Preparation method of MEMS device and MEMS device

Abstract

The present application relates to a method for preparing a MEMS device and the MEMS device, comprising: a substrate, comprising a first surface and a second surface opposite to each other; a first diaphragm, located on the first surface side, comprising a first movable area and a first fixed area; a first protruding structure, located on a side of the first diaphragm away from the substrate and connected to the first movable area, the cross-sectional area of ​​the first protruding structure decreasing along a first direction, the cross-section being a plane parallel to the first surface, and the first direction being a direction from the second surface to the first surface; the material of the first protruding structure comprising SiN, the Si content in the first protruding structure decreasing and the N content increasing along the first direction; a first supporting structure, located on a side of the first diaphragm away from the substrate and connected to the first fixed area; a back plate, located on a side of the first supporting structure away from the first diaphragm; wherein, in the first direction, the projection of the first protruding structure falls within the projection range of the back plate; in this way, the reliability of the device is improved.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a method for preparing a MEMS device and a MEMS device. Background Art

[0002] With the rapid development of electronic technology, micro-electro-mechanical system (MEMS) devices have become increasingly widely used due to their advantages such as small size, easy installation, high temperature resistance, good stability, high degree of automation, and suitability for mass production. Among the many MEMS devices, MEMS microphones and MEMS pressure sensors utilize capacitors formed by a diaphragm and a back plate to achieve their device functions. Specifically, the vibration of the diaphragm changes the distance between the diaphragm and the back plate, which in turn changes the capacitance of the capacitor. This capacitance change can be amplified and converted into an electrical signal output, thereby achieving the device function.

[0003] The deformation of the diaphragm during vibration is usually temporary and recoverable. However, in the actual preparation process, the diaphragm will undergo multiple subsequent high-temperature processes after formation, which will weaken the strength of the diaphragm. Then, the diaphragm may undergo permanent deformation during the vibration process, causing changes in the capacitor formed by the diaphragm and the back plate, thereby reducing the reliability of the device. Summary of the Invention

[0004] In view of this, embodiments of the present application provide a method for manufacturing a MEMS device and a MEMS device to solve at least one problem existing in the background technology.

[0005] In a first aspect, an embodiment of the present application provides a MEMS device, including:

[0006] a substrate comprising a first surface and a second surface opposite to each other;

[0007] a first diaphragm located on the first surface side, the first diaphragm including a first movable area and a first fixed area located outside the first movable area;

[0008] a first protruding structure located on a side of the first diaphragm away from the substrate and connected to the first movable region, wherein a cross-sectional area of ​​the first protruding structure decreases along a first direction, the cross-section being a plane parallel to the first surface, and the first direction being a direction from the second surface to the first surface; the first protruding structure being made of SiN, wherein a Si content in the first protruding structure decreases and a N content increases along the first direction;

[0009] a first supporting structure, located on a side of the first diaphragm away from the substrate and connected to the first fixing area;

[0010] A back plate is located on a side of the first supporting structure away from the first diaphragm; wherein, in the first direction, the projection of the first protruding structure falls within the projection range of the back plate.

[0011] In conjunction with the first aspect of the present application, in an optional implementation manner, the method further includes:

[0012] a first reinforcement structure located on a side of the first diaphragm away from the substrate, the cross-sectional area of ​​the first reinforcement structure decreasing along the first direction, and the first reinforcement structure and the first protruding structure formed in the same process based on the same material layer;

[0013] Part of the first reinforcement structure is embedded in the first support structure.

[0014] In combination with the first aspect of the present application, in an optional embodiment, within the same plane, the cross-sectional area of ​​the first reinforcement structure is greater than the cross-sectional area of ​​the first protruding structure.

[0015] In conjunction with the first aspect of the present application, in an optional implementation manner, the method further includes:

[0016] a second diaphragm, located on a side of the back plate away from the first diaphragm;

[0017] a second supporting structure, located between the back plate and the second diaphragm, so that the second diaphragm is spaced apart from the back plate;

[0018] a through opening, passing through the back plate along the first direction;

[0019] a support column comprising a first support portion connected to the first diaphragm, a third support portion connected to the second diaphragm, and a second support portion connected between the first support portion and the third support portion along the first direction; the cross-sectional area of ​​the first support portion decreases along the first direction; the cross-sectional area of ​​the third support portion increases along the first direction; the second support portion passes through the through opening; the cross-sectional areas of the first support portion and the third support portion are both greater than the cross-sectional area of ​​the second support portion;

[0020] The first supporting portion and the first protruding structure are formed in the same process based on the same material layer;

[0021] A material of the third supporting portion includes SiN, and a Si content in the third supporting portion increases and a N content decreases along the first direction.

[0022] In conjunction with the first aspect of the present application, in an optional embodiment, the second diaphragm includes a second movable area and a second fixed area located outside the second movable area;

[0023] The MEMS device further includes: a second protruding structure, located on a side of the second diaphragm facing the back plate and connected to the second movable region, wherein the cross-sectional area of ​​the second protruding structure increases along the first direction; wherein, in the first direction, a projection of the second protruding structure falls within a projection range of the back plate;

[0024] The second protruding structure and the third supporting portion are formed in the same process based on the same material layer.

[0025] In a second aspect, an embodiment of the present application provides a method for preparing a MEMS device, the method comprising:

[0026] providing a substrate comprising a first surface and a second surface opposite to each other;

[0027] forming a first diaphragm on the first surface side, the first diaphragm including a first movable area and a fixed area located outside the first movable area;

[0028] forming a first semiconductor material layer on the first diaphragm, wherein the material of the first semiconductor material layer includes SiN, and the Si content of the first semiconductor material layer decreases and the N content increases along a first direction, wherein the first direction is from the second surface to the first surface;

[0029] Performing a first wet etching process on the first semiconductor material layer to form a first protruding structure on the first movable area, wherein the cross-sectional area of ​​the first protruding structure decreases along the first direction, and the cross-sectional area is a plane parallel to the first surface;

[0030] forming a first sacrificial layer covering the first diaphragm and the first protruding structure;

[0031] A back plate is formed on the first sacrificial layer; wherein, in the first direction, the projection of the first protruding structure falls within the projection range of the back plate.

[0032] In conjunction with the second aspect of the present application, in an optional embodiment,

[0033] The first semiconductor material layer is subjected to a first wet etching process to form a first reinforcement structure, wherein the first reinforcement structure is located on a side of the first diaphragm away from the substrate and connected to the first fixing region, and the cross-sectional area of ​​the first reinforcement structure decreases along the first direction;

[0034] After forming the back plate on the first sacrificial layer, the method further includes: removing part of the first sacrificial layer, forming the remaining first sacrificial layer into a first supporting structure located on the first fixed area, and partially embedding the first reinforcing structure into the first supporting structure.

[0035] In conjunction with the second aspect of the present application, in an optional embodiment,

[0036] In the same plane, the cross-sectional area of ​​the first reinforcement structure is greater than the cross-sectional area of ​​the first protruding structure.

[0037] In conjunction with the second aspect of the present application, in an optional embodiment,

[0038] The first semiconductor material layer is subjected to a first wet etching process to form a first supporting portion, wherein the cross-sectional area of ​​the first supporting portion decreases along the first direction;

[0039] A through opening is formed in the back plate and penetrates the back plate along a first direction;

[0040] After forming the back plate on the first sacrificial layer, the method further includes:

[0041] forming a second sacrificial layer covering the back plate and filling the through hole;

[0042] forming a through hole penetrating the second sacrificial layer and the first sacrificial layer and passing through the through opening, wherein the through hole exposes the first supporting portion;

[0043] filling a second semiconductor material layer in the through hole to form a second supporting portion;

[0044] forming a third semiconductor material layer covering the second sacrificial layer and the second supporting portion, wherein the material of the third semiconductor material layer includes SiN, and the Si content in the third semiconductor material layer increases and the N content decreases along the first direction;

[0045] performing a second wet etching process on the third semiconductor material layer to form a third supporting portion, wherein the cross-sectional area of ​​the third supporting portion increases along the first direction; the first supporting portion, the second supporting portion, and the third supporting portion are sequentially connected to form a supporting column, wherein the cross-sectional area of ​​the first supporting portion and the cross-sectional area of ​​the third supporting portion are both greater than the cross-sectional area of ​​the second supporting portion;

[0046] A second diaphragm is formed on the third supporting portion.

[0047] In conjunction with the second aspect of the present application, in an optional embodiment, the second diaphragm includes a second movable area and a second fixed area located outside the second movable area;

[0048] The second wet etching process is performed on the third semiconductor material layer to form a second protruding structure. The second protruding structure is located on the side of the second diaphragm facing the back plate and is connected to the second movable area. The cross-sectional area of ​​the second protruding structure increases along the first direction; wherein, in the first direction, the projection of the second protruding structure falls within the projection range of the back plate.

[0049] In conjunction with the second aspect of the present application, in an optional embodiment, before forming the second diaphragm on the third supporting portion, the method further includes: forming a third sacrificial layer covering the sidewalls of the third supporting portion and the second sacrificial layer, wherein the top surface of the third sacrificial layer and the top end of the third supporting portion form a flat plane, the top surface of the third sacrificial layer being a surface of the third sacrificial layer away from the second sacrificial layer, and the top end of the third supporting portion being an end of the third supporting portion away from the second sacrificial layer;

[0050] The second diaphragm covers the third sacrificial layer and the third supporting portion.

[0051] Compared with the prior art, the embodiments of the present application have the following beneficial effects:

[0052] The MEMS device provided in the embodiment of the present application includes: a substrate, the substrate including a first surface and a second surface opposite to each other; a first diaphragm, located on the side of the first surface, the first diaphragm including a first movable area and a first fixed area located on the periphery of the first movable area; a first protruding structure, located on a side of the first diaphragm away from the substrate and connected to the first movable area, the cross-sectional area of ​​the first protruding structure decreases along a first direction, the cross-section is a plane parallel to the first surface, and the first direction is the direction from the second surface to the first surface; the material of the first protruding structure includes SiN, and the Si content in the first protruding structure decreases and the N content increases along the first direction; a first supporting structure, located on a side of the first diaphragm away from the substrate and connected to the first fixed area; a back plate, located on a side of the first supporting structure away from the first diaphragm; wherein, in the first direction, the projection of the first protruding structure falls within the projection range of the back plate. Therefore, by forming the first protruding structure on the movable area of ​​the first diaphragm, the thickness and strength of the movable area of ​​the first diaphragm are increased, and the risk of permanent deformation due to insufficient strength of the diaphragm is reduced; the projection of the first protruding structure falls within the projection range of the back plate, and the first protruding structure can also serve as an anti-adhesion structure to prevent the diaphragm from adhering to the back plate when vibrating, thereby reducing the risk of device failure; and the cross-sectional area of ​​the first protruding structure decreases along the first direction, while ensuring the reinforcing effect of the first protruding structure on the strength of the first diaphragm, the contact area between the first protruding structure and the back plate is reduced, thereby shortening the contact time between the first protruding structure and the back plate, and after the first protruding structure contacts the back plate , the first diaphragm can bounce back faster in the direction away from the back plate, reducing the risk of permanent deformation of the first diaphragm due to maintaining contact for a long time; in addition, since the material of the first protruding structure includes SiN, and the Si content in the first protruding structure decreases and the N content increases along the first direction, the part of the material layer used to form the first protruding structure that is farther away from the first diaphragm is easier to be etched and removed, so that during the preparation process, the etchant etches the material layer progressively along the first direction, and the first protruding structure with a cross-sectional area decreasing along the first direction can be directly etched, so that the first protruding structure has higher dimensional accuracy, better contour consistency, and higher strength; ultimately, the reliability of the device is improved.

[0053] The preparation method of the MEMS device provided in the embodiment of the present application includes: providing a substrate, the substrate including a first surface and a second surface opposite to each other; forming a first diaphragm on the first surface side, the first diaphragm including a first movable area and a first fixed area located on the periphery of the first movable area; forming a first semiconductor material layer on the first diaphragm, the material of the first semiconductor material layer including SiN, the Si content in the first semiconductor material layer decreases and the N content increases along a first direction, the first direction being the direction from the second surface to the first surface; performing a first wet etching process on the first semiconductor material layer to form a first protruding structure on the first movable area, the cross-sectional area of ​​the first protruding structure decreases along the first direction, and the cross-section is a plane parallel to the first surface; forming a first sacrificial layer covering the first diaphragm and the first protruding structure; forming a back plate on the first sacrificial layer; wherein, in the first direction, the projection of the first protruding structure falls within the projection range of the back plate. Thus, by forming the first protruding structure on the movable area of ​​the first diaphragm, the thickness and strength of the movable area of ​​the first diaphragm are increased, and the risk of permanent deformation due to insufficient strength of the diaphragm is reduced; the projection of the first protruding structure falls within the projection range of the back plate, and the first protruding structure can also serve as an anti-adhesion structure to prevent the diaphragm from adhering to the back plate when vibrating, thereby reducing the risk of device failure; and the cross-sectional area of ​​the first protruding structure decreases along the first direction, while ensuring the reinforcing effect of the first protruding structure on the strength of the first diaphragm, the contact area between the first protruding structure and the back plate is reduced, thereby shortening the contact between the first protruding structure and the back plate. The contact time is shorter than that of the first protruding structure. After the first protruding structure contacts the back plate, the first diaphragm can bounce away from the back plate more quickly, thereby reducing the risk of permanent deformation of the first diaphragm due to the long contact time. Specifically, by controlling the Si content in the first semiconductor material layer to decrease and the N content to increase along the first direction, the part of the first semiconductor material layer farther away from the first diaphragm is easier to be etched and removed, so that the first protruding structure with a reduced cross-sectional area along the first direction can be directly etched, so that the first protruding structure has higher dimensional accuracy, better contour consistency and higher strength. Ultimately, the prepared device has higher reliability.

[0054] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0056] Figure 1 A schematic cross-sectional view of a MEMS device according to an embodiment of the present invention;

[0057] Figure 2 A schematic cross-sectional structure diagram of a first protruding structure, a first reinforcing structure, and a first supporting portion provided as a specific example;

[0058] Figure 3 A schematic cross-sectional structure diagram of a second protruding structure, a second reinforcing structure, and a third supporting portion provided as a specific example;

[0059] Figure 4 A schematic diagram of a process for preparing a MEMS device according to an embodiment of the present application;

[0060] Figure 5 A schematic cross-sectional structure diagram of a first semiconductor material layer provided in an embodiment of the present application;

[0061] Figure 6 A schematic cross-sectional structure diagram of a first semiconductor material layer provided as a specific example;

[0062] Figure 7 A schematic cross-sectional view of the first protruding structure, the first reinforcing structure, and the first supporting portion provided in an embodiment of the present application;

[0063] Figure 8 A schematic diagram of the cross-sectional structure of the back plate and the second sacrificial layer provided in an embodiment of the present application;

[0064] Figure 9 A schematic diagram of the cross-sectional structure of a through hole provided in an embodiment of the present application;

[0065] Figure 10 A schematic cross-sectional structure diagram of a third semiconductor material layer provided in an embodiment of the present application;

[0066] Figure 11 A schematic cross-sectional structure diagram of a third semiconductor material layer provided as a specific example;

[0067] Figure 12 A schematic cross-sectional view of the second protruding structure, the second reinforcing structure, and the third supporting portion provided in an embodiment of the present application;

[0068] Figure 13 A schematic cross-sectional structure diagram of a third sacrificial layer provided in an embodiment of the present application;

[0069] Figure 14 A schematic cross-sectional view of the second diaphragm provided in an embodiment of the present application;

[0070] Figure 15 This is a schematic diagram of the cross-sectional structure of the back cavity provided in an embodiment of the present application.

[0071] Description of reference numerals:

[0072] 100, substrate; 101, first surface; 102, second surface; 103, back cavity;

[0073] 210, first diaphragm; 211, first movable area; 212, first fixed area; 213, first air hole; 220, second diaphragm; 221, second movable area; 222, second fixed area; 223, second air hole;

[0074] 300, first semiconductor material layer; 301, first sublayer of first material layer; 302, second sublayer of first material layer; 303, third sublayer of first material layer;

[0075] 310, first protruding structure;

[0076] 410, first reinforcement structure;

[0077] 500, support column; 510, first support portion; 520, second support portion; 530, third support portion;

[0078] 610, first sacrificial layer; 611, first supporting structure; 620, second sacrificial layer; 621, second supporting structure; 630, third sacrificial layer; 640, fourth sacrificial layer; 641, third supporting structure; 601, first cavity; 602, second cavity; 603, third cavity; 604, through hole;

[0079] 700, back electrode plate; 710, first back electrode insulating layer; 720, back electrode conductive layer; 730, second back electrode insulating layer; 701, through port;

[0080] 800, third semiconductor material layer; 801, first sublayer of third material layer; 802, second sublayer of third material layer; 803, third sublayer of third material layer;

[0081] 810, second raised structure;

[0082] 910. Second reinforcement structure. DETAILED DESCRIPTION

[0083] The exemplary embodiments disclosed herein will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present application are shown in the accompanying drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the specific embodiments described herein. Rather, these embodiments are provided to enable a more thorough understanding of the present application and to fully convey the scope of the present application to those skilled in the art.

[0084] In the following description, numerous specific details are provided to provide a more thorough understanding of the present application. However, it will be apparent to those skilled in the art that the present application can be practiced without one or more of these details. In other instances, certain technical features known in the art are not described to avoid confusion with the present application; that is, all features of actual embodiments are not described herein, nor are well-known functions and structures described in detail.

[0085] In the drawings, the sizes of layers, regions, elements and their relative sizes may be exaggerated for clarity. Like reference numerals denote like elements throughout.

[0086] When an element or layer is referred to as being "on," "adjacent to," "connected to," or "coupled to" another element or layer, it may be directly on, adjacent to, connected to, or coupled to the other element or layer, or there may be intervening elements or layers. 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. Although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are merely used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Therefore, without departing from the teachings of the present application, the first element, component, region, layer, or part discussed below may be represented as the second element, component, region, layer, or part. However, when the second element, component, region, layer, or part is discussed, it does not necessarily mean that the first element, component, region, layer, or part exists in the present application.

[0087] Spatially relative terms such as "under," "beneath," "below," "under," "above," "above," etc., may be used herein for convenience of description to describe the relationship of an element or feature shown in the figures to other elements or features. In addition to the orientations shown in the figures, spatially relative terms are intended to also include different orientations of the device in use and operation. For example, if the device in the drawings is turned over, then, the elements or features described as "under" or "beneath" or "beneath" the other elements will be oriented "above" the other elements or features. Thus, the exemplary terms "under" and "under" may include both the above and below orientations. The device may be oriented otherwise (rotated 90 degrees or in other orientations) and the spatial descriptors used herein are interpreted accordingly.

[0088] The purpose of the terms used herein is only to describe specific embodiments and is not intended to limit the present application. When used herein, the singular forms "a", "an", and "the" are 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, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0089] In order to fully understand the present application, detailed steps and detailed structures will be presented in the following description to illustrate the technical solution of the present application. The preferred embodiments of the present application are described in detail below. However, in addition to these detailed descriptions, the present application may also have other implementation methods.

[0090] Figure 1 The cross-sectional structure diagram of the MEMS device provided in the embodiment of the present application is shown in the figure. The MEMS device includes:

[0091] The substrate 100 includes a first surface 101 and a second surface 102 opposite to each other;

[0092] The first diaphragm 210 is located on the first surface 101 side. The first diaphragm 210 includes a first movable area 211 and a first fixed area 212 located on the periphery of the first movable area 211;

[0093] The first protruding structure 310 is located on a side of the first diaphragm 210 away from the substrate 100 and connected to the first movable region 211. The cross-sectional area of ​​the first protruding structure 310 decreases along a first direction, where the cross-section is a plane parallel to the first surface 101. The first direction is from the second surface 102 to the first surface 101. The material of the first protruding structure 310 includes SiN. The Si content in the first protruding structure 310 decreases and the N content increases along the first direction.

[0094] The first supporting structure 611 is located on a side of the first diaphragm 210 away from the substrate 100 and connected to the first fixing region 212 ;

[0095] The back plate 700 is located on a side of the first support structure 611 away from the first diaphragm 210 ; wherein, in the first direction, the projection of the first protruding structure 310 falls within the projection range of the back plate 700 .

[0096] Thus, the reliability of the MEMS device is improved. Specifically, a first protruding structure 310 is formed on the first movable area 211 of the first diaphragm 210, which substantially increases the thickness of the first diaphragm 210, thereby increasing the strength of the first diaphragm 210 and reducing the risk of permanent deformation due to insufficient diaphragm strength; the first protruding structure 310 is located in the first movable area 211 of the first diaphragm 210 and the projection of the first protruding structure 310 falls within the projection range of the back plate 700. When the first diaphragm 210 moves toward the back plate 700, the first protruding structure 310 replaces the first diaphragm 210 and contacts the back plate 700. The first protruding structure 310 can serve as an anti-adhesion structure to avoid The diaphragm is prevented from adhering to the back plate 700 during vibration, thereby reducing the risk of device failure; moreover, the cross-sectional area of ​​the first protruding structure 310 decreases along the first direction, while ensuring the reinforcing effect of the first protruding structure 310 on the strength of the first diaphragm 210, the contact area between the first protruding structure 310 and the back plate 700 is reduced, thereby shortening the contact time between the first protruding structure 310 and the back plate 700. After the first protruding structure 310 contacts the back plate 700, the first diaphragm 210 can bounce away from the back plate 700 more quickly, thereby reducing the risk of permanent deformation of the first diaphragm 210 due to maintaining the contact state for a long time. In addition, since the material of the first protruding structure 310 includes SiN, and the Si content in the first protruding structure 310 decreases and the N content increases along the first direction, the portion of the material layer used to form the first protruding structure 310 that is farther away from the first diaphragm 210 is easier to be etched and removed. Therefore, during the preparation process, the amount of etching of the material layer by the etchant increases along the first direction, and the remaining material layer constitutes the first protruding structure 310 whose cross-sectional area decreases along the first direction. The first protruding structure 310 has higher dimensional accuracy, better contour consistency, higher strength, and simpler process.

[0097] In some embodiments, the MEMS device is a MEMS microphone. Of course, this application does not exclude that the MEMS device is any other suitable device known to those skilled in the art, such as a pressure sensor.

[0098] The substrate 100 may be a silicon substrate, or may include Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, InGaAs or other compound semiconductors, or may include a multilayer structure composed of these semiconductors, etc. Alternatively, the substrate 100 may be silicon on insulator (SOI), stacked silicon on insulator (SSOI), stacked silicon germanium on insulator (S-SiGeOI), silicon germanium on insulator (SiGeOI), and germanium on insulator (GeOI), etc. Those skilled in the art may make a selection as needed, and this embodiment does not limit this.

[0099] Please refer to Figure 1A back cavity 103 is formed in the substrate 100 and penetrates the substrate 100 along a first direction.

[0100] In some embodiments, the MEMS device further includes: a third support structure 641, located on the side of the first diaphragm 210 facing the substrate 100 and connected to the first fixed region 212; and a third cavity 603, with the third support structure 641 surrounding the third cavity 603. Thus, the third support structure 641 separates the first diaphragm 210 from the substrate 100, and the third cavity 603 provides space for the first diaphragm 210 to move along a second direction, which is the direction from the first surface 101 to the second surface 102.

[0101] The material of the third support structure 641 may include silicon oxide. Of course, the present application does not exclude the possibility that the material of the third support structure 641 is other materials, and this embodiment does not limit this.

[0102] In some embodiments, a first air hole 213 is formed in the first diaphragm 210 and penetrates the first diaphragm 210 along a first direction.

[0103] The material of the first diaphragm 210 may include polysilicon. Of course, the present application does not exclude the possibility that the material of the first diaphragm 210 is other materials, and this embodiment does not limit this.

[0104] It can be understood that the first movable area 211 of the first diaphragm 210 is the part of the first diaphragm 210 that can move along the first direction or the second direction, and the first fixed area 212 of the first diaphragm 210 is connected to the first supporting structure 611 and the third supporting structure 641, and is used to fix the first diaphragm 210, and is the non-movable part of the first diaphragm 210.

[0105] In some embodiments, the Si content in the first protruding structure 310 decreases linearly and the N content increases linearly along the first direction. The longitudinal cross-section of the first protruding structure 310 is a trapezoid, and the longitudinal cross-section is a plane parallel to the first direction. Optionally, the angle between the side wall of the first protruding structure 310 and the bottom end of the first protruding structure 310 is in the range of 30° to 60°, and the bottom end of the first protruding structure 310 is the end of the first protruding structure 310 facing the first diaphragm 210. Controlling the inclination angle of the side wall of the first protruding structure 310 within this range is more conducive to stress conduction. Of course, this application does not exclude the situation where the angle between the side wall of the first protruding structure 310 and the bottom end of the first protruding structure 310 is greater than 0° and less than 30°.

[0106] In some embodiments, the Si content in the first convex structure 310 decreases gradually and the N content increases gradually along the first direction. Optionally, the first convex structure 310 includes a plurality of first material layer sub-layers stacked along the first direction, wherein the Si content in the first material layer sub-layers decreases layer by layer and the N content increases layer by layer along the first direction, and the Si content and N content in a single first material layer sub-layer remain unchanged. The longitudinal cross-section of the first convex structure 310 is a step-shaped shape. As a specific example, please refer to Figure 2 The first convex structure 310 includes a first material layer, a first sublayer 301, a first material layer, a second sublayer 302, and a first material layer, a third sublayer 303, which are sequentially stacked along a first direction. The Si content in the first sublayer 301 of the first material layer is X1 and the N content is Y1. The Si content in the second sublayer 302 of the first material layer is X2 and the N content is Y2. The Si content in the third sublayer 303 of the first material layer is X3 and the N content is Y3. From the first sublayer 301 of the first material layer to the third sublayer 303 of the first material layer, the Si content decreases and the N content increases. Specifically, X1>X2>X3, and Y1 <Y2<Y3。

[0107] Optionally, the number of the first material layer sub-layers is greater than or equal to 3.

[0108] The material of the first support structure 611 may include silicon oxide. Of course, the present application does not exclude the possibility that the material of the first support structure 611 is other materials, and this embodiment does not limit this.

[0109] like Figure 1 As shown, the MEMS device may further include a first cavity 601 surrounded by a first support structure 611. The first cavity 601 provides space for the first diaphragm 210 to move along a first direction. The first cavity 601 is connected to the third cavity 603 through the first air hole 213.

[0110] Optionally, the MEMS device also includes a first reinforcement structure 410, which is located on the side of the first diaphragm 210 away from the substrate 100, and the cross-sectional area of ​​the first reinforcement structure 410 decreases along the first direction. The first reinforcement structure 410 and the first protruding structure 310 are formed in the same process based on the same material layer; a portion of the first reinforcement structure 410 is embedded in the first support structure 611.

[0111] Therefore, by setting the first reinforcement structure 410 on the first diaphragm 210, the thickness of the first diaphragm 210 is further increased and the strength of the first diaphragm 210 is strengthened; by setting the cross-sectional area of ​​the first reinforcement structure 410 to decrease along the first direction, stress concentration can be reduced and reliability can be improved; part of the first reinforcement structure 410 is embedded in the first support structure 611, so that the first reinforcement structure 410 can also serve as an anchoring structure to strengthen the connection strength between the second diaphragm 220 and the second support structure 621, which is beneficial to enhance the reliability of the device.

[0112] The first reinforcement structure 410 and the first protrusion structure 310 are formed in the same process based on the same material layer, saving process and cost. Figure 2 The description is not repeated here.

[0113] Optionally, within the same plane, the cross-sectional area of ​​the first reinforcement structure 410 is greater than the cross-sectional area of ​​the first protruding structure 310. It is understandable that the first protruding structure 310 is located in the first movable region 211 and may come into contact with the back plate 700 when the first diaphragm 210 moves. The relatively small size of the first protruding structure 310 can reduce the contact time and reduce the risk of permanent deformation of the first diaphragm 210. The first reinforcement structure 410 is located in the first fixed region 212. Setting the size of the first reinforcement structure 410 relatively large is more conducive to strengthening the thickness and strength of the first diaphragm 210. Therefore, under the synergistic effect of the two, the strength and anti-adhesion effect of the first diaphragm 210 are simultaneously strengthened, which is conducive to improving the reliability of the device.

[0114] In some embodiments, the backplate 700 may include a first backplate insulating layer 710, a backplate conductive layer 720, and a second backplate insulating layer 730 stacked sequentially along a first direction. The first and second backplate insulating layers 710 and 730 may be made of silicon nitride; the backplate conductive layer 720 may be made of polycrystalline silicon. Of course, the present invention does not exclude the possibility that the first backplate insulating layer 710, the backplate conductive layer 720, and the second backplate insulating layer 730 may be made of other materials; furthermore, the first and second backplate insulating layers 710 and 730 may also be made of different materials.

[0115] In some embodiments, the MEMS device further comprises:

[0116] The second diaphragm 220 is located on a side of the back plate 700 away from the first diaphragm 210;

[0117] The second supporting structure 621 is located between the back plate 700 and the second diaphragm 220 so that the second diaphragm 220 and the back plate 700 are spaced apart.

[0118] A through opening 701 passes through the back plate 700 along a first direction;

[0119] The support column 500 includes a first support portion 510 connected to the first diaphragm 210, a third support portion 530 connected to the second diaphragm 220, and a second support portion 520 connected between the first support portion 510 and the third support portion 530 along the first direction. The cross-sectional area of ​​the first support portion 510 decreases along the first direction; the cross-sectional area of ​​the third support portion 530 increases along the first direction. The second support portion 520 passes through the through opening 701. The cross-sectional areas of the first support portion 510 and the third support portion 530 are both greater than the cross-sectional area of ​​the second support portion 520.

[0120] The first support portion 510 and the first protruding structure 310 are formed in the same process based on the same material layer;

[0121] The material of the third support portion 530 includes SiN, and the Si content in the third support portion 530 increases and the N content decreases along the first direction.

[0122] It is understood that a MEMS device having a first diaphragm 210 and a second diaphragm 220 can be referred to as a "dual-diaphragm MEMS device." A support column 500 is typically disposed between the two diaphragms of a dual-diaphragm MEMS device. Common support columns 500 in the art are vertical structures, specifically, having a rectangular longitudinal cross-section. When the MEMS device is operating, the first and second diaphragms 210 and 220 vibrate. The vertical support columns 500 have poor stress conduction and are prone to stress concentration, affecting the reliability of the MEMS device. In some related technologies, a through hole with a greater width at both ends than in the middle is formed by etching a first sacrificial layer for forming the first support structure 611 and a second sacrificial layer for forming the second support structure 621. The through hole is then filled with material to form the support column 500. While the larger widths at both ends of the support column 500 improve the support and stress conduction performance of the support column 500, voids may appear within the filled support column 500, resulting in poor structural accuracy and strength, making it difficult to effectively improve device reliability.

[0123] In the embodiment of the present application, the Si content in the first support portion 510 is controlled to decrease and the N content is increased, and the Si content in the third support portion 530 is controlled to increase and the N content is decreased along the first direction, and the wet etching rate is changed. In actual preparation, the two ends of the support column 500, namely the first support portion 510 and the third support portion 530, can be directly obtained by etching the material layer. The structural accuracy of the support column 500 is better and the supporting strength is higher. Moreover, the cross-sectional area of ​​the first support portion 510 and the cross-sectional area of ​​the third support portion 530 are both larger than the cross-sectional area of ​​the second support portion 520. The cross-sectional area of ​​the first support portion 510 decreases along the first direction, and the cross-sectional area of ​​the third support portion 530 increases along the first direction. The contact surface area between the first support portion 510 and the first diaphragm 210 is larger, and the contact surface area between the third support portion 530 and the second diaphragm 220 is larger, so the stress conduction effect is better, which is more conducive to avoiding stress concentration and improving the reliability of the device.

[0124] The first support portion 510 and the first protruding structure 310 are formed in the same process based on the same material layer. This can save process and cost. It should be noted that, regarding the specific structure of the first support portion 510, please refer to the first protruding structure 310 and Figure 2 The description is not repeated here.

[0125] In some embodiments, the Si content in the third support portion 530 increases linearly and the N content decreases linearly along the first direction. The longitudinal cross-section of the third support portion 530 is trapezoidal. Optionally, the angle between the sidewall of the third support portion 530 and the top of the third support portion 530 ranges from 30° to 60°, where the top of the third support portion 530 is the end of the third support portion 530 facing the second diaphragm 220. Of course, this application does not exclude the possibility that the angle between the sidewall of the third support portion 530 and the top of the third support portion 530 is greater than 0° and less than 30°.

[0126] In some embodiments, the Si content in the third support portion 530 increases gradually and the N content decreases gradually along the first direction. Optionally, the third support portion 530 includes a plurality of third material layer sublayers stacked along the first direction, wherein the Si content in the third material layer sublayers increases layer by layer and the N content decreases layer by layer along the first direction, and the Si content and N content in a single third material layer sublayer remain unchanged. The longitudinal cross-section of the third support portion 530 is a step-shaped shape. As a specific example, please refer to Figure 3The third supporting portion 530 includes a third material layer, a third sublayer 803, a third material layer, a second sublayer 802, and a third material layer, a first sublayer 801, which are sequentially stacked along the first direction. The Si content in the first sublayer 801 of the third material layer is A1 and the N content is B1. The Si content in the second sublayer 802 of the third material layer is A2 and the N content is B2. The Si content in the third sublayer 803 of the third material layer is A3 and the N content is B3. From the third sublayer 803 of the third material layer to the first sublayer 801 of the third material layer, the Si content increases and the N content decreases. Specifically, A1>A2>A3, and B1 <B2<B3。

[0127] Optionally, the number of the third material layer sub-layers is greater than or equal to 3.

[0128] Optionally, the first support portion 510 and the third support portion 530 are symmetrically arranged along the plane where the center of the second support portion 520 is located, and the plane where the center of the second support portion 520 is located is parallel to the plane where the first surface 101 is located. As a result, the two ends of the support column 500 are symmetrically arranged, the support column 500 has a better stress conduction effect and a higher support effect, which is conducive to improving the reliability of the device. Specifically, in the first direction, the projection of the cross section at the first position in the first support portion 510 completely overlaps with the projection of the cross section at the second position in the third support portion 530, and the distance between the first position and the first diaphragm is equal to the distance between the second position and the second diaphragm. The thickness of the first support portion 510 is the same as the thickness of the third support portion 530.

[0129] In some embodiments, the Si content in the first support portion 510 decreases linearly and the N content increases linearly along the first direction, while the Si content in the third support portion 530 increases linearly and the N content decreases linearly. The Si content and N content at a first position in the first support portion 510 are the same as the Si content and N content at a second position in the third support portion 530. This facilitates symmetrical arrangement of the first support portion 510 and the third support portion 530.

[0130] In some embodiments, the Si content in the first support portion 510 decreases gradually and the N content increases gradually along the first direction, and the Si content in the third support portion 530 increases gradually and the N content decreases gradually; the Si content and N content at the first position in the first support portion 510 are correspondingly the same as the Si content and N content at the second position in the third support portion 530. The first supporting portion 510 may include a plurality of first material layer sublayers stacked along the first direction, wherein the Si content of each first material layer sublayer decreases layer by layer and the N content increases layer by layer along the first direction, and the Si content and N content in a single first material layer sublayer remain unchanged; the third supporting portion 530 includes a plurality of third material layer sublayers stacked along the first direction, wherein the Si content of each third material layer sublayer increases layer by layer and the N content decreases layer by layer along the first direction, and the Si content and N content in a single third material layer sublayer remain unchanged; the first material layer sublayers are arranged in sequence starting from the first sublayer of the first material layer along the first direction, and the first sublayer of the first material layer is a layer close to the first diaphragm 210; the third material layer sublayers are arranged in sequence starting from the first sublayer of the third material layer along the second direction, and the first sublayer of the third material layer is a layer close to the second diaphragm 220; the Si content and N content in the first material layer sublayer and the third material layer sublayer with the same serial number are the same; the thickness of the first material layer sublayer and the third material layer sublayer with the same serial number is the same. The number of first material layer sub-layers in the first support portion 510 is the same as the number of third material layer sub-layers in the third support portion 530. In the first direction, the projections of the first material layer sub-layers and the third material layer sub-layers with the same sequence number completely overlap. This facilitates the symmetrical arrangement of the first support portion 510 and the third support portion 530.

[0131] As a specific example, see Figure 2 and Figure 3The first supporting portion 510 includes a first sublayer 301 of a first material layer, a second sublayer 302 of a first material layer, and a third sublayer 303 of a first material layer stacked along a first direction. The third supporting portion 530 includes a third sublayer 803 of a third material layer, a second sublayer 802 of a third material layer, and a first sublayer 801 of a third material layer stacked along the first direction. The Si content decreases and the N content increases from the first sublayer 301 of the first material layer to the third sublayer 303 of the first material layer, and from the first sublayer 801 of the third material layer to the third sublayer 803 of the third material layer. The Si content and N content of the first sublayer 301 of the first material layer are correspondingly equal to the Si content and N content of the first sublayer 801 of the third material layer. The Si content and N content of the second sublayer 302 of the first material layer are correspondingly equal to the Si content and N content of the second sublayer 802 of the third material layer. The Si content and N content of the third sublayer 303 of the first material layer are correspondingly equal to the Si content and N content of the third sublayer 803 of the third material layer. The thickness of the first sublayer 301 of the first material layer is equal to the thickness of the first sublayer 801 of the third material layer, the thickness of the second sublayer 302 of the first material layer is equal to the thickness of the second sublayer 802 of the third material layer, and the thickness of the third sublayer 303 of the first material layer is equal to the thickness of the third sublayer 803 of the third material layer. In the first direction, the projection of the first sublayer 301 of the first material layer completely overlaps with the projection of the first sublayer 801 of the third material layer, the projection of the second sublayer 302 of the first material layer completely overlaps with the projection of the second sublayer 802 of the third material layer, and the projection of the third sublayer 303 of the first material layer completely overlaps with the projection of the third sublayer 803 of the third material layer.

[0132] The material of the second support structure 621 may include silicon oxide. Of course, the present application does not exclude the possibility that the material of the second support structure 621 is other materials, and this embodiment does not limit this.

[0133] Please refer to Figure 1 The MEMS device further includes a second cavity 602 surrounded by a second support structure 621. The second cavity 602 provides space for the second diaphragm 220 to move along the second direction. The second cavity 602 is connected to the first cavity 601 through a through port 701.

[0134] In some embodiments, a second air hole 223 is formed in the second diaphragm 220 and penetrates the second diaphragm 220 along the first direction.

[0135] The material of the second diaphragm 220 may include polysilicon. Of course, the present application does not exclude the possibility that the material of the second diaphragm 220 is other materials, and this embodiment does not limit this.

[0136] Optionally, in the first direction, the projection of the first air hole 213 falls within the projection range of the through-opening 701 . Further, the projection of the first air hole 213 is located at the center of the projection of the through-opening 701 .

[0137] Optionally, in the first direction, the projection of the second air hole 223 falls within the projection range of the through-opening 701 . Further, the projection of the second air hole 223 is located at the center of the projection of the through-opening 701 .

[0138] Optionally, the second diaphragm 220 includes a second movable area 221 and a second fixed area 222 located on the periphery of the second movable area 221; the MEMS device also includes: a second protruding structure 810, located on the side of the second diaphragm 220 facing the back plate 700 and connected to the second movable area 221, and the cross-sectional area of ​​the second protruding structure 810 increases along the first direction; wherein, in the first direction, the projection of the second protruding structure 810 falls within the projection range of the back plate 700; the second protruding structure 810 and the third support portion 530 are formed in the same process based on the same material layer.

[0139] It is understandable that the second protruding structure 810 and the third supporting portion 530 are formed in the same process based on the same material layer, which can save process and cost. Figure 3 The description is not repeated here.

[0140] Thus, the reliability of the MEMS device is improved. Specifically, a second protruding structure 810 is formed on the second movable area 221 of the second diaphragm 220, which substantially increases the thickness of the second movable area 221 of the second diaphragm 220, thereby increasing the strength of the second diaphragm 220 and reducing the risk of permanent deformation due to insufficient diaphragm strength; the projection of the second protruding structure 810 falls within the projection range of the back plate 700. When the second diaphragm 220 moves toward the back plate 700, the second protruding structure 810 replaces the second diaphragm 220 and contacts the back plate 700. The second protruding structure 810 can serve as an anti-adhesion structure to prevent the diaphragm from adhering to the back plate 700 when vibrating. On the back pole plate 700, the risk of device failure is reduced; and the cross-sectional area of ​​the second protruding structure 810 increases along the first direction, while ensuring the reinforcing effect of the second protruding structure 810 on the strength of the second diaphragm 220, the contact area between the second protruding structure 810 and the back pole plate 700 is reduced, thereby shortening the contact time between the second protruding structure 810 and the back pole plate 700. After the second protruding structure 810 contacts the back pole plate 700, the second diaphragm 220 can bounce away from the back pole plate 700 more quickly, reducing the risk of permanent deformation of the second diaphragm 220 due to maintaining the contact state for a long time.

[0141] It can be understood that during actual preparation, the Si content of the material layer can be controlled to increase and the N content can be controlled to decrease along the first direction, so that the wet etching rate of the material layer decreases along the first direction. In this way, when the wet etching process is performed, the amount of etching of the material layer by the etchant increases, and the remaining material layer constitutes a second protruding structure 810 with an increasing cross-sectional area along the first direction. The second protruding structure 810 has higher dimensional accuracy, higher structural strength, and a simpler process.

[0142] It can be understood that the second movable area 221 of the second diaphragm 220 is the part of the second diaphragm 220 that can move along the first direction or the second direction, and the second fixed area 222 of the second diaphragm 220 is connected to the second supporting structure 621, which is used to fix the second diaphragm 220 and is the immovable part of the second diaphragm 220.

[0143] Optionally, the MEMS device also includes: a second reinforcement structure 910, located on the side of the second diaphragm 220 facing the back plate 700, and the cross-sectional area of ​​the second reinforcement structure 910 increases along the first direction; the second reinforcement structure 910 and the third support part 530 are formed in the same process based on the same material layer; and a portion of the second reinforcement structure 910 is embedded in the second support structure 621.

[0144] Thus, by providing the second support structure 621 on the second diaphragm 220, the thickness of the second diaphragm 220 is further increased, and the strength of the second diaphragm 220 is strengthened; the second reinforcement structure 910 and the third support portion 530 are formed in the same process based on the same material layer, saving process steps and costs. It should be noted that the specific structure of the second reinforcement structure 910 can be specifically referred to the third support portion 530 and Figure 3 The description is not repeated here.

[0145] Optionally, within the same plane, the cross-sectional area of ​​the second reinforcement structure 910 is greater than the cross-sectional area of ​​the second protruding structure 810. It is understandable that the second protruding structure 810 is located in the second movable region 221 and contacts the back plate 700 when the second diaphragm 220 moves. The relatively small size of the second protruding structure 810 can reduce the contact area and time, thereby reducing the risk of permanent deformation of the second diaphragm 220. The second reinforcement structure 910 is located in the second fixed region 222. Setting the size of the second reinforcement structure 910 relatively large is more conducive to strengthening the thickness and strength of the second diaphragm 220. Thus, under the synergistic effect of the two, the strength and anti-adhesion effect of the second diaphragm 220 are simultaneously strengthened, further improving the reliability of the device.

[0146] The present invention also provides a method for preparing a MEMS device. Figure 4 , the preparation method comprises:

[0147] Step S101: providing a substrate, the substrate comprising a first surface and a second surface opposite to each other;

[0148] Step S102: forming a first diaphragm on the first surface side, the first diaphragm including a first movable area and a fixed area located outside the first movable area;

[0149] Step S103: forming a first semiconductor material layer on the first diaphragm, wherein the material of the first semiconductor material layer includes SiN, and the Si content of the first semiconductor material layer decreases and the N content increases along a first direction, wherein the first direction is from the second surface to the first surface;

[0150] Step S104: performing a first wet etching process on the first semiconductor material layer to form a first protruding structure on the first movable area, wherein the cross-sectional area of ​​the first protruding structure decreases along the first direction, and the cross-sectional area is parallel to the plane of the first surface;

[0151] Step S105: forming a first sacrificial layer covering the first diaphragm and the first protruding structure;

[0152] Step S106: forming a back plate on the first sacrificial layer; wherein, in the first direction, the projection of the first protruding structure falls within the projection range of the back plate.

[0153] Thus, by forming a first protruding structure on the first movable area of ​​the first diaphragm, the thickness and strength of the movable area of ​​the first diaphragm are increased, and the risk of permanent deformation due to insufficient strength of the diaphragm is reduced; the projection of the first protruding structure falls within the projection range of the back plate, and the first protruding structure can also serve as an anti-adhesion structure to prevent the diaphragm from adhering to the back plate when vibrating, thereby reducing the risk of device failure; and the cross-sectional area of ​​the first protruding structure decreases along the first direction, while ensuring the reinforcing effect of the first protruding structure on the strength of the first diaphragm, the contact area between the first protruding structure and the back plate is reduced, thereby shortening the contact area between the first protruding structure and the back plate. The contact time is shorter than that of the first protruding structure. After the first protruding structure contacts the back plate, the first diaphragm can bounce away from the back plate more quickly, thereby reducing the risk of permanent deformation of the first diaphragm due to prolonged contact. Specifically, by controlling the Si content in the first semiconductor material layer to decrease and the N content to increase along the first direction, the part of the first semiconductor material layer farther away from the first diaphragm is easier to be etched away, thereby directly etching the first protruding structure with a reduced cross-sectional area along the first direction, so that the first protruding structure has higher dimensional accuracy, better contour consistency, and higher strength. Ultimately, the reliability of the prepared MEMS device is improved.

[0154] First, please refer to Figure 5 , perform step S101, provide a substrate 100, the substrate 100 includes a first surface 101 and a second surface 102 opposite to each other.

[0155] Next, the preparation method may further include: forming a fourth sacrificial layer 640 on the first surface 101 side.

[0156] Next, step S102 is performed to form a first diaphragm 210 on the first surface 101 . The first diaphragm 210 includes a first movable region 211 and a first fixed region 212 located at the periphery of the first movable region 211 .

[0157] In some embodiments, the manufacturing method may further include: forming a first air hole 213 penetrating the first diaphragm 210 along a first direction.

[0158] Next, step S103 is performed to form a first semiconductor material layer 300 on the first diaphragm 210. The material of the first semiconductor material layer 300 includes SiN. The Si content in the first semiconductor material layer 300 decreases and the N content increases along the first direction. Thus, by controlling the Si and N contents in the first semiconductor material layer 300, the wet etching rate of the first semiconductor material layer 300 can be controlled. Subsequently, when the wet etching process is performed, a structure of a desired shape can be obtained.

[0159] During actual preparation, the Si content and the N content in the first semiconductor material layer 300 can be controlled by adjusting the amount of Si source gas and the amount of N source gas introduced.

[0160] In some embodiments, the Si content in the first semiconductor material layer 300 decreases linearly and the N content increases linearly along the first direction.

[0161] In some embodiments, the Si content in the first semiconductor material layer 300 decreases gradually and the N content increases gradually along the first direction. Optionally, the first semiconductor material layer 300 includes a plurality of first material layer sublayers stacked along the first direction, wherein the Si content in the first material layer sublayers decreases layer by layer and the N content increases layer by layer along the first direction, and the Si content and N content in a single first material layer sublayer remain unchanged. As a specific example, please refer to Figure 6 The first semiconductor material layer 300 includes a first material layer first sublayer 301, a first material layer second sublayer 302, and a first material layer third sublayer 303 stacked in sequence along a first direction. The Si content in the first material layer first sublayer 301 is X1 and the N content is Y1. The Si content in the first material layer second sublayer 302 is X2 and the N content is Y2. The Si content in the first material layer third sublayer 303 is X3 and the N content is Y3. From the first material layer first sublayer 301 to the first material layer third sublayer 303, the Si content decreases and the N content increases. Specifically, X1>X2>X3, and Y1 <Y2<Y3。

[0162] Optionally, the number of the first material layer sub-layers is greater than or equal to 3.

[0163] Next, please refer to Figure 7 , step S104 is executed to perform a first wet etching process on the first semiconductor material layer 300 to form a first protruding structure 310 on the first movable region 211. The cross-sectional area of ​​the first protruding structure 310 decreases along the first direction. Thus, by forming the first protruding structure 310 on the first movable region 211 of the first diaphragm 210, the thickness of the movable region of the first diaphragm 210 is increased, reducing the risk of permanent deformation due to insufficient diaphragm strength.

[0164] It is understandable that the higher the Si content and the lower the N content in the SiN layer, the easier it is to be etched away. Therefore, along the first direction, the Si content in the first semiconductor material layer 300 decreases and the N content increases. During the first wet etching process, the amount of etching of the first semiconductor material layer 300 by the etchant decreases along the first direction, and the remaining first semiconductor material layer 300 forms a first protrusion structure 310 whose cross-sectional area decreases along the first direction.

[0165] The etchant may include hydrofluoric acid or phosphoric acid.

[0166] In some embodiments, the Si content in the first semiconductor material layer 300 decreases linearly and the N content increases linearly along the first direction; the longitudinal cross-section of the first protrusion structure 310 is trapezoidal. Optionally, the angle between the sidewall of the first protrusion structure 310 and the bottom of the first protrusion structure 310 ranges from 30° to 60°, with the bottom of the first protrusion structure 310 being the end of the first protrusion structure 310 facing the first diaphragm 210. Of course, this application does not exclude the possibility that the angle between the sidewall of the first protrusion structure 310 and the bottom of the first protrusion structure 310 is greater than 0° and less than 30°.

[0167] In some embodiments, please refer to Figure 2 and Figure 6 The first semiconductor material layer 300 includes a plurality of first material layer sublayers stacked along a first direction, wherein the Si content in the first material layer sublayers decreases layer by layer and the N content increases layer by layer along the first direction, and the Si content and N content in a single first material layer sublayer remain unchanged; the longitudinal cross-sectional shape of the first protruding structure 310 is a step shape.

[0168] Optionally, refer to Figure 7 When executing step S104, a first wet etching process is performed on the first semiconductor material layer 300 to form a first reinforcement structure 410. The first reinforcement structure 410 is located on the side of the first diaphragm 210 away from the substrate 100 and is connected to the first fixed area 212. The cross-sectional area of ​​the first reinforcement structure 410 decreases along the first direction. Figure 1 In subsequent steps, specifically after forming the back plate 700 on the first sacrificial layer 610, the above method may further include: removing part of the first sacrificial layer 610, and forming the remaining first sacrificial layer 610 into a first support structure 611 located on the first fixed area 212, and partially embedding the first reinforcement structure 410 into the first support structure 611.

[0169] Thus, the first reinforcement structure 410 and the first protrusion structure 310 are formed in the same process based on the same material layer, saving processes and costs. Figure 2 The description is not repeated here.

[0170] Optionally, in the same plane, the cross-sectional area of ​​the first reinforcement structure 410 is greater than the cross-sectional area of ​​the first protruding structure 310 .

[0171] It can be understood that the first protruding structure 310 is located in the first movable area 211, and when the first diaphragm 210 moves, it will contact the back plate 700. The size of the first protruding structure 310 is relatively small, which can reduce the contact time and reduce the risk of permanent deformation of the first diaphragm 210; the first reinforcing structure 410 is located in the first fixed area 212, and the size of the first reinforcing structure 410 is set to be relatively large, which is more conducive to strengthening the thickness and strength of the first diaphragm 210; thus, under the synergistic effect of the two, the strength and anti-adhesion effect of the first diaphragm 210 are simultaneously enhanced, which is conducive to improving the reliability of the device.

[0172] Next, please refer to Figure 8 , executing step S105 to form a first sacrificial layer 610 covering the first diaphragm 210 and the first protruding structure 310 .

[0173] The material of the first sacrificial layer 610 may include silicon oxide. Of course, the present application does not exclude the possibility that the material of the first sacrificial layer 610 is other materials, and this embodiment does not limit this.

[0174] Next, step S106 is performed to form a back plate 700 on the first sacrificial layer 610; wherein, in the first direction, the projection of the first protruding structure 310 falls within the projection range of the back plate 700. Thus, the first protruding structure 310 can also serve as an anti-adhesion structure to prevent the diaphragm from adhering to the back plate 700 during vibration, thereby reducing the risk of device failure; and the cross-sectional area of ​​the first protruding structure 310 decreases along the first direction. While ensuring the first protruding structure 310 strengthens the strength of the first diaphragm 210, it also reduces the contact area between the first protruding structure 310 and the back plate 700, thereby shortening the contact time between the first protruding structure 310 and the back plate 700. After the first protruding structure 310 contacts the back plate 700, the first diaphragm 210 can bounce away from the back plate 700 more quickly, reducing the risk of permanent deformation of the first diaphragm 210 due to prolonged contact.

[0175] Optionally, refer to Figure 1 、 Figures 7 to 14 When performing step S104, a first wet etching process is performed on the first semiconductor material layer 300 to form a first support portion 510. The cross-sectional area of ​​the first support portion 510 decreases along the first direction;

[0176] A through opening 701 is formed in the back plate 700 and passes through the back plate 700 along a first direction;

[0177] After executing step S106 and forming the back plate 700 on the first sacrificial layer 610 , the method further includes:

[0178] forming a second sacrificial layer 620 covering the back plate 700 and filling the through opening 701;

[0179] A through hole 604 is formed that penetrates the second sacrificial layer 620 and the first sacrificial layer 610 and passes through the through opening 701 , and the through hole 604 exposes the first support portion 510 ;

[0180] Filling the through hole 604 with a second semiconductor material layer to form a second supporting portion 520 ;

[0181] forming a third semiconductor material layer 800 covering the second sacrificial layer 620 and the second support portion 520 , wherein the third semiconductor material layer 800 includes SiN, and the Si content in the third semiconductor material layer 800 increases and the N content decreases along the first direction;

[0182] A second wet etching process is performed on the third semiconductor material layer 800 to form a third support portion 530, wherein the cross-sectional area of ​​the third support portion 530 increases along the first direction; the first support portion 510, the second support portion 520, and the third support portion 530 are sequentially connected to form a support column 500, wherein the cross-sectional area of ​​the first support portion 510 and the cross-sectional area of ​​the third support portion 530 are both greater than the cross-sectional area of ​​the second support portion 520;

[0183] The second diaphragm 220 is formed on the third supporting portion 530 .

[0184] In the embodiment of the present application, the Si content in the first semiconductor material layer 300 is controlled to decrease and the N content is increased along the first direction, and the Si content in the third semiconductor material layer 800 is controlled to increase and the N content is controlled to decrease, thereby changing the wet etching rate. As a result, the two ends of the support column 500, namely the first support part 510 and the third support part 530, can be directly obtained by etching the material layer, and the cross-sectional area of ​​the first support part 510 and the cross-sectional area of ​​the third support part 530 are both larger than the cross-sectional area of ​​the second support part 520. The structural accuracy of the support column 500 is better and the supporting strength is higher. The cross-sectional area of ​​the first support part 510 decreases along the first direction, and the cross-sectional area of ​​the third support part 530 increases along the first direction. The contact surface area between the first support part 510 and the first diaphragm 210 is larger, and the contact surface area between the third support part 530 and the second diaphragm 220 is larger, resulting in a better stress conduction effect and more conducive to avoiding stress concentration. Therefore, the reliability of the MEMS device is improved.

[0185] In some embodiments, the Si content in the third semiconductor material layer 800 increases linearly and the N content decreases linearly along the first direction. The longitudinal cross-section of the third support portion 530 is a trapezoid. Optionally, the angle between the sidewall of the third support portion 530 and the top of the third support portion 530 ranges from 30° to 60°, and the top of the third support portion 530 is the end of the third support portion 530 facing the second diaphragm 220. Of course, this application does not exclude the possibility that the angle between the sidewall of the third support portion 530 and the top of the third support portion 530 is greater than 0° and less than 30°.

[0186] In some embodiments, the Si content in the third semiconductor material layer 800 increases gradually and the N content decreases gradually along the first direction. Optionally, the third semiconductor material layer 800 may include a plurality of third material layer sublayers stacked along the first direction, wherein the Si content in the third material layer sublayers increases layer by layer and the N content decreases layer by layer along the first direction, and the Si content and N content in a single third material layer sublayer remain unchanged. As a specific example, please refer to Figure 11, the third semiconductor material layer 800 includes a third material layer third sub-layer 803, a third material layer second sub-layer 802, and a third material layer first sub-layer 801 stacked in sequence along the first direction. The Si content in the third material layer first sub-layer 801 is all A1 and the N content is all B1. The Si content in the third material layer second sub-layer 802 is all A2 and the N content is all B2. The Si content in the third material layer third sub-layer 803 is all A3 and the N content is all B3. From the third material layer third sub-layer 803 to the third material layer first sub-layer 801, the Si content increases and the N content decreases. Specifically, A1 > A2 > A3, and B1 < B2 < B3. Please refer to Figure 3 , in the first direction, the cross-sectional shape of the third support portion 530 is stepped.

[0187] Optionally, the number of sub-layers of the third material layer is greater than or equal to 3.

[0188] Optionally, the first support portion 510 and the third support portion 530 are symmetrically arranged along the plane where the center of the second support portion 520 is located. The plane where the center of the second support portion 520 is located is parallel to the plane where the first surface 101 is located. Thus, the two ends of the support column 500 are symmetrically arranged, the stress conduction effect of the support column 500 is better, the support effect is higher, which is beneficial to improving the device reliability. Specifically, in the first direction, the projection of the cross-section at the first position in the first support portion 510 completely overlaps with the projection of the cross-section at the second position in the third support portion 530. The distance between the first position and the first diaphragm is equal to the distance between the second position and the second diaphragm. The thickness of the first support portion 510 is the same as the thickness of the third support portion 530.

[0189] In some embodiments, along the first direction, the Si content in the first semiconductor material layer 300 decreases linearly and the N content increases linearly, and the Si content in the third semiconductor material layer 800 increases linearly and the N content decreases linearly. The Si content and N content at the first position in the first semiconductor material layer 300 correspond to the Si content and N content at the second position in the third semiconductor material layer 800. The thickness of the first semiconductor material layer 300 is the same as the thickness of the third semiconductor material layer 800. Thus, it is beneficial to achieve the symmetrical arrangement of the first support portion 510 and the third support portion 530.

[0190] In some embodiments, the Si content in the first semiconductor material layer 300 decreases gradually and the N content increases gradually along the first direction, and the Si content in the third semiconductor material layer 800 increases gradually and the N content decreases gradually; the Si content and N content at the first position in the first semiconductor material layer 300 are the same as the Si content and N content at the second position in the third semiconductor material layer 800. The first semiconductor material layer 300 may include a plurality of first material layer sublayers stacked along the first direction, wherein the Si content of each first material layer sublayer decreases layer by layer and the N content increases layer by layer along the first direction, and the Si content and N content in a single first material layer sublayer remain unchanged; the third semiconductor material layer 800 includes a plurality of third material layer sublayers stacked along the first direction, wherein the Si content of each third material layer sublayer increases layer by layer and the N content decreases layer by layer along the first direction, and the Si content and N content in a single third material layer sublayer remain unchanged; the first material layer sublayers are arranged in sequence starting from the first sublayer of the first material layer along the first direction, and the first sublayer of the first material layer is a layer close to the first diaphragm 210; the third material layer sublayers are arranged in sequence starting from the first sublayer of the third material layer along the second direction, and the first sublayer of the third material layer is a layer close to the second diaphragm 220; the Si content and N content of the first material layer sublayer and the third material layer sublayer with the same serial number are the same; the thickness of the first material layer sublayer and the third material layer sublayer with the same serial number are the same. The number of first material layer sublayers in the first semiconductor material layer 300 is the same as the number of third material layer sublayers in the third semiconductor material layer 800. This facilitates symmetrical arrangement of the first support portion 510 and the third support portion 530.

[0191] In some embodiments, the process conditions of the first wet etching process are the same as the process conditions of the second wet etching process, thereby facilitating symmetrical arrangement of the first support portion 510 and the third support portion 530 .

[0192] The material of the second sacrificial layer 620 may include silicon oxide. Of course, the present application does not exclude the possibility that the material of the second sacrificial layer 620 is other materials, and this embodiment does not limit this.

[0193] Optionally, refer to Figure 1 The second diaphragm 220 includes a second movable area 221 and a second fixed area 222 located on the periphery of the second movable area 221; a second wet etching process is performed on the third semiconductor material layer 800 to form a second protruding structure 810. The second protruding structure 810 is located on the side of the second diaphragm 220 facing the back plate 700 and is connected to the second movable area 221. The cross-sectional area of ​​the second protruding structure 810 increases along the first direction; wherein, in the first direction, the projection of the second protruding structure 810 falls within the projection range of the back plate 700.

[0194] It is understandable that the second protruding structure 810 and the third supporting portion 530 are formed in the same process based on the same material layer, which can save process and cost. Figure 3 The description is not repeated here.

[0195] A second protruding structure 810 is formed on the second movable area 221 of the second diaphragm 220, which substantially increases the thickness of the second movable area 221 of the second diaphragm 220, thereby increasing the strength of the second diaphragm 220 and reducing the risk of permanent deformation due to insufficient diaphragm strength; the projection of the second protruding structure 810 falls within the projection range of the back pole plate 700, and when the second diaphragm 220 moves toward the back pole plate 700, the second protruding structure 810 replaces the second diaphragm 220 and contacts the back pole plate 700. The second protruding structure 810 can serve as an anti-adhesion structure to prevent the diaphragm from adhering to the back pole plate when vibrating. plate 700, reducing the risk of device failure; and, the cross-sectional area of ​​the second protruding structure 810 increases along the first direction, while ensuring the reinforcing effect of the second protruding structure 810 on the strength of the second diaphragm 220, the contact area between the second protruding structure 810 and the back plate 700 is reduced, thereby shortening the contact time between the second protruding structure 810 and the back plate 700. After the second protruding structure 810 contacts the back plate 700, the second diaphragm 220 can bounce away from the back plate 700 more quickly, reducing the risk of permanent deformation of the second diaphragm 220 due to maintaining the contact state for a long time.

[0196] Optionally, refer to Figure 13 Before forming the second diaphragm 220 on the third support portion 530, the method may further include: forming a third sacrificial layer 630 covering the sidewalls of the third support portion 530 and the second sacrificial layer 620, wherein the top surface of the third sacrificial layer 630 and the top of the third support portion 530 form a flat surface, the top surface of the third sacrificial layer 630 being the surface of the third sacrificial layer 630 away from the second sacrificial layer 620, and the top of the third support portion 530 being the end of the third support portion 530 away from the second sacrificial layer 620; and the second diaphragm 220 covering the third sacrificial layer 630 and the third support portion 530. Thus, by forming the third sacrificial layer 630, the top surface of the third sacrificial layer 630 and the top of the third support portion 530 form a flat surface, allowing the second diaphragm 220 to be fabricated on a flat surface, thereby ensuring the flatness of the second diaphragm 220 and improving the reliability of the MEMS device.

[0197] It can be understood that during actual preparation, a third sacrificial material layer covering the third support part 530 and the second sacrificial layer 620 can be formed first; then a planarization process is performed on the third sacrificial material layer to form a flat plane between the top surface of the third sacrificial layer 630 and the top of the third support part 530.

[0198] The material of the third sacrificial layer 630 may include silicon oxide. Of course, the present application does not exclude the possibility that the material of the third sacrificial layer 630 is other materials, and this embodiment does not limit this.

[0199] In some embodiments, a second wet etching process is performed on the third semiconductor material layer 800 to further form a second reinforcement structure 910, which is located on the side of the second diaphragm 220 facing the back plate 700. The cross-sectional area of ​​the second reinforcement structure 910 increases along the first direction. Figure 1 In the subsequent steps, specifically after the back plate 700 is formed on the first sacrificial layer 610, the above method further includes: removing part of the second sacrificial layer 620 and the third sacrificial layer 630, and the remaining second sacrificial layer 620 and the third sacrificial layer 630 are formed into a second support structure 621 located on the second fixed area 222, and part of the second reinforcement structure 910 is embedded in the second support structure 621. Thus, by providing the second support structure 621 on the second diaphragm 220, the thickness of the second diaphragm 220 is further increased, and the strength of the second diaphragm 220 is strengthened; the second reinforcement structure 910 and the third support part 530 are formed in the same process based on the same material layer, saving process and cost. It should be noted that, with regard to the specific structure of the second reinforcement structure 910, specific reference can be made to the third support part 530 and Figure 3 The description is not repeated here.

[0200] In some embodiments, the surface layer of the first semiconductor material layer 300 on the side away from the first diaphragm 210 includes a first reserved area and a first etching area, and the first reserved area is used to form at least one of the following: the top of the first protruding structure 310, the top of the first reinforcing structure 410, and the top of the first supporting portion 510; the top of the first protruding structure 310 is the end of the first protruding structure 310 away from the first diaphragm 210, the top of the first reinforcing structure 410 is the end of the first reinforcing structure 410 away from the first diaphragm 210, and the top of the first supporting portion 510 is the end of the first supporting portion 510 away from the first diaphragm 210; before performing the first wet etching process on the first semiconductor material layer 300, the preparation method also includes: forming a first mask layer on the first semiconductor material layer 300; the first mask layer includes a first blocking portion and a first opening portion, the first opening portion exposes the first etching area, and in the first direction, the projection of the first blocking portion covers the projection of the first reserved area, and the projection area of ​​the first blocking portion is larger than the projection area of ​​the first reserved area. It can be understood that wet etching is isotropic etching, and the etchant will undercut the material layer. Therefore, the size of the first blocking portion is set to be larger than the size of the first reserved area to leave room for the process, so that the size of the first protruding structure 310, the first reinforcing structure 410 or the first supporting portion 510 finally prepared is more precise.

[0201] In some embodiments, the surface layer of the side of the third semiconductor material layer 800 away from the second sacrificial layer 620 includes a second reserved area and a second etching area, and the second reserved area is used to form at least one of the following: the top of the second protruding structure 810, the top of the second reinforcing structure 910, and the top of the third supporting portion 530. The top of the second protruding structure 810 is the end of the second protruding structure 810 away from the second sacrificial layer 620, the top of the second reinforcing structure 910 is the end of the second reinforcing structure 910 away from the second sacrificial layer 620, and the top of the third supporting portion 530 is the end of the third supporting portion 530 away from the second sacrificial layer 620; before performing the second wet etching process on the third semiconductor material layer 800, the preparation method also includes: forming a second mask layer on the third semiconductor material layer 800; the second mask layer includes a second blocking portion and a second opening portion, the second opening portion exposes the second etching area, and in the first direction, the projection of the second blocking portion covers the projection of the second reserved area, and the projection area of ​​the second blocking portion is larger than the projection area of ​​the second reserved area. It can be understood that wet etching is isotropic etching, and the etchant will undercut the material layer. Therefore, the size of the second shielding portion is set to be larger than the size of the second reserved area to leave room for the process, so that the size of the finally prepared second protruding structure 810, second reinforcing structure 910 or third supporting portion 530 is more precise.

[0202] The process of forming the first mask layer may include a first photolithography process, and the process of forming the second mask layer may include a second photolithography process.

[0203] In some embodiments, the mask used in the first photolithography process and the mask used in the second photolithography process have the same shape. Furthermore, the mask used in the first photolithography process and the mask used in the second photolithography process are the same mask. Specifically, when performing the first photolithography process, the mask used in the second photolithography process is used as the mask. This can save mask preparation, reduce process steps, and reduce costs.

[0204] Next, please refer to Figure 15 A back cavity 103 is formed from the second surface 102 side, penetrating the substrate 100 .

[0205] Next, please refer to Figure 1 , a portion of the fourth sacrificial layer 640 is etched away to form a third cavity 603, and the remaining fourth sacrificial layer 640 is formed into a third support structure 641 located on the first fixed area 212; a portion of the first sacrificial layer 610 is etched away to form a first cavity 601, and the remaining first sacrificial layer 610 is formed into a first support structure 611 located on the first fixed area 212; a portion of the second sacrificial layer 620 and the third sacrificial layer 630 is etched away to form a second cavity 602, and the remaining second sacrificial layer 620 and the third sacrificial layer 630 are formed into a second support structure 621 located on the second fixed area 222.

[0206] It should be noted that the MEMS device embodiments and the MEMS device preparation method embodiments provided in this application belong to the same concept; the various technical features in the technical solutions described in the various embodiments can be arbitrarily combined without conflict. However, it should be further noted that the MEMS device provided in the embodiments of this application, the combination of its various technical features can already solve the technical problem to be solved by this application; therefore, the MEMS device provided in the embodiments of this application is not limited by the MEMS device preparation method provided in the embodiments of this application, and any MEMS device prepared by the preparation method that can form the MEMS device structure provided in the embodiments of this application is within the scope of protection of this application.

[0207] It should be understood that the above embodiments are exemplary and are not intended to include all possible implementation methods. Various modifications and changes may be made to the above embodiments without departing from the scope of the present disclosure. Similarly, the various technical features of the above embodiments may be arbitrarily combined to form other embodiments of the present application that may not be explicitly described. Therefore, the above embodiments merely express several implementation methods of the present application and do not limit the scope of protection of the patent application.

Claims

1. A MEMS device, characterized in that: include: a substrate comprising a first surface and a second surface opposite to each other; a first diaphragm located on the first surface side, the first diaphragm including a first movable area and a first fixed area located outside the first movable area; a first protruding structure located on a side of the first diaphragm away from the substrate and connected to the first movable region, wherein a cross-sectional area of ​​the first protruding structure decreases along a first direction, the cross-section being a plane parallel to the first surface, and the first direction being a direction from the second surface to the first surface; the first protruding structure being made of SiN, wherein a Si content in the first protruding structure decreases and a N content increases along the first direction; a first supporting structure, located on a side of the first diaphragm away from the substrate and connected to the first fixing area; A back plate is located on a side of the first supporting structure away from the first diaphragm; wherein, in the first direction, the projection of the first protruding structure falls within the projection range of the back plate.

2. The MEMS device according to claim 1, wherein: Also includes: a first reinforcement structure located on a side of the first diaphragm away from the substrate, the cross-sectional area of ​​the first reinforcement structure decreasing along the first direction, and the first reinforcement structure and the first protruding structure formed in the same process based on the same material layer; Part of the first reinforcement structure is embedded in the first support structure.

3. The MEMS device according to claim 2, wherein: In the same plane, the cross-sectional area of ​​the first reinforcement structure is greater than the cross-sectional area of ​​the first protruding structure.

4. The MEMS device according to claim 1, wherein: Also includes: a second diaphragm, located on a side of the back plate away from the first diaphragm; a second supporting structure, located between the back plate and the second diaphragm, so that the second diaphragm is spaced apart from the back plate; a through opening, passing through the back plate along the first direction; a support column comprising a first support portion connected to the first diaphragm, a third support portion connected to the second diaphragm, and a second support portion connected between the first support portion and the third support portion along the first direction; the cross-sectional area of ​​the first support portion decreases along the first direction; the cross-sectional area of ​​the third support portion increases along the first direction; The second support portion passes through the through opening; the cross-sectional area of ​​the first support portion and the cross-sectional area of ​​the third support portion are both larger than the cross-sectional area of ​​the second support portion; The first supporting portion and the first protruding structure are formed in the same process based on the same material layer; A material of the third supporting portion includes SiN, and a Si content in the third supporting portion increases and a N content decreases along the first direction.

5. The MEMS device according to claim 4, wherein: The second diaphragm includes a second movable area and a second fixed area located outside the second movable area; The MEMS device further includes: a second protruding structure, located on a side of the second diaphragm facing the back plate and connected to the second movable region, wherein the cross-sectional area of ​​the second protruding structure increases along the first direction; wherein, in the first direction, a projection of the second protruding structure falls within a projection range of the back plate; The second protruding structure and the third supporting portion are formed in the same process based on the same material layer.

6. A method for preparing a MEMS device, characterized in that: The method comprises: providing a substrate comprising a first surface and a second surface opposite to each other; forming a first diaphragm on the first surface side, the first diaphragm including a first movable area and a first fixed area located outside the first movable area; forming a first semiconductor material layer on the first diaphragm, wherein the material of the first semiconductor material layer includes SiN, and the Si content of the first semiconductor material layer decreases and the N content increases along a first direction, wherein the first direction is from the second surface to the first surface; Performing a first wet etching process on the first semiconductor material layer to form a first protruding structure on the first movable area, wherein the cross-sectional area of ​​the first protruding structure decreases along the first direction, and the cross-sectional area is a plane parallel to the first surface; forming a first sacrificial layer covering the first diaphragm and the first protruding structure; A back plate is formed on the first sacrificial layer; wherein, in the first direction, the projection of the first protruding structure falls within the projection range of the back plate.

7. The method for preparing a MEMS device according to claim 6, wherein: The first semiconductor material layer is subjected to a first wet etching process to form a first reinforcement structure, wherein the first reinforcement structure is located on a side of the first diaphragm away from the substrate and connected to the first fixing region, and the cross-sectional area of ​​the first reinforcement structure decreases along the first direction; After forming the back plate on the first sacrificial layer, the method further includes: removing part of the first sacrificial layer, forming the remaining first sacrificial layer into a first supporting structure located on the first fixed area, and partially embedding the first reinforcing structure into the first supporting structure.

8. The method for preparing a MEMS device according to claim 7, wherein: In the same plane, the cross-sectional area of ​​the first reinforcement structure is greater than the cross-sectional area of ​​the first protruding structure.

9. The method for preparing a MEMS device according to claim 6, wherein: The first semiconductor material layer is subjected to a first wet etching process to form a first supporting portion, wherein the cross-sectional area of ​​the first supporting portion decreases along the first direction; A through opening is formed in the back plate and penetrates the back plate along a first direction; After forming the back plate on the first sacrificial layer, the method further includes: forming a second sacrificial layer covering the back plate and filling the through hole; forming a through hole penetrating the second sacrificial layer and the first sacrificial layer and passing through the through opening, wherein the through hole exposes the first supporting portion; filling a second semiconductor material layer in the through hole to form a second supporting portion; forming a third semiconductor material layer covering the second sacrificial layer and the second supporting portion, wherein the material of the third semiconductor material layer includes SiN, and the Si content in the third semiconductor material layer increases and the N content decreases along the first direction; performing a second wet etching process on the third semiconductor material layer to form a third supporting portion, wherein the cross-sectional area of ​​the third supporting portion increases along the first direction; the first supporting portion, the second supporting portion, and the third supporting portion are sequentially connected to form a supporting column, wherein the cross-sectional area of ​​the first supporting portion and the cross-sectional area of ​​the third supporting portion are both greater than the cross-sectional area of ​​the second supporting portion; A second diaphragm is formed on the third supporting portion.

10. The method for preparing a MEMS device according to claim 9, wherein: The second diaphragm includes a second movable area and a second fixed area located outside the second movable area; The second wet etching process is performed on the third semiconductor material layer to form a second protruding structure. The second protruding structure is located on the side of the second diaphragm facing the back plate and is connected to the second movable area. The cross-sectional area of ​​the second protruding structure increases along the first direction; wherein, in the first direction, the projection of the second protruding structure falls within the projection range of the back plate.

11. The method for preparing a MEMS device according to claim 9, wherein: Before forming the second diaphragm on the third supporting portion, the method further includes: forming a third sacrificial layer covering the sidewall of the third supporting portion and the second sacrificial layer, wherein the top surface of the third sacrificial layer and the top end of the third supporting portion form a flat surface, the top surface of the third sacrificial layer being the surface of the third sacrificial layer away from the second sacrificial layer, and the top end of the third supporting portion being the end of the third supporting portion away from the second sacrificial layer; The second diaphragm covers the third sacrificial layer and the third supporting portion.

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