WO2022156200A1

WO2022156200A1 - Differential-capacitance type mems microphone and manufacturing method therefor

Info

Publication number: WO2022156200A1
Application number: PCT/CN2021/113044
Authority: WO
Inventors: 冯栋
Original assignee: 无锡华润上华科技有限公司
Priority date: 2021-01-20
Filing date: 2021-08-17
Publication date: 2022-07-28
Also published as: CN114866936A

Abstract

The present invention relates to a differential-capacitance type MEMS microphone and a manufacturing method therefor. The microphone comprises: a first diaphragm; a first back plate, disposed above the first diaphragm; a second back plate; a second diaphragm, disposed above the second back plate; and a support layer, disposed between the first diaphragm and the first back plate and between the second back plate and the second diaphragm. A first capacitor formed by the first diaphragm and the first back plate is configured to output a first capacitance value signal, a second capacitor formed by the second diaphragm and the second back plate is configured to output a second capacitance value signal, and the first capacitance value signal and the second capacitance value signal form a differential signal. In the present invention, the first capacitance value signal and the second capacitance value signal output by the microphone can constitute the differential signal, thereby improving the high-frequency noise immunity, and ensuring a better audio signal processing effect. Moreover, the manufacturing process is simplified, photoetching steps are reduced, the manufacturing process is compatible with existing mature technologies, the microphone is easier to large-scale mass production, and the manufacturing difficulty and cost are low.

Description

Differential capacitive MEMS microphone and method of making the same

technical field

The invention relates to the technical field of semiconductor devices, in particular to a differential capacitive MEMS microphone, and also to a manufacturing method of a differential capacitive MEMS microphone.

Background technique

Micro-Electro-Mechanical System (MEMS) devices are usually produced using integrated circuit manufacturing technology. Silicon-based microphones have broad application prospects in hearing aids and mobile communication equipment. The research on MEMS microphone chips has been more than 20 years. During this period, many types of microphone chips have been developed, including piezoresistive, piezoelectric and capacitive, among which capacitive MEMS microphones are the most widely used. Capacitive MEMS microphones have the following advantages: small size, high sensitivity, good frequency characteristics, and low noise.

An exemplary capacitive MEMS microphone structure is a combination design of a single diaphragm and a single backplate. One is a structural design in which the diaphragm of the MEMS microphone is at the bottom and the backplate is at the top; Structural design of the backplane below. The anti-interference ability of the above-mentioned microphone structure is poor, and the THD Value (Total Harmonic Distortion, total harmonic distortion value) of the microphone is relatively large.

SUMMARY OF THE INVENTION

Based on this, it is necessary to provide a differential capacitive MEMS microphone with strong anti-interference ability and a manufacturing method thereof.

A differential condenser MEMS microphone, comprising:

the first diaphragm;

a first back plate, arranged above the first diaphragm;

second backplane;

The second diaphragm is arranged above the second back plate;

a support layer, arranged between the first diaphragm and the first backplate, and between the second backplate and the second diaphragm;

Wherein, the first capacitor formed by the first diaphragm and the first backplate is used to output the first capacitance value signal, and the second capacitor formed by the second diaphragm and the second backplate is used to output the second capacitance value signal, the first capacitance value signal and the second capacitance value signal constitute a differential signal.

The above differential capacitive MEMS microphone, when the sound pressure acts downward on the device, the first diaphragm and the second diaphragm move downward, the distance between the first diaphragm and the first back plate becomes larger, and the first capacitance value changes. while the distance between the second diaphragm and the second back plate becomes smaller, and the second capacitance value becomes larger. Since the changes of the first capacitance value and the second capacitance value are opposite, the first capacitance value signal and the second capacitance value signal form a differential signal, which can improve high frequency noise immunity and ensure better audio signal processing effect.

In one embodiment, the shape and size of the first diaphragm are the same as those of the second diaphragm, and the shape and size of the first back plate are the same as those of the second back plate.

In one embodiment, the support layer is a sacrificial layer of insulating material.

In one embodiment, a support layer is not provided at a part of the position between the first diaphragm and the first back plate to form a first cavity, and a part of the position between the second diaphragm and the second back plate is No support layer is provided to form the second cavity.

In one embodiment, a plurality of sound holes are opened on the first backplane and the second backplane.

In one of the embodiments, the first diaphragm and the second diaphragm are flexible films, and the first backplane and the second backplane are rigid films.

In one of the embodiments, it further includes a base plate, and the first diaphragm and the second back plate are arranged on the base plate.

In one of the embodiments, an insulating layer is further included, and the insulating layer is provided between the base plate and the first diaphragm, and between the base plate and the second back plate.

In one embodiment, it also includes:

a first pad, arranged on the upper surface of the first backplane;

the second pad is provided on the upper surface of the first diaphragm;

a third pad, arranged on the upper surface of the second diaphragm;

The fourth pad is arranged on the upper surface of the second backplane.

In one embodiment, the first diaphragm and the second diaphragm are both conductive materials.

A method for manufacturing a differential capacitive MEMS microphone, comprising:

forming a first diaphragm and a second back plate on the substrate by deposition, photolithography and etching;

A sacrificial layer is formed on the first diaphragm and the second backplane by deposition, photolithography and etching;

forming a second diaphragm and a first backplate on the sacrificial layer by deposition, photolithography and etching;

By photolithography and etching, the substrate is etched out of the back cavity;

The sacrificial layer is released by the etchant, a first cavity is formed between the first diaphragm and the first back plate, a second cavity is formed between the second diaphragm and the second back plate, and a second cavity is formed between the second diaphragm and the second back plate. A plurality of sound holes are formed on the first backplane and the second backplane.

The above-mentioned manufacturing method of the differential capacitive MEMS microphone has a simple manufacturing process, less lithography layers, is compatible with existing mature technologies, is easier to mass-produce, and has low manufacturing difficulty and cost.

In one embodiment, after the step of forming the second diaphragm and the first back plate and before the step of etching the substrate out of the back cavity, the method further includes deposition, photolithography and etching, forming a first pad located on the upper surface of the first backplate, a second pad located on the upper surface of the first diaphragm, a third pad located on the upper surface of the second diaphragm, and a third pad located on the upper surface of the second diaphragm the step of a fourth pad on the upper surface of the second backplane.

In one embodiment, the step of etching the substrate out of the back cavity by photolithography and etching includes forming the back cavity by double-sided photolithography and inductively coupled plasma etching processes.

In one embodiment, the step of etching the substrate out of the back cavity further includes backside thinning of the substrate.

In one embodiment, the step of releasing the sacrificial layer with an etchant includes etching the sacrificial layer using a buffered oxide etchant.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application or in the traditional technology, the following briefly introduces the accompanying drawings that are used in the description of the embodiments or the traditional technology. Obviously, the drawings in the following description are only the For some embodiments of the application, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without any creative effort.

FIG. 1 is an exemplary capacitive MEMS microphone structure;

FIG. 2 is an exemplary capacitive MEMS microphone structure with a dual backplane structure;

3 is a schematic structural diagram of a capacitive MEMS microphone in an embodiment;

4 is a flowchart of a method for manufacturing a capacitive MEMS microphone in one embodiment;

5a, 5b and 5c are schematic cross-sectional views of the device in step S410 in one embodiment;

6 is a schematic cross-sectional view of the device after step S420 is completed in one embodiment;

7a, 7b and 7c are schematic cross-sectional views of the device in step S430 in one embodiment;

8 is a schematic cross-sectional view of the device after step S440 is completed in one embodiment;

FIG. 9 is a schematic cross-sectional view of the device after step S450 is completed in one embodiment.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terms used herein in the description of the present invention are for the purpose of describing specific embodiments only, and are not intended to limit the present invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions are used herein for the purpose of illustration only. When an element or layer is referred to as being "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it can be directly on the other elements or layers, Adjacent thereto, connected or coupled to other elements or layers, or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other elements or layers, there are no intervening elements or layers present. Floor. It will be understood that although the terms first, second, third, A, B, C, etc. may be used to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections may not be should 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 invention.

When the terms "comprising" and/or "comprising" are used in this specification, they indicate the presence of the stated feature, integer, step, operation, element and/or component, but do not preclude the presence or addition of one or more other features, Entities, steps, operations, elements, components and/or combinations thereof. The singular forms "a," "an," and "the/the" are intended to include the plural forms as well, unless the context clearly dictates otherwise.

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 invention, such that variations in the shapes shown may be contemplated due, for example, to manufacturing techniques and/or tolerances. Accordingly, embodiments of the present invention should not be limited to the particular shapes of the regions shown herein, but include shape deviations due, for example, to manufacturing techniques. For example, an implanted region shown as a rectangle typically has rounded or curved features and/or a gradient of implant concentration at its edges rather than a binary change from implanted to non-implanted region. Likewise, a buried region formed by implantation may result in some implantation in the region between the buried region and the surface over which the implantation proceeds. Thus, the regions shown in the figures are schematic in nature and their shapes do not represent the actual shape of a region of a device and do not limit the scope of the invention.

FIG. 1 is an exemplary structure of a capacitive MEMS microphone, which has poor anti-interference ability and a large THD Value (Total Harmonic Distortion, total harmonic distortion value) of the microphone.

FIG. 2 is an exemplary structure of a capacitive MEMS microphone with a double-back plate structure, which can eliminate the non-linear change of capacitance caused by the vibration of the diaphragm and reduce the total harmonic distortion. However, the thickness of the structure is large, so the warpage of the wafer is large (mainly, the warpage of the substrate is large). On the other hand, the structure is relatively complex, with many lithography layers, which is incompatible with the existing mature MEMS microphone structure, and the manufacturing cost and difficulty are high, which is not conducive to market competition.

Referring to FIG. 3 , the present application provides a differential capacitive MEMS microphone including a first diaphragm 112 , a first backplate 114 , a second diaphragm 122 , a second backplate 124 and a support layer 130 . The first back plate 114 is disposed above the first diaphragm 112 , and the second diaphragm 122 is disposed above the second back plate 124 . The support layer 130 is disposed between the first diaphragm 112 and the first back plate 114 and between the second back plate 124 and the second diaphragm 122 .

The first capacitor C1 formed by the first diaphragm 112 and the first back plate 114 is used to output the first capacitance value signal, and the second capacitor C2 formed by the second diaphragm 122 and the second back plate 124 is used to output the second capacitance value. The capacitance value signal, the first capacitance value signal and the second capacitance value signal constitute a differential signal.

In an embodiment of the present application, the first diaphragm 112 and the second diaphragm 122 are flexible films, and the first backplate 114 and the second backplate 124 are rigid films. Specifically, the first vibrating film 112 and the second vibrating film 122 are a layer of flexible thin films with tensile stress and electrical conductivity. When the surrounding air vibrates, a certain degree of deformation can occur, and the The two backplanes 124 together form a plate capacitor and serve as one pole of the plate capacitor. The stress of the first backplane 114 and the second backplane 124 is relatively large, and they are fixed when the first diaphragm 112 and the second diaphragm 122 vibrate. In an embodiment of the present application, the first diaphragm 112 is softer than the first back plate 114 , and the second diaphragm 122 is softer than the second back plate 124 .

In an embodiment of the present application, the first diaphragm 112 , the second diaphragm 122 , the first back plate 114 and the second back plate 124 are all conductive materials. In other embodiments, the first diaphragm 112 , the second diaphragm 122 , the first back plate 114 and the second back plate 124 may also be a composite layer structure including a conductive layer, for example, one of the following materials or Various: Si, Ge, SiGe, SiC, Al, W, Ti, or nitrides of Al/W/Ti. In the embodiment shown in FIG. 3 , the first backplane 114 includes a polysilicon film made of a conductive material and a silicon nitride film on the polysilicon film; similarly, the second backplane 124 also includes a polysilicon film made of a conductive material and a polysilicon film on the polysilicon film. of silicon nitride films.

It can be understood that FIG. 3 is an example of some main structures of the capacitive MEMS microphone, and the capacitive MEMS microphone may have other structures besides the structures shown in the figure.

The above differential capacitive MEMS microphone, when the sound pressure acts downward on the device, the first diaphragm 112 and the second diaphragm 122 move downward, the distance between the first diaphragm 112 and the first back plate 114 increases, and the first diaphragm 112 and the first back plate 114 become larger. A capacitance value becomes smaller; while the distance between the second diaphragm 122 and the second back plate 124 becomes smaller, and the second capacitance value becomes larger. Since the changes of the first capacitance value and the second capacitance value are opposite, the first capacitance value signal and the second capacitance value signal will form a differential signal, which can improve the high frequency immunity, reduce the total harmonic distortion, and ensure better audio signal processing effects.

In an embodiment of the present application, the shape and size of the first diaphragm 112 are the same as those of the second diaphragm 122 , the shape and size of the first back plate 114 are the same as those of the second back plate 124 , and the The material is the same as that of the second diaphragm 122 . In this way, the absolute value of the variation of the first capacitance value can be equal to the absolute value of the variation of the second capacitance value.

In the embodiment shown in FIG. 3 , the supporting layer 130 is not provided in the part between the first diaphragm 112 and the first back plate 114 to form the first cavity 131 , the second diaphragm 122 and the second back plate 124 The supporting layer 130 is not provided at the partial positions in between so as to form the second cavity 133 . In one embodiment of the present application, the first cavity 131 and the second cavity 133 are cylindrical cavities; in other embodiments, the first cavity 131 and the second cavity 133 may also be cuboid or other shapes .

In an embodiment of the present application, the support layer 130 is a sacrificial layer, and the cavity is actually released from the sacrificial layer. During the release process, the sacrificial layer at the position of the cavity is etched away to form a cavity. In one embodiment of the present application, the thickness of the support layer 130 is 3-5 microns. In an embodiment of the present application, the support layer 130 is made of insulating material. In an embodiment of the present application, the conductive structure (polysilicon film) of the second backplane 124 and the first vibrating film 112 are insulated and isolated by the support layer 130 .

In the embodiment shown in FIG. 3 , the first backplane 114 and the second backplane 124 are each provided with a plurality of sound holes of a specific size, and the sound waves can be conducted to the first diaphragm 112/second diaphragm through the sound holes 122. In one embodiment of the present application, the sound holes are uniformly distributed on the first backplane 114 and the second backplane 124; in other embodiments, the sound holes may also be non-uniformly distributed, for example, on the first backplane 114/the second backplane 124. The middle area of the two backplanes 124 is more concentrated.

In the embodiment shown in FIG. 3 , the differential capacitive MEMS microphone further includes a substrate 110 . The first diaphragm 112 and the second back plate 124 are disposed on the substrate 110 . In this embodiment, the material of the substrate 110 is Si, and the material of the substrate 110 may also be other semiconductors or semiconductor compounds, such as one of Ge, SiGe, SiC, SiO2 or Si3N4. The substrate 110 is provided with a back cavity directly below the first cavity 131 and the second cavity 133 .

In the embodiment shown in FIG. 3 , the differential capacitive MEMS microphone further includes an insulating layer 113 disposed between the substrate 110 and the first diaphragm 112 and between the substrate 110 and the second backplane 124 . The insulating layer 113 serves to insulate the substrate 100 and the lower electrode layer from each other. In one embodiment of the present application, the insulating layer 113 also serves as an etch stop layer for back cavity etching. In one embodiment of the present application, the insulating layer 113 is a silicon oxide layer.

In an embodiment of the present application, the differential capacitive MEMS microphone further includes a first pad 142 disposed on the upper surface of the first back plate 114, a second pad 144 disposed on the upper surface of the first diaphragm 112, The third pad 146 is provided on the upper surface of the second diaphragm 122 , and the fourth pad 148 is provided on the upper surface of the second back plate 124 . In one embodiment of the present application, the first pad 142 , the second pad 144 , the third pad 146 and the fourth pad 148 are all made of metal. The first pad 142 , the second pad 144 , the third pad 146 and the fourth pad 148 can connect the first backplane 114 / the first diaphragm 112 / the second vibration when the differential capacitive MEMS microphone package is wired. The membrane 122/second backplane 124 is drawn out. In the embodiment shown in FIG. 3 , the first pad 142 is disposed on the conductive structure (polysilicon film) extending from the first backplane 114 to the support layer 130 , and the position where the first pad 142 is disposed is not provided with nitriding Silicon film; similarly, the fourth pad 148 is disposed on the conductive structure (polysilicon film) extending from the second backplane 124 to the support layer 130, and the silicon nitride film is not disposed at the position where the fourth pad 148 is disposed.

In an embodiment of the present application, the above-mentioned differential capacitive MEMS microphone can increase the acoustic overload point of total harmonic distortion (THD) of 10% to 135dB SPL, and the signal-to-noise ratio can reach 70dB, which is about 6dB higher than the prior art . Doubles the distance at which the microphone accepts user voice commands, especially for far-field pickup devices such as smart speakers and smart homes.

The present application accordingly provides a method for manufacturing a differential capacitive MEMS microphone, which can be used to manufacture the differential capacitive MEMS microphone described in any of the above embodiments. 4 is a flowchart of a method for manufacturing a differential capacitive MEMS microphone in an embodiment, including the following steps:

S410, forming a first diaphragm and a second back plate on the substrate by deposition, photolithography and etching.

Referring to FIG. 5a, after polysilicon (Poly) and silicon nitride are deposited, a polysilicon layer 212a and a silicon nitride layer 224a are formed.

In the embodiment shown in FIG. 5a, before depositing polysilicon and silicon nitride, a step of forming a silicon oxide layer 213 on the substrate 210 is further included. Polysilicon and silicon nitride are deposited on the silicon oxide layer 213 . In one embodiment of the present application, the silicon oxide layer 213 is formed by depositing a field oxygen layer. In other embodiments, the silicon oxide layer 213 may also be formed by thermal growth.

In one embodiment of the present application, the material of the substrate 210 is Si. The material of the substrate 210 may also be other semiconductors or semiconductor compounds, such as one of Ge, SiGe, SiC, SiO2 or Si3N4.

Referring to FIG. 5b, after polysilicon and silicon nitride are deposited, the silicon nitride layer 224a is photo-etched and etched; then the photoresist is removed, and the poly-silicon layer 212a is photo-etched and etched to form the second backplane 224 and the first vibration plate 224a. Membrane 212, as shown in Figure 5c.

S420, a sacrificial layer is formed on the first diaphragm and the second backplane by deposition, photolithography and etching.

Referring to FIG. 6, in this embodiment, an oxide layer is deposited on the first diaphragm 212 and the second back plate 224, and then a sacrificial layer 230 is formed by photolithography and etching.

S430, forming a second diaphragm and a first back plate on the sacrificial layer by deposition, photolithography and etching.

Referring to FIG. 7a, polysilicon and silicon nitride are deposited on the sacrificial layer 230 to form a polysilicon layer 222a and a silicon nitride layer 214a. Then, the silicon nitride layer 214a is photo-etched and etched, as shown in FIG. 7b; the photoresist is then removed, and the polysilicon layer 222a is photo-etched and etched to form the first back plate 214 and the second diaphragm 222, as shown in FIG. 7c shown.

S440, first to fourth pads are formed by deposition, photolithography and etching.

A metal layer is deposited, and then a first pad 242 located on the upper surface of the first backplane 214 and a second pad located on the upper surface of the first diaphragm 212 are formed through the pad (PAD) metal lithography and etching 244 , a third pad 246 located on the upper surface of the second diaphragm 222 , and a fourth pad 248 located on the upper surface of the second back plate 224 . Specifically, the first pad 242 is provided on the conductive structure (polysilicon film) extending from the first backplane 214 to the support layer 230, and the silicon nitride film is not provided at the position where the first pad 242 is provided; The four pads 248 are arranged on the conductive structure (polysilicon film) extending from the second backplane 224 to the support layer 230 , and the silicon nitride film is not arranged at the position where the fourth pad 248 is arranged, see FIG. 8 .

S450, the substrate is etched out of the back cavity through photolithography and etching.

In one embodiment of the present application, the photolithography adopts a double-sided photolithography process, and then the back surface of the substrate 210 is etched through an inductively coupled plasma (Inductively Coupled Plasma, ICP) etching process to form a back cavity, see FIG. 9 .

In an embodiment of the present application, before step S450, a step of thinning the back surface of the substrate 210 is further included. Specifically, thinning may be performed after step S440 and before step S450.

S460, releasing the sacrificial layer through an etchant.

After the sacrificial layer 230 is etched, a first cavity is formed between the first diaphragm 212 and the first back plate 214, a second cavity is formed between the second diaphragm 222 and the second back plate 224, and a first cavity is formed between the second diaphragm 222 and the second back plate 224. A plurality of sound holes are formed on the back plate 214 . And since the material of the sacrificial layer 230 is the same as that of the silicon oxide layer 213 , the silicon oxide layer 213 will be etched together, so that a plurality of acoustic holes are formed on the second backplane 224 . For the structure after etching, please refer to FIG. 3 . The conductive structure (polysilicon film) of the second backplane 124 and the first vibrating film 112 are insulated and isolated by the support layer 130 .

In one embodiment of the present application, the etchant is a buffered oxide etchant (BOE).

The above-mentioned manufacturing method of a differential capacitive MEMS microphone has a brief manufacturing process and few lithography layers (mainly seven lithography steps from steps S410 to S450, wherein steps S410 and S430 are both two lithography steps. The structure shown in FIG. 2 is used as a reference. Usually requires more than 12 lithography), and is compatible with the existing mature technology, it is easier to mass-produce, and the manufacturing difficulty and cost are low.

It should be understood that although the various steps in the flowchart of FIG. 4 are sequentially displayed according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, the execution of these steps is not strictly limited to the order, and these steps may be performed in other orders. Moreover, at least a part of the steps in FIG. 4 may include multiple steps or multiple stages, these steps or stages are not necessarily executed at the same time, but may be executed at different times, and the execution sequence of these steps or stages is also It does not have to be performed sequentially, but may be performed alternately or alternately with other steps or at least a portion of the steps or stages within the other steps.

In the description of this specification, reference to the description of the terms "some embodiments," "other embodiments," "ideal embodiments," etc. means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in the present specification. at least one embodiment or example of the invention. In this specification, schematic descriptions of the above terms do not necessarily refer to the same embodiment or example.

The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity, all possible combinations of the technical features of the above-described embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, all It is considered to be the range described in this specification.

The above-mentioned embodiments only represent several embodiments of the present application, and the descriptions thereof are relatively specific and detailed, but should not be construed as a limitation on the scope of the patent application. It should be noted that, for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can be made, which all belong to the protection scope of the present application. Therefore, the scope of protection of the patent of the present application shall be subject to the appended claims.

Claims

A differential capacitive MEMS microphone, comprising:

the first diaphragm;

a first back plate, arranged above the first diaphragm;

second backplane;

The second diaphragm is arranged above the second back plate;

a support layer, arranged between the first diaphragm and the first backplate, and between the second backplate and the second diaphragm;

Wherein, the first capacitor formed by the first diaphragm and the first backplate is used to output the first capacitance value signal, and the second capacitor formed by the second diaphragm and the second backplate is used to output the second capacitance value signal, the first capacitance value signal and the second capacitance value signal constitute a differential signal.
The differential condenser MEMS microphone according to claim 1, wherein the shape and size of the first diaphragm are the same as those of the second diaphragm, and the shape and size of the first back plate are the same as those of the first diaphragm. The two backplanes are the same.
The differential capacitive MEMS microphone according to claim 1, wherein the support layer is a sacrificial layer of insulating material, and a part of the position between the first diaphragm and the first back plate is not provided with a support layer to form In the first cavity, a support layer is not provided in a part of the position between the second diaphragm and the second back plate to form a second cavity.
The differential capacitive MEMS microphone according to claim 1, wherein the thickness of the support layer is 3-5 microns.
The differential condenser MEMS microphone according to claim 1, wherein a plurality of sound holes are opened on the first backplane and the second backplane.
The differential capacitive MEMS microphone according to claim 1, wherein the first diaphragm and the second diaphragm are flexible films, and the first backplane and the second backplane are rigid films.
The differential capacitive MEMS microphone according to claim 1, further comprising a substrate, and the first diaphragm and the second back plate are disposed on the substrate.
The differential capacitive MEMS microphone according to claim 7, further comprising an insulating layer, the insulating layer is provided between the substrate and the first diaphragm, and between the substrate and the second backplane .
The differential capacitive MEMS microphone of claim 1, further comprising:

a first pad, arranged on the upper surface of the first backplane;

a second pad, arranged on the upper surface of the first diaphragm;

a third pad, arranged on the upper surface of the second diaphragm;

The fourth pad is arranged on the upper surface of the second backplane.
The differential capacitive MEMS microphone according to claim 1, wherein the first diaphragm and the second diaphragm are both conductive materials.
A method for manufacturing a differential capacitive MEMS microphone, comprising:

forming a first diaphragm and a second back plate on the substrate by deposition, photolithography and etching;

A sacrificial layer is formed on the first diaphragm and the second backplane by deposition, photolithography and etching;

forming a second diaphragm and a first backplate on the sacrificial layer by deposition, photolithography and etching;

By photolithography and etching, the substrate is etched out of the back cavity;

The sacrificial layer is released by the etchant, a first cavity is formed between the first diaphragm and the first back plate, a second cavity is formed between the second diaphragm and the second back plate, and a second cavity is formed between the second diaphragm and the second back plate. A plurality of sound holes are formed on the first backplane and the second backplane.
The method for manufacturing a differential capacitive MEMS microphone according to claim 11, wherein after the step of forming the second diaphragm and the first back plate, and before the step of etching the substrate out of the back cavity , and also includes forming a first pad located on the upper surface of the first backplane, a second pad located on the upper surface of the first diaphragm, and a second pad located on the second diaphragm through deposition, photolithography and etching. the steps of a third pad on the upper surface of the film and a fourth pad on the upper surface of the second backplane.
The method for manufacturing a differential capacitive MEMS microphone according to claim 11, wherein the step of etching the substrate out of the back cavity by photolithography and etching includes double-sided photolithography and inductive coupling. A plasma etching process forms the back cavity.
The method for manufacturing a differential capacitive MEMS microphone according to claim 11, wherein the step of etching the substrate out of the back cavity further comprises thinning the back surface of the substrate.
The method for manufacturing a differential capacitive MEMS microphone according to claim 11, wherein the step of releasing the sacrificial layer through an etchant comprises etching the sacrificial layer with a buffered oxide etchant.