A MEMS piezoelectric loudspeaker and acoustic device

Abstract

This application relates to the field of semiconductor technology, specifically to a MEMS piezoelectric loudspeaker and acoustic device, including a substrate and a piezoelectric stack disposed on the substrate; the piezoelectric stack has multiple tangents extending from the geometric center of the piezoelectric stack to the edge of the piezoelectric stack, forming multiple cantilever beams arranged rotationally symmetrically about the geometric center; each cantilever beam has a fixed edge away from the geometric center; at least two of the cantilever beams have trench structures on the substrate, the trench structures being located close to the fixed edge of the cantilever beam. This application can reduce peaks at resonant frequencies and effectively expand the frequency bandwidth, improving overall audio performance; in addition, this application can also reduce diaphragm stiffness, thereby significantly enhancing its low-frequency deformation capability and optimizing the low-frequency sound pressure level curve.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and more specifically, to a MEMS piezoelectric loudspeaker and acoustic device. Background Technology

[0002] MEMS piezoelectric loudspeakers typically use the same diaphragm design, resulting in a uniform cantilever beam shape. Consequently, these cantilever beams share the same resonant frequency. When the loudspeaker operates at this specific resonant frequency, the free end of the cantilever beam experiences its maximum displacement. This phenomenon causes the sound intensity at that frequency to be significantly higher than at other frequencies, creating a "peak." This undesirable high-amplitude peak disrupts the balance of sound quality, making certain frequencies in music or speech overly prominent, sounding unnatural or harsh. Furthermore, relying on only a single frequency as the excitation source limits the loudspeaker's effective frequency bandwidth, affecting the smoothness of the frequency response curve and overall sound quality. Utility Model Content

[0003] The purpose of this application is to provide a MEMS piezoelectric loudspeaker and acoustic device that can reduce peaks at resonant frequencies, effectively expand the frequency bandwidth, and improve overall audio performance. In addition, this application can also reduce diaphragm stiffness, thereby significantly enhancing its low-frequency deformation capability and optimizing the low-frequency sound pressure level curve.

[0004] The embodiments of this application are implemented as follows:

[0005] On one hand, this application provides a MEMS piezoelectric loudspeaker, including a substrate and a piezoelectric stack disposed on the substrate; the piezoelectric stack has multiple tangents extending from the geometric center of the piezoelectric stack to the edge of the piezoelectric stack, forming multiple cantilever beams arranged rotationally symmetrically about the geometric center; the cantilever beams have fixed sides away from the geometric center; at least two of the cantilever beams have groove structures on the substrate, the groove structures being located close to the fixed sides of the cantilever beams.

[0006] As an optional implementation, the substrate has a support structure on the side away from the piezoelectric stack, the support structure has a cavity in the middle, and the support structure has a connecting portion that connects to the edge of the substrate; the projection of the trench structure on the substrate coincides with the projection of the connecting portion on the substrate.

[0007] As an optional implementation, the trench structures are even in number and arranged symmetrically about the geometric center in pairs.

[0008] As an optional implementation, the trench structure includes at least two strip trenches; the at least two strip trenches extend in parallel directions; the at least two strip trenches are arranged sequentially along the direction perpendicular to the fixed side, and the width of the at least two strip trenches gradually decreases along the direction away from the fixed side.

[0009] As an optional implementation, the groove structure includes at least two strip grooves; at least one of the strip grooves extends parallel to the fixed side, and at least one of the strip grooves extends intersectes with the extension direction of the fixed side.

[0010] As an optional implementation, the trench structure includes a plurality of recessed holes; the plurality of recessed holes are arranged at intervals along the extension direction of the fixed side.

[0011] As an alternative implementation, the trench extends through the substrate; or, the opening of the trench structure faces the piezoelectric stack, and the depth of the trench structure is less than the thickness of the substrate.

[0012] As an optional implementation, the piezoelectric stack is a regular polygonal structure, the cantilever beam is an isosceles triangle structure, and the fixed side is located at the base of the isosceles triangle structure; the two ends of the groove structure are respectively connected to the two sides of the isosceles triangle.

[0013] As an optional implementation, the piezoelectric stack includes a bottom electrode layer, a piezoelectric layer, and a top electrode layer stacked sequentially.

[0014] On the other hand, embodiments of this application provide an acoustic device, including the aforementioned MEMS piezoelectric loudspeaker and a power amplifier, wherein the power amplifier is electrically connected to the piezoelectric loudspeaker.

[0015] The beneficial effects of the embodiments of this application include:

[0016] This application embodiment, by creating a trench structure on the substrate corresponding to the cantilever beam and performing etching frequency modulation processing, enables the speaker to generate multiple resonant excitations, thereby significantly increasing the frequency domain bandwidth. Simultaneously, compared to a speaker without etching frequency modulation processing, the speaker designed in this application exhibits a significantly reduced sound pressure level peak at the resonant frequency, contributing to a flatter and more stable audio response. Furthermore, the speaker of this application uses a symmetrically shaped diaphragm, possessing excellent audio performance. Simultaneously, this application avoids the cantilever beam fracture problem caused by excessive stress on the fixed edge of the cantilever beam, thereby improving structural reliability and ensuring a high product yield. This application embodiment, by etching a trench structure on the substrate of the cantilever beam to reduce the bending stiffness of the cantilever beam, significantly enhances its low-frequency deformation capability, improves air coupling efficiency, optimizes the low-frequency sound pressure level curve, and achieves a more balanced and immersive audio experience. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is one of the schematic diagrams of the MEMS piezoelectric loudspeaker structure in the embodiments of this application;

[0019] Figure 2 This is the second schematic diagram of the MEMS piezoelectric loudspeaker structure in the embodiments of this application;

[0020] Figure 3 This is the third schematic diagram of the MEMS piezoelectric loudspeaker structure in the embodiments of this application;

[0021] Figure 4 This is the fourth schematic diagram of the MEMS piezoelectric loudspeaker structure in the embodiments of this application;

[0022] Figure 5 This is the fifth schematic diagram of the MEMS piezoelectric loudspeaker structure in the embodiments of this application;

[0023] Figure 6 This is the sixth schematic diagram of the MEMS piezoelectric loudspeaker structure in the embodiments of this application;

[0024] Figure 7 This is the seventh schematic diagram of the MEMS piezoelectric loudspeaker structure in the embodiments of this application;

[0025] Figure 8 This is a comparison of the simulated SPL curves of the loudspeaker in the embodiment of this application and a conventional square loudspeaker.

[0026] Icons: 100-Substrate; 101-Piezoelectric stack; 102-Tangent; 103-Geometric center; 104-Cantilever beam; 105-Fixed edge; 106-Trench structure; 107-Support structure; 108-Cavity; 109-Connector; 110-Strip trench; 111-Recessed hole; 112-Bottom electrode layer; 113-Piezoelectric layer; 114-Top electrode layer. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0028] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0029] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0030] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0031] MEMS piezoelectric loudspeakers typically use the same diaphragm design, resulting in a consistent shape for the cantilever beams 104. Consequently, these cantilever beams 104 share the same resonant frequency. When the loudspeaker operates at this specific resonant frequency, the free end of the cantilever beam 104 experiences its maximum displacement. This phenomenon causes the sound intensity at that frequency to be significantly higher than at other frequencies, forming a "peak." This undesirable high-amplitude peak disrupts the balance of sound quality, making certain frequencies in music or speech overly prominent, sounding unnatural or harsh. Furthermore, relying on only a single frequency as the excitation source limits the loudspeaker's effective frequency bandwidth, affecting the smoothness of the frequency response curve and overall sound quality performance.

[0032] To address the aforementioned technical problems, this application provides a MEMS piezoelectric loudspeaker and acoustic device.

[0033] Reference Figure 1 , Figure 2As shown, the MEMS piezoelectric loudspeaker provided in this application embodiment includes a substrate 100 and a piezoelectric stack 101 disposed on the substrate 100; the piezoelectric stack 101 has multiple tangents 102, which extend from the geometric center 103 of the piezoelectric stack 101 to the edge of the piezoelectric stack 101 to form multiple cantilever beams 104 arranged rotationally symmetrically about the geometric center 103; the cantilever beams 104 have fixed edges 105 away from the geometric center 103; at least two cantilever beams 104 are provided with trench structures 106 on the substrate 100 corresponding to them, and the trench structures 106 are located close to the fixed edges 105 of the cantilever beams 104.

[0034] The MEMS piezoelectric loudspeaker of this embodiment includes a substrate 100 and a piezoelectric stack 101 on the substrate 100. The piezoelectric stack 101 has multiple tangents 102 extending from a geometric center 103 to its edges, dividing the piezoelectric stack 101 into multiple cantilever beams 104 arranged rotationally symmetrically about the geometric center 103. The side of each cantilever beam 104 away from the geometric center 103 is a fixed side 105. At least two cantilever beams 104 have trench structures 106 on the substrate 100, and these trench structures 106 are close to but do not directly coincide with the fixed side 105 of the cantilever beam 104. The trenches are present to adjust the strength and bending stiffness of the cantilever beams 104.

[0035] The piezoelectric stack 101 includes a bottom electrode layer 112, a piezoelectric layer 113, and a top electrode layer 114 stacked sequentially.

[0036] It should be noted that the MEMS piezoelectric speaker design reduces the bending stiffness of the cantilever beam 104 by etching a trench structure 106 on the substrate 100 of the cantilever beam 104, thereby significantly enhancing its low-frequency deformation capability, improving air coupling efficiency, optimizing the low-frequency sound pressure level curve, and achieving a more balanced and immersive audio experience.

[0037] This application embodiment achieves a significant increase in frequency bandwidth by etching and frequency-modulating the cantilever beam 104, enabling the MEMS piezoelectric speaker to generate multiple resonant excitations. Simultaneously, compared to a speaker without etching and frequency modulation, the speaker designed in this application exhibits a significantly reduced sound pressure level peak at the resonant frequency, contributing to a flatter and more stable audio response. This design not only improves sound quality but also enhances the frequency response curve uniformity of the speaker, making it suitable for demanding consumer electronics applications.

[0038] Reference Figure 8 As shown, finite element simulation analysis shows that, compared with traditional loudspeakers, the introduction of the groove structure 106 can effectively increase the low-frequency displacement of the diaphragm, significantly increasing the volume of the air being propelled, thereby improving the low-frequency response.

[0039] In this embodiment, the groove structure 106 is positioned close to the fixed edge 105, which can effectively adjust the strength of the cantilever beam 104, thereby achieving a better frequency modulation effect.

[0040] It should be noted that the groove structure 106 and the fixed edge 105 in this embodiment of the application have a certain distance between them to avoid the groove structure 106 directly coinciding with the extension path of the fixed edge 105, and to prevent the etching of the groove structure 106 from causing a significant increase in stress at the connection of the cantilever beam 104 and the fixed edge 105, thereby making the cantilever beam 104 more prone to breakage.

[0041] The technical effects of the MEMS piezoelectric loudspeaker provided in this application embodiment are as follows:

[0042] Enhanced low-frequency deformation capability: By etching trench structure 106 on substrate 100, the bending stiffness of cantilever beam 104 is reduced, enabling cantilever beam 104 to undergo greater deformation at lower frequencies, improving air coupling efficiency, optimizing low-frequency sound pressure level curve, and achieving a more balanced and immersive audio experience.

[0043] Increased frequency bandwidth: By etching and frequency-tuning the cantilever beam 104, multiple resonant excitations can be generated, significantly increasing the frequency bandwidth of the MEMS piezoelectric loudspeaker. This allows the loudspeaker to cover a wider frequency range, meeting the needs of different application scenarios.

[0044] Improved sound quality and a flatter frequency response curve: Compared to speakers without etching and frequency modulation, the speaker in this design has a significantly reduced sound pressure level peak at the resonant frequency, which helps to achieve a flatter and more stable audio response, thus improving the overall sound quality.

[0045] Preventing breakage risk: The design of maintaining a certain distance between the groove structure 106 and the fixed edge 105 avoids the risk of breakage of the cantilever beam 104 due to stress concentration, ensuring the reliability and durability of the equipment.

[0046] For example, the specific preparation method of this application embodiment includes:

[0047] S1. Select an SOI wafer as substrate 100 and etch trenches on the surface of substrate 100.

[0048] S2. Deposit silicon dioxide in the trenches of the SO I wafer and grind the surface smooth using a chemical mechanical polishing process.

[0049] S3, then deposit the bottom electrode, piezoelectric layer 113, and top electrode in sequence.

[0050] S4. Perform pre-etching, sequentially etching through the top electrode, piezoelectric layer 113, bottom electrode and support layer, and etch a release hole directly above the trench.

[0051] S5, substrate 100 back side etched cavity 108.

[0052] S6. Immerse in BOE solution to complete the release, forming cantilever beam 104.

[0053] S7. HF gas is introduced to release silicon dioxide, forming a trench structure 106, thus obtaining a MEMS piezoelectric loudspeaker.

[0054] As an optional implementation, the driving voltage of each cantilever beam 104 in this embodiment is adjusted according to the distribution of its resonant frequency. For example, when the resonant frequencies of the diaphragms of two sets of cantilever beams 104 are f0 and f1 respectively, the driving voltage within the operating frequency range of f0-f1 should be in opposite phase to the driving voltage of other frequency bands. Other cantilever beams 104 adopt an inverse driving strategy with their corresponding resonant frequencies as boundaries. This driving method in this embodiment ensures that the movement direction of each cantilever beam 104 remains consistent, thereby maximizing the volume of air pushed and significantly improving the sound output performance of the loudspeaker.

[0055] The aforementioned driving method ensures that the movement direction of each cantilever beam 104 remains consistent. This significantly increases the volume of air propelled, thereby improving the efficiency and quality of sound output. Since the speaker's sound production primarily depends on the cantilever beam 104's ability to propel air, this method effectively enhances the speaker's overall performance.

[0056] It should be noted that, due to differences in the design of the cantilever beam 104 in the embodiments of this application, their resonant frequencies are different. At the resonant frequency, the displacement of the cantilever beam 104 may undergo phase reversal. If in-phase voltage driving is continued, it may cause reverse displacement between different cantilever beams 104, thereby adversely affecting the sound output of the speaker.

[0057] Reference Figure 1 As shown, in an optional embodiment, a support structure 107 is provided on the side of the substrate 100 away from the piezoelectric stack 101. A cavity 108 is provided in the middle of the support structure 107. The support structure 107 has a connecting portion 109 that is connected to the edge of the substrate 100. The projection of the trench structure 106 on the substrate 100 coincides with the projection of the connecting portion 109 on the substrate 100.

[0058] In this embodiment, a support structure 107 is provided on the side of the substrate 100 facing away from the piezoelectric stack 101. This means that the support structure 107 is located on the back side of the entire device, that is, the side opposite to the piezoelectric stack 101. A cavity 108 is provided in the middle of the support structure 107. The presence of this cavity 108 can provide the necessary space for vibration, reduce unnecessary energy loss, and improve the flexibility and response speed of the overall structure.

[0059] The support structure 107 in this embodiment has a connecting portion 109 that connects to the edge of the substrate 100. This ensures that the support structure 107 can be firmly attached to the substrate 100, providing additional mechanical support. The projection of the trench structure 106 onto the substrate 100 partially coincides with the projection of the connecting portion 109 onto the substrate 100. By aligning a portion of the projection of the trench structure 106 with the connecting portion 109, this embodiment enhances the overall stability of the structure without affecting the movement of the cantilever beam 104.

[0060] The embodiments of this application enhance mechanical stability by increasing the overall mechanical stability of the device through the design of the support structure 107 and its connecting portion 109, thereby reducing the risk of potential damage caused by external vibration or impact. This is crucial for improving the durability and reliability of the device.

[0061] The embodiments of this application can optimize vibration characteristics by providing a cavity 108 in the support structure 107, which effectively reduces the restrictive effect of the support structure 107 on the cantilever beam 104, thereby optimizing its vibration characteristics. This helps to improve the quality of audio output, especially in the low-frequency range.

[0062] The embodiments of this application coordinate stress distribution. The design of the groove structure 106 and the projection portion of the connection 109 overlapping aims to balance the distribution of mechanical stress and avoid structural failure caused by local stress concentration. This design ensures both the effective deformation of the cantilever beam 104 and the integrity of the overall structure.

[0063] For example, refer to Figure 2 as well as Figure 3 As shown, the number of trench structures 106 is even, and they are arranged symmetrically about the geometric center 103 in pairs.

[0064] By symmetrically arranging the groove structure 106, it can be ensured that the mechanical stress generated during operation is evenly distributed on the cantilever beam 104. This avoids localized overload or material fatigue caused by stress concentration, thereby improving the reliability and service life of the equipment.

[0065] The symmetrical design of this embodiment helps to maintain a more stable and controllable vibration mode of the cantilever beam 104. This not only improves low-frequency response performance but also ensures the consistency and stability of audio output. Because the motion state of each cantilever beam 104 is similar, the possibility of phase differences and resonant frequency drift due to asymmetry is reduced.

[0066] The even-numbered and symmetrically arranged groove design simplifies the alignment steps in the manufacturing process, reducing production difficulty and cost. In this embodiment, the arrangement of the groove structure 106 in this way allows for a more balanced airflow in all directions, thereby improving the overall sound output quality. Especially for stereo or surround sound applications, the symmetrical design helps to provide a more realistic and immersive listening experience.

[0067] Reference Figure 2 As shown, as an optional implementation, the trench structure 106 includes at least two strip trenches 110; the at least two strip trenches 110 extend in parallel directions; the at least two strip trenches 110 are arranged sequentially along the direction perpendicular to the fixed edge 105, and the width of the at least two strip trenches 110 gradually decreases along the direction away from the fixed edge 105.

[0068] It should be noted that the extension directions of all the strip grooves 110 are parallel to each other. This helps to maintain a uniform effect on the cantilever beam 104 and simplifies the manufacturing process. These strip grooves 110 are arranged sequentially along a direction perpendicular to the fixed edge 105 of the cantilever beam 104.

[0069] This layout in the embodiments of this application can effectively adjust the rigidity distribution of different parts of the cantilever beam 104 from the fixed end to the free end. At least two strip grooves 110 gradually decrease in width along the direction away from the fixed edge 105. This means that the grooves closer to the fixed edge 105 are wider, while the grooves closer to the free end are narrower.

[0070] It should be noted that by changing the groove width, the bending stiffness of the cantilever beam 104 can be gradually adjusted from the fixed side 105 to the free side. The wider groove near the fixed side 105 can more significantly reduce the local stiffness, making the cantilever beam 104 more likely to deform in the low-frequency range; while the narrower groove near the free end has a relatively smaller impact on stiffness, ensuring the effective vibration of the cantilever beam 104.

[0071] This embodiment of the application reduces unnecessary resonance spikes and achieves a flatter frequency response curve by precisely controlling the stiffness distribution of each part of the cantilever beam 104. This not only improves the overall sound quality but also ensures stable performance throughout the entire operating frequency band.

[0072] This application's embodiment addresses stress concentration issues through a gradually decreasing groove width design. Wider grooves are distributed in areas subject to higher stress, i.e., near the fixed edge 105, while the gradually narrowing design avoids the risk of structural failure due to excessive material weakening, thus improving the overall mechanical reliability of the equipment.

[0073] Reference Figure 3As shown, as an optional implementation, the trench structure 106 includes at least two strip trenches 110; at least one strip trench 110 extends in a direction parallel to the fixed side 105, and at least one strip trench 110 extends in a direction intersecting with the extension direction of the fixed side 105.

[0074] It should be noted that by combining parallel and intersecting strip grooves 110, this application can more precisely control the stiffness of different parts of the cantilever beam 104. The grooves parallel to the fixed edge 105 mainly affect the overall stiffness of the cantilever beam 104, while the grooves in the intersecting direction can introduce additional flexibility or stiffness variations in local areas, thereby optimizing the overall vibration mode.

[0075] This combination design in the embodiments of this application helps to improve the frequency response curve of the loudspeaker. For example, the parallel strip grooves 110 can help reduce the stiffness of the low-frequency range and improve the low-frequency output; while the intersecting grooves can be used to fine-tune the performance of the mid-to-high frequency range, reduce unnecessary resonance peaks, and make the frequency response flatter.

[0076] This design contributes to higher quality sound output by allowing for better control over the vibration behavior of the cantilever beam 104. Especially when processing complex audio signals, the optimized frequency response provides a clearer, more natural sound reproduction.

[0077] Unlike the above implementation method, refer to Figure 4 As shown, the groove structure 106 includes a plurality of recessed holes 111; the plurality of recessed holes 111 are arranged at intervals along the extending direction of the fixed edge 105.

[0078] It should be noted that the shape of the strip groove 110 is not limited; it can be straight or curved, and those skilled in the art can choose according to their needs.

[0079] Reference Figure 5 , Figure 6 As shown, as an optional implementation, different numbers of groove structures 106 can be provided on different cantilever beams 104, so as to achieve an asymmetrical arrangement of the groove structures 106 as a whole, so as to make targeted and precise adjustment of the stiffness of each cantilever beam 104 as needed.

[0080] Additionally, different shaped groove structures 106 can be provided on the same cantilever beam 104 as needed. For example, refer to... Figure 7 As shown, the combination of the strip groove 110 and the elliptical recessed hole 111 enables the adjustment of the stiffness of the cantilever beam.

[0081] As an alternative implementation, the trench extends through the substrate 100; or, the opening of the trench structure 106 faces the piezoelectric stack 101, and the depth of the trench structure 106 is less than the thickness of the substrate 100.

[0082] It should be noted that the opening of the trench structure 106 faces the piezoelectric stack 101, and the depth of the trench structure 106 is less than the thickness of the substrate 100, that is, the trench structure 106 does not penetrate the substrate 100. This can avoid low-frequency leakage of the device and improve the SPL at low frequencies.

[0083] As an optional implementation, the piezoelectric stack 101 is a regular polygonal structure, the cantilever beam 104 is an isosceles triangle structure, and the fixed side 105 is located at the base of the isosceles triangle structure; the two ends of the groove structure 106 are respectively connected to the two sides of the isosceles triangle.

[0084] For example, refer to Figure 2 , Figure 3 As shown, the piezoelectric stack 101 has a regular quadrilateral structure with four cantilever beams 104.

[0085] For example, refer to Figure 4 As shown, the piezoelectric stack 101 has a regular hexagonal structure with six cantilever beams 104.

[0086] This application provides an acoustic device including the aforementioned MEMS piezoelectric loudspeaker and a power amplifier, wherein the power amplifier is electrically connected to the piezoelectric loudspeaker. This acoustic device incorporates the same structure and beneficial effects as the MEMS piezoelectric loudspeaker in the foregoing embodiments. The structure and beneficial effects of the MEMS piezoelectric loudspeaker have been described in detail in the foregoing embodiments and will not be repeated here.

[0087] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A MEMS piezoelectric loudspeaker, characterized in that, The system includes a substrate (100) and a piezoelectric stack (101) disposed on the substrate (100); the piezoelectric stack (101) has multiple tangents (102) extending from the geometric center (103) of the piezoelectric stack (101) to the edge of the piezoelectric stack (101) to form multiple cantilever beams (104) arranged rotationally symmetrically about the geometric center (103); the cantilever beams (104) have fixed sides (105) away from the geometric center (103); at least two of the cantilever beams (104) are provided with trench structures (106) on the substrate (100), the trench structures (106) being located close to the fixed sides (105) of the cantilever beams (104).

2. The MEMS piezoelectric loudspeaker according to claim 1, characterized in that, The substrate (100) has a support structure (107) on the side away from the piezoelectric stack (101). The support structure (107) has a cavity (108) in the middle and a connecting portion (109) that is connected to the edge of the substrate (100). The projection of the trench structure (106) on the substrate (100) coincides with the projection of the connecting portion (109) on the substrate (100).

3. The MEMS piezoelectric loudspeaker according to claim 2, characterized in that, The number of groove structures (106) is even, and they are arranged symmetrically about the geometric center (103) in pairs.

4. The MEMS piezoelectric loudspeaker according to any one of claims 1-3, characterized in that, The groove structure (106) includes at least two strip grooves (110); the at least two strip grooves (110) extend in parallel directions; the at least two strip grooves (110) are arranged sequentially along the direction perpendicular to the fixed side (105), and the width of the at least two strip grooves (110) gradually decreases along the direction away from the fixed side (105).

5. The MEMS piezoelectric loudspeaker according to any one of claims 1-3, characterized in that, The groove structure (106) includes at least two strip grooves (110); at least one of the strip grooves (110) extends in a direction parallel to the fixed side (105), and at least one of the strip grooves (110) extends in a direction intersecting with the extension direction of the fixed side (105).

6. The MEMS piezoelectric loudspeaker according to any one of claims 1-3, characterized in that, The groove structure (106) includes a plurality of recessed holes (111); the plurality of recessed holes (111) are arranged at intervals along the extension direction of the fixed side (105).

7. The MEMS piezoelectric loudspeaker according to any one of claims 1-3, characterized in that, The trench penetrates the substrate (100); or, the opening of the trench structure (106) faces the piezoelectric stack (101), and the depth of the trench structure (106) is less than the thickness of the substrate (100).

8. The MEMS piezoelectric loudspeaker according to claim 1, characterized in that, The piezoelectric stack (101) is a regular polygon structure, the cantilever beam (104) is an isosceles triangle structure, the fixed side (105) is located at the base of the isosceles triangle structure; the two ends of the groove structure (106) are respectively connected to the two sides of the isosceles triangle.

9. The MEMS piezoelectric loudspeaker according to any one of claims 1-3, characterized in that, The piezoelectric stack (101) includes a bottom electrode layer (112), a piezoelectric layer (113), and a top electrode layer (114) stacked sequentially.

10. An acoustic device, characterized in that, The invention includes the MEMS piezoelectric loudspeaker and power amplifier as described in any one of claims 1-9, wherein the power amplifier is electrically connected to the piezoelectric loudspeaker.

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