MEMS microphone and preparation method thereof, and electronic device

Abstract

The invention relates to the technical field of microelectronics, and provides an MEMS microphone and a preparation method thereof, and an electronic device, the microphone comprises a substrate, the substrate comprises a first wafer and a first sacrificial layer, the first wafer is provided with a sealed cavity diaphragm, the first sacrificial layer is used for separating the sealed cavity diaphragm from the first wafer, and the substrate comprises a sound transmission hole penetrating through the first wafer and the first sacrificial layer; a second wafer on which a back plate is prepared; wherein the first wafer and the second wafer are bonded in a low-pressure environment, so that the sealed cavity vibrating diaphragm and the back plate form a capacitor. According to the method, the signal-to-noise ratio of the microphone is improved, and the reliability of the MEMS microphone is enhanced.

Description

Technical Field

[0001] The present invention relates to the field of microelectronics technology, and in particular, to a MEMS microphone, a preparation method thereof, and an electronic device. Background Art

[0002] With the rapid development of semiconductor technology, microelectromechanical system (MEMS) technology has become a key technology in the field of sensors. Due to its characteristics such as miniaturization, integration, low power consumption, and high sensitivity, MEMS sensors have been widely used in multiple fields such as automotive electronics, consumer electronics, industrial electronics, and electronic audio and video. Especially in the field of electronic audio and video, MEMS microphones have gradually replaced traditional electret condenser microphones (ECMs) due to their excellent performance and size advantages.

[0003] The working principle of a MEMS microphone is based on the movement of a diaphragm to generate a capacitance change, and the sound signal is converted into an electrical signal by detecting this change. In the design of traditional MEMS microphones, in order to further reduce noise, the SDM (Sealed Dual Membrane) technology has been proposed. The SDM technology directly reduces the density of gas molecules around the diaphragm through a low-pressure sealing technology, thereby reducing the background thermal noise. Although SDM microphones perform excellently in reducing noise, their process difficulty is relatively high, especially in the design of the support pillars connecting the diaphragm. In order to maintain a certain capacitance value of the MEMS microphone, the support pillars need to achieve deep etching and deposition with a high aspect ratio, which easily leads to the formation of voids, reduces the connection strength, and affects the reliability of the device. Summary of the Invention

[0004] The present invention provides a MEMS microphone, a preparation method thereof, and an electronic device, which are used to solve the defect of low reliability of devices in the prior art. By performing hierarchical etching and then completing electrical connection through bonding, the problem of deep etching and deposition with a high aspect ratio is solved, the connection strength is improved, and the reliability of the device is ensured.

[0005] The present invention provides a MEMS microphone, including: a substrate, the substrate includes a first wafer on which a sealed cavity diaphragm is prepared and a first sacrificial layer for spacing the sealed cavity diaphragm from the first wafer, and the substrate includes a sound transmission hole penetrating through the first wafer and the first sacrificial layer; a second wafer, on which a back plate is prepared; wherein, the first wafer and the second wafer are bonded in a low-pressure environment, so that the sealed cavity diaphragm and the back plate form a capacitor.

[0006] According to the MEMS microphone provided by the present invention, the sealed cavity diaphragm includes: a first diaphragm, the first diaphragm is connected to the first sacrificial layer; a second diaphragm, the second diaphragm is mechanically coupled to the first diaphragm through a connecting column, and under the action of the incident sound pressure, the first diaphragm drives the second diaphragm to perform common-mode vibration, and the second diaphragm is in a low-viscosity atmosphere; a second sacrificial layer for spacing the first diaphragm and the second diaphragm.

[0007] According to the MEMS microphone provided by the present invention, the back plate includes: a first back electrode with perforations, the first back electrode is spaced from the second wafer through a third sacrificial layer 108; a second back electrode with perforations, the second back electrode is spaced from the second diaphragm through a fourth sacrificial layer.

[0008] According to the MEMS microphone provided by the present invention, the number of impedance holes on the back plate is less than the number of impedance holes on the back plate in a non-low-pressure environment.

[0009] The present invention also provides a method for manufacturing a MEMS microphone, including: preparing a first wafer, and fabricating a first sacrificial layer on the first wafer; fabricating a sealed cavity diaphragm on the first sacrificial layer; preparing a second wafer, and fabricating a back plate on the second wafer; bonding the first wafer and the second wafer in a low-pressure environment so that the sealed cavity diaphragm and the back plate form a capacitor; fabricating a sound transmission hole in the first wafer and the first sacrificial layer.

[0010] According to the method for manufacturing a MEMS microphone provided by the present invention, the fabricating a sealed cavity diaphragm on the first sacrificial layer includes: fabricating a first diaphragm on the first sacrificial layer, and the material of the first diaphragm has electrical insulation; fabricating a second sacrificial layer on the first diaphragm; performing patterning and etching deposition on the second sacrificial layer to obtain a connecting structure, and the dimensions of the connecting structure in the vertical and horizontal directions meet a preset standard, and the filling material of the connecting structure has a high etching selectivity ratio with the second sacrificial layer and is electrically insulated; performing a planarization process on the first wafer after depositing the filling material of the connecting structure; depositing a second diaphragm, and the material of the second diaphragm has good electrical conductivity; opening holes in the second diaphragm as discharge holes for the products after etching the second sacrificial layer; releasing the second sacrificial layer by dry etching; sealing the second diaphragm in a low-viscosity fluid to form the sealed cavity diaphragm; performing patterning on the surface of the first wafer for the sealed cavity diaphragm and the back plate pads.

[0011] According to the method for manufacturing a MEMS microphone provided by the present invention, the fabricating a first diaphragm on the first sacrificial layer includes: performing patterning on the film in the vertical direction to make the film have a higher compliance coefficient.

[0012] According to the manufacturing method of the MEMS microphone provided by the present invention, the diameter of the bleeding hole is smaller than the thickness of the second diaphragm and has a uniform distribution.

[0013] According to the manufacturing method of the MEMS microphone provided by the present invention, the preparation of the second wafer and the manufacturing of the back plate on the second wafer include: depositing a third sacrificial layer 108 on the second wafer as the cavity above the back plate, where the thickness of the third sacrificial layer 108 is greater than a preset value; depositing back plate material on the third sacrificial layer 108 and performing patterning to etch out the impedance holes of the back plate; depositing a fourth sacrificial layer above the back plate; performing photolithography, etching, and depositing metal electrodes to lead the back electrode to the surface of the second wafer; performing patterning on the surface of the second wafer and completing the release of the perforated back plate through etching.

[0014] The present invention also provides an electronic device including any one of the above-mentioned MEMS microphones.

[0015] The MEMS microphone, its manufacturing method, and the electronic device provided by the present invention respectively manufacture a sealed cavity diaphragm on a first wafer and a back plate on a second wafer, and then bond the first wafer and the second wafer in a low-pressure environment through wafer-level bonding technology, improving the signal-to-noise ratio of the microphone while solving the problem of deep high-aspect-ratio etching and deposition, and enhancing the reliability of the MEMS microphone. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 is a schematic structural diagram of the MEMS microphone provided by the present invention.

[0018] Figure 2 is a schematic flow chart of the manufacturing method of the MEMS microphone provided by the present invention.

[0019] Figures 3 - 17 is a schematic diagram of the manufacturing process of the MEMS microphone provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings in the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts shall fall within the protection scope of the present invention.

[0021] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the art to which the present invention pertains. The "first", "second", and similar terms used in the present invention do not denote any order, quantity, or importance, but are only used to distinguish different components. Similarly, the terms such as "a", "an", or "the" do not denote a quantity limitation, but indicate the existence of at least one. The terms such as "comprising" or "including" mean that the elements or objects appearing before this term cover the elements or objects listed after this term and their equivalents, without excluding other elements or objects. The terms such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect.

[0022] The terms related to the present invention will be briefly explained below.

[0023] The following Figures 1 - 17 describes the MEMS microphone of the present invention, its manufacturing method, and the electronic device.

[0024] Figure 1 is a schematic structural diagram of the MEMS microphone provided by the present invention. As Figure 1 shown, the microphone includes: a substrate, the substrate includes a first wafer 101 on which a sealed cavity diaphragm is fabricated and a first sacrificial layer 102 for spacing the sealed cavity diaphragm from the first wafer 101, and the substrate includes a sound transmission hole penetrating through the first wafer 101 and the first sacrificial layer 102; a second wafer 109, on which a backplate 107 is fabricated; wherein, the first wafer 101 and the second wafer 109 are bonded in a low-pressure environment, such that the sealed cavity diaphragm and the backplate 107 form a capacitor, that is, the transducer body, covering the substrate.

[0025] In this embodiment, the first wafer 101 can be made of common semiconductor materials, such as silicon. The structure of the sealed cavity diaphragm can adopt various designs to adapt to different performance requirements and application scenarios. As an example, one solution is to adopt a double-layer diaphragm design, where the first diaphragm is connected to the sacrificial layer, and the second diaphragm is mechanically coupled to the first diaphragm through connecting posts to form a common-mode vibration structure. At the same time, a low-viscosity fluid is introduced between the two diaphragms to reduce the background noise; another solution is to design it as a single-layer diaphragm, directly forming a capacitor structure with the backplane, and reducing the air damping by forming a sealed cavity under the diaphragm; there is also a solution to integrate multiple micropores on the diaphragm to improve the sound wave transmittance and the sensitivity of the diaphragm; in addition, a composite diaphragm structure can also be adopted, and the stiffness and mass distribution of the diaphragm are optimized through the stacking of different material layers to achieve a wider frequency response and a higher signal-to-noise ratio. These solutions can be selected and optimized according to the specific applications and performance goals of the MEMS microphone to achieve the best acoustic performance.

[0026] In addition, the backplane 107 prepared on the second wafer 109 can have various structural designs to meet different performance requirements and process requirements. As an example, one solution is to design it as a flat structure with a micropore array, and these micropores are used to adjust the acoustic impedance and reduce the air damping, improving the sensitivity and frequency response of the microphone; another solution is to adopt a porous backplane, by forming connected holes or channels inside the backplane to enhance the sound wave capture ability and reduce the noise; there is also a solution to design it as a backplane with ridges or grooves, and these structures can enhance the stiffness of the backplane, while reducing the use of materials and lowering the cost; in addition, the backplane can also be designed as a multi-layer structure, and the acoustic performance and electrical performance are optimized through the stacking of different material layers. For example, a metal layer is integrated on the backplane to improve the conductivity and thermal stability. These different backplane structure solutions can be selected and customized according to the specific application scenarios and performance requirements of the MEMS microphone to achieve the best acoustic conversion efficiency and signal quality.

[0027] For the MEMS microphone provided by the present invention, a sealed cavity diaphragm is prepared on the first wafer 101, and a backplane 107 is prepared on the second wafer 109. Then, through the wafer-level bonding technology, the first wafer 101 and the second wafer 109 are bonded in a low-pressure environment. By sealing the diaphragm in a low-pressure environment, the background thermal noise is reduced, the signal-to-noise ratio of the microphone is improved. At the same time, the problem of high aspect ratio etching and deposition is solved, relatively easy preparation is achieved, and the reliability of the MEMS microphone is enhanced.

[0028] In some alternative implementations, the sealed cavity diaphragm includes: a first diaphragm 103, which is connected to a first sacrificial layer 102; a second diaphragm 105, which is mechanically coupled to the first diaphragm 103 through a connecting post. Under the action of the incident sound pressure, the first diaphragm 103 drives the second diaphragm 105 to perform common-mode vibration, and the second diaphragm 105 is in a low-viscosity atmosphere; a second sacrificial layer 104, which is used to separate the first diaphragm 103 and the second diaphragm 105. The sealed cavity diaphragm is composed of two mechanically coupled thin films up and down. Among them, the bottom diaphragm drives the top diaphragm to perform common-mode vibration under the action of the incident sound pressure. The top diaphragm can be completely in a low-viscosity fluid, which can effectively reduce the background noise and serve as the real movable structure in the variable capacitance structure of the MEMS microphone.

[0029] In this implementation, the first sacrificial layer 102 on the first wafer 101 can be made of silicon oxide material, while the first diaphragm 103 and the second diaphragm 105 can be composed of polysilicon, and the support structure and support posts can be made of silicon nitride oxide to ensure the stability and reliability of the structure; the second sacrificial layer 104 can use silicon glass material to cover the entire sealed cavity diaphragm.

[0030] In some alternative implementations, the backplate 107 includes: a first back electrode with perforations, and the first back electrode is separated from the second wafer 109 by a third sacrificial layer 108; a second back electrode with perforations, and the second back electrode is separated from the second diaphragm 105 by a fourth sacrificial layer 106. The second wafer 109 is made of silicon material, and the backplate 107 on it is also polysilicon and is suspended through the third sacrificial layer 108. This design makes a capacitor structure formed between the backplate and the wafer, and the third sacrificial layer can be removed in subsequent processes to enable the free vibration of the backplate, thereby improving the acoustic performance of the microphone.

[0031] In some alternative implementations, the number of impedance holes on the backplate 107 is less than the number of impedance holes on the backplate 107 in a non-low-pressure environment. Since the backplate 107 is in a low-pressure environment, the number of impedance holes on the backplate 107 can be appropriately reduced, thereby improving the stiffness of the backplate 107 while reducing the process difficulty.

[0032] The preparation method of the MEMS microphone provided by the present invention will be described below. The preparation method of the MEMS microphone described below can be mutually referred to the MEMS microphone described above.

[0033] Figure 2 It is a schematic flowchart of the preparation method of the MEMS microphone provided by the embodiment of the present application, as Figure 2 shown, and specifically includes: Step 201, prepare the first wafer 101 and fabricate the first sacrificial layer 102 on the first wafer 101.

[0034] See Figure 3 , Figure 3 which shows the first wafer 101 prepared. Continuing to refer to Figure 4 , on the first wafer 101, methods such as thermal oxidation or Low Pressure Chemical Vapor Deposition (LPCVD) can be used to fabricate the first sacrificial layer 102 as a separation between the diaphragm and the substrate.

[0035] Step 202, prepare a sealed cavity diaphragm on the first sacrificial layer 102; In this embodiment, to prepare a sealed cavity diaphragm on the first sacrificial layer 102, various methods can be used, including directly depositing diaphragm materials on the first sacrificial layer by LPCVD technology and then performing photolithography and etching to form a structure, using a stacking technique to sequentially deposit different functional layers to construct a composite diaphragm, controlling the material prestress through stress engineering to optimize the vibration characteristics, applying self-aligned etching technology to improve the structure accuracy, using template-assisted deposition to define the diaphragm shape, a multi-step release process to gradually form a cavity structure, and integrating microfluidic technology to integrate fluid channels to dynamically adjust the diaphragm performance. These parallel solutions can be flexibly selected according to performance requirements, cost, and process feasibility to optimize the acoustic characteristics of the MEMS microphone.

[0036] Step 203, prepare the second wafer 109 and fabricate the backplate 107 on the second wafer 109.

[0037] In this embodiment, the backplate material can be directly deposited on the wafer surface by Chemical Vapor Deposition (CVD) or Physical Vapor Deposition (PVD) technology, and then photolithography and etching processes are carried out to form the backplate structure; or Micro-Electro-Mechanical System (MEMS) processing techniques (such as Deep Reactive Ion Etching, DRIE) can be used to directly etch the backplate shape on the wafer; spin coating or inkjet printing techniques can also be used to form a thin layer of the backplate on the wafer, and then the geometric features of the backplate are defined through a patterning process; in addition, a prefabricated backplate structure can be transferred to the wafer through lamination or bonding techniques, or electroplating technology can be used to deposit the backplate material on the wafer. These solutions can be selected according to the required backplate material characteristics, geometry, and production cost to achieve the best effect of fabricating the MEMS microphone backplate.

[0038] Step 204, bond the first wafer 101 and the second wafer 109 in a low-pressure environment so that the sealed cavity diaphragm and the backplate 107 form a capacitor.

[0039] In this embodiment, techniques such as thermal oxidation bonding, anodic bonding, glass fusion bonding, or polymer bonding can be employed. Each technique has its specific temperature, pressure, and environmental requirements to ensure a strong connection between the two wafers and the performance of the capacitor. Alternatively, a bonding method assisted by a temporary adhesive can be used to achieve temporary or permanent connection between the wafers through ultraviolet curing or thermal curing. Micromachining techniques can also be utilized to form specific microstructures on the wafer surface to promote mechanical interlocking between the wafers and enhance the bonding strength. These solutions can be selected according to the required electrical performance, mechanical stability, and production cost.

[0040] Step 205, fabricate a sound transmission hole in the first wafer 101 and the first sacrificial layer 102.

[0041] In this embodiment, methods such as photolithography and etching can be used to form a receiving surface for sound wave incidence on the back surface of the substrate. The sound transmission hole can penetrate the thickness of the substrate, exposing the diaphragm.

[0042] The manufacturing method of the MEMS microphone provided by the present invention respectively fabricates a sealed cavity diaphragm on the first wafer 101 and a backplane 107 on the second wafer 109, and then bonds the first wafer 101 and the second wafer 109 in a low-pressure environment through wafer-level bonding technology, improving the signal-to-noise ratio of the microphone while solving the problem of high aspect ratio etching and deposition in the traditional method, and enhancing the reliability of the MEMS microphone.

[0043] In some alternative implementation manners, Figures 5 to 12 The process of fabricating a sealed cavity diaphragm on the first sacrificial layer 102 is shown, including: fabricating a first diaphragm 103 on the first sacrificial layer 102, and the material of the first diaphragm 103 has electrical insulation; fabricating a second sacrificial layer 104 on the first diaphragm 103; completing patterning and etching deposition on the second sacrificial layer 104 to obtain a connection structure, and the scales of the connection structure in the vertical and horizontal directions meet the preset standards, and the filling material of the connection structure has a high etching selectivity ratio with the second sacrificial layer 104 and is electrically insulated; performing a planarization process on the first wafer 101 after depositing the filling material of the connection structure; depositing a second diaphragm 105, and the material of the second diaphragm 105 has good electrical conductivity; opening holes in the second diaphragm 105 as discharge holes for the products after etching the second sacrificial layer 104; releasing the second sacrificial layer 104 by dry etching; sealing the second diaphragm 105 in a low-viscosity fluid to form a sealed cavity diaphragm; completing patterning of the sealed cavity diaphragm and the pads of the backplane 107 on the surface of the first wafer 101.

[0044] See Figure 5, on the first sacrificial layer 102, the first diaphragm 103 can be prepared by CVD. The optional materials should have significant electrical insulation properties, such as polysilicon, amorphous silicon, silicon nitride, non-metal, organic polymers, etc. The film can have an appearance of a circle, ellipse, rectangle or any other closed structure, and the film thickness can be 0.5 - 1 μm. See Figure 6 , on the first diaphragm 103, the second sacrificial layer 104 can be prepared by methods such as CVD and PVD. The optional materials are, for example, silicon oxide, borophosphosilicate glass, silicon nitride, amorphous carbon, etc. The second sacrificial layer 104 should have a suitable height, such as 1 - 2 μm.

[0045] See Figures 7 - 9 , patterning and etching deposition can be completed on the second sacrificial layer 104. As a connecting structure, the connecting structure can have an arbitrary columnar or pedestal-like three-dimensional structure. In terms of the characteristic length, the connecting structure should have comparable scales in the vertical and horizontal directions to ensure the reliability of etching and filling. The filling material should be selected to have a high etching selectivity ratio with the second sacrificial layer 104 and be electrically insulating. The connecting structure can have a sparse or compact distribution. A planarization process, such as etching, reflow, CMP, etc., is performed on the first wafer 101 after depositing the connecting structure material to ensure the flatness of the wafer device surface.

[0046] See Figure 10 , deposit the second diaphragm 105. The material of the second diaphragm 105 should have good electrical conductivity, such as doped semiconductors, metals, etc. Generally, the film thickness should not be greater than 0.5 μm. Similarly, the second diaphragm 105 can also have an appearance of a circle, ellipse, rectangle or any other closed structure, and the film can be appropriately patterned in the vertical direction, such as wrinkling, segmentation, suspension, etc., to make the film have a higher compliance coefficient.

[0047] See Figure 11 , pattern the second diaphragm 105 and open holes as the discharge holes for the etched products of the second sacrificial layer 104. The second sacrificial layer 104 can be released by dry etching, such as vHF, ashing, etc. See Figure 12 , in a low-viscosity atmosphere, the second diaphragm 105 can be sealed to form a film containing a sealed cavity. Finally, patterning of the diaphragm and the pads of the backplane 107 can be completed on the surface of the first wafer 101.

[0048] In some alternative implementation manners, preparing the first diaphragm 103 on the first sacrificial layer 102 includes: patterning the film in the vertical direction to make the film have a higher compliance coefficient. Appropriate patterning of the film in the vertical direction, such as wrinkling, segmentation, suspension, etc., can make the film have a higher compliance coefficient.

[0049] In some alternative implementations, the diameter of the bleed hole is smaller than the thickness of the second diaphragm 105 and has a uniform distribution. This can ensure that the bleed hole does not penetrate the entire diaphragm during the release process, thereby guaranteeing the integrity and mechanical strength of the diaphragm. At the same time, this also helps to maintain the consistency and uniformity of the diaphragm and avoid local weak points caused by overly large hole diameters.

[0050] In some alternative implementations, Figures 13 to 17 The process of fabricating the backplane 107 on the second wafer 109 is shown, including: depositing a third sacrificial layer 108 on the second wafer 109 as a cavity above the backplane 107, where the thickness of the third sacrificial layer 108 is greater than a preset value; depositing the backplane 107 material on the third sacrificial layer 108 and patterning it to etch out the impedance holes of the backplane 107; depositing a fourth sacrificial layer 106 above the backplane 107; performing photolithography, etching, and depositing metal electrodes to lead the back electrode to the surface of the second wafer 109; patterning the surface of the second wafer 109 and completing the release of the perforated backplane 107 through etching.

[0051] See Figure 13 , the second wafer 109 is prepared. The substrate can be selected from single-crystalline silicon, compound single-crystalline semiconductors, glass, silicon-on-insulator, etc. See Figure 12 , depositing the third sacrificial layer 108 as a cavity above the backplane 107. The third sacrificial layer 108 should have a considerable thickness, such as 5 μm. See Figure 15 , depositing the backplane 107 material, which should have good conductivity, such as doped semiconductors, metals, etc. The thickness of the backplane 107 should not be less than 1 μm to ensure a sufficient stiffness coefficient. See Figure 16 , patterning the backplane 107 to etch out the acoustic impedance holes. The impedance holes can be arranged in a specific array, such as rectangular, arc-shaped, hexagonal, etc. Horizontally, the impedance holes can have a characteristic length of 4 - 10 μm, and the shape of the holes can be circular, elliptical, rectangular, or any other closed structure appearance.

[0052] See Figure 17 , depositing the fourth sacrificial layer 106 above the backplane 107. This sacrificial layer simultaneously defines the capacitance value of the variable capacitance structure in the zero-excitation state. To obtain a higher capacitance value, the thickness of the fourth sacrificial layer 106 should not be greater than 2 μm. Then, perform photolithography, etching, and depositing metal electrodes to lead the back electrode to the surface of the second wafer 109. Perform one patterning on the surface of the second wafer 109, and then complete the release of the perforated backplane 107 through etching. Finally, the wafer with the sealed cavity diaphragm and the backplane 107 can be electrically connected through bonding, such as direct bonding, to complete the fabrication of the overall device.

[0053] On the other hand, the present invention also provides an electronic device, including the MEMS microphone described in the above embodiments.

[0054] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art can understand and implement it without creative effort.

[0055] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on this understanding, the essence of the above technical solution, or the part that contributes to the prior art, can be embodied in the form of a software product. The computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A MEMS microphone, characterized in that: include: A substrate, the substrate comprising a first wafer having a sealed cavity diaphragm and a first sacrificial layer for spacing the sealed cavity diaphragm from the first wafer, the substrate comprising a sound transmission hole penetrating the first wafer and the first sacrificial layer; a second wafer, on which a backplane is prepared; The first wafer and the second wafer are bonded under a low-pressure environment, so that the sealed cavity diaphragm and the back plate form a capacitor.

2. The MEMS microphone according to claim 1, characterized in that: The sealed cavity diaphragm comprises: a first diaphragm, wherein the first diaphragm is connected to the first sacrificial layer; a second diaphragm, wherein the second diaphragm is mechanically coupled to the first diaphragm via a connecting column, the first diaphragm drives the second diaphragm to vibrate in a common mode under the action of incident sound pressure, and the second diaphragm is in a low-viscosity atmosphere; The second sacrificial layer is used to separate the first diaphragm and the second diaphragm.

3. The MEMS microphone according to claim 2, characterized in that: The back plate comprises: a first back electrode with a perforation, wherein the first back electrode is separated from the second wafer by a third sacrificial layer 108; A second back electrode with a perforation is provided, wherein the second back electrode is separated from the second diaphragm by a fourth sacrificial layer.

4. The MEMS microphone according to claim 1, characterized in that: The number of impedance holes on the backplane is less than the number of impedance holes on the backplane in a non-low-voltage environment.

5. A method for preparing a MEMS microphone, characterized in that: include: preparing a first wafer, and forming a first sacrificial layer on the first wafer; preparing a sealed cavity diaphragm on the first sacrificial layer; preparing a second wafer, and preparing a backplane on the second wafer; Bonding the first wafer and the second wafer under a low pressure environment so that the sealed cavity diaphragm and the back plate form a capacitor; Sound transmission holes are made in the first wafer and the first sacrificial layer.

6. The method for preparing a MEMS microphone according to claim 5, characterized in that: The step of preparing a sealed cavity diaphragm on the first sacrificial layer comprises: Preparing a first diaphragm on the first sacrificial layer, wherein the material of the first diaphragm has electrical insulation properties; On the first diaphragm, preparing a second sacrificial layer; Performing patterning and etching deposition on the second sacrificial layer to obtain a connection structure, wherein the dimensions of the connection structure in the vertical and horizontal directions meet preset standards, and the filling material of the connection structure has a high etching selectivity ratio with the second sacrificial layer and is electrically insulated; performing a planarization process on the first wafer after depositing the filling material of the connection structure; Depositing a second diaphragm, wherein the material of the second diaphragm has good electrical conductivity; Opening a hole in the second diaphragm to serve as a discharge hole for the product after etching the second sacrificial layer; releasing the second sacrificial layer by dry etching; In a low-viscosity fluid, sealing the second diaphragm to form the sealed cavity diaphragm; The sealing cavity diaphragm and the backplane pad are patterned on the surface of the first wafer.

7. The method for preparing a MEMS microphone according to claim 6, characterized in that: The step of preparing a first diaphragm on the first sacrificial layer comprises: The film is patterned in the vertical direction to make the film have a higher compliance coefficient.

8. The method for preparing a MEMS microphone according to claim 6, characterized in that: The diameter of the discharge holes is smaller than the thickness of the second diaphragm and has a uniform distribution.

9. The method for preparing a MEMS microphone according to claim 5, characterized in that: The step of preparing a second wafer and preparing a backplane on the second wafer includes: Depositing a third sacrificial layer 108 on the second wafer as a cavity above the back plate, wherein the thickness of the third sacrificial layer 108 is greater than a preset value; Depositing a backplane material on the third sacrificial layer 108, and patterning it to etch out impedance holes of the backplane; depositing a fourth sacrificial layer over the backplate; Photolithography, etching, and deposition of metal electrodes to lead the back electrode to the surface of the second wafer; The surface of the second wafer is patterned, and the release of the perforated backplane is completed by etching.

10. An electronic device, characterized in that: A MEMS microphone comprising any one of claims 1-4.

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