Diaphragm structure of MEMS microphone and manufacturing method thereof

Abstract

The present application relates to a kind of diaphragm structure of MEMS microphone and its manufacturing method, the diaphragm structure includes the diaphragm membrane layer with air release structure, diaphragm membrane layer is also provided with air hole, diaphragm structure also includes the valve cover covering air hole, valve cover includes the fixed connection of one end of valve cover with diaphragm membrane layer, valve cover is directly contacted with the diaphragm membrane layer of air hole edge around air hole 360 degrees, to completely cover air hole, valve cover is used to open when being subjected to greater than pressure threshold air pressure to expose air hole to carry out air release.The valve cover of the present application is closed state to cover air hole, the diaphragm of MEMS microphone is normally vented by air release structure when sound pressure is small;Valve cover only opens when bearing larger sound pressure, so it can quickly reduce the sound pressure on diaphragm when being subjected to larger sound pressure impact, protect MEMS microphone.Air hole is completely covered by valve cover, so when sound pressure does not reach pressure threshold, air hole has no airflow, and has no effect on the frequency characteristic of microphone.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, and in particular to a diaphragm structure for a MEMS microphone, and a method for manufacturing the diaphragm structure for a MEMS microphone. Background Technology

[0002] Micro-Electro-Mechanical Systems (MEMS) devices are typically manufactured using integrated circuit technology. Silicon-based microphones have broad application prospects in fields such as hearing aids and mobile communication devices. Research on MEMS microphone chips has been ongoing for over 20 years, during which time many types of microphone chips have been developed, including piezoresistive, piezoelectric, and capacitive types, with capacitive MEMS microphones being the most widely used.

[0003] The vent holes on the diaphragm of a MEMS microphone can be, for example, groove-shaped, or circular-hole-shaped. These vent holes have a fixed size, and when the diaphragm is subjected to a large sound pressure impact, the venting capacity cannot be changed. Rapid venting may cause the diaphragm to rupture under excessive pressure, leading to the failure of the entire microphone device. Summary of the Invention

[0004] Therefore, it is necessary to provide a diaphragm structure for a MEMS microphone that has a strong air leakage capability when the diaphragm is subjected to large sound pressure impacts.

[0005] A diaphragm structure for a MEMS microphone includes a diaphragm layer with a venting structure. The diaphragm layer further includes vents, and the diaphragm structure also includes a valve cover covering the vents. The valve cover includes a fixed portion that securely connects one end of the valve cover to the diaphragm layer. The valve cover is in direct contact with the diaphragm layer at the edge of the vent around the vent in a 360-degree radius, thereby completely covering the vent. The valve cover is used to open when subjected to air pressure exceeding a pressure threshold, thereby exposing the vent for venting.

[0006] In the aforementioned MEMS microphone diaphragm structure, the valve cover is normally closed, sealing the vent. When the sound pressure level is low, the diaphragm normally releases air through this venting structure. The valve cover only opens when subjected to higher sound pressure levels, and the higher the sound pressure, the greater the opening and the stronger the venting capacity. Therefore, it can quickly and effectively reduce the sound pressure on the diaphragm under significant sound pressure impact, thus protecting the MEMS microphone. Because the valve cover covers the vent 360 degrees, no airflow passes through the vent when the sound pressure does not reach the pressure threshold. This closed vent state has no impact on the frequency characteristics of the MEMS microphone. Therefore, this novel venting structure neither affects the frequency response of the MEMS microphone nor compromises its venting capacity.

[0007] In one embodiment, the valve cover has a stress gradient in the longitudinal direction that gradually increases in tensile stress from the direction away from the diaphragm layer to the direction approaching the diaphragm layer. The stress gradient causes the valve cover to bend toward the diaphragm layer, thereby closing the vent.

[0008] In one embodiment, the valve cover is made of a flexible material.

[0009] In one embodiment, the venting structure is a vent hole and / or a vent groove.

[0010] In one embodiment, the diaphragm layer comprises a conductive material.

[0011] In one embodiment, the valve cover comprises a conductive material.

[0012] In one embodiment, the valve cover includes a first valve cover and a second valve cover, the first valve cover being disposed on a first surface of the diaphragm layer, and the second valve cover being disposed on a second surface of the diaphragm layer opposite to the first surface.

[0013] In one embodiment, the pressure threshold is less than the upper limit of the sound pressure that the diaphragm layer can withstand.

[0014] It is also necessary to provide a MEMS microphone, including a diaphragm and a backplate disposed opposite to the diaphragm, the diaphragm having the diaphragm structure described in any of the foregoing embodiments.

[0015] In one embodiment, the MEMS microphone further includes a support layer disposed between the backplate and the diaphragm.

[0016] In one embodiment, the backplate is disposed above the diaphragm, or the diaphragm is disposed above the backplate.

[0017] In one embodiment, the MEMS microphone further includes a substrate on which the diaphragm is disposed.

[0018] In one embodiment, the MEMS microphone further includes an insulating layer disposed between the substrate and the diaphragm.

[0019] In one embodiment, the MEMS microphone further includes a first electrode electrically connected to the diaphragm and a second electrode electrically connected to the backplate.

[0020] It is also necessary to provide a method for manufacturing the diaphragm structure of a MEMS microphone.

[0021] A method for manufacturing a diaphragm structure for a MEMS microphone includes: forming a diaphragm layer with vents on a support structure; forming a first sacrificial layer on the diaphragm layer, wherein a first region near the edge of the vents is not covered by the first sacrificial layer; forming a valve cover layer on the diaphragm layer and the first sacrificial layer, wherein the valve cover layer is in direct contact with the diaphragm layer in the first region; the valve cover layer has a stress gradient with gradually increasing tensile stress in the longitudinal direction, wherein the gradual increase is from the direction away from the diaphragm layer to the direction approaching the diaphragm layer; and patterning the valve cover layer to form... A valve cover is formed to cover the vent; the valve cover includes a fixed part located in the first region that fixes one end of the valve cover to the diaphragm film layer; around the vent, the valve cover and the diaphragm film layer are separated by the first sacrificial layer except in the first region; the support structure is removed, and the first sacrificial layer is etched away; wherein, after the first sacrificial layer is removed, the valve cover is in direct contact with the diaphragm film layer at the edge of the vent in all 360 degrees around the vent, thereby completely covering the vent, and the stress gradient causes the valve cover to bend towards the diaphragm film layer to close the vent.

[0022] The manufacturing method of the diaphragm structure of the aforementioned MEMS microphone involves forming a first sacrificial layer, and then forming a valve cover with a stress gradient on the first sacrificial layer. After removing the first sacrificial layer, the stress gradient causes the valve cover to bend towards the diaphragm layer, thereby closing the vent. The valve cover only opens when subjected to a large sound pressure level, and the greater the sound pressure, the greater the opening amplitude and the stronger the venting capacity. Therefore, it can quickly and effectively reduce the sound pressure on the diaphragm when subjected to a large sound pressure impact, thereby protecting the MEMS microphone.

[0023] In one embodiment, before the step of forming the first sacrificial layer on the diaphragm film, a step of forming a second sacrificial layer to fill the pores is included; the step of forming the first sacrificial layer on the diaphragm film is to form the first sacrificial layer on the diaphragm film and the second sacrificial layer; after the step of removing the support structure, a step of etching to remove the second sacrificial layer is included.

[0024] In one embodiment, the support structure is an insulating layer disposed on the substrate; after the step of forming the valve cover covering the vent and before the step of removing the support structure, the step of etching the substrate on the back side to form a back cavity is further included; the back side is the side of the substrate facing away from the diaphragm film layer; the removal of the support structure, the etching to remove the first sacrificial layer, and the etching to remove the second sacrificial layer are all performed using the same etchant.

[0025] In one embodiment, during the step of forming a diaphragm layer with pores on the support structure, the formed diaphragm layer also has a venting structure.

[0026] In one embodiment, the step of forming a valve cap layer on the diaphragm film and the first sacrificial layer includes: depositing polysilicon on the diaphragm film and the first sacrificial layer; and adjusting the doping concentration of the polysilicon by an ion implantation process to form the stress gradient. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of a novel venting structure on the diaphragm of a MEMS microphone in one embodiment;

[0029] Figure 2 This is one embodiment Figure 1 The diagram shown illustrates the venting structure when the valve cover is opened under atmospheric pressure.

[0030] Figure 3 This is a flowchart of a method for manufacturing the diaphragm structure of a MEMS microphone in one embodiment;

[0031] Figure 4 This is a flowchart of a method for manufacturing the diaphragm structure of a MEMS microphone in another embodiment;

[0032] Figures 5a-5f Is adopted Figure 4 The diagram shows a cross-sectional view of the diaphragm structure during the fabrication process of the diaphragm structure for a MEMS microphone. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0035] It should be noted that when an element is described as being "fixed to" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only. When an element or layer is described as being "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it can be directly on, adjacent to, connected to, or coupled to other elements or layers, or there may be an intervening element or layer. Conversely, when an element is described as being "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other elements or layers, there is no intervening element or layer. It should be understood that although the terms first, second, third, A, B, C, etc., may be used to describe various elements, components, areas, layers, and / or parts, these elements, components, areas, layers, and / or parts should not be limited by these terms. These terms are used only to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Therefore, without departing from the teachings of this invention, the first element, component, region, layer, or part discussed below may be referred to as the second element, component, region, layer, or part.

[0036] When the terms “comprising” and / or “including” are used in this specification, they indicate the presence of the stated feature, integral, step, operation, element, and / or component, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or combinations thereof. The singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise.

[0037] Embodiments of the invention are described herein with reference to cross-sectional views illustrating ideal embodiments (and intermediate structures) of the invention, thus allowing for variations in the illustrated shape due to, for example, manufacturing techniques and / or tolerances. Therefore, embodiments of the invention should not be limited to the specific shapes of the regions shown herein, but rather include shape deviations due to, for example, manufacturing techniques. For instance, implantation regions shown as rectangular typically have rounded or curved features at their edges and / or implantation concentration gradients, rather than a binary change from implantation regions to non-implantation regions. Similarly, the buried regions formed by implantation can result in some implantation in the region between the buried region and the surface traversed during implantation. Therefore, the regions shown in the figures are substantially schematic, and their shapes do not represent the actual shapes of regions of the device and do not limit the scope of the invention.

[0038] The traditional vent / vent groove structure described in the background art has fixed dimensions, and its venting capacity cannot be changed when the diaphragm is subjected to a large sound pressure impact. An improved vent is an openable valve structure. When subjected to a large sound pressure impact, the valve opens under the action of sound pressure, thereby improving the venting capacity, which helps to reduce the pressure on the diaphragm and protect the device. However, in this type of vent with valves, there are gaps between the valves, which can affect the frequency characteristics of the MEMS microphone during normal operation.

[0039] This application proposes a novel venting structure for use on the diaphragm of a MEMS microphone. See also... Figure 1 The diaphragm structure of the MEMS microphone includes a diaphragm layer 110 with vents 121, and a valve cover 120 covering the vents 121. The valve cover 120 includes a fixing portion 122 that fixes one end of the valve cover to the diaphragm layer 110. The valve cover 120 is used to open when subjected to air pressure greater than a pressure threshold, thereby exposing the vents 121 for venting. Figure 1 The venting structures shown can be provided on one or more of the diaphragm of each MEMS microphone, and can be used in conjunction with conventional diaphragm venting structures. That is, the diaphragm layer 110 can also be provided with vent holes and / or vent grooves. When the MEMS microphone is working normally, the valve cover 120 is normally closed, covering the vent 121. The diaphragm of the MEMS microphone vents normally through conventional venting structures (e.g., vent holes / vent grooves) when the sound pressure is low. The valve cover 120 only opens when subjected to higher sound pressure, and the higher the sound pressure, the greater the opening range and the stronger the venting capacity. See [reference needed]. Figure 2 Therefore, it can quickly and effectively reduce the sound pressure on the diaphragm when subjected to a large sound pressure impact, thereby protecting the MEMS microphone.

[0040] In one embodiment of this application, one end of the valve cover 120 is in direct contact with the diaphragm layer 110 via the fixed part 122. The valve cover 120 overlaps the diaphragm layer 110 around the vent 121, ensuring direct contact with the diaphragm layer 110 at the edge of the vent 121. This results in the vent 121 being completely covered, with the valve cover 120 completely covering the vent 121. Because the valve cover 120 completely covers the vent 121, no airflow passes through the vent 121 when the sound pressure does not reach the pressure threshold. This closed state of the vent 121 has no impact on the frequency characteristics of the MEMS microphone device. Therefore, this novel venting structure does not affect the frequency response of the MEMS microphone while achieving strong venting capability.

[0041] Generally, the sound pressure level experienced by a MEMS microphone during normal operation is not very high, and the valve cover 120 remaining closed will not cause the diaphragm to rupture. Therefore, the pressure threshold of the valve cover 120 can be designed based on the upper limit of the sound pressure level during normal operation of the MEMS microphone. That is, the valve cover 120 opens when it approaches the upper limit of the sound pressure level, and the pressure threshold is less than the upper limit of the sound pressure level that the diaphragm layer 110 can withstand. In other words, the pressure threshold should be less than the sound pressure level that would cause the diaphragm layer 110 to rupture.

[0042] In one embodiment of this application, the valve cover 120 has a stress gradient in the longitudinal direction where the tensile stress gradually increases (from the direction away from the diaphragm layer 110 to the direction approaching the diaphragm layer 110, in...). Figure 1 In the valve cover 120 shown, the tensile stress gradually increases from top to bottom. This stress gradient causes the valve cover 120 to bend towards the diaphragm layer 110, thereby closing the vent 121. Figure 1 In the embodiment shown, the fixing part 122 is located longitudinally between the diaphragm film layer 110 and other parts of the valve cover 120, thereby raising the valve cover 120. Since the valve cover 120 has the aforementioned stress gradient, it bends toward the diaphragm film layer 110 at a position other than the fixing part 122, thereby covering the vent 121 360 degrees.

[0043] In one embodiment of this application, the valve cover 120 is made of a flexible material, meaning it is a material that allows the valve cover 120 to bend when opened under high sound pressure. In one embodiment of this application, the valve cover 120 may be made of the same material as the diaphragm layer 110. In one embodiment of this application, the valve cover 120 is made of polycrystalline silicon.

[0044] In one embodiment of this application, the diaphragm structure is a diaphragm of a capacitive MEMS microphone. In another embodiment of this application, the diaphragm layer 110 includes a conductive material, and / or the valve cover 120 includes a conductive material.

[0045] In one embodiment of this application, the diaphragm structure may include two sets of valve covers 120 in different directions to provide bidirectional venting function. Specifically, one set of valve covers 120 is disposed on the upper surface of the diaphragm layer 110, with the tensile stress of the valve cover 120 gradually increasing from top to bottom, and the stress gradient causing the valve cover 120 to bend downwards to cover the vent hole 121; the other set of valve covers 120 is disposed on the lower surface of the diaphragm layer 110, with the tensile stress of the valve cover 120 gradually increasing from bottom to top, and the stress gradient causing the valve cover 120 to bend upwards to cover the vent hole 121.

[0046] This application provides a MEMS microphone, including a diaphragm and a backplate disposed opposite to the diaphragm, wherein the diaphragm has the diaphragm structure described in any of the foregoing embodiments. In one embodiment of this application, the MEMS microphone is a capacitive MEMS microphone, with the backplate and diaphragm each serving as one electrode of a parallel-plate capacitor, i.e., one of the backplate and the diaphragm serves as the lower electrode layer, and the other as the upper electrode layer. The MEMS microphone also includes a support layer disposed between the backplate and the diaphragm for supporting the upper electrode layer. A portion of the space between the backplate and the diaphragm is not provided with a support layer, thus forming a cavity.

[0047] In one embodiment of this application, the MEMS microphone further includes a substrate, with a lower electrode layer disposed on the substrate. In one embodiment of this application, the substrate material is Si; in other embodiments, the substrate material may also be other semiconductors or semiconductor compounds, such as one of Ge, SiGe, SiC, SiO2, or Si3N4. A back cavity is formed in the middle of the substrate, and the back cavity is correspondingly disposed to the cavity (the cavity between the back plate and the diaphragm), that is, the back cavity is disposed directly below the cavity.

[0048] In one embodiment of this application, the MEMS microphone further includes an insulating layer disposed between the substrate and the lower electrode layer. The insulating layer serves to insulate the substrate and the lower electrode layer from each other. In one embodiment of this application, the insulating layer also serves as an etch stop layer for back cavity etching. In one embodiment of this application, the insulating layer may be made of silicon oxide, such as silicon dioxide.

[0049] In one embodiment of this application, the support layer is a sacrificial layer, and the cavity is actually formed by the release of the sacrificial layer. During the release process, the sacrificial layer at the cavity location is corroded away to form the cavity.

[0050] In one embodiment of this application, the MEMS microphone further includes a first electrode electrically connected to the diaphragm and a second electrode electrically connected to the backplane. The first and second electrodes are used to lead out the diaphragm and backplane respectively during the MEMS microphone packaging wire bonding process, forming an electrical connection with an ASIC (Application Specific Integrated Circuit) or a printed circuit board (PCB). In one embodiment of this application, the first electrode is disposed on the upper surface of the diaphragm, and can be located away from the central region of the diaphragm, near the edge of the diaphragm. The second electrode is also located away from the central region of the backplane. In one embodiment of this application, both the first and second electrodes are made of conductive metal.

[0051] This application provides a method for manufacturing a diaphragm structure for a MEMS microphone. Figure 3 This is a flowchart of a method for manufacturing a diaphragm structure for a MEMS microphone, including the following steps:

[0052] S310 forms a diaphragm layer with pores on the supporting structure.

[0053] The diaphragm layer needs to be formed on a structure that can support the diaphragm layer. In one embodiment of this application, the supporting structure is an insulating layer. An air hole penetrates the diaphragm layer, and the bottom of the air hole exposes a portion of the insulating layer beneath the diaphragm layer.

[0054] S320 forms the first sacrificial layer on the diaphragm film.

[0055] A region (hereinafter referred to as the first region) is left near the edge of the vent and is not covered by the first sacrificial layer. In subsequent steps, a valve cover fixing part that is in direct contact with the diaphragm layer needs to be formed in the first region.

[0056] S330, a valve cover layer is formed on the diaphragm layer and the first sacrificial layer.

[0057] The valve cover layer is in direct contact with the diaphragm layer in the first region. The valve cover layer has a stress gradient in the longitudinal direction where the tensile stress gradually increases (from the direction away from the diaphragm layer to the direction approaching the diaphragm layer).

[0058] S340, patterned valve cover layer, forming a valve cover that covers the vent.

[0059] The valve cover includes a fixed portion located in the first region that securely connects one end of the valve cover to the diaphragm layer. Around the vent, the valve cover and the diaphragm layer are separated by a first sacrificial layer, except in the first region.

[0060] S350, remove the support structure and etch away the first sacrificial layer.

[0061] After step S340 is completed, other process steps for the MEMS microphone continue. For example, for a capacitive MEMS microphone with the diaphragm at the bottom and the backplate at the top, after step S340, a sacrificial layer as a support layer is formed on the valve cover and the first sacrificial layer, then a backplate is formed on the sacrificial layer, then a first electrode is formed on the diaphragm layer, and a second electrode is formed on the backplate. After that, step S350 can be executed. The support structure can be removed from the back side. In one embodiment of this application, only a portion of the support structure is removed in the middle, allowing the diaphragm layer to vibrate up and down, while the edge support structure is retained to support the diaphragm layer. After the first sacrificial layer is removed, the valve cover is in direct contact with the diaphragm layer at the edge of the vent in 360 degrees around the vent, thereby completely covering the vent. The stress gradient in the valve cover causes the valve cover to bend towards the diaphragm layer, thereby closing the vent.

[0062] The manufacturing method of the diaphragm structure of the aforementioned MEMS microphone involves forming a first sacrificial layer, and then forming a valve cover with a stress gradient on the first sacrificial layer. After removing the first sacrificial layer, the stress gradient causes the valve cover to bend towards the diaphragm layer, thereby closing the vent. The valve cover only opens when subjected to a large sound pressure level, and the greater the sound pressure, the greater the opening amplitude and the stronger the venting capacity. Therefore, it can quickly and effectively reduce the sound pressure on the diaphragm when subjected to a large sound pressure impact, thereby protecting the MEMS microphone.

[0063] Figure 4 In another embodiment, the process flow of the method for manufacturing the diaphragm structure of a MEMS microphone includes the following steps:

[0064] S410 forms a diaphragm layer with pores on the supporting structure.

[0065] See Figure 5a In one embodiment of this application, the support structure is an insulating layer 202. In one embodiment of this application, the diaphragm film layer 210 is made of polycrystalline silicon. In one embodiment of this application, polycrystalline silicon is deposited on the insulating layer 202, and then the deposited polycrystalline silicon is patterned to form pores 211. The pores 211 penetrate the diaphragm film layer 210, and the bottom of the pores 211 exposes a portion of the insulating layer 202 beneath the diaphragm film layer 210. Patterning can be performed using photolithography and etching processes. In one embodiment of this application, conventional venting structures, such as vent holes and / or vent grooves, are also formed during the patterning and deposition of polycrystalline silicon.

[0066] S420 forms a second sacrificial layer that fills the pores.

[0067] In one embodiment of this application, a sacrificial layer material may be deposited on the insulating layer 202 and the diaphragm layer 210 (see [link]). Figure 5bThe sacrificial layer material is filled into the pores 211, and then the sacrificial layer material on the surface of the diaphragm layer 210 is removed. Specifically, the sacrificial layer material on the diaphragm layer 210 can be removed by chemical mechanical polishing (CMP). The sacrificial layer material in the pores 211 is retained as the second sacrificial layer 232. See [link to documentation]. Figure 5c In one embodiment of this application, the material of the second sacrificial layer 232 is silicon oxide, such as silicon dioxide.

[0068] S430, a first sacrificial layer is formed on the diaphragm film and the second sacrificial layer.

[0069] In one embodiment of this application, a sacrificial layer material (which may be the same material as the second sacrificial layer 232) can be deposited on the diaphragm film layer 210 and the second sacrificial layer 232, and then a first sacrificial layer 234 can be patterned to form it. The thickness of the first sacrificial layer 234 is less than the thickness of the diaphragm film layer 210. In one embodiment of this application, the location where the valve cover fixing portion needs to be formed is determined by photolithography and etching. Figure 5d The first sacrificial layer 234 (marked as the first region 231) is removed, exposing the portion of the diaphragm layer 210 beneath the first sacrificial layer 234. In one embodiment of this application, the first region 231 is located near the edge of the second sacrificial layer 232 (i.e., near the edge of the vent 211).

[0070] S440, a valve cover layer is formed on the diaphragm layer and the first sacrificial layer.

[0071] In one embodiment of this application, polysilicon is deposited as a valve cover layer 22 on the diaphragm film layer 210 and the first sacrificial layer 234, see [link to relevant documentation]. Figure 5e The valve cap layer 22 has a stress gradient in the longitudinal direction, with the tensile stress gradually increasing (from the direction away from the diaphragm layer 210 to the direction approaching the diaphragm layer 210). To achieve this stress gradient in the valve cap layer 22, the doping concentration of the polysilicon can be adjusted through an ion implantation process. The trend of the doping concentration change in the longitudinal direction of the valve cap layer 22 can be a gradual increase, a gradual decrease, an increase followed by a decrease, or a decrease followed by an increase. The tensile stress of the valve cap layer 22 can also be adjusted through a subsequent annealing process.

[0072] S450, patterned valve cover layer, forming a valve cover that covers the vent.

[0073] In one embodiment of this application, a valve cap 220 is formed by photolithography and etching of the valve cap layer 22. The valve cap 220 includes a valve cap located in a first region 231. Figure 5f(Not shown in the text) The fixing part 222 fixes one end of the valve cover 220 to the diaphragm layer 210. That is, the fixing part 222 and the other parts of the valve cover 220 are an integrated structure formed at the same time. In the air hole 211 ( Figure 5f (Not shown in the image) Around the valve cover 220 and the diaphragm layer 210, except for the first region 231, the valve cover 220 and the diaphragm layer 210 are separated by the first sacrificial layer 234. It can also be understood that the fixed part 222 of the valve cover 220 passes through the first sacrificial layer 234 and is fixedly connected to the diaphragm layer 210.

[0074] S460, remove the support structure and etch away the first and second sacrificial layers.

[0075] In one embodiment of this application, the insulating layer 202 in step S410 is formed on the substrate. In one embodiment of this application, the substrate material is Si; in other embodiments, the substrate material may also be other semiconductors or semiconductor compounds, such as Ge, SiGe, SiC, SiO2, or Si3N4. After step S450 is completed, other process steps of the MEMS microphone are performed. For example, for a capacitive MEMS microphone with the diaphragm at the bottom and the backplate at the top, after step S340, a third sacrificial layer as a support layer is formed on the valve cover 220 and the first sacrificial layer 234, and then a backplate is formed on the third sacrificial layer. Then, a first electrode is formed on the diaphragm film layer 210, and a second electrode is formed on the backplate. Before step S460, the substrate is etched on the back side to form a back cavity, and the insulating layer 202 serves as an etching stop layer for the back cavity etching. The insulating layer 202, the first sacrificial layer 234, the second sacrificial layer 232, and the third sacrificial layer can all be made of silicon oxide, such as silicon dioxide. Therefore, an etchant can be used to remove the insulating layer 202, the first sacrificial layer 234, the second sacrificial layer 232, and the third sacrificial layer. In one embodiment of this application, only a portion of the insulating layer 202 in the middle is removed, allowing the diaphragm layer 210 to vibrate up and down. The insulating layer 202 at the edges is retained to support the diaphragm layer 210 and to insulate it from the substrate.

[0076] After the first sacrificial layer 234 and the second sacrificial layer 232 are released, one end of the valve cover 220 directly contacts the diaphragm layer 210 through the fixed part 222. The valve cover 220 overlaps with the diaphragm layer 210 at the edge of the vent 221 around the vent 221. In this way, the valve cover 220 is in direct contact with the diaphragm layer 210 at the edge of the vent 221 at all 360 degrees around the vent, thus completely covering the vent 221. The stress gradient in the valve cover 220 causes it to bend towards the diaphragm layer 210, thereby closing the vent 221. The structure after step S460 can be referred to... Figure 1 .

[0077] It should be understood that although the steps in the flowchart of this application are shown sequentially as indicated by the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowchart of this application may include multiple steps or multiple stages, which are not necessarily completed at the same time, but may be executed at different times, and the execution order of these steps or stages is not necessarily sequential, but may be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0078] In the description of this specification, references to terms such as "some embodiments," "other embodiments," and "ideal embodiments" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0079] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features of the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0080] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A diaphragm structure of a MEMS microphone, comprising a diaphragm membrane layer having a vent structure, characterized in that, The diaphragm layer is also provided with vents, and the diaphragm structure further includes a valve cover covering the vents. The valve cover includes a fixed connection portion that fixes one end of the valve cover to the diaphragm layer. The valve cover is in direct contact with the edge of the vent in the diaphragm layer, thereby completely covering the vent. The valve cover is used to open when subjected to air pressure greater than a pressure threshold, thereby exposing the vent for air release. The valve cover has a stress gradient in the longitudinal direction where the tensile stress gradually increases. The gradual increase is from the direction away from the diaphragm layer to the direction approaching the diaphragm layer. The stress gradient causes the valve cover to bend towards the diaphragm layer, thereby covering the vent.

2. The diaphragm structure of a MEMS microphone according to claim 1, wherein, The venting structure is a vent hole and / or a vent groove.

3. The diaphragm structure of a MEMS microphone according to claim 1, wherein, The diaphragm layer includes a conductive material, and / or the valve cover includes a conductive material.

4. The diaphragm structure of a MEMS microphone according to any one of claims 1-3, wherein, The valve cover includes a first valve cover and a second valve cover. The first valve cover is disposed on a first surface of the diaphragm layer, and the second valve cover is disposed on a second surface of the diaphragm layer opposite to the first surface.

5. A method for manufacturing a diaphragm structure for a MEMS microphone, comprising: A diaphragm layer with pores is formed on the supporting structure; A first sacrificial layer is formed on the diaphragm film, and the first region near the edge of the pore is not covered by the first sacrificial layer; A valve cover layer is formed on the diaphragm film and the first sacrificial layer, the valve cover layer being in direct contact with the diaphragm film in the first region; the valve cover layer has a stress gradient in the longitudinal direction in which the tensile stress gradually increases from the direction away from the diaphragm film to the direction approaching the diaphragm film. The valve cover layer is patterned to form a valve cover covering the air hole; the valve cover includes a fixed part located in the first region that fixes one end of the valve cover to the diaphragm film layer; around the air hole, the valve cover and the diaphragm film layer are separated by the first sacrificial layer except in the first region. Remove the supporting structure and etch away the first sacrificial layer; In this process, after the first sacrificial layer is removed, the valve cover comes into direct contact with the diaphragm layer at the edge of the vent, thereby completely covering the vent. The stress gradient causes the valve cover to bend toward the diaphragm layer, thereby covering the vent.

6. The method of claim 5, wherein the method further comprises: Before the step of forming the first sacrificial layer on the diaphragm film, the method further includes the step of forming a second sacrificial layer that fills the pores; The step of forming the first sacrificial layer on the diaphragm film layer is to form the first sacrificial layer on the diaphragm film layer and the second sacrificial layer; After the step of removing the support structure, the method further includes a step of eroding to remove the second sacrificial layer.

7. The method for manufacturing the diaphragm structure of the MEMS microphone according to claim 6, characterized in that, After the step of patterning the valve cover layer and before the step of removing the support structure, the method further includes: A third sacrificial layer is formed on the valve cover and on the first sacrificial layer; A backplate is formed on the third sacrificial layer; A first electrode is formed on the diaphragm layer, and a second electrode is formed on the back plate; The step of removing the support structure further includes: corroding away part of the third sacrificial layer, with the remaining third sacrificial layer serving as the support layer of the back plate.

8. The method of claim 7, wherein the method further comprises: The supporting structure is an insulating layer disposed on the substrate; After the step of forming the valve cover covering the vent and before the step of removing the support structure, the method further includes a step of etching the substrate on the back side to form a back cavity; the back side is the side of the substrate that faces away from the diaphragm film layer. The removal of the support structure, the etching removal of the first sacrificial layer, the etching removal of the second sacrificial layer, and the etching removal of part of the third sacrificial layer all use the same etchant.

9. The method of claim 8, wherein the method further comprises: forming a first electrode layer on the first surface of the substrate; forming a second electrode layer on the second surface of the substrate; and forming a diaphragm layer on the first electrode layer and the second electrode layer. The step of forming a second sacrificial layer that fills the pores includes: A sacrificial layer material is deposited on the insulating layer and the diaphragm film, so that the sacrificial layer material fills the pores; The sacrificial layer material on the diaphragm is removed by a chemical mechanical polishing process, and the sacrificial layer material in the pores is retained as the second sacrificial layer.

10. The method of claim 5, wherein the method further comprises: forming a diaphragm structure of the MEMS microphone. In the step of forming a diaphragm layer with pores on the support structure, the diaphragm layer also has a venting structure.

11. The method of manufacturing a diaphragm structure of a MEMS microphone according to any one of claims 5 to 10, wherein The step of forming a valve cover layer on the diaphragm layer and the first sacrificial layer includes: Polycrystalline silicon is deposited on the diaphragm film and the first sacrificial layer; The stress gradient is formed by adjusting the doping concentration of the polycrystalline silicon through an ion implantation process.

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