Membrane structure, mems microphone and manufacturing method

Abstract

The application discloses a MEMS structure, a MEMS microphone and a preparation method. The MEMS structure comprises a first structure layer, a second structure layer, a spacer layer arranged between the first structure layer and the second structure layer to form a first cavity between the second structure layer and the first structure layer, and a main structure layer and an auxiliary structure layer. The main structure layer is provided with a first opening, the auxiliary structure layer is arranged on the side of the first cavity of the first opening, the auxiliary structure layer is provided with a second opening, the first opening and the second opening are staggered in the thickness direction of the second structure layer, and the first opening and the second opening are communicated through a transverse gap to form a release channel. A sealing layer is arranged at the release channel to seal the release channel. The MEMS structure disclosed by the application is beneficial to improving the performance.

Description

Technical Field

[0001] This application generally relates to the field of semiconductor technology. More specifically, this application relates to a MEMS structure, a MEMS microphone, and a method for fabricating it. Background Technology

[0002] MEMS (Micro-Electro-Mechanical Systems) devices are widely used in sensors, microphones, pressure gauges, and other fields. In the manufacturing process of MEMS devices, it is usually necessary to form cavities between structural layers and perform release etching on the sacrificial layer through release holes, and then seal the release holes to create the required gas pressure environment or vacuum cavity inside the device.

[0003] Traditional MEMS release holes typically employ a vertical hole structure, for example... Figure 1 As shown, a through-hole vertical release hole 102 is directly etched into the top structural layer 101. This vertical release hole 102 then etches the underlying sacrificial layer 103, forming a cavity 104. Subsequently, a sealing film 106 is deposited on the device surface to seal the vertical release hole 102. However, this vertical release hole structure has an inherent drawback: during the deposition of the sealing film 106, some sealing material is deposited through the vertical release hole 102 onto the surface of the bottom structural layer 105 directly below the release hole, forming a protrusion 107. The deposition area of ​​this protrusion 107 is typically larger than the opening area of ​​the release hole. This protrusion 107 occupies the movement space above the bottom structural layer 105, limiting the downward deformation space of the top structural layer 101 in applications such as pressure sensors, thus directly affecting the measurement range and linearity of the MEMS device.

[0004] In view of this, there is an urgent need to provide a MEMS structure solution to avoid the formation of protrusions on the surface of the bottom structural layer by the sealing layer, thereby improving the performance and measurement accuracy of MEMS devices. Summary of the Invention

[0005] In order to at least solve one or more of the technical problems mentioned above, this application proposes solutions for MEMS structures, MEMS microphones and fabrication methods in several aspects.

[0006] In a first aspect, this application provides a MEMS structure, comprising: a first structural layer; a second structural layer having a spacer layer between it and the first structural layer to form a first cavity between the second structural layer and the first structural layer, the second structural layer comprising a main structural layer and an auxiliary structural layer, the main structural layer and the auxiliary structural layer being contacted and connected at at least one first region and separated from each other at at least one second region to form a lateral gap, wherein the main structural layer has a first opening, the auxiliary structural layer is disposed on the side of the first opening facing the first cavity, the auxiliary structural layer has a second opening, the first opening and the second opening are offset in the thickness direction of the second structural layer, and the first opening and the second opening are connected through the lateral gap to form a release channel; and a sealing layer located at the release channel to seal the release channel.

[0007] In some embodiments, the sealing layer covers the inner wall of the first opening and extends along the thickness direction of the second structural layer to an auxiliary structural layer corresponding to the first opening, so as to seal the transverse gap.

[0008] In other embodiments, the surface of the main structural layer facing the first cavity has a protrusion facing the second opening at a position corresponding to the second opening.

[0009] In some other embodiments, the main structural layer is disposed on the spacer layer, and in a plane perpendicular to the thickness direction of the second structural layer, the projection of the main structural layer and the spacer layer partially overlap, while the projection of the auxiliary structural layer and the spacer layer do not overlap.

[0010] In some embodiments, the first opening is a groove-shaped structure or a hole-shaped structure; the second opening is a hole-shaped structure.

[0011] In other embodiments, the thickness of the transverse gap is 0.02 μm to 0.5 μm; and / or the thickness of the auxiliary structural layer is 0.1 μm to 0.5 μm.

[0012] In some other embodiments, the width of the first opening is 1 μm to 5 μm; the width of the first opening is smaller than the width of the second opening.

[0013] In some embodiments, the first structural layer includes a first electrode layer, a first dielectric layer, and a second electrode layer stacked together; wherein a third opening is provided on the first dielectric layer, and the first electrode layer and the second electrode layer are electrically connected through the third opening.

[0014] In other embodiments, the MEMS structure further includes a third structural layer, which is spaced apart from the first structural layer, and the first structural layer is located between the second structural layer and the third structural layer, with the third structural layer forming a second cavity between the first structural layer and the third structural layer.

[0015] In some other embodiments, the MEMS structure further includes: a connecting post connecting the second structural layer and the third structural layer; and the first structural layer is provided with a plurality of fourth openings, at least some of which are used for the connecting post to pass through.

[0016] In some embodiments, at least one first conductive post is disposed on the surface of the main structural layer facing the first structural layer, and the at least one first conductive post includes a first annular conductive post configured to surround the connecting post.

[0017] In other embodiments, at least one second conductive post is disposed on the surface of the third structural layer facing the first structural layer, the at least one second conductive post including a second annular conductive post configured to surround the connecting post; and with the first structural layer as the symmetrical layer, the second conductive post and the first conductive post are symmetrically distributed.

[0018] In some other embodiments, the width of the first annular conductive post is 0.3 μm to 1 μm.

[0019] In a second aspect, this application provides a MEMS microphone, including the MEMS structure according to any one of the first aspects of this application.

[0020] In a third aspect, this application provides a method for fabricating a MEMS structure, comprising: depositing a first sacrificial layer on a first structural layer; forming an auxiliary structural layer having a second opening on the first sacrificial layer; forming a main structural layer having a first opening on the auxiliary structural layer, and contacting and connecting the main structural layer and the auxiliary structural layer at at least one first region, separating them from each other at at least one second region to form a lateral gap, wherein the first opening and the second opening are offset in their thickness direction so as to form a release channel through the first opening, the lateral gap and the second opening; using the release channel, etching a portion of the first sacrificial layer to form a first cavity between the second structural layer composed of the auxiliary structural layer and the main structural layer and the first structural layer, wherein the unetched portion of the first sacrificial layer constitutes a spacer layer between the first structural layer and the second structural layer; and sealing the release channel.

[0021] In some embodiments, sealing the release channel includes: depositing a sealing layer on the main structural layer; and etching the sealing layer using a photomask-free etching process to retain the sealing layer covering the inner wall of the first opening and extending to the auxiliary structural layer based on the sidewall effect, so as to seal the lateral gap.

[0022] In other embodiments, the preparation method further includes: forming an auxiliary structural layer with a second opening on the surface of the middle region of the first sacrificial layer; and etching the middle region of the first sacrificial layer while etching a portion of the first sacrificial layer.

[0023] In some other embodiments, the first opening is a groove-shaped structure or a hole-shaped structure; the second opening is a hole-shaped structure.

[0024] In some embodiments, forming the release channel includes: depositing a second sacrificial layer on the auxiliary structural layer; etching the second sacrificial layer to retain a first sacrificial portion covering the second opening and a second sacrificial portion covering at least a portion of the surface of the auxiliary structural layer; depositing a main structural layer on the auxiliary structural layer, the second sacrificial layer, and the first sacrificial layer; etching the main structural layer above the second sacrificial portion to form a first opening; and etching the first sacrificial portion and the second sacrificial portion through the first opening to form the release channel.

[0025] In other embodiments, the preparation method further includes: depositing a second sacrificial layer on the auxiliary structural layer using a conformal deposition process, so that the second sacrificial layer forms a recessed structure at the second opening; when depositing a main structural layer on the auxiliary structural layer, the second sacrificial layer and the first sacrificial layer, the main structural layer covers the recessed structure, such that the main structural layer faces the surface of the first cavity and forms a protrusion facing the second opening at the recessed structure.

[0026] In some other embodiments, the thickness of the second sacrificial portion is 0.02 μm to 0.5 μm; and / or the thickness of the auxiliary structural layer is 0.1 μm to 0.5 μm.

[0027] In some embodiments, the width of the first opening is 1 μm to 5 μm; the width of the first opening is smaller than the width of the second opening.

[0028] In other embodiments, the first structural layer includes a first electrode layer, a first dielectric layer, and a second electrode layer stacked together; before depositing a first sacrificial layer on the first structural layer, the fabrication method further includes: depositing a first dielectric layer on the first electrode layer; etching the first dielectric layer until the first electrode layer is exposed to form a third opening on the first dielectric layer; and depositing a second electrode layer on the first dielectric layer such that the second electrode layer covers at least a portion of the surface of the first dielectric layer and fills the third opening to connect with the first electrode layer.

[0029] In some other embodiments, before depositing the first sacrificial layer on the first structural layer, the fabrication method further includes: providing a third structural layer; depositing the third sacrificial layer on the third structural layer; forming the first structural layer on the third sacrificial layer; etching the first structural layer until the third sacrificial layer is exposed to form a plurality of fourth openings, such that when the first sacrificial layer is deposited on the first structural layer, the first sacrificial layer fills the plurality of fourth openings.

[0030] In some embodiments, the fabrication method further includes: etching at least a portion of the first sacrificial layer and the third sacrificial layer at locations corresponding to the fourth opening to form a connecting hole between the second structural layer and the third structural layer; depositing a second dielectric layer on the first sacrificial layer such that the second dielectric layer covers the surface of the first sacrificial layer and fills the connecting hole; etching the second dielectric layer to retain the second dielectric layer in the connecting hole to form a connecting post.

[0031] In other embodiments, the fabrication method further includes: before depositing the host structural layer, etching the surface of the first sacrificial layer facing the second structural layer to form at least one first groove, the at least one first groove including a first annular groove surrounding the connecting post; during the deposition of the host structural layer, the host structural layer fills the at least one first groove to form at least one first conductive post on the surface of the second structural layer facing the first structural layer, the at least one first conductive post including a first annular conductive post surrounding the connecting post.

[0032] In some other embodiments, the third sacrificial layer includes a first sacrificial sublayer and a second sacrificial sublayer. Depositing the third sacrificial layer on the third structural layer includes: depositing a first sacrificial sublayer on the third structural layer; etching the first sacrificial sublayer until the third structural layer is exposed to form at least one second groove, wherein the at least one second groove includes a second annular groove; depositing a conductive layer on the first sacrificial sublayer such that the conductive layer covers the surface of the first sacrificial sublayer and fills the at least one second groove up to the surface of the third structural layer; removing the conductive layer from the surface of the first sacrificial sublayer, retaining the conductive layer deposited in the at least one second groove to form at least one second conductive pillar on the third structural layer, wherein the at least one second conductive pillar includes a second annular conductive pillar; and depositing a second sacrificial sublayer on the surface of the first sacrificial sublayer and on the surface of the second conductive pillar facing the first structural layer.

[0033] In some embodiments, the preparation method further includes: when etching the surface of the first sacrificial layer facing the second structural layer, the first groove and the second groove are symmetrically distributed.

[0034] In other embodiments, the width of the first annular groove is 0.3 μm to 1 μm.

[0035] With the MEMS structure provided above, the embodiments of this application stagger the first opening and the second opening in the thickness direction of the second structural layer, and connect the first opening and the second opening through a lateral gap to form a non-vertical release channel. This can prevent the sealing layer material from being deposited directly onto the surface of the first structural layer through the release channel to form a protrusion when the sealing layer is deposited, thereby avoiding the protrusion from restricting the movement space of the second structural layer and thus improving the performance of the MEMS device.

[0036] Furthermore, in some preferred embodiments, by extending the sealing layer onto the auxiliary structural layer to seal the lateral gap, the sidewall effect can be utilized to naturally form a sealed structure without additional photolithography steps, avoiding complex processes such as photolithography and resist removal on the fragile structure with the already formed cavity, thereby improving the manufacturing yield and device reliability of MEMS devices. Attached Figure Description

[0037] The above and other objects, features, and advantages of exemplary embodiments of this application will become readily understood by reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of this application are illustrated by way of example and not limitation, and the same or corresponding reference numerals denote the same or corresponding parts, wherein:

[0038] Figure 1 This illustrates an existing MEMS structure; Figure 2A Schematic diagrams of MEMS structures according to some embodiments of this application are shown; Figure 2B Schematic diagrams of MEMS structures according to other embodiments of this application are shown; Figure 3 An exemplary flowchart of a method for fabricating a MEMS structure according to some embodiments of this application is shown; Figures 4A-4G The following are schematic diagrams illustrating the fabrication process of MEMS structures according to some embodiments of this application; Figures 5A-5C The following are schematic diagrams illustrating the fabrication process of MEMS structures including protrusions according to some embodiments of this application; Figures 6A to 6N A schematic diagram illustrating the fabrication process of a MEMS structure according to some embodiments of this application is shown. Detailed Implementation

[0039] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0040] It should be understood that the terms "comprising" and "including" used in the specification and claims of this application indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0041] It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application. As used in this specification and claims, 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 term “and / or” as used in this specification and claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations.

[0042] In the description of this application, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the present invention.

[0043] The specific embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0044] Figure 2A Schematic diagrams of MEMS structures according to some embodiments of this application are shown. For example... Figure 2A As shown, the MEMS structure includes a first structural layer 210 and a second structural layer 220; wherein, a spacer layer 230 is provided between the second structural layer 220 and the first structural layer 210 to form a first cavity 240 between the second structural layer 220 and the first structural layer 210, the second structural layer 220 includes a main structural layer 221 and an auxiliary structural layer 222, the main structural layer 221 and the auxiliary structural layer 222 are contacted and connected at at least one first region 223, and separated from each other at at least one second region to form a lateral gap 224, wherein... A first opening 2211 is provided on the main structural layer 221. An auxiliary structural layer 222 is provided on the side of the first opening 2211 facing the first cavity 240. A second opening 2221 is provided on the auxiliary structural layer 222. The first opening 2211 and the second opening 2221 are offset in the thickness direction Z of the second structural layer 220. When the first opening 2211 and the second opening 2221 are connected by a transverse gap 224, a release channel is formed (as shown by the dashed arrow in the figure). A sealing layer 250 is located at the release channel to seal the release channel.

[0045] In some embodiments, the first structural layer 210 may be a bottom support layer, substrate, or backplane layer of a MEMS structure, and may include one or more combinations of single-crystal silicon layers, polycrystalline silicon layers, silicon nitride layers, silicon oxide layers, or dielectric layers. The spacer layer 230 may be a layer of materials such as silicon oxide or silicon nitride. The presence of the spacer layer 230 maintains a certain distance between the second structural layer 220 and the first structural layer 210, thereby forming a first cavity 240 between them. The first cavity 240 may be a closed air cavity or vacuum cavity, used by MEMS structures (such as pressure sensors, microphones, etc.) to sense external signals or provide movement space.

[0046] The first region of contact connection and the second region of separation between the main structural layer 221 and the auxiliary structural layer 222 are two spatial relationships that coexist. Specifically, the first region refers to those areas where the main structural layer 221 and the auxiliary structural layer 222 are in spatial contact and physically connected. In these regions, the two structures are directly bonded or connected through a supporting structure without gaps. The main structural layer 221 and the auxiliary structural layer 222 are in contact and physically connected at least in at least one first region 223. This contact connection can take various forms, such as point contact (e.g., connected through one or more discrete support points), line contact (e.g., connected through a continuous edge or ridge), or surface contact (e.g., directly bonded through a continuous planar region). The specific contact form can be selected based on the mechanical strength requirements, electrical connection requirements, or manufacturing process feasibility of the MEMS structure.

[0047] Meanwhile, the second region refers to the areas where the main structural layer 221 and the auxiliary structural layer 222 are spatially separated and not in direct contact. In these regions, gaps exist between the two layers, forming transverse gaps 224, which are an important component of the release channel. The transverse gap 224 is a slot extending along a plane perpendicular to the thickness direction Z, and its width can be precisely controlled through the manufacturing process.

[0048] This arrangement, which connects the first region and separates the second region, ensures that the main structural layer 221 and the auxiliary structural layer 222 maintain the overall mechanical stability of the structure while providing the necessary spatial path for forming a non-vertical release channel.

[0049] A first opening 2211 is provided on the main structural layer 221, and a second opening 2221 is provided on the auxiliary structural layer 222. The auxiliary structural layer 222 is located on the side of the first opening 2211 facing the first cavity 240, that is, the auxiliary structural layer 222 is located below the first opening 2211 (on the side closer to the first structural layer 210). The first opening 2211 and the second opening 2221 are offset in the thickness direction Z of the second structural layer 220, that is, the central axis of the first opening 2211 and the central axis of the second opening 2221 do not coincide in the horizontal direction, but have a certain offset. The first opening 2211 and the second opening 2221 are connected by a transverse gap 224, forming a non-vertical, tortuous release channel (as shown by the dashed arrow in the figure). The path of this release channel is: entering from the first opening 2211, extending horizontally through the transverse gap 224, and then extending downward through the second opening 2221 to the first cavity 240.

[0050] A sealing layer 250 is located at the release channel to seal the release channel. Specifically, the sealing layer 250 may be deposited at the entrance of the release channel (e.g., Figure 2AThe first opening 2211 shown in the diagram) or inside the channel (such as at the transverse gap 224) is used to block the release channel, isolating the first cavity 240 from the outside. For example, Figure 2B Schematic diagrams of MEMS structures according to other embodiments of this application are shown. Figure 2A compared to, Figure 2B The difference in the MEMS structure shown is that the sealing layer 250 seals the lateral gap 224 to achieve the purpose of sealing the release channel.

[0051] like Figure 2B As shown, the sealing layer 250 can cover the inner wall of the first opening 2211 and extend along the thickness direction Z of the second structural layer 220 to the auxiliary structural layer 222 corresponding to the first opening 2211 to seal the transverse gap 224.

[0052] The term "covering the inner wall of the first opening 2211" refers to the deposition of the sealing layer 250 on the sidewall surface of the first opening 2211 of the main structural layer 221, forming a sidewall covering layer extending along the thickness direction Z. Simultaneously, the sealing layer 250 extends downwards from the inner wall of the first opening 2211, passes through the transverse gap 224, and finally reaches the upper surface of the auxiliary structural layer 222. Thus, the sealing layer 250 forms a continuous sidewall sealing structure.

[0053] It is important to understand that since the sealing layer 250 is only formed on the sidewall of the first opening 2211, the cross-section of the transverse gap 224, and the corresponding area of ​​the auxiliary structural layer 222, while the remaining area on the upper surface of the main structural layer 221 is completely cleaned, the patterning of the sealing layer can be completed without additional photolithography and resist removal steps, simplifying the process. Secondly, since the sealing layer 250 extends along the Z-direction, it does not occupy additional area in the horizontal direction, thus ensuring the compactness of the MEMS structure. In addition, the seal formed by the sidewall structure has better mechanical stability and is less prone to detachment or breakage under stress, improving the long-term reliability of the MEMS device.

[0054] Furthermore, such as Figure 2A and Figure 2B As shown, in some embodiments, the main structural layer 221 is disposed on the spacer layer 230, and in a plane perpendicular to the thickness direction Z of the second structural layer 220, the projection of the main structural layer 221 overlaps with that of the spacer layer 230, while the projection of the auxiliary structural layer 222 does not overlap with that of the spacer layer 230.

[0055] The projection in the plane perpendicular to the thickness direction Z here refers to the projected outline of each structural layer on the horizontal plane from a two-dimensional perspective viewed from the top of the MEMS structure. The overlapping of the projected portions of the main structural layer 221 and the spacer layer 230 means that, in the top-view plane, a portion of the main structural layer 221 coincides with at least a portion of the spacer layer 230, i.e., the main structural layer 221 covers at least a portion of the spacer layer 230.

[0056] In contrast, the non-overlapping projections of the auxiliary structural layer 222 and the spacer layer 230 mean that the projected outline of the auxiliary structural layer 222 in the top view plane does not intersect with the projected outline of the spacer layer 230 at all. That is, the auxiliary structural layer 222 is located outside the coverage area of ​​the spacer layer 230 in the horizontal direction. In other words, the auxiliary structural layer 222 is offset in the horizontal direction from the area directly above the spacer layer 230, so that it does not overlap with the spacer layer 230 in the vertical direction.

[0057] Through the above combination Figure 2A and Figure 2B As described above, because the release channel in the MEM structure of this application embodiment is a non-perpendicular tortuous path, the sealing layer 250 is not deposited directly onto the surface of the first structural layer 210 in a vertical direction during deposition, thereby effectively preventing the sealing material from forming protrusions on the surface of the first structural layer 210. This prevents device performance degradation caused by protrusions occupying the movement space; for example, in a pressure sensor, it does not restrict the downward deformation of the top structural layer, thus ensuring the measurement range and linearity.

[0058] To further understand the technical solution of this application, the following will be combined with... Figures 3-4G The preparation method is further explained.

[0059] Figure 3 An exemplary flowchart illustrating the fabrication method of MEMS structures according to some embodiments of this application is shown. Figure 3As shown, the preparation method 300 includes: in step S301, depositing a first sacrificial layer on a first structural layer; in step S302, forming an auxiliary structural layer with a second opening on the first sacrificial layer; in step S303, forming a main structural layer with a first opening on the auxiliary structural layer, and contacting and connecting the main structural layer and the auxiliary structural layer at at least one first region, separating them from each other at at least one second region to form a lateral gap, wherein the first opening and the second opening are offset in their thickness direction so as to form a release channel through the first opening, the lateral gap and the second opening; in step S304, using the release channel, etching a portion of the first sacrificial layer to form a first cavity between the second structural layer composed of the auxiliary structural layer and the main structural layer and the first structural layer, wherein the unetched portion of the first sacrificial layer constitutes a spacer layer between the first structural layer and the second structural layer; and in step S305, sealing the release channel.

[0060] To facilitate understanding, the following will combine... Figures 4A-4G The preparation method 300 is further described.

[0061] Figures 4A-4G Schematic diagrams illustrating the fabrication process of MEMS structures according to some embodiments of this application are shown. For example... Figure 4A As shown, firstly, a first sacrificial layer 401 is deposited on the first structural layer 210. Then, an auxiliary structural layer 222 with a second opening 2221 is formed on the first sacrificial layer 401. The material of the first sacrificial layer 401 is preferably silicon oxide (SiO2), but other materials with a good etching selectivity to the structural layer to be retained can also be used. The deposition of the first sacrificial layer 401 can be performed using chemical vapor deposition (CVD) processes, such as plasma-enhanced chemical vapor deposition (PE-CVD) or low-pressure chemical vapor deposition (LP-CVD) or a combination of both, to form a uniform and thickness-controllable thin film on the surface of the first structural layer 210. The thickness of the first sacrificial layer 401 on the surface of the first structural layer 210 determines the height of the final formed first cavity 240, which can usually be precisely controlled according to the design requirements of the MEMS structure, for example, it can be selected between 1 μm and 3 μm.

[0062] The auxiliary structural layer 222 is a component of the second structural layer, and its material can be one or more of silicon nitride, polysilicon, TiW, Cr, TiN, Ta, and TaN, or a combination of two or more of these materials. The formation process of the auxiliary structural layer 222 may include: firstly, depositing an auxiliary structural layer material on the surface of the first sacrificial layer 401 using, for example, an LP-CVD process; then, etching a pattern for the second opening 2221 on the surface of the auxiliary structural layer material using, for example, a photolithography process; and finally, removing the material in the corresponding area using a dry or wet etching process, thereby forming the second opening 2221 penetrating the auxiliary structural layer 222. In some embodiments, the thickness of the auxiliary structural layer 222 is 0.1 μm to 0.5 μm. Exemplarily, the thickness of the auxiliary structural layer 222 can be 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, or other values ​​within the range of 0.1 μm to 0.5 μm.

[0063] In other embodiments, the second opening 2221 can be a hole-like structure. The second opening 2221 can be a circular hole, a square hole, or an opening of other geometric shapes. The size of the second opening 2221 needs to be determined based on the overall design of the release channel, and its diameter or width is typically on the order of micrometers, for example, 1 μm to 10 μm. The position of the second opening 2221 needs to be horizontally offset from the subsequently formed first opening 2211 so that the two are connected through a lateral gap 224 to form a non-vertical release channel. Therefore, during the photolithography pattern design stage, the horizontal coordinates of the second opening 2221 need to be precisely controlled.

[0064] Next, in such Figure 4A After completing step S302, step S303, forming the release channel, can be performed. In some embodiments, such as... Figure 4B As shown, a second sacrificial layer 402 is deposited on the auxiliary structural layer 222. The second sacrificial layer 402 is a temporary material layer for the subsequent formation of lateral gaps. The material can be, for example, silicon oxide (SiO2) or other materials with a good etch selectivity ratio to the auxiliary structural layer 222 and the subsequent host structural layer 221. The deposition process can be, for example, chemical vapor deposition (CVD), specifically including plasma-enhanced chemical vapor deposition (PE-CVD) or low-pressure chemical vapor deposition (LP-CVD).

[0065] During deposition, the second sacrificial layer 402 covers the upper surface of the auxiliary structure layer 222 and fills the second opening 2221 on the auxiliary structure layer 222, thereby forming a thin film of uniform thickness within the second opening 2221 and on the surface of the auxiliary structure layer 222. The thickness of the second sacrificial layer 402 determines the height of the subsequently formed lateral gap 224, so submicron thicknesses can be achieved by precisely controlling deposition parameters (such as deposition time, temperature, pressure, etc.). In some embodiments, the thickness of the second sacrificial layer 402 on the surface of the auxiliary structure layer 222 is 0.02 μm to 0.5 μm, thereby obtaining a lateral gap with a thickness of 0.02 μm to 0.5 μm. For example, the thickness of the second sacrificial layer 402 on the surface of the auxiliary structure layer 222 can be 0.02μm, 0.05μm, 0.1μm, 0.15μm, 0.2μm, 0.25μm, 0.3μm, 0.35μm, 0.4μm, 0.45μm, 0.5μm, or other values ​​in the range of 0.02μm to 0.5μm.

[0066] By depositing the second sacrificial layer 402, a sacrificial space-occupying layer can be pre-set above the auxiliary structural layer 222. This layer will be completely removed in subsequent processes, thereby forming a transverse gap 224 between the main structural layer 221 and the auxiliary structural layer 222, providing the necessary physical space for the formation of the release channel.

[0067] After the second sacrificial layer 402 is deposited, it can be etched, such as... Figure 4C As shown, a first sacrificial portion 4021 covering the second opening 2221 and a second sacrificial portion 4022 covering at least a portion of the surface of the auxiliary structural layer 222 are retained.

[0068] Etching the second sacrificial layer 402 allows for the selective removal of material from certain areas while retaining material from specific regions. This etching process typically includes the following steps: First, photoresist is coated onto the surface of the second sacrificial layer 402, and a photoresist mask with a specific pattern is formed through an exposure and development process. This mask covers the areas of the second sacrificial layer that need to be retained, namely the locations of the first sacrificial portion 4021 and the second sacrificial portion 4022. Subsequently, dry etching (e.g., reactive ion etching) or wet etching is used to remove the second sacrificial layer material not covered by the photoresist mask until the surface of the underlying auxiliary structural layer 222 or the first sacrificial layer 401 is exposed. Finally, the remaining photoresist mask is removed, completing the patterned etching.

[0069] The aforementioned first sacrificial portion 4021 refers to the portion of the second sacrificial layer retained inside the second opening 2221. Specifically, the first sacrificial portion 4021 fills the second opening 2221, covering its inner wall and bottom. Since the first sacrificial portion 4021 occupies the internal space of the second opening 2221, it will be removed in subsequent processes, thus forming part of the release channel. The second sacrificial portion 4022 refers to the portion of the second sacrificial layer retained on the upper surface of the auxiliary structural layer 222. The second sacrificial portion 4022 is located above the auxiliary structural layer 222, covering at least a portion of its surface, and its thickness is the height (or thickness) of the subsequently formed transverse gap 224. The shape and extent of the second sacrificial portion 4022 can be adjusted according to the design requirements of the release channel; for example, it can be retained as an annular region surrounding the second opening 2221, or as a discrete block corresponding to the position of the first opening 2221.

[0070] Through the etching process described above, the second sacrificial layer 402 is divided into two functionally distinct retention areas: First, by retaining the first sacrificial portion 4021, it can be ensured that the second opening 2221 remains unobstructed during the subsequent deposition of the main structural layer 221, preventing it from being filled by the main structural layer material, thus preserving a complete path for the formation of the release channel; second, by retaining the second sacrificial portion 4022, a precise gap can be pre-defined between the main structural layer 221 and the auxiliary structural layer 222, the thickness of which is determined by the thickness of the second sacrificial portion 4022, thereby determining the thickness of the lateral gap. Furthermore, the portion of the auxiliary structural layer 222 exposed by the etching process of the second sacrificial layer 402 can be used for subsequent contact connection with the main structural layer. Moreover, this selective retention process requires only one photolithography and etching step, resulting in low process cost and high efficiency.

[0071] Next, as Figure 4D As shown, the main structure layer 221 can be deposited on the auxiliary structure layer 222, the second sacrificial layer and the first sacrificial layer 401; and the main structure layer 221 above the second sacrificial portion 4022 can be etched to form the first opening 2211.

[0072] In some embodiments, the material of the main structural layer 221 may be selected from monocrystalline silicon, polycrystalline silicon, silicon nitride, silicon oxide, or a combination thereof, or may be a metallic material such as TiW, Cr, TiN, Ta, TaN, etc. The deposition of the main structural layer 221 may employ chemical vapor deposition (CVD) processes, such as low-pressure chemical vapor deposition (LP-CVD) or plasma-enhanced chemical vapor deposition (PE-CVD), to form a continuous and uniform structural layer on the surfaces of the auxiliary structural layer 222, the second sacrificial layer (such as the surface of the second sacrificial portion 4022), and the first sacrificial layer 401.

[0073] After depositing the main structural layer 221, a first opening 2211 needs to be formed on it. The formation process of the first opening 2211 can be achieved, for example, by photolithography. By controlling the etching time or using endpoint detection technology, the etching can be precisely stopped on the surface of the second sacrificial portion 4022, avoiding over-etching and damage to the auxiliary structural layer 222.

[0074] The first opening 2211 needs to be staggered from the second opening 2221 in the horizontal direction. This staggered arrangement can be achieved through the pattern design on the photomask. For example, when designing the photomask, the pattern of the first opening 2211 is arranged in the adjacent area of ​​the second opening 2221, ensuring that the two are staggered by a certain distance in the horizontal direction.

[0075] In some embodiments, the first opening 2211 is a groove-shaped structure or a hole-shaped structure. For example, the shape of the first opening 2211 can be a circular hole, a square hole, or a groove-shaped structure, and its width or diameter can be between 1 μm and 5 μm. The number of first openings 2211 can be one or more. When the first opening 2211 is a groove-shaped structure, it can be a linear groove or an arc-shaped groove surrounding the second opening 2221, etc. The width of the first opening 2211 refers to the lateral dimension of the first opening as shown in the cross-sectional view of the MEMS structure in the figure. Exemplarily, the width or diameter of the first opening 2211 can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, etc., or other values ​​in the range of 1 μm to 5 μm.

[0076] The size of the first opening 2211 can be smaller or larger than the size of the second opening 2221, depending on the fluid characteristics of the release channel and the requirements of the sealing process. In a preferred embodiment, the width of the first opening 2211 is smaller than the width of the second opening 2221, thereby making the inlet end (first opening 2211) of the release channel smaller, which helps to reduce the thickness requirement of the subsequent sealing layer deposition.

[0077] Through the first opening 2211, the first sacrificial portion 4021 and the second sacrificial portion 4022 are etched to form such a Figure 4EThe diagram shows a release channel connected by a first opening 2211, a transverse gap 224, and a second opening 2221. The first opening 2211 serves as the inlet of the release channel, and its position and size directly determine the deposition position and sealing effect of the subsequent sealing layer. Because the first opening 2211 and the second opening 2221 are horizontally offset and connected through the transverse gap 224 formed between the main structural layer 221 and the auxiliary structural layer 222, a non-vertical tortuous release channel is constructed. The size of the transverse gap 224 is much smaller than the aperture of a traditional vertical release hole. Furthermore, the control over the size of the first opening allows the sealing layer to fill only the first opening and block the cross-section extending from the transverse gap during deposition, without needing to cover a large area of ​​the vertical hole wall. This significantly reduces the requirements for the sealing layer thickness, greatly simplifies the sealing process, and reduces the process difficulty.

[0078] Furthermore, such as Figure 4E As shown, while forming the release channel, a portion of the first sacrificial layer 401 can be etched using this release channel to form a first cavity 240 between the second structural layer (composed of the auxiliary structural layer 222 and the main structural layer 221) and the first structural layer 210, thus completing step S304. The portion of the first sacrificial layer that is not etched constitutes the spacer layer 230 between the first and second structural layers.

[0079] The corrosion treatment described above refers to introducing a corrosive agent through the release channel, allowing it to contact the second sacrificial layer and the first sacrificial layer 401, and selectively removing the parts of the second sacrificial layer and the first sacrificial layer 401 that need to be removed. This can be achieved, for example, through wet corrosion or vapor phase corrosion processes. The corrosive agent penetrates along the release channel to the surface of the first sacrificial layer 401, reacts chemically with the material of the first sacrificial layer, and is then discharged after being converted into soluble or volatile products. After etching, the area removed from the first sacrificial layer 401 forms the first cavity 240, which is located between the second structural layer and the first structural layer 210, providing necessary space for the moving parts of the MEMS device (such as diaphragms or movable electrodes). The unetched portion of the first sacrificial layer 401 remains in place, forming the spacer layer 230 between the first structural layer 210 and the second structural layer. The spacer layer 230 supports the second structural layer 220 in the horizontal direction, ensuring that the second structural layer 220 and the first structural layer 210 maintain a predetermined distance, thereby maintaining the shape and dimensional stability of the first cavity 240.

[0080] Through the above-mentioned etching process, a release channel can be formed simultaneously, the first cavity 240 can be formed and the spacer layer 230 can be retained without additional masking or etching steps, thereby simplifying the manufacturing process and ensuring the consistency and reliability of the structure.

[0081] In some embodiments, step S302 may further include: forming an auxiliary structural layer with a second opening on the surface of the intermediate region of the first sacrificial layer; step S304 may further include: etching the intermediate region of the first sacrificial layer while etching a portion of the first sacrificial layer. That is to say, in such... Figure 4A As shown, by etching the auxiliary structure layer, the auxiliary structure layer 222 with the second opening 2221 is located on the surface of the middle region of the first sacrificial layer 401, thereby achieving the desired effect. Figure 4E After the etching process shown, the middle region of the first sacrificial layer is removed, so that the projections of the auxiliary structural layer 222 and the spacer layer 230 do not overlap, while the projections of the main structural layer 221 and the spacer layer 230 partially overlap.

[0082] Furthermore, such as Figure 4F As shown, a sealing layer 250 can be deposited on the surface of the main structural layer 221, which at least covers the first opening 2211. The material of the sealing layer 250 can be selected from silicon oxide, silicon nitride, aluminum oxide, polycrystalline silicon, or a combination of two or more of them. These materials have good density and etching selectivity, and can effectively block the penetration of gas or liquid. The sealing layer 250 can be deposited using methods such as plasma-enhanced chemical vapor deposition (PE-CVD), low-pressure chemical vapor deposition (LP-CVD), or atomic layer deposition (ALD). Among these methods, PE-CVD is often chosen because of its lower deposition temperature and better process compatibility.

[0083] The deposition thickness of the sealing layer 250 needs to be selected based on the geometry of the release channel. Specifically, the deposition thickness should be at least sufficient to cover and seal the first opening 2211. After this sealing step, the sealing pressure of the first cavity 240 is equal to the process pressure during the deposition of the sealing layer 250.

[0084] In some embodiments, after the sealing layer 250 is deposited, the sealing layer 250 can be patterned using a photolithography process to retain the sealing layer at the first opening 2211, resulting in the following: Figure 2A The MEMS structure shown.

[0085] In other embodiments, such as Figure 4G As shown, when depositing the sealing layer 250, it can fill the first opening 2211 and extend from the first opening 2211 to the surface of the auxiliary structural layer 222. In order to ensure the deposition thickness of the sealing layer 250 in the first opening 2211 and the lateral gap, the thickness of the sealing layer 250 on the surface of the main structural layer 221 can be controlled to reach 0.5~1μm.

[0086] exist Figure 4GBased on the structure shown, a photomask-free etching process can be used to etch the sealing layer 250 to retain the inner wall covering the first opening 2211 and extending to the auxiliary structural layer 222 based on the sidewall effect, thereby sealing the lateral gap and obtaining the desired result. Figure 2B The MEMS structure shown is shown in the figure.

[0087] The maskless etching process here refers to uniform etching of the entire wafer surface without using a photoresist mask. This process utilizes the anisotropic properties of the etching gas, resulting in different etching rates for materials on surfaces with different orientations. In MEMS manufacturing, maskless etching typically employs dry etching techniques such as reactive ion etching (RIE) or inductively coupled plasma etching (ICP). By controlling parameters such as the composition, pressure, power, and temperature of the etching gas, selective removal of the sealing layer material can be achieved.

[0088] In anisotropic etching, etching ions act perpendicularly to the wafer surface, causing the material on the horizontal surface to be rapidly etched away, while the material on the vertical or inclined sidewall surfaces is retained due to the geometric shielding effect; this phenomenon is called the sidewall effect. Specifically, when etching gas ions are incident perpendicularly to the wafer surface... Figure 4G When the sealing layer 250 surface is exposed to vertically downward etching ions, the sealing layer material in the horizontal direction is rapidly removed. However, since the sidewall surface is parallel to the ion incident direction, the etching ions are geometrically shielded, and the sealing layer 250 on the sidewall surface is hardly etched. Therefore, the sealing layer material on the sidewall is retained.

[0089] During the actual etching process, the portion of the sealing layer 250 located on the upper surface of the main structural layer 221, being horizontally oriented, is completely removed by the etching gas. However, the sealing layer 250 located on the inner wall of the first opening 2211, being vertically or nearly vertically oriented, is protected by the sidewall effect and is retained. Simultaneously, since the inner wall of the first opening 2211 is connected to the upper surface of the auxiliary structural layer 222 via a transverse gap 224, the sealing layer 250 retained on the inner wall of the first opening 2211 extends downwards along the thickness direction Z of the second structural layer, passes through the transverse gap 224, and finally covers the area on the auxiliary structural layer 222 corresponding to the first opening 2211, thus forming a complete and continuous sidewall sealing structure. This sealing structure covers the inlet end of the transverse gap 224's cross-section, effectively blocking the release channel.

[0090] In this embodiment, the use of a photomask-free etching process eliminates the need for additional photolithography steps to define the pattern of the sealing layer 250, thus saving a series of processes such as resist coating, exposure, development, and resist removal, significantly simplifying the manufacturing process and reducing process costs and cycle time. Simultaneously, it avoids photolithography and resist removal operations on the fragile structure where the first cavity 240 has already been formed, effectively preventing MEMS structure breakage due to mechanical stress or chemical solutions, thereby improving manufacturing yield and device reliability. Furthermore, the sealing layer 250, formed through the sidewall effect, is naturally defined by the geometry of the structure itself, requiring no precise alignment and exhibiting extremely high process consistency. Moreover, the thickness and width of the sealing layer 250 can be precisely controlled through deposition conditions and etching parameters, meeting the sealing requirements of different lateral gap sizes. The final sealed structure is as follows: Figure 2B As shown, the sealing layer 250 is located only on the inner wall of the first opening 2211 and in the corresponding area of ​​the auxiliary structural layer 222, while the upper surface of the main structural layer 221 is fully exposed, providing a clean surface for subsequent contact electrodes or other process steps.

[0091] The above combination Figures 4A-4G right Figure 3 The preparation method shown is described exemplarily. It is understood that the above description is exemplary and not limiting; for example, Figure 4B The second sacrificial layer 402 shown in the diagram may not be limited to completely filling the second opening as illustrated, but may also form a recessed structure at the second opening. For ease of understanding, the following will combine... Figures 5A-5C An exemplary description is provided.

[0092] Figures 5A-5C The illustration shows schematic diagrams illustrating the fabrication process of MEMS structures including protrusions, according to some embodiments of this application. For example... Figure 5A As shown, in such Figure 3 The step S302 shown may further include: depositing a second sacrificial layer 402 on the auxiliary structural layer 222 using a conformal deposition process, so that the second sacrificial layer 402 forms a recessed structure 4023 at the second opening 2221.

[0093] The conformal deposition process here refers to a process method capable of uniformly depositing thin films on complex three-dimensional surfaces, such as low-pressure chemical vapor deposition (LP-CVD) or atomic layer deposition (ALD). Unlike conventional deposition processes, conformal deposition allows the film to grow uniformly along the contour of the surface being deposited, forming a film of consistent thickness on both the horizontal surface and the vertical sidewalls. When the second sacrificial layer 402 is deposited on the auxiliary structural layer 222 using conformal deposition, the second sacrificial layer 402 uniformly covers the upper surface of the auxiliary structural layer 222 as well as the inner wall and bottom of the second opening 2221. Due to the characteristics of conformal deposition, the surface of the second sacrificial layer 402 at the second opening 2221 will exhibit a geometric shape corresponding to the contour of the second opening 2221, forming a downwardly recessed structure 4023. The depth of this recessed structure 4023 is suitable for the depth of the second opening 2221, and its shape and size are determined by the geometry of the second opening 2221, such as a circular recess, a square recess, or a groove-shaped recess.

[0094] Then, as Figure 5B As shown, after etching the second sacrificial layer 402, when depositing the main structure layer 221 on the auxiliary structure layer 222, the second sacrificial layer 402 and the first sacrificial layer 401, the main structure layer 221 covers the recessed structure 4023, such that the main structure layer 221 faces the surface of the first cavity 240, and a protrusion 2212 facing the second opening 2221 is formed at the recessed structure 4023.

[0095] During the deposition of the main structural layer 221, the material of the main structural layer 221 fills the recessed structure 4023, thereby forming a geometry complementary to the recessed structure 4023 on the lower surface of the main structural layer 221 (i.e., the surface facing the first cavity 240). Specifically, when the main structural layer 221 is deposited on the second sacrificial layer 402 containing the recessed structure 4023, the lower surface of the main structural layer 221 conforms to the contour of the recessed structure 4023, thereby forming a protrusion 2212 protruding towards the second opening 2221 at the corresponding position. The shape of the protrusion 2212 corresponds to the shape of the recessed structure 4023, for example, it can be a circular protrusion, an annular protrusion, or a columnar protrusion. In some embodiments, a conformal deposition process can also be used to deposit the main structural layer 221, in which case a recessed structure can also be formed on the surface of the protrusion 2212 facing away from the auxiliary structural layer 222.

[0096] Furthermore, in such Figure 5B Based on the structure shown, after the corrosion treatment in step S304 and the sealing treatment in step S305 (e.g.) Figure 4G After the sealing process shown, for example, you can obtain... Figure 5CThe MEMS structure shown is described above. In this MEMS structure, the main structural layer 221 has a protrusion structure 2212 facing the surface of the first cavity 240 at a position corresponding to the second opening 2221.

[0097] Specifically, in the corrosion treatment of step S304, the second sacrificial layer 402 is completely removed, while a portion of the first sacrificial layer 401 is also removed, forming the first cavity 240. At this time, the protruding structure 2212 is exposed in the first cavity 240, facing the location of the second opening 2221. Due to the presence of the protruding structure 2212, the gap between the main structural layer 221 and the auxiliary structural layer 222 becomes narrower at the protruding structure 2212, thereby further reducing the local size of the release channel. In the sealing treatment of step S305, the sealing layer 250 is deposited and blocks the release channel. The narrow gap near the protruding structure 2212 makes it easier for the sealing layer 250 to complete the sealing, reducing the requirement for the thickness of the sealing layer.

[0098] It is also understandable that by conformally depositing the second sacrificial layer 402 and forming the protrusion structure 2212 using the recessed structure 4023, the required protrusion structure can be naturally formed on the main structural layer 221 without adding additional photolithography steps, thus simplifying the manufacturing process. Secondly, the presence of the protrusion structure 2212 can further reduce the effective opening size of the release channel, making it easier for the sealing layer 250 to block the channel during deposition, reducing the requirement for the thickness of the sealing layer. In addition, the correspondence between the protrusion structure 2212 and the second opening 2221 allows the protrusion structure 2212 to act as a guide or current limiter during the release etching process, improving the uniformity and controllability of the etching process. Finally, for applications such as dual-diaphragm microphones or pressure sensors, the protrusion structure 2212 can serve as an additional electrode structure to enhance the electric field distribution or improve capacitive sensitivity, thereby improving device performance. In summary, this embodiment achieves the natural formation of the protrusion structure through simple conformal deposition, which simplifies the process and improves device performance.

[0099] The above text combined Figures 2A to 5C This application describes in detail the MEMS structural features of some embodiments, such as release channels and sealing methods. It is understood that the above structures and fabrication steps are exemplary, and this application also provides other implementations of the MEMS structure to further expand the application scope and performance of the MEMS structure. The following will combine... Figure 6A The accompanying figures and subsequent figures provide a detailed description of optional additional structures in the MEMS structure (such as third structural layers, connecting pillars, conductive pillars, etc.) and their formation methods. These features can be combined with the aforementioned release channels and sealing structures to achieve more complex device configurations, such as dual-diaphragm microphones, thereby further improving the device's sensitivity, mechanical stability, or electrical performance.

[0100] Figures 6A to 6N Schematic diagrams illustrating the fabrication process of MEMS structures according to some embodiments of this application are shown. For example... Figure 6A As shown, firstly, a substrate 610 can be provided, and a third dielectric layer 620 is deposited on the surface of the substrate 610; then, a third structural layer 630 is formed on the third dielectric layer 620. The substrate 610 is the starting base for the MEMS manufacturing process; for example, it can be a single-crystal silicon wafer, whose surface is cleaned and planarized to provide a clean interface for subsequent thin film deposition. The third dielectric layer 620 is deposited on the surface of the substrate 610, and its material can be silicon oxide, silicon nitride, or a combination of both. It can be formed using thermal oxidation or chemical vapor deposition (CVD) processes, and its thickness is, for example, between 0.2 micrometers and 1.5 micrometers. Its function is to electrically isolate the subsequently formed third structural layer 630 from the substrate 610, preventing the generation of parasitic capacitance or leakage current, and it can also serve as a stop layer or sacrificial layer base for subsequent etching processes.

[0101] The third structural layer 630 can be formed on top of the third dielectric layer 620 using a low-pressure chemical vapor deposition (LP-CVD) process. The material can be polycrystalline silicon, silicon nitride, metal, or a combination thereof. The thickness of the third structural layer 630 can be, for example, 0.3 μm to 1 μm. The third structural layer 630 provides mechanical support and electrical functionality for MEMS structures. For example, in a dual-diaphragm microphone application, the third structural layer 630 can serve as a bottom fixed electrode or lower diaphragm structure, providing a mechanical basis for the subsequent formation of a second cavity and a movable diaphragm.

[0102] like Figure 6A As further illustrated, in some embodiments, the third structural layer 630 may be etched (e.g., patterned etching) to form at least one through-hole 631 to expose the third dielectric layer 620. In other embodiments, the through-hole 631 may be a hole-shaped structure, such as a circular hole or a square hole. The diameter or width of the through-hole 631 may be, for example, 2 μm to 20 μm. The through-hole 631 can be used as a drainage channel for the etchant in subsequent etching processes.

[0103] Next, a third sacrificial layer can be deposited on the third structural layer 630. The third sacrificial layer may include one or more sacrificial layers. Figures 6B-6E A schematic diagram illustrating the formation process of the third sacrificial layer in some embodiments of this application is shown.

[0104] like Figure 6BAs shown, firstly, a first sacrificial sublayer 641 can be deposited on the third structural layer 630; then, the first sacrificial sublayer 641 is etched until the third structural layer 630 is exposed, forming at least one second groove 651, wherein the at least one second groove 651 includes a second annular groove 652.

[0105] The first sacrificial sublayer 641 described herein is part of the third sacrificial layer and is used to occupy space in subsequent processes to form the cavity for the second conductive pillar. The material of the first sacrificial sublayer 641 can be selected from silicon oxide, silicon nitride, or other materials with a good etch selectivity ratio with the subsequent conductive material. Its deposition process can be chemical vapor deposition (CVD), such as plasma-enhanced chemical vapor deposition (PE-CVD) or low-pressure chemical vapor deposition (LP-CVD), or a combination of both. The thickness of the first sacrificial sublayer 641 determines the height of the subsequently formed second conductive pillar, and therefore can be precisely controlled according to the design requirements of the MEMS device, for example, it can be selected between 1 μm and 2 μm. After deposition, its surface typically requires planarization to ensure the accuracy of subsequent photolithography processes.

[0106] By etching the first sacrificial sublayer 641, such as through patterned etching, a second groove 651 is formed at a predetermined location, penetrating the first sacrificial sublayer 641. The bottom of the second groove 651 exposes the surface of the underlying third structural layer 630. The number of second grooves 651 can be one or more, as needed. The diameter or width of the second groove 651 can be 0.3 μm to 1.5 μm. The shape of the second groove 651 can be, for example, a circular hole, a square hole, an annular hole, or a groove-shaped structure.

[0107] In some embodiments, at least one second groove 651 is a second annular groove 652, i.e., a groove structure in the shape of an annular ring. The annular path of the second annular groove 652 can be a circular ring, a square ring, or other closed annular geometry, and its inner and outer diameters can be set according to the size requirements of the subsequently formed second conductive post. In some embodiments, the width of the second annular groove 652 is 0.3 μm to 1 μm. Exemplarily, the width of the second annular groove 652 can be, for example, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, or other values ​​within the range of 0.3 μm to 1 μm. Here, the width of the second annular groove 652 refers to the annular width of the groove (i.e., half the difference between the inner and outer diameters). The formation of the second annular groove 652 requires a corresponding annular pattern on the photomask and is achieved through a precise etching process.

[0108] After the second groove 651 is formed, as follows Figure 6CAs shown, a conductive layer 653 can be deposited on the first sacrificial sublayer 641 such that the conductive layer 653 covers the surface of the first sacrificial sublayer 641 and fills at least one second groove 651 up to the surface of the third structural layer 630.

[0109] The conductive layer 653 here refers to the thin film material used to form subsequent conductive pillars (such as the second conductive pillar). It can be selected from polycrystalline silicon, metals (such as aluminum, titanium, tungsten, copper, etc.), metal compounds (such as titanium nitride, tantalum nitride, etc.), or combinations thereof, and formed through processes such as chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD). The specific process selection depends on the type of conductive material and the required deposition quality. During deposition, the conductive layer 653 not only covers the flat upper surface of the first sacrificial layer 641 but also penetrates and fills the interior of the second groove 651. Since the second groove 651 is an open structure penetrating the first sacrificial layer 641, when the conductive layer 653 is deposited to the bottom of the second groove 651, it directly contacts the exposed surface of the third structural layer 630, thereby forming a continuous conductive path extending downwards from the upper surface of the first sacrificial layer 641 to the third structural layer 630. The deposition thickness of the conductive layer 653 on the surface of the first sacrificial layer 641 typically needs to ensure that the second groove 651 is completely filled. For example, in some embodiments, the conductive layer 653 is deposited on the surface of the first sacrificial layer 641 with a thickness of 0.3 μm to 1 μm.

[0110] By filling the second groove 651 with a conductive layer 653, the conductive layer material in the second groove 651 can be directly connected to the third structural layer 630, forming an electrical path between the subsequent conductive pillar and the third structural layer 630.

[0111] Next, as Figure 6D As shown, the conductive layer on the surface of the first sacrificial sublayer 641 is removed, and the conductive layer deposited in at least one second groove is retained to form at least one second conductive post 654 on the third structural layer 630, the at least one second conductive post 654 including a second annular conductive post 655.

[0112] The conductive layer on the surface of the first sacrificial sublayer 641 can be removed using planarization processes, such as chemical mechanical polishing (CMP) or etch-back processes. This completely removes excess conductive layer material from the upper surface of the first sacrificial sublayer 641, leaving only the conductive layer material filling the second groove 651, thus forming a conductive structure flush with the surface of the first sacrificial sublayer 641. During planarization, the CMP process utilizes the mechanical and chemical action of the polishing slurry and polishing pad to precisely remove the conductive layer on the upper surface of the first sacrificial sublayer 641. The conductive layer material filling the second groove 651 is retained because it is protected by the sidewalls of the first sacrificial sublayer 641. Simultaneously, the CMP process stops at the surface of the first sacrificial sublayer 641, avoiding over-polishing damage to the underlying third structural layer 630.

[0113] The conductive layer retained in the second groove 651 constitutes the second conductive pillar 654. The second conductive pillar 654 extends upward from the surface of the third structural layer 630 to be flush with the upper surface of the first sacrificial layer 641, and its shape is completely consistent with the shape of the second groove 651. When the second groove 651 includes the second annular groove 652, the formed second conductive pillar 654 includes the second annular conductive pillar 655, that is, it is a ring-shaped conductive pillar structure, and the second annular conductive pillar 655 is arranged around its internal central region.

[0114] Furthermore, such as Figure 6E As shown, after removing the conductive layer from the surface of the first sacrificial sublayer 641, a second sacrificial sublayer 642 can be deposited on the surface of the first sacrificial sublayer 641 and on the surface of the second conductive post 654 facing the first structural layer (which is subsequently formed on the third sacrificial layer 640). Here, the surface facing the first structural layer can be the upper surface of the second conductive post 654 in the figure, i.e., the end facing away from the third structural layer 630.

[0115] The second sacrificial sublayer 642 described herein is another component of the third sacrificial layer 640. Its material can be selected from silicon oxide, silicon nitride, or other materials with a good etch selectivity ratio with subsequent structural layers. The deposition process can employ chemical vapor deposition (CVD), such as plasma-enhanced chemical vapor deposition (PE-CVD) or low-pressure chemical vapor deposition (LP-CVD), or a combination of both, to form a uniform thin film on the upper surface of the first sacrificial sublayer 641 and the second conductive pillar 654. The thickness of the second sacrificial sublayer 642 determines the spacing between the subsequently formed first structural layer and the third structural layer 630, and therefore can be precisely controlled according to the design requirements of the MEMS device, for example, it can be selected between 0.3 μm and 1 μm.

[0116] By depositing the second sacrificial sublayer 642, a continuous sacrificial layer surface can be formed above the first sacrificial sublayer 641 and the second conductive pillar 654, providing a flat substrate for the subsequent formation of the first structural layer thereon. At the same time, it ensures that the top of the second conductive pillar 654 is wrapped by the sacrificial layer material to avoid accidental damage or contamination in subsequent processes. In the subsequent release corrosion process, the second sacrificial sublayer 642 will be completely removed to form a second cavity, exposing the top of the second conductive pillar 654 in the second cavity, thereby forming an electrical interaction or capacitive coupling with the upper structural layer.

[0117] At this point, the preparation of the third sacrificial layer 640 (including the first sacrificial sublayer 641 and the second sacrificial sublayer) has been completed. The first structural layer will be formed on the third sacrificial layer 640 next.

[0118] Figures 6F to 6G This illustration shows a schematic diagram of the process of forming a first structural layer on a third sacrificial layer 640 in some embodiments of this application. For example... Figure 6F As shown, firstly, a first electrode layer 661 can be deposited on the third sacrificial layer 640; then, a first dielectric layer 662 is deposited on the first electrode layer 661; next, the first dielectric layer 662 is etched until the first electrode layer 661 is exposed, so as to form a third opening 663 on the first dielectric layer 662.

[0119] The first electrode layer 661 is a component of the backplane electrode layer or intermediate electrode in a MEMS device. Its material can be selected from polysilicon, metals (such as aluminum, titanium, tungsten, etc.), or other conductive materials, and it is formed using processes such as low-pressure chemical vapor deposition (LP-CVD) or physical vapor deposition (PVD). The first electrode layer 661 is deposited on the flat surface of the third sacrificial layer 640, and its thickness can be selected according to the electrical performance requirements of the device, for example, between 0.2 μm and 1 μm.

[0120] The first dielectric layer 662 is deposited on the surface of the first electrode layer 661. Its material can be selected from silicon nitride, silicon oxide, or a combination of both, and is formed by a chemical vapor deposition (CVD) process, such as plasma-enhanced chemical vapor deposition (PE-CVD), low-pressure chemical vapor deposition (LP-CVD), or a combination of both. The thickness of the first dielectric layer 662 can be selected between 0.5 μm and 2 μm. Its function is to provide electrical isolation and mechanical protection for the first electrode layer 661, preventing short circuits between the first electrode layer 661 and other subsequently formed conductive layers. Furthermore, the first dielectric layer 662 typically requires planarization after deposition to ensure its surface flatness meets the requirements of subsequent photolithography processes.

[0121] Etching the first dielectric layer 662 can refer to patterning the first dielectric layer 662 to form a third opening structure penetrating the first dielectric layer 662. The shape of the third opening 663 can be a circular hole, a square hole, or a groove structure, etc., and its size can be selected according to the process requirements of the subsequent conductive filling material. There can be one or more third openings 663. The position of the third opening 663 can correspond to a specific area on the first electrode layer 661 to ensure that the conductive connection formed later can be precisely aligned.

[0122] After the third opening 663 is formed, as Figure 6G As shown, a second electrode layer 664 is deposited on the first dielectric layer 662 such that the second electrode layer 664 covers at least a portion of the surface of the first dielectric layer 662 and fills the third opening 663 to connect with the first electrode layer 661.

[0123] The second electrode layer 664 is another component of the backplane electrode layer or intermediate electrode in a MEMS device. Its material can be selected from polysilicon, metals (such as aluminum, titanium, tungsten, copper, etc.), or other conductive materials, and is formed using processes such as low-pressure chemical vapor deposition (LP-CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD). The second electrode layer 664 is deposited on the upper surface of the first dielectric layer 662, and its thickness can be selected according to the electrical performance requirements of the device, for example, between 0.2 μm and 1 μm. The preferred thickness of the second electrode layer 664 is the same as that of the first electrode layer 661.

[0124] During the deposition process, the second electrode layer 664 not only covers the flat upper surface of the first dielectric layer 662, but also enters and fills the interior of the third opening 663. Since the third opening 663 is an opening structure that penetrates the first dielectric layer 662, when the second electrode layer 664 is deposited to the bottom of the third opening 663, it will directly contact the exposed surface of the first electrode layer 661, so that the first electrode layer and the second electrode layer form an electrical connection through the third opening, thereby making the second electrode layer 664 and the first electrode layer 661 have the same potential.

[0125] This structure enables interconnection between the conductive layers on both sides of the backplane electrode layer, allowing electrical signals to be transmitted from one side to the other without additional wires or bonding steps, thus simplifying the electrical layout and packaging design of the device. Furthermore, the conductive material filling the third opening 663 forms a tight contact interface with the first dielectric layer 662, exhibiting good mechanical stability and electrical reliability, and is not easily broken due to thermal stress or mechanical vibration.

[0126] This completes the fabrication process of the first structural layer 210 (including the stacked first electrode layer 661, first dielectric layer 662, and second electrode layer 664). The MEMS structure of this embodiment will be further optimized based on the first structural layer 210 below.

[0127] like Figure 6H As shown, after the first structural layer 210 is formed, the first structural layer 210 can be etched until the third sacrificial layer 640 is exposed, forming multiple fourth openings 665.

[0128] The fourth opening 665 can be formed by patterned etching. The bottom of the fourth opening 665 exposes the third sacrificial layer 640. The position of at least part of the fourth opening 665 can correspond to the position of the second conductive post. The fourth opening 665 can be a circular hole, a square hole, or a groove-shaped structure, and its size can be determined according to the size of the second conductive post at the corresponding position, for example, the diameter or width is slightly larger than the outer contour size of the second conductive post at the corresponding position.

[0129] The number and layout of the fourth openings 665 can be designed according to the mechanical support and electrical connection requirements of the MEMS device. For example, in some embodiments, the position of some of the fourth openings 665 may not correspond to the second conductive post, but may be determined only according to the position of the connection posts to be set later. In other embodiments, some of the fourth openings 665 may not need to penetrate all the layers in the first structural layer 210 (such as the first electrode layer 661, the first dielectric layer 662 and the second electrode layer 664 in the figure), but may only penetrate a portion of the layers in the first structural layer 210. For example, in the peripheral area of ​​the first structural layer 210, only the first dielectric layer 662 may be etched through.

[0130] Then, as Figure 6I As shown, after the fourth opening 665 is formed, a first sacrificial layer 401 is deposited on the first structural layer 210. When the first sacrificial layer 401 is deposited on the first structural layer 210, the first sacrificial layer 401 fills the plurality of fourth openings 665.

[0131] The process of depositing the first sacrificial layer 401 on the first structural layer 210 is combined with the above text. Figure 4A Similar to the description, the difference is that in the deposition process of this embodiment, the first sacrificial layer 401 not only covers the upper surface of the first structural layer 210, but also enters and fills the interior of the fourth opening 665, thereby forming a sacrificial layer columnar structure that penetrates the first structural layer 210 in the fourth opening 665.

[0132] like Figure 6IAs further shown, at least a portion of the first sacrificial layer 401 and the third sacrificial layer 640 at the location corresponding to the fourth opening 665 can be etched to form a connecting hole 671 connecting the second structural layer and the third structural layer 630.

[0133] The via 671 can be obtained by patterning the first sacrificial layer 401 and the third sacrificial layer 640 at at least a portion of the locations corresponding to the fourth opening 665. The etching process can employ either dry or wet etching, depending on the characteristics of the sacrificial layer material. During etching, the etchant enters from the upper surface of the first structural layer 210, sequentially passing through the first sacrificial layer 401 and the third sacrificial layer 640 until the surface of the third structural layer 630 is exposed. The resulting via 671 is typically a vertical via. The position and number of vias 671 correspond to the position and number of the fourth openings 665; for example, one via 671 can be formed at each location corresponding to the fourth opening 665, or vias 671 can be formed only at a portion of the locations corresponding to the fourth openings 665. The diameter or width of the via 671 is typically smaller than the size of the fourth opening 665 to ensure that the subsequently deposited dielectric material can completely fill the via 671.

[0134] By forming the connecting hole 671, a vertical channel is provided for the subsequent deposition of the connecting pillar material, enabling the connecting pillar to extend downward from the second structural layer to the third structural layer 630, thereby achieving mechanical connection and electrical isolation between the two structural layers, and ensuring the structural stability and electrical performance of the dual-diaphragm MEMS device.

[0135] After forming the connecting hole 671, as Figure 6J As shown, a second dielectric layer 672 can be deposited on the first sacrificial layer 401 such that the second dielectric layer 672 covers the surface of the first sacrificial layer 401 and fills the via 671.

[0136] The second dielectric layer 672 is a material layer used to form the connecting pillar. The material can be selected from silicon nitride, silicon oxide, aluminum oxide, or polycrystalline silicon, or a combination of two or more of these materials, and is formed by chemical vapor deposition (CVD) processes, such as plasma-enhanced chemical vapor deposition (PE-CVD), low-pressure chemical vapor deposition (LP-CVD), or atomic layer deposition (ALD). The deposition thickness of the second dielectric layer 672 needs to be sufficient to completely fill the connecting hole 671; for example, the deposition thickness of the second dielectric layer 672 on the first sacrificial layer 401 can be 0.5 μm to 2 μm. During deposition, the second dielectric layer 672 covers the upper surface of the first sacrificial layer 401 and extends downward along the inner wall of the connecting hole 671 to the bottom of the connecting hole 671, thereby forming a solid dielectric pillar inside the connecting hole 671. This dielectric pillar extends from the upper surface of the first sacrificial layer 401 to the surface of the third structural layer 630.

[0137] Next, as Figure 6K As shown, the second dielectric layer 672 is etched to retain the second dielectric layer 672 in the connecting hole to form the connecting post 673.

[0138] Specifically, patterned etching can be used to process the second dielectric layer 672, removing at least a portion of the material of the second dielectric layer 672 on the surface of the first sacrificial layer 401, while retaining the second dielectric layer 672 filling the interior of the connecting hole 671, thus forming a connecting post 673. The connecting post 673 extends upward from the surface of the third structural layer 630 to be flush with the upper surface of the first sacrificial layer 401, and its shape is consistent with the shape of the connecting hole 671, such as a cylindrical, square, or annular columnar structure.

[0139] By depositing the second dielectric layer 672 and filling the via 671, a vertical mechanical support structure, namely the connecting post 673, can be formed in the thickness direction of the MEMS structure. This connecting post 673 connects the upper second structural layer to the lower third structural layer 630, providing structural stability and mechanical support for the dual-diaphragm MEMS device and preventing collapse or deformation of the layers during subsequent processing or use. Secondly, the connecting post 673, formed of a dielectric material, has excellent electrical insulation properties, preventing accidental short circuits between the upper and lower structures and ensuring that the signal detection of the capacitive MEMS device is not interfered with. Furthermore, the connecting post 673 is flush with the surface of the first sacrificial layer 401, providing a flat substrate for subsequent deposition of other thin film layers (such as auxiliary structural layers or main structural layers), which is beneficial for improving the uniformity and yield of subsequent processes.

[0140] Then, the above-described procedure can be performed on the first sacrificial layer 401. Figures 4A-4G The operating steps shown, or as follows Figures 5A-5C The operation steps shown are used to obtain the MEMS structure including a release channel and a sealing layer according to the embodiments of this application.

[0141] In other embodiments, such as Figure 6L As shown, after the auxiliary structural layer 222 and the second sacrificial layer 402 are formed on the first sacrificial layer 401 and before the main structural layer is deposited, the surface of the first sacrificial layer 401 facing the second structural layer is etched to form at least one first groove 681, the at least one first groove 681 including a first annular groove 682 surrounding the connecting post 673.

[0142] Specifically, the formation process of the first groove 681 includes: First, after forming the auxiliary structural layer 222 and the second sacrificial layer 402, the exposed surface of the first sacrificial layer 401 is patterned by etching. The position and shape of the first groove 681 are defined by photolithography. Then, anisotropic etching of the first sacrificial layer 401 is performed using a dry etching process (e.g., reactive ion etching) to remove the first sacrificial layer material in the corresponding area, forming the first groove 681 of a predetermined depth. The depth of the first groove 681 can be selected according to the height requirements of the subsequently formed first conductive pillar, for example, it can be between 1 μm and 2 μm. The shape of the first groove 681 can be circular, square, or annular.

[0143] In some embodiments, at least one first groove 681 may include a first annular groove 682, i.e., an annular groove structure, which surrounds the connecting post 673. Its annular path can be a circular ring, a square ring, or other closed annular geometry. The inner and outer diameters of the first annular groove 682 can be set according to the size requirements of the subsequently formed first conductive post. In other embodiments, the width (i.e., the ring width) of the first annular groove 682 is 0.3 μm to 1 μm. Exemplarily, the width of the first annular groove 682 can be 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, or other values ​​within the range of 0.3 μm to 1 μm. The formation of the first annular groove 682 requires a corresponding annular pattern on the photomask and is achieved through a precise etching process.

[0144] In other embodiments, when the surface of the first sacrificial layer 401 facing the second structural layer is etched, the first groove 681 and the second groove are symmetrically distributed. Here, symmetrical distribution means that in a plane perpendicular to the thickness direction of the second structural layer, the position and shape of the first groove 681 and the second groove 651 are mirror-symmetric or centrally symmetric with respect to the first structural layer 210. Specifically, the first groove 681 is formed on the upper surface of the first sacrificial layer 401, while the second groove is formed on the lower surface of the third sacrificial layer 640 (specifically, the first sacrificial sub-layer 641), with both located on the upper and lower sides of the first structural layer 210, respectively. When the first structural layer 210 is considered as the symmetry layer (or the center of symmetry layer), the projected contours of the first groove 681 and the second groove 651 on the first structural layer 210 coincide, aligning them in the vertical direction. For example, when the second groove includes a second annular groove, the first groove 681 includes a first annular groove 682, and the first annular groove 682 and the second annular groove have the same inner diameter, outer diameter, and ring width, and are aligned in the vertical direction, thereby forming a symmetrical annular structure. This symmetrical distribution can be achieved by precisely designing the pattern of the photomask: when fabricating the first groove 681 on the first sacrificial layer 401, the same or complementary photomask pattern as that used to form the second groove is used, and alignment accuracy is ensured.

[0145] After the first groove is formed, as Figure 6M As shown, a main structural layer can be deposited on the first sacrificial layer 401, the second sacrificial layer 402, and the auxiliary structural layer 222. During the deposition of the main structural layer 221, the main structural layer 221 fills the first groove to form at least one first conductive post 683 on the surface of the second structural layer facing the first structural layer 210. The at least one first conductive post 683 includes a first annular conductive post 684 surrounding the connecting post 673. The first annular conductive post 684 is arranged around the connecting post 673, and its annular path can be a circular ring, a square ring, or other closed annular geometry. The inner diameter, outer diameter, and annular width of the first annular conductive post 684 correspond to the dimensions of the first annular groove. In some embodiments, the width of the first annular conductive post is 0.3 μm to 1 μm.

[0146] By forming a first conductive pillar 683 in the main structural layer 221, and with the first structural layer 210 as the symmetrical layer, the second conductive pillar is symmetrically distributed with the first conductive pillar, together forming a symmetrical conductive pillar structure. Utilizing the edge electric field effect between the symmetrical conductive pillar structure and the fourth opening of the first structural layer, the MEMS structure can generate a more significant capacitance change under small deformations, which is beneficial for enhancing the capacitance detection sensitivity of the MEMS structure. For dual-diaphragm sensors, when the upper and lower diaphragms (i.e., the second and third structural layers) deform synchronously under the action of external signals, the bending degree and distribution of the electric field lines on both sides of the symmetrical conductive pillar structure remain consistent, thus doubling the utilization of the edge effect and achieving a superior improvement in sensitivity. For example, in dual-diaphragm microphone applications, this symmetrical structure can significantly improve acoustic sensitivity. Furthermore, using annular conductive pillars can fully utilize the annular space between the connecting pillar and the fourth opening, increasing the effective electrode area within a limited area, thereby further increasing the capacitance change and providing a structural basis for ultra-high precision detection of MEMS structures.

[0147] like Figure 6M As further shown, in addition to the first opening 2211, a fifth opening 2213 and / or a sixth opening 2214 can be provided on the main structure layer 221 as needed. The fifth opening 2213 can be symmetrical with the through hole 631 in the vertical direction to provide a ventilation path to balance the pressure between the environment and the back cavity. The sixth opening 2214 can be located on a portion of the second dielectric layer 672 retained on the surface of the first sacrificial layer (such as the peripheral area of ​​the MEMS structure) to separate multiple MEMS structures.

[0148] The function of the sixth opening 2214 is to separate multiple MEMS structures. For example, in the wafer-level packaging or device dicing process, the sixth opening 2214 can be used as an isolation groove to isolate adjacent MEMS devices and prevent crosstalk or short circuits in subsequent processes.

[0149] Furthermore, in Figure 6M Based on the structure shown, by etching the substrate 610, a structure like the one shown can be formed. Figure 6NThe back cavity 691 shown is an opening structure formed in the substrate 610 to expose the bottom region of the MEMS structure. The back cavity 691 is typically formed using a back-side deep silicon etching process (e.g., deep reactive ion etching, DRIE), where anisotropic etching is performed on the back side of the substrate 610 (i.e., the side facing away from the third dielectric layer 620) to remove the substrate material in the corresponding area until the surface of the third dielectric layer 620 is exposed. The size and shape of the back cavity 691 can be designed according to the application requirements of the MEMS device. For example, in microphone applications, the back cavity 691 is typically a circular or square opening with a diameter or width ranging from hundreds of micrometers to several millimeters to provide sufficient acoustic space.

[0150] In other embodiments, the second sacrificial layer 402, a portion of the first sacrificial layer 401, a portion of the third sacrificial layer 640, and a portion of the third dielectric layer 620 can be etched through the release channel, and the release channel is then sealed to obtain the desired result. Figure 6N The MEMS structure shown.

[0151] Specifically, the corrosive agent first enters through the first opening 2211, flows through the transverse gap 224, passes through the second opening 2221, and reaches the surfaces of the first sacrificial layer 401, the third sacrificial layer 640, and the third dielectric layer 620. It then reacts chemically with these sacrificial layer materials, converting them into soluble or volatile products before being discharged. During the corrosion process, the second sacrificial layer 402 is completely removed, forming the transverse gap; a portion of the first sacrificial layer is removed, forming the first cavity 240; a portion of the third sacrificial layer 640 is removed, forming the second cavity 692; and a portion of the third dielectric layer 620 is removed, allowing the back cavity 691 to communicate with the first cavity 240 and the second cavity 692. The uncorroded portion of the first sacrificial layer forms the spacer layer 230, and the uncorroded portion of the third sacrificial layer 640 forms the support structure between the third structural layer 630 and the first structural layer 210.

[0152] Understandably, removing multiple sacrificial layers at once via the release channel eliminates the need for designing separate release holes for each sacrificial layer, significantly simplifying the manufacturing process and reducing its complexity and cost. Secondly, because the release channel is a non-perpendicular, tortuous path, the sealing layer is not directly deposited onto the surface of the first structural layer 210 or the third structural layer 630 during deposition, preventing the sealing material from forming protrusions on these layer surfaces, thus ensuring the movement space and performance accuracy of the MEMS structure.

[0153] After the etching process is completed, the release channel is sealed, for example by depositing a sealing layer and then performing a maskless etching process to form a sealing layer 250, thus blocking the release channel and obtaining the desired result. Figure 6NThe MEMS structure shown includes a first structural layer 210, a second structural layer 220 (including a main structural layer 221 and an auxiliary structural layer 222), and a third structural layer 630. The third structural layer 630 is spaced apart from the first structural layer 210, and the first structural layer 210 is located between the second structural layer 220 and the third structural layer 630, forming a second cavity 692 between the third structural layer 630 and the first structural layer 210. The MEMS structure may also include a connecting post 673 connecting the second structural layer 220 and the third structural layer 630; and the first structural layer 210 has multiple fourth openings, at least some of which are for the connecting post 673 to pass through. At least one first conductive post 683 is provided on the surface of the main structural layer 221 facing the first structural layer 210, and the at least one first conductive post 683 includes a first annular conductive post 684 configured to surround the connecting post 673. At least one second conductive post is disposed on the surface of the third structural layer 630 facing the first structural layer 210, and the at least one second conductive post includes a second annular conductive post configured to surround the connecting post 673.

[0154] This application also provides a MEMS microphone, including the one described above according to this application. Figures 2A to 6N The MEMS structure described in any one of the above.

[0155] Specifically, this MEMS microphone integrates the release channel structure, sealing layer structure, and optional features such as dual diaphragms, connecting pillars, and conductive pillars described in the above embodiments. For example, in its second structural layer, the main structural layer and the auxiliary structural layer form a non-perpendicular release channel through staggered first and second openings and lateral gaps, effectively preventing the sealing layer from forming protrusions on the surface of the bottom structural layer, thus providing ample space for diaphragm movement. In other embodiments, symmetrically distributed conductive pillars (such as the first and second conductive pillars) utilize the edge electric field effect to generate more significant capacitance changes under small deformations. When the upper and lower diaphragm layers deform synchronously, the bending degree and distribution of the electric field lines on both sides are consistent, doubling the utilization of the edge effect and significantly improving the microphone's sensitivity. Furthermore, the annular conductive pillar fully utilizes the space between the connecting pillar and the fourth opening, further increasing the effective capacitance area. With the above structure, this MEMS microphone not only simplifies the manufacturing process and achieves high yield, but also possesses excellent acoustic performance and reliability, making it suitable for high-precision sound detection scenarios.

[0156] While numerous embodiments of this application have been shown and described herein, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Many modifications, alterations, and alternatives will arise for those skilled in the art without departing from the spirit and intent of this application. It should be understood that various alternatives to the embodiments of this application described herein may be employed in the practice of this application. The appended claims are intended to define the scope of protection of this application and therefore cover equivalents or alternatives within the scope of these claims.

Claims

1. A MEMS structure, characterized by, include: First structural layer; A second structural layer is provided with a spacer layer between it and the first structural layer to form a first cavity between the second structural layer and the first structural layer. The second structural layer includes a main structural layer and an auxiliary structural layer. The main structural layer and the auxiliary structural layer are in contact and connected at at least one first region and separated from each other at at least one second region to form a lateral gap. The main structural layer is provided with a first opening. The auxiliary structural layer is provided on the side of the first opening facing the first cavity. The auxiliary structural layer is provided with a second opening. The first opening and the second opening are offset in the thickness direction of the second structural layer, and a release channel is formed when the first opening and the second opening are connected through the lateral gap. A sealing layer is located at the release channel to seal the release channel.

2. The MEMS structure according to claim 1, characterized in that, The sealing layer covers the inner wall of the first opening and extends along the thickness direction of the second structural layer to the auxiliary structural layer corresponding to the first opening, so as to seal the transverse gap.

3. The MEMS structure according to claim 1 or 2, characterized in that, The surface of the main structural layer facing the first cavity has a protrusion structure facing the second opening at a position corresponding to the second opening.

4. The MEMS structure according to claim 1 or 2, characterized in that, The main structural layer is disposed on the spacer layer, and in a plane perpendicular to the thickness direction of the second structural layer, the projection of the main structural layer and the spacer layer overlaps, while the projection of the auxiliary structural layer and the spacer layer do not overlap.

5. The MEMS structure according to claim 1, characterized in that, The first opening is a groove-shaped structure or a hole-shaped structure; The second opening is a hole-shaped structure.

6. The MEMS structure according to claim 1 or 2, characterized in that, The thickness of the transverse gap is 0.02 μm to 0.5 μm; and / or The thickness of the auxiliary structural layer is 0.1μm to 0.5μm.

7. The MEMS structure according to claim 1, characterized in that, The width of the first opening is 1μm to 5μm; The width of the first opening is smaller than the width of the second opening.

8. The MEMS structure according to claim 1, characterized in that, The first structural layer includes a first electrode layer, a first dielectric layer, and a second electrode layer stacked together; wherein A third opening is provided on the first dielectric layer, and the first electrode layer and the second electrode layer are electrically connected through the third opening.

9. The MEMS structure of claim 1 or 8, wherein, Also includes: A third structural layer is arranged at a distance from the first structural layer, and the first structural layer is located between the second structural layer and the third structural layer, with a second cavity formed between the third structural layer and the first structural layer.

10. The MEMS structure of claim 9, wherein, Also includes: A connecting column, which connects the second structural layer and the third structural layer; and The first structural layer is provided with a plurality of fourth openings, at least some of which are used for the connecting post to pass through.

11. The MEMS structure according to claim 10, characterized in that, At least one first conductive post is provided on the surface of the main structural layer facing the first structural layer, and the at least one first conductive post includes a first annular conductive post configured to surround the connecting post.

12. The MEMS structure according to claim 11, characterized in that, At least one second conductive post is disposed on the surface of the third structural layer facing the first structural layer, and the at least one second conductive post includes a second annular conductive post configured to surround the connecting post; and With the first structural layer as the symmetrical layer, the second conductive pillars are symmetrically distributed with respect to the first conductive pillars.

13. The MEMS structure according to claim 11, characterized in that, The width of the first annular conductive post is 0.3μm~1μm.

14. A MEMS microphone, characterized by Includes the MEMS structure according to any one of claims 1-13.

15. A method of fabricating a MEMS structure, characterized by, include: A first sacrificial layer is deposited on the first structural layer; An auxiliary structural layer with a second opening is formed on the first sacrificial layer; A main structure layer with a first opening is formed on the auxiliary structure layer, and the main structure layer and the auxiliary structure layer are contacted and connected at at least one first region and separated from each other at at least one second region to form a lateral gap. The first opening and the second opening are offset in their thickness direction so as to form a release channel through the first opening, the lateral gap and the second opening. Using the release channel, a portion of the first sacrificial layer is etched to form a first cavity between the second structural layer, which is composed of the auxiliary structural layer and the main structural layer, and the first structural layer. The portion of the first sacrificial layer that is not etched constitutes a spacer layer between the first structural layer and the second structural layer. The release channel is sealed.

16. The method of claim 15, wherein, The sealing process for the release channel includes: A sealing layer is deposited on the main structural layer; The sealing layer is etched using a photomask-free etching process to retain the sealing layer covering the inner wall of the first opening and extending to the auxiliary structural layer based on the sidewall effect, so as to seal the lateral gap.

17. The method of manufacturing according to claim 15 or 16, wherein, Further includes: An auxiliary structural layer with a second opening is formed on the surface of the middle region of the first sacrificial layer; When etching a portion of the first sacrificial layer, the middle region of the first sacrificial layer is etched.

18. The preparation method according to claim 15, characterized in that, The first opening is a groove-shaped structure or a hole-shaped structure; The second opening is a hole-shaped structure.

19. The production method according to claim 15 or 16, characterized by, The formation of the release channel includes: A second sacrificial layer is deposited on the auxiliary structural layer; The second sacrificial layer is etched to retain the first sacrificial portion covering the second opening and the second sacrificial portion covering at least a portion of the surface of the auxiliary structure layer; A main structure layer is deposited on the auxiliary structure layer, the second sacrificial layer, and the first sacrificial layer; The main structural layer above the second sacrificial part is etched to form the first opening; The first sacrificial portion and the second sacrificial portion are corroded through the first opening to form the release channel.

20. The method of claim 19, wherein, Further includes: A conformal deposition process is used to deposit the second sacrificial layer on the auxiliary structural layer, so that the second sacrificial layer forms a recessed structure at the second opening; When the main structure layer is deposited on the auxiliary structure layer, the second sacrificial layer and the first sacrificial layer, the main structure layer covers the recessed structure such that the main structure layer faces the surface of the first cavity and forms a protrusion facing the second opening at the recessed structure.

21. The preparation method according to claim 19, characterized in that, The thickness of the second sacrificial portion is 0.02 μm to 0.5 μm; and / or The thickness of the auxiliary structural layer is 0.1μm to 0.5μm.

22. The preparation method according to claim 19, characterized in that, The width of the first opening is 1μm to 5μm; The width of the first opening is smaller than the width of the second opening.

23. The method of claim 15, wherein, The first structural layer includes a first electrode layer, a first dielectric layer, and a second electrode layer stacked together. Before depositing the first sacrificial layer on the first structural layer, the preparation method further includes: A first dielectric layer is deposited on the first electrode layer; The first dielectric layer is etched until the first electrode layer is exposed to form a third opening in the first dielectric layer; A second electrode layer is deposited on the first dielectric layer such that the second electrode layer covers at least a portion of the surface of the first dielectric layer and fills the third opening to connect with the first electrode layer.

24. The preparation method according to claim 19, characterized in that, Before depositing the first sacrificial layer on the first structural layer, the preparation method further includes: Provide a third structural layer; A third sacrificial layer is deposited on the third structural layer; The first structural layer is formed on the third sacrificial layer; The first structural layer is etched until the third sacrificial layer is exposed, forming a plurality of fourth openings, so that when the first sacrificial layer is deposited on the first structural layer, the first sacrificial layer fills the plurality of fourth openings.

25. The preparation method according to claim 24, characterized in that, Further includes: The first sacrificial layer and the third sacrificial layer at least part of the location corresponding to the fourth opening are etched to form a connecting hole between the second structural layer and the third structural layer; A second dielectric layer is deposited on the first sacrificial layer such that the second dielectric layer covers the surface of the first sacrificial layer and fills the via; The second dielectric layer is etched to retain the second dielectric layer in the connecting hole, thereby forming a connecting post.

26. The preparation method according to claim 25, characterized in that, Further includes: Before depositing the main structural layer, the surface of the first sacrificial layer facing the second structural layer is etched to form at least one first groove, the at least one first groove including a first annular groove surrounding the connecting post; During the deposition of the main structural layer, the main structural layer fills the at least one first groove to form at least one first conductive post on the surface of the second structural layer facing the first structural layer, the at least one first conductive post including a first annular conductive post surrounding the connecting post.

27. The preparation method according to claim 26, characterized in that, The third sacrificial layer includes a first sacrificial sublayer and a second sacrificial sublayer, and depositing the third sacrificial layer on the third structural layer includes: A first sacrificial sublayer is deposited on the third structural layer; The first sacrificial sublayer is etched until the third structural layer is exposed, forming at least one second groove, wherein the at least one second groove includes a second annular groove; A conductive layer is deposited on the first sacrificial sublayer, such that the conductive layer covers the surface of the first sacrificial sublayer and fills the at least one second groove up to the surface of the third structural layer; The conductive layer on the surface of the first sacrificial sublayer is removed, while the conductive layer deposited in the at least one second groove is retained to form at least one second conductive pillar on the third structural layer, the at least one second conductive pillar including a second annular conductive pillar; A second sacrificial sublayer is deposited on the surface of the first sacrificial sublayer and on the surface of the second conductive pillar facing the first structural layer.

28. The preparation method according to claim 27, characterized in that, Further includes: When etching the surface of the first sacrificial layer facing the second structural layer, the first groove and the second groove are symmetrically distributed.

29. The preparation method according to claim 26, characterized in that, The width of the first annular groove is 0.3μm~1μm.

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