CN220108197U

CN220108197U - Capacitive MEMS microphone

Info

Publication number: CN220108197U
Application number: CN202320807062.8U
Authority: CN
Inventors: 朱莉莉
Original assignee: Hubei Jiufengshan Laboratory
Current assignee: Hubei Jiufengshan Laboratory
Priority date: 2023-04-09
Filing date: 2023-04-09
Publication date: 2023-11-28
Anticipated expiration: 2033-04-09

Abstract

The utility model relates to the technical field of acoustic-electric conversion, and provides a capacitive MEMS microphone, which comprises a substrate, a vibrating diaphragm, a mounting rack, a backboard and a support column; the mounting frame is arranged on the upper surface of the substrate, and the vibrating diaphragm is arranged between the backboard and the substrate; the mounting frame is provided with a first mounting position and a second mounting position, the vibrating diaphragm is provided with an extension part along the radial direction, and the extension part is mounted on the first mounting position; the backboard is arranged on the second installation position; the middle part of vibrating diaphragm still is equipped with the elastic part, and the support column is located the backplate and is towards one side of vibrating diaphragm, and corresponds the setting with the elastic part. The capacitive MEMS microphone has larger effective area, namely larger capacitance variation under the same bias voltage, thereby having higher sensitivity and signal-to-noise ratio and effectively improving the performance of the MEMS microphone.

Description

Capacitive MEMS microphone

Technical Field

The utility model relates to the technical field of acoustic-electric conversion, in particular to a capacitive MEMS microphone.

Background

With the intellectualization of electronic products, the demand for audio interface devices has increased dramatically, and microphones used in electronic products are currently classified into two types, namely, ECM (Electret Condenser microphone) electret microphones and MEMS (Micro Electro Mechanical System) condenser microphones. The MEMS microphone has advantages of small volume, lower cost, better sensitivity consistency, and the like, is widely used, and is being widely studied.

However, the vibrating diaphragm of the existing MEMS microphone is in a circular structure, and the periphery of the MEMS vibrating diaphragm is directly fixed on the substrate, so that in the working state, when sound pressure acts on the vibrating diaphragm, the displacement of the central position of the vibrating diaphragm is maximum, the displacement of the periphery is zero, the vibration of each position of the vibrating diaphragm is uneven, and the effective area of the vibrating diaphragm is low under the same bias voltage, so that the sensitivity of the microphone is low, the SNR (signal to noise ratio) is low, and the SNR (signal to noise ratio) is one of the main performance indexes of the microphone, so that the performance of the microphone is poor.

Accordingly, in order to solve the above-mentioned problems and improve the sensitivity of the microphone, the present utility model proposes a novel capacitive MEMS microphone.

Disclosure of Invention

Based on the above description, the present utility model provides a capacitive MEMS microphone for improving the signal-to-noise ratio of the MEMS microphone to improve the sensitivity thereof.

The technical scheme for solving the technical problems is as follows:

the present utility model provides a capacitive MEMS microphone comprising: substrate, vibrating diaphragm, mounting rack, backboard and support column;

the mounting frame is arranged on the upper surface of the substrate, and the vibrating diaphragm is arranged between the backboard and the substrate;

the mounting frame is provided with a first mounting position and a second mounting position, the vibrating diaphragm is provided with an extension part along the radial direction, and the extension part is mounted on the first mounting position; the backboard is mounted on the second mounting position;

the middle part of vibrating diaphragm still is equipped with the elastic part, the support column is located the backplate is towards one side of vibrating diaphragm, and with the elastic part corresponds the setting.

On the basis of the technical scheme, the utility model can be improved as follows.

Further, the substrate is provided with a cavity, the diaphragm is arranged on the cavity, and the cavity is used for allowing sound pressure to pass through, so that the sound pressure acts on the diaphragm.

Further, a first gap is formed between the lower surface of the vibrating diaphragm and the upper surface of the substrate;

and a second gap is formed between the upper surface of the vibrating diaphragm and the lower surface of the backboard.

Further, the extension portion is bent.

Further, the plurality of the extension parts are provided;

the extending parts are sequentially distributed along the circumferential direction of the vibrating diaphragm.

Further, the number of the elastic parts is at least one;

when the elastic part is one, the elastic part is arranged at the axle center of the vibrating diaphragm;

when the elastic parts are a plurality of, a plurality of the elastic parts are arranged in an array.

Further, the number of the support columns is the same as the number of the elastic parts; the support column is arranged corresponding to the elastic part.

Further, in the non-working state, the lower surface of the support column and the elastic part have a third gap;

in the working state, the lower surface of the support column is abutted with the elastic part so as to support the vibrating diaphragm.

Further, the middle part of the vibrating diaphragm is arranged in a downward protruding mode;

or, the middle part of the backboard is arranged in an upward protruding way.

Further, the backboard is provided with a plurality of through holes; and a plurality of through hole arrays are distributed.

Compared with the prior art, the technical scheme of the utility model has the following beneficial technical effects:

the capacitive MEMS microphone provided by the utility model is provided with the substrate, the vibrating diaphragm, the mounting frame, the backboard and the support column, wherein the vibrating diaphragm is provided with the extension part along the radial direction, and the extension part is mounted on the mounting frame in a partially fixed mode, so that the rigidity of the vibrating diaphragm around the vibrating diaphragm can be reduced; meanwhile, the middle part of the vibrating diaphragm is provided with an elastic structure, and the elastic part is used as an elastic part, so that the rigidity of each position of the vibrating diaphragm is more uniform, and the displacement of the vibrating diaphragm under the action of sound pressure is more uniform; in addition, at the position opposite to the elastic part, a support column is arranged on one side of the back plate facing the vibrating diaphragm, and the support column can form a support for the vibrating diaphragm.

Compared with the prior art, the capacitive MEMS microphone provided by the utility model has larger effective area, namely larger capacitance variation under the same bias voltage, thereby having higher sensitivity and signal-to-noise ratio and effectively improving the performance of the MEMS microphone.

Drawings

Fig. 1 is a schematic diagram of the overall structure of a capacitive MEMS microphone according to an embodiment of the present utility model;

fig. 2 is a schematic diagram of a partial structure of a capacitive MEMS microphone according to an embodiment of the present utility model;

fig. 3 is a schematic cross-sectional structure diagram of a capacitive MEMS microphone according to an embodiment of the present utility model;

FIG. 4 is a schematic diagram showing the vibration mode-displacement contour effect of a diaphragm of a capacitive MEMS microphone according to an embodiment of the present utility model;

in the drawings, the list of components represented by the various numbers is as follows:

1. a substrate; 2. a vibrating diaphragm; 21. an extension; 22. an elastic part; 3. a mounting frame; 4. a back plate; 5. and (5) supporting the column.

Detailed Description

In order that the utility model may be readily understood, a more complete description of the utility model will be rendered by reference to the appended drawings. Embodiments of the utility model are illustrated in the accompanying drawings. This utility model may, however, be embodied in many different 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.

In describing embodiments of the present utility model, it should be noted that, unless explicitly stated and limited otherwise, the terms "coupled," "coupled," and "connected" should be construed broadly, and may be either a fixed connection, a removable connection, or an integral connection, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium. The specific meaning of the above terms in embodiments of the present utility model will be understood in detail by those of ordinary skill in the art.

In the description of embodiments of the present utility model, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

Furthermore, in the description of the embodiments of the present utility model, the term "plurality" means two or more in number.

Embodiments of the present utility model will be described in further detail with reference to fig. 1 to 4 and examples, which are provided to illustrate the present utility model but not to limit the scope of the present utility model.

As shown in fig. 1 to 3, the capacitive MEMS microphone provided by the embodiment of the utility model is composed of a substrate 1, a vibrating diaphragm 2, a mounting frame 3, a back plate 4 and a support column 5.

The mounting frame 3 is arranged on the upper surface of the substrate 1, and the vibrating diaphragm 2 is arranged between the backboard 4 and the substrate 1; the mounting frame 3 is provided with a first mounting position and a second mounting position, the vibrating diaphragm 2 is provided with an extension part 21 along the radial direction, and the extension part 21 is mounted on the first mounting position; the backboard 4 is arranged on the second installation position; the middle part of the vibrating diaphragm 2 is also provided with an elastic part 22, and the support column 5 is arranged on one side of the back plate 4 facing the vibrating diaphragm 2 and is correspondingly arranged with the elastic part 22.

Specifically, the capacitive microphone works on the principle: the MEMS microphone mainly comprises a vibrating diaphragm 2, a back plate 4 and a substrate 1, wherein the vibrating diaphragm 2 and the back plate 4 form a panel capacitor, bias voltage is applied to the vibrating diaphragm 2 or the back plate 4, sound pressure acts on the vibrating diaphragm 2, the distance between the vibrating diaphragm 2 and the back plate 4 is changed, the capacitor is changed, and voltage signals are output. The corresponding calculation formula is as follows:

wherein, sensitivity is as followsFor sensitivity, V is the bias voltage, _Δ c is capacitance variation under sound pressure effect, C ₀ Is the initial capacitance.

In order to reduce the damping of the pressing film between the diaphragm 2 and the back plate 4, the back plate 4 is provided with a through hole structure.

Specifically, as shown in fig. 1, the back plate 4 has a plurality of through holes; the plurality of through holes are distributed in an array, the specific number and the arrangement mode of the through holes are not particularly limited, and the through holes can be arranged according to actual needs.

The signal-to-noise ratio (SNR) is a main performance index of a microphone, and the improvement of the signal-to-noise ratio is mainly achieved by improving the sensitivity of the MEMS and reducing the noise of the MEMS. The bias voltage V is usually set to be the pull-in voltage V between the diaphragm 2 and the backplate 4 of the microphone _pullin Is a certain proportion (when there is a voltage between the diaphragm 2 and the back plate 4, an electrostatic force is generated between the diaphragm 2 and the back plate 4, when the voltage is large enough, the diaphragm 2 and the back plate 4 will attract together under the action of the electrostatic force, V _pullin The maximum voltage at which no attraction between the diaphragm 2 and the backplate 4 occurs).

In summary, under the same bias voltage, the capacitance variation can be increased _Δ C to increase the sensitivity of the microphone.

Wherein the capacitance variation _Δ C is proportional to the effective area A of the diaphragm 2 _eff . Effective area A _eff The calculation formula of (2) is as follows:

w is the displacement of the diaphragm 2 everywhere,the integral is the integral of the displacement of the diaphragm 2 to the area of the diaphragm 2, w ₀ Is the displacement amount at the maximum displacement of the diaphragm 2.

The effective area of the diaphragm 2 is generally smaller than the actual area of the diaphragm 2, and the more uniform the displacement of the diaphragm 2 is, the closer the effective area is to the actual area, namely the larger the effective area is.

As shown in fig. 3, the capacitive MEMS microphone provided by the embodiment of the present utility model is provided with a substrate 1, a diaphragm 2, a mounting frame 3, a back plate 4 and a support column 5, wherein the substrate 1 is provided with a cavity, the diaphragm 2 is disposed on the cavity, and the cavity is used for passing sound pressure, so that the sound pressure acts on the diaphragm 2.

In a preferred example, the mounting frame 3 and the back plate 4 may be formed as an integral structure, and they are formed in the same process.

Meanwhile, as shown in fig. 3, a first gap is formed between the lower surface of the diaphragm 2 and the upper surface of the substrate 1; the upper surface of the diaphragm 2 and the lower surface of the back plate 4 are provided with a second gap so that the diaphragm 2 can displace under the action of sound pressure.

The specific dimensions of the first gap and the second gap are not limited herein, and may be set according to actual needs.

As shown in fig. 2, the diaphragm 2 is provided with an extension 21 in the radial direction, and the extension 21 is mounted on the mounting frame 3 in a partially fixed manner, that is, the end of the extension 21 is connected to the mounting frame, so that the rigidity around the diaphragm 2 can be reduced.

Further, as shown in fig. 2, the middle portion of the diaphragm 2 has an elastic structure as the elastic portion 22. As shown in fig. 3, at a position opposite to the elastic portion 22, a support column 5 is provided on the back plate 4, and the support column 5 can form a support for the diaphragm 2, increasing the rigidity of the diaphragm 2. The elastic parts 22 and the support columns 5 are combined to ensure that the rigidity of each position of the diaphragm 2 is more uniform, so that the displacement of the diaphragm 2 under the action of sound pressure is more uniform.

It should be noted that: the support column 5 is also called an insulating column, and in practical application, is not limited to a cylinder, and may be other shapes with the same function, such as a truncated cone shape, etc.; meanwhile, the insulating column may have a multilayer structure, and may include an electrode layer structure at a position not in contact with the diaphragm.

Namely, the elastic part 22 and the support column 5 are arranged, so that the vibration effective area of the vibrating diaphragm 2 can be increased under the same chip size, and the vibrating diaphragm has larger capacitance variation under the same bias voltage, so that the vibrating diaphragm has larger sensitivity and further has larger microphone signal-to-noise ratio.

In addition to the above embodiment, the extension portion 21 may be in a bent shape, or may be in a regular shape, or may be in an irregular shape, or may be in a straight bent shape, or may be in a curved bent shape, or may be preferably in a spring shape, which is not particularly limited, and various bent shapes can achieve the effects of the present utility model and fall within the scope of the embodiments of the present utility model.

Further, the extension portion 21 is plural; the plurality of extension portions are sequentially arranged along the circumferential direction of the diaphragm 2, the number of which is not particularly limited, and may be set according to actual needs.

In a specific example, as shown in fig. 2, there are 8 extending portions 21, and the 8 extending portions 21 are uniformly arranged on the outer edge of the diaphragm 2 along the circumferential direction of the diaphragm 2.

Based on the above embodiment, the number of the elastic portions 22 is at least one. The method is divided into the following two cases:

mode one: when the number of the elastic parts 22 is one, the elastic parts 22 are disposed at the axial center of the diaphragm 2, as shown in fig. 2.

Mode two: when the number of elastic portions 22 is plural, the plural elastic portions 22 are arranged in an array. The number of the components is not particularly limited, and the components can be set according to actual needs.

It should be noted that: the number of the support columns 5 is the same as the number of the elastic parts 22; the support columns 5 are arranged in one-to-one correspondence with the elastic parts 22.

In actual operation, the support column 5 and the elastic portion 22 have two states:

in the non-operating state, the lower surface of the support column 5 has a third clearance with the elastic portion 22; the specific size of the gap is not limited, the gap is set according to actual needs, and the gap is not too large or too small, so that the following working state is required to be met;

in the operating state, the lower surface of the support column 5 abuts against the elastic portion 22 to support the diaphragm 2.

On the basis of the embodiment, optionally, the middle part of the diaphragm 2 is arranged in a protruding way; or, the middle part of backplate 4 upwards protruding setting is setting up vibrating diaphragm 2 or backplate 4 to protruding structure, can effectively prevent that vibrating diaphragm 2 and backplate 4 from taking place to adhere.

In a specific example, the number of the protrusions may be 1 or more, the positions of the protrusions correspond to the positions of the support columns 5, and the sizes of the protrusions are slightly smaller than the end face sizes of the support columns 5. In the case of a plurality of protrusions, the protrusion structures may be uniformly distributed over the entire diaphragm 2 or the backplate 4.

In order to further prove the beneficial effects of the embodiment of the utility model, fig. 4 shows a schematic diagram of the contour effect of the vibration mode-displacement of the vibrating diaphragm 2, and it can be seen from the diagram that the capacitive MEMS microphone provided by the embodiment of the utility model has a larger effective area, so that the capacitive MEMS microphone has a larger capacitance variation under the same bias voltage, thereby having higher sensitivity and signal-to-noise ratio, and effectively improving the performance of the MEMS microphone.

In the description of the present specification, the description with reference to the term "particular example" or "some examples" or the like means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the embodiments of the utility model. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present utility model, and are not limiting; although the utility model has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present utility model.

Claims

1. A capacitive MEMS microphone, comprising: substrate, vibrating diaphragm, mounting rack, backboard and support column;

2. The capacitive MEMS microphone of claim 1, wherein the substrate is provided with a cavity, the diaphragm being disposed on the cavity, the cavity being configured to be penetrated by a sound pressure such that the sound pressure acts on the diaphragm.

3. The capacitive MEMS microphone of claim 1, wherein a lower surface of the diaphragm and an upper surface of the substrate are provided with a first gap;

4. The capacitive MEMS microphone of claim 1, wherein the extension is bent.

5. The capacitive MEMS microphone of claim 4, wherein the extension is a plurality of;

6. The capacitive MEMS microphone of claim 1, wherein the number of elastic portions is at least one;

7. The capacitive MEMS microphone of claim 6, wherein the number of support posts is the same as the number of elastic portions; the support column is arranged corresponding to the elastic part.

8. The capacitive MEMS microphone of claim 7, wherein in a non-operational state, a lower surface of the support post has a third gap with the elastic portion;

9. The capacitive MEMS microphone of claim 1, wherein the middle portion of the diaphragm is convex downward;

or, the middle part of the backboard is arranged in an upward protruding way.

10. The capacitive MEMS microphone of claim 1, wherein the backplate has a plurality of through holes; and a plurality of through hole arrays are distributed.