezoelectric diaphragm according to claim 10, characterized in that the first electrode (230) comprises a first bus electrode and a plurality of first interdigitated electrodes arranged on one side of the first bus electrode; The second electrode (240) comprises a second bus electrode and a plurality of second interdigitated electrodes arranged on both sides of the second bus electrode; The third electrode (250) comprises a third bus electrode and a plurality of third interdigitated electrodes arranged on one side of the third bus electrode; In the projection direction, the first bus electrode and the third bus electrode are located on both sides of the second bus electrode, and the first bus electrode, the second bus electrode and the third bus electrode are all straight lines, wherein the first bus electrode and the third bus electrode are respectively The first interdigitated electrodes and the third interdigitated electrodes are arranged in a one-to-one correspondence and are staggered with the second interdigitated electrodes, respectively, and the first interdigitated electrodes, the second interdigitated electrodes and the third interdigitated electrodes are all arc-shaped. The piezoelectric diaphragm according to claim 1, characterized in that the first piezoelectric layer (210) and the second piezoelectric layer (220) have the same thickness, which is 0.5 μm to 2 μm. A piezoelectric transducer, comprising: A substrate (100) having a back cavity (110); and The piezoelectric diaphragm (200) according to any one of claims 1 to 12, wherein the piezoelectric diaphragm (200) is disposed on one side of the substrate (100) and covers the back cavity (110); The first piezoelectric layer (210) faces the substrate (100), a dielectric layer (300) is provided between the substrate (100) and the first piezoelectric layer (210), and the area where the dielectric layer (300) and the back cavity (110) are opposite is a hollow area. A method for preparing a piezoelectric transducer according to claim 13, characterized in that the preparation method comprises: Providing a substrate, covering a dielectric layer on one side of the substrate, and forming a first electrode on the dielectric layer; Covering the first electrode with a first piezoelectric layer, and forming a second electrode on a surface of the first piezoelectric layer facing away from the first electrode; Covering the second electrode with a second piezoelectric layer, and forming a third electrode on a surface of the second piezoelectric layer away from the second electrode, so as to obtain a piezoelectric diaphragm; A through hole is formed at the center of the piezoelectric diaphragm along the thickness direction, and a partial area of the first electrode, the second electrode and the third electrode is exposed by etching; Disposing an electrical connection structure in the area where the first electrode, the second electrode, and the third electrode are exposed; and A back cavity is formed on a side of the substrate away from the piezoelectric diaphragm, and a region on the dielectric layer opposite to the back cavity is removed to form a hollow region. The preparation method according to claim 14 is characterized in that the first electrode, the second electrode and the third electrode are first deposited to form a metal film, and then photolithography and etching are performed to form a set electrode pattern; The thickness of the metal film is smaller than the thickness of either the first piezoelectric layer or the second piezoelectric layer, and the thickness of the first piezoelectric layer and the second piezoelectric layer is controlled to be 0.5 μm to 2 μm. m. The preparation method according to claim 14 is characterized in that the preparation method further comprises: dividing the piezoelectric diaphragm into a plurality of membrane petals, and making one end of each of the membrane petals fixed to the substrate and the other end suspended above the substrate. A sound-generating device, characterized by comprising: A packaging structure (400), wherein a sound hole (421) is provided on the packaging structure (400); and At least one piezoelectric transducer according to claim 13, wherein the piezoelectric transducer is disposed in the packaging structure (400). The sound-generating device according to claim 17, characterized in that the packaging structure (400) comprises a base (410) and a shell (420), wherein the shell (420) is covered on the base (410) and encloses the base (410) to form a receiving cavity (430); The sound hole (421) is located on the shell (420) and is connected to the accommodating cavity (430); the side of the substrate (100) facing away from the piezoelectric diaphragm (200) is arranged on the base (410), and the base (410) is provided with a through hole (411) connected to the back cavity (110). An electronic device, characterized by comprising the sound-generating device as described in claim 17 or 18.