A method for forming a MEMS structure and a MEMS structure

Abstract

The present application discloses a method for forming a MEMS structure and a MEMS structure. The method includes: providing a first substrate; forming a functional layer, the functional layer including a first sacrificial layer located on the first surface, a first diaphragm located on the surface of the first sacrificial layer, a second sacrificial layer located on the surface of the first diaphragm, a back plate located on the surface of the second sacrificial layer, and a third sacrificial layer located on the surface of the second sacrificial layer and the back plate; etching the third sacrificial layer and the second sacrificial layer to form a groove in the functional layer to expose the first diaphragm; forming a support structure in the groove and on the surface of the third sacrificial layer located around the groove; removing part of the second sacrificial layer and part of the third sacrificial layer to form a cavity in the functional layer to expose part of the first diaphragm, the back plate and the support structure; forming a second diaphragm on the side of the support structure away from the first substrate. By setting the above technical features, the stability and reliability of the support for the second diaphragm can be improved, and the manufacturing process can be simplified.

Description

Technical Field

[0001] The present application relates to the field of micro-electromechanical technology, and in particular to a method for forming a MEMS structure and a MEMS structure. Background Art

[0002] When using chips with MEMS (Micro-Electrical-Mechanical Systems) structures in microphones, commonly used MEMS structures can be roughly divided into single-membrane, dual-membrane, and dual-backplate structures. The dual-membrane structure, due to its vacuum seal, has less air damping and lower MEMS noise, resulting in a better signal-to-noise ratio for dual-membrane MEMS microphones.

[0003] In the related art, the dual-membrane structure MEMS microphone forms a lower diaphragm and an upper diaphragm stacked in sequence on a substrate. In order to meet process requirements, a release hole is opened on the upper diaphragm, and the release hole is sealed after the sacrificial layer is released. Therefore, the manufacturing process of its MEMS structure is complicated, and the support stability of the upper diaphragm in the MEMS structure is poor. Summary of the Invention

[0004] In view of the above-mentioned defects of the related art, the technical problem to be solved by this application is how to improve the reliability of the MEMS structure on the basis of simplifying the MEMS structure manufacturing process.

[0005] In order to solve at least one of the above-mentioned technical problems, the present application discloses a method for forming a MEMS structure and a MEMS structure.

[0006] According to one aspect of the present application, a method for forming a MEMS structure is provided, comprising:

[0007] providing a first substrate;

[0008] A functional layer is formed on the first surface of the first substrate, the functional layer including a first sacrificial layer located on the first surface, a first diaphragm located on the surface of the first sacrificial layer, a second sacrificial layer located on the surface of the first diaphragm, a back plate located on the surface of the second sacrificial layer, and a third sacrificial layer, the back plate having a plurality of openings, the third sacrificial layer being located on the surface of the back plate and filling the plurality of openings; the openings having a first projection in a direction perpendicular to the first surface;

[0009] Etching the third sacrificial layer and the second sacrificial layer to form a groove in the functional layer that exposes the first diaphragm, wherein the groove has a second projection in a direction perpendicular to the first surface, and the second projection is located inside the first projection;

[0010] forming a support structure in the groove and on a portion of the surface of the third sacrificial layer located around the groove;

[0011] removing a portion of the second sacrificial layer and a portion of the third sacrificial layer to form a cavity in the functional layer that exposes a portion of the first diaphragm, the back plate, and the support structure;

[0012] A second diaphragm is formed on a side of the support structure away from the first substrate.

[0013] Optionally, the support structure includes a first part located in the groove and a second part located at an end of the first part away from the first substrate; the first part has a third projection in a direction perpendicular to the first surface, and the second part has a fourth projection in a direction perpendicular to the first surface, and the third projection is located inside the fourth projection.

[0014] Optionally, the method of forming a support structure in the groove and on a portion of the surface of the third sacrificial layer located around the groove includes:

[0015] forming a supporting layer in the groove and on the surface of the third sacrificial layer;

[0016] A portion of the support layer located on the surface of the third sacrificial layer is patterned to form a support structure.

[0017] Optionally, the method for forming a support structure further includes: after forming the support layer and before patterning a portion of the support layer, planarizing the support layer.

[0018] Optionally, after patterning the support layer, a plurality of etching openings are formed in the support layer;

[0019] The method of forming a cavity in the functional layer to expose a portion of the first diaphragm, the back plate, and the support structure includes:

[0020] The third sacrificial layer and the second sacrificial layer are etched by using a plurality of etching openings until the first diaphragm, the back plate and the supporting structure are exposed to form a cavity.

[0021] Optionally, the method of forming the second diaphragm on a side of the support structure away from the first substrate includes:

[0022] forming a first wafer structure, the first wafer structure including a second substrate, a fourth sacrificial layer located on a surface of the second substrate, and a second diaphragm located on a surface of the fourth sacrificial layer;

[0023] The first wafer structure is bonded to the first surface of the first substrate, and the second diaphragm is in contact with the support structure.

[0024] Optionally, after forming the second diaphragm, the method includes:

[0025] removing the second substrate and the fourth sacrificial layer;

[0026] The first substrate and the first sacrificial layer are etched from the second surface of the first substrate until the first diaphragm is exposed to form a back cavity, wherein the second surface is opposite to the first surface.

[0027] Optionally, the method for forming the functional layer includes:

[0028] A first sacrificial layer, a first diaphragm, and a second sacrificial layer are sequentially formed on a side surface of the first substrate; the first sacrificial layer is located on a side surface of the first substrate, the first diaphragm is located on a side surface of the first sacrificial layer away from the first substrate; and the second sacrificial layer is located on a side surface of the first diaphragm away from the first substrate;

[0029] forming a back plate material layer on the surface of the second sacrificial layer;

[0030] Patterning the back plate material layer to form a back plate;

[0031] A third sacrificial layer is formed on the surface of the second sacrificial layer and the surface of the back plate.

[0032] According to a second aspect of the present application, a MEMS structure is provided, comprising:

[0033] a first substrate;

[0034] a first diaphragm, located on the first surface of the first substrate;

[0035] a back plate, located on a side of the first diaphragm away from the first substrate, the back plate having a plurality of openings;

[0036] a supporting structure, located on a side of the back plate away from the first substrate, the supporting structure passing through the opening and in contact with the first diaphragm;

[0037] The second diaphragm is bonded to a side of the support structure away from the first substrate.

[0038] Optionally, the functional layer has a groove, the groove has a second projection in a direction perpendicular to the first surface, and the second projection is located inside the first projection;

[0039] The support structure includes a first portion passing through the opening and a second portion located at an end of the first portion away from the first substrate, the first portion has a third projection in a direction perpendicular to the first surface, the second portion has a fourth projection in a direction perpendicular to the first surface, and the third projection is located inside the fourth projection.

[0040] The method for forming a MEMS structure disclosed in an embodiment of the present application forms a functional layer including a first diaphragm on a first substrate, and after forming a support structure, the first diaphragm and a second diaphragm are bonded together to obtain a MEMS structure. Because the first diaphragm is formed on the first substrate and the second diaphragm is formed on the second substrate, compared to the related art method of sequentially forming the first and second diaphragms on the same substrate, the embodiment of the present application does not require the second diaphragm to be etched and then sealed, thereby simplifying the MEMS structure manufacturing process.

[0041] The supporting structure includes a first part located in the groove and a second part connected to the first part, so that the supporting structure is "mushroom-shaped", thereby increasing the contact area between the supporting structure and the second diaphragm, and providing stable and reliable support for the second diaphragm.

[0042] Other features and advantages of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0044] In order to more completely understand the present application and its beneficial effects, the following description will be given in conjunction with the accompanying drawings, wherein the same drawing numbers represent the same parts in the following description.

[0045] Figure 1 A schematic flow chart corresponding to a method for forming a MEMS structure according to a specific embodiment of the present disclosure;

[0046] Figure 2 This is a schematic structural diagram corresponding to step S2 in the formation method provided in a specific embodiment of the present disclosure;

[0047] Figure 3 This is a schematic structural diagram corresponding to step S3 in the formation method provided in a specific embodiment of the present disclosure;

[0048] Figure 4 Schematic diagram of the structure corresponding to step S4 in the formation method provided in the specific embodiment of the present disclosure Figure 1 ;

[0049] Figure 5 Schematic diagram of the structure corresponding to step S4 in the formation method provided in the specific embodiment of the present disclosure Figure 2 ;

[0050] Figure 6This is a schematic structural diagram corresponding to step S5 in the formation method provided in a specific embodiment of the present disclosure;

[0051] Figure 7 A structural schematic diagram corresponding to the second wafer structure provided in a specific embodiment of the present disclosure;

[0052] Figure 8 The structure corresponding to step S6 in the formation method provided in the specific embodiment of the present disclosure is shown in FIG. Figure 1 ;

[0053] Figure 9 The structure corresponding to step S6 in the formation method provided in the specific embodiment of the present disclosure is shown in FIG. Figure 2 ;

[0054] Figure 10 This is a structural schematic diagram corresponding to step S7 in the formation method provided in a specific embodiment of the present disclosure;

[0055] Figure 11 The structure corresponding to step S8 in the formation method provided in the specific embodiment of the present disclosure is shown in FIG. Figure 1 ;

[0056] Figure 12 The structure corresponding to step S8 in the formation method provided in the specific embodiment of the present disclosure is shown in FIG. Figure 2 .

[0057] Description of reference numerals:

[0058] 1-first wafer structure, 2-second wafer structure, 3-functional layer;

[0059] 10-first substrate, 11-back cavity, 12-second substrate;

[0060] 20-first sacrificial layer, 21-second sacrificial layer, 22-third sacrificial layer, 23-fourth sacrificial layer;

[0061] 30-first diaphragm, 31-second diaphragm;

[0062] 40-back plate, 41-opening, 42-groove, 43-cavity;

[0063] 50-support layer, 51-support body, 52-support structure, 53-first part, 54-second part. DETAILED DESCRIPTION

[0064] The following will be combined with the drawings in the embodiments of this specification to clearly and completely describe the technical solutions in the embodiments of this specification. Obviously, the embodiments described are only part of the embodiments of this specification, not all of the embodiments. Based on the embodiments in this specification, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0065] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or server that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0066] Various exemplary embodiments, features, and aspects of the present disclosure will be described in detail below with reference to the accompanying drawings. The same reference numerals in the accompanying drawings represent elements with the same or similar functions. Although various aspects of the embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless otherwise indicated.

[0067] The word “exemplary” is used exclusively herein to mean “serving as an example, example, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

[0068] The term "and / or" as used herein describes an association relationship between associated objects, indicating that three relationships can exist. For example, "A and / or B" can represent the existence of A alone, the simultaneous existence of A and B, and the existence of B alone. Furthermore, the term "at least one" as used herein refers to any combination of at least two of any one or more of a plurality of items. For example, "at least one of A, B, and C" can represent any one or more elements selected from the set consisting of A, B, and C.

[0069] In addition, numerous specific details are provided in the following detailed description to better illustrate the present disclosure. Those skilled in the art will appreciate that the present disclosure can be practiced without certain specific details. In some instances, methods, means, components, and circuits well known to those skilled in the art are not described in detail in order to highlight the main points of the present disclosure.

[0070] Figure 1Schematic diagram of the process flow corresponding to the MEMS structure forming method provided by the exemplary embodiment of the present disclosure. Figure 1 As shown, a method for forming a MEMS structure includes:

[0071] Step S1: providing a first substrate 10;

[0072] Step S2: A functional layer 3 is formed on the first surface of the first substrate 10. The functional layer 3 includes a first sacrificial layer 20 located on the first surface, a first diaphragm 30 located on the surface of the first sacrificial layer 20, a second sacrificial layer 21 located on the surface of the first diaphragm 30, a back plate 40 located on the surface of the second sacrificial layer 21, and a third sacrificial layer 22. The back plate 40 includes a plurality of openings 41. The third sacrificial layer 22 is located on the surface of the back plate 40 and fills the plurality of openings 41. The openings 41 have a first projection in a direction perpendicular to the first surface.

[0073] In some embodiments, the first substrate 10 may be a silicon substrate. The first substrate 10 has a first surface and a second surface that are opposite to each other along a stacking direction. The functional layer 3 may be formed on either the first surface or the second surface. The stacking direction is the direction in which the first substrate 10 and the functional layer 3 are stacked. In this embodiment, the functional layer 3 may be formed on the first surface of the first substrate 10.

[0074] Figure 2 This is a schematic structural diagram corresponding to step S2 in the formation method provided in a specific embodiment of the present disclosure. Figure 2 As shown, the stacking direction is direction A. The functional layer 3 includes a first sacrificial layer 20, a first diaphragm 30, a second sacrificial layer 21, a back plate 40, and a third sacrificial layer 22, which are arranged in sequence along the stacking direction. Among them, the material of the first diaphragm 30 can be polysilicon or polysilicon doped with silicon nitride. The material of the back plate 40 can be polysilicon or polysilicon doped with silicon nitride. The material of the first sacrificial layer 20, the second sacrificial layer 21, and the third sacrificial layer 22 can all be silicon dioxide. Setting the material of each sacrificial layer to be the same can improve the convenience of subsequent release of each sacrificial layer.

[0075] The method for forming the functional layer 3 includes:

[0076] A first sacrificial layer 20, a first diaphragm 30, and a second sacrificial layer 21 are sequentially formed on one side surface of the first substrate 10; the first sacrificial layer 20 is located on one side surface of the first substrate 10, the first diaphragm 30 is located on a side surface of the first sacrificial layer 20 away from the first substrate 10; and the second sacrificial layer 21 is located on a side surface of the first diaphragm 30 away from the first substrate 10.

[0077] forming a back plate 40 material layer on the surface of the second sacrificial layer 21;

[0078] Patterning the back plate 40 material layer to form the back plate 40;

[0079] A third sacrificial layer 22 is formed on the surface of the second sacrificial layer 21 and the surface of the back plate 40 .

[0080] In some embodiments, silicon dioxide may be deposited on the first surface of the first substrate 10 to form a first sacrificial layer 20. The first sacrificial layer 20 is used to provide support for the first diaphragm 30 and to protect the first diaphragm 30 when the first substrate 10 is subsequently etched to form the back cavity 11, thereby preventing damage to the first diaphragm 30 during the formation of the back cavity 11.

[0081] Polysilicon is deposited on the surface of the first sacrificial layer 20 away from the first substrate 10 to form a first diaphragm 30. Silicon dioxide is deposited on the surface of the first diaphragm 30 away from the first substrate 10 to form a second sacrificial layer 21. The second sacrificial layer 21 is used to provide support for the back plate 40 and to protect the first diaphragm 30 during the subsequent process of patterning the back plate 40 material layer to form the back plate 40.

[0082] Silicon nitride and polysilicon are deposited on the surface of the second sacrificial layer 21 away from the first substrate 10 to form a back electrode plate 40 material layer, and then the back electrode plate 40 material layer is patterned to form a back electrode plate 40 having a plurality of openings 41. Part of the surface of the second sacrificial layer 21 is exposed from the openings 41.

[0083] Silicon dioxide is deposited on the side surface of the back plate 40 away from the first substrate 10 and the partial surface of the second sacrificial layer 21 exposed in the opening 41 to form a third sacrificial layer 22 covering the surface of the back plate 40 and a portion of the second sacrificial layer 21 .

[0084] Step S3: etching the third sacrificial layer 22 and the second sacrificial layer 21 to form a groove 42 in the functional layer 3 that exposes the first diaphragm 30. The groove 42 has a second projection in a direction perpendicular to the first surface, and the second projection is located inside the first projection.

[0085] Figure 3 This is a schematic structural diagram corresponding to step S3 in the formation method provided in a specific embodiment of the present disclosure. Figure 3 As shown, the third sacrificial layer 22 and the second sacrificial layer 21 are etched, and the etching position can be the opening 41, so as to form a groove 42 in the functional layer 3 that exposes a portion of the surface of the first diaphragm 30. The groove 42 is located in the opening 41, so that the support structure 52 is subsequently formed at the location of the groove 42, so that the support structure 52 can be evenly distributed, thereby improving the stability and reliability of the support structure 52.

[0086] Step S4 : forming a support structure 52 in the groove 42 and on a portion of the surface of the third sacrificial layer 22 located around the groove 42 .

[0087] In some embodiments, the support structure 52 can be obtained by etching the support layer 50. The material of the support layer 50 can be silicon nitride. Step S4 can include:

[0088] A support layer 50 is formed in the groove 42 and on the surface of the third sacrificial layer 22;

[0089] A portion of the support layer 50 located on the surface of the third sacrificial layer 22 is patterned to form a support structure 52. The support structure 52 includes a first portion 53 located within the groove 42 and a second portion 54 located at an end of the first portion 53 away from the first substrate 10. The first portion 53 has a third projection in a direction perpendicular to the first surface, and the second portion 54 has a fourth projection in a direction perpendicular to the first surface, and the third projection is located within the fourth projection.

[0090] Figure 4 Schematic diagram of the structure corresponding to step S4 in the formation method provided in the specific embodiment of the present disclosure Figure 1 .like Figure 4 As shown, silicon nitride is deposited in the groove 42 and on the side of the third sacrificial layer 22 away from the first substrate 10 to form a support layer 50, so that the support layer 50 can cover the surface of the third sacrificial layer 22 and the portion of the surface of the first diaphragm 30 exposed from the groove 42.

[0091] After forming the support layer 50, the portion of the support layer 50 located on the surface of the third sacrificial layer 22 may be patterned. Figure 5 As shown, the support layer 50 on the surface of the third sacrificial layer 22 between two adjacent grooves 42 can be etched to form a support structure 52 including a first portion 53 and a second portion 54. The first portion 53 has a third projection in a direction perpendicular to the first surface, and the second portion 54 has a fourth projection in a direction perpendicular to the first surface. The third projection is located inside the fourth projection, so that the support structure 52 is a "mushroom-shaped" support structure 52. Compared with the arrangement of the first portion 53 alone as the support structure 52, the "mushroom-shaped" support structure 52 can increase the contact area between the second diaphragm 31, thereby improving the stability and reliability of the support for the second diaphragm 31.

[0092] In some embodiments, after patterning the support layer 50, in addition to forming the support structure 52, the support body 51 may also be formed. Specifically, a portion of the support layer 50 located at the edge of the surface of the third sacrificial layer 22 may also be etched. The support body 51 is adjacent to the support structure 52, and an etching opening may exist between the support body 51 and the support structure 52. Etching openings may also exist between two adjacent support structures 52, allowing etching liquid to enter through the multiple etching openings and subsequently release the second sacrificial layer 21 and the third sacrificial layer 22.

[0093] In some embodiments, after forming the support layer 50 and before patterning a portion of the support layer 50, the support layer 50 is planarized. By planarizing the support layer 50, the surfaces of the support body 51 and the plurality of support structures 52 can be made flat, thereby improving the subsequent bonding effect with the second diaphragm 31 and making the surface of the ultimately formed MEMS structure flat.

[0094] Step S5 : removing a portion of the second sacrificial layer 21 and a portion of the third sacrificial layer 22 , and forming a cavity 43 in the functional layer 3 that exposes a portion of the first diaphragm 30 , the back plate 40 and the support structure 52 .

[0095] Specifically, the support layer 50 has etching openings between adjacent support structures 52, and also between the support body 51 and the support structure 52. The third sacrificial layer 22 and the second sacrificial layer 21 can be etched using the multiple etching openings until the first diaphragm 30, the back plate 40, and the support structure 52 are exposed, forming a cavity 43.

[0096] Figure 6 This is a schematic diagram of the structure corresponding to step S5 in the formation method provided in the specific embodiment of the present disclosure. Figure 6 Schematic diagram of the structure of the second wafer structure 2. Figure 6 As shown, all the second sacrificial layers 21 and all the third sacrificial layers 22 between adjacent support structures 52 are removed to form a cavity 43 between adjacent support structures 52 , exposing a portion of the first diaphragm 30 , the back plate 40 and the support structure 52 .

[0097] Furthermore, the portion of the third sacrificial layer 22 covered by the support body 51 and the second portion 54 of the support structure 52, as well as the portion of the second sacrificial layer 21 below the portion of the third sacrificial layer 22, are removed. The specific distance between the portion of the second sacrificial layer 21 and the portion of the third sacrificial layer 22 removed in a direction parallel to the surface of the first substrate 10 can be adaptively adjusted based on different needs, and this adjustment can be achieved by adjusting the duration of the removal process. For example, the specific distance between the third sacrificial layer 22 and the second sacrificial layer 21 removed can be adjusted by controlling the timing of injecting the etching solution through the opening between the support body 51 and the support structure 52.

[0098] In some embodiments, after the support body 51 and the support structure 52 are formed, a portion of the second sacrificial layer 21 and a portion of the third sacrificial layer 22 are removed to form the second wafer structure 2 . Figure 6 and Figure 7 Schematic diagrams of the structure corresponding to the second wafer structure 2 at different viewing angles. Figure 7 As shown, the support body 51 surrounds the outside of multiple support structures 52.

[0099] Step S6 : forming a second diaphragm 31 on a side of the support structure 52 away from the first substrate 10 .

[0100] In some embodiments, the second diaphragm 31 may be formed by bonding the first wafer structure 1 and the second wafer structure 2 .

[0101] Figure 8 The structure corresponding to step S6 in the formation method provided in the specific embodiment of the present disclosure is shown in FIG. Figure 1 .like Figure 8 As shown, a first wafer structure 1 is first formed. The first wafer structure 1 includes a second substrate 12 , a fourth sacrificial layer 23 located on a surface of the second substrate 12 , and a second diaphragm 31 located on a surface of the fourth sacrificial layer 23 .

[0102] In some embodiments, the second substrate 12 may be a silicon substrate. The first substrate 10 has a first surface and a second surface that are opposed to each other along the stacking direction. A fourth sacrificial layer 23 may be formed on either the first surface or the second surface, and a second diaphragm 31 may be formed on the surface of the fourth sacrificial layer 23 facing away from the second substrate 12. The fourth sacrificial layer 23 may be made of silicon dioxide. The second diaphragm 31 may be made of polycrystalline silicon or polycrystalline silicon doped with silicon nitride.

[0103] In some embodiments, the fourth sacrificial layer 23 is used to provide support for the second diaphragm 31 in the first wafer structure 1 and to protect the second diaphragm 31 during the subsequent removal of the second substrate 12 .

[0104] Furthermore, after obtaining the first wafer structure 1 , the first wafer structure 1 is bonded toward the first surface of the first substrate 10 , and the second diaphragm 31 is in contact with the support structure 52 .

[0105] Figure 9 The structure corresponding to step S6 in the formation method provided in the specific embodiment of the present disclosure is shown in FIG. Figure 2 .like Figure 9 As shown, the second diaphragm 31 contacts the support body 51 and the second part 54 of the multiple support structures 52, thereby bonding the first wafer structure 1 and the second wafer structure 2, and forming a low-pressure sealed (e.g., vacuum sealed) cavity between the first diaphragm 30 and the second diaphragm 31.

[0106] The MEMS structure is divided into a first wafer structure 1 and a second wafer structure 2. First, a "mushroom-shaped" support structure 52 is formed in the second wafer structure 2, and then the second diaphragm 31 is bonded to the "mushroom-shaped" support structure 52 to form a MEMS structure. Compared with the related art, in this embodiment, there is no need to set a release hole for releasing the sacrificial layer on the second diaphragm 31, and thus there is no need to seal the second diaphragm 31 during the formation of the MEMS structure, thereby simplifying the manufacturing process of the MEMS structure. At the same time, the "mushroom-shaped" support structure 52 can increase the contact area between the support structure 52 and the second diaphragm 31, thereby improving the stability and reliability of the support for the second diaphragm 31, so that the MEMS structure has better structural reliability.

[0107] Step S7: removing the second substrate 12 and the fourth sacrificial layer 23 .

[0108] Figure 10 This is a schematic structural diagram corresponding to step S7 in the formation method provided in a specific embodiment of the present disclosure. Figure 10 As shown, after the first wafer structure 1 and the second wafer structure 2 are bonded, the second substrate 12 and the fourth sacrificial layer 23 are removed, so that the second diaphragm 31 is exposed and located on the surface of each layer structure.

[0109] Step S8 : etching the first substrate 10 and the first sacrificial layer 20 from the second surface of the first substrate 10 until the first diaphragm 30 is exposed to form the back cavity 11 , with the second surface facing the first surface.

[0110] like Figure 11 As shown, after removing the second substrate 12 and the fourth sacrificial layer 23, the first substrate 10 is first etched from the second surface of the first substrate 10. Figure 12 As shown, the first sacrificial layer 20 is etched to expose the first diaphragm 30 and form a back cavity 11 penetrating the first substrate 10 and the first sacrificial layer 20 .

[0111] Correspondingly, the technical solution of this application also discloses a MEMS structure, which is obtained by using the method for forming the MEMS structure as described in any of the above embodiments. Figure 12 As shown, a MEMS structure includes:

[0112] a first substrate 10;

[0113] The first diaphragm 30 is located on the first surface of the first substrate 10;

[0114] a back plate 40 , located on a side of the first diaphragm 30 away from the first substrate 10 , and having a plurality of openings 41 ;

[0115] The support structure 52 is located on a side of the back plate 40 away from the first substrate 10 . The support structure 52 passes through the opening 41 and contacts the first diaphragm 30 .

[0116] The second diaphragm 31 is bonded to a side of the support structure 52 away from the first substrate 10 .

[0117] In some embodiments, the support structure 52 includes a first portion 53 passing through the opening 41 and a second portion 54 located at an end of the first portion 53 away from the first substrate 10. The first portion 53 has a third projection in a direction perpendicular to the first surface, and the second portion 54 has a fourth projection in a direction perpendicular to the first surface, and the third projection is located inside the fourth projection.

[0118] Since the MEMS structure in this embodiment is obtained by adopting the formation method described in any of the above embodiments, the MEMS structure also has structural reliability and a simple manufacturing process.

[0119] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0120] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0121] The embodiments, implementation methods and related technical features of the present application can be combined and replaced with each other without conflict.

[0122] The above are only preferred embodiments of the present application and are not intended to limit the present application in any form. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present application without departing from the content of the technical solution of the present application shall still fall within the scope of the technical solution of the present application. The selection of terms used in this article is intended to best explain the principles, practical applications, or technical improvements of each embodiment in the market, or to enable other ordinary technicians in this technical field to understand the embodiments disclosed herein.

Claims

1. A method for forming a MEMS structure, characterized in that: include: providing a first substrate; forming a functional layer on the first surface of the first substrate, the functional layer comprising a first sacrificial layer located on the first surface, a first diaphragm located on a surface of the first sacrificial layer, a second sacrificial layer located on a surface of the first diaphragm, a back plate located on a surface of the second sacrificial layer, and a third sacrificial layer, the back plate having a plurality of openings, the third sacrificial layer being located on a surface of the back plate and filling the plurality of openings; The opening has a first projection in a direction perpendicular to the first surface; Etching the third sacrificial layer and the second sacrificial layer to form a groove in the functional layer that exposes the first diaphragm, wherein the groove has a second projection in a direction perpendicular to the first surface, and the second projection is located inside the first projection; A support structure is formed in the groove and on a portion of the surface of the third sacrificial layer located around the groove; the support structure includes a first portion located in the groove and a second portion located at an end of the first portion away from the first substrate; the first portion has a third projection in a direction perpendicular to the first surface, the second portion has a fourth projection in a direction perpendicular to the first surface, and the third projection is located inside the fourth projection; the second portion is obtained by patterning a portion of the support layer located on the surface of the third sacrificial layer; removing a portion of the second sacrificial layer and a portion of the third sacrificial layer to form a cavity in the functional layer that exposes a portion of the first diaphragm, the back plate, and the support structure; A second diaphragm is formed on a side of the support structure away from the first substrate.

2. The method for forming a MEMS structure according to claim 1, wherein: The method of forming a support structure in the groove and on a portion of the surface of the third sacrificial layer located around the groove comprises: forming a supporting layer in the groove and on the surface of the third sacrificial layer; A portion of the support layer located on the surface of the third sacrificial layer is patterned to form the support structure.

3. The method for forming a MEMS structure according to claim 2, wherein: The method for forming the support structure further includes: after forming the support layer and before patterning the portion of the support layer, planarizing the support layer.

4. The method for forming a MEMS structure according to claim 2, wherein: After patterning the support layer, a plurality of etching openings are formed in the support layer; The method of forming a cavity in the functional layer to expose a portion of the first diaphragm, the back plate, and the support structure includes: The third sacrificial layer and the second sacrificial layer are etched using the multiple etching openings until the first diaphragm, the back plate and the supporting structure are exposed to form the cavity.

5. The method for forming a MEMS structure according to claim 1, wherein: The method of forming the second diaphragm on the side of the support structure away from the first substrate includes: forming a first wafer structure, the first wafer structure comprising a second substrate, a fourth sacrificial layer located on a surface of the second substrate, and a second diaphragm located on a surface of the fourth sacrificial layer; The first wafer structure is bonded toward the first surface of the first substrate, and the second diaphragm is in contact with the support structure.

6. The method for forming a MEMS structure according to claim 5, wherein: After forming the second diaphragm, the method includes: removing the second substrate and the fourth sacrificial layer; The first substrate and the first sacrificial layer are etched from the second surface of the first substrate until the first diaphragm is exposed to form a back cavity, wherein the second surface is opposite to the first surface.

7. The method for forming a MEMS structure according to claim 1, wherein: The method for forming the functional layer includes: The first sacrificial layer, the first diaphragm, and the second sacrificial layer are sequentially formed on one side surface of the first substrate; the first sacrificial layer is located on one side surface of the first substrate, the first diaphragm is located on a side surface of the first sacrificial layer away from the first substrate; and the second sacrificial layer is located on a side surface of the first diaphragm away from the first substrate; forming a back plate material layer on the surface of the second sacrificial layer; Patterning the back plate material layer to form the back plate; The third sacrificial layer is formed on the surface of the second sacrificial layer and the surface of the back plate.

8. A MEMS structure, characterized in that: include: a first substrate; a first diaphragm, located on the first surface of the first substrate; a back plate, located on a side of the first diaphragm away from the first substrate, the back plate having a plurality of openings; a support structure located on a side of the back plate away from the first substrate, the support structure passing through the opening and in contact with the first diaphragm; the support structure comprising a first portion passing through the opening and a second portion located at an end of the first portion away from the first substrate, the first portion having a third projection in a direction perpendicular to the first surface, the second portion having a fourth projection in a direction perpendicular to the first surface, the third projection being located within the fourth projection; and the second portion being obtained by patterning a portion of the support layer; The second diaphragm is bonded to a side of the support structure away from the first substrate.

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