CN116300533A - MEMS microphone and manufacturing method thereof - Google Patents

Abstract

The application discloses a MEMS microphone and a manufacturing method thereof, wherein the manufacturing method comprises the following steps: sequentially forming a first sacrificial layer, a vibrating diaphragm, a second sacrificial layer and a back plate on the first surface of the substrate, and forming a plurality of back plate sound holes on the back plate, wherein part of the second sacrificial layer is exposed out of the back plate sound holes; forming a third sacrificial layer on the backboard, wherein the third sacrificial layer fills the backboard sound hole, and part of the backboard is exposed at the circumferential edge of the third sacrificial layer; forming a cover plate on the third sacrificial layer and on a part of the backboard exposed at the peripheral edge of the third sacrificial layer, and forming a plurality of cover plate sound holes in the cover plate on the third sacrificial layer, wherein part of the third sacrificial layer is exposed out of the cover plate sound holes; and forming a back hole on the second surface of the substrate, and releasing the first sacrificial layer, the second sacrificial layer and the third sacrificial layer. According to the MEMS microphone and the manufacturing method thereof, the MEMS microphone is not easy to damage and fail when falling down.

Description

MEMS microphone and manufacturing method thereof

Technical Field

The application relates to the technical field of semiconductor devices, in particular to a MEMS microphone and a manufacturing method thereof.

Background

At present, a microphone with more application and better performance is a Micro-Electro-Mechanical-System Microphone (Micro-Electro-Mechanical-System Microphone), also called a silicon-based condenser microphone, hereinafter referred to as a MEMS microphone. The MEMS microphone is an electroacoustic transducer manufactured by micro-machining technology, and has the characteristics of small volume, good frequency response characteristic, low noise and the like.

At present, an MEMS microphone is mostly composed of a silicon substrate, and a diaphragm and a back plate which are positioned on the silicon substrate, wherein the back plate is usually exposed in air, a back plate sound hole is formed in the back plate to receive external sound, a cavity is formed between the diaphragm and the back plate, a plate capacitor is composed of the diaphragm and the back plate, the diaphragm and the back plate are respectively used as two electrodes of the plate capacitor, and the diaphragm vibrates under the action of sound waves to change the distance between the diaphragm and the back plate, so that the capacitance of the plate capacitor is changed, and therefore sound wave signals can be converted into electric signals.

Since the backplate is typically exposed to air, when the MEMS microphone is dropped, the backplate is fragile, causing the MEMS microphone to fail.

There is therefore a need for an improvement to at least partially solve the above-mentioned problems.

Disclosure of Invention

In the summary, a series of concepts in a simplified form are introduced, which will be further described in detail in the detailed description. The summary of the invention is not intended to define the key features and essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

In order to at least partially solve the above-mentioned problems, according to a first aspect of the present invention, there is provided a method of manufacturing a MEMS microphone, comprising the steps of:

sequentially forming a first sacrificial layer, a vibrating diaphragm, a second sacrificial layer and a back plate on a first surface of a substrate, and forming a plurality of back plate sound holes on the back plate, wherein part of the second sacrificial layer is exposed out of the back plate sound holes;

forming a third sacrificial layer on the back plate, wherein the third sacrificial layer fills the back plate sound hole, and a part of the back plate is exposed at the circumferential edge of the third sacrificial layer;

forming a cover plate on the third sacrificial layer and part of the back plate exposed at the peripheral edge of the third sacrificial layer, and forming a plurality of cover plate sound holes in the cover plate on the third sacrificial layer, wherein part of the third sacrificial layer is exposed by the cover plate sound holes;

and forming a back hole on the second surface of the substrate, releasing the first sacrificial layer, the second sacrificial layer and the third sacrificial layer to form a first cavity in the first sacrificial layer, a second cavity between the back plate and the vibrating diaphragm and a third cavity between the cover plate and the back plate, wherein the second cavity and the third cavity are communicated through the back plate sound hole.

Illustratively, in the sound inlet direction of the MEMS microphone, the back plate sound holes and the cover plate sound holes are staggered.

Illustratively, the backplate includes a first insulating layer, a conductive layer, and a second insulating layer;

forming a back plate on the second sacrificial layer, and forming a back plate sound hole on the back plate, wherein part of the second sacrificial layer is exposed out of the back plate sound hole, and the method comprises the following steps:

forming the first insulating layer on the second sacrificial layer;

forming the conductive layer on the first insulating layer;

forming the second insulating layer on the conductive layer;

etching the second insulating layer, the conducting layer and the first insulating layer to form a backboard sound hole penetrating through the second insulating layer, the conducting layer and the first insulating layer, wherein part of the second sacrificial layer is exposed out of the backboard sound hole.

Illustratively, forming a back hole on the second surface of the substrate, and before releasing the first, second and third sacrificial layers, further comprises:

forming a connection hole, wherein the connection hole penetrates through the cover plate and the second insulating layer outside the third sacrificial layer, and exposes a part of the conductive layer;

and forming a metal electrode in the connection hole.

Illustratively, the substrate material comprises silicon;

the materials of the first sacrificial layer, the second sacrificial layer and the third sacrificial layer all comprise silicon oxide;

the material of the vibrating diaphragm comprises polysilicon;

the materials of the first insulating layer and the second insulating layer comprise silicon nitride;

the material of the conductive layer comprises polysilicon;

the cover plate is made of silicon nitride.

According to a second aspect of the present invention, there is provided a MEMS microphone comprising:

a substrate, wherein a second surface of the substrate is provided with a back hole;

the first sacrificial layer is positioned on the first surface of the substrate, and a first cavity is formed in the middle of the first sacrificial layer;

a diaphragm located on the first sacrificial layer;

the backboard is positioned at one side of the vibrating diaphragm away from the first sacrificial layer, a second cavity is formed between the backboard and the vibrating diaphragm, and a plurality of backboard sound holes are formed in the backboard;

the cover plate is positioned on one side of the back plate away from the vibrating diaphragm, a third cavity is formed between the cover plate and the back plate, and a plurality of cover plate sound holes are formed in the cover plate.

Illustratively, in the sound inlet direction of the MEMS microphone, the back plate sound holes and the cover plate sound holes are staggered.

Illustratively, the backplate includes a first insulating layer, a conductive layer, and a second insulating layer;

the first insulating layer is located the backplate is towards one side of vibrating diaphragm, the conducting layer is located first insulating layer is kept away from one side of vibrating diaphragm, the second insulating layer is located the conducting layer is kept away from one side of first insulating layer, the apron is located the second insulating layer is kept away from one side of conducting layer, backplate sound hole runs through first insulating layer conducting layer and second insulating layer.

Illustratively, the MEMS microphone further comprises a connection hole and a metal electrode;

the connecting hole penetrates through the cover plate and the second insulating layer outside the third cavity, and part of the conducting layer is exposed;

the metal electrode is positioned in the connecting hole and is connected with the conductive layer in a conductive way.

Illustratively, the substrate material comprises silicon;

the material of the first sacrificial layer comprises silicon oxide;

the material of the vibrating diaphragm comprises polysilicon;

the materials of the first insulating layer and the second insulating layer comprise silicon nitride;

the material of the conductive layer comprises polysilicon;

the cover plate is made of silicon nitride.

According to the MEMS microphone and the manufacturing method thereof, the cover plate is arranged on one side of the back plate of the MEMS microphone, which is far away from the vibrating diaphragm, the cavity is arranged between the cover plate and the back plate, the cover plate and the cavity can effectively protect the back plate, when the MEMS microphone falls, the cover plate can replace the back plate to be contacted with the ground, the damage risk of the back plate when the back plate falls is effectively reduced, the back plate is not easy to damage even if the cover plate is damaged and broken after being contacted with the ground, and the MEMS microphone can be used continuously without failure as long as the back plate is not damaged, so that the reliability of the MEMS microphone can be effectively improved, and the service life of the MEMS microphone is prolonged.

Drawings

The following drawings of the present application are included to provide an understanding of the present application as part of the present application. The drawings illustrate embodiments of the present application and their description to explain the principles and devices of the present application. In the drawings of which there are shown,

FIG. 1 is a schematic cross-sectional view of a MEMS microphone according to an embodiment of the application;

FIG. 2 is a schematic cross-sectional view of a MEMS microphone according to another embodiment of the application;

FIG. 3 is a flow chart of a method of fabricating the MEMS microphone of FIG. 1;

fig. 4A to 4F are schematic cross-sectional views corresponding to respective steps in the method of manufacturing the MEMS microphone in fig. 1.

Reference numerals illustrate:

100-substrate, 110-back hole, 200-first sacrificial layer, 210-first cavity, 300-diaphragm, 400-second sacrificial layer, 410-second cavity, 420-groove, 500-back plate, 510-first insulating layer, 511-blocking piece, 520-conductive layer, 530-second insulating layer, 540-back plate sound hole, 600-third sacrificial layer, 610-third cavity, 700-cover plate, 710-cover plate sound hole, 800-connecting hole, 900-metal electrode;

400 '-second sacrificial layer, 410' -second cavity, 500 '-back plate, 530' -second insulating layer.

Detailed Description

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, some features well known in the art have not been described in order to avoid obscuring the present application.

It should be understood that the present application may be embodied in various forms and should not be construed as limited to the 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 application to those skilled in the art. In the drawings, the size of layers and regions, as well as the relative sizes, may be exaggerated for clarity. Like numbers refer to like elements throughout.

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.

Spatially relative terms, such as "under," "below," "beneath," "under," "above," "over," 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.

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.

Embodiments of the invention are described herein with reference to cross-sectional illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of the present application. In this way, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments of the present application should not be limited to the particular shapes shown herein, but rather include deviations in shapes that result, for example, from manufacturing. Thus, the illustrations shown in the figures are schematic in nature, their shapes are not intended to illustrate the actual shape of a device and are not intended to limit the scope of the present application.

A MEMS microphone according to an embodiment of the present application is exemplarily described with reference to fig. 1. The MEMS microphone includes a substrate 100, a first sacrificial layer 200, a diaphragm 300, a backplate 500, and a cover plate 700.

In the embodiment of the present application, the substrate 100 is made of silicon. The first sacrificial layer 200 is disposed on the first surface of the substrate 100, and the second surface of the substrate 100 has a back hole 110, wherein the back hole 110 penetrates through the substrate 100. In other embodiments, the material of the substrate 100 may be at least one of the following materials: germanium, silicon carbide, 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 first sacrificial layer 200 has a first cavity 210 in the middle thereof, which communicates with the back hole 110. In this embodiment, the material of the first sacrificial layer 200 is silicon oxide. In other embodiments, the material of the first sacrificial layer 200 may be silicon nitride or silicon oxynitride.

The diaphragm 300 is positioned on the first sacrificial layer 200, and the circumferential edge of the diaphragm 300 is supported by the first sacrificial layer 200. In the embodiment of the present application, the material of the diaphragm 300 is polysilicon. In other embodiments, the diaphragm 300 may be made of monocrystalline silicon or conductive metal (e.g., aluminum or other suitable metal materials).

The backplate 500 is located on a side of the diaphragm 300 remote from the first sacrificial layer 200, with a second cavity 410 between the backplate 500 and the diaphragm 300. In the present embodiment, the backplate 500 includes a first insulating layer 510, a conductive layer 520, and a second insulating layer 530. The first insulating layer 510 is located on a side of the backplate 500 facing the diaphragm 300, a second cavity 410 is provided between the first insulating layer 510 and the diaphragm 300, and a plurality of blocking blocks 511 protruding toward the diaphragm 300 are disposed on a side of the first insulating layer 510 facing the diaphragm 300, and the blocking blocks 511 are used for preventing the backplate 500 from adhering when the diaphragm 300 vibrates. The conductive layer 520 is located on a side of the first insulating layer 510 away from the diaphragm 300, and the conductive layer 520 and the diaphragm 300 form a flat plate capacitor. The second insulating layer 530 is located on a side of the conductive layer 520 away from the diaphragm 300. In this embodiment, the material of the conductive layer 520 is polysilicon, the material of the first insulating layer 510 and the second insulating layer 530 is silicon nitride, and the strength of the back plate 500 can be effectively improved due to the arrangement of the first insulating layer 510 and the second insulating layer 530. The backplate 500 has a plurality of backplate acoustic holes 540 communicated with the first cavity 210, the backplate acoustic holes 540 penetrate through the first insulating layer 510, the conductive layer 520 and the second insulating layer 530, and sound waves from outside can enter the second cavity 410 between the backplate 500 and the diaphragm 300 through the backplate acoustic holes 540, so as to drive the diaphragm 300 to vibrate. In the embodiment of the present application, the diaphragm 300 has a plurality of release holes (not shown in the drawings), which communicate the second cavity 410 with the first cavity 210, so as to balance the air pressure when the sound wave acts, that is, act as air leakage. In other embodiments, the backplate 500 may include only the conductive layer 520 and the second insulating layer 530, without the first insulating layer 510.

In the embodiment of the present application, the circumferential edge of the second insulating layer 530 extends toward the first sacrificial layer 200 and the substrate 100, and is connected to the first sacrificial layer 200 and the substrate 100, so that the backplate 500 is supported on the first sacrificial layer 200 and the substrate 100, thereby forming the second cavity 410 between the backplate 500 and the diaphragm 300. In other embodiments, the peripheral edge of the second insulating layer 530 may also extend toward the diaphragm 300 and be connected to the diaphragm 300 such that the backplate 500 is supported on the diaphragm 300. Referring to fig. 2, in the MEMS microphone according to another embodiment of the present application, a second sacrificial layer 400 'is disposed on a diaphragm 300, a backplate 500' (including a first insulating layer 510, a conductive layer 520, and a second insulating layer 530 ') is disposed on the second sacrificial layer 400', a second cavity 410 'is provided in the middle of the second sacrificial layer 400' (i.e., a second cavity 410 'is provided between the backplate 500' and the diaphragm 300), and a circumferential edge of the second insulating layer 530 'in the backplate 500' may not extend toward the first sacrificial layer 200 and the substrate 100.

The cover plate 700 is located at a side of the back plate 500 away from the diaphragm 300, a third cavity 610 is provided between the cover plate 700 and the back plate 500, the third cavity 610 communicates with the second cavity 410 through the back plate sound holes 540, and a plurality of cover plate sound holes 710 communicating with the third cavity 610 are provided in the cover plate 700. Thus, the external sound wave may sequentially pass through the cover plate sound hole 710, the third cavity 610, the back plate sound hole 540, and the second cavity 410, so as to drive the diaphragm 300 to vibrate. The material of the cover plate 700 may be the same as that of the first insulating layer 510 and the second insulating layer 530, and may be silicon nitride. In other embodiments, the cover 700 may be made of a material with a relatively high hardness, such as silicon carbide. Therefore, the cover plate 700 and the third cavity 610 can effectively protect the back plate 500, when the MEMS microphone falls, the cover plate 700 can replace the back plate 500 to be in contact with the ground, so that the risk of damage of the back plate 500 when falling is effectively reduced, even if the cover plate 700 is damaged and broken after being in contact with the ground, the damage of the back plate 500 is not easy to cause, and as long as the back plate 500 is not damaged, the MEMS microphone can be used continuously without failure, thereby effectively improving the reliability of the MEMS microphone and prolonging the service life of the MEMS microphone.

In the embodiment of the present application, in the sound entering direction of the MEMS microphone (i.e. in the direction from top to bottom in fig. 1), the cover plate sound holes 710 and the back plate sound holes 540 are staggered and staggered. That is, in the axial direction of the cover plate sound hole 710, it is blocked by the back plate 500; in the axial direction of the backplate acoustic holes 540, they are blocked by the cover plate 700. Accordingly, foreign matters such as dust enter the third cavity 610 through the cover plate sound hole 710 and then are blocked by the back plate 500, so that the foreign matters are not easy to enter the second cavity 410 between the back plate 500 and the diaphragm 300 through the back plate sound hole 540, thereby effectively reducing the influence of the foreign matters such as dust on the performance of the microphone and effectively guaranteeing the acoustic performance of the microphone.

In the embodiment of the present application, the MEMS microphone further includes a connection hole 800 and a metal electrode 900, wherein the connection hole 800 is located outside the third cavity 610, and penetrates the cover plate 700 and the second insulating layer 530, so that the conductive layer 520 is partially exposed. The metal electrode 900 is located in the connection hole 800 and is electrically connected to the conductive layer 520, and the material of the metal electrode may be Cr or Au. The metal electrode 900 is disposed such that the conductive layer 520 may be connected to an external device such as an ASIC chip through the metal electrode 900, so that the external device may convert a capacitance change between the backplate 500 and the diaphragm 300 when the diaphragm 300 vibrates into an electrical signal output.

A method of manufacturing the MEMS microphone of fig. 1 is exemplarily described with reference to fig. 3 and fig. 4A to 4F, and includes the steps of:

s100: the first sacrificial layer 200, the diaphragm 300, the second sacrificial layer 400, and the backplate 500 are sequentially formed on the first surface of the substrate 100, and the plurality of backplate acoustic holes 540 are formed on the backplate 500. Wherein the backplate acoustic holes 540 expose a portion of the second sacrificial layer 400.

Specifically, referring to fig. 4A, a substrate 100 is provided first, and in this embodiment, the substrate 100 is made of silicon. A first sacrificial layer 200 is deposited on a first surface of the substrate 100 (i.e., the upper surface of the substrate 100 in fig. 4A). The first sacrificial layer 200 covers the upper surface of the substrate 100. After the deposition of the first sacrificial layer 200 is completed, the circumferential edge of the first sacrificial layer 200 may be etched to expose a portion of the substrate 100 outside the first sacrificial layer 200, thereby forming a patterned first sacrificial layer 200. In this embodiment, the material of the first sacrificial layer 200 is silicon oxide. Then, a diaphragm 300 is deposited on the first sacrificial layer 200, and the diaphragm 300 covers the upper surface of the first sacrificial layer 200. In the embodiment of the present application, the material of the diaphragm 300 is polysilicon. After the deposition of the diaphragm 300 is completed, the peripheral edge of the diaphragm 300 may be etched, so that a portion of the first sacrificial layer 200 is exposed outside the diaphragm 300, thereby forming the patterned diaphragm 300. Then, a second sacrificial layer 400 is deposited on the diaphragm 300, the second sacrificial layer 400 covering the upper surface of the diaphragm 300. In this embodiment, the second sacrificial layer 400 and the first sacrificial layer 200 are made of the same material and are all silicon oxide. After the second sacrificial layer 400 is deposited, a plurality of grooves 420 are etched on the second sacrificial layer 400, the depth of the grooves 420 is smaller than the thickness of the second sacrificial layer 400, and the grooves 420 are used for forming the blocking blocks 511. Thereafter, a back plate 500 is formed on the second sacrificial layer 400, and the back plate 500 includes a first insulating layer 510, a conductive layer 520, and a second insulating layer 530. Specifically, a first insulating layer 510 is deposited on the second sacrificial layer 400, the material of the first insulating layer 510 is silicon nitride, and the first insulating layer 510 covers the upper surface of the second sacrificial layer 400 and fills the recess 420. After the second sacrificial layer 400 is deposited, the upper surface of the first insulating layer 510 may be planarized so that the upper surface of the first insulating layer 510 becomes a plane. The specific manner of planarization may be Chemical mechanical planarization (Chemical-Mechanical Planarization, CMP) or other suitable planarization process, and one skilled in the art may choose as desired. Then, a conductive layer 520 is deposited on the upper surface of the first insulating layer 510, the conductive layer 520 is made of polysilicon, and the conductive layer 520 covers the first insulating layer 510. Then, a second insulating layer 530 is deposited on the upper surface of the conductive layer 520 and the exposed upper surfaces of the substrate 100 and the first sacrificial layer 200, the second insulating layer 530 is made of silicon nitride, and the second insulating layer 530 covers the upper surface of the conductive layer 520 and extends from the circumferential edges of the conductive layer 520 and the first insulating layer 510 to the substrate 100 and the first sacrificial layer 200. Then, the second insulating layer 530, the conductive layer 520 and the first insulating layer 510 are etched to form a plurality of back plate sound holes 540 penetrating the second insulating layer 530, the conductive layer 520 and the first insulating layer 510 and exposing a portion of the second sacrificial layer 400. The cross-section of the backplate acoustic hole 540 in its axial direction may be circular or other suitable shape. It should be noted that the specific deposition method mentioned in the present application may be Chemical Vapor Deposition (CVD), physical Vapor Deposition (PVD) or other suitable deposition methods known to those skilled in the art, and those skilled in the art may select a corresponding deposition method according to the deposited material. The specific etching mode mentioned in the application can be dry etching or wet etching, and a person skilled in the art can select a corresponding etching mode according to the material to be etched.

S110: a third sacrificial layer 600 is formed on the backplate 500. Wherein the third sacrificial layer 600 fills the backplate acoustic holes 540 and a portion of the backplate 500 is exposed at the circumferential edge of the third sacrificial layer 600.

Specifically, referring to fig. 4B, in step S110, first, a third sacrificial layer 600 is deposited on the upper surface of the second insulating layer 530 to cover the upper surface of the second insulating layer 530, and the third sacrificial layer 600 fills the backplate acoustic hole 540. Then, the upper surface of the third sacrificial layer 600 is planarized so that the upper surface of the third sacrificial layer 600 becomes a plane. The specific manner of planarization may be chemical mechanical planarization or other suitable planarization process, and one skilled in the art may choose as desired. Finally, the peripheral edge of the third sacrificial layer 600 is etched, so that a part of the second insulating layer 530 is exposed at the peripheral edge of the etched third sacrificial layer 600. In other embodiments, the peripheral edge of the third sacrificial layer 600 may be etched first, so that a part of the second insulating layer 530 is exposed outside the peripheral edge of the etched third sacrificial layer 600, and then the upper surface of the etched third sacrificial layer 600 may be planarized to be a plane.

S120: a cover plate 700 is formed on the third sacrificial layer 600 and on a portion of the back plate 500 exposed at the circumferential edge of the third sacrificial layer 600, and a plurality of cover plate sound holes 710 are formed in the cover plate 700 on the third sacrificial layer 600. Wherein the cover acoustic holes 710 expose a portion of the third sacrificial layer 600.

Specifically, referring to fig. 4C, in step S120, first, a cover plate 700 is deposited on the third sacrificial layer 600 and on a portion of the back plate 500 exposed at the circumferential edge of the third sacrificial layer 600, the cover plate 700 covering the upper surface and the side surfaces of the third sacrificial layer 600 over the second insulating layer 530. The cover plate 700 is made of silicon nitride in accordance with the second insulating layer 530. Then, the cover plate 700 on the third sacrificial layer 600 is etched to form a plurality of cover plate sound holes 710 penetrating the cover plate 700 and exposing a portion of the third sacrificial layer 600. The cover acoustic port 710 may have a circular or other suitable shape in cross-section along its axis. It should be noted that, when the cover plate 700 is etched to form the cover plate sound holes 710, the cover plate sound holes 710 and the back plate sound holes 540 need to be staggered in the sound entering direction of the MEMS microphone (i.e., in a direction perpendicular to the upper surface of the back plate 500 or perpendicular to the upper surface of the cover plate 700). In this embodiment, the cover plate 700 is etched to form the cover plate sound hole 710, and the cover plate 700 and the second insulating layer 530 outside the third sacrificial layer 600 are etched to form the connection hole 800, and the connection hole 800 exposes a portion of the conductive layer 520. The number of the connection holes 800 may be plural. Referring to fig. 4D, after the connection hole 800 is formed, a metal electrode 900 is deposited in the connection hole 800, the metal electrode 900 is made of Cr and Au, and the metal electrode 900 is electrically connected to the conductive layer 520.

S130: the back hole 110 is formed at the second surface of the substrate 100, and the first, second and third sacrificial layers 200, 400 and 600 are released to form the first cavity 210 in the first sacrificial layer 200, the second cavity 410 between the backplate 500 and the diaphragm 300, and the third cavity 610 between the cover plate 700 and the backplate 500. Wherein the second cavity 410 and the third cavity 610 communicate through the backplate acoustic hole 540.

Specifically, referring to fig. 4E, in step S130, the substrate 100 is etched first to form a back hole 110 on a second surface of the substrate 100 (i.e., a lower surface of the substrate 100 in fig. 4E), wherein the back hole 100 penetrates the substrate 100. The substrate 100 may be etched using a deep reactive ion etching process (Deep Reactive Ion Etching, abbreviated as DRIE, which is one of dry etching processes) or other suitable etching process to form the back holes 110. Thereafter, referring to fig. 4F, the first, second and third sacrificial layers 200, 400 and 600 are released by using an etching solution through the back hole 110 and the cover plate sound hole 710 to form the first cavity 210 in the middle of the first sacrificial layer 200, the second and third sacrificial layers 400 and 600 are removed to form the second cavity 410 between the back plate 500 and the diaphragm 300, and the third cavity 610 is formed between the cover plate 700 and the back plate 500. The second cavity 410 and the third cavity 610 communicate through the back plate sound hole 540, and the third cavity 610 communicates with the outside through the cover plate sound hole 710. Thus, the MEMS microphone is formed, and the cover plate sound holes 710 and the back plate sound holes 540 are staggered in the sound inlet direction of the MEMS microphone. In other embodiments, the second sacrificial layer 400 may not be completely removed when the second sacrificial layer 400 is released, but a second cavity 410 may be formed in the middle of the second sacrificial layer 400, leaving an edge portion of the second sacrificial layer 400 through which the back plate 500 is supported.

For the MEMS microphone shown in fig. 2, the manufacturing method thereof may include the steps of:

s200: the first sacrificial layer 200, the diaphragm 300, the second sacrificial layer 400', and the backplate 500' are sequentially formed on the first surface of the substrate 100, and the plurality of backplate acoustic holes 540 are formed on the backplate 500'. Wherein the backplate acoustic holes 540 expose the second sacrificial layer 400'.

Specifically, the substrate 100 is provided first, and the substrate 100 may be made of silicon. A first sacrificial layer 200 is deposited on a first surface of the substrate 100 (i.e., the upper surface of the substrate 100 in fig. 2). The first sacrificial layer 200 covers the upper surface of the substrate 100. The material of the first sacrificial layer 200 may be silicon oxide. Then, a diaphragm 300 is deposited on the first sacrificial layer 200, and the diaphragm 300 covers the upper surface of the first sacrificial layer 200. The material of the diaphragm 300 may be polysilicon. Then, a second sacrificial layer 400' is deposited on the diaphragm 300, the second sacrificial layer 400' covers the upper surface of the diaphragm 300, and the second sacrificial layer 400' and the first sacrificial layer 200 are made of the same material and are all made of silicon oxide. After the second sacrificial layer 400' is deposited, a plurality of grooves are etched on the second sacrificial layer 400', the depth of the grooves being smaller than the thickness of the second sacrificial layer 400', the grooves being used to form the blocking blocks 511. Thereafter, a back plate 500 'is formed on the second sacrificial layer 400', the back plate 500 'including a first insulating layer 510, a conductive layer 520, and a second insulating layer 530'. Specifically, a first insulating layer 510 is deposited on the second sacrificial layer 400', the material of the first insulating layer 510 is silicon nitride, and the first insulating layer 510 covers the upper surface of the second sacrificial layer 400' and fills the recess 420. After the second sacrificial layer 400' is deposited, the upper surface of the first insulating layer 510 may be planarized such that the upper surface of the first insulating layer 510 is planar. The specific manner of planarization may be chemical mechanical planarization or other suitable planarization process, and one skilled in the art may choose as desired. Then, a conductive layer 520 is deposited on the upper surface of the first insulating layer 510, the conductive layer 520 is made of polysilicon, and the conductive layer 520 covers the first insulating layer 510. Then, a second insulating layer 530' is deposited on the upper surface of the conductive layer 520, the material of the second insulating layer 530' is silicon nitride, and the second insulating layer 530' covers the upper surface of the conductive layer 520. Then, the second insulating layer 530', the conductive layer 520, and the first insulating layer 510 are etched to form a plurality of back plate sound holes 540 penetrating the second insulating layer 530', the conductive layer 520, and the first insulating layer 510 and exposing a portion of the second sacrificial layer 400'. The cross section of the back plate sound hole 540 in the axial direction thereof may be circular.

S210: a third sacrificial layer 600 is formed on the backplate 500'. Wherein the third sacrificial layer 600 fills the backplate acoustic holes 540 and a portion of the backplate 500' is exposed at the circumferential edge of the third sacrificial layer 600.

Step S210 is substantially the same as step S110, and the description thereof will not be repeated here.

S220: a cover plate 700 is formed on the third sacrificial layer 600 and on a portion of the back plate 500' exposed at the circumferential edge of the third sacrificial layer 600, and a plurality of cover plate sound holes 710 are formed in the cover plate 700 on the third sacrificial layer 600. Wherein the cover acoustic holes 710 expose a portion of the third sacrificial layer 600.

Step S220 is substantially the same as step S120, and the description thereof will not be repeated here.

S230: the back hole 110 is formed in the substrate 100, and the first sacrificial layer 200, the second sacrificial layer 400', and the third sacrificial layer 600 are released to form the first cavity 210 in the middle of the first sacrificial layer 200, the second cavity 410' between the backplate 500 'and the diaphragm 300, and the third cavity 610 between the cover plate 700 and the backplate 500'. Wherein the second cavity 410 'and the third cavity 610 communicate through the acoustic port of the backplate 500'.

Specifically, in step S230, the substrate 100 is etched first to form the back hole 110 on the second surface of the substrate 100 (i.e. the lower surface of the substrate 100 in fig. 2), and the back hole 100 penetrates through the substrate 100. The substrate 100 may be etched using a deep reactive ion etching process (Deep Reactive Ion Etching, abbreviated as DRIE, which is one of dry etching processes) or other suitable etching process to form the back holes 110. Thereafter, the first, second and third sacrificial layers 200, 400 'and 600 are released through the back hole 110 and the cover plate sound hole 710 using an etching solution to form the first cavity 210 in the middle of the first sacrificial layer 200, the second cavity 410' in the middle of the second sacrificial layer 400 '(i.e., the second cavity 410' between the back plate 500 'and the diaphragm 300), the third sacrificial layer 600 is removed, and the third cavity 610 is formed between the cover plate 700 and the back plate 500'. The backplate 500' is supported on the diaphragm 300 by the second sacrificial layer 400', the second cavity 410' and the third cavity 610 communicate through the backplate acoustic holes 540, and the third cavity 610 communicates with the outside through the backplate acoustic holes 710. Thus, the MEMS microphone is formed, and the cover plate sound holes 710 and the back plate sound holes 540 are staggered in the sound inlet direction of the MEMS microphone.

In the MEMS microphone formed by the above manufacturing method, the cover plate 700 is disposed on the side of the backplate 500 (backplate 500 ') away from the diaphragm 300, a cavity is disposed between the cover plate 700 and the backplate 500 (backplate 500 '), the cover plate 700 and the cavity can effectively protect the backplate 500 (backplate 500 '), when the MEMS microphone falls, the cover plate 700 can replace the backplate 500 (backplate 500 ') to contact with the ground, the risk of damage of the backplate 500 (backplate 500 ') when falling is effectively reduced, and the backplate 500 (backplate 500 ') is not easily damaged even if the cover plate 700 contacts with the ground and breaks, and as long as the backplate 500 (backplate 500 ') is not damaged, the MEMS microphone can be used continuously without failure, thereby effectively improving the reliability of the MEMS microphone and prolonging the service life of the MEMS microphone. The cover plate 700 and the second insulating layer 530 (second insulating layer 530') are made of silicon nitride with high hardness, and the same materials can be combined together better through a deposition mode, so that the whole MEMS microphone has higher strength, is not easy to damage when falling, and enhances the reliability of the MEMS microphone. In the sound entering direction of the MEMS microphone, the cover plate sound holes 710 and the back plate sound holes 540 are staggered, so that after the foreign matters such as dust enter the third cavity 610 through the cover plate sound holes 710, the foreign matters are blocked by the back plate 500 (the back plate 500 '), and are not easy to enter the second cavity 410 (the second cavity 410') between the back plate and the diaphragm 300 through the back plate sound holes 540, thereby effectively reducing the influence of the foreign matters such as dust on the performance of the microphone and effectively guaranteeing the acoustic performance of the microphone.

Although the illustrative embodiments have been described herein with reference to the accompanying drawings, it is to be understood that the above illustrative embodiments are merely illustrative and are not intended to limit the scope of the present application thereto. Various changes and modifications may be made therein by one of ordinary skill in the art without departing from the scope and spirit of the present application. All such changes and modifications are intended to be included within the scope of the present application as set forth in the appended claims.

In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the present application may be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

Similarly, it should be appreciated that in order to streamline the application and aid in understanding one or more of the various inventive aspects, various features of the application are sometimes grouped together in a single embodiment, figure, or description thereof in the description of exemplary embodiments of the application. However, the method of this application should not be construed to reflect the following intent: i.e., the claimed application requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this application.

It will be understood by those skilled in the art that all of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and all of the processes or units of any method or apparatus so disclosed, may be combined in any combination, except combinations where the features are mutually exclusive. Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise.

Furthermore, those skilled in the art will appreciate that while some embodiments described herein include some features but not others included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the present application and form different embodiments. For example, in the claims, any of the claimed embodiments may be used in any combination.

It should be noted that the above-mentioned embodiments illustrate rather than limit the application, and that those skilled in the art will be able to design alternative embodiments without departing from the scope of the appended claims.

Claims (10)

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

sequentially forming a first sacrificial layer, a vibrating diaphragm, a second sacrificial layer and a back plate on a first surface of a substrate, and forming a plurality of back plate sound holes on the back plate, wherein part of the second sacrificial layer is exposed out of the back plate sound holes;

forming a third sacrificial layer on the back plate, wherein the third sacrificial layer fills the back plate sound hole, and a part of the back plate is exposed at the circumferential edge of the third sacrificial layer;

forming a cover plate on the third sacrificial layer and part of the back plate exposed at the peripheral edge of the third sacrificial layer, and forming a plurality of cover plate sound holes in the cover plate on the third sacrificial layer, wherein part of the third sacrificial layer is exposed by the cover plate sound holes;

and forming a back hole on the second surface of the substrate, releasing the first sacrificial layer, the second sacrificial layer and the third sacrificial layer to form a first cavity in the first sacrificial layer, a second cavity between the back plate and the vibrating diaphragm and a third cavity between the cover plate and the back plate, wherein the second cavity and the third cavity are communicated through the back plate sound hole.

2. The method according to claim 1, wherein,

and in the sound inlet direction of the MEMS microphone, the sound holes of the back plate and the sound holes of the cover plate are staggered.

3. The method according to claim 1, wherein,

the backboard comprises a first insulating layer, a conductive layer and a second insulating layer;

forming a back plate on the second sacrificial layer, and forming a back plate sound hole on the back plate, wherein part of the second sacrificial layer is exposed out of the back plate sound hole, and the method comprises the following steps:

forming the first insulating layer on the second sacrificial layer;

forming the conductive layer on the first insulating layer;

forming the second insulating layer on the conductive layer;

etching the second insulating layer, the conductive layer and the first insulating layer to form a back plate sound hole penetrating through the second insulating layer, the conductive layer and the first insulating layer, wherein a part of the second sacrificial layer is exposed out of the back plate sound hole.

4. The method according to claim 3, wherein,

forming a back hole on the second surface of the substrate to release the first sacrificial layer, the second sacrificial layer and the third sacrificial layer, and further comprising:

forming a connection hole, wherein the connection hole penetrates through the cover plate and the second insulating layer outside the third sacrificial layer, and exposes a part of the conductive layer;

and forming a metal electrode in the connection hole.

5. The method according to claim 3, wherein,

the substrate is made of silicon;

the materials of the first sacrificial layer, the second sacrificial layer and the third sacrificial layer all comprise silicon oxide;

the material of the vibrating diaphragm comprises polysilicon;

the materials of the first insulating layer and the second insulating layer comprise silicon nitride;

the material of the conductive layer comprises polysilicon;

the cover plate is made of silicon nitride.

6. A MEMS microphone, comprising:

a substrate, wherein a second surface of the substrate is provided with a back hole;

a first sacrificial layer on the first surface of the substrate, the first sacrificial layer having a first cavity therein;

a diaphragm located on the first sacrificial layer;

the backboard is positioned at one side of the vibrating diaphragm away from the first sacrificial layer, a second cavity is formed between the backboard and the vibrating diaphragm, and a plurality of backboard sound holes are formed in the backboard;

the cover plate is positioned on one side of the back plate away from the vibrating diaphragm, a third cavity is formed between the cover plate and the back plate, and a plurality of cover plate sound holes are formed in the cover plate.

7. The MEMS microphone, as recited in claim 6,

and in the sound inlet direction of the MEMS microphone, the sound holes of the back plate and the sound holes of the cover plate are staggered.

8. The MEMS microphone, as recited in claim 6,

the backboard comprises a first insulating layer, a conductive layer and a second insulating layer;

the first insulating layer is located the backplate is towards one side of vibrating diaphragm, the conducting layer is located first insulating layer is kept away from one side of vibrating diaphragm, the second insulating layer is located the conducting layer is kept away from one side of first insulating layer, the apron is located the second insulating layer is kept away from one side of conducting layer, backplate sound hole runs through first insulating layer conducting layer and second insulating layer.

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

the MEMS microphone further comprises a connecting hole and a metal electrode;

the connecting hole penetrates through the cover plate and the second insulating layer outside the third cavity, and part of the conducting layer is exposed;

the metal electrode is positioned in the connecting hole and is connected with the conductive layer in a conductive way.

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

the substrate is made of silicon;

the material of the first sacrificial layer comprises silicon oxide;

the material of the vibrating diaphragm comprises polysilicon;

the materials of the first insulating layer and the second insulating layer comprise silicon nitride;

the material of the conductive layer comprises polysilicon;

the cover plate is made of silicon nitride.

Images