A piezoelectric MEMS speaker and a method for manufacturing the same

Abstract

The present invention relates to the field of speaker technology, and in particular to a piezoelectric MEMS speaker and a method for preparing the same, wherein the piezoelectric MEMS speaker comprises: a body, wherein a cavity region is formed on the body; a vibration film, which is disposed above the cavity region and connected to the upper surface of the body; and a plurality of cantilever beam spring structures, wherein the plurality of cantilever beam spring structures are sequentially connected and disposed circumferentially along the upper surface of the body; the cantilever beam spring structure comprises a fixed end and a free end. In the present application, a first piezoelectric composite structure is disposed on the vibration film, and a second piezoelectric composite structure is disposed on the cantilever beam spring. According to the polarization directions of the first piezoelectric composite structure and the second piezoelectric composite structure, the first piezoelectric composite structure and the second piezoelectric composite structure are connected in series or in parallel, thereby improving the driving force and mechanical characteristics of the MEMS speaker, so that the MEMS speaker can obtain a greater sound pressure level output.

Description

Technical Field

[0001] The present invention relates to the technical field of loudspeakers, and in particular to a piezoelectric MEMS loudspeaker and a preparation method thereof. Background Art

[0002] Traditional speakers are driven by a coil and magnet system, where the coil pushes against a narrow section of a diaphragm to move air and produce sound. There is a lower limit to how big the coil and magnet assembly can be in a traditional speaker, and because the magnet cannot shrink without losing sound output, traditional speakers are difficult to miniaturize.

[0003] Piezoelectric MEMS speakers use a monolithic piezoelectric drive instead of a concentrated coil / magnet drive. They rely on the piezoelectric principle and do not generate electromagnetic radiation. The electrical impedance depends entirely on the capacitance between the two electrodes of the MEMS device. The electrical impedance of the pure capacitor can be recycled by collecting it from the vibration of the speaker, thereby reducing the total power consumption of the MEMS piezoelectric speaker.

[0004] However, there is currently a problem of low output sound pressure level SPL (sound pressure level), especially at the low frequency end. The main reason is that it is difficult to have a large enough stroke movement or air thrust in a small size. Therefore, how to improve the output sound pressure level of piezoelectric MEMS speakers through structural and process improvements is a technical problem that urgently needs to be solved in the current MEMS speaker industrialization. Summary of the invention

[0005] In view of this, an object of the present invention is to provide a piezoelectric MEMS speaker and a method for manufacturing the same.

[0006] In a first aspect, an embodiment of the present invention provides a piezoelectric MEMS speaker, the piezoelectric MEMS speaker comprising:

[0007] A body, wherein the body is provided with a cavity area;

[0008] A vibration film, disposed above the cavity area and connected to the upper surface of the body;

[0009] There are multiple cantilever beam spring structures, and the multiple cantilever beam spring structures are sequentially connected and arranged circumferentially along the upper surface of the body; the cantilever beam spring structure includes a fixed end and a free end, the fixed end is connected to the body, and the free end is connected to the vibration film. Under the action of excitation, the cantilever beam spring structure and the vibration film vibrate and make sound;

[0010] A first piezoelectric composite structure connected to the central area of ​​the vibration film;

[0011] The second piezoelectric composite structure is arranged on the cantilever beam spring structure, and the second piezoelectric composite structure is connected in parallel or in series with the first piezoelectric composite structure.

[0012] In combination with the first aspect, the first piezoelectric composite structure is disposed in a central area of ​​an upper surface and / or a central area of ​​a lower surface of the vibration film.

[0013] In combination with the first aspect, the first piezoelectric composite structure and the second piezoelectric composite structure have the same electric polarization direction, and the first piezoelectric composite structure and the second piezoelectric composite structure are connected in series.

[0014] In combination with the first aspect, the first piezoelectric composite structure and the second piezoelectric composite structure have opposite polarization directions, and the first piezoelectric composite structure and the second piezoelectric composite structure are connected in parallel.

[0015] In combination with the first aspect, the first piezoelectric composite structure includes at least one piezoelectric composite unit.

[0016] In combination with the first aspect, the first piezoelectric composite structure includes a plurality of piezoelectric composite units having the same electric polarization direction, and the plurality of piezoelectric composite units are connected in parallel.

[0017] In combination with the first aspect, the first piezoelectric composite structure includes a plurality of first piezoelectric composite units and at least one second piezoelectric composite unit, and the plurality of first piezoelectric composite units are connected in parallel and then connected in series with the second piezoelectric composite unit;

[0018] The electric polarization directions of the first piezoelectric composite unit and the second piezoelectric composite unit are opposite.

[0019] In combination with the first aspect, the second piezoelectric composite structure includes:

[0020] A first piezoelectric composite layer, comprising at least one piezoelectric composite unit, is disposed at a fixed end of the cantilever beam spring structure;

[0021] A second piezoelectric composite layer, comprising at least one piezoelectric composite unit, is disposed at the free end of the cantilever beam spring structure, and the second piezoelectric composite layer is electrically connected to the first piezoelectric composite structure;

[0022] an insulating layer, provided on the first piezoelectric composite layer and the second piezoelectric composite layer, and used for electrically isolating the first piezoelectric composite layer from the second piezoelectric composite layer;

[0023] A metal trace has one end connected to the first piezoelectric composite layer and the other end connected to the second piezoelectric composite layer.

[0024] In combination with the first aspect, the piezoelectric composite unit includes a bottom electrode layer, a top electrode layer and at least one piezoelectric film.

[0025] In a second aspect, the present application provides a method for preparing a piezoelectric MEMS speaker, the method comprising:

[0026] A vibration film and a cantilever beam spring structure are manufactured on the body, wherein the vibration film is arranged in the central area of ​​the body, and a plurality of cantilever beam spring structures are sequentially connected and circumferentially distributed on the body, and a free end of each cantilever beam spring structure is connected to the vibration film;

[0027] Etching the body so that the central area directly facing the vibration film is a cavity area;

[0028] Determining whether the first piezoelectric composite structure on the vibration film and the second piezoelectric composite structure on the cantilever beam spring structure have the same electric polarization direction;

[0029] If so, connecting the first piezoelectric composite structure and the second piezoelectric composite structure in series;

[0030] If not, the first piezoelectric composite structure and the second piezoelectric composite structure are connected in parallel.

[0031] The embodiments of the present invention bring the following beneficial effects: The present invention provides a piezoelectric MEMS speaker and a preparation method thereof, wherein the piezoelectric MEMS speaker comprises: a main body, wherein a cavity area is opened on the main body; a vibration film, which is arranged above the cavity area and connected to the upper surface of the main body; there are multiple cantilever beam spring structures, and the multiple cantilever beam spring structures are connected in sequence and arranged circumferentially along the upper surface of the main body; the cantilever beam spring structure comprises a fixed end and a free end, wherein the fixed end is connected to the main body, and the free end is connected to the vibration film, and under the action of excitation, the cantilever beam spring structure and the vibration film vibrate and make sound; a first piezoelectric composite structure, which is connected to the central area of ​​the vibration film; a second piezoelectric composite structure, which is arranged on the cantilever beam spring structure, and the second piezoelectric composite structure is connected in parallel or in series with the first piezoelectric composite structure.

[0032] In the present application, a first piezoelectric composite structure is arranged on the vibration film, and a second piezoelectric composite structure is arranged on the cantilever beam spring. According to the polarization directions of the first piezoelectric composite structure and the second piezoelectric composite structure, the first piezoelectric composite structure and the second piezoelectric composite structure are connected in series or in parallel, thereby improving the driving force and mechanical properties of the MEMS speaker, so that the MEMS speaker can obtain a greater sound pressure level output.

[0033] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings.

[0034] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1 A schematic diagram of the structure of a piezoelectric MEMS speaker provided in Example 1 of the present invention;

[0037] Figure 2 A schematic diagram of the AB cross-sectional structure of a piezoelectric MEMS speaker provided in Embodiment 1 of the present invention;

[0038] Figure 3 A schematic cross-sectional structure diagram of another piezoelectric MEMS speaker provided in Embodiment 1 of the present invention in which the first piezoelectric composite structure is disposed on both the upper and lower surfaces of the vibration film;

[0039] Figure 4 A schematic diagram of a structure in which a first piezoelectric composite layer and a second piezoelectric composite layer are connected in series on a third cantilever beam spring structure in a piezoelectric MEMS speaker provided in Example 1 of the present invention;

[0040] Figure 5 A schematic diagram of a structure in which a second piezoelectric composite layer and a first piezoelectric composite structure are connected in series on a second cantilever beam spring structure of a piezoelectric MEMS speaker provided in Example 1 of the present invention;

[0041] Figure 6 Another structural schematic diagram of the piezoelectric MEMS speaker provided in Embodiment 1 of the present invention;

[0042] Figure 7 Another structural schematic diagram of the piezoelectric MEMS speaker provided in Embodiment 1 of the present invention;

[0043] Figure 8 A schematic diagram of the structure of a piezoelectric MEMS speaker provided in Embodiment 1 of the present invention under a condition of electrode distribution;

[0044] Fig. 9 A schematic diagram of the structure of a piezoelectric MEMS speaker provided in Embodiment 1 of the present invention under another electrode distribution condition;

[0045] Fig.10A schematic diagram of the structure of a piezoelectric MEMS speaker provided in Embodiment 1 of the present invention under another electrode distribution condition;

[0046] Fig.11 This is a simulation effect diagram of a piezoelectric MEMS speaker provided in Example 1 of the present invention under single-electrode driving;

[0047] Fig.12 This is a diagram of the simulation effect of the piezoelectric MEMS speaker provided in Example 1 of the present invention under dual-electrode and three-electrode driving conditions. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0049] In order to facilitate the understanding of this embodiment, the technical terms designed in this application are briefly introduced below.

[0050] Piezoelectric speakers, also known as buzzers, crystal speakers or buzzer speakers, use the piezoelectric effect to generate sound. The initial mechanical movement is generated by applying voltage to the piezoelectric material, and this movement is usually converted into audible sound using a diaphragm and a resonator. Compared with other speakers, piezoelectric speakers are relatively easy to drive. Compared with traditional electro-coil speakers, piezoelectric MEMS speakers have the advantages of small size, thin thickness, light weight, low power consumption, and simple processing technology.

[0051] Piezoelectric speakers are commonly used to generate sound in digital quartz watches and other electronic devices, sometimes as tweeters in less expensive speaker systems, and are also used to generate ultrasonic waves in sonar systems.

[0052] MEMS (Microelectromechanical System) is an industrial technology that integrates microelectronics technology with mechanical engineering. Its operating range is within the micrometer range.

[0053] After introducing the technical terms involved in this application, the application scenarios and design concepts of the embodiments of this application are briefly introduced.

[0054] In traditional speakers, the size of the coil and magnet assembly has a lower limit. Since the magnet cannot shrink without losing sound output, it is difficult to miniaturize traditional speakers. Piezoelectric MEMS speakers use a single-chip piezoelectric drive instead of a centralized coil / magnet drive, relying on the piezoelectric principle, but there is currently a problem of low output sound pressure level SPL (sound pressure level), especially at the low frequency end. The main reason is that it is difficult to have a large enough stroke movement or air thrust in a small size, resulting in a low output sound pressure level of the piezoelectric MEMS speaker.

[0055] Example 1

[0056] The embodiment of the present application provides a piezoelectric MEMS speaker, which includes: a body 01, a vibration film 60, a cantilever beam spring structure, a first piezoelectric composite structure and a second piezoelectric composite structure.

[0057] The body 01 is provided with a cavity area 104 (combined with Figure 2 As shown), the body 01 is processed by a DRIE etching process to obtain a cavity area 104.

[0058] The vibration film 60 is disposed above the cavity area 104 and connected to the upper surface of the body 01 .

[0059] There are multiple cantilever beam spring structures, which are connected in sequence and arranged circumferentially along the upper surface of the body 01, combined with Figure 1 As shown, in this embodiment, there are four cantilever beam spring structures, namely a first cantilever beam spring structure 10a, a second cantilever beam spring structure 10b, a third cantilever beam spring structure 10c and a fourth cantilever beam spring structure 10d.

[0060] Taking the first cantilever beam spring structure 10a as an example, the first cantilever beam spring structure 10a includes a fixed end 30a and a free end 40a, the fixed end 30a is connected to the body 01, and the free end 40a is connected to the vibration film 60. Under excitation, the first cantilever beam spring structure 10a and the vibration film 60 vibrate and make sound.

[0061] The first piezoelectric composite structure 70 is connected to the central area of ​​the vibration film 60 .

[0062] The second piezoelectric composite structure is disposed on the cantilever beam spring structure, and the second piezoelectric composite structure is connected in parallel or in series with the first piezoelectric composite structure 70 .

[0063] In this embodiment, a first piezoelectric composite structure 70 is arranged on the vibration film 60, and a second piezoelectric composite structure is arranged on the cantilever beam spring structure (10a~10d). According to the polarization directions of the first piezoelectric composite structure and the second piezoelectric composite structure, the first piezoelectric composite structure 70 and the second piezoelectric composite structure are connected in series or in parallel, thereby improving the driving force and mechanical properties of the MEMS speaker, so that the MEMS speaker can obtain a larger sound pressure level output.

[0064] Combination Figure 1 As shown, in the present embodiment, there are four cantilever beam spring structures (10a~10d), and the cantilever beam spring structure includes a fixed end (30a~30d) and a free end (40a~40d), the fixed end (30a~30d) is respectively anchored on the main body 01, and the free end (40a~40d) is respectively connected to the vibration film 60, and under the action of excitation, the cantilever beam spring structure (10a~10d) and the vibration film 60 vibrate and make sound. A second piezoelectric composite structure (a first piezoelectric composite layer 11a~11d and a second piezoelectric composite layer 12a~12d) is respectively provided on each cantilever beam spring structure (10a~10d), that is, a first piezoelectric composite layer 11a and a second piezoelectric composite layer 12a are provided on the first cantilever beam spring structure 10a; a first piezoelectric composite layer 11b and a second piezoelectric composite layer 12b are provided on the second cantilever beam spring structure 10b; a first piezoelectric composite layer 11c and a second piezoelectric composite layer 12c are provided on the third cantilever beam spring structure 10c; and a first piezoelectric composite layer 11d and a second piezoelectric composite layer 12d are provided on the fourth cantilever beam spring structure 10d.

[0065] The first piezoelectric composite layer (11a-11d) is connected to the fixed end (30a-30d); the second piezoelectric composite layer (12a-12d) is connected to the free end (40a-40d), and there is no piezoelectric composite structure connection between the first piezoelectric composite layer (11a-11d) and the second piezoelectric composite layer (12a-12d), and electrical isolation is performed by the electrical isolation layer (20a-20d) through the MEMS process. In this embodiment, the first piezoelectric composite layer and the second piezoelectric composite layer 12a-12d each include a piezoelectric composite unit.

[0066] The materials of the cantilever beam spring structure (10a-10d) and the vibration film 60 can be single crystal silicon, polycrystalline silicon, glass, organic or non-polar compounds.

[0067] In combination with the first aspect, the first piezoelectric composite structure 70 is disposed in the central area of ​​the upper surface and / or the central area of ​​the lower surface of the vibration film 60 .

[0068] As an practicable method, the first piezoelectric composite structure 70 is disposed on the upper surface of the vibration film 60 (combined with Figure 2As another practicable manner, the first piezoelectric composite structure 70 is disposed on the lower surface of the vibration film 60; As another practicable manner, the first piezoelectric composite structure 70 is disposed on the upper surface and the lower surface of the vibration film 60 (combined with Figure 3 In this embodiment, the first piezoelectric composite structure 70 is disposed on the upper surface of the vibration film 60 , and the metal welding position is located on the upper surface of the body 01 .

[0069] In combination with the first aspect, the first piezoelectric composite structure 70 and the second piezoelectric composite structure have the same electric polarization direction, and the first piezoelectric composite structure 70 and the second piezoelectric composite structure are connected in parallel.

[0070] In combination with the first aspect, the first piezoelectric composite structure 70 and the second piezoelectric composite structure have opposite electric polarization directions, and the first piezoelectric composite structure 70 and the second piezoelectric composite structure are connected in series.

[0071] In combination with the first aspect, the first piezoelectric composite structure 70 includes at least one piezoelectric composite unit.

[0072] In combination with the first aspect, the first piezoelectric composite structure includes a plurality of piezoelectric composite units having the same electric polarization direction, and the plurality of piezoelectric composite units are connected in parallel.

[0073] In combination with the first aspect, the first piezoelectric composite structure 70 includes a plurality of first piezoelectric composite units and at least one second piezoelectric composite unit, and the plurality of piezoelectric composite units in the first electric polarization direction are connected in parallel and then connected in series with the second piezoelectric composite unit;

[0074] The electric polarization directions of the first piezoelectric composite unit and the second piezoelectric composite unit are opposite.

[0075] In combination with the first aspect, the second piezoelectric composite structure includes: a first piezoelectric composite layer (11a-11d), a second piezoelectric composite layer (12a-12d), an insulating layer (20a-20c) and a metal trace (combined Figure 1 shown).

[0076] The first piezoelectric composite layer (11a-11d) comprises at least one piezoelectric composite unit and is arranged at the fixed end (30a-30d) of the cantilever beam spring structure.

[0077] The second piezoelectric composite layer (12a-12d) includes at least one piezoelectric composite unit, is disposed at the free end (40a-40d) of the cantilever beam spring structure, and is electrically connected to the first piezoelectric composite structure 70.

[0078] The insulating layer (20a-20c) is provided on the first piezoelectric composite layer (11a-11d) and the second piezoelectric composite layer (12a-12d) and is used to electrically isolate the first piezoelectric composite layer 11a-11d and the second piezoelectric composite layer (12a-12d);

[0079] One end of the metal wiring is connected to the first piezoelectric composite layer (11a-11d), and the other end is connected to the second piezoelectric composite layer (12a-12d).

[0080] Combination Figure 1 , Figure 4 , Figure 5 For example, the second piezoelectric composite structure disposed on the third cantilever beam spring structure 10c includes a first piezoelectric composite layer 11c and a second piezoelectric composite layer 12c, wherein the first piezoelectric composite layer 11c is disposed at the fixed end 30c, and the second piezoelectric composite layer 12c is disposed at the free end 40c. Figure 4 As shown, the second piezoelectric composite structure also includes an insulating layer 20c arranged between the first piezoelectric composite layer 11c and the second piezoelectric composite layer 12c, and there is no piezoelectric layer in the insulating layer 20c; the first piezoelectric composite layer 11c and the second piezoelectric composite layer 12c are electrically connected through a metal wire. Specifically, when the polarization directions of the first piezoelectric composite layer 11c and the second piezoelectric composite layer 12c are the same, a parallel connection mode is adopted; when the polarization directions of the first piezoelectric composite layer 11c and the second piezoelectric composite layer 12c are opposite, a series connection mode is adopted.

[0081] The body 01 is grooved by MEMS etching process to obtain 07-1 and 08-1 (combined with Figure 4 As shown), by slotting, a Figure 3 The third cantilever beam spring structure 10c is shown, and the width of the gap is set at 1 to 5 um. When driving is applied, the fixed end 30c of the third cantilever beam spring structure 10c is fixed, the second piezoelectric composite structure is deformed, and the free end 40c of the third cantilever beam spring structure 10c is deformed under force, driving the vibration film 60 to vibrate up and down to push the air, thereby making a sound.

[0082] The body 01 includes a base silicon layer and a cavity region obtained by DRIE etching process.

[0083] The piezoelectric composite unit constituting the above-mentioned piezoelectric composite layer and piezoelectric composite structure includes a bottom electrode layer 201 , a top electrode layer 203 and at least one piezoelectric film 202 . The piezoelectric film 202 is disposed between the bottom electrode layer 201 and the top electrode layer 203 .

[0084] Combination Figure 2 As shown, in this embodiment, the piezoelectric film 202 is a layer, the first piezoelectric composite structure 70 is arranged on the central area of ​​the upper surface of the vibration film 60, the second piezoelectric composite structure is arranged on the upper surface of the cantilever beam spring structure (10a~10d), the gap between the vibration film 60 and the cantilever beam spring structure is 81, 91, and the gap between the cantilever beam spring structure and the main body 01 is 80, 90.

[0085] As another possible implementation, combining Figure 3 The first piezoelectric composite structure 70 is arranged in the central area of ​​the upper surface of the vibration film 60 and the central area of ​​the lower surface of the vibration film 60. The first piezoelectric composite structure 70 includes a bottom electrode layer 201, a piezoelectric film 202 and a top electrode layer 203 arranged in sequence.

[0086] When the piezoelectric film 202 is a multilayer structure, the piezoelectric composite unit includes a top electrode layer 201, first to Nth piezoelectric films 202, and a bottom electrode layer 203 arranged in sequence from top to bottom, wherein in the first to Nth piezoelectric films 202, an electrode layer structure (not shown in the figure) is arranged between two adjacent piezoelectric films 202. The material of the piezoelectric film 202 can be a single crystal piezoelectric material or a polycrystalline piezoelectric material, such as single crystal AlN, doped AlN, single crystal PZT, ZnO, etc. The thickness of the piezoelectric layer is 0.1 to 25um, and the thickness of each piezoelectric layer can be the same or different. The materials of the top electrode layer 201 and the bottom electrode layer 203 can be single crystal metal materials such as Mo, Pt, Al, Cu, etc., and can also be alloy materials. The thickness of the top electrode layer 201 and the bottom electrode layer 203 is 0.01 to 5um.

[0087] Combination Figure 4 As shown, taking the electrical connection of the third cantilever beam spring structure 10c of the piezoelectric MEMS speaker as an example: the second piezoelectric composite structure on the third cantilever beam spring structure 10c includes a first piezoelectric composite layer 11c, a second piezoelectric composite layer 12c and an electrical isolation layer 20c; wherein the first piezoelectric composite layer 11c and the second piezoelectric composite layer 12c both contain a single-layer piezoelectric film 202.

[0088] The schematic diagram of the first piezoelectric composite layer 11c and the second piezoelectric composite layer 12c connected in series is shown in FIG. Figure 4 Specifically: the first top electrode 21c is electrically connected to the second bottom electrode 23c; the first bottom electrode 24c is electrically connected to the second top electrode 26c; wherein 22c and 25c are metal traces connecting the second piezoelectric composite layer 12b to the first piezoelectric composite structure 70.

[0089] Combination Figure 5 As shown, the electrical connection mode when the second piezoelectric composite layer 12b on the second cantilever beam spring structure 10b of the piezoelectric MEMS speaker and the first piezoelectric composite structure 70 have the same electric polarization direction is taken as an example:

[0090] When the piezoelectric layers of the second piezoelectric composite structure and the first piezoelectric composite structure 70 in the central region of the vibrating film 60 have the same polarization direction, the second piezoelectric composite layers in the first piezoelectric composite structure 70 and the second piezoelectric composite structure should be in a series relationship. Figure 5As shown, the bottom electrode 51c of the second piezoelectric composite layer 12b is connected to the top electrode 53c of the first piezoelectric composite structure 70, and the top electrode 54c of the second piezoelectric composite layer 12b is connected to the bottom electrode 56c of the first piezoelectric composite structure 70; 52c and 54c are metal traces connecting the second piezoelectric composite layer 12b to the first piezoelectric composite structure 70.

[0091] In this embodiment, by setting the polarization direction and electric field direction of each part of the first piezoelectric composite structure and the second piezoelectric composite structure, the piezoelectric MEMS speaker can obtain the maximum vibration displacement under certain driving conditions, thereby improving the sound pressure level output.

[0092] The examples are as follows: 12b is the second piezoelectric composite layer of the second cantilever beam spring structure 10b, 11d is the first piezoelectric composite single layer of the fourth cantilever beam spring structure 10d, and when the polarization directions of the first piezoelectric composite structure 70, the second piezoelectric composite unit 12b of the second cantilever beam spring structure 10b and the first piezoelectric composite unit 11d of the fourth cantilever beam spring structure 10d are the same, the electrical connection between the first piezoelectric composite structure 70 and the second piezoelectric composite unit 12b of the second cantilever beam spring structure 10b is a series structure; when the polarization directions of the first piezoelectric composite structure 70 and the second piezoelectric composite unit 12b of the second cantilever beam spring structure 10b are opposite, the electrical connection is a series structure.

[0093] It is worth noting that the vibration film 60 and the cantilever beam spring structure can be of any shape as long as they are adapted to the shape of the vibration film 60. The structural differences will lead to different performances of the piezoelectric MEMS speakers, such as the first-order resonant frequency of the piezoelectric MEMS speakers, the displacement of the vibration film 60 under the same voltage, and the output sound pressure level.

[0094] In this embodiment, in combination with the above example, the vibration film is a quadrilateral, and the cantilever beam spring structure is also a quadrilateral. In this embodiment, there are four cantilever beam spring structures, and the four cantilever beam spring structures are connected end to end;

[0095] As another practicable manner, the shape of the vibration film 60 is hexagonal, and the corresponding cantilever beam spring structure is also hexagonal, that is, each cantilever beam spring structure corresponds to one side of the vibration film 60 (such as Figure 6 shown);

[0096] As another practicable manner, the shape of the vibration film 60 is circular, and the corresponding cantilever beam spring structure is also circular, circumferentially surrounding the vibration film 60 and being electrically connected to the vibration film 60 (eg, Figure 7 shown).

[0097] In the cross-sectional view of the piezoelectric MEMS speaker along AB in this embodiment, the second piezoelectric composite layer 12b of the second cantilever beam spring structure 10b and the first piezoelectric composite layer 11d of the fourth cantilever beam spring structure 10d in the cantilever beam spring structures on the left and right sides of the piezoelectric MEMS speaker. The polarization direction of the piezoelectric MEMS speaker is as follows: Fig.10 As shown by the arrow in the figure, the positive electrical connection terminal is marked with a symbol "+" and the negative electrical connection terminal is marked with a symbol "-" (combined with Figure 8 , Fig. 9 , Fig.10 shown).

[0098] Combination Figure 8 As shown, when the polarization directions of the piezoelectric layers in the piezoelectric MEMS speaker are consistent and upward (or all downward), the first piezoelectric composite structure 70 and the second piezoelectric composite layer 12b of the second cantilever beam spring structure 10b are a series structure, and the negative electrical connection end (lower electrode) of the first piezoelectric composite structure 70 is connected to the positive electrical connection end (upper electrode) of the second piezoelectric composite layer 12b, and the positive electrical connection end (upper electrode) of the first piezoelectric composite structure 70 is connected to the negative electrical connection end (lower electrode) of the second piezoelectric composite layer 12b.

[0099] Combination Fig. 9 In the piezoelectric MEMS speaker, the polarization direction of the first piezoelectric composite structure 70 is downward, and the polarization directions of the second piezoelectric composite layer 12b and the first piezoelectric composite layer 11d on the left and right sides are both upward; that is, when the polarization directions of the piezoelectric layers are inconsistent, the first piezoelectric composite structure 70 and the second piezoelectric composite layer 12b of the second cantilever beam spring structure 10b are a parallel structure, that is, the negative electrical connection end (lower electrode) of the first piezoelectric composite structure 70 is connected to the negative electrical connection end (lower electrode) of the second piezoelectric composite layer 12b; the positive electrical connection end (upper electrode) of the first piezoelectric composite structure 70 is connected to the positive electrical connection end (upper electrode) of the second piezoelectric composite layer 12b.

[0100] Combination Fig.10 As shown, in the piezoelectric MEMS speaker, the polarization direction of the first piezoelectric composite structure 70 is downward, the polarization directions of the first piezoelectric composite layers 11d on the left and right sides are also downward, and the polarization direction of the second piezoelectric composite layer 12b is downward and opposite to the polarization direction of the first piezoelectric composite structure 70; the polarization directions of the first piezoelectric composite layer 11d and the second piezoelectric composite layer 12b are opposite, and the electrical connection method is parallel connection; the first piezoelectric composite layer 11d and the first piezoelectric composite structure 70 have the same polarization direction, and the electrical connection method is series connection; the polarization direction of the second piezoelectric composite layer 12b is opposite to the polarization direction of the first piezoelectric composite structure 70, and the electrical connection method is parallel connection.

[0101] The piezoelectric MEMS speaker structure provided in this embodiment can be a bridge structure with reinforced edges; it can also be a circular, rectangular or polygonal structure with reinforced all around; by setting the polarization direction and electric field direction of each voltage layer, the piezoelectric MEMS speaker can obtain the maximum vibration displacement and sound pressure level output under certain driving conditions.

[0102] In this embodiment, the piezoelectric MEMS speaker has a rectangular structure, a unit size of 3 mm×3 mm, a single piezoelectric layer structure: SOI substrate silicon wafer, Si / PT / PZT / PT / PZT / PT=5um / 0.1um / 1um / 0.1um / 1um / 0.1um.

[0103] Using the piezoelectric MEMS speaker provided in this embodiment, the MEMS piezoelectric speakers with the same structure are simulated under the same excitation by different electrode connection methods to obtain the following simulation results: Fig.11 , Fig.12 And the simulation data are shown in Table 1-1.

[0104] Table 1-1 Finite element simulation results of piezoelectric MEMS speakers

[0105]

[0106] Combination Fig.11 , Fig.12 And from Table 1-1, we can see that:

[0107] The displacement of the cantilever beam driven by the inner and outer single electrodes is not much different from that of the inner membrane single electrode, but the volume of air pushed is quite different. This is because the vibration pattern is caused by the different positions of the piezoelectric composite unit;

[0108] The cantilever beam is driven by dual inner and outer electrodes, and the diaphragm vibrates in a piston mode, with large displacement and greater air displacement.

[0109] The inner and outer electrodes of the cantilever beam, plus the three-electrode drive of the diaphragm, have the largest air displacement because the diaphragm displacement is much greater than the maximum of the inner and outer double-electrode drive of the cantilever beam.

[0110] In a second aspect, this embodiment provides a method for preparing a piezoelectric MEMS speaker, comprising the following steps:

[0111] S110, a vibration film 60 and an arm beam spring structure are manufactured on the main body 01, the vibration film 60 is arranged in the central area of ​​the main body, and a plurality of cantilever beam spring structures are sequentially connected and circumferentially distributed on the main body 01, and the free end of each cantilever beam spring structure is connected to the vibration film 60.

[0112] S120 , etching the device body 01 so that the central area facing the vibration film 60 becomes the cavity area 104 .

[0113] S130, determining whether the first piezoelectric composite structure 70 on the vibration film 60 and the second piezoelectric composite structure on the cantilever beam spring structure have the same electric polarization direction.

[0114] If the first piezoelectric composite structure 70 and the second piezoelectric composite structure have the same electric polarization direction, step S140 is executed.

[0115] If the electric polarization directions of the first piezoelectric composite structure 70 and the second piezoelectric composite structure are different, step S150 is executed.

[0116] S140, connecting the first piezoelectric composite structure 70 and the second piezoelectric composite structure in series.

[0117] S150, connecting the first piezoelectric composite structure 70 and the second piezoelectric composite structure in parallel.

[0118] In this embodiment, by judging whether the polarization directions of the first piezoelectric composite structure 70 and the second piezoelectric composite structure are the same, a series electrical connection is adopted when the polarization directions are the same, and a parallel electrical connection is adopted when the polarization directions are different (i.e. opposite), so that the vibrating film 60 and the cantilever beam spring structure vibrate and make sound under the action of excitation.

[0119] In addition, the material of the body 01 can be silicon, glass, sapphire, etc. By changing the cavity area 104, different first-order resonance frequencies of the piezoelectric MEMS speaker can be obtained.

[0120] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the system and device described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0121] In addition, in the description of the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0122] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc., which can store program codes.

[0123] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0124] Finally, it should be noted that the above embodiments are only specific implementations of the present invention, which are used to illustrate the technical solutions of the present invention, rather than to limit them. The protection scope of the present invention is not limited thereto. Although the present invention is described in detail with reference to the above embodiments, those skilled in the art should understand that any person skilled in the art can still modify the technical solutions recorded in the above embodiments within the technical scope disclosed by the present invention, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A piezoelectric MEMS speaker, characterized in that: The piezoelectric MEMS speaker comprises: A body, wherein the body is provided with a cavity area; A vibrating film, disposed above the cavity area and connected to the upper surface of the body; There are multiple cantilever beam spring structures, and the multiple cantilever beam spring structures are sequentially connected and arranged circumferentially along the upper surface of the body; the cantilever beam spring structure includes a fixed end and a free end, the fixed end is connected to the body, and the free end is connected to the vibration film. Under the action of excitation, the cantilever beam spring structure and the vibration film vibrate and make sound; A first piezoelectric composite structure is provided in a central area of ​​an upper surface and / or a central area of ​​a lower surface of the vibration film and is connected to a central area of ​​the vibration film; A second piezoelectric composite structure is provided on the cantilever beam spring structure, and the second piezoelectric composite structure is connected in parallel or in series with the first piezoelectric composite structure; Wherein, if the first piezoelectric composite structure and the second piezoelectric composite structure have the same electric polarization direction, the first piezoelectric composite structure and the second piezoelectric composite structure are connected in series; If the electric polarization directions of the first piezoelectric composite structure and the second piezoelectric composite structure are opposite, the first piezoelectric composite structure and the second piezoelectric composite structure are connected in parallel.

2. The piezoelectric MEMS speaker according to claim 1, characterized in that: The first piezoelectric composite structure includes at least one piezoelectric composite unit.

3. The piezoelectric MEMS speaker according to claim 1, characterized in that: The first piezoelectric composite structure includes a plurality of piezoelectric composite units having the same electric polarization direction, and the plurality of piezoelectric composite units are connected in parallel.

4. The piezoelectric MEMS speaker according to claim 3, characterized in that: The first piezoelectric composite structure includes a plurality of first piezoelectric composite units and at least one second piezoelectric composite unit, and the plurality of first piezoelectric composite units are connected in parallel and then connected in series with the second piezoelectric composite unit; The electric polarization directions of the first piezoelectric composite unit and the second piezoelectric composite unit are opposite.

5. The piezoelectric MEMS speaker according to claim 1, characterized in that: The second piezoelectric composite structure comprises: A first piezoelectric composite layer, comprising at least one piezoelectric composite unit, is disposed at a fixed end of the cantilever beam spring structure; A second piezoelectric composite layer, comprising at least one piezoelectric composite unit, is disposed at the free end of the cantilever beam spring structure, and the second piezoelectric composite layer is electrically connected to the first piezoelectric composite structure; an insulating layer, provided on the first piezoelectric composite layer and the second piezoelectric composite layer, and used for electrically isolating the first piezoelectric composite layer from the second piezoelectric composite layer; A metal trace has one end connected to the first piezoelectric composite layer and the other end connected to the second piezoelectric composite layer.

6. The piezoelectric MEMS speaker according to claim 3, characterized in that: The piezoelectric composite unit includes a bottom electrode layer, a top electrode layer and at least one piezoelectric film.

7. A method for preparing a piezoelectric MEMS speaker, characterized in that: The method comprises: A vibration film and a cantilever beam spring structure are manufactured on the body, wherein the vibration film is arranged in the central area of ​​the body, and a plurality of cantilever beam spring structures are sequentially connected and circumferentially distributed on the body, and a free end of each cantilever beam spring structure is connected to the vibration film; Etching the body so that the central area directly facing the vibration film is a cavity area; Determining whether the first piezoelectric composite structure on the vibration film and the second piezoelectric composite structure on the cantilever beam spring structure have the same electric polarization direction; If so, connecting the first piezoelectric composite structure and the second piezoelectric composite structure in series; If not, the first piezoelectric composite structure and the second piezoelectric composite structure are connected in parallel.

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