CN212544055U - MEMS microphone - Google Patents

Abstract

The utility model provides a MEMS microphone, the support wall body on the substrate encloses into a cavity, and the vibrating diaphragm hangs in the cavity and the edge extends to the internal realization of support wall and fixes. The release hole array on the back plate structure comprises a plurality of release holes which penetrate through the back plate structure and are communicated with the cavity, in the process of forming the support wall body through the release hole array release sacrificial layer, the outline of the inner wall of the support wall body is mainly related to the outermost release holes of the release hole array, and the outermost release holes are configured into first release holes and second release holes which are arranged at intervals. Because the aperture of the first release hole is larger than that of the second release hole, the inner wall of the support wall body can be corroded into a wave shape by the first release hole, and a sharp corner in the wave shape can be cut off by the second release hole, so that the formation of the sharp corner is inhibited, the contour of the inner wall of the support wall body is smooth, the vibrating membrane is prevented from falling off due to the fact that the sharp corner punctures the vibrating membrane, and the service life and the reliability of the device are improved.

Description

MEMS microphone

Technical Field

The utility model relates to a microphone technical field especially relates to a MEMS microphone.

Background

The MEMS microphone is a MEMS (Micro-Electro-Mechanical System) device manufactured by using a Micro-machining process. Due to the advantages of small volume, high sensitivity and good compatibility with the existing semiconductor technology, the MEMS microphone is more and more widely applied to mobile terminals such as mobile phones.

The structure of the MEMS microphone is provided with a vibrating membrane, a back plate structure and a supporting wall body, the supporting wall body is enclosed to form a cavity B ', the back plate structure is located on the supporting wall body and covers the cavity B', the vibrating membrane is suspended in the cavity B ', and the edge of the vibrating membrane extends into the supporting wall body 200' to be fixed. Fig. 1 is a schematic structural diagram of a conventional support wall 200', as shown in fig. 1, in a process of manufacturing a MEMS microphone, the support wall 200' is formed by releasing a sacrificial layer using a release hole array on a backplate structure (an etchant corrodes a portion of the sacrificial layer using the release hole array as a channel, and the remaining sacrificial layer forms a support wall 200', and the corroded portion forms a cavity B'), so that the contour of an inner wall of the support wall 200 'is not smooth enough, but has a wave shape with a sharp corner Q in the wave shape, and since a diaphragm needs to vibrate up and down in the cavity B', and an edge of the diaphragm is fixed by the support wall 200', the sharp corner Q easily pierces the diaphragm during vibration of the diaphragm, thereby causing the diaphragm to break or even fall from the support wall 200', and further causing device damage.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a MEMS microphone can level and smooth support the profile of wall body inner wall, suppresses the closed angle to improve the reliability and the life-span of device.

In order to achieve the above object, the present invention provides a MEMS microphone, including:

a substrate;

the supporting wall body is arranged on the substrate and encloses a cavity;

the vibrating membrane is suspended in the cavity, and the edge of the vibrating membrane extends into the supporting wall body to be fixed;

the back plate structure is positioned on the supporting wall body and covers the cavity; and the number of the first and second groups,

and the release hole array comprises a plurality of release holes which penetrate through the backboard structure and are communicated with the cavity, the release holes positioned at the outermost circle of the release hole array comprise first release holes and second release holes which are arranged at intervals, and the aperture of the first release holes is larger than that of the second release holes.

Optionally, the center of the cavity coincides with the center of the array of release holes.

Optionally, the first release hole is located on a first virtual circumference with the center of the release hole array as a center, the second release hole is located on a second virtual circumference with the center of the release hole array as a center, and the first virtual circumference and the second virtual circumference may or may not coincide.

Optionally, the distance between adjacent first release holes is equal, and/or the distance between adjacent second release holes is equal.

Optionally, the release holes inside the outermost ring of release holes are third release holes, and the third release holes are arranged in a rectangular array, a honeycomb structure array or a concentric rotation array.

Optionally, the backplane structure has a release area corresponding to the cavity, and the release hole array is located in the release area.

Optionally, the pore size of the release pores is 1 micron to 20 microns.

Optionally, the release hole is one or more of a circular hole, a cross-flower hole and a polygonal hole.

Optionally, the support wall includes two stacked support layers, and an edge of the diaphragm is clamped between the two support layers.

Optionally, an acoustic cavity is formed in the substrate, and the acoustic cavity penetrates through the substrate and is communicated with the cavity.

Optionally, the backplate structure includes a first protection layer, a second protection layer, and a backplate electrode located between the first protection layer and the second protection layer, and the first protection layer is closer to the diaphragm than the second protection layer.

Optionally, the first protection layer has a plurality of protrusions facing the cavity.

Optionally, the method further includes:

the first contact point is positioned on the same layer as the vibration film and is electrically connected with the vibration film;

the second contact point is positioned on the same layer as the back plate electrode and is electrically connected with the back plate electrode;

the first bonding pad is electrically connected with the first contact point through a conductive channel penetrating through the second protective layer, the first protective layer and at least part of the supporting wall;

and the second bonding pad is electrically connected with the second contact point through a conductive channel penetrating through the second protective layer.

The utility model provides an among the MEMS microphone, the support wall body on the substrate encloses into a cavity, and the vibrating diaphragm hangs in the cavity and the edge extends to and realizes fixedly in the support wall body. The release hole array on the back plate structure comprises a plurality of release holes which penetrate through the back plate structure and are communicated with the cavity, in the process of forming the support wall body through the release hole array release sacrificial layer, the outline of the inner wall of the support wall body is mainly related to the outermost release holes of the release hole array, and the outermost release holes are configured into first release holes and second release holes which are arranged at intervals. Because the aperture of the first release hole is larger than that of the second release hole, the inner wall of the support wall body can be corroded into a wave shape by the first release hole, and a sharp corner in the wave shape can be cut off by the second release hole, so that the formation of the sharp corner is inhibited, the contour of the inner wall of the support wall body is smooth, the vibrating membrane is prevented from falling off due to the fact that the sharp corner punctures the vibrating membrane, and the service life and the reliability of the device are improved.

Drawings

Fig. 1 is a schematic structural diagram of a conventional supporting wall provided in an embodiment of the present invention;

fig. 2 to 14b are schematic structural diagrams corresponding to respective steps of a method for manufacturing an MEMS microphone according to the present embodiment, where fig. 14a is a schematic structural diagram of the MEMS microphone, and fig. 14b is a top view of fig. 14 a;

wherein the reference numerals are:

200' -supporting a wall; q-sharp angle; b' -a cavity;

100-a substrate; 200-supporting a wall body; 210-a first support layer; 220-a second support layer; 310-a first groove; 320-a second groove; 330-third groove; 340-a fourth groove; 350-fifth groove; 410-a diaphragm; 420-first contact point; 510-a first protective layer; 521-a back plate electrode; 522 — second contact point; 530-a second protective layer; 610-a first pad; 620-second pad; 700-array of release wells; 710-a first release aperture; 720-a second release hole; 730-a third release aperture; 800-an acoustic chamber;

b-a cavity; r-fold structure; an S-bump.

Detailed Description

The following description of the embodiments of the present invention will be described in more detail with reference to the drawings. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the drawings are in simplified form and are not to precise scale, and are provided for convenience and clarity in order to facilitate the description of the embodiments of the present invention.

Fig. 14a and 14b are schematic structural views of the MEMS microphone of the present embodiment. Referring to fig. 14a and 14b, the MEMS microphone includes a substrate 100, a support wall 200, a diaphragm 410, and a backplate structure. The substrate 100 is used for supporting a device, and the supporting wall 200 is located between the substrate 100 and the backplate structure to form a sandwich structure. The supporting wall 200 encloses a cavity B, the diaphragm 410 is suspended in the cavity B, the edge of the diaphragm extends into the supporting wall 200 for fixing, and the upper and lower surfaces of the diaphragm 410 are respectively spaced from the backplate structure and the substrate 100 by a certain distance, so that the diaphragm 410 can vibrate up and down in the cavity B.

Referring to fig. 14a, in the present embodiment, the substrate 100 has an acoustic cavity 800, the acoustic cavity 800 penetrates through the substrate 100 and is communicated with the cavity B, and the cross-sectional shape of the acoustic cavity 800 along the thickness direction may be an inverted trapezoid, a square or a hexagon.

Further, the support wall 200 is ring-shaped to enclose the cavity B. In this embodiment, the support wall 200 includes two support layers stacked, and the edge of the diaphragm 410 is fixed by being clamped between the two support layers. In this way, the height of the cavity B can be controlled by controlling the thickness of the support wall 200, and the distance between the diaphragm 410 and the substrate 100 and between the diaphragm and the backplate structure can be adjusted by adjusting the thickness ratio of the two support films constituting the support wall 200. Typically, the diaphragm 410 and the backplate structure are spaced apart by 1 to 5 microns.

In this embodiment, the widths of the two supporting layers in the direction perpendicular to the thickness direction are not equal, so that the sizes of the upper part and the lower part of the cavity B are not equal, and at this time, the cross section of the cavity B in the thickness direction is approximately T-shaped; of course, the lateral widths of the two supporting layers may also be equal, so that the cavity B is substantially cylindrical.

As an alternative embodiment, the diaphragm 410 includes a middle portion and a peripheral portion surrounding the middle portion, the edge of the peripheral portion extending into the support wall 200, the middle portion including at least one through hole (not shown) for stress relief and adjustment of the microphone frequency response curve. The diaphragm 410 further includes a wrinkle structure R for connecting a middle portion and a peripheral portion, the wrinkle structure R being concentric annular wrinkle portions on the diaphragm 410, the middle portion of the diaphragm 410 and the wrinkle structure R being movable regions. Alternatively, the corrugation structure R may be a spiral corrugation, and the curvature radius of the thread of the corrugation structure R is not changed or is changed with the position, for example, the curvature radius of each spiral thread is the same. The corrugated structure R can be selected according to the requirements of the actual application.

Compared with the diaphragm 410 with a flat surface, the diaphragm 410 with the corrugated structure R can improve the elastic characteristics of the diaphragm, control the movable area, improve the elastic coefficient of the diaphragm structure, and meet the requirement of the performance design of the MEMS microphone. Further, the corrugated structure R may extend to the peripheral portion of the diaphragm 410, effectively releasing the stress of the diaphragm 410, and improving the sensitivity of the MEMS microphone.

Further, because the outer contour of the fold structure R is located within the range of the acoustic cavity 800, the problem of reliability reduction of the MEMS microphone due to process fluctuation in mass production can be avoided, and the overall performance of the product is improved.

In the present embodiment, the thickness of the diaphragm 410 is, for example, 0.3 to 1 μm.

Further, the back plate structure includes a first protection layer 510, a back plate electrode 521 and a second protection layer 530, the first protection layer 510 faces the cavity B, and the back plate electrode 521 is located between the first protection layer 510 and the second protection layer 530 to form a sandwich structure. The first protection layer 510 and the second protection layer 530 are each composed of any one of a Boron Nitride (BN) layer, a silicon nitride (SIN) layer, a silicon boron nitride (SIBN) layer, a borophosphosilicate glass (BPSG) layer, and a phosphosilicate glass (PSG), and in this embodiment, the first protection layer 510 and the second protection layer 530 are each a boron nitride layer.

In this embodiment, the thickness of the first protection layer 510 is, for example, 0.08 to 0.25 micrometers; the thickness of the second protective layer 530 is, for example, 0.1 to 1.5 micrometers; the back electrode plate electrode 521 has a thickness of, for example, 0.3 to 1 μm.

In this embodiment, the cross-sectional area of the diaphragm 410 is larger than the maximum cross-sectional area of the acoustic cavity 800 in the direction perpendicular to the thickness direction, and the cross-sectional area of the backplate electrode 521 is smaller than or equal to the minimum cross-sectional area of the acoustic cavity 800, and more preferably, the cross-sectional area of the backplate electrode 521 is smaller than the minimum cross-sectional area of the acoustic cavity 800. It should be noted that, when the cross-sectional shape of the acoustic cavity 800 in the thickness direction is a square shape, the cross-sectional areas of the acoustic cavities 800 are all the same, and the only cross-sectional area is the minimum cross-sectional area; when the cross-sectional shape of the acoustic cavity 800 in the thickness direction is an inverted trapezoid, a trapezoid, or a hexagon, the cross-sectional area of the acoustic cavity 800 at the upper surface or the lower surface of the substrate 100 is the smallest. In some embodiments, the smallest cross-sectional area of the acoustic cavity 800 has a radius of 250 microns to 600 microns.

In this embodiment, the first protection layer 510 has a protrusion S facing the diaphragm 410, so as to prevent the adhesion between the backplate electrode 521 and the diaphragm 410 when the diaphragm 410 deforms by more than 33% under a large impact or excitation during the use of the MEMS microphone (which may greatly prolong the duration of the current state of the MEMS microphone, causing intermittent or even permanent failure of the MEMS microphone). Alternatively, the protrusions S may be polygonal pyramids, polygonal prisms, cones, or cylinders; the diameter of the projections S is, for example, 0.5 to 1.5 micrometers, and the height is, for example, 0.5 to 1.5 micrometers.

It should be appreciated that the second protective layer 530 may act as a mechanical support layer for the back plate electrode 521 to provide rigidity such that the back plate electrode 521 maintains a non-deformed state in an operating state.

Alternatively, the back plate electrode 521 is formed above the movable region of the diaphragm 410, and the back plate electrode 521 and the diaphragm 410 form two plates of a capacitor. The area of the back plate electrode 521 is smaller than or equal to the area of the movable region of the diaphragm 410, in this embodiment, the area of the back plate electrode 521 is smaller than the area of the movable region of the diaphragm 410, for example, the area of the back plate electrode 521 is 70% to 100% of the movable region of the diaphragm 410, and since the area of the back plate electrode 521 is smaller than or equal to the area of the movable region of the diaphragm 410, an ineffective capacitance component is removed from a detection signal, so that the sensitivity of the detection signal is only related to an effective capacitance component, thereby improving the sensitivity of the MEMS microphone. The movable region of the diaphragm 410 includes a middle portion and a connection portion.

Optionally, the shape of the back electrode plate electrode 521 may be a circular shape, a concentric circular ring shape, a circular shape with a radial strip beam at the edge, a triangular shape, a square shape, or other geometric shapes, which is not limited by the present invention. Further, the back electrode plate electrode 521 may also have a plurality of through holes, and the through holes may also be formed in a circular shape, a polygonal shape, or the like.

In this embodiment, the diaphragm 410 and the back plate electrode 521 are both made of doped polysilicon, so that the diaphragm 410 and the back plate electrode 521 have conductivity. In this embodiment, the MEMS microphone further includes a first contact point 420 disposed on the same layer as the diaphragm 410 and electrically connected thereto, and a second contact point 522 disposed on the same layer as the back electrode plate electrode 521 and electrically connected thereto, wherein a first pad 610 and a second pad 620 are further formed on the second protective layer 530, and the first pad 610 and the second pad 620 are electrically connected to the first contact point 420 and the second contact point 522 through conductive paths, respectively.

It should be understood that the diaphragm 410 and the back plate electrode 521 can also be made of metal materials such as aluminum, copper, gold, titanium, nickel, tungsten, and alloys thereof, which is not limited by the present invention.

In the present embodiment, the first pad 610 and the second pad 620 are made of a conductive material, such as any one of aluminum, gold, copper, nickel, titanium, chromium, or an alloy thereof, and have a thickness of, for example, 1 to 2 micrometers.

It should be understood that the number of the first pads 610 and the second pads 620 may be one, two or more, and the present invention is not limited thereto.

With continued reference to fig. 14a and 14B, the back plate structure has a release area corresponding to the cavity B, the area outside the release area is disposed on the support wall 200, a release hole array 700 is disposed in the release area, the release hole array 700 includes a plurality of release holes penetrating through the back plate structure and communicating with the cavity B, the release hole array 700 has an outermost ring of release holes, and as can be seen from fig. 14B, the outermost ring of release holes is the release holes farthest from the center of the release hole array 700. The release holes in the release hole array 700 serve not only as a supply channel of an etchant in the manufacturing process but also as sound holes in the finally formed MEMS microphone to reduce acoustic resistance.

Further, the release holes, such as one or more of circular holes, cross-flower holes, and polygonal holes, may be identical or different in shape, as viewed from the surface of the second protective layer 530. In this embodiment, the release holes are all circular holes.

In this embodiment, the pore size of the release hole is 1 to 20 micrometers, for example, 5 micrometers, 10 micrometers, or 15 micrometers.

Referring to fig. 14a and 14b, in the present embodiment, the outermost release holes include a plurality of first release holes 710 and a plurality of second release holes 720, the release holes in the outermost release holes are all third release holes 730, the first release holes 710 and the second release holes 720 are circumferentially spaced, and the third release holes 730 are arranged in a honeycomb array, a rectangular array, a concentric rotation array, or the like. The aperture of the first release hole 710 is larger than that of the second release hole 720, and the aperture of the third release hole 730 is not particularly required in this embodiment.

In the process of releasing the sacrificial layer to form the support wall 200 through the release hole array 700, the third release holes 730 are mainly used to remove the sacrificial layer in a large area to form the cavity B, and the outermost release holes affect the profile of the side surface of the cavity B, that is, the profile of the inner wall of the support wall 200 formed by the remaining sacrificial layers. In this embodiment, the outermost circles of release holes are configured as the first release holes 710 and the second release holes 720 which are arranged at intervals, and the aperture of the first release holes 710 is larger than the aperture of the second release holes 720, so that the inner wall of the support wall 200 is corroded into a wave shape by the first release holes 710, and the second release holes 720 can cut off sharp corners in the wave shape, thereby inhibiting the formation of the sharp corners, smoothing the contour of the inner wall of the support wall 200, preventing the sharp corners from piercing the vibration film 410 and causing the vibration film 410 to fall off, and improving the service life and reliability of the device.

Further, since the cavities B are formed by releasing the sacrificial layer through the release hole array 700, and the third release holes 730 are generally regularly arranged, the centers of the cavities B coincide with the center of the release hole array 700, so that the structure of the device is uniform and stable.

Referring to fig. 14b, in the present embodiment, the first release holes 710 are located on a first virtual circumference with the center of the release hole array 700 as the center, and the second release holes 720 are located on a second virtual circumference with the center of the release hole array 700 as the center, wherein the first virtual circumference and the second virtual circumference are coincident. That is, the first and second release holes 710 and 720 are all equidistant from the center of the release hole array 700.

Of course, the degree of "chipping" off sharp corners in the undulations may be adjusted by adjusting the position of the second release holes 720, so the first imaginary circle and the second imaginary circle may not actually coincide, and in this case, the first release holes 710 and the second release holes 720 are not equidistant from the center of the release hole array 700.

Referring to fig. 14b, in the present embodiment, the first release holes 710 are uniformly distributed on the first virtual circumference, so that the distances between the adjacent first release holes 710 are equal; and, the second release holes 720 are uniformly distributed on the second virtual circumference such that the distances between the adjacent second release holes 720 are equal. In this way, the arrangement of the first release holes 710 and the second release holes 720 in the outermost circle of the release hole array 700 is also regular, so that the contour of the inner wall of the support wall 200 is uniform.

With continuing reference to fig. 14a and 14b, it should be understood that, since the support wall 200 is formed by two support layers, the sacrificial layer forming the support wall 200 is also a two-layer structure, and during the process of releasing the sacrificial layer, for increasing efficiency, one layer of the sacrificial layer facing the backplate structure is released through the release hole array 700, and one layer facing the substrate 100 is released through the acoustic cavity 800, so that the release hole array 700 actually improves the profile of a portion of the inner wall of the support wall 200.

Fig. 2 to 14b are schematic structural diagrams corresponding to corresponding steps of the method for manufacturing the MEMS microphone provided in this embodiment. Next, a method of manufacturing the MEMS microphone will be described in detail with reference to fig. 2 to 14 b.

Referring to fig. 2, first, a substrate 100 is provided, for example, the substrate 100 is a silicon wafer with a <100> crystal orientation, and the doping type of the substrate 100 is N-type, but it should be understood that the invention is not limited to the crystal orientation and the doping type of the substrate 100.

Next, a first support layer 210 is formed on the substrate 100, and the first support layer 210 is, for example, a silicon oxide layer. The method for forming the first support layer 210 is, for example: a silicon oxide layer is formed on the substrate 100 as the first support layer 210 by a thermal oxidation or Chemical Vapor Deposition (CVD) method. In this embodiment, a portion of the first support layer 210 is used as a sacrificial layer to form a portion of the cavity, and the thickness of the first support layer 210 is, for example, 0.5 to 2 micrometers.

Referring to fig. 3, a first groove 310 is formed on the surface of the first supporting layer 210, and the first groove 310 is formed by a plurality of sub-grooves arranged at intervals. In this embodiment, a resist layer is formed on the surface of the first support layer 210, and a pattern including an opening is formed in the resist layer by a photolithography process. The exposed portion of the first support layer 210 is removed using a selective etchant with the resist layer as a mask, thereby forming the first groove 310. By controlling the etching time, the etching may be stopped after reaching a predetermined depth of the first support layer 210, and after the etching, the resist layer may be removed by ashing or dissolution in a solvent.

The first groove 310 is opened at a surface of the first support layer 210 and extends downward. The shape of the first groove 310 is a concentric ring shape, for example, including nested 1 to 6 circular ring shapes, when viewed from the surface of the first support layer 210. In this embodiment, when viewed from a cross section of the first support layer 210, the first groove 310 has a square shape; as an alternative embodiment, the first groove 310 has a trapezoidal or V-shape with a bottom surface size smaller than an opening surface size when viewed from a cross section of the first support layer 210. The depth of the first groove 310 is, for example, 0.5 to 0.8 micrometers.

Preferably, an opening surface of the first groove 310 and a surface of the first support layer 210 form a smooth transition curved surface. To this end, an additional deposition step may be used to form a conformal capping layer, such as a thin oxide layer, to improve the topography of the first recess 310 and to obtain a rounded transition curve. The thickness of the cover layer is, for example, 0.1 to 2 micrometers.

Referring to fig. 4, a diaphragm 410 and a first contact 420 are formed on the first supporting layer 210, and the diaphragm 410 and the first contact 420 are located on the same layer and are made of doped polysilicon. The diaphragm 410 and the first contact point 420 are formed, for example, by: depositing polysilicon on the first support layer 210 by Low Pressure Chemical Vapor Deposition (LPCVD), for example, at a temperature of 570 to 630 degrees celsius; the polysilicon layer is patterned using photolithography and etching steps to pattern the diaphragm 410 and the first contact 420 in different regions of the polysilicon layer, respectively.

The diaphragm 410 is conformally formed on the first support layer 210, so that the diaphragm 410 has a second groove 320 corresponding to the first groove 310, and the second groove 320 is used to define a middle portion and a peripheral portion of the diaphragm 410. The portion of the diaphragm 410 corresponding to the first groove 310 and the second groove 320 corresponds to a corrugated structure R that continuously and conformally covers the first support layer 210 with a middle portion and a peripheral portion. The corrugation structure R is also concentric ring-shaped corrugations, in accordance with the shapes of the first and second grooves 310 and 320.

Referring to fig. 5 and 6, a second supporting layer 220 is formed on the vibrating membrane 410, and a plurality of third recesses 330 are formed on the upper surface of the second supporting layer 220, in this embodiment, the second supporting layer 220 is a silicon oxide layer. The method of forming the second support layer 220 is, for example: a silicon oxide layer is formed on the diaphragm 410 as the second support layer 220 by a Low Pressure Chemical Vapor Deposition (LPCVD) or Plasma Enhanced Chemical Vapor Deposition (PECVD) method. After the second support layer 220 is formed, the upper surface of the second support layer 220 is planarized, for example, using a chemical mechanical planarization process.

A portion of the second support layer 220 will act as a sacrificial layer for forming a portion of the cavity and also define the spacing between the diaphragm 410 and the backplate structure by the thickness of the second support layer 220. The thickness of the second support layer 220 is chosen according to the electrical and acoustic properties of the MEMS microphone, for example 2 to 4 microns.

Next, a resist layer is formed on the surface of the second support layer 220, and a pattern including an opening is formed in the resist layer by a photolithography process. The exposed portions of the second support layer 220 are removed using a selective etchant using the resist layer as a mask, thereby forming a plurality of third grooves 330. By controlling the etching time, the etching may be stopped at a predetermined depth to the second support layer 220. After etching, the resist layer may be removed by ashing or dissolution in a solvent.

The third groove 330 is opened at the surface of the second support layer 220 and extends downward. The third grooves 330 may have a polygonal shape, such as a circular hole, a square hole, or a triangular hole, when viewed from the surface of the second support layer 220. The third groove 330 has a rectangular shape or a trapezoidal or V-shaped shape having a bottom surface size smaller than an opening surface size, when viewed from a cross-section of the second support layer 220, for defining a protrusion for preventing adhesion of the back plate structure formed in a subsequent step.

Referring to fig. 6 and 7, a first protection layer 510 is formed on the second supporting layer 220. The method for forming the first protection layer 510 is, for example: a boron nitride layer is formed on the second support layer 220 by a plasma enhanced chemical vapor deposition method.

The first protective layer 510 fills the third groove 330, thereby forming a protrusion S. The shape of the protrusion S corresponds to the shape of the third groove 330.

Referring to fig. 8, a back plate electrode 521 and a second contact 522 connected to the back plate electrode 521 are formed on the first protection layer 510, in this embodiment, the back plate electrode 521 and the second contact 522 are located on the same layer and are both made of doped polysilicon. The methods for forming the back electrode plate electrode 521 and the second contact point 522 are, for example: a doped polysilicon layer is formed on a portion of the surface of the first protective layer 510 using Low Pressure Chemical Vapor Deposition (LPCVD). The polysilicon layer is then patterned using photolithography and etching steps to pattern the backplane electrode 521 and to form a second contact 522 to the backplane electrode 521.

With reference to fig. 8, after the back electrode plate 521 is formed, the first passivation layer 510 and the second supporting layer 220 above the first contact 420 are etched by a conventional semiconductor etching process to form a fourth recess 340, wherein the surface of the first contact 420 is not exposed by the fourth recess 340.

Referring to fig. 9, a second passivation layer 530 is formed on the back electrode plate 521. The method for forming the second protection layer 530 is, for example: a conformal boron nitride layer is formed on the back plate electrode 521 by Plasma Enhanced Chemical Vapor Deposition (PECVD) method.

The first protective layer 510, the back plate electrode 521 and the second protective layer 530 form a back plate structure.

Further, since the back plate electrode 521 is patterned, a portion of the second protection layer 530 is formed on the surfaces of the back plate electrode 521 and the second contact 522, and another portion is formed on the surface of the first protection layer 510, and the fourth groove 340 is also filled with a portion.

Referring to fig. 10, the second passivation layer 530 in the fourth groove 340 is removed, the second supporting layer 220 at the bottom of the fourth groove 340 is etched to expose the first contact 420, and a fifth groove 350 exposing the second contact 522 is formed. It is understood that the second supporting layer 220 at the bottom of the fourth groove 340 can protect the first contact point 420 during this step, and prevent the first contact point 420 from being damaged by over-etching.

Referring to fig. 10 and 11, a conductive material is filled in the fourth groove 340 and the fifth groove 350 to form a conductive path, and then a first pad 610 and a second pad 620 are formed on the conductive path formed by the fourth groove 340 and the fifth groove 350, respectively, to serve as lead layers of two electrodes of the MEMS microphone. The first bonding pad 610, the second bonding pad 620 and the conductive channel are formed by the following steps: forming a metal layer on the surface of the second protection layer 530 by sputtering or evaporation, wherein the metal layer fills the fourth groove 340 and the fifth groove 350 and covers the surface of the second protection layer 530; and forming a resist layer on the surface of the metal layer, and forming a pattern containing an opening in the resist layer by adopting a photoetching process. Removing the exposed portion of the metal layer with a selective etchant using the resist layer as a mask, the etching using the second protection layer 530 as a stop layer due to the selectivity of the etchant; after etching, the resist layer may be removed by ashing or dissolution in a solvent.

Referring to fig. 12, a plurality of release holes penetrating through the second passivation layer 530, the back plate electrode 521 and the first passivation layer 510 are formed, and the plurality of release holes form a release hole array 700. The method of forming the release hole is, for example: forming a resist layer on the surface of the second protection layer 530, and forming a pattern including an opening in the resist layer by using a photolithography process; the release holes are formed by removing the exposed portions of each of the second protective layer 530, the back plate electrode 521, and the first protective layer 510 with a selective etchant using the resist layer as a mask. The second support layer 220 acts as a stop layer due to the selectivity of the etchant; after etching, the resist layer may be removed by ashing or dissolution in a solvent.

As an alternative embodiment, the release holes may also be formed using a special deep trench etcher.

In this embodiment, the array of release holes 700 includes a first release hole 710, a second release hole 720 and a third release hole 730. The first release holes 710 and the second release holes 720 are positioned at the outermost circle of the release hole array 700 and are arranged at intervals, and the aperture of the first release holes 710 is larger than that of the second release holes 720; the third release holes 730 are located in the outermost circle of release holes and distributed in an array.

Referring to fig. 13, an acoustic cavity 800 is formed in the substrate 100. In this embodiment, the substrate 100 is thinned to a design value, for example, 350 to 450 microns, preferably 400 microns, by a chemical mechanical planarization process. Then, a resist layer is formed on the lower surface of the substrate 100, and a pattern including an opening is formed in the resist layer using a photolithography process. The acoustic chamber 800 is formed by removing the exposed portions of the substrate 100 with a selective etchant using a resist layer as a mask. In this embodiment, the cross-sectional shape of the acoustic cavity 800 along the thickness direction is an inverted trapezoid opening, and optionally, the cross-sectional shape of the acoustic cavity 800 along the thickness direction may also be a square or hexagonal opening. The first support layer 210 acts as a stop layer due to the selectivity of the etchant. After etching, the resist layer may be removed by ashing or dissolution in a solvent.

Alternatively, the acoustic cavity 800 is formed using a conventional Bosch process in MEMS technology and a special deep trench etcher.

Referring to fig. 13 and 14a, a portion of the first support layer 210 is removed through the acoustic cavity 800, and a portion of the second support layer 220 is removed through the release hole array 700 to release the diaphragm 410. In this embodiment, hydrofluoric acid is used as an etchant, and the acoustic cavity 800 and the release hole array 700 are used as an access channel of the etchant. The first protective layer 510 and the second protective layer 530 each serve as a protective film for the back plate electrode 521, so that the back plate electrode 521 is not etched in this etching step.

The hydrofluoric acid is in contact with the first and second support layers 210 and 220 by using the release hole arrays 700 and the acoustic cavities 800 as channels by vapor fumigation of hydrofluoric acid or wet etching of hydrofluoric acid, thereby removing a portion of each of the first and second support layers 210 and 220 to re-expose a portion of the upper and lower surfaces of the diaphragm 410, thereby releasing the diaphragm 410.

After removing a portion of the first and second supporting layers 210 and 220, the remaining first and second supporting layers 210 and 220 constitute a supporting wall 200. The support wall 200 encloses a cavity B in which the diaphragm 410 is suspended after being released and divides the cavity B into upper and lower portions, the cavity B, the release holes in the release hole array 700, and the acoustic cavity 800 communicating with each other for providing an airflow channel during vibration of the diaphragm 410.

To sum up, in the MEMS microphone provided by the utility model, the supporting wall encloses into a cavity, and the vibrating diaphragm hangs in the cavity and the edge extends to the internal realization of supporting wall fixedly. The release hole array on the back plate structure comprises a plurality of release holes which penetrate through the back plate structure and are communicated with the cavity, in the process of forming the support wall body through the release hole array release sacrificial layer, the outline of the inner wall of the support wall body is mainly related to the outermost release holes of the release hole array, and the outermost release holes are configured into first release holes and second release holes which are arranged at intervals. Because the aperture of the first release hole is larger than that of the second release hole, the inner wall of the support wall body can be corroded into a wave shape by the first release hole, and a sharp corner in the wave shape can be cut off by the second release hole, so that the formation of the sharp corner is inhibited, the contour of the inner wall of the support wall body is smooth, the vibrating membrane is prevented from falling off due to the fact that the sharp corner punctures the vibrating membrane, and the service life and the reliability of the device are improved.

The above description is only for the preferred embodiment of the present invention, and does not limit the present invention. Any technical personnel who belongs to the technical field, in the scope that does not deviate from the technical scheme of the utility model, to the technical scheme and the technical content that the utility model discloses expose do the change such as the equivalent replacement of any form or modification, all belong to the content that does not break away from the technical scheme of the utility model, still belong to within the scope of protection of the utility model.

Claims (13)

1. A MEMS microphone, comprising:

a substrate;

the supporting wall body is arranged on the substrate and encloses a cavity;

the vibrating membrane is suspended in the cavity, and the edge of the vibrating membrane extends into the supporting wall body to be fixed;

the back plate structure is positioned on the supporting wall body and covers the cavity; and the number of the first and second groups,

and the release hole array comprises a plurality of release holes which penetrate through the back plate structure and are communicated with the cavity, the outermost circle of release holes positioned in the release hole array comprises first release holes and second release holes which are arranged at intervals, and the aperture of each first release hole is larger than that of each second release hole.

2. The MEMS microphone of claim 1, wherein a center of the cavity coincides with a center of the array of release holes.

3. The MEMS microphone of claim 1, wherein the first release hole is located on a first virtual circumference centered at a center of the array of release holes, the second release hole is located on a second virtual circumference centered at the center of the array of release holes, and the first virtual circumference is coincident or non-coincident with the second virtual circumference.

4. The MEMS microphone of claim 3, wherein a distance between adjacent first release holes is equal, and/or a distance between adjacent second release holes is equal.

5. The MEMS microphone of claim 1, wherein the release holes inside the outermost ring of release holes are third release holes arranged in a rectangular array, a honeycomb structure array, or a concentric rotation array.

6. The MEMS microphone of claim 1, wherein the backplate structure has a release region corresponding to the cavity, the array of release holes being located within the release region.

7. The MEMS microphone of any one of claims 1-6, wherein the release holes each have a pore size of 1 to 20 microns.

8. The MEMS microphone of any one of claims 1-6, wherein the release hole is one or more of a circular hole, a cross-flower hole, and a polygonal hole.

9. The MEMS microphone of claim 1, wherein the support wall comprises two stacked support layers, an edge of the diaphragm being sandwiched between the two support layers.

10. The MEMS microphone of claim 1, wherein the substrate has an acoustic cavity formed therein, the acoustic cavity extending through the substrate and communicating with the cavity.

11. The MEMS microphone of claim 1, wherein the backplate structure comprises a first protective layer, a second protective layer, and a backplate electrode between the first protective layer and the second protective layer, the first protective layer being closer to the diaphragm than the second protective layer.

12. The MEMS microphone of claim 11, wherein the first protective layer has a plurality of protrusions facing the cavity.

13. The MEMS microphone of claim 11, further comprising:

the first contact point is positioned on the same layer as the vibration film and is electrically connected with the vibration film;

the second contact point is positioned on the same layer as the back plate electrode and is electrically connected with the back plate electrode;

the first bonding pad is electrically connected with the first contact point through a conductive channel penetrating through the second protective layer, the first protective layer and at least part of the supporting wall;

and the second bonding pad is electrically connected with the second contact point through a conductive channel penetrating through the second protective layer.

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