CN113852897A

CN113852897A - Piezoelectric MEMS (micro-electromechanical systems) loudspeaker, design method thereof and electronic equipment

Info

Publication number: CN113852897A
Application number: CN202110881872.3A
Authority: CN
Inventors: 张孟伦
Original assignee: Tianjin University
Current assignee: Guangzhou Leyi Investment Co ltd; Rhine Century Beijing Culture Media Co ltd
Priority date: 2021-08-02
Filing date: 2021-08-02
Publication date: 2021-12-28

Abstract

The invention discloses a piezoelectric MEMS speaker, a design method thereof, and an electronic device. The piezoelectric MEMS speaker includes N diaphragms adjacent to each other, the structures of the N diaphragms adjacent to each other are asymmetrical, N is a positive integer greater than 1, and the diaphragms adjacent to each other have a first gap, and Or, the piezoelectric MEMS speaker includes at least one diaphragm and at least one boundary element adjacent to the diaphragm, the height of the boundary element is not higher than the height of the diaphragm, and there is a second gap between the diaphragm and the boundary element, wherein, The size of the first gap and/or the second gap satisfies a preset condition such that an acoustic short-circuit phenomenon occurs when the diaphragm vibrates at the mechanical resonance point, and does not occur when the diaphragm is stationary. The present invention realizes the adaptive acoustic short-circuit structure through the asymmetric design of the speaker diaphragm structure, or realizes the adaptive acoustic short-circuit structure through the height of the boundary element being lower than or equal to the diaphragm height, which can reduce the sound pressure level peak at the resonance and increase the bandwidth.

Description

Piezoelectric MEMS (micro-electromechanical systems) loudspeaker, design method thereof and electronic equipment

Technical Field

The invention relates to the technical field of MEMS, in particular to a piezoelectric MEMS loudspeaker, a design method thereof and electronic equipment.

Background

MEMS speakers typically produce sound by vibrating air with one or more actuator diaphragms. The displacement of a conventional MEMS speaker at the resonant frequency is maximized, which results in an unacceptably high amplitude spike in the sound pressure level of the speaker at the resonant frequency, and a smaller frequency domain bandwidth and a deteriorated frequency response curve.

Disclosure of Invention

In view of this, the present invention provides a piezoelectric MEMS speaker, a design method thereof, and an electronic device, which can adaptively generate an acoustic short circuit, reduce a sound pressure level peak at a resonance, and increase a bandwidth.

The first aspect of the present invention provides a piezoelectric MEMS speaker, which includes N adjacent diaphragms, where the N adjacent diaphragms are asymmetric in structure, N is a positive integer greater than 1, a first gap is provided between the adjacent diaphragms, and/or the piezoelectric MEMS speaker includes at least one diaphragm and at least one boundary element adjacent to the diaphragm, a height of the boundary element is not higher than a height of the diaphragm, and a second gap is provided between the diaphragm and the boundary element, where a size of the first gap and/or the second gap satisfies a predetermined condition such that an acoustic short-circuit phenomenon occurs when the diaphragm vibrates at a mechanical resonance point and does not occur when the diaphragm is stationary.

Optionally, the height of the boundary element is lower than the height of the diaphragm.

Optionally, the preset conditions include: when the diaphragm vibrates at the mechanical resonance point, the size of the first gap and/or the second gap is larger than 20 μm, or the gap area of the first gap and/or the second gap is larger than 5% of the loudspeaker area; and when the diaphragm is at rest, the gap size of the first gap and/or the second gap is less than 20 μm, or the gap area of the first gap and/or the second gap is less than 5% of the loudspeaker area.

Optionally, the structural asymmetry of the N diaphragms adjacent to each other includes: one or more of the diaphragm shape, the diaphragm size and the diaphragm thickness of the N diaphragms adjacent to each other are different.

Optionally, the piezoelectric MEMS speaker includes N diaphragms adjacent to each other, the structures of the N diaphragms adjacent to each other are asymmetric, and the diaphragm design satisfies the following characteristics: the N adjacent vibrating diaphragms are spliced into a polygonal vibrating diaphragm area, the fixed end of each vibrating diaphragm is located on the outline of the polygonal vibrating diaphragm area, the free end of each vibrating diaphragm has the same common point, and the common point is an eccentric point in the polygonal vibrating diaphragm area; and/or the N adjacent diaphragms are in an N-stage nested design, wherein the fixed ends of the diaphragms of each stage are collinear.

Optionally, the N diaphragms adjacent to each other are of N-level nested design, and at least two of the diaphragms have different shapes.

Optionally, in a piezoelectric MEMS loudspeaker comprising at least one diaphragm and at least one boundary element adjacent to the diaphragm, the boundary element has a height not higher than the height of the diaphragm, and an edge of the boundary element is parallel to at least one side of the free end of the diaphragm.

Optionally, the fixed end of the diaphragm is smaller in size than the free end.

Optionally, the diaphragm includes: a longitudinally stacked structural layer, a bottom electrode layer, a piezoelectric layer and a top electrode layer; or a bottom electrode layer, N piezoelectric layers and N-1 middle electrode layers which are stacked longitudinally, wherein N is a positive integer larger than 1, and a top electrode layer which are arranged alternately.

Optionally, the method further comprises: a substrate and the boundary element is composed of a portion of the substrate, the material of the boundary element being silicon.

Optionally, the fixed end of the diaphragm is connected with a diaphragm supporting layer, and the diaphragm supporting layer is made of silicon.

The second aspect of the present invention provides a method for designing a piezoelectric MEMS speaker, including: n adjacent vibrating diaphragms are arranged, the N adjacent vibrating diaphragms are asymmetric in structure, N is a positive integer larger than 1, and a first gap is formed between the adjacent vibrating diaphragms; and/or at least one diaphragm and at least one boundary element adjacent to the diaphragm are arranged, the height of the boundary element is not higher than that of the diaphragm, and a second gap is formed between the diaphragm and the boundary element; the size of the first gap and/or the second gap is set to satisfy a preset condition so that an acoustic short-circuit phenomenon occurs when the diaphragm vibrates at the mechanical resonance point, and the acoustic short-circuit phenomenon does not occur when the diaphragm is stationary.

Optionally, the preset conditions include: when the diaphragm vibrates at the mechanical resonance point, the spacing of the first gap and/or the second gap is larger than 20 μm, or the area of the first gap and/or the second gap is larger than 5% of the area of the loudspeaker; and the pitch of the first and/or second gap is less than 20 μm when the diaphragm is at rest, or to an extent that the area of the first and/or second gap is less than 5% of the area of the loudspeaker.

Optionally, in a case that the piezoelectric MEMS speaker includes N diaphragms adjacent to each other, and the structure of the N diaphragms adjacent to each other is asymmetric, the diaphragm design process includes the following steps: determining a polygonal diaphragm area and an eccentric point positioned in the polygonal diaphragm area, and connecting the vertex angle of the polygonal diaphragm area with the eccentric point, so that the polygonal diaphragm area is divided into N diaphragms which are adjacent to each other, the fixed end of each diaphragm is arranged on the outline of the polygonal diaphragm area, and the eccentric point is simultaneously used as the free end of the N diaphragms; and/or determining a total nested diaphragm area, dividing the total nested diaphragm area into N diaphragms which are adjacent to each other and are in N-level nested design, and taking at least one edge on the outline of the total nested diaphragm area as the fixed ends of the N diaphragms which are adjacent to each other.

Optionally, at least two diaphragms of the N mutually adjacent diaphragms of the N-stage nested design have different shapes.

Optionally, in a case that the piezoelectric MEMS speaker includes at least one diaphragm and at least one boundary element adjacent to the diaphragm, and a height of the boundary element is not higher than a height of the diaphragm, the device layout design process includes the following steps: the edge of the boundary element is designed to be parallel to at least one side of the free end of the diaphragm.

Optionally, the method further comprises: the boundary element is provided to be comprised of a portion of the substrate of the piezoelectric MEMS speaker, the material of the boundary element being silicon.

Optionally, the method further comprises: the vibrating diaphragm supporting layer is arranged to support the fixed end of the vibrating diaphragm, and the vibrating diaphragm supporting layer is made of silicon.

A third aspect of the invention proposes an electronic device characterized by comprising a piezoelectric MEMS speaker according to any one of claims 1 to 11.

According to the technical scheme of the invention, the self-adaptive acoustic short-circuit structure is realized through the asymmetrical design of the loudspeaker diaphragm structure, or the self-adaptive acoustic short-circuit structure is realized through the height of the boundary element which is lower than or equal to the height of the diaphragm, so that the sound pressure level peak at the resonance position can be reduced, and the bandwidth is increased.

Drawings

For purposes of illustration and not limitation, the present invention will now be described in accordance with its preferred embodiments, particularly with reference to the accompanying drawings, in which:

fig. 1 is a top view of a piezoelectric MEMS speaker according to a first embodiment of the present invention;

FIGS. 2 to 5 are schematic cross-sectional views of two adjacent diaphragms of the embodiment shown in FIG. 1 at different vibration modes at a resonance frequency;

FIG. 6 is a top view of a piezoelectric MEMS speaker of conventional construction;

FIG. 7 is a graph comparing frequency response curves for the piezoelectric MEMS speaker of FIG. 1 and the piezoelectric MEMS speaker of FIG. 6;

fig. 8 to 10 respectively show the vibration of the diaphragm of the piezoelectric MEMS speaker shown in fig. 1 at three different frequency points;

fig. 11 is a top view of a piezoelectric MEMS speaker according to a second embodiment of the present invention;

fig. 12 is a top view of a piezoelectric MEMS speaker according to a third embodiment of the present invention;

fig. 13 is a top view of a piezoelectric MEMS speaker according to a fourth embodiment of the present invention;

fig. 14 is a top view of a piezoelectric MEMS speaker according to a fifth embodiment of the present invention;

fig. 15 is a top view of a piezoelectric MEMS speaker according to a sixth embodiment of the present invention;

fig. 16 is a top view of a piezoelectric MEMS speaker according to a seventh embodiment of the present invention;

fig. 17 to 19 respectively show sectional views of different vibration modes of the diaphragm in the piezoelectric MEMS speaker shown in fig. 16;

fig. 20 is a top view of a piezoelectric MEMS speaker according to an eighth embodiment of the present invention;

fig. 21 is a top view of a piezoelectric MEMS speaker according to a ninth embodiment of the present invention;

fig. 22 is a top view of a piezoelectric MEMS speaker according to a tenth embodiment of the present invention;

fig. 23 is a top view of a piezoelectric MEMS speaker according to an eleventh embodiment of the present invention;

fig. 24 is a top view of a piezoelectric MEMS speaker according to a twelfth embodiment of the present invention;

fig. 25 is a top view of a piezoelectric MEMS speaker according to a thirteenth embodiment of the present invention;

fig. 26 is a top view of a piezoelectric MEMS speaker according to a fourteenth embodiment of the present invention;

FIG. 27 is a schematic cross-sectional view of a diaphragm of a piezoelectric MEMS speaker in accordance with an embodiment of the present invention;

fig. 28 is a schematic cross-sectional view of a diaphragm of a piezoelectric MEMS speaker according to another embodiment of the present invention.

Detailed Description

In order to solve the problem, the invention provides a design of an adaptive acoustic short circuit, and the basic principle is as follows: a gap is formed between the diaphragm and other adjacent structures (which can be another diaphragm or a boundary element), and when the mechanical resonant frequency is higher, the gap causes the sound cavities on two sides of the loudspeaker diaphragm to generate an acoustic short circuit, so that the sound pressure level peak at the resonant frequency is greatly reduced; when the excitation frequency is far away from the resonance frequency, the sound pressure level of the frequency bands is ensured because the gap is small and the condition of sound short circuit is not met. This situation is collectively referred to as adaptive acoustic shorting.

The means for realizing the adaptive acoustic short circuit mainly include two kinds: firstly, by using asymmetric diaphragm structures (such as different sizes or shapes), the mechanical resonant frequencies of at least two diaphragms are different, and the diaphragms can start to vibrate at different frequency points, so that the gaps between adjacent diaphragms are enlarged in the vibrating process of the diaphragms, the acoustic short circuit phenomenon is caused, and the sound pressure level at the resonant frequency is reduced; the existence of multiple resonance frequencies for the speaker also divides the energy of the conventional planar MEMS speaker at one resonance frequency into the several resonance frequencies, thereby achieving an increase in bandwidth. Secondly, by using the boundary element with a height lower than or equal to the height of the diaphragm, the gap between the diaphragm and the boundary element is enlarged during the vibration process near the resonance point, which causes the phenomenon of acoustic short circuit, thereby reducing the sound pressure level at the frequency.

The technical solutions in the embodiments of the present invention are clearly and completely described below with reference to the drawings in the embodiments, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments that can be derived by one of ordinary skill in the art from the embodiments given herein are intended to be within the scope of the present invention.

The piezoelectric MEMS loudspeaker comprises N adjacent vibrating diaphragms, wherein the N adjacent vibrating diaphragms are asymmetric in structure, N is a positive integer larger than 1, and a first gap is formed between the adjacent vibrating diaphragms; and/or at least one diaphragm and at least one boundary element adjacent to the diaphragm, the boundary element having a height not higher than the height of the diaphragm, the diaphragm and the boundary element having a second gap therebetween. Wherein the size of the first gap and/or the second gap satisfies a preset condition such that an acoustic short-circuit phenomenon occurs when the diaphragm vibrates, and the acoustic short-circuit phenomenon does not occur when the diaphragm is stationary.

Preferably, the height of the boundary element is lower than the height of the diaphragm. Due to the height difference, it can be ensured that the distance d between the boundary element and the diaphragm is necessarily greater than zero.

Wherein, the structural asymmetry of N adjacent diaphragms means: one or more of the diaphragm shape, the diaphragm size and the diaphragm thickness of the N diaphragms adjacent to each other are different. Wherein the preset condition may include: when the diaphragm vibrates near the resonance point, the distance between the first gap and/or the second gap is larger than 20 micrometers, or the area of the first gap and/or the second gap is larger than 5% of the area of the loudspeaker, so that the loudspeaker can generate acoustic short circuit when vibrating near the resonance point, and the sound pressure peak is reduced; and when the diaphragm is at rest, the spacing of the first gap and/or the second gap is less than 20 μm, or the area of the first gap and/or the second gap is less than 5% of the area of the loudspeaker, so that the sound pressure of the loudspeaker at a non-resonance point is not deteriorated. The gap area refers to the gap width d multiplied by the gap length, and the speaker area refers to the area of the entire speaker (including the diaphragm and the gap) in the horizontal plane.

Fig. 1 is a layout of a piezoelectric MEMS speaker according to a first embodiment of the present invention. It should be noted that the figures only show the diaphragm and the peripheral structure, and other parts are omitted. Similar processing is also performed in a plurality of figures, which are not described in detail. The piezoelectric MEMS speaker shown in fig. 1 includes four

asymmetric diaphragms

10,11,12, and 13, 14 being a gap between adjacent diaphragms, and 23 being a diaphragm support layer (for mechanically supporting or fixing the diaphragm edge). Since the four diaphragms 10 to 13 are not different in shape from each other, the piezoelectric MEMS speaker generates four resonance frequencies. Because the vibration modes or directions of the diaphragms are different, the vibration amplitude of one diaphragm is larger, the vibration amplitude of the other diaphragm is smaller, or the vibration directions of the two diaphragms are opposite. Both of these conditions cause the gap spacing to become large, creating an acoustic short circuit phenomenon that reduces the sound pressure level at that frequency.

Fig. 2 to 5 are schematic diagrams of different vibration modes of two adjacent diaphragms at a resonance frequency according to the embodiment shown in fig. 1, where 11 and 13 are two diaphragms located opposite to each other, 23 is a diaphragm support layer, and d is a gap distance between two diaphragm tips. Specifically, the method comprises the following steps: FIG. 2 corresponds to the case where the vibration directions of the two diaphragms are opposite; FIG. 3 corresponds to the case where one diaphragm has a large amplitude and the other diaphragm does not vibrate; fig. 4 corresponds to the case where the two diaphragms have the same vibration direction but have larger amplitude difference; fig. 5 corresponds to the case where the single-ended diaphragm vibrates. When the resonant frequency is close to, the vibrating diaphragms meet the condition of self-adaptive acoustic short circuit, so that the sound pressure spike can be reduced; when the frequency is far lower than the resonance frequency, the condition of self-adaptive sound short circuit is not met between the vibrating diaphragms, so that the sound short circuit can be prevented, and the sound pressure is not deteriorated.

The adaptive acoustic short circuit can be generated as long as at least two resonant frequencies in the four vibrating diaphragms are different. There are various implementations of different resonant frequencies, such as different shapes, different sizes, different thicknesses, etc. between the diaphragms. The case of only four diaphragms is shown here, and two diaphragms, three diaphragms and more diaphragms can be flexibly designed as required. In such an embodiment, it can be considered that N (N is a positive integer greater than or equal to 1) diaphragms adjacent to each other are spliced into a polygonal diaphragm region, the fixed end of each diaphragm is located on the outline of the polygonal diaphragm region, and the free ends of the diaphragms have the same common point, which is an eccentric point inside the polygonal diaphragm region. As an alternative to the design method, it is understood that N adjacent and asymmetrical diaphragms can be designed in the following manner: the diaphragm region is divided into N asymmetric diaphragms by first determining the N-sided polygon diaphragm regions and the inner eccentricity point and then providing N gaps from the vertices of the polygon to the eccentricity point.

Fig. 6 is a layout of a piezoelectric MEMS speaker of a conventional structure, which has four diaphragms symmetrically arranged to have the same shape, size, and thickness.

Fig. 7 is a graph comparing frequency response curves of the piezoelectric MEMS speaker according to the embodiment of the present invention shown in fig. 1 and the conventional piezoelectric MEMS speaker shown in fig. 6. As is apparent from the results, the conventional speaker shown in fig. 6 has a sound pressure level frequency response curve as shown by the dotted line in fig. 7 due to the strong symmetry of the four diaphragms, and it can be seen that an unacceptable peak of 155dB sound pressure level occurs at 7 kHz. While the high amplitude spikes of the piezoelectric MEMS speaker of the embodiment of the present invention shown in fig. 1 are significantly reduced and the bandwidth is also increased.

Fig. 8 to 10 respectively show vibration conditions of the diaphragms of the piezoelectric MEMS speaker with the adaptive acoustic short-circuit structure shown in fig. 1 at three different frequency points, where the vibration directions of adjacent diaphragms are opposite to each other, which results in an increased distance between the diaphragms, and thus causes an acoustic short-circuit phenomenon. And because the shape or the size of different vibrating diaphragms are the same, the displacement of adjacent vibrating diaphragms is the same near the resonant frequency, so that the distance between the vibrating diaphragms is too small, and the sound short circuit does not occur, thereby causing sound pressure peak.

Fig. 11 is a layout of a piezoelectric MEMS speaker according to a second embodiment of the present invention, in which a nested cantilever beam structure is adopted. As shown in fig. 11, 10_1, 10_2, and 10_3 are three sequentially nested diaphragms fixed at the same end, 22 is a boundary element, 23 is a diaphragm support layer, and 14 is a gap between the diaphragms. The three diaphragms have different sizes, so that the resonant frequencies are different, and the self-adaptive acoustic short circuit is realized. The height of the boundary element 22 is not higher than the height of the diaphragms 10_1, 10_2, 10_ 3.

The design ideas of the two embodiments of fig. 1 and fig. 11 are combined, that is, the nested design is added to the asymmetric diaphragm, so as to obtain a layout of the piezoelectric MEMS speaker according to the third embodiment of the present invention as shown in fig. 12. Wherein 10i, 11i, 12i, 13i are internal diaphragms for high frequency parts; 10a, 11a, 12a, 13a are outer diaphragms for the low-frequency part; 22 is a boundary element, 23 is a diaphragm support layer, and 14 is a gap between the diaphragms.

Fig. 13 is a layout of a piezoelectric MEMS speaker according to a fourth embodiment of the present invention, and fig. 14 is a layout of a piezoelectric MEMS speaker according to a fifth embodiment of the present invention. The resonant frequency of the diaphragm can also be changed by changing the shape of the diaphragm in the nested design. For example, comparing the fourth embodiment shown in fig. 13 with the fifth embodiment shown in fig. 14, the resonant frequencies are different due to the different shapes of the diaphragms 10_1 and 10_ 2.

Fig. 15 is a layout of a piezoelectric MEMS speaker according to a sixth embodiment of the present invention. In the embodiment, the diaphragm structures with different shapes and nested designs are added on the basis of the traditional piezoelectric MEMS loudspeaker with four symmetrical diaphragms, so that different resonant frequencies of the diaphragms can appear, and the hardware condition of self-adaptive acoustic short circuit is met.

Fig. 16 is a layout of a piezoelectric MEMS speaker according to a seventh embodiment of the present invention. Fig. 16 shows two

triangular diaphragms

10 and 11, a gap 14 between the diaphragm and between the diaphragm and the boundary element, a boundary element 22, and a diaphragm support layer 23. This embodiment shows a structure for realizing an adaptive acoustic short circuit by using a height difference between the boundary element and the diaphragm, so that a gap between the diaphragm and the boundary element at and near the resonant frequency becomes larger, which causes an acoustic short circuit phenomenon, thereby reducing a sound pressure level at the frequency.

In the embodiment shown in fig. 16, the vibration modes of the diaphragm are as shown in fig. 17 to 19, where 13 is the diaphragm, 22 is the boundary element, 23 is the diaphragm support layer, and d is the distance between the diaphragm and the boundary element. Specifically, the method comprises the following steps: fig. 17 corresponds to the case where the height of the boundary element and the height of the diaphragm are the same; FIG. 18 corresponds to the case where the boundary element is lower than the diaphragm by d 0; fig. 19 corresponds to the case where a part of the diaphragm is located above the boundary element. When the diaphragm is static, the distance d is smaller, and the acoustic short circuit condition is not reached; when the diaphragm vibrates upwards or downwards, the distance d is increased to achieve an acoustic short circuit condition, and self-adaptive acoustic short circuit is achieved.

Based on the inventive principle of the embodiment shown in fig. 16, the present invention also proposes a piezoelectric MEMS speaker with an adaptive acoustic short circuit structure in other structures, as shown in fig. 20 to 22.

Fig. 20 is a layout of a piezoelectric MEMS speaker according to an eighth embodiment of the present invention. The acoustic short-circuit structure is realized in this embodiment by means of height differences between the

diaphragms

10,11,13 and between the diaphragms and the boundary element 22.

Fig. 21 is a layout of a piezoelectric MEMS speaker according to a ninth embodiment of the present invention. The difference in height between the

diaphragms

10,11 and the boundary elements 22 on both sides in fig. 21 can lead to acoustic short-circuits, which occur in the middle of the two diaphragms due to the difference in resonance frequency.

Fig. 22 is a layout of a piezoelectric MEMS speaker according to a tenth embodiment of the present invention. In fig. 22, the four diaphragms are only fixed in the middle, and the height difference between the periphery of the diaphragms and the boundary element 22 can realize an acoustic short-circuit.

In the above embodiments, the size of the fixed end is larger than that of the free end, and in order to increase the sound pressure level, the size of the free end of the diaphragm may be set larger than that of the fixed end, so as to push more air, thereby achieving the purpose of increasing the sound pressure level, as shown in fig. 23 to 26, specifically, 10,11,12, and 13 are diaphragms, 14 is a gap, 22 is a boundary element, and 23 is a diaphragm supporting layer.

Fig. 23 is a layout of a piezoelectric MEMS speaker according to the eleventh embodiment of the present invention. In fig. 23, the two

diaphragms

10,11 are fixed at the short side and free at the long side, and the height difference between the diaphragms and the surrounding boundary elements can cause acoustic short-circuits.

Fig. 24 is a layout of a piezoelectric MEMS speaker according to a twelfth embodiment of the present invention. The loudspeaker of fig. 24 comprises three diaphragms and the working principle is the same as that of fig. 27.

Fig. 25 is a layout of a piezoelectric MEMS speaker according to a thirteenth embodiment of the present invention. In fig. 25, the conventional planar diaphragm is fixed in the middle instead of being fixed at the periphery.

Fig. 26 is a layout of a piezoelectric MEMS speaker according to a fourteenth embodiment of the present invention. Fig. 26 shows an asymmetrical structure of the diaphragm, and the difference in resonance frequency and the height difference between the diaphragm and the boundary element both lead to an acoustic short circuit.

The diaphragm in the piezoelectric MEMS speaker according to the embodiment of the present invention may include a structural layer, a bottom electrode layer, a piezoelectric layer, and a top electrode layer, which are stacked in a longitudinal direction. As shown in the schematic cross-sectional view of the diaphragm in fig. 27, 1 is a structural layer, and the material may be silicon or the like; 2, a piezoelectric layer is made of AlN, PZT, ZnO and the like; and 3, a top electrode layer and a bottom electrode layer, wherein the material can be molybdenum, platinum, gold and other metals.

The diaphragm in the piezoelectric MEMS speaker according to the embodiment of the present invention may also include a bottom electrode layer, N piezoelectric layers, N-1 middle electrode layers, and a top electrode layer, which are stacked in the longitudinal direction, where N is a positive integer greater than 1. In another embodiment of a schematic cross-sectional view of a diaphragm shown in fig. 28, the piezoelectric layer 2 has two layers, and the electrode layer 3 (including a top electrode layer, a middle electrode layer, and a top electrode layer) has three layers. In which case the structural layer may be omitted.

In the piezoelectric MEMS speaker according to the embodiment of the present invention, the material of the boundary element and the diaphragm support layer is preferably silicon. The silicon material has good mechanical properties, is easy to obtain and has low cost.

The design method of the piezoelectric MEMS loudspeaker comprises the following steps: n adjacent vibrating diaphragms are arranged, the N adjacent vibrating diaphragms are asymmetric in structure, N is a positive integer larger than 1, and a first gap is formed between the adjacent vibrating diaphragms; and/or at least one diaphragm and at least one boundary element adjacent to the diaphragm are arranged, the height of the boundary element is not higher than that of the diaphragm, and a second gap is formed between the diaphragm and the boundary element; the size of the first gap and/or the second gap is set to satisfy a preset condition so that an acoustic short-circuit phenomenon occurs when the diaphragm vibrates, and the acoustic short-circuit phenomenon does not occur when the diaphragm is stationary. Preferably, the height of the boundary element is lower than the height of the diaphragm.

The preset conditions may include: when the diaphragm vibrates, the distance between the first gap and/or the second gap is larger than 20 μm, or the area of the first gap and/or the second gap is larger than 5% of the area of the loudspeaker; and, when the diaphragm is at rest, the pitch of the first and/or second gap is less than 20 μm, or to an extent that the area of the first and/or second gap is less than 5% of the loudspeaker area.

The structural asymmetry of the N diaphragms adjacent to each other may include: one or more of the diaphragm shape, the diaphragm size and the diaphragm thickness of the N diaphragms adjacent to each other are different.

In the case that the piezoelectric MEMS speaker includes N diaphragms adjacent to each other, and the structure of the N diaphragms adjacent to each other is asymmetric, the diaphragm designing process may include the steps of: determining a polygonal diaphragm area and an eccentric point positioned in the polygonal diaphragm area, and connecting the vertex angle of the polygonal diaphragm area with the eccentric point, so that the polygonal diaphragm area is divided into N diaphragms which are adjacent to each other, the fixed end of each diaphragm is arranged on the outline of the polygonal diaphragm area, and the eccentric point is simultaneously used as the free end of the N diaphragms; and/or determining a total nested diaphragm area, dividing the total nested diaphragm area into N diaphragms which are adjacent to each other and are in N-level nested design, and taking at least one edge on the outline of the total nested diaphragm area as the fixed ends of the N diaphragms which are adjacent to each other.

Among N mutually adjacent diaphragms of N-level nested design, the shapes of at least two diaphragms are different.

In the case that the piezoelectric MEMS speaker includes at least one diaphragm and at least one boundary element adjacent to the diaphragm, and the height of the boundary element is not higher than the height of the diaphragm, the device layout design process includes the following steps: the edge of the boundary element is designed to be parallel to at least one side of the free end of the diaphragm. When the design is adopted, when the device is in a static state, the widths (namely the intervals) of all the parts of the slit are consistent, and the processing is easy to realize; when the device is in a working state, the working conditions of all the parts of the slit are the same, and the phenomenon of acoustic short circuit is easy to realize.

The fixed end of the diaphragm may be smaller in size than the free end.

The diaphragm may include a longitudinally stacked structural layer, a bottom electrode, a piezoelectric layer, and a top electrode.

The design method of the piezoelectric MEMS loudspeaker can further comprise the following steps: the boundary element is provided to be comprised of a portion of the substrate of the piezoelectric MEMS speaker, the material of the boundary element being silicon.

The design method of the piezoelectric MEMS loudspeaker can further comprise the following steps: the vibrating diaphragm supporting layer is arranged to support the fixed end of the vibrating diaphragm, and the vibrating diaphragm supporting layer is made of silicon.

An electronic device according to an embodiment of the present invention may comprise any of the piezoelectric MEMS speakers disclosed above.

According to the technical scheme of the embodiment of the invention, the self-adaptive sound short-circuit structure is realized through the asymmetrical design of the loudspeaker diaphragm structure, or the self-adaptive sound short-circuit structure is realized through the height of the boundary element which is lower than or equal to the height of the diaphragm, so that the sound pressure level peak at the resonance position can be reduced, and the bandwidth can be increased.

The above-described embodiments should not be construed as limiting the scope of the invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions can occur, depending on design requirements and other factors. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A piezoelectric MEMS speaker is characterized in that,

the piezoelectric MEMS loudspeaker comprises N mutually adjacent diaphragms, the structures of the N mutually adjacent diaphragms are asymmetric, N is a positive integer larger than 1, a first gap is arranged between the mutually adjacent diaphragms, and/or,

the piezoelectric MEMS loudspeaker comprises at least one diaphragm and at least one boundary element adjacent to the diaphragm, the boundary element having a height not higher than the height of the diaphragm, the diaphragm and the boundary element having a second gap therebetween,

wherein the size of the first gap and/or the second gap satisfies a preset condition such that an acoustic short-circuit phenomenon occurs when the diaphragm vibrates at a mechanical resonance point, and does not occur when the diaphragm is stationary.

2. Piezoelectric MEMS loudspeaker according to claim 1, wherein the height of the boundary element is lower than the height of the diaphragm.

3. Piezoelectric MEMS speaker as claimed in claim 1, wherein the preset conditions include:

when the diaphragm vibrates at a mechanical resonance point, the size of the first gap and/or the second gap is larger than 20 μm, or the gap area of the first gap and/or the second gap is larger than 5% of the loudspeaker area; and is

When the diaphragm is at rest, the gap size of the first gap and/or the second gap is less than 20 μm, or the gap area of the first gap and/or the second gap is less than 5% of the loudspeaker area.

4. Piezoelectric MEMS loudspeaker according to claim 1, wherein the structural asymmetry of the N mutually adjacent diaphragms comprises: one or more of the diaphragm shape, the diaphragm size and the diaphragm thickness of the N diaphragms adjacent to each other are different.

5. Piezoelectric MEMS loudspeaker according to claim 1, characterized in that the piezoelectric MEMS loudspeaker comprises N mutually adjacent diaphragms, which are asymmetrical in their structure and which are designed to satisfy the following characteristics:

the N adjacent vibrating diaphragms are spliced into a polygonal vibrating diaphragm area, the fixed end of each vibrating diaphragm is located on the outline of the polygonal vibrating diaphragm area, the free ends of the vibrating diaphragms have the same common point, and the common point is an eccentric point in the polygonal vibrating diaphragm area; and/or the like and/or,

the N adjacent diaphragms are in N-stage nested design, wherein fixed ends of the diaphragms at all stages are collinear.

6. Piezoelectric MEMS loudspeaker as claimed in claim 5, wherein the N diaphragms adjacent to each other are of N-level nested design and wherein at least two diaphragms differ in shape.

7. Piezoelectric MEMS loudspeaker as claimed in claim 1, comprising at least one diaphragm and at least one boundary element adjacent to the diaphragm, the boundary element having a height not higher than the height of the diaphragm and an edge parallel to at least one side of the free end of the diaphragm.

8. The piezoelectric MEMS speaker of claim 7, wherein the fixed end of the diaphragm is smaller in size than the free end.

9. The piezoelectric MEMS speaker as claimed in any one of claims 1 to 8, wherein the diaphragm comprises:

a longitudinally stacked structural layer, a bottom electrode layer, a piezoelectric layer and a top electrode layer; or,

the piezoelectric actuator comprises a bottom electrode layer, N piezoelectric layers and N-1 middle electrode layers which are stacked longitudinally, and a top electrode layer, wherein N is a positive integer larger than 1.

10. The piezoelectric MEMS speaker as claimed in any one of claims 1 to 8, further comprising: a substrate and the border element is comprised of a portion of the substrate, the material of the border element being silicon.

11. Piezoelectric MEMS speaker as claimed in any one of claims 1 to 8, wherein the fixed end of the diaphragm is connected to a diaphragm support layer, the material of the diaphragm support layer being silicon.

12. A design method of a piezoelectric MEMS speaker is characterized by comprising the following steps:

the method comprises the following steps that N mutually adjacent vibrating diaphragms are arranged, the N mutually adjacent vibrating diaphragms are asymmetric in structure, N is a positive integer larger than 1, and a first gap is formed between the mutually adjacent vibrating diaphragms; and/or the like and/or,

arranging at least one diaphragm and at least one boundary element adjacent to the diaphragm, wherein the height of the boundary element is not higher than that of the diaphragm, and a second gap is formed between the diaphragm and the boundary element;

setting the size of the first gap and/or the second gap to satisfy a preset condition so that an acoustic short-circuit phenomenon occurs when the diaphragm vibrates at a mechanical resonance point, and the acoustic short-circuit phenomenon does not occur when the diaphragm is stationary.

13. A method of designing a piezoelectric MEMS speaker as claimed in claim 12, wherein the height of the boundary element is lower than the height of the diaphragm.

14. A method of designing a piezoelectric MEMS speaker as claimed in claim 12, wherein the preset conditions include:

when the diaphragm vibrates at a mechanical resonance point, the spacing of the first gap and/or the second gap is larger than 20 μm, or the area of the first gap and/or the second gap is larger than 5% of the area of the loudspeaker; and is

When the diaphragm is at rest, the spacing of the first gap and/or the second gap is less than 20 μm, or even the area of the first gap and/or the second gap is less than 5% of the area of the loudspeaker.

15. The design method of piezoelectric MEMS speaker as claimed in claim 12, wherein the structural asymmetry of the N diaphragms adjacent to each other comprises: one or more of the diaphragm shape, the diaphragm size and the diaphragm thickness of the N diaphragms adjacent to each other are different.

16. The method of claim 12, wherein the diaphragm design process in the case that the piezoelectric MEMS speaker includes N diaphragms adjacent to each other, and the N diaphragms adjacent to each other have asymmetric structures includes the following steps:

determining a polygonal diaphragm area and an eccentric point positioned in the polygonal diaphragm area, and connecting the vertex angle of the polygonal diaphragm area with the eccentric point, so as to divide the polygonal diaphragm area into N diaphragms which are adjacent to each other, setting the fixed end of each diaphragm on the outline of the polygonal diaphragm area, and simultaneously taking the eccentric point as the free end of the N diaphragms; and/or the like and/or,

determining a total nested diaphragm area, dividing the total nested diaphragm area into N diaphragms which are adjacent to each other and are designed in an N-level nested manner, and taking at least one edge on the outline of the total nested diaphragm area as the fixed ends of the N diaphragms which are adjacent to each other.

17. The design method of piezoelectric MEMS speaker as claimed in claim 16, wherein at least two diaphragms among N diaphragms adjacent to each other in the N-level nested design are different in shape.

18. The method according to claim 12, wherein in the case that the piezoelectric MEMS speaker includes at least one diaphragm and at least one boundary element adjacent to the diaphragm, and the height of the boundary element is not higher than the height of the diaphragm, the device layout design process includes the following steps:

the edge of the boundary element is designed to be parallel to at least one side of the free end of the diaphragm.

19. A method of designing a piezoelectric MEMS speaker as claimed in claim 18, wherein the fixed end of the diaphragm is smaller in size than the free end.

20. A method of designing a piezoelectric MEMS speaker as claimed in any one of claims 12 to 19, wherein the diaphragm includes:

21. A method of designing a piezoelectric MEMS speaker as claimed in any one of claims 12 to 19, further comprising: the boundary element is provided to be comprised of a portion of the substrate of the piezoelectric MEMS speaker, the material of the boundary element being silicon.

22. A method of designing a piezoelectric MEMS speaker as claimed in any one of claims 12 to 19, further comprising: the fixed end of the diaphragm is provided with a support layer, and the diaphragm support layer is made of silicon.

23. An electronic device, characterized by comprising a piezoelectric MEMS speaker as claimed in any one of claims 1 to 11.