Piezoelectric MEMS sound wave emission unit with broadband response and MEMS device
By using a piezoelectric ring-high modulus thin film composite acoustic structure, the synergistic resonance of the suspended ring structure and the high Young's modulus thin film solves the problem of wide bandwidth and high sound pressure output of piezoelectric MEMS acoustic wave emitting unit, achieving high sound pressure output in the frequency range of 1kHz-500kHz, which is suitable for applications such as ultrasonic detection and miniature loudspeakers.
Patent Information
- Application Number
- CN202511232037.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-29
- Publication Date
- 2026-01-23
AI Technical Summary
Existing piezoelectric MEMS acoustic wave emitting units struggle to achieve both wide bandwidth and high sound pressure level output, limiting their application in fields such as medical ultrasound imaging, precision industrial inspection, and miniature loudspeakers.
A piezoelectric ring-high modulus film composite acoustic structure is adopted. By combining a ring-shaped piezoelectric drive unit with a high Young's modulus film, and utilizing the synergistic resonance of the suspended ring structure and the high Young's modulus film, a wide frequency response and high sound pressure output are achieved.
Achieving a wideband high sound pressure level of 60dB-150dB within the frequency range of 1kHz-500kHz improves the device's operating bandwidth and sound pressure performance, making it suitable for applications such as ultrasonic testing, imaging, and miniature loudspeakers.
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Figure CN121397441A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application relates to a piezoelectric MEMS sound wave emitting unit with wide frequency response and a MEMS device, and belongs to the technical field of micro-electro-mechanical systems (MEMS). BACKGROUND
[0002] In recent years, piezoelectric MEMS sound wave emitting units have rapidly developed under the driving of the demand for miniaturization of consumer electronics, and significant breakthroughs have been made in structural design, material systems (such as PZT, AlN, ScAlN and LiNbO3) and wafer-level manufacturing processes (such as silicon-based bonding and thin film deposition). However, the existing technology still faces various challenges, including the difficulty in balancing the wide frequency band and high emission sound pressure of the device, and the attenuation problem of the low frequency band emission sound pressure. For example, the cantilever beam structure of the traditional piezoelectric micro loudspeaker cannot balance the size reduction and low frequency sound pressure enhancement, so the frequency response flatness and sound quality need to be improved. For another example, traditional ultrasonic detection / imaging requires ultrasonic waves with wide frequency response and high emission sound pressure to achieve high axial resolution and large detection distance. These key technical problems restrict the application effect of piezoelectric MEMS sound wave emitting units in the fields of medical ultrasonic imaging, precision industrial detection and micro loudspeakers. Existing research generally uses resonant unit arrays, phase modulation driving or other special structures to expand the working bandwidth, which not only cannot fundamentally improve the frequency band and emission sound pressure of the device, but also increases the complexity of the device and the driving circuit. SUMMARY
[0003] In order to solve the problem that the existing technology of the traditional piezoelectric MEMS sound wave emitting unit cannot balance the wide frequency band response and high sound pressure output, the application provides a technical scheme of a piezoelectric MEMS sound wave emitting unit with wide frequency response, which uses a piezoelectric ring-high modulus film composite acoustic structure, uses a ring-shaped piezoelectric driving unit and a high Young's modulus film in combination, and through the synergistic effect of the ring structure resonance and the film structure, the high-efficiency driving characteristic is retained, and the wide frequency response advantage is combined, so that the working bandwidth is expanded while the sound pressure output performance is significantly improved.
[0004] The application adopts the following technical scheme:
[0005] According to the first aspect of the application, a piezoelectric MEMS sound wave emitting unit with wide frequency response is provided, which comprises a composite vibration structure and a support layer arranged from top to bottom.
[0006] A cavity is formed in the support layer, and the cavity extends to the lower side end face of the composite vibration structure.
[0007] The composite vibration structure comprises a high Young's modulus film and a suspended ring structure, and the high Young's modulus film covers the suspended ring structure.
[0008] The suspended ring structure comprises an upper electrode, a piezoelectric layer, and a lower electrode arranged from top to bottom, and comprises a ring-shaped region, a peripheral frame region arranged around the ring-shaped region, and a support beam region in the horizontal direction;
[0009] The ring-shaped region is a ring-shaped area surrounded by an outer contour and an inner contour;
[0010] The ring-shaped region is connected to the peripheral frame region by at least two support beam regions;
[0011] The ring-shaped region is suspended above the cavity.
[0012] Optionally, the high Young's modulus film has a Young's modulus greater than or equal to 50 GPa.
[0013] Optionally, the high Young's modulus film has a thickness of 100 nm to 1000 nm.
[0014] Optionally, the piezoelectric layer has a thickness of 0.3 μm to 10 μm.
[0015] Optionally, the inner contour and the outer contour are concentrically arranged.
[0016] Optionally, the shapes of the inner contour and the outer contour independently comprise a circle, a square, and a polygon.
[0017] Optionally, the inner contour has an equivalent diameter of 100 μm to 4000 μm.
[0018] Optionally, the outer contour has an equivalent diameter of 300 μm to 5000 μm.
[0019] Optionally, the ring-shaped region has a width of 100 μm to 2450 μm.
[0020] Optionally, the ring-shaped region is connected to the peripheral frame region by two symmetrically arranged support beam regions.
[0021] Optionally, at a distance of 1000 μm from the surface of the piezoelectric MEMS acoustic wave transmitting unit having a wide frequency response, the sound pressure level is 60 dB to 150 dB within a frequency of 1 kHz to 500 kHz.
[0022] According to a second aspect of the present application, a MEMS device is provided, comprising the piezoelectric MEMS acoustic wave transmitting unit having a wide frequency response according to the first aspect described above.
[0023] The beneficial effects of the present application include:
[0024] (1) Wide frequency band and high sound pressure output
[0025] The piezoelectric MEMS sound wave emitting unit with wide frequency response provided in the application realizes wide frequency band (1 kHz-500 kHz) high sound pressure (60-150 dB) output through the composite resonance structure of the suspended ring structure and the high Young's modulus film, and overcomes the problems of narrow frequency band and serious low frequency attenuation of the traditional piezoelectric device; the radial vibration of the ring structure and the out-of-plane vibration of the film are coupled to excite multiple resonance peaks, so that the sound pressure level remains high (>100 dB) in a wide frequency range. The high Young's modulus materials such as graphene, diamond and silicon carbide are used as the film, and the rigid boundary of the film optimizes the radiation efficiency of the vibration energy and improves the overall sound pressure output.
[0026] (2) Flexible size and frequency
[0027] The piezoelectric MEMS sound wave emitting unit with wide frequency response provided in the application uses conventional MEMS materials as the support layer, which is suitable for large-scale production. The structure size is flexible and adjustable, the frequency is designed as needed, and it is suitable for different application scenarios, such as ultrasonic imaging, nondestructive testing, piezoelectric MEMS loudspeaker, etc. BRIEF DESCRIPTION OF DRAWINGS
[0028] Figure 1 FIG. 1 is a cross-sectional structure diagram of the piezoelectric MEMS sound wave emitting unit with wide frequency response in the embodiments of the application;
[0029] Figure 2 FIG. 3 is a comparison diagram of the piezoelectric MEMS sound wave emitting unit structure in the embodiments of the application, wherein (a) is a perspective diagram of the piezoelectric MEMS sound wave emitting unit without covering the high Young's modulus film, and (b) is a perspective diagram of the piezoelectric MEMS sound wave emitting unit with wide frequency response and covering the high Young's modulus film;
[0030] Figure 3 FIG. 4 is a sound pressure level-frequency response characteristic simulation diagram of the piezoelectric MEMS sound wave emitting unit with wide frequency response in the embodiments of the application. DETAILED DESCRIPTION
[0031] The application will be described in detail below with reference to the embodiments, but the application is not limited to these embodiments.
[0032] Unless otherwise specified, the raw materials in the embodiments of the application are purchased through commercial channels.
[0033] Unless otherwise specified, the test methods all use conventional methods, and the instrument settings all use the recommended settings of the manufacturers.
[0034] Traditional piezoelectric MEMS acoustic wave transmitting units often have difficulty in meeting the dual requirements of wide frequency band response and high sound pressure output, which seriously restricts their application in the fields of ultrasonic detection and miniature loudspeakers. Specifically, the existing piezoelectric MEMS acoustic wave transmitting units mostly have a single vibration mode, which limits their working bandwidth, and they can usually only maintain effective output near the center frequency; in addition, the multi-resonance unit design used in the prior art to expand the bandwidth not only greatly increases the device size, but also introduces complex modal interference problems. Limited by the above-mentioned technologies, the current piezoelectric MEMS acoustic wave transmitting units are difficult to meet the growing performance requirements, making it difficult for them to fully exert their application potential in the fields of medical imaging, industrial detection, TWS earphone and other wearable device loudspeakers. In order to solve the foregoing technical problems, the present application proposes a piezoelectric MEMS acoustic wave transmitting unit adopting a piezoelectric ring-high modulus film composite acoustic structure, which uses a design scheme of combining a ring-shaped piezoelectric driving unit with a high Young's modulus film. The core of this structure is to optimize the device performance by optimizing the vibration coupling mechanism, achieving the coordinated improvement of wide frequency band and high sound pressure output: the ring-shaped piezoelectric structure produces radial vibration under the action of an external electric field, and the vibration energy of the piezoelectric ring-shaped structure can be efficiently transmitted to the film to excite the out-of-plane vibration mode of the film. Through the synergistic effect of the ring structure itself and the film structure, the efficient driving characteristics are retained, and the wide frequency response advantage is also possessed, so that the working bandwidth is expanded while the sound pressure output performance is significantly improved.
[0035] Based on this, the present application provides a piezoelectric MEMS acoustic wave transmitting unit with wide frequency response and a MEMS device. The piezoelectric MEMS acoustic wave transmitting unit with wide frequency response adopts a piezoelectric ring-high modulus film composite acoustic structure, which uses a resonant structure composed of a suspended ring and a high Young's modulus film to achieve wide frequency band and high sound pressure output.
[0036] According to an embodiment of the present application, the piezoelectric MEMS acoustic wave transmitting unit with wide frequency response has a structure schematic diagram as shown in Figure 1 from top to bottom, including a composite vibration structure, a support layer;
[0037] A cavity is opened on the support layer, and the cavity extends to the lower side end surface of the composite vibration structure;
[0038] The composite vibration structure includes a high Young's modulus film and a suspended ring structure, and the high Young's modulus film covers the suspended ring structure;
[0039] The suspended ring structure includes an upper electrode, a piezoelectric layer and a lower electrode arranged from top to bottom, and the suspended ring structure includes a ring-shaped area, a peripheral frame area arranged around the ring-shaped area, and a support beam area in the horizontal direction;
[0040] The ring-shaped area is a ring-shaped area surrounded by an outer contour and an inner contour;
[0041] The annular region is connected to the peripheral frame region by at least two support beam regions;
[0042] The annular region is suspended above the cavity.
[0043] In one embodiment, the high Young's modulus film has a Young's modulus greater than or equal to 50 GPa. The high Young's modulus film is composed of a high Young's modulus material, including but not limited to graphene, diamond, silicon carbide, and a Young's modulus that is too low will not be conducive to resonant coupling, affecting the vibration effect.
[0044] In one embodiment, the high Young's modulus film has a thickness of 100 nm to 1000 nm. This thickness range is used to form a resonant coupling effect between the annular, which helps to achieve a wide frequency response and improve the sound pressure level of the emitted sound.
[0045] In one embodiment, the piezoelectric layer has a thickness of 0.3 μm to 10 μm. This range is an easy-to-achieve thickness range using existing technology, and a thickness that is too small is difficult to process and high in cost, and a thickness that is too large will affect the vibration amplitude.
[0046] In one embodiment, the piezoelectric layer is a conventional MEMS material, and the specific selection is not strictly limited, for example, it can be PZT, LiNbO3, LiTaO3, ScAlN, AlN.
[0047] In one embodiment, the inner contour and the outer contour are concentrically arranged.
[0048] In one embodiment, the shape of the inner contour and the outer contour independently includes a circle, a square, and a polygon. The rings formed by different shape contours have similar effects.
[0049] In one embodiment, the equivalent diameter of the inner contour is 100 μm to 4000 μm.
[0050] The equivalent diameter of the outer contour is 300 μm to 5000 μm.
[0051] In one embodiment, the width of the annular region is 100 μm to 2450 μm.
[0052] If you want to move to a lower frequency, you need to increase the size and thickness, and if you want to move to a higher frequency, you need to reduce the size and thickness. The above size range can cover the emission frequency of the sound wave emission unit from audible sound to ultrasonic.
[0053] The annular region on the piezoelectric layer serves as the vibration main body, and the suspended annular structure serves to support the high Young's modulus film and drive the high Young's modulus film to vibrate.
[0054] In one embodiment, the annular region is connected to the peripheral frame region by two symmetrically arranged support beam regions.
[0055] In one embodiment, the connection between the annular region and the peripheral frame region by at least two support beam regions can be fixed connection.
[0056] In one embodiment, the length of the support beam region is 10-1000 microns, and the width of the support beam region is 10-3000 microns. The support beam is used to realize the suspended annular structure to form an elastic suspended structure.
[0057] In one embodiment, the materials of the upper electrode and the lower electrode are not strictly limited, for example, they can be aluminum (Al), platinum (Pt), gold (Au), and chromium (Cr).
[0058] In one embodiment, the thickness of the upper electrode and the lower electrode is 100-500 nm.
[0059] In one embodiment, the material of the support layer is a conventional material, for example, it can be silicon, glass, and silicon carbide.
[0060] In one embodiment, the thickness of the support layer is 50-5000 microns. When an alternating voltage is applied between the upper electrode and the lower electrode, the piezoelectric layer generates a reverse piezoelectric effect, driving the suspended annular region to vibrate radially. The resonant frequency of the annular region is determined by the width of the ring and the material stiffness. The high Young's modulus film forms a composite resonant mode with the annular region, amplifying the vibration displacement of the annular region, improving the sound pressure level and the frequency response range.
[0061] In one embodiment, within the frequency range of 1 kHz-500 kHz, the sound pressure level at a distance of 1000 microns from the surface of the piezoelectric MEMS acoustic wave transmitting unit with wide frequency response is 60-150 dB. The overall structural design of the piezoelectric MEMS acoustic wave transmitting unit with wide frequency response in this application is compatible with standard MEMS process. While maintaining the miniaturization of the device, the working bandwidth and sound pressure output performance are significantly improved. This technical solution is particularly suitable for professional fields such as ultrasonic detection / imaging and piezoelectric MEMS loudspeakers, and provides a new technical path for the development of high-performance piezoelectric micro-mechanical acoustic wave transmitting units.
[0062] In one of the embodiments, the piezoelectric MEMS acoustic wave transmitting unit with wide frequency response can be applied to micro-speakers (such as TWS earphones, smart glasses), medical ultrasonic imaging, industrial non-destructive testing, and multi-functional acoustic system integration, etc. requiring wide frequency band and high sound pressure output. The design of the piezoelectric MEMS acoustic wave transmitting unit with wide frequency response in the present application can achieve a wider frequency response range and higher sound pressure output when applied to the aforementioned fields, providing superior signal quality and resolution for ultrasonic detection and providing high-quality audio effects for micro-speakers. This structure significantly improves the overall performance of the traditional piezoelectric acoustic wave transmitting unit while maintaining the miniaturization of the device.
[0063] According to another embodiment of the present application, a MEMS device is also provided, comprising a piezoelectric MEMS acoustic wave transmitting unit with wide frequency response as described above.
[0064] Embodiment 1
[0065] The piezoelectric MEMS acoustic wave transmitting unit with wide frequency response comprises a composite vibration structure, a support layer, wherein a cavity is formed in the support layer and extends to the lower side of the composite vibration structure, the composite vibration structure comprises a high Young's modulus film and a suspended ring structure, the suspended ring structure comprises an upper electrode, a piezoelectric layer, and a lower electrode arranged from top to bottom, and the high Young's modulus film covers the suspended ring structure.
[0066] When the high Young's modulus film is not covered, the schematic diagram of the appearance structure of the MEMS acoustic wave transmitting unit is shown in Figure 2 (a), the suspended ring structure comprises a ring area, a peripheral frame area arranged around the ring area, and a support beam area in the horizontal direction, the ring area is a ring-shaped area surrounded by an outer contour and an inner contour, the shapes of the outer contour and the inner contour are independently circular and concentrically arranged, the ring area and the peripheral frame area are fixedly connected through the two symmetrically arranged support beam areas, and the high Young's modulus film covers the ring area, and the ring area is suspended above the cavity. When the high Young's modulus film is covered, the schematic diagram of the appearance structure of the piezoelectric MEMS acoustic wave transmitting unit with wide frequency response is shown in Figure 2 (b), the high Young's modulus film covers the surface of the suspended ring structure.
[0067] The structure of the piezoelectric MEMS acoustic wave transmitting unit is analyzed by finite element simulation to obtain the sound pressure level-frequency response characteristics. The specific materials and structure size ranges of the piezoelectric MEMS acoustic wave transmitting unit in the simulation analysis process are set as follows:
[0068] The high Young's modulus film is a silicon carbide film with a thickness of 100-1000 nm.
[0069] The piezoelectric layer is made of LiNbO3 with a thickness of 0.3 μm-10 μm.
[0070] In the annular region, the equivalent diameter of the inner contour is 100μm-4000μm, the equivalent diameter of the outer contour is 300μm-5000μm, and the width of the annular region is 100μm-2450μm.
[0071] The length of the support beam area is 10μm-1000μm, and the width of the support beam area is 10μm-3000μm;
[0072] The upper electrode is made of platinum (Pt) and has a thickness of 100nm-500nm;
[0073] The lower electrode is made of gold (Au) and has a thickness of 100nm-500nm;
[0074] The support layer is made of silicon and has a thickness of 50μm-5000μm.
[0075] The results showed that as the size and thickness of each layer of the structure changed, the characteristic frequency would inevitably shift, but the overall structure still had a wideband response.
[0076] Typical results are as follows Figure 3 As shown, the curve reflects the sound pressure level response at a distance of 1000 μm from the device surface. The horizontal axis represents frequency (1 kHz - 500 kHz), and the vertical axis represents sound pressure level (dB). The device's first resonant frequency is 42 kHz. In the low-frequency range of 1 kHz to 30 kHz, the sound pressure level remains above 60 dB. Near the first resonant frequency, the sound pressure level can reach above 120 dB. Afterward, multiple resonant peaks appear in the high-frequency range, with the sound pressure level fluctuating in the range of 100 dB to 150 dB. This confirms that the composite structure of the suspended ring structure and the high Young's modulus film in the composite vibration structure produces a synergistic resonance effect, enabling wideband high sound pressure output. The rigid boundary constraint of the film efficiently converts the vibration energy of the ring structure into out-of-plane acoustic radiation, suppressing low-frequency energy dissipation. The introduction of the high Young's modulus film produces the following synergistic effects: First, by converting the radial vibration of the ring region into out-of-plane vibration of the film, air damping loss is reduced, increasing the sound pressure level; second, using a high Young's modulus film material enables a wideband response. Furthermore, by covering the annulus with a thin film, the radial vibration of the annular region is converted into out-of-plane vibration of the film. Therefore, the shape of the annular region can be circular or polygonal, with essentially the same effect.
[0077] In summary, the application uses the composite resonance structure to achieve a wide frequency high sound pressure output of 60dB-150dB within the frequency of 1kHz-500kHz through the synergistic design of the suspended ring structure and the high Young's modulus film, and is particularly suitable for the fields of ultrasonic imaging, industrial nondestructive testing, piezoelectric MEMS loudspeakers, etc. By adjusting the thickness and size of the ring structure, the improved piezoelectric acoustic wave emitting unit can be flexibly applied to various frequency bands, such as the field of micro loudspeakers, thereby making up for the defect of insufficient low-frequency sound pressure level. The piezoelectric ring-high modulus film composite acoustic structure of the application provides a high yield, wide frequency and high sound pressure level scheme, and has significant industrial application value.
[0078] The above is only a few embodiments of the application, and does not limit the application in any form. Although the preferred embodiments are disclosed above, the application is not limited thereto. Any person skilled in the art can make some changes or modifications to the disclosed technical content without departing from the scope of the application, and such changes or modifications are equivalent to equivalent embodiments, and are within the scope of the technical solution.
Claims
1. A piezoelectric MEMS acoustic wave transmitting unit having a wide frequency response, characterized by, The composite vibration structure, a support layer arranged from top to bottom; A cavity is formed in the support layer, and the cavity extends to the lower end surface of the composite vibration structure; The composite vibration structure comprises a high Young's modulus film and a suspended ring structure, and the high Young's modulus film covers the suspended ring structure; The suspended ring structure comprises an upper electrode, a piezoelectric layer, and a lower electrode arranged from top to bottom, and the suspended ring structure comprises a ring region, a peripheral frame region arranged outside the ring region, and a support beam region in the horizontal direction; The ring region is a ring-shaped region surrounded by an outer contour and an inner contour; the ring region is connected to the peripheral frame region through at least two support beam regions; The ring region is suspended above the cavity.
2. The piezoelectric MEMS acoustic wave launch unit with wide frequency response of claim 1, wherein, The Young's modulus of the high Young's modulus film is greater than or equal to 50 GPa.
3. The piezoelectric MEMS acoustic wave launch unit with wide frequency response of claim 1, wherein, The thickness of the high Young's modulus film is 100 nm-1000 nm.
4. The piezoelectric MEMS acoustic wave launch unit with wide frequency response of claim 1, wherein, The thickness of the piezoelectric layer is 0.3 μm-10 μm.
5. The piezoelectric MEMS acoustic wave launch unit with wide frequency response of claim 1, wherein, The inner contour and the outer contour are concentrically arranged.
6. The piezoelectric MEMS acoustic wave launch unit with wide frequency response of claim 1, wherein, The shapes of the inner contour and the outer contour independently comprise a circle, a square, and a polygon.
7. The piezoelectric MEMS acoustic wave launch unit with wide frequency response of claim 1, wherein, The equivalent diameter of the inner contour is 100 μm-4000 μm; The equivalent diameter of the outer contour is 300 μm-5000 μm.
8. The piezoelectric MEMS acoustic wave launch unit with wide frequency response of claim 1, wherein, The width of the ring region is 100 μm-2450 μm.
9. The piezoelectric MEMS acoustic wave launch unit with wide frequency response of claim 1, wherein, The ring region is connected to the peripheral frame region through two symmetrically arranged support beam regions.
10. A MEMS device, characterized by The piezoelectric MEMS acoustic wave transmitting unit with wide frequency response comprises the piezoelectric MEMS acoustic wave transmitting unit according to any one of claims 1 to 9.