Piezoelectric MEMS loudspeaker preparation method and piezoelectric MEMS loudspeaker

Abstract

The invention discloses a piezoelectric MEMS loudspeaker preparation method and a piezoelectric MEMS loudspeaker, the MEMS loudspeaker comprises a support substrate and a diaphragm, and the support substrate is provided with a cavity; the vibrating diaphragm covers the supporting substrate, a release hole is partially or wholly formed in the vibrating diaphragm, the release hole is communicated with the cavity, and the cavity formed in the supporting substrate and the release hole formed in the vibrating diaphragm form a low-pressure sealed cavity; the low-pressure sealing cavity has the pressure intensity lower than the standard atmospheric pressure, and the vibrating diaphragm is provided with an electrically-driven electrode and / or a functional material. The release hole is formed in the vibrating diaphragm and communicated with the cavity in the supporting substrate, vibration on the vibrating diaphragm can be transmitted into the cavity more rapidly through the release hole, rapid transmission of vibration energy is promoted, the sound output quality and efficiency are further optimized, the vibration transmission process is further accelerated through the low-pressure sealing cavity, and the sound output efficiency is improved. And the energy loss is reduced, so that the MEMS loudspeaker can realize higher sound output quality in a smaller volume.

Description

Technical Field

[0001] The present invention relates to the technical field of MEMS speakers, and more particularly to a method for preparing a piezoelectric MEMS speaker and a piezoelectric MEMS speaker. Background Art

[0002] With the rapid development of microelectronics technology, MEMS technology has been widely used in many fields. Among them, MEMS speakers, as key components for sound conversion and transmission, have shown great potential in miniaturization and integration. MEMS speakers achieve efficient transmission and reception of sound waves through their highly integrated vibrating film structure.

[0003] As a type of MEMS speaker, piezoelectric MEMS speakers use the inverse piezoelectric effect of piezoelectric materials to convert electrical energy into mechanical energy, thereby driving the vibration film to vibrate and generate sound. The core lies in the close integration of piezoelectric materials and vibration films, as well as the precise control of the vibration frequency and amplitude of the vibration film to achieve efficient conversion of sound waves.

[0004] Existing piezoelectric MEMS speakers usually have a larger back cavity to optimize the vibration characteristics of the diaphragm and reduce the impact of air damping on the vibration effect. The main function of the back cavity is to provide a relatively closed space so that the diaphragm can be subjected to a more uniform air pressure distribution when vibrating, thereby improving the emission efficiency and sound quality of the sound waves. However, the size of the back cavity is often proportional to the mass of the speaker diaphragm, and is usually required to reach hundreds of cubic millimeters to ensure that the diaphragm can vibrate freely and stably.

[0005] In contrast, the volume of the MEMS device part is usually smaller. The difference between the volume of the back cavity and the volume of the MEMS device part limits the application scope of piezoelectric MEMS speakers. An overly large back cavity will cause unnecessary reflection and interference of sound waves in the back cavity, thus affecting the transmission efficiency and sound quality of the sound waves. Summary of the invention

[0006] In order to overcome the problem that existing piezoelectric MEMS speakers usually have a larger back cavity to optimize the vibration of the diaphragm, the difference between the volume of the back cavity and the volume of the MEMS device part limits the application scope of the piezoelectric MEMS speakers, and an overly large back cavity will cause unnecessary reflection and interference of sound waves in the back cavity, thereby affecting the transmission efficiency and sound quality of the sound waves. The present invention provides a piezoelectric MEMS speaker preparation method and a piezoelectric MEMS speaker.

[0007] The technical solution of the present invention is as follows: A method for preparing a piezoelectric MEMS speaker, comprising: S1, machining a cavity on a supporting substrate; S2, covering the cavity of the supporting substrate with a filling layer, so that the upper surface of the filling layer is flush with the surface of the supporting substrate located at the periphery of the cavity; S3, depositing a diaphragm on the surface of the supporting substrate and the surface of the filling layer; S4, etching a part or the whole of the diaphragm to form a release hole, the release hole is connected to the cavity, so that the release hole opened on the diaphragm and the cavity opened on the supporting substrate form a low-pressure sealed chamber; S5, connecting the electrodes on the diaphragm and the contacts on the circuit board through connecting wires; S6. Packaging the piezoelectric MEMS speaker.

[0008] According to the present invention of the above scheme, the step of etching the diaphragm part to form the release hole in S4 includes: S411, depositing a supporting layer on the surface of the supporting substrate and the surface of the filling layer; S412, etching the support layer to form a release hole, and removing the filling layer to expose the cavity; S413, depositing a second metal conductive layer material on the surface of the support layer to form a bottom electrode structure, maintaining a vacuum or low-pressure environment during the deposition process, so that the cavity and the release hole are connected to form a low-pressure sealed back cavity; S414, depositing a piezoelectric layer material on the second metal conductive layer to form a piezoelectric layer structure; S415, depositing a first metal conductive layer material on the surface of the piezoelectric layer to form a top electrode structure.

[0009] According to the present invention of the above scheme, the step of etching the entire diaphragm to form a release hole in S4 includes: S421, depositing a supporting layer on the surface of the supporting substrate and the surface of the filling layer; S422, depositing a second metal conductive layer material on the surface of the support layer to form a bottom electrode structure, and performing etching; S423, depositing a piezoelectric layer material on the surface of the second metal conductive layer to form a piezoelectric layer structure, and performing etching; S424, depositing a first metal conductive layer on the surface of the piezoelectric layer to form a top electrode structure, and performing etching; S425, etching the support layer to connect the holes etched on the second metal conductive layer, the piezoelectric layer and the first metal conductive layer to form a connected release hole, removing the filling layer to expose the cavity; S426, depositing a sealing layer, maintaining a vacuum or low-pressure environment during the deposition process, so that the cavity and the release hole are connected to form a low-pressure sealed back cavity.

[0010] A piezoelectric MEMS speaker, comprising: A supporting substrate, wherein a cavity is formed on the supporting substrate; A diaphragm, the diaphragm is covered on the supporting substrate, a release hole is opened partially or entirely on the diaphragm, and the release hole is connected to the cavity; When a part of the diaphragms has a release hole, the diaphragms without the release hole are sealed and covered on the diaphragms with the release hole, so that the cavity on the supporting substrate and the release hole on the diaphragm form a low-pressure sealed chamber; When the entire diaphragm is provided with a release hole, the diaphragm is sealed and covered with a sealing layer, so that the cavity provided on the supporting substrate and the release hole provided on the diaphragm form a low-pressure sealed chamber; The low-pressure sealed chamber has a pressure lower than the standard atmospheric pressure, and the diaphragm is provided with electrically drivable electrodes and / or functional materials.

[0011] According to the present invention of the above scheme, the release hole is arranged in the middle or side of the diaphragm.

[0012] According to the present invention of the above scheme, the pressure of the low-pressure sealed chamber is vacuum.

[0013] According to the above-mentioned solution of the present invention, a circuit board is provided on the side of the supporting base away from the diaphragm, and the electrodes on the diaphragm are connected to the circuit board via connecting wires.

[0014] According to the present invention of the above scheme, the diaphragm includes a supporting layer and a piezoelectric layer, the supporting layer is arranged on the surface of the supporting substrate and sealed and covered on the supporting substrate, and the piezoelectric layer is arranged on the supporting layer.

[0015] According to the above-mentioned solution of the present invention, metal conductive layers are formed on the top and bottom surfaces of the piezoelectric layer, and the top and bottom metal conductive layers are respectively connected to the circuit board through the connecting wires.

[0016] According to the present invention of the above scheme, the release hole is provided on the support layer.

[0017] According to the above scheme of the present invention, the release holes are arranged on the support layer, the piezoelectric layer and the metal conductive layers arranged on the top and bottom surfaces of the piezoelectric layer, and the sealing layer is arranged on the metal conductive layer on the top surface of the piezoelectric layer.

[0018] According to the present invention of the above aspect, the depth of the cavity is less than 1 mm.

[0019] According to the above aspect of the present invention, the depth of the cavity is less than 500 micrometers.

[0020] According to the above aspect of the present invention, the depth of the cavity is less than 5 micrometers.

[0021] According to the present invention of the above aspect, the surface of the piezoelectric layer is covered with an insulating layer.

[0022] According to the present invention of the above scheme, the support substrate is made of silicon material or glass.

[0023] The beneficial effect of the present invention according to the above scheme is that, by opening a release hole on the diaphragm, the release hole is connected to the cavity on the supporting base, and the vibration on the diaphragm can be transmitted to the cavity more quickly through the release hole, thereby promoting the rapid transmission of vibration energy and optimizing the quality and efficiency of sound output. The low-pressure sealed chamber formed by the release hole and the cavity further accelerates the vibration transmission process and reduces energy loss, so that the MEMS speaker can achieve higher sound output quality and lower distortion rate in a smaller volume. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A top view of the planar structure of the present invention; Figure 2 for Figure 1 Side view taken along line AA; Figure 3 for Figure 1 A partial cross-sectional view of the first embodiment taken along the line AA; Figure 4 for Figure 1 A partial cross-sectional view of the second embodiment taken along the line AA; Figure 5 The frequency response curves of the piezoelectric MEMS speaker of the present invention and the existing piezoelectric MEMS speaker; Fig. 6A is a schematic diagram of S1 in the manufacturing method of the present invention; Figure 6B is a schematic diagram of S2 in the manufacturing method of the present invention; Fig. 7A is a schematic diagram of S411 and S412 in the manufacturing method of the present invention; Figure 7B is a schematic diagram of S413 in the manufacturing method of the present invention; Figure 7C is a schematic diagram of S414 in the manufacturing method of the present invention; Fig.7D is a schematic diagram of S415 in the manufacturing method of the present invention; Fig. 8A is a schematic diagram of S421 in the manufacturing method of the present invention; Figure 8B is a schematic diagram of S422 in the manufacturing method of the present invention; Figure 8C is a schematic diagram of S423 and S424 in the manufacturing method of the present invention; Fig.8D is a schematic diagram of S425 in the manufacturing method of the present invention; Fig. 8E It is a schematic diagram of S426 in the manufacturing method of the present invention.

[0025] In the drawings, the reference numerals are as follows: 100, supporting substrate; 101, cavity; 200, diaphragm; 201, release hole; 202, supporting layer; 203, piezoelectric layer; 204, first metal conductive layer; 205, second metal conductive layer; 300, sealing layer; 400, circuit board; 500, connecting wire. DETAILED DESCRIPTION

[0026] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0027] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present invention are intended to cover non-exclusive inclusions. 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 that are not listed, or may optionally include other steps or units that are inherent to these processes, methods, products or devices. Terms such as "disposed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral body; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. The directions or positions indicated by the terms "upper", "lower", "left", "right", "front", "back", "bottom", etc. are based on the directions or positions shown in the drawings, which are only for the convenience of description and cannot be understood as limitations on the present technical solution.

[0028] It should be noted that existing piezoelectric MEMS speakers usually have a larger back cavity to optimize the vibration characteristics of the diaphragm and reduce the impact of air damping on the vibration effect. The main function of the back cavity is to provide a relatively closed space so that the diaphragm can be subjected to a more uniform air pressure distribution when vibrating, thereby improving the emission efficiency and sound quality of the sound waves. However, the size of the back cavity is often proportional to the mass of the speaker diaphragm, and is usually required to reach hundreds of cubic millimeters to ensure that the diaphragm can vibrate freely and stably.

[0029] In contrast, the volume of the MEMS device part is usually smaller. The difference between the volume of the back cavity and the volume of the MEMS device part limits the application scope of piezoelectric MEMS speakers. An overly large back cavity will cause unnecessary reflection and interference of sound waves in the back cavity, thus affecting the transmission efficiency and sound quality of the sound waves.

[0030] like Figure 1 As shown in FIG8 , this embodiment provides a piezoelectric MEMS speaker. By opening a release hole 201 on the diaphragm 200, the release hole 201 is connected to the cavity 101 on the supporting substrate 100. The vibration on the diaphragm 200 can be transmitted to the cavity 101 more quickly through the release hole 201, which promotes the rapid transmission of vibration energy and optimizes the quality and efficiency of sound output. 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, so that the MEMS speaker can achieve higher sound output quality and lower distortion in a smaller volume.

[0031] Specifically, the MEMS speaker includes: a supporting substrate 100 and a diaphragm 200, and a cavity 101 is formed on the supporting substrate 100; The diaphragm 200 is sealed and covered on the supporting base 100. The diaphragm 200 is partially or entirely provided with a release hole 201, which is connected to the cavity 101. The release hole 201 serves 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.

[0032] When a portion of the diaphragm 200 has a release hole 201, the diaphragm 200 without the release hole 201 is sealed and covered on the diaphragm 200 with the release hole 201, so that the cavity 101 opened on the supporting substrate 100 and the release hole 201 opened on the diaphragm 200 form a low-pressure sealed chamber; the diaphragm 200 region without the release hole 201 serves as a sealing layer 300, directly covering the diaphragm 200 with the release hole 201. The release hole 201 and the cavity 101 are enclosed to form a low-pressure sealed chamber, which effectively reduces the air pressure in the chamber and enhances the response speed and vibration amplitude of the diaphragm 200.

[0033] When the entire diaphragm 200 is provided with a release hole 201, the diaphragm 200 is sealed and covered with a sealing layer 300, so that the cavity 101 provided on the supporting substrate 100 and the release hole 201 provided on the diaphragm 200 form a low-pressure sealed chamber; The low-pressure sealed chamber has a pressure lower than the standard atmospheric pressure, which significantly reduces air damping, allowing the diaphragm 200 to vibrate more quickly and freely under the drive of an electrical signal, thereby reducing distortion and improving sound quality. The diaphragm 200 is provided with electrically drivable electrodes and / or functional materials.

[0034] The working principle is as follows: when an electrical signal is applied to the electrode on the diaphragm 200, the diaphragm 200 vibrates under the action of the electric field or magnetic field. Due to the presence of the release hole 201, the vibration energy on the diaphragm 200 can be quickly transferred to the cavity 101 inside the supporting base 100 to form sound waves. At the same time, the low-pressure sealed chamber further accelerates the vibration transmission process and reduces energy loss, so that the speaker can achieve higher sound output quality and lower distortion in a smaller volume.

[0035] Figure 5 The frequency response curves of the MEMS speaker and the traditional speaker in this embodiment are shown in the figure. It can be clearly seen from the figure that the smaller the back cavity of the traditional piezoelectric MEMS speaker is, the higher the resonant frequency is and the lower the sound pressure level is. Compared with the traditional piezoelectric MEMS speaker, the piezoelectric MEMS speaker with a low-pressure sealed chamber has a 5dB higher sound pressure level under the same resonant frequency condition, and does not require an additional back cavity, which reduces the volume of the speaker.

[0036] The release hole 201 is arranged in the middle or side of the diaphragm 200. When the release hole 201 is arranged in the middle of the diaphragm 200, it can ensure that the vibration energy in all directions of the diaphragm 200 can be transmitted to the cavity 101 more evenly. This helps to reduce the loss of energy during the transmission process and improve the efficiency of the speaker. The release hole 201 arranged in the middle helps to produce more uniform and three-dimensional sound waves, so that the speaker can provide more consistent sound output in all directions.

[0037] The release hole 201 is arranged on the side to better utilize the space between the diaphragm 200 and the supporting substrate 100, especially when the shape or size of the diaphragm 200 is limited. This design helps to achieve efficient sound wave output while maintaining the compactness of the speaker. The release hole 201 is arranged on the side to reduce the interference between the vibration of the diaphragm 200 and other structural components, thereby reducing the distortion rate and improving the sound quality.

[0038] In one embodiment, the pressure of the low-pressure sealed chamber is a vacuum or a near-vacuum. In other examples of implementations, 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 may typically be 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 either case, the pressure of the low-pressure sealed chamber may be generally selected to be a typical range in which it may be lower than standard atmospheric pressure, which is used for meteorological conditions that should be reasonably expected and altitude relative to altitude (e.g., up to 9,000 meters above sea level) in which the MEMS microphone may be used.

[0039] In one embodiment, a circuit board 400 is provided on one side of the support substrate 100 away from the diaphragm 200, and the electrodes on the diaphragm 200 are connected to the circuit board 400 via a connecting line 500. The circuit board 400 is responsible for receiving the audio signal and transmitting it to the electrode. When the audio signal passes through the electrode, a changing electric field or magnetic field is generated, thereby driving the diaphragm 200 to vibrate according to the waveform of the audio signal. This vibration then pushes the surrounding air molecules to generate sound waves, which is the sound we hear.

[0040] The diaphragm 200 includes a supporting layer 202 and a piezoelectric layer 203. The supporting layer 202 is deposited on the surface of the supporting substrate 100 and sealed on the cavity 101 of the supporting substrate 100, thereby forming a low-pressure sealed chamber. The piezoelectric layer 203 is deposited on the supporting layer 202. When subjected to an electric field, it deforms to produce sound. In order to improve the conversion efficiency and stability of the piezoelectric layer 203, metal conductive layers are deposited on the top and bottom surfaces of the piezoelectric layer 203 to form an electrode structure. The top and bottom two layers of metal conductive layers are connected to the circuit board 400 through connecting wires 500, respectively, to realize the input and output of audio signals.

[0041] In order to prevent short circuit between the top and bottom metal conductive layers and protect the electrodes and connecting wires 500 from the external environment, an insulating layer is coated on the surface of the piezoelectric layer 203 to ensure the connection and shielding of the top and bottom metal conductive layers on the connecting wires 500.

[0042] A method for preparing a piezoelectric MEMS speaker, comprising: S1, processing a cavity 101 on a supporting substrate 100, wherein the material of the supporting substrate 100 may be, but is not limited to, single crystal silicon or the like; S2, covering the cavity 101 of the support substrate 100 with a filling layer, and making the upper surface of the filling layer substantially flush with the surface of the support substrate 100 located around the cavity 101 by a process such as grinding; S3, depositing a diaphragm on the surface of the supporting substrate and the surface of the filling layer; S4, etching a part or the whole of the diaphragm to form a release hole, the release hole is connected to the cavity, so that the release hole opened on the diaphragm and the cavity opened on the supporting substrate form a low-pressure sealed chamber; S5, connecting the electrodes on the diaphragm and the contacts on the circuit board through connecting wires; S6. Encapsulate the piezoelectric MEMS speaker to protect the internal structure and circuit system from the external environment. Example

[0043] 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, and when a voltage is applied, the piezoelectric layer 203 will deform, thereby generating vibration, and the vibration energy can be quickly transmitted to the cavity 101 inside the support substrate 100 to form a sound wave.

[0044] The specific process is: A cavity 101 is processed on a supporting substrate 100, wherein the material of the supporting substrate 100 may be selected from but is not limited to single crystal silicon, etc.; the cavity 101 of the supporting substrate 100 is covered with a filling layer, and the upper surface of the filling layer is made substantially flush with the surface of the supporting substrate 100 located around the cavity 101 by processes such as grinding; S411, a supporting layer 202 is deposited on the surface of the supporting substrate 100 and the surface of the filling layer; S412, a release hole 201 is formed on the supporting layer 202 by etching, and the filling layer is removed to expose the cavity 101; S413 , deposit the second metal conductive layer 205 material on the surface of the support layer 202 to form a bottom electrode structure, maintain a vacuum or low-pressure environment during the deposition process, so that the cavity 101 and the release hole 201 form a low-pressure sealed back cavity; S414, deposit the piezoelectric layer 203 material on the surface of the second metal conductive layer 205 to form a piezoelectric layer 203 structure; S415, deposit the first metal conductive layer 204 on the surface of the piezoelectric layer 203 to form a top electrode structure; connect the electrodes on the diaphragm 200 and the contacts on the circuit board 400 through the connecting wire 500. Finally, the entire MEMS speaker is packaged to protect the internal structure and circuit system from the external environment. Among them, it is necessary to deposit an insulating layer material (such as silicon dioxide, silicon nitride, etc.) on the surface of the piezoelectric layer 203 and the metal conductive layer to protect the electrodes and the connecting wire 500. Example

[0045] Release holes are provided on the support layer 202, the piezoelectric layer 203, and the metal conductive layers disposed on the top and bottom surfaces of the piezoelectric layer 203, and the sealing layer 300 is disposed on the metal conductive layer on the top surface of the piezoelectric layer 203. When voltage is applied, the piezoelectric layer 203 will deform, thereby generating vibration, and the vibration energy can be directly transmitted to the cavity 101 inside the support substrate 100 through the release hole 201 to form a sound wave.

[0046] The specific process is: A cavity 101 is processed on a supporting substrate 100, wherein the material of the supporting substrate 100 may be selected from but is not limited to single crystal silicon, etc.; the cavity 101 of the supporting substrate 100 is covered with a filling layer, and the upper surface of the filling layer is made substantially flush with the surface of the supporting substrate 100 located around the cavity 101 by processes such as grinding; S421, a supporting layer 202 is deposited on the surface of the supporting substrate 100 and the surface of the filling layer; S422, a second metal conductive layer 205 material is deposited on the surface of the supporting layer 202 to form a bottom electrode structure, and etching is performed; S423, a pressure-sensitive adhesive is deposited on the surface of the second metal conductive layer 205 The piezoelectric layer 203 material is deposited to form the piezoelectric layer 203 structure, and then etched; S424, the first metal conductive layer 204 is deposited on the surface of the piezoelectric layer 203 to form a top electrode structure, and then etched; S425, 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; S426, the sealing layer is deposited, and a vacuum or low-pressure environment is maintained during the deposition process, so that the cavity 101 and the release hole 201 are connected 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 wire 500. Finally, the entire MEMS speaker is packaged to protect the internal structure and circuit system from the external environment. Among them, it is necessary to deposit an insulating layer material (such as silicon dioxide, silicon nitride, etc.) on the surface of the piezoelectric layer 203 and the metal conductive layer to protect the electrodes and the connecting wire 500.

[0047] In one embodiment, the depth of the cavity 101 is less than 1 mm. When the depth of the cavity 101 is set below 1 mm, the effect of air damping on the movement of the diaphragm 200 can be significantly reduced, thereby improving the response speed and sound quality of the speaker. Further, the depth of the cavity 101 is less than 500 microns. Further reducing the depth of the chamber to below 500 microns can further reduce air damping, thereby further improving the performance of the speaker. Further, the depth of the cavity 101 is less than 5 microns. By reducing the depth of the cavity 101 to below 5 microns, a chamber of this depth can almost eliminate the effect of air damping on the movement of the diaphragm 200, bringing the performance of the speaker close to the theoretical limit.

[0048] In one embodiment, the material of the support substrate 100 can be metal such as silicon, aluminum, or dielectric materials such as aluminum nitride. Silicon is one of the most commonly used materials in MEMS technology because it has good mechanical properties, thermal stability and chemical stability, and is easily compatible with integrated circuit processes. MEMS speakers with silicon substrates can be processed through standard semiconductor processes, which is conducive to large-scale production. Aluminum metal substrates have better heat dissipation properties. Dielectric materials such as aluminum nitride have attracted attention in MEMS speakers 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, thereby improving the conversion efficiency of the speaker.

[0049] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

[0050] The above is an exemplary description of the present invention in conjunction with the accompanying drawings. It is obvious that the implementation of the present invention is not limited to the above-mentioned method. As long as various improvements are made by adopting the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for preparing a piezoelectric MEMS speaker, characterized in that: include: S1, machining a cavity on a supporting substrate; S2, covering the cavity of the supporting substrate with a filling layer, so that the upper surface of the filling layer is flush with the surface of the supporting substrate located at the periphery of the cavity; S3, depositing a diaphragm on the surface of the supporting substrate and the surface of the filling layer; S4, etching a part or the whole of the diaphragm to form a release hole, the release hole is connected to the cavity, so that the release hole opened on the diaphragm and the cavity opened on the supporting substrate form a low-pressure sealed chamber; S5, connecting the electrodes on the diaphragm and the contacts on the circuit board through connecting wires; S6. Packaging the piezoelectric MEMS speaker.

2. The method for preparing a piezoelectric MEMS speaker according to claim 1, characterized in that: in, The step of etching the diaphragm portion to form a release hole in S4 includes: S411, depositing a supporting layer on the surface of the supporting substrate and the surface of the filling layer; S412, etching the support layer to form a release hole, and removing the filling layer to expose the cavity; S413, depositing a second metal conductive layer material on the surface of the support layer to form a bottom electrode structure, maintaining a vacuum or low-pressure environment during the deposition process, so that the cavity and the release hole are connected to form a low-pressure sealed back cavity; S414, depositing a piezoelectric layer material on the second metal conductive layer to form a piezoelectric layer structure; S415, depositing a first metal conductive layer material on the surface of the piezoelectric layer to form a top electrode structure.

3. The method for preparing a piezoelectric MEMS speaker according to claim 1, characterized in that: in, The step of etching the entire diaphragm to form a release hole in S4 includes: S421, depositing a supporting layer on the surface of the supporting substrate and the surface of the filling layer; S422, depositing a second metal conductive layer material on the surface of the support layer to form a bottom electrode structure, and performing etching; S423, depositing a piezoelectric layer material on the surface of the second metal conductive layer to form a piezoelectric layer structure, and performing etching; S424, depositing a first metal conductive layer on the surface of the piezoelectric layer to form a top electrode structure, and performing etching; S425, etching the support layer to connect the holes etched on the second metal conductive layer, the piezoelectric layer and the first metal conductive layer to form a connected release hole, removing the filling layer to expose the cavity; S426, depositing a sealing layer, maintaining a vacuum or low-pressure environment during the deposition process, so that the cavity and the release hole are connected to form a low-pressure sealed back cavity.

4. A piezoelectric MEMS speaker, characterized in that: The piezoelectric MEMS speaker prepared by the piezoelectric MEMS speaker preparation method according to any one of claims 1 to 3 comprises: A supporting substrate, wherein a cavity is formed on the supporting substrate; A diaphragm, the diaphragm is covered on the supporting substrate, a release hole is opened partially or entirely on the diaphragm, and the release hole is connected to the cavity; When a part of the diaphragms has a release hole, the diaphragms without the release hole are sealed and covered on the diaphragms with the release hole, so that the cavity on the supporting substrate and the release hole on the diaphragm form a low-pressure sealed chamber; When the entire diaphragm is provided with a release hole, the diaphragm is sealed and covered with a sealing layer, so that the cavity provided on the supporting substrate and the release hole provided on the diaphragm form a low-pressure sealed chamber; The low-pressure sealed chamber has a pressure lower than the standard atmospheric pressure, and the diaphragm is provided with electrically drivable electrodes and / or functional materials.

5. The piezoelectric MEMS speaker according to claim 4, characterized in that: The release hole is arranged in the middle or side of the diaphragm.

6. The piezoelectric MEMS speaker according to claim 5, characterized in that: A circuit board is provided on a side of the support substrate away from the diaphragm, and the electrodes on the diaphragm are connected to the circuit board via connecting wires.

7. The piezoelectric MEMS speaker according to claim 6, characterized in that: The diaphragm comprises a supporting layer and a piezoelectric layer. The supporting layer is arranged on the surface of the supporting substrate and is sealed and covered on the supporting substrate. The piezoelectric layer is arranged on the supporting layer.

8. The piezoelectric MEMS speaker according to claim 7, characterized in that: Metal conductive layers are formed on the top and bottom surfaces of the piezoelectric layer, and the top and bottom metal conductive layers are respectively connected to the circuit board through the connecting wires.

9. The piezoelectric MEMS speaker according to claim 7, characterized in that: The release hole is provided on the supporting layer.

10. The piezoelectric MEMS speaker according to claim 8, characterized in that: The support layer, the piezoelectric layer and the metal conductive layers arranged on the top and bottom surfaces of the piezoelectric layer are all provided with the release holes, and the sealing layer is arranged on the metal conductive layer on the top surface of the piezoelectric layer.

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