MEMS loudspeaker with self-sealing back cavity
By creating a release hole on the MEMS speaker diaphragm and forming a low-pressure sealed chamber, the problems of large speaker size and air damping effect are solved, achieving higher sound output quality and lower distortion rate.
Patent Information
- Application Number
- CN202423258100.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-26
- Publication Date
- 2025-12-02
- Estimated Expiration
- 2034-12-26
AI Technical Summary
Existing MEMS loudspeakers have an excessively large overall size due to the large back cavity designed to optimize diaphragm vibration, and the air damping affects the vibration performance.
A release hole is made on the diaphragm, which connects to the cavity on the supporting base to form a low-pressure sealed chamber. This reduces the air pressure inside the chamber, decreases air damping, promotes the rapid transfer of vibration energy, and optimizes the sound output quality and efficiency.
Achieving higher sound output quality and lower distortion in a smaller volume improves the speaker's response speed and sound quality.
Smart Images
Figure CN223625997U_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of microelectromechanical systems (MEMS) technology, and more specifically, to a MEMS loudspeaker with a self-sealing back cavity. Background Technology
[0002] MEMS loudspeakers, as key components for sound conversion and transmission, are centered on their highly integrated diaphragm structure. This structure achieves efficient sound wave transmission and reception by precisely controlling the vibration frequency and amplitude of the diaphragm.
[0003] Existing MEMS loudspeakers typically feature large back cavities to optimize diaphragm vibration and reduce the impact of air damping on vibration performance. The size of the back cavity is often proportional to the mass of the loudspeaker diaphragm, usually requiring several hundred cubic millimeters (e.g., 200 mm³) to ensure the diaphragm can vibrate freely and stably. The back cavity volume is much larger than the volume of the MEMS device itself (typically 10 mm²). 3 (Left and right), resulting in a large overall size of the speaker. Utility Model Content
[0004] To overcome the problem that existing MEMS loudspeakers typically have a large back cavity to optimize diaphragm vibration and reduce the impact of air damping on vibration, but the back cavity design leads to a large overall loudspeaker size, this invention provides a MEMS loudspeaker with a self-sealing back cavity.
[0005] The technical solution of this utility model is as follows:
[0006] A MEMS loudspeaker with a self-sealing back cavity, the MEMS loudspeaker comprising:
[0007] A supporting base having a cavity formed thereon;
[0008] A diaphragm, which covers the supporting substrate, has a release hole partially or entirely formed therein, and the release hole communicates with the cavity;
[0009] When a release hole is opened in part of the diaphragm, the diaphragm without a release hole is sealed and covered on the diaphragm with the release hole, so that the cavity opened on the support substrate and the release hole opened on the diaphragm form a low-pressure sealed chamber.
[0010] When all the diaphragms have release holes, a sealing layer is sealed on top of the diaphragm so that the cavity on the supporting base and the release holes on the diaphragm form a low-pressure sealed chamber.
[0011] The low-pressure sealed chamber has a pressure lower than standard atmospheric pressure, and the diaphragm is provided with electrically drivable electrodes and / or functional materials.
[0012] According to the above-described scheme of this utility model, the pressure of the low-pressure sealed chamber is a vacuum.
[0013] According to the present invention based on the above scheme, a circuit board is provided on the side of the supporting substrate away from the diaphragm, and the electrodes on the diaphragm are connected to the circuit board through connecting wires.
[0014] According to the present invention based on the above scheme, the diaphragm includes a support layer and a piezoelectric layer. The support layer is disposed on the surface of the support substrate and is sealed and covered on the support substrate. The piezoelectric layer is disposed on the support layer.
[0015] According to the above-described scheme of this utility model, the top and bottom surfaces of the piezoelectric layer are formed with metal conductive layers, and the top and bottom metal conductive layers are respectively connected to the circuit board through the connecting lines.
[0016] According to the present invention based on the above scheme, the support layer is provided with the release hole.
[0017] According to the present invention based on the above scheme, the support layer, the piezoelectric layer, and the metal conductive layers disposed on the top and bottom surfaces of the piezoelectric layer are all provided with the release hole, and the sealing layer is disposed on the metal conductive layer on the top surface of the piezoelectric layer.
[0018] According to the above-described scheme of this utility model, the depth of the cavity is less than 1 mm.
[0019] According to the above-described scheme of this utility model, the depth of the cavity is less than 500 micrometers.
[0020] According to the above-described scheme of this utility model, the depth of the cavity is less than 5 micrometers.
[0021] According to the above-described scheme of this utility model, the surface of the piezoelectric layer is covered with an insulating layer.
[0022] According to the above-described scheme of this utility model, the supporting substrate is made of silicon or glass.
[0023] According to the above-described solution, the beneficial effects of this utility model are as follows: by opening a release hole on the diaphragm, which connects to the cavity on the supporting substrate, the vibration on the diaphragm can be transmitted to the cavity more quickly through the release hole, promoting the rapid transmission of vibration energy and optimizing the quality and efficiency of sound output. Furthermore, the low-pressure sealed chamber formed by the release hole and the cavity further accelerates the vibration transmission process and reduces energy loss, enabling the MEMS loudspeaker to achieve higher sound output quality and lower distortion rate in a smaller volume. Attached Figure Description
[0024] Figure 1Top view of the planar structure of this utility model;
[0025] Figure 2 for Figure 1 A side view cut along line AA.
[0026] Figure 3 for Figure 1 A partial cross-sectional view of Example 1, cut along line AA.
[0027] Figure 4 for Figure 1 A partial cross-sectional view of Example 2, cut along line AA.
[0028] Figure 5 The frequency response curves of the MEMS speaker of this invention and existing MEMS speakers are shown.
[0029] In the figure, the various attached figures are labeled as follows:
[0030] 100, Supporting substrate; 101, Cavity; 200, Diaphragm; 201, Release hole; 202, Supporting layer; 203, Piezoelectric layer; 204, First conductive metal layer; 205, Second conductive metal layer; 300, Sealing layer; 400, Circuit board; 500, Connecting wire. Detailed Implementation
[0031] To make the technical problems, technical solutions and beneficial effects of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments.
[0032] It should be noted that the terms "comprising" and "having," and any variations thereof, in the specification and claims of this utility model are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices. Terms such as "set up" should be interpreted broadly; for example, it can refer to a fixed connection, a detachable connection, or an integral part; it can refer to a mechanical connection or an electrical connection; it can refer to a direct connection or an indirect connection through an intermediate medium; it can refer to the internal communication of two elements or the interaction between two elements, unless otherwise expressly defined. Terms such as "upper," "lower," "left," "right," "front," "rear," and "bottom" indicate orientations or positions based on the orientations or positions shown in the accompanying drawings, and are only for ease of description and should not be construed as limiting the present technical solution.
[0033] It should be noted that existing MEMS loudspeakers typically feature a large back cavity to optimize diaphragm vibration and reduce the impact of air damping on the vibration effect. The size of the back cavity is often proportional to the mass of the loudspeaker diaphragm, and is usually required to reach several hundred cubic millimeters (e.g., 200 mm³) to ensure that the diaphragm can vibrate freely and stably. The back cavity volume is much larger than the volume of the MEMS device itself (typically 10 mm²). 3 (Left and right), resulting in a large overall size of the speaker.
[0034] like Figures 1-5 As shown, this embodiment provides a MEMS loudspeaker with a self-sealing back cavity. By opening a release hole 201 on the diaphragm 200, the release hole 201 connects to the cavity 101 on the support substrate 100. Vibrations on the diaphragm 200 can be transmitted to the cavity 101 more quickly through the release hole 201, promoting the rapid transmission of vibration energy and optimizing the quality and efficiency of sound output. Furthermore, the low-pressure sealed chamber formed by the release hole 201 and the cavity 101 further accelerates the vibration transmission process and reduces energy loss, enabling the MEMS loudspeaker to achieve higher sound output quality and lower distortion rate in a smaller volume.
[0035] Specifically, the MEMS loudspeaker includes a support substrate 100 and a diaphragm 200, wherein a cavity 101 is formed on the support substrate 100;
[0036] The diaphragm 200 is sealed and covered on the support base 100. The diaphragm 200 is partially or entirely provided with a release hole 201, which connects to the cavity 101. The release hole 201 acts as a bridge connecting the diaphragm 200 and the cavity 101, which not only promotes the rapid transmission of vibration energy, but also optimizes the quality and efficiency of sound output through its unique layout.
[0037] When a portion of the diaphragm 200 has a release hole 201, the diaphragm 200 without the release hole 201 seals over the diaphragm 200 with the release hole 201, so that the cavity 101 on the supporting substrate 100 and the release hole 201 on the diaphragm 200 form a low-pressure sealed chamber; the area of the diaphragm 200 without the release hole 201 serves as a sealing layer 300, directly covering the diaphragm 200 with the release hole 201. By forming a low-pressure sealed chamber with the release hole 201 and the cavity 101, the air pressure inside the chamber is effectively reduced, enhancing the response speed and vibration amplitude of the diaphragm 200.
[0038] When all the diaphragms 200 have release holes 201, a sealing layer 300 is sealed and covered on the top of the diaphragm 200 so that the cavity 101 on the support base 100 and the release holes 201 on the diaphragm 200 form a low-pressure sealed chamber.
[0039] The low-pressure sealed chamber has a pressure lower than standard atmospheric pressure, which significantly reduces air damping, allowing the diaphragm 200 to vibrate more rapidly and freely under electrical signal drive, thereby reducing distortion and improving sound quality. The diaphragm 200 is equipped with electrically drivable electrodes and / or functional materials.
[0040] The working principle is as follows: When an electrical signal is applied to the electrodes on the diaphragm 200, the diaphragm 200 vibrates under the influence of an electric or magnetic field. Due to the presence of the release hole 201, the vibration energy on the diaphragm 200 can be rapidly transferred to the cavity 101 inside the supporting base 100, forming sound waves. At the same time, the low-pressure sealed chamber further accelerates the vibration transmission process, reduces energy loss, and enables the loudspeaker to achieve higher sound output quality and lower distortion rate in a smaller volume.
[0041] Figure 5 The figures show the frequency response curves of the MEMS loudspeaker and the conventional loudspeaker in this embodiment. It is clear from the figures that the smaller the back cavity of the conventional piezoelectric MEMS loudspeaker, the higher the resonant frequency and the lower the sound pressure level. Compared to the conventional piezoelectric MEMS loudspeaker, the piezoelectric MEMS loudspeaker with a low-pressure sealed cavity achieves a 5dB higher sound pressure level at the same resonant frequency, and requires no additional back cavity, thus reducing the loudspeaker size.
[0042] In one embodiment, the pressure of the low-pressure sealed chamber is a vacuum or near-vacuum. In other instances of implementation, the pressure in the low-pressure sealed chamber may be less than about 50% of standard atmospheric pressure. It is also possible that the pressure in the low-pressure sealed chamber may be less than about 45%, 40%, 35%, 30%, 25%, or 20% of standard atmospheric pressure (standard atmospheric pressure is typically 101.325 kPa or 1013.25 mbar). The pressure in the low-pressure sealed chamber may also be expressed as an absolute pressure, such as less than 50 kPa, less than 40 kPa, less than 30 kPa, or less than 25 kPa. In any case, the pressure of the low-pressure sealed chamber may typically be selected as a range that is below standard atmospheric pressure, which is appropriate for the weather conditions that should be reasonably expected for the MEMS microphone to be used and relative to altitude (e.g., up to 9000 meters above sea level).
[0043] In one embodiment, a circuit board 400 is provided on the side of the support substrate 100 away from the diaphragm 200, and electrodes on the diaphragm 200 are connected to the circuit board 400 via connecting lines 500. The circuit board 400 is responsible for receiving audio signals and transmitting them to the electrodes. When the audio signal passes through the electrodes, it generates a changing electric or magnetic field, which in turn drives the diaphragm 200 to vibrate according to the waveform of the audio signal. This vibration then pushes the surrounding air molecules, generating sound waves, which are the sounds we hear.
[0044] The diaphragm 200 includes a support layer 202 and a piezoelectric layer 203. The support layer 202 is deposited on the surface of the support substrate 100 and seals over the cavity 101 of the support substrate 100, thereby forming a low-pressure sealed chamber. The piezoelectric layer 203 is deposited on the support layer 202 and deforms when subjected to an electric field, thereby generating sound. To improve the conversion efficiency and stability of the piezoelectric layer 203, conductive metal layers are deposited on both the top and bottom surfaces of the piezoelectric layer 203 to form an electrode structure. The top and bottom conductive metal layers are connected to the circuit board 400 via connecting lines 500, realizing the input and output of audio signals.
[0045] To prevent short circuits between the top and bottom conductive metal layers and to protect the electrodes and connecting wires 500 from external environmental influences, an insulating layer is applied to the surface of the piezoelectric layer 203 to ensure the connection and shielding of the top and bottom conductive metal layers on the connecting wires 500. Example
[0046] The support layer 202 is provided with a release hole 201, and the piezoelectric layer 203 and the top and bottom metal conductive layers are sealed and covered on the support layer 202. The release hole 201 is provided on the support layer 202. When a voltage is applied, the piezoelectric layer 203 will deform, thereby generating vibration. The vibration energy can be quickly transmitted to the cavity 101 inside the support substrate 100 to form sound waves.
[0047] The specific process flow is as follows:
[0048] A cavity 101 is fabricated on a support substrate 100, wherein the material of the support substrate 100 may be selected from, but is not limited to, monocrystalline silicon; a filling layer is used to cover the cavity 101 of the support substrate 100, and the upper surface of the filling layer is made substantially flush with the surface of the support substrate 100 located around the cavity 101 through processes such as grinding; a support layer 202 is deposited on the surface of the support substrate 100 and the surface of the filling layer; a release hole 201 is formed on the support layer 202 by etching, and the filling layer is removed to expose the cavity 101; a second [missing information] is deposited on the surface of the support layer 202. A metal conductive layer 205 is formed to create the bottom electrode structure. During deposition, a vacuum or low-pressure environment is maintained to create a low-pressure sealed back cavity for the cavity 101 and the release hole 201. The bottom electrode is then etched. A piezoelectric layer 203 is deposited on the surface of the second metal conductive layer 205 and etched to form the piezoelectric layer 203 structure. A first metal conductive layer 204 is deposited on the surface of the piezoelectric layer 203 and etched to form the top electrode structure. The electrodes on the diaphragm 200 are connected to the contacts on the circuit board 400 via connecting lines 500. Finally, the entire MEMS speaker is packaged to protect the internal structure and circuitry from external environmental influences. This requires depositing insulating materials (such as silicon dioxide or silicon nitride) on the surfaces of the piezoelectric layer 203 and the metal conductive layer to protect the electrodes and connecting lines 500. Example
[0049] Release holes are provided on the support layer 202, the piezoelectric layer 203, and the metal conductive layers on both the top and bottom surfaces of the piezoelectric layer 203. The sealing layer 300 is provided on the metal conductive layer on the top surface of the piezoelectric layer 203. When a voltage is applied, the piezoelectric layer 203 will deform, thereby generating vibration. The vibration energy can be directly transmitted to the cavity 101 inside the support substrate 100 through the release hole 201, forming sound waves.
[0050] The specific process flow is as follows:
[0051] A cavity 101 is fabricated on a support substrate 100, wherein the material of the support substrate 100 may be selected, but is not limited to, single-crystal silicon; a filling layer is used to cover the cavity 101 of the support substrate 100, and the upper surface of the filling layer is made substantially flush with the surface of the support substrate 100 located around the cavity 101 through processes such as grinding; a support layer 202 is deposited on the surface of the support substrate 100 and the surface of the filling layer; a second metal conductive layer 205 is deposited on the surface of the support layer 202 to form a bottom electrode structure, and then etched; a stamping layer is deposited on the surface of the second metal conductive layer 205. The piezoelectric layer 203 material is used to form the piezoelectric layer 203 structure, and then etched. A first conductive metal layer 204 is deposited on the surface of the piezoelectric layer 203 to form the top electrode structure, and then etched. The support layer 202 is etched to form a connected release hole 201 or slit, and the filling layer is removed to expose the cavity 101. During the etching process, a vacuum or low-pressure environment is maintained, and a sealing layer is deposited to connect the cavity 101 and the release hole 201 to form a low-pressure sealed back cavity. The electrodes on the diaphragm 200 are connected to the contacts on the circuit board 400 through the connecting line 500. Finally, the entire MEMS speaker is packaged to protect the internal structure and circuit system from the influence of the external environment. This requires depositing an insulating layer material (such as silicon dioxide, silicon nitride, etc.) on the surfaces of the piezoelectric layer 203 and the conductive metal layer to protect the electrodes and the connecting line 500.
[0052] In one embodiment, the depth of cavity 101 is less than 1 mm. When the depth of cavity 101 is set below 1 mm, the influence of air damping on the movement of diaphragm 200 can be significantly reduced, improving the speaker's response speed and sound quality. Further, the depth of cavity 101 is less than 500 micrometers. Further reducing the cavity depth to below 500 micrometers can further reduce air damping, further improving the speaker's performance. Further, the depth of cavity 101 is less than 5 micrometers. Reducing the depth of cavity 101 to below 5 micrometers, this depth of cavity can almost eliminate the influence of air damping on the movement of diaphragm 200, bringing the speaker's performance close to its theoretical limit.
[0053] In one embodiment, the support substrate 100 can be made of metals such as silicon and aluminum, or dielectric materials such as aluminum nitride. Silicon is one of the most commonly used materials in MEMS technology due to its good mechanical properties, thermal stability, and chemical stability, as well as its ease of compatibility with integrated circuit processes. Silicon-based MEMS loudspeakers can be fabricated using standard semiconductor processes, facilitating large-scale production. Aluminum substrates offer better heat dissipation. Dielectric materials such as aluminum nitride are attracting attention in MEMS loudspeakers due to their piezoelectric properties. When these materials are used as the support substrate 100, they not only provide the necessary mechanical support but also directly participate in the sound generation process, improving the loudspeaker's conversion efficiency.
[0054] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.
[0055] The present utility model patent has been described above with reference to the accompanying drawings. Obviously, the implementation of the present utility model patent is not limited to the above-described manner. Any improvements made by adopting the inventive concept and technical solution of the present utility model patent, or the direct application of the inventive concept and technical solution of the present utility model patent to other occasions without modification, are all within the protection scope of the present utility model.
Claims
1. A MEMS loudspeaker with a self-sealing back cavity, characterized in that, The MEMS speaker includes: A supporting base having a cavity formed thereon; A diaphragm, which covers the supporting substrate, has a release hole partially or entirely formed therein, and the release hole communicates with the cavity; When a release hole is opened in part of the diaphragm, the diaphragm without a release hole is sealed and covered on the diaphragm with the release hole, so that the cavity opened on the support substrate and the release hole opened on the diaphragm form a low-pressure sealed chamber. When all the diaphragms have release holes, a sealing layer is sealed on top of the diaphragm so that the cavity on the supporting base and the release holes on the diaphragm form a low-pressure sealed chamber. The low-pressure sealed chamber has a pressure lower than standard atmospheric pressure, and the diaphragm is provided with electrically drivable electrodes and / or functional materials.
2. A MEMS loudspeaker with a self-sealing back cavity according to claim 1, characterized in that, The pressure in the low-pressure sealed chamber is a vacuum.
3. A MEMS loudspeaker with a self-sealing back cavity according to claim 1 or 2, characterized in that, A circuit board is provided on the side of the support substrate away from the diaphragm, and the electrodes on the diaphragm are connected to the circuit board via connecting wires.
4. A MEMS loudspeaker with a self-sealing back cavity according to claim 3, characterized in that, The diaphragm includes a support layer and a piezoelectric layer. The support layer is disposed on the surface of the support substrate and is sealed over the support substrate. The piezoelectric layer is disposed on the support layer.
5. A MEMS loudspeaker with a self-sealing back cavity according to claim 4, characterized in that, Metal conductive layers are formed on both the top and bottom surfaces of the piezoelectric layer, and the two metal conductive layers are respectively connected to the circuit board through the connecting lines.
6. A MEMS loudspeaker with a self-sealing back cavity according to claim 4, characterized in that, The support layer is provided with the release hole.
7. A MEMS loudspeaker with a self-sealing back cavity according to claim 5, characterized in that, The support layer, the piezoelectric layer, and the metal conductive layers on both the top and bottom surfaces of the piezoelectric layer are all provided with the release holes, and the sealing layer is provided on the metal conductive layer on the top surface of the piezoelectric layer.
8. A MEMS loudspeaker with a self-sealing back cavity according to claim 1, 2, 4, 5, 6 or 7, characterized in that, The depth of the cavity is less than 1 mm.
9. A MEMS loudspeaker with a self-sealing back cavity according to claim 8, characterized in that, The cavity has a depth of less than 500 micrometers.
10. A MEMS loudspeaker with a self-sealing back cavity according to claim 9, characterized in that, The cavity has a depth of less than 5 micrometers.