CN117835133A

CN117835133A - MEMS microphone and preparation method thereof

Info

Publication number: CN117835133A
Application number: CN202311864137.7A
Authority: CN
Inventors: 傅思宇
Original assignee: Xinlian Integrated Circuit Manufacturing Co ltd
Current assignee: Xinlian Integrated Circuit Manufacturing Co ltd
Priority date: 2023-12-29
Filing date: 2023-12-29
Publication date: 2024-04-05

Abstract

The embodiment of the application relates to a MEMS microphone and a preparation method thereof, comprising the following steps: providing a substrate; forming a first sacrificial layer; forming a vibrating diaphragm; forming a second sacrificial layer; forming a back plate; forming a back cavity in a substrate; forming a first cavity, a slit and a second cavity; the forming of the second sacrificial layer includes: injecting charges into a part of the diaphragm corresponding to the slit preset formation region; after forming the back plate, the method comprises the following steps: forming a first release hole penetrating through the back plate in the thickness direction of the substrate; and/or, before forming the second sacrificial layer, comprising: injecting charges into a portion of the diaphragm corresponding to the slit preset formation region; forming the back plate includes: forming a second support structure and a back plate; after forming the second support structure, comprising: injecting charge in the second support structure; and/or, forming the diaphragm comprises: forming a first support structure and a vibrating diaphragm; after forming the first support structure, comprising: injecting charge in the first support structure; the etching liquid and the electric charge are utilized to carry out electrochemical reaction. Thereby, etching efficiency is accelerated.

Description

MEMS microphone and preparation method thereof

Technical Field

The application relates to the technical field of semiconductors, in particular to an MEMS microphone and a preparation method thereof.

Background

MEMS microphone devices fabricated using microelectromechanical systems processes (Micro Electro Mechanical System, MEMS) are widely used due to their small and lightweight features.

The MEMS microphone forms a variable capacitor by using the vibrating diaphragm and the backboard, and the change of the capacitor is realized by the vibration of the vibrating diaphragm, so that the sound signal is converted into an electric signal. In actual production, a downward vibration space of the diaphragm is generally formed by etching a sacrificial layer below the diaphragm, and the sacrificial layer above the etched diaphragm is used for forming a cavity between the diaphragm and the back plate as an upward vibration space of the diaphragm. Thus, after sound enters from the acoustic holes on the back plate, the diaphragm can vibrate up and down in the vibration space.

However, in the current process of etching the sacrificial layer, in order to prevent the sacrificial layer from remaining, especially, the sacrificial layer below the diaphragm, there is a certain side-picking requirement, and the process is generally long, which easily causes excessive loss of the diaphragm, the back plate, and the like, and finally affects the mechanical reliability of the device. Specifically, in the process, a slit is formed between the vibrating diaphragm and the substrate by side etching, and etching liquid for etching the sacrificial layer is easily concentrated in the deep part of the slit and continuously erodes the vibrating diaphragm, so that the strength of the vibrating diaphragm is influenced, and the mechanical reliability is greatly influenced.

Disclosure of Invention

In view of the foregoing, embodiments of the present application provide a MEMS microphone and a method for manufacturing the same to solve at least one of the problems in the background art.

In one aspect, an embodiment of the present application provides a method for preparing a MEMS microphone, where the method includes:

providing a substrate, wherein the substrate comprises a back cavity preset forming area;

forming a first sacrificial layer on the substrate, wherein the first sacrificial layer comprises a first cavity preset forming area overlapped with the back cavity preset forming area along the thickness direction of the substrate and a slit preset forming area positioned at the periphery of the first cavity preset forming area;

forming a diaphragm on the first sacrificial layer;

forming a second sacrificial layer on the diaphragm;

forming a back plate on the second sacrificial layer;

forming a back cavity in the substrate; and removing at least part of the first sacrificial layer to form a first cavity and a slit, and removing at least part of the second sacrificial layer to form a second cavity;

wherein,

before forming the second sacrificial layer, the method further comprises: injecting charges into a portion of the diaphragm corresponding to the slit preset formation region; after forming the back plate, the method further comprises: forming a first release hole penetrating the back plate in a thickness direction of the substrate in a portion of the back plate corresponding to the slit preset formation region;

And/or, before forming the second sacrificial layer, the method further comprises: injecting charges into a portion of the diaphragm corresponding to the slit preset formation region; forming a back plate on the second sacrificial layer, comprising: forming a second support structure covering the side wall of the second sacrificial layer, and a backboard connected with the second support structure and positioned on the second sacrificial layer; after forming the second support structure, the method further comprises: injecting charge in the second support structure;

and/or forming a diaphragm on the first sacrificial layer, including: forming a first support structure covering the side wall of the first sacrificial layer, and a vibrating diaphragm connected with the first support structure and positioned on the first sacrificial layer; after forming the first support structure, the method further comprises: injecting charge in the first support structure;

the first cavity, the slit and the second cavity are formed by a wet etching process, and part of etching liquid interacts with injected charges to perform electrochemical reaction, so that a part of the diaphragm corresponding to the slit is etched to form a plurality of second release holes penetrating the diaphragm along the thickness direction of the substrate, and/or the second support structure is etched to form a plurality of third release holes penetrating the second support structure along the plane direction of the substrate, and/or the first support structure is etched to form a plurality of fourth release holes penetrating the first support structure along the plane direction of the substrate; etching the first sacrificial layer by partial etching liquid through the back cavity to form an opening exposing a part of the first sacrificial layer in the slit preset forming area from one side of the first cavity; and part of etching liquid passes through the second release hole and/or the fourth release hole, and part of etching liquid passes through the opening to jointly etch the part of the first sacrificial layer positioned in the slit preset forming area so as to form a slit.

Optionally, the forming a first release hole in a portion of the back plate corresponding to the slit preset formation region includes: injecting charges in a portion of the back plate corresponding to the slit preset formation region; and performing a wet etching process, wherein part of etching liquid interacts with charges injected into the backboard to perform electrochemical reaction, so that a plurality of first release holes are etched at corresponding positions of the backboard.

Optionally, the slit pre-formed region includes a first side facing the opening and a second side facing away from the opening, the first side and the second side being opposite each other in a direction parallel to a substrate plane;

the projection of the part of the vibrating diaphragm, into which the electric charges are injected, is positioned in the projection range of the slit preset forming area along the thickness direction of the substrate; the portion is closer to the second side than the first side.

Optionally, the projection of the portion of the diaphragm into which the electric charges are injected is annular in the thickness direction of the substrate, and surrounds the projection of the first cavity preset formation region.

Optionally, the projection of the first release hole and the projection of the second release hole at least partially coincide in the thickness direction of the substrate.

Optionally, the charge is injected by an oxygen plasma.

Optionally, the first support structure and the diaphragm are of the same material; and/or the second support structure and the back plate are the same material.

In a second aspect, embodiments of the present application further provide a MEMS microphone, including:

a substrate in which a back cavity is formed;

the first support structure is positioned between the substrate and the vibrating diaphragm, so that the vibrating diaphragm is arranged above the substrate at intervals;

the first cavity and the slit are positioned in the area between the vibrating diaphragm and the substrate, the first cavity coincides with the back cavity along the thickness direction of the substrate, and the slit is positioned at the periphery of the first cavity and is communicated with the first cavity;

the second support structure is positioned between the vibrating diaphragm and the back plate, so that the back plate is arranged above the vibrating diaphragm at intervals;

wherein,

a first release hole penetrating the back plate in the thickness direction of the substrate is formed in a part of the back plate corresponding to the slit, and a plurality of second release holes penetrating the diaphragm in the thickness direction of the substrate are formed in a part of the diaphragm corresponding to the slit; the second release holes are etched and formed by utilizing the interaction of etching liquid and charges injected into the vibrating diaphragm in a wet etching process to generate electrochemical reaction;

And/or a plurality of third release holes penetrating the second support structure along the substrate plane direction are formed in the second support structure, and a plurality of second release holes penetrating the diaphragm along the substrate thickness direction are formed in the part of the diaphragm corresponding to the slit; the second release holes are etched and formed by utilizing the interaction of etching liquid and charges injected into the vibrating diaphragm in a wet etching process to generate electrochemical reaction; the third release holes are etched and formed by utilizing the interaction of etching liquid and charges injected into the second support structure in a wet etching process to generate electrochemical reaction;

and/or, a plurality of fourth release holes penetrating the first support structure along the substrate plane direction are formed in the first support structure; the fourth release holes are etched by an electrochemical reaction of an etching solution interacting with charges injected in the first support structure in a wet etching process.

Optionally, the number of the first release holes is a plurality, and the plurality of the first release holes are etched and formed by interaction of etching liquid and charges injected in the backboard in a wet etching process to generate electrochemical reaction.

Optionally, the slit comprises a first side towards the first cavity and a second side away from the first cavity, the first side and the second side being opposite each other in a direction parallel to the substrate plane;

a second release hole of the plurality of second release holes closest to the second side is less than a second release hole closest to the first side.

Optionally, the projections of the plurality of second release holes are distributed over an annular region surrounding the projections of the first cavity in the thickness direction of the substrate.

The MEMS microphone and the preparation method thereof provided by the embodiment of the application have the following beneficial effects:

etching liquid can flow into the slit preset forming area through the opening, and can flow into the slit preset forming area through the second release hole and/or the fourth release hole, so that the part of the first sacrificial layer positioned in the slit preset forming area is etched together to form the slit, the channel of the etching liquid flowing into the slit preset forming area is increased, the etching efficiency is improved, the etching liquid is prevented from accumulating in the deep part of the slit, the diaphragm and the backboard are prevented from being damaged due to overlong etching time, and the etching liquid is prevented from being damaged due to overlong etching time; and each release hole is etched by utilizing the interaction of etching liquid and injected charges in a wet etching process to generate electrochemical reaction, so that the release holes do not need to be pre-buried, and the problem that the pre-buried release holes are blocked by impurities released by a sacrificial layer in high-temperature treatment of a production process, so that the release holes cannot be opened to influence the etching rate is avoided; the number of the formed release holes is multiple, so that the contact path between etching liquid and the sacrificial layer is increased, and the etching efficiency is improved; moreover, the etching solution and injected charges interact to generate electrochemical reaction to etch the material to form the release holes in the wet etching process, so that the difficulty that the side wall through holes cannot be realized by the traditional photoetching and etching process is solved, and the process implementation reliability of the release holes formed at the proper positions of the device structure is ensured; finally, the mechanical reliability of the device is ensured.

Additional aspects and advantages of the application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the application.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the application and do not constitute an undue limitation to the application. In the drawings:

fig. 1 to 2 are schematic cross-sectional structures of MEMS microphones in the related art during the manufacturing process;

fig. 3 is a flow chart of a method for manufacturing a MEMS microphone according to an embodiment of the present application;

fig. 4 to 12 are schematic cross-sectional structures of MEMS microphones according to another alternative embodiment of the present application during the manufacturing process;

fig. 13 to 16 are schematic cross-sectional structures of MEMS microphones according to an alternative embodiment of the present application during the manufacturing process;

fig. 17 to 19 are schematic cross-sectional structures of MEMS microphones according to still another alternative embodiment of the present application during the manufacturing process;

fig. 20 to 21 are schematic cross-sectional structures of MEMS microphones according to still another alternative embodiment of the present application during the manufacturing process;

Fig. 22 to 23 are schematic cross-sectional views of MEMS microphones according to other alternative embodiments of the present application during the manufacturing process;

FIGS. 24-25 are top views of MEMS microphones provided in some alternative embodiments of the present application during fabrication;

fig. 26 is a top view of a MEMS microphone provided in some alternative embodiments of the present application.

Detailed Description

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present application are shown in the drawings, it should be understood that the present application may be embodied in various forms and should not be limited to the specific embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present application. However, it will be apparent to one skilled in the art that the present application may be practiced without one or more of these details. In other instances, well-known features have not been described in detail so as not to obscure the application; that is, not all features of an actual implementation are described in detail herein, and well-known functions and constructions are not described in detail.

In the drawings, the size of layers, regions, elements and their relative sizes may be exaggerated for clarity. Like numbers refer to like elements throughout.

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

Spatially relative terms, such as "under … …," "under … …," "below," "under … …," "above … …," "above," and the like, may be used herein for ease of description to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use and operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements or features described as "under" or "beneath" other elements would then be oriented "on" the other elements or features. Thus, the exemplary terms "under … …" and "under … …" may include both an upper and a lower orientation. The device may be otherwise oriented (rotated 90 degrees or other orientations) and the spatially relative descriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term "and/or" includes any and all combinations of the associated listed items.

For a thorough understanding of the present application, detailed steps and detailed structures will be presented in the following description in order to explain the technical aspects of the present application. Preferred embodiments of the present application are described in detail below, however, the present application may have other implementations in addition to these detailed descriptions.

Fig. 1 and 2 are schematic cross-sectional structures of a related art MEMS microphone during a manufacturing process. In the related art, when a wet etching process is performed, an etching solution etches the first sacrificial layer 200 through the back cavity 101, forming a first cavity 210; and the first sacrificial layer 200 in the slit preset formation region 220a is laterally etched through the opening 211 exposed by the first cavity 210, thereby forming the slit 220 as shown in fig. 2. The lateral etching process is generally long, so that excessive losses of the diaphragm 300, the back plate 500 and the like are easily caused, and the mechanical reliability of the device is affected; in addition, the etching solution is easily concentrated in the deep part of the slit 220, and continuously erodes the diaphragm 300, affecting the strength of the diaphragm 300.

Based on this, the embodiment of the application provides a method for preparing a MEMS microphone, please refer to fig. 3, which includes:

S301: providing a substrate, wherein the substrate comprises a back cavity preset forming area;

s302: forming a first sacrificial layer on a substrate, wherein the first sacrificial layer comprises a first cavity preset forming area overlapped with a back cavity preset forming area along the thickness direction of the substrate and a slit preset forming area positioned at the periphery of the first cavity preset forming area;

s303: forming a diaphragm on the first sacrificial layer;

s304: forming a second sacrificial layer on the diaphragm;

s305: forming a back plate on the second sacrificial layer;

s306: forming a back cavity in a substrate; and removing at least part of the first sacrificial layer to form a first cavity and a slit, and removing at least part of the second sacrificial layer to form a second cavity;

wherein,

the method further comprises, prior to forming the second sacrificial layer: s3101: injecting charges into a portion of the diaphragm corresponding to the slit preset formation region; after forming the back plate, the method further comprises: s3102: forming a first release hole penetrating the back plate in the thickness direction of the substrate in a portion of the back plate corresponding to the slit preset formation region;

and/or, before forming the second sacrificial layer, the method further comprises: s3101: injecting charges into a portion of the diaphragm corresponding to the slit preset formation region; s306a: forming a back plate on the second sacrificial layer, comprising: forming a second support structure covering the side wall of the second sacrificial layer, and a backboard connected with the second support structure and positioned on the second sacrificial layer; after forming the second support structure, the method further comprises: s3201: injecting charge in the second support structure;

And/or, S303a: forming a diaphragm on the first sacrificial layer, comprising: forming a first supporting structure covering the side wall of the first sacrificial layer, and a vibrating diaphragm connected with the first supporting structure and positioned on the first sacrificial layer; after forming the first support structure, the method further comprises: s3301: injecting charge in the first support structure;

the first cavity, the slit and the second cavity are formed by a wet etching process, part of etching liquid interacts with injected charges to generate electrochemical reaction, so that a part of the diaphragm corresponding to the slit is etched to form a plurality of second release holes penetrating the diaphragm along the thickness direction of the substrate, and/or a plurality of third release holes penetrating the second support structure along the plane direction of the substrate are etched in the second support structure, and/or a plurality of fourth release holes penetrating the first support structure along the plane direction of the substrate are etched in the first support structure; etching the first sacrificial layer by a part of etching liquid through the back cavity to form an opening exposing a part of the first sacrificial layer in the slit preset forming area from one side of the first cavity; and part of the etching liquid passes through the second release hole and/or the fourth release hole, and part of the etching liquid passes through the opening to jointly etch the part of the first sacrificial layer positioned in the slit preset forming area so as to form the slit.

As can be appreciated, in the method for manufacturing the MEMS microphone provided by the embodiment of the present application, the etching solution may not only flow into the slit preset formation area through the opening, but also flow into the slit preset formation area through the second release hole and/or the fourth release hole, so as to etch the portion of the first sacrificial layer located in the slit preset formation area together to form the slit, so that the channel of the etching solution flowing into the slit preset formation area is increased, the etching efficiency is improved, the etching solution is prevented from accumulating in the deep part of the slit, and damage to the diaphragm and the back plate caused by excessively long etching time is avoided; and each release hole is etched by utilizing the interaction of etching liquid and injected charges in a wet etching process to generate electrochemical reaction, so that the release holes do not need to be pre-buried, and the problem that the pre-buried release holes are blocked by impurities released by a sacrificial layer in high-temperature treatment of a production process, so that the release holes cannot be opened to influence the etching rate is avoided; the number of the formed release holes is multiple, so that the contact path between etching liquid and the sacrificial layer is increased, and the etching efficiency is improved; moreover, the etching solution and injected charges interact to generate electrochemical reaction to etch the material to form the release holes in the wet etching process, so that the difficulty that the side wall through holes cannot be realized by the traditional photoetching and etching process is solved, and the process implementation reliability of the release holes formed at the proper positions of the device structure is ensured; finally, the mechanical reliability of the device is ensured.

It will be appreciated that the steps indicated by the dashed arrows in fig. 3 represent steps performed in some alternative parallel solutions, and that in the following of this document the steps indicated by the dashed arrows will be described in alternative embodiments.

In step S301, referring to fig. 4, a substrate 100 is provided, and the substrate 100 includes a back cavity preset formation region 110a.

In this embodiment, the material of the substrate 100 may be any suitable substrate material known to those skilled in the art, for example, at least one of the following materials: silicon, silicon-on-insulator (SOI), silicon-on-insulator (SSOI), silicon-on-insulator (S-SiGeOI), silicon-on-insulator (SiGeOI), germanium-on-insulator (GeOI), and the like. The material of the substrate 100 is not limited in this application.

The substrate 100 may include an upper surface and a lower surface opposite to each other, and a direction perpendicular to the upper surface and the lower surface of the substrate is defined as a substrate thickness direction, neglecting flatness of the upper surface and the lower surface. The substrate thickness direction is also the stacking direction in which the material layers are subsequently deposited on the substrate 100. While the upper and lower surfaces of the substrate 100 are located on or, strictly speaking, the center plane in the thickness direction of the substrate, i.e., defined as the substrate plane; the direction parallel to the substrate plane may also be referred to as the direction along the substrate plane.

In step S302, please continue to refer to fig. 4, a first sacrificial layer 200 is formed on the substrate 100, and the first sacrificial layer 200 includes a first cavity pre-forming region 210a overlapping with the back cavity pre-forming region 101a along the thickness direction of the substrate, and a slit pre-forming region 220a located at the periphery of the first cavity pre-forming region 210 a.

Optionally, the material of the first sacrificial layer 200 includes silicon oxide.

Alternatively, the process of forming the first sacrificial layer 200 includes a thermal oxidation process, a low pressure chemical vapor deposition process, a plasma enhanced chemical vapor deposition process, or the like. The fabrication process of the first sacrificial layer 200 is not limited in this application.

As an alternative embodiment, referring to fig. 13, after forming the first sacrificial layer 200, the preparation method may further include: the first sacrificial layer 200 is patterned to form a plurality of first openings 230 penetrating the first sacrificial layer 200. Thus, referring to fig. 14, the diaphragm 300 formed later is filled in the first openings 230 to form the first bump structures 301 and the first supporting structures 340a. In the process of vibrating the diaphragm 300 up and down, the first protrusion structure 301 located in the first cavity preset forming area 210a may play a role in avoiding adhesion between the diaphragm 300 and the substrate 100.

In step S303, referring to fig. 5, a diaphragm 300 is formed on the first sacrificial layer 200.

Alternatively, the process of forming the diaphragm 300 includes a chemical vapor deposition method, a physical vapor deposition method, an atomic layer deposition method, a coating method, or the like. The process for preparing the diaphragm 300 is not particularly limited in this application.

Alternatively, the diaphragm 300 includes a multi-layer composite film composed of polysilicon and silicon nitride, and may further include a single polysilicon layer.

As an alternative embodiment, referring to fig. 14, a diaphragm 300 is formed on a first sacrificial layer 200, including: a first support structure 340a covering the sidewall of the first sacrificial layer 200 is formed, and the diaphragm 300 is connected to the first support structure 340a and located on the first sacrificial layer 200. Thus, the first support structure 340a may function to support the diaphragm 300 such that the diaphragm 300 may be spaced apart from the substrate 100; in addition, during the process of etching the first sacrificial layer 200 to form the slit, the first support structure 340a located at the edge of the slit pre-formed region 220a may serve as a lateral etching stop structure.

Optionally, the first support structure 340a and the diaphragm 300 are of the same material.

In this alternative specific example, forming the diaphragm 300 on the first sacrificial layer 200 may include: a diaphragm material is deposited, at least a portion of the diaphragm material is formed on the first sacrificial layer 200 to form the diaphragm 300, and at least a portion of the diaphragm material covers a sidewall of the first sacrificial layer 200 to form the first support structure 340a. Thus, the diaphragm 300 and the first support structure 340a are simultaneously formed by the diaphragm material, saving process steps.

As an alternative embodiment, after forming the first support structure 340a, the method further includes: charge is injected in the first support structure 340 a. Thus, referring to fig. 15, the fourth release hole 340 is formed on the first support structure 340a in the subsequent step, so that the etching solution can synchronously etch the first sacrificial layer 200 of the slit preset formation region 220a from two positions of the fourth release hole 340 and the opening 211 of the first cavity side, thereby accelerating the etching rate; on this basis, since the fourth release hole 340 is located at one side of the sidewall of the first sacrificial layer 200 and is a horizontal release hole along the substrate plane direction, the fourth release hole is formed through electrochemical reaction, and thus the difficulty that the sidewall through hole cannot be realized by the conventional photolithography and etching process is solved.

As another alternative embodiment, in step S3101, referring to fig. 5 and 24, electric charges are injected into the portion 310a of the diaphragm corresponding to the slit preset formation region. Therefore, in the subsequent step, the release holes are formed by utilizing the electrochemical reaction generated by the interaction of the etching liquid and the charges in the wet etching process, so that the etching liquid can conveniently etch the first sacrificial layer 200 positioned in the slit preset forming region 220a through the release holes, the etching rate is improved, and the damage to the device caused by overlong etching time is avoided.

In this embodiment, the portion 310a of the diaphragm 300 corresponding to the predetermined slit forming region refers to a portion where the predetermined slit forming region 220a projects onto the diaphragm 300 in the thickness direction of the substrate. Further, it should be understood that the electric charges may be injected in the portion 310a of the diaphragm 300 corresponding to the slit preset formation region, the electric charges may be injected to the whole of the diaphragm 310a, or the electric charges may be injected to the portion of the diaphragm 310 a; for example, referring to fig. 17, the portion into which the charge is injected is shown at 311 a.

It will be appreciated that during actual manufacturing, the MEMS microphone may be subjected to a number of high temperature processes, and specifically, for example, after the backplate 500 is formed, a high temperature annealing process is typically performed to activate the backplate 500 so that it may be electrically conductive. During this process, the sacrificial layer in the device is not removed, and under high temperature conditions, the sacrificial layer may generate impurities, specifically, for example, silicon-based impurities. If a release hole is formed in the diaphragm 300 in advance, impurities generated by the sacrificial layer may accumulate in the release hole, causing a blockage, which is not beneficial to the release of the subsequent sacrificial layer. And, silicon-based impurity is difficult to be removed by etching liquid, and after the sacrificial layer is removed, silicon-based impurity may remain on the inner wall of the device, resulting in problems such as leakage and sensitivity failure. In this embodiment, the second release hole is not pre-buried, but the position where the second release hole is to be formed (the position corresponding to the slit preset formation region 220 a) is first subjected to charge injection, so as to prepare for the second release hole to be opened in the subsequent wet etching process for removing the sacrificial layer. The risk that the pre-buried release hole is blocked by impurities is avoided, and the problem that the release hole cannot be opened to influence the etching rate is solved.

Alternatively, the process of injecting charge includes a plasma process.

Further, the charges are injected by oxygen plasma.

In this embodiment, a patterned mask layer (not shown) may be formed on the diaphragm 300 through a photolithography process, where a portion of the diaphragm 300 to be injected with electric charges is exposed, and a certain electric charge is applied to the portion by oxygen plasma, so that the electric charges are uniformly distributed in the portion of the diaphragm 300 to be injected with electric charges. It will be appreciated that the dot-like structure in the charge-injected portion 311a of the diaphragm in fig. 24 represents the charge and only schematically shows that the charge is uniformly distributed in this region, and that the degree of charge density, and thus the size and density of the second relief holes formed, can be controlled by controlling the power, gas flow and pressure adjustment of the oxygen plasma process during actual fabrication.

Alternatively, referring to fig. 25, in the thickness direction of the substrate, a projection 311s of the portion of the diaphragm into which the electric charges are injected is annular, and surrounds a projection 210s of the first cavity preset formation region. Therefore, when the etching liquid diffuses on the surface of the diaphragm 300, the time required for the electrochemical reaction between the etching liquid and the electric charge contact is basically the same, and the etching rate is improved.

Alternatively, referring to fig. 11 and 25, the slit preset formation region 220a includes a first side 221 facing the opening 211 and a second side 222 facing away from the opening 211, the first side 221 and the second side 222 being opposite to each other in a direction parallel to the substrate plane; along the thickness direction of the substrate, the projection 311s of the charge-injected portion of the diaphragm 300 is located within the range of the projection 220s of the slit preset formation region; the portion 311a into which electric charges are injected is closer to the second side 222 with respect to the first side 221 (refer to fig. 18 in which d1 is smaller than d 2). It will be appreciated that the opening 211 is exposed during the subsequent step of etching the first sacrificial layer 200 through the back cavity 101 to form the first cavity 210.

As can be appreciated, in the device, the depth of the slit 220 is much greater than the sum of the thicknesses of the second sacrificial layer 400 and the diaphragm 300, and thus, in the subsequent etching step, a portion of the etching liquid performs unidirectional lateral etching on the first sacrificial layer 200 of the slit preset formation region 220a through the opening 211; a part of the etching liquid performs lateral etching in two directions through the second release holes 310 formed in the charge-injected portion 311a of the diaphragm, thereby achieving synchronous etching in three directions (as indicated by arrows in fig. 25). In this synchronous etching process, the portion of the first sacrificial layer 200 between the second release hole 310 and the opening 211 may realize the relative etching from the second release hole 310 and from the opening 211 to the middle thereof, while the portion of the first sacrificial layer 200 between the second release hole 310 and the second side 222 only undergoes the unidirectional etching from the second release hole 310 to the second side 222, so that by setting d1 to be smaller than d2, the difference of etching conditions is balanced, and the overall etching time of the first sacrificial layer 200 to the slit preset formation region 220a is shortened.

In other embodiments, the portion 311a of the diaphragm into which the electric charges are injected may be the portion 310a of the diaphragm corresponding to the slit preset formation region, that is, the electric charges may be injected in the entire region of the portion 310a of the diaphragm corresponding to the slit preset formation region, thereby enabling the etching solution to etch the slit preset formation region 220a of the first sacrificial layer 200 more quickly, and improving the etching rate.

Referring to fig. 5, the preparation method may further include: a plurality of vent holes 320 are formed in the diaphragm 300. Thus, when the diaphragm 300 is impacted by a large sound pressure, the diaphragm 300 is prevented from being broken due to the failure of air leakage.

It is understood that the formation of the vent hole 320 on the diaphragm 300 is a conventional arrangement in the art, and thus, will not be described in detail herein.

In step S305, referring to fig. 6, a second sacrificial layer 400 is formed on the diaphragm 300. The second sacrificial layer 400 serves to space the diaphragm 300 from the backplate 500 to occupy a position for a second cavity 410 formed in a subsequent step. The spacing of the diaphragm 300 from the backplate 500 is defined by the thickness of the second sacrificial layer 400.

In some embodiments, the material of the second sacrificial layer 400 and the material of the first sacrificial layer 200 may be the same.

In this embodiment, the process of forming the second sacrificial layer 400 and the process of forming the first sacrificial layer 200 may be the same. Therefore, a detailed description is not given here. Of course, the present application does not exclude the case where the process of forming the second sacrificial layer 400 is not the same as the process of forming the first sacrificial layer 200.

In some embodiments, the second sacrificial layer 400 may refer to more than one sacrificial layer, and may include, for example, a first sub-layer and a second sub-layer (not shown) formed sequentially. In some embodiments, a first sub-layer is formed on the diaphragm 300, and then a portion of the first sub-layer is removed, so that a bump structure is formed on the first sub-layer; next, a second sub-layer is formed overlying the first sub-layer.

It will be appreciated that the second sub-layer is conformally formed on the first sub-layer based on the first sub-layer raised structure, and the back-plate 500 formed in a subsequent step is conformally formed on the second sub-layer, whereby the back-plate 500 raised structure is formed in the back-plate 500. The convex structure may prevent the diaphragm 300 from adhering to the backplate 500 during vibration.

In step S305, referring to fig. 7, a back plate 500 is formed on the second sacrificial layer 400.

Alternatively, the backplate 500 comprises a multilayer composite film of silicon nitride and polysilicon.

Specifically, the backplate 500 may be a laminated structure including a dielectric layer 510 and a structural layer 520 covering the dielectric layer 510. Advantageously, the mechanical strength of the back plate 500 is improved, and the problem of collapse of the back plate 500 at the suspended portion after the formation of the second cavity 410 in the subsequent step is avoided.

In this embodiment, the material of the dielectric layer 510 may be silicon nitride, and the material of the structural layer 520 may be polysilicon.

As yet another alternative embodiment, referring to fig. 17, forming the back plate 500 on the second sacrificial layer 400 includes: a second support structure 550a is formed to cover the sidewalls of the second sacrificial layer 400, and a back plate 500 connected to the second support structure 550a and located on the second sacrificial layer 400. Thus, the second supporting structure 550a plays a role of supporting the backplate 500 after the second sacrificial layer 400 is removed in a subsequent step, so that the backplate 500 is spaced apart from the diaphragm 300; in addition, the second support structure 550a may act as a lateral etch stop during a subsequent process of etching the second sacrificial layer 400 to form the second cavity 410.

Optionally, the second support structure 550a and the back plate 500 are the same material.

In this alternative specific example, forming the back plate 500 on the second sacrificial layer 400 may include: a backplate material is deposited, at least a portion of the backplate material being formed on the second sacrificial layer 400 to form the backplate 500, at least a portion of the backplate material covering sidewalls of the second sacrificial layer 400 to form the second support structure 550a. Thus, the back plate 500 and the second support structure 550a are simultaneously formed by the back plate material, saving process steps.

As yet another alternative embodiment, after forming the second support structure 550a, the method of preparing further includes: charge is injected in the second support structure 550 a. Thus, referring to fig. 18, the third release holes 550 are formed in the second support structure 550a in the subsequent step, so that the etching liquid can flow from the third release holes 550 and the second release holes 310 into the slit preset formation regions 220a for synchronous etching; on this basis, since the third release hole 550 is located at one side of the sidewall of the second sacrificial layer 400 and is a horizontal release hole along the substrate plane direction, the third release hole 550 is formed through electrochemical reaction, and thus the difficulty that the sidewall through hole cannot be realized by the conventional photolithography and etching process is solved.

Referring to fig. 8, after forming the back plate 500, the method may further include: a plurality of acoustic holes 540 are formed in the backplate 500, whereby sound waves can enter the second cavity 410 through the acoustic holes 540, causing the diaphragm 300 to vibrate up and down. It will be appreciated that the formation of the acoustic holes 540 in the backplate 500 is a conventional arrangement in the art and, therefore, will not be described in further detail herein.

As another alternative embodiment, after step S305, step S3102 is further included, referring to fig. 11, a first release hole 530 penetrating the back plate 500 in the thickness direction of the substrate is formed in a portion 530a of the back plate corresponding to the slit preset formation region.

In step S306, referring to fig. 10 to 12, a back cavity 101 is formed in the substrate 100; and removing at least a portion of the first sacrificial layer 200 to form the first cavity 210 and the slit 220, and removing at least a portion of the second sacrificial layer 400 to form the second cavity 410.

It should be understood that in step S306, the sequence of forming the back cavity 101, the first release hole 530, the first cavity 210, the slit 220, and the second cavity 410 is not limited, and those skilled in the art may adjust the sequence of forming the above parts according to actual process conditions.

It should also be appreciated that in another alternative embodiment, step S3102 is also included after step S305. Although step S3102 is shown in fig. 3 before step S306, in the actual manufacturing process, a person skilled in the art may adjust the forming sequence of the above parts according to the actual process conditions.

Optionally, the first release holes 530 are formed simultaneously in the step of forming the plurality of acoustic holes 540 in the backplate 500. The first release hole 530 may be formed through a photolithography, etching process. As an alternative embodiment, the first release hole 530 may be formed after the step of forming the back cavity 101. It should be appreciated that the first release hole 530 is formed before the second cavity 410 is formed and the second release hole 310 is formed.

Optionally, referring to fig. 9, after forming the back plate 500 on the second sacrificial layer 400, the preparation method further includes: the substrate 100 is thinned. Specifically, the substrate 100 may be flipped after forming the plurality of acoustic holes 540, and then the lower surface of the substrate 100 may be thinned. Next, a back cavity 101 is formed in the substrate 100.

In this embodiment, the method for forming the back cavity 101 in the substrate 100 may include: a patterned mask layer (not shown) is formed on the substrate 100 through a photolithography process, the patterned mask layer exposing a back cavity preset formation region 101a of the substrate 100, and the back cavity 101 is formed in the substrate 100 through an etching process.

As an alternative embodiment, referring to fig. 12, the first cavity 210, the slit 220, and the second cavity 410 are formed by a wet etching process, and a portion of the etching solution interacts with charges injected into the diaphragm 300 to perform an electrochemical reaction, so that a plurality of second release holes 310 are etched at corresponding positions of the diaphragm 300; etching the first sacrificial layer 200 through the back cavity 101 by a part of the etching liquid to form an opening 211 exposing a portion of the first sacrificial layer 200 located in the slit preset formation region 220a from one side of the first cavity 210; a portion of the etching liquid passes through the second release hole 310, and a portion of the etching liquid passes through the opening 211 to collectively etch a portion of the first sacrificial layer 200 located in the slit pre-formed region 220a, so as to form the slit 220.

In this embodiment, the portion 530a of the back plate corresponding to the slit preset formation region refers to a portion where the slit preset formation region 220a projects onto the back plate 500 in the thickness direction of the substrate.

It will be appreciated that, in performing the wet etching process, the etching solution may etch the second sacrificial layer 400 through the acoustic holes 540 in the backplate 500, and during this process, the etching solution may be required to be diffused to the positions of the second release holes 310 in the diaphragm 300 after the longitudinal etching and a certain degree of lateral etching. By forming the first release holes 530 in the portion 530a of the backplate corresponding to the slit preset formation region, the distance of the etching liquid for lateral etching is shortened, so that the etching liquid can etch the second sacrificial layer 400 through the first release holes 530 and flow to the portion 311a of the diaphragm into which the charges are injected, and interact with the charges injected in the diaphragm 300 to perform an electrochemical reaction, thereby improving etching efficiency.

Further, referring to fig. 11, in the thickness direction of the substrate, the projection 530s of the distribution area of the first release holes at least partially coincides with the projection 310s of the distribution area of the second release holes. Therefore, the transverse etching distance of the etching liquid is further shortened, and the etching efficiency is improved.

Further, in the thickness direction of the substrate, the projection 530s of the distribution area of the first release hole and the projection 310s of the distribution area of the second release hole may completely coincide, thereby enabling the etching liquid to etch directly from the first release hole 530 to the position of the second release hole 310 with the highest probability, so that the etching rate is faster.

Alternatively, forming a first release hole 530 penetrating the back plate 500 in the thickness direction of the substrate in a portion 530a of the back plate corresponding to the slit preset formation region, includes: injecting charges in a portion 530a of the back plate corresponding to the slit preset formation region; a wet etching process is performed, and a portion of the etching liquid interacts with charges injected in the backplate 500 to cause an electrochemical reaction, so that a plurality of first release holes 530 are etched at corresponding positions of the backplate 500.

It will be appreciated that in actual fabrication, the MEMS microphone is subjected to a number of high temperature processes, during which the second sacrificial layer 400 in the device is not removed, and under high temperature conditions, the second sacrificial layer 400 may generate impurities, in particular, for example, silicon-based impurities. If a release hole is formed in the backplate 500 in advance, silicon-based impurities generated in the second sacrificial layer 400 may accumulate in the release hole, causing a blockage, which is unfavorable for the etching solution to enter the device to release the sacrificial layer. And, the silicon-based impurities are difficult to be removed by the etching liquid, and after the second cavity 410 is formed, the silicon-based impurities may remain on the inner wall of the device, resulting in problems such as leakage and sensitivity failure.

The wet etching process performed to form the plurality of first release holes 530 may be the same wet etching process as the wet etching process to form the first cavity 210, the slit 220, and the second cavity 410, i.e., the plurality of first release holes 530 are formed in the same process as the first cavity 210, the slit 220, and the second cavity 410.

By injecting the charges only in the preceding step, the first release hole 530 is not formed in advance, and in the process of releasing the sacrificial layer by performing the wet etching process finally, the first release hole 530 is formed by using the electrochemical reaction between the charges and the etching liquid, so that the influence of the impurity on the etching rate caused by blocking the release hole formed in advance can be avoided.

In this embodiment, the process of injecting charges in the portion 530a of the backplate corresponding to the slit pre-formed region may be the same as the process of injecting charges in the portion of the diaphragm 300 corresponding to the slit pre-formed region 220 a.

It will be appreciated that if the charge injected on the backplate 500 is negative, when it contacts positive ions in the etching solution, an electric field is generated which attracts the positive ions towards the surface of the backplate 500, promoting chemical reaction of the positive ions with the surface of the backplate 500, thereby accelerating the etching solution to attack the portion of the injected charge, forming the first release holes 530. Similarly, if the charges injected on the backplate 500 are positive charges, it may also accelerate the etching solution to attack the portion where the charges are injected.

In the related art, it is desirable to avoid the etching liquid from corroding the diaphragm 300 and the backplate 500 as much as possible. In this embodiment, by injecting an electric charge, the etching solution is accelerated to erode the material of the diaphragm 300 (and the backplate 500), so that the diaphragm 300 (and the backplate 500) is etched through at the position where the second release holes 310 (and the first release holes 530) are required to be formed, providing more channels for the inflow of the etching solution.

In the related art, the minimum value of the aperture of the acoustic hole 540 formed on the MEMS microphone backplate 500 is around 2 μm to 3 μm; in this embodiment, the aperture of the first release hole 530 formed by the electrochemical reaction is nano-sized, and can be as small as several tens of nanometers. The risk of poor mechanical strength of the back plate 500 due to large aperture of the first release hole 530 is avoided, the reliability of the device is improved, and at the same time, miniaturization of the device is facilitated.

It will be appreciated that the process of forming release holes by electrochemical reaction can be applied to the formation of nanoscale holes in any device where there is a need for nanoscale holes. In particular, for example, a dust cover of a microphone, nanoscale holes formed through electrochemical reaction can avoid the condition that micron-sized particles enter a device through a traditional micron-sized release hole to cause product failure.

In the actual preparation process, the aperture and the density of the first release holes 530 can be adjusted by controlling the power, the gas flow, the pressure and other factors of the plasma process according to specific requirements.

Referring to fig. 11, a portion of the etching solution etches the second sacrificial layer 400 through the first release holes 530 and the acoustic holes 540 on the backplate 500, and in the process of forming the second cavity 410, the etching solution interacts with charges injected into the diaphragm 300 to perform an electrochemical reaction, so that the corresponding positions of the diaphragm 300 are etched to form a plurality of second release holes 310.

In the related art, the minimum value of the aperture of the vent hole 320 formed on the MEMS microphone diaphragm 300 is about 0.2 μm to 0.3 μm; in this embodiment, the aperture of the second release hole 310 is nano-scale, and can be as small as several tens of nanometers. The risk of poor mechanical strength of the diaphragm 300 due to the large aperture of the second release hole 310 is avoided, the reliability of the device is improved, and simultaneously, the miniaturization of the device is facilitated.

In the actual preparation process, the aperture and the density of the second release holes 310 can be adjusted by controlling the factors such as the power, the gas flow, the pressure, etc. of the plasma process according to specific requirements.

Referring to fig. 11 and 12, while a portion of the etching liquid is in contact with the back plate 500, the portion of the etching liquid etches the first sacrificial layer 200 through the back cavity 101, forming an opening 211 exposing a portion of the first sacrificial layer 200 located within the slit preset formation region 220a from one side of the first cavity 210; a portion of the etching liquid passes through the second release hole 310, and a portion of the etching liquid passes through the opening 211 to collectively etch a portion of the first sacrificial layer 200 located in the slit pre-formed region 220a, so as to form the slit 220. Thereby, the etching speed of the portion of the first sacrificial layer 200 located in the slit preset formation region 220a is increased, the diaphragm 300 and the backplate 500 are prevented from being excessively eroded, particularly the diaphragm 300, and the mechanical reliability of the device is improved.

As an alternative embodiment, referring to fig. 16 and 17, a plurality of fourth release holes 340 penetrating the first support structure 340a in the substrate plane direction are etched in the first support structure 340 a; etching the first sacrificial layer 200 through the back cavity 101 by a part of the etching liquid to form an opening 211 exposing a portion 220a of the first sacrificial layer located in the slit preset formation region from one side of the first cavity 201; part of the etching liquid passes through the fourth release hole 340, and part of the etching liquid passes through the opening 211 to collectively etch the portion 220a of the first sacrificial layer located in the slit preset formation region to form the slit 220. Thereby, the synchronous etching of the first sacrificial layer 220 in the slit preset formation region 220a in two directions is realized, and the etching rate is accelerated.

In the present embodiment, the pore diameter of the fourth release hole 340 is nano-scale, and can be as small as several tens of nanometers. The risk of poor supporting strength of the first supporting structure 340a due to the large aperture of the fourth release hole 340 is avoided, the reliability of the device is improved, and at the same time, the miniaturization of the device is facilitated.

In the actual preparation process, the aperture and the density of the fourth release holes 340 can be adjusted by controlling factors such as the power, the gas flow, the pressure and the like of the plasma process according to specific requirements.

As yet another alternative embodiment, referring to fig. 19 and 20, a portion of the etching solution interacts with the injected charges to perform an electrochemical reaction, so that a portion 310a of the diaphragm corresponding to the slit is etched to form a plurality of second release holes 310 penetrating the diaphragm 300 in the thickness direction of the substrate; a plurality of third release holes 550 etched in the second support structure 550a through the second support structure 550a in the direction of the substrate plane; etching the first sacrificial layer 200 through the back cavity 101 by a part of the etching liquid to form an opening 221 exposing a portion 220a of the first sacrificial layer located in the slit preset formation region from one side of the first cavity 210; a portion of the etching liquid passes through the second release hole 310 and a portion of the etching liquid passes through the opening 221 to collectively etch the portion 220a of the first sacrificial layer located in the slit pre-set formation region to form the slit 220. Thereby, the etching liquid can flow from the third release holes 550 and the second release holes 310 into the slit pre-formed regions 220a, accelerating the etching rate.

In the present embodiment, the aperture of the third release hole 550 is nano-sized, and may be as small as several tens of nanometers. The risk of poor supporting strength of the second supporting structure 550a due to the large aperture of the third release hole 550 is avoided, the reliability of the device is improved, and at the same time, the miniaturization of the device is facilitated.

In the actual preparation process, the aperture and the density of the third release holes 550 can be adjusted by controlling factors such as the power, the gas flow, the pressure and the like of the plasma process according to specific requirements.

As still another alternative embodiment, referring to fig. 21 and 22, a portion of the etching solution interacts with the injected charges to perform an electrochemical reaction, so that a portion 310a of the diaphragm corresponding to the slit is etched to form a plurality of second release holes 310 penetrating the diaphragm 300 in the thickness direction of the substrate; a plurality of third release holes 550 etched in the second support structure 550a through the second support structure 550a in the direction of the substrate plane; etching the first sacrificial layer 200 through the back cavity 101 by a part of the etching liquid to form an opening 221 exposing a portion 220a of the first sacrificial layer located in the slit preset formation region from one side of the first cavity 210; a portion of the etching liquid passes through the second release hole 310 and a portion of the etching liquid passes through the opening 221 to collectively etch the portion 220a of the first sacrificial layer located in the slit pre-set formation region to form the slit 220. Thereby, the etching liquid may flow from the first release hole 530, the third release hole 550, and the second release hole 310 into the slit preset formation area 220a, accelerating the etching rate.

As an alternative embodiment, referring to fig. 23 and 24, a portion of the etching solution interacts with the injected charges to perform an electrochemical reaction, so that a portion 310a of the diaphragm corresponding to the slit is etched to form a plurality of second release holes 310 penetrating the diaphragm 300 in the thickness direction of the substrate; a plurality of third release holes 550 etched in the second support structure 550a through the second support structure 550a in the direction of the substrate plane; a plurality of fourth release holes 340 etched in the first support structure 340a to penetrate the first support structure 340a in the substrate plane direction; etching the first sacrificial layer 200 through the back cavity 101 by a part of the etching liquid to form an opening 221 exposing a portion 220a of the first sacrificial layer located in the slit preset formation region from one side of the first cavity 210; part of the etching liquid passes through the second release hole 310, part of the etching liquid passes through the opening 221, and part of the etching liquid passes through the fourth release hole 340, and the part 220a of the first sacrificial layer located in the slit preset formation region is etched together to form the slit 220. Thus, the etching liquid may flow from the first, third, second and fourth release holes 530, 550, 310 and 340 into the slit preset formation regions 220a to accelerate the etching rate.

Optionally, the preparation method may further include: pads (not shown) are formed, which are electrically connected to the diaphragm 300.

As can be appreciated, the MEMS microphone utilizes the diaphragm 300 to form a variable capacitance with the backplate 500, and the change in capacitance is achieved by the vibration of the diaphragm 300, converting an acoustic signal into an electrical signal, so that the diaphragm 300 can be regarded as a lower plate of the variable capacitance, and thus the lower plate can be electrically led out through a pad.

The embodiment of the application further provides a MEMS microphone, please refer to fig. 23, the MEMS microphone includes:

a substrate 100, a back cavity 101 being formed in the substrate 100;

the diaphragm 300 and the first support structure 340a, the first support structure 340a is located between the substrate 100 and the diaphragm 300, such that the diaphragm 300 is disposed above the substrate 100 at intervals;

the first cavity 210 and the slit 220 are positioned in the region where the diaphragm 300 and the substrate 100 are spaced, the first cavity 210 coincides with the back cavity 101 along the thickness direction of the substrate, and the slit 220 is positioned at the periphery of the first cavity 210 and is communicated with the first cavity 210;

a backplate 500 and a second support structure 550a, the second support structure 550a being positioned between the diaphragm 300 and the backplate 500 such that the backplate 500 is spaced above the diaphragm 300;

Wherein,

the portion 560 of the back plate corresponding to the slit has a first release hole 530 formed therethrough in the thickness direction of the substrate, and the portion 330 of the diaphragm corresponding to the slit has a plurality of second release holes 310 formed therethrough in the thickness direction of the substrate, the second release holes penetrating the diaphragm 300; the plurality of second release holes 310 are etched by an electrochemical reaction by the interaction of the etching liquid and charges injected in the diaphragm 300 in the wet etching process;

and/or, a plurality of third release holes 550 penetrating the second support structure 550a in the substrate plane direction are formed in the second support structure 550a, and a plurality of second release holes 310 penetrating the diaphragm 300 in the substrate thickness direction are formed in the portion 330 of the diaphragm corresponding to the slit; the plurality of second release holes 310 are etched by an electrochemical reaction by the interaction of the etching liquid and charges injected in the diaphragm 300 in the wet etching process; the plurality of third release holes 550 are etched using an etching solution that interacts with charges injected in the second support structure 550a to generate an electrochemical reaction in a wet etching process;

and/or, a plurality of fourth release holes 340 penetrating the first support structure 340a in the substrate plane direction are formed in the first support structure 340 a; the plurality of fourth release holes 340 are etched using an etching liquid that interacts with charges injected in the first support structure 340a to perform an electrochemical reaction in a wet etching process.

As can be appreciated, in the MEMS microphone provided by the embodiment of the present application, by providing the second release hole and/or the fourth release hole, in the process of forming the slit, the etching solution may not only flow into the preset formation area of the slit through the opening, but also flow into the preset formation area of the slit through the second release hole and/or the fourth release hole, so that a channel for flowing the etching solution into the preset formation area of the slit is increased, etching efficiency is improved, etching solution is prevented from accumulating in a deep part of the slit, and damage to the diaphragm and the back plate caused by excessively long etching time is avoided; and each release hole is etched by utilizing the interaction of etching liquid and injected charges in a wet etching process to generate electrochemical reaction, so that the release holes do not need to be pre-buried, and the problem that the pre-buried release holes are blocked by impurities released by a sacrificial layer in high-temperature treatment of a production process, so that the release holes cannot be opened to influence the etching rate is avoided; the number of the formed release holes is multiple, so that the contact path between etching liquid and the sacrificial layer is increased, and the etching efficiency is improved; moreover, the etching solution and injected charges interact to generate electrochemical reaction to etch the material to form the release holes in the wet etching process, so that the difficulty that the side wall through holes cannot be realized by the traditional photoetching and etching process is solved, and the process implementation reliability of the release holes formed at the proper positions of the device structure is ensured; finally, the mechanical reliability of the device is ensured.

It will further be appreciated that the plurality of second relief holes 310 etched by the electrochemical reaction of the etching liquid interacting with the charge injected in the diaphragm 300 during the wet etching process are clearly different from those formed by the photolithography and etching processes. Specifically, for example, the position, shape, aperture and the like of the hole formed by the photoetching and etching process are determined by the pattern on the mask plate; the position, shape, and pore diameter of the plurality of second release holes 310 formed by the electrochemical reaction are determined by the position of the injected charges and the distribution of the charges. Therefore, the plurality of second release holes 310 are etched by the electrochemical reaction of the etching liquid interacting with charges injected into the diaphragm 300 in the wet etching process, which affects the structure of the plurality of second release holes 310.

In this embodiment, the portion 550 of the back plate corresponding to the slit refers to a portion where the slit 220 projects on the back plate 500 in the thickness direction of the substrate.

In this embodiment, the portion 330 of the diaphragm corresponding to the slit refers to a portion where the slit 220 projects onto the diaphragm 300 in the thickness direction of the substrate.

Referring to fig. 23, the number of the first release holes 530 is plural, and the plurality of first release holes 530 are etched by the electrochemical reaction of the etching solution and the charges injected into the backplate 500 in the wet etching process.

The first release hole 530 is formed by the electrochemical reaction between the electric charge and the etching liquid in the wet etching process, so that the problem that impurities generated in the process block the release hole formed in advance to influence the etching rate can be avoided; the plurality of the first release holes 530 are formed, which is more beneficial to accelerating the etching speed of the etching liquid; the first release hole 530 formed by the electrochemical reaction has a diameter of nano-scale, and can be as small as several tens of nanometers. The risk of poor mechanical strength of the diaphragm 300 caused by large aperture of the release hole is avoided, the reliability of the device is improved, and meanwhile, the miniaturization of the device is facilitated.

Referring to fig. 19, a plurality of third release holes 550 penetrating the second support structure 550a along the substrate plane direction are formed in the second support structure 550a, and the plurality of third release holes 550 are etched by using an interaction between an etching liquid and charges injected into the second support structure 550a in a wet etching process to generate an electrochemical reaction. The third release hole 550 is formed by the electrochemical reaction of the electric charge and the etching liquid in the wet etching process, so that the problem that impurities generated in the process block the release hole formed in advance to influence the etching rate can be avoided; moreover, the difficulty that the horizontal through hole at the side wall position cannot be realized by the traditional photoetching and etching process is overcome; the number of the formed third release holes 550 is more favorable for accelerating the etching speed of the etching liquid; the third release hole 550 formed by the electrochemical reaction has a diameter of nano-scale, and can be as small as several tens of nanometers. The risk of poor supporting strength of the second supporting structure 550a caused by large aperture of the release hole is avoided, and the reliability of the device is improved.

Referring to fig. 16, a plurality of fourth release holes 340 penetrating the first support structure 340a along the substrate plane direction are formed in the first support structure 340a, and the plurality of fourth release holes 340 are etched by using an etching solution interacting with charges injected in the first support structure 340a in a wet etching process to perform an electrochemical reaction. The fourth release hole 340 is formed by the electrochemical reaction of the electric charge and the etching liquid in the wet etching process, so that the problem that impurities generated in the process block the release hole formed in advance to influence the etching rate can be avoided; moreover, the difficulty that the horizontal through hole at the side wall position cannot be realized by the traditional photoetching and etching process is overcome; the number of the fourth release holes 340 is more favorable for accelerating the etching speed of the etching liquid; the fourth release hole 340 formed by the electrochemical reaction has a diameter of nano-scale, and can be as small as several tens of nanometers. The risk of poor supporting strength of the first supporting structure 340a caused by large aperture of the release hole is avoided, and the reliability of the device is improved.

Optionally, the first support structure 340a and the diaphragm 300 are of the same material; and/or the second support structure 550a and the back plate 550 are the same material. As can be appreciated, in actual production, the first support structure 340a is formed at the sidewall of the sacrificial layer using a process of preparing the diaphragm 300; the second support structures 550a are formed on the sidewalls of the sacrificial layer using a process of preparing the backplate 500.

Referring to fig. 12, the slit 220 includes a first side 221 facing the first cavity 210 and a second side 222 facing away from the first cavity 210, the first side 221 and the second side 222 being opposite to each other in a direction parallel to the substrate plane; the distance D1 between the second release hole 310 closest to the second side 222 and the second side 222 of the plurality of second release holes 310 is smaller than the distance D2 between the second release hole 310 closest to the first side 221 and the first side 221.

As can be appreciated, in the device, the depth of the slit 220 is much greater than the spacing between the back plate 500 and the slit 220 in the thickness direction of the substrate, so that in the process of forming the slit 220, part of the etching liquid performs unidirectional lateral etching on the first sacrificial layer 200 from the side facing the first cavity 210; the partial etching liquid performs lateral etching of the first sacrificial layer 200 in two directions through the second release holes 310, thereby achieving synchronous etching in three directions. In this synchronous etching process, the portion of the first sacrificial layer 200 between the second release hole 310 and the first side 221 may realize the relative etching from the second release hole 310 and from the first side 221 to the middle thereof, while the portion of the first sacrificial layer 200 between the second release hole 310 and the second side 222 only performs the unidirectional etching from the second release hole 310 to the second side 222, thus balancing the difference of etching conditions by setting D1 to be smaller than D2, and shortening the overall etching time of the first sacrificial layer 200 for the slit preset formation region 220 a.

Referring to fig. 26, projections of the plurality of second release holes are distributed over an annular region (refer to projections 310s of the distribution region of the second release holes) along the thickness direction of the substrate, and the annular region surrounds the projections 210s of the first cavity.

Therefore, the time required for the etching liquid to diffuse on the surface of the diaphragm 300 is basically the same, and the etching rate is improved.

It will be appreciated that, in order to clearly show the relationship between the projection of the second release holes and the annular structure, the size, density, etc. of the projections of the second release holes are changed to some extent, and fig. 26 only schematically shows the distribution of the projections of the plurality of second release holes over an annular area.

It will be appreciated that in some alternative embodiments of the present embodiment, by providing the second release hole 310 and/or the fourth release hole 340, a path through which the etching liquid flows is increased; on the basis of providing the second release holes 310 in the device, in some alternative embodiments, the path of the etching solution flowing in can be increased by providing the first release holes 530 and/or the third release holes 550, so as to increase the etching speed.

It should be noted that, the MEMS microphone embodiment provided in the present application and the MEMS microphone manufacturing method embodiment belong to the same concept; the features of the embodiments described in the present invention may be combined arbitrarily without any conflict.

It should be understood that the above examples are illustrative and are not intended to encompass all possible implementations encompassed by the claims. Various modifications and changes may be made in the above embodiments without departing from the scope of the disclosure. Likewise, the various features of the above embodiments may be combined arbitrarily to form further embodiments of the application that may not be explicitly described. Thus, the above examples merely represent several embodiments of the present application and do not limit the scope of protection of the patent of the present application.

Claims

1. A method of manufacturing a MEMS microphone, the method comprising:

forming a diaphragm on the first sacrificial layer;

forming a second sacrificial layer on the diaphragm;

forming a back plate on the second sacrificial layer;

Wherein,

2. The method of manufacturing a MEMS microphone according to claim 1, wherein the forming a first release hole in a portion of the back plate corresponding to the slit pre-formed region comprises: injecting charges in a portion of the back plate corresponding to the slit preset formation region; and performing a wet etching process, wherein part of etching liquid interacts with charges injected into the backboard to perform electrochemical reaction, so that a plurality of first release holes are etched at corresponding positions of the backboard.

3. The method of manufacturing a MEMS microphone according to claim 1,

the slit preset formation region includes a first side toward the opening and a second side away from the opening, the first and second sides being opposite each other in a direction parallel to a substrate plane;

4. The method of claim 1, wherein the projection of the charge injected portion of the diaphragm is annular in shape and surrounds the projection of the first cavity pre-formed region in the thickness direction of the substrate.

5. The method of manufacturing a MEMS microphone according to any of claims 1-4, wherein the projection of the first release hole and the projection of the second release hole at least partially coincide in the thickness direction of the substrate.

6. A method of manufacturing a MEMS microphone according to claim 1 or 2, wherein the charge is injected by oxygen plasma.

7. The method of manufacturing a MEMS microphone according to claim 1,

The first support structure and the vibrating diaphragm are made of the same material; and/or the second support structure and the back plate are the same material.

8. A MEMS microphone, comprising:

a substrate in which a back cavity is formed;

wherein,

9. The MEMS microphone of claim 8, wherein the number of first release holes is a plurality, the plurality of first release holes being etched using an etching liquid that interacts with charges injected in the backplate to cause an electrochemical reaction in a wet etching process.

10. The MEMS microphone of claim 8, wherein the MEMS microphone is configured to receive a signal from a microphone,

the slit comprises a first side facing the first cavity and a second side facing away from the first cavity, the first side and the second side being opposite each other in a direction parallel to the substrate plane;

11. The MEMS microphone of claim 8, wherein the projections of the plurality of second release holes are distributed over an annular region along the thickness of the substrate, the annular region surrounding the projections of the first cavity.

12. The MEMS microphone of claim 8, wherein the first support structure and the diaphragm are of the same material; and/or the second support structure and the back plate are the same material.