MEMS microphone and manufacturing method thereof

Abstract

The invention discloses an MEMS microphone and a manufacturing method thereof, the MEMS microphone comprises at least one back plate and at least one vibrating diaphragm, a cavity is formed between the at least one back plate and the at least one vibrating diaphragm, the thickness of the middle area of the at least one back plate is smaller than that of the edge area, and the thickness of the cavity is smaller than that of the edge area of the at least one back plate. The distance between the middle area of the at least one back plate and the at least one vibrating diaphragm is greater than the distance between the edge area of the at least one back plate and the at least one vibrating diaphragm. The thickness of the middle area of the back plate is smaller than that of the edge area, so that the distance from the middle area of the back plate to the vibrating diaphragm is larger than that from the edge area of the back plate to the vibrating diaphragm, collision between the vibrating diaphragm and the back plate in the moving process is avoided under the condition that the size of a device is not changed, the stability of the MEMS microphone is enhanced, and the reliability of the MEMS microphone is improved. And the effective area of the back plate is further increased by increasing the distance between the back plate and the vibrating diaphragm, so that the capacitance is increased, and the sensitivity of the MEMS microphone is improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and more particularly to a MEMS microphone and a manufacturing method thereof. Background Art

[0002] Micro-Electro-Mechanical System (MEMS) technology is a high-tech that has developed rapidly in recent years. Micro sensors and actuators fabricated using MEMS technology have been widely applied in military electronics, mobile electronics, medical electronics, automotive electronics, and industrial electronics due to their excellent performance such as miniaturization, low power consumption, high reliability, high sensitivity, easy integration, as well as the characteristics of enhancing system function density, information density, and interconnection density. With the advent of the era of the Internet of Everything, the Internet of Things and intelligent devices have developed rapidly, and sensors, as key devices for sensing and collecting external environmental information, have become even more important.

[0003] A MEMS microphone is an acoustic sensor that converts sound pressure waves into analog signals, including a MEMS sensor and an Application Specific Integrated Circuit (ASIC). The two can be electrically connected together and disposed in a single package. The MEMS sensor is a variable capacitor with a fixed backplate and a movable diaphragm. When sound waves are applied to the MEMS sensor, the diaphragm can move in response to the sound pressure waves, thereby changing the distance between the backplate and the diaphragm, and further changing the capacitance of the variable capacitor. The capacitance change is determined according to the sound wave parameters, and this capacitance is converted into an analog signal and input into the ASIC for further analysis and processing. However, during the movement of the diaphragm, it may touch the backplate and cause adhesion, resulting in device damage. Summary of the Invention

[0004] A series of simplified concepts are introduced in the Summary of the Invention section, which will be further elaborated in the Detailed Description section. The Summary of the Invention section of the present invention does not mean to attempt to define the key features and essential technical features of the claimed technical solution, nor does it mean to attempt to determine the protection scope of the claimed technical solution.

[0005] The present invention provides a MEMS microphone, including at least one backplate and at least one diaphragm. A cavity is formed between the at least one backplate and the at least one diaphragm. The thickness of the middle region of the at least one backplate is less than that of the edge region, so that the distance from the middle region of the at least one backplate to the at least one diaphragm is greater than the distance from the edge region of the at least one backplate to the at least one diaphragm.

[0006] Exemplarily, the at least one backplate includes a first surface and a second surface which are oppositely arranged, wherein the first surface is close to the at least one diaphragm, and the first surface of the at least one backplate is in an arc shape or a stepped shape that is recessed inward.

[0007] Exemplarily, the at least one backplate includes a first surface and a second surface which are oppositely arranged, and both the first surface and the second surface of the at least one backplate are in an arc shape or a stepped shape that is recessed inward.

[0008] Exemplarily, a plurality of sound holes are formed in the at least one backplate.

[0009] Exemplarily, the MEMS microphone further includes a support structure, two ends of the at least one backplate are connected to the support structure, and two ends of the at least one diaphragm are connected to the support structure through an elastic device.

[0010] Exemplarily, a reinforcing layer is further formed on the surface of the diaphragm to enhance the rigidity of the diaphragm.

[0011] Exemplarily, the MEMS microphone includes one or more of a single-backplate single-diaphragm structure, a double-backplate single-diaphragm structure, and a triple-backplate double-diaphragm structure.

[0012] The present invention further provides a manufacturing method of a MEMS microphone, including:

[0013] Providing a first substrate, forming a first groove in the first substrate, and forming a diaphragm in the first groove;

[0014] Providing a second substrate, forming a second groove in the second substrate, wherein the depth of the middle region of the second groove is greater than that of the edge region;

[0015] Bonding the first substrate and the second substrate so that the first groove and the second groove together form a cavity;

[0016] Etching a region of the second substrate corresponding to the cavity to form a backplate having a plurality of sound holes;

[0017] Etching a region of the first substrate corresponding to the cavity to expose the diaphragm.

[0018] Exemplarily, forming the second groove in the second substrate includes:

[0019] Forming a dielectric layer on the surface of the second substrate;

[0020] Forming an opening region in the dielectric layer to expose the surface of the second substrate;

[0021] A photoresist layer is formed within the opening region, and the thickness of the middle region of the photoresist layer is less than that of the edge region;

[0022] The photoresist layer and the second substrate are etched to form a second groove within the opening region, and the depth of the middle region of the second groove is greater than that of the edge region.

[0023] Exemplarily, the method further includes the step of forming a third groove in the second substrate, the depth of the middle region of the third groove being greater than that of the edge region, and the second groove and the third groove are respectively located on the relatively arranged first surface and second surface of the second substrate.

[0024] According to the MEMS microphone and its manufacturing method provided by the present invention, by making the thickness of the middle region of the back plate less than that of the edge region, the distance from the middle region of the back plate to the diaphragm is greater than the distance from the edge region of the back plate to the diaphragm. Without changing the size of the device, it avoids the collision between the diaphragm and the back plate during the movement of the diaphragm, enhances the stability of the MEMS microphone, and further improves the effective area of the back plate by increasing the distance between the back plate and the diaphragm, thereby increasing the capacitance and improving the sensitivity of the MEMS microphone. Description of the Drawings

[0025] The following drawings of the present invention are used as a part of the present invention to understand the present invention. The embodiments of the present invention shown in the drawings and their descriptions are used to explain the principles of the present invention.

[0026] In the drawings:

[0027] Figure 1 is a flowchart of a manufacturing method of a MEMS microphone structure according to an embodiment of the present invention;

[0028] Figures 2A-2J is a cross-sectional schematic diagram of the structure obtained by sequentially implementing the manufacturing method of a single-backplate single-diaphragm MEMS microphone structure according to an embodiment of the present invention;

[0029] Figure 2J is a schematic diagram of a single-backplate single-diaphragm structure of a MEMS microphone according to an embodiment of the present invention;

[0030] Figure 3 is a schematic diagram of a double-backplate single-diaphragm structure of a MEMS microphone according to an embodiment of the present invention;

[0031] Figure 4 is a schematic diagram of a triple-backplate double-diaphragm structure of a MEMS microphone according to an embodiment of the present invention. Detailed Embodiments

[0032] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that the present invention may be practiced without one or more of these specific details. In other instances, well-known features have not been described in order to avoid obscuring the invention.

[0033] It should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. On the contrary, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the dimensions and relative dimensions of layers and regions may be exaggerated for clarity. Like reference numerals throughout the figures denote like elements.

[0034] It should be understood that when an element or layer is referred to as being "on," "adjacent to," "connected to," or "coupled to" another element or layer, it can be directly on, adjacent to, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers, and / or sections, these elements, components, regions, layers, and / or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or section from another element, component, region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of the present invention.

[0035] Spatial relationship terms such as "below," "beneath," "lower," "underneath," "above," "upper," etc. are used herein for convenience in describing the relationship of one element or feature to another element or feature shown in the figures. It should be understood that, in addition to the orientation shown in the figures, spatial relationship terms are intended to encompass different orientations of the device in use and operation. For example, if the device in the figures is flipped over, then an element or feature described as "below" or "beneath" or "under" another element or feature will be oriented "above" the other element or feature. Thus, the exemplary terms "below" and "beneath" can include both an upper and a lower orientation. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatial descriptors used herein are to be interpreted accordingly.

[0036] The purpose of the terms used herein is only to describe specific embodiments and is not a limitation of the present invention. As used herein, the singular forms "a", "an" and "the" are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms "comprising" and / or "including", when used in this specification, specify the presence of the stated features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups. As used herein, the term "and / or" includes any and all combinations of the associated listed items.

[0037] To fully understand the present invention, detailed steps and detailed structures will be presented in the following description to illustrate the technical solutions proposed by the present invention. The preferred embodiments of the present invention are described in detail below. However, in addition to these detailed descriptions, the present invention may have other embodiments.

[0038] The present invention provides a MEMS microphone and a manufacturing method thereof, as Figure 1 shown, including the following steps:

[0039] Step S110: Provide a first substrate, form a first groove in the first substrate, and form a diaphragm in the first groove;

[0040] Step S120: Provide a second substrate, form a second groove in the second substrate, and the depth of the middle region of the second groove is greater than the depth of the edge region;

[0041] Step S130: Bond the first substrate and the second substrate so that the first groove and the second groove together form a cavity;

[0042] Step S140: Etch the region of the second substrate corresponding to the cavity to form a back plate having a plurality of sound holes;

[0043] Step S150: Etch the region of the first substrate corresponding to the cavity to expose the diaphragm.

[0044] Next, with reference to Figures 2A to 2J a detailed description will be given of the manufacturing method of the MEMS microphone structure of the present invention, where Figures 2A to 2J is a schematic cross-sectional view of the structure obtained by sequentially implementing the manufacturing method of the MEMS microphone structure according to an embodiment of the present invention.

[0045] First, perform step S110, as Figures 2A-2C shown, provide a first substrate 210, form a first groove 211 in the first substrate 210, and form a diaphragm 230 in the first groove.

[0046] In one embodiment, asFigure 2A As shown, a first substrate 210 is provided. The first substrate 210 can be any suitable semiconductor substrate, such as a silicon substrate, which can also be at least one of the materials mentioned below: Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP or other III / V compound semiconductors, and also includes multilayer structures composed of these semiconductor materials, etc., or is a silicon-on-insulator (SOI) substrate, silicon-on-insulator stacked silicon (SSOI), silicon-on-insulator stacked germanium silicide (S-SiGeOI), germanium silicide-on-insulator (SiGeOI), and germanium-on-insulator (GeOI), or can also be a double-sided polished wafer (DSP), and can also be Al 2 O 3 and other sapphire substrates, ceramic substrates, quartz or glass substrates, etc. Specifically, the first substrate 210 can be an N-type silicon substrate.

[0047] In one embodiment, as Figure 2B shown, a first groove 211 is formed in the first substrate 210 by a photolithography process. Specifically, a patterned photoresist layer (not shown) with a first groove pattern is formed on the first substrate 210. The photoresist can be formed by a spin coating process, and then the patterned photoresist layer is formed through processes such as exposure, development, and cleaning. Then, the first substrate 210 is etched using the patterned photoresist layer as a mask, thereby forming the first groove 211 in the first substrate 210. The method for etching the first substrate 210 can adopt any existing technology well-known to those skilled in the art, preferably dry etching, and dry etching includes but is not limited to reactive ion etching (RIE), ion beam etching, plasma etching, laser ablation, or any combination of these methods.

[0048] It should be noted that the thickness of the photoresist layer used as an etching mask formed on the first substrate is uniform, and the thickness of the middle region is the same as that of the edge region. Therefore, the depth of the middle region of the formed first groove 211 is the same as that of the edge region.

[0049] In one embodiment, as Figure 2B shown, before forming the diaphragm 230 in the first groove 211, it further includes the step of forming a first dielectric layer 212 on the first substrate 210. The first dielectric layer 212 includes but is not limited to a silicon oxide layer. The formation method of the first dielectric layer 212 can be to generate silicon oxide on the surfaces of the first substrate 210 and the first groove 211 by thermal oxidation, or can also be to form a silicon oxide layer covering the surface of the first substrate 210, the bottom, and the sidewalls of the first groove 211 by chemical vapor deposition (CVD) methods such as low-pressure chemical vapor deposition (LPCVD), plasma-enhanced chemical vapor deposition (PECVD), etc.

[0050] In one embodiment, as Figure 2C shown, a diaphragm 230 is formed in the first groove 211. The diaphragm 230 includes, but is not limited to, a polysilicon layer or a doped polysilicon layer. The diaphragm 230 is formed at the bottom of the first groove 211. Any existing techniques well-known to those skilled in the art can be used for the conventional semiconductor process method of forming the diaphragm 230. Preferably, chemical vapor deposition (CVD) methods such as low-temperature chemical vapor deposition (LTCVD), low-pressure chemical vapor deposition (LPCVD), metalorganic chemical vapor deposition (MOCVD), rapid thermal chemical vapor deposition (RTCVD), and plasma-enhanced chemical vapor deposition (PECVD) can be used.

[0051] In one embodiment, in order to enhance the rigidity of the diaphragm 230, a reinforcing layer (not shown) can also be formed on one or both sides of the diaphragm 230 (i.e., the upper surface and / or the lower surface). The reinforcing layer includes, but is not limited to, a silicon carbide layer or a silicon nitride layer. Any existing techniques well-known to those skilled in the art can be used for the formation method of the reinforcing layer, which will not be elaborated here.

[0052] In one embodiment, both ends of the diaphragm 230 are directly connected to the sidewalls of the first groove 211, or both ends of the diaphragm 230 are connected to the sidewalls of the first groove 211 through an elastic device. The elastic device includes, but is not limited to, a spring. When both ends of the diaphragm 230 are connected to the sidewalls of the first groove 211 through an elastic device, the displacement of the diaphragm of the formed MEMS microphone during vibration will further increase, the capacitance change amount will increase, and more signals can be transmitted within a unit vibration time.

[0053] Next, step S120 is executed. As Figures 2D-2G shown, a second substrate 220 is provided, and a second groove 221 is formed in the second substrate 220. The depth of the middle region of the second groove 221 is greater than the depth of the edge region.

[0054] In one embodiment, as Figure 2DAs shown, a second substrate 220 is provided. The second substrate 220 can be any suitable semiconductor substrate, such as a silicon substrate, which can also be at least one of the materials mentioned below: Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, or other III / V compound semiconductors, and also includes multilayer structures composed of these semiconductor materials, etc., or is a silicon-on-insulator (SOI) substrate, silicon-on-insulator stacked (SSOI), silicon-germanium-on-insulator stacked (S-SiGeOI), silicon-germanium-on-insulator (SiGeOI), and germanium-on-insulator (GeOI), or can also be a double-sided polished wafer (DSP), or can be an aluminum 2 O 3 and other sapphire substrates, ceramic substrates, quartz or glass substrates, etc. Specifically, the second substrate 220 can be an N-type silicon substrate.

[0055] Exemplarily, forming the second groove 221 in the second substrate 220 includes: forming a second dielectric layer 222 on the surface of the second substrate 220; forming an opening region in the second dielectric layer 222 to expose the surface of the second substrate 220; forming a photoresist layer in the opening region, where the thickness of the middle region of the photoresist layer is less than that of the edge region; etching the photoresist layer and the second substrate to form a second groove in the opening region, where the depth of the middle region of the second groove is greater than that of the edge region.

[0056] In one embodiment, as Figure 2D shown, a second dielectric layer 222 is formed on the second substrate 220, and an opening region is formed in the second dielectric layer 222 to expose the surface of the second substrate 220. The second dielectric layer 222 includes, but is not limited to, a silicon oxide layer. The formation method of the second dielectric layer 222 can adopt any existing technology well-known to those skilled in the art, preferably chemical vapor deposition (CVD), such as low-temperature chemical vapor deposition (LTCVD), low-pressure chemical vapor deposition (LPCVD), metalorganic chemical vapor deposition (MOCVD), rapid thermal chemical vapor deposition (RTCVD), plasma-enhanced chemical vapor deposition (PECVD). Then, a photolithography process is used to form an opening region in the second dielectric layer 222 that exposes the surface of the second substrate 220.

[0057] In one embodiment, a photolithography process is used to form the second groove 221 in the second substrate 220. Specifically, a photoresist layer 223 is formed in the opening region of the second dielectric layer 222, and the thickness of the middle region of the photoresist layer 223 is less than that of the edge region, as Figure 2EAs shown. The surface of the formed photoresist 223 can be arc-shaped or stepped, and the present application places no restrictions thereon. Then, using the second dielectric layer 222 and the photoresist 223 as masks, the second substrate 220 is etched. Any existing techniques well-known to those skilled in the art can be used to etch the second substrate 220, and dry etching is preferably used. Dry etching includes, but is not limited to, reactive ion etching (RIE), ion beam etching, plasma etching, laser ablation, or any combination of these methods, thereby forming a second groove 221 in the second substrate 220. Since the thickness of the middle region of the photoresist layer 223 is less than that of the edge region, the depth of the middle region of the formed second groove 221 is greater than that of the edge region, as Figure 2F shown.

[0058] In one embodiment, the surface of the formed second groove 221 is arc-shaped or stepped. When the surface of the second groove 221 is arc-shaped, the depth of the second groove 221 changes linearly from the middle region to the edge region. When the surface of the second groove 221 is stepped, the depth of the second groove 221 changes non-linearly from the middle region to the edge region.

[0059] Exemplarily, a third groove is formed in the second substrate. The depth of the middle region of the third groove is greater than that of the edge region. The second groove and the third groove are respectively located on the relatively arranged first surface and the second surface of the second substrate.

[0060] In one embodiment, as Figure 2G shown, the second substrate 220 includes a relatively arranged first surface and a second surface. When the first surface is used to form the above-mentioned second groove, a third groove can be formed on the second surface. The formation method of the third groove is the same as that of the second groove, and will not be elaborated here.

[0061] The third groove can be formed after the second groove is formed, or can be formed synchronously with the second groove.

[0062] Next, step S130 is executed. As Figure 2H shown, the first substrate 210 and the second substrate 220 are bonded together so that the first groove 211 and the second groove 221 jointly form a cavity 240.

[0063] In one embodiment, before bonding the first substrate 210 and the second substrate 220, it further includes a step of performing chemical mechanical polishing (CMP) on the surfaces of the first dielectric layer 212 and the second dielectric layer 222 so that the surfaces of the first dielectric layer 212 and the second dielectric layer 222 meet the bonding requirements. By directly bonding the fronts of the first dielectric layer 212 and the second dielectric layer 222, the bonding of the first substrate 210 and the second substrate 220 is achieved.

[0064] Next, perform step S140. As Figure 2I shown, etch the area of the second substrate 220 corresponding to the cavity 240 to form a backplate 250 having a plurality of sound holes.

[0065] In one embodiment, the second substrate 220 is thinned by processes such as etching or CMP so that the thickness of the second substrate 220 reaches a preset thickness, such as 1 μm to 5 μm. Then, a photolithography process is performed on the area of the second substrate 220 corresponding to the cavity 240 to form a plurality of through holes, thereby forming a backplate 250 having a plurality of sound holes in the second substrate 220. Any existing technology well-known to those skilled in the art can be used to form the through holes, preferably dry etching, and dry etching includes but is not limited to reactive ion etching (RIE), ion beam etching, plasma etching, laser ablation, or any combination of these methods.

[0066] Next, perform step S150. As Figure 2J shown, etch the area of the first substrate 210 corresponding to the cavity to expose the diaphragm 230.

[0067] In one embodiment, any existing technology well-known to those skilled in the art can be used to etch the first substrate 210. Preferably, deep reactive ion etching (DRIE) is used to etch the back surface of the first substrate 210 and the first dielectric layer 211 between the first substrate 210 and the diaphragm 230 as a sacrificial layer to form a back opening and expose the diaphragm 230.

[0068] Thus, the introduction of the key steps of the MEMS microphone of the present invention is completed. For the complete device fabrication, multiple other process steps may be required, which will not be elaborated one by one here.

[0069] It is worth mentioning that the order of the above steps is only an example. On the premise of no conflict, the order of the above steps can also be swapped or carried out alternately, etc.

[0070] The present invention provides a MEMS microphone. As Figure 2J shown, it includes at least one backplate 250 and at least one diaphragm 230. A cavity 240 is formed between the at least one backplate 250 and the at least one diaphragm 230. The thickness of the middle region of the at least one backplate 250 is less than the thickness of the edge region, so that the distance from the middle region of the at least one backplate 250 to the at least one diaphragm 230 is greater than the distance from the edge region of the at least one backplate 250 to the at least one diaphragm.

[0071] In one embodiment, the at least one backplate 250 includes, but is not limited to, a single-crystalline silicon layer, a polycrystalline silicon layer, or a doped polycrystalline silicon layer. A plurality of through-holes serving as sound holes are formed in the backplate 250. The diaphragm 230 includes, but is not limited to, a polycrystalline silicon layer or a doped polycrystalline silicon layer. A reinforcing layer is further formed on the surface of the diaphragm to enhance the rigidity of the diaphragm. The reinforcing layer includes, but is not limited to, a silicon carbide layer or a silicon nitride layer. The at least one backplate 250 serves as a fixed electrode plate, and the at least one diaphragm serves as a movable electrode plate.

[0072] In one embodiment, the MEMS microphone further includes a support structure. The support structure encloses with the backplate 250 and the diaphragm 230 to form the cavity 240. Both ends of the at least one backplate 250 are connected to the support structure, and both ends of the at least one diaphragm 230 are connected to the support structure through an elastic device. The elastic device includes, but is not limited to, a spring. When the diaphragm 230 is connected to the support structure through the elastic device, the displacement of the diaphragm 230 of the MEMS microphone during vibration will further increase, the capacitance change amount increases, and more signals can be transmitted within a unit vibration time.

[0073] In one embodiment, the at least one backplate 250 includes a first surface and a second surface that are oppositely arranged, wherein the first surface is close to the at least one diaphragm 230, and the first surface of the at least one backplate 250 is in an inwardly concave arc shape or a stepped shape. When the first surface of the backplate 250 is in an arc shape, the thickness of the backplate 250 changes linearly from the thickness in the middle region to the thickness in the edge region. When the first surface of the backplate 250 is in a stepped shape, the thickness of the backplate 250 changes non-linearly from the thickness in the middle region to the thickness in the edge region.

[0074] In one embodiment, the at least one backplate 250 includes a first surface and a second surface that are oppositely arranged, and both the first surface and the second surface of the at least one backplate are in an inwardly concave arc shape or a stepped shape.

[0075] Exemplarily, the MEMS microphone includes one or more of a single backplate single diaphragm structure, a double backplate single diaphragm structure, and a triple backplate double diaphragm structure.

[0076] In one embodiment, the single backplate single diaphragm structure of the MEMS microphone is as Figure 2J shown.

[0077] In one embodiment, Figure 3The double-backplate single-diaphragm structure of the MEMS microphone is shown. Among them, a first backplate is formed above the diaphragm, a second backplate is formed below the diaphragm, a first cavity is formed between the diaphragm and the first backplate, and a second cavity is formed between the diaphragm and the second backplate. The thickness of the middle region of the first backplate and the second backplate is less than that of the edge region. The surface of the first backplate close to the diaphragm is in an inwardly concave arc shape or stepped shape, and the distance from the middle region of the first backplate to the diaphragm is greater than the distance from the edge region of the first backplate to the diaphragm. The surface of the second backplate close to the diaphragm is in an inwardly concave arc shape or stepped shape, and the distance from the middle region of the second backplate to the diaphragm is greater than the distance from the edge region of the second backplate to the diaphragm.

[0078] In one embodiment, Figure 3 The formation method of the double-backplate single-diaphragm structure of the MEMS microphone shown can be carried out after forming Figure 2J the single-backplate single-diaphragm structure shown, and repeating the process of bonding the Figure 2F backplate shown to the first side of the diaphragm introduced in steps S130 to S150, and bonding the Figure 2F backplate shown to the second side of the diaphragm, so as to obtain the Figure 3 double-backplate single-diaphragm structure of the MEMS microphone shown. The specific process will not be elaborated here.

[0079] Compared with Figure 2J the single-backplate single-diaphragm structure shown, Figure 3 the double-backplate single-diaphragm structure shown is equivalent to adding a capacitor. When the diaphragm vibrates up and down, in theory, two current signals with equal magnitudes and opposite directions can be generated for differential output, thereby greatly improving the sensitivity and signal-to-noise ratio of the MEMS microphone.

[0080] In one embodiment, Figure 4The three-backplate double-diaphragm structure of the MEMS microphone is shown, including a first backplate, a first diaphragm, a second backplate, a second diaphragm, and a third backplate that are sequentially arranged at intervals from bottom to top. Among them, a first cavity is formed between the first backplate and the first diaphragm, a second cavity is formed between the first diaphragm and the second backplate, a third cavity is formed between the second backplate and the second diaphragm, and a fourth cavity is formed between the second diaphragm and the third backplate. The thickness of the middle regions of the first backplate, the second backplate, and the third backplate is less than the thickness of the edge regions. The surface of the first backplate close to the first diaphragm is in an inwardly concave arc shape or stepped shape, and the distance from the middle region of the first backplate to the first diaphragm is greater than the distance from the edge region of the first backplate to the diaphragm. The surfaces of the second backplate close to the first diaphragm and the second diaphragm are both in an inwardly concave arc shape or stepped shape, and the distances from the middle region of the second backplate to the first diaphragm and the second diaphragm are both greater than the distances from the edge region of the first backplate to the first diaphragm and the second diaphragm. The surface of the third backplate close to the second diaphragm is in an inwardly concave arc shape or stepped shape, and the distance from the middle region of the third backplate to the second diaphragm is greater than the distance from the edge region of the third backplate to the second diaphragm.

[0081] In one embodiment, Figure 4 The method for forming the three-backplate double-diaphragm structure of the MEMS microphone shown can be carried out after forming Figure 2J the single-backplate single-diaphragm structure shown, and then bonding two Figure 2J single-backplate single-diaphragm structures shown to both sides of the Figure 2G backplate shown, thereby manufacturing the Figure 4 three-backplate double-diaphragm structure of the MEMS microphone shown. The specific process will not be elaborated here.

[0082] Compared with Figure 3 the double-backplate single-diaphragm structure shown, Figure 4 the three-backplate double-diaphragm structure shown includes four capacitors. The more capacitors there are, the stronger the output signal. Although theoretically, higher and better MEMS microphone performance can be obtained by continuously stacking backplates and diaphragms. However, according to the energy conversion principle, there is a certain loss during the process of converting external sound energy into mechanical energy through vibration. The more layers of backplates and diaphragms there are, the more energy loss there is, and the performance improvement is not obvious. Even in certain cases, the energy is exhausted in the MEMS microphone. Coupled with the limitations of the actual production process and the market's certain requirements for the device thickness, the situation of infinitely stacking backplates and diaphragms is impossible to achieve. According to the data obtained from simulation, the signal transmission effect of the three-backplate double-diaphragm structure is the best. At this time, the energy loss of the MEMS microphone is the smallest, the performance is the strongest, and the structure is also easier to achieve through process means.

[0083] According to the MEMS microphone and its manufacturing method provided by the present invention, by making the thickness of the middle region of the back plate less than that of the edge region, so that the distance from the middle region of the back plate to the diaphragm is greater than the distance from the edge region of the back plate to the diaphragm, without changing the size of the device, the collision between the diaphragm and the back plate during the movement of the diaphragm is avoided, the stability of the MEMS microphone is enhanced, and by increasing the distance between the back plate and the diaphragm, the effective area of the back plate is further increased, thereby increasing the capacitance and improving the sensitivity of the MEMS microphone.

[0084] The present invention has been described through the above embodiments. However, it should be understood that the above embodiments are only for the purpose of illustration and example, and are not intended to limit the present invention to the scope of the described embodiments. In addition, those skilled in the art can understand that the present invention is not limited to the above embodiments, and more variations and modifications can be made according to the teachings of the present invention, and these variations and modifications all fall within the scope of protection required by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalent scope.

Claims

1. A MEMS microphone, characterized in that: It includes at least one back plate and at least one diaphragm, a cavity is formed between the at least one back plate and the at least one diaphragm, the thickness of the middle area of ​​the at least one back plate is smaller than the thickness of the edge area, so that the distance from the middle area of ​​the at least one back plate to the at least one diaphragm is greater than the distance from the edge area of ​​the at least one back plate to the at least one diaphragm.

2. The MEMS microphone according to claim 1, wherein: The at least one back plate includes a first surface and a second surface that are arranged opposite to each other, wherein the first surface is close to the at least one diaphragm, and the first surface of the at least one back plate is in an inwardly concave arc shape or a stepped shape.

3. The MEMS microphone according to claim 1, wherein: The at least one back plate comprises a first surface and a second surface which are arranged opposite to each other, and the first surface and the second surface of the at least one back plate are both in an inwardly concave arc shape or a stepped shape.

4. The MEMS microphone according to claim 1, wherein: The at least one back plate has a plurality of acoustic holes formed therein.

5. The MEMS microphone according to claim 1, wherein: A reinforcement layer is also formed on the surface of the diaphragm to enhance the rigidity of the diaphragm.

6. The MEMS microphone according to claim 1, wherein: It also includes a supporting structure, two ends of the at least one back plate are connected to the supporting structure, and two ends of the at least one diaphragm are connected to the supporting structure through an elastic device.

7. The MEMS microphone according to claim 1, wherein: The MEMS microphone includes one or more of a single-backplate single-diaphragm structure, a double-backplate single-diaphragm structure, and a triple-backplate double-diaphragm structure.

8. A method for manufacturing a MEMS microphone, characterized in that: include: Providing a first substrate, forming a first groove in the first substrate, and forming a diaphragm in the first groove; Providing a second substrate, forming a second groove in the second substrate, wherein a depth of a middle region of the second groove is greater than a depth of an edge region; Bonding the first substrate and the second substrate so that the first groove and the second groove together form a cavity; Etching the second substrate in a region corresponding to the cavity to form a back plate having a plurality of acoustic holes; The region of the first substrate corresponding to the cavity is etched to expose the diaphragm.

9. The method for manufacturing a MEMS microphone according to claim 8, wherein: Forming a second groove in the second substrate includes: forming a dielectric layer on a surface of the second substrate; forming an opening region in the dielectric layer to expose the surface of the second substrate; forming a photoresist layer in the opening region, wherein the thickness of the middle region of the photoresist layer is smaller than the thickness of the edge region; The photoresist layer and the second substrate are etched to form a second groove in the opening area, wherein a depth of a middle area of ​​the second groove is greater than a depth of an edge area.

10. The method for manufacturing a MEMS microphone according to claim 8, wherein: The method further includes forming a third groove in the second substrate, wherein the depth of the middle region of the third groove is greater than the depth of the edge region, and the second groove and the third groove are respectively located on the first surface and the second surface of the second substrate which are oppositely disposed.

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