WO2021134672A1

WO2021134672A1 - Piezoelectric mems microphone

Info

Publication number: WO2021134672A1
Application number: PCT/CN2019/130909
Authority: WO
Inventors: 童贝; 石正雨; 沈宇; 李杨
Original assignee: 瑞声声学科技(深圳)有限公司; 瑞声科技（南京）有限公司
Priority date: 2019-12-31
Filing date: 2019-12-31
Publication date: 2021-07-08

Abstract

Provided is a piezoelectric MEMS microphone, comprising a substrate provided with a back cavity, a vibrating diaphragm suspended in the back cavity, and an elastic support piece connected between the vibrating diaphragm and the substrate; the vibrating diaphragm is fixed on the substrate, two sides of the side surface of the vibrating diaphragm away from the back cavity along the vibration direction of the vibrating diaphragm are respectively provided with a first piezoelectric diaphragm, the side surface of the vibrating diaphragm facing the back cavity is provided with a second piezoelectric diaphragm, and the second piezoelectric diaphragm is connected in parallel to the first piezoelectric diaphragm. In the present design, a structure corresponding to the second piezoelectric diaphragm corresponding to the first piezoelectric diaphragm above the vibrating diaphragm is mainly prepared below the vibrating diaphragm, and the second piezoelectric diaphragm is connected is parallel to the first piezoelectric diaphragm. The design slightly reduces sensitivity, but significantly decreases noise since the capacitance is doubled after the parallel connection, such that the total signal-to-noise ratio (SNR) is considerably increased.

Description

Piezo MEMS microphone

Technical field

The utility model relates to the field of microphones.

Background technique

At present, piezoelectric MEMS microphones mainly adopt the method of diaphragm bending or cantilever bending, which generates a certain stress at the anchor point, which causes the piezoelectric diaphragm covering it to be compressed, thereby generating a certain charge output. The overall noise level is relatively high, and the signal-to-noise ratio can not be significantly improved by changing the thickness and stress of the film and optimizing the design of slots and holes on the diaphragm.

Therefore, it is necessary to provide a piezoelectric MEMS microphone that can improve the signal-to-noise ratio.

Summary of the invention

technical problem

The purpose of the utility model is to provide a piezoelectric MEMS microphone with a high signal-to-noise ratio.

The solution to the problem

Technical solutions

The technical scheme of the utility model is as follows:

A piezoelectric MEMS microphone has a substrate with a back cavity, a diaphragm suspended in the back cavity, and an elastic support connected between the diaphragm and the substrate. The diaphragm extends along the diaphragm. A first piezoelectric diaphragm and a second piezoelectric diaphragm are respectively provided on both sides of the vibration direction, and the second piezoelectric diaphragm is connected in parallel with the first piezoelectric diaphragm.

Further, the first piezoelectric diaphragm and the second piezoelectric diaphragm have the same structure.

Further, the first piezoelectric diaphragm and the second piezoelectric diaphragm are directly opposite and symmetrically arranged on both sides of the vibrating diaphragm.

Further, the first piezoelectric diaphragm is circular, rectangular or square.

Further, the first piezoelectric membrane structure includes two electrode layers and a piezoelectric layer sandwiched between the two electrode layers.

Further, the elastic support member extends from the edge of the diaphragm toward the base, and the base recesses corresponding to the elastic support member to form an escape portion, and the elastic support member is accommodated in the escape portion.

Further, the elastic support includes an extension arm extending from the edge of the diaphragm toward the base and spaced apart from the base, and an end of the extension arm that is bent and extended away from the diaphragm and connected to the base. The connecting wall of the substrate connection.

Further, the connecting arms are respectively formed on opposite sides of the extension arm.

Further, each of the connecting arms includes at least one connecting bar parallel to the extension arm.

Further, at least two of the elastic support members are symmetrically connected to the outer circumference of the diaphragm.

The beneficial effects of the invention

Beneficial effect

The beneficial effect of the utility model is that the design mainly prepares the second piezoelectric diaphragm corresponding to the first piezoelectric diaphragm under the diaphragm, and the second piezoelectric diaphragm is connected in parallel with the first piezoelectric diaphragm. The design method will slightly reduce the sensitivity, but because the capacitance is doubled after the parallel connection, the noise will be greatly reduced, so the overall signal-to-noise ratio (SNR) will be considerably improved.

Brief description of the drawings

Description of the drawings

Figure 1 is a schematic diagram of the structure of the piezoelectric MEMS microphone provided by the utility model;

Figure 2 is a cross-sectional view taken along line A-A of Figure 1;

Figure 3 is a partial enlarged view of B in Figure 1;

Fig. 4 is a partial enlarged view of C in Fig. 1;

Fig. 5 is another embodiment of the piezoelectric MEMS microphone provided by the present invention.

In the picture:

100. Piezoelectric MEMS microphone; 1. substrate; 101, back cavity; 2. diaphragm; 3. first piezoelectric diaphragm; 4. second piezoelectric diaphragm; 31, electrode layer; 32, piezoelectric layer; 5. Elastic support; 51, extension arm; 52, connecting arm; 521, connecting strip.

Invention embodiment

Detailed ways

The present utility model will be further explained below in conjunction with the drawings and embodiments.

1 and 2, a piezoelectric MEMS microphone 100 is provided, which has a substrate with a back cavity 101, a diaphragm 2 suspended in the back cavity 101, and is connected between the diaphragm 2 and the substrate The elastic support 5 of the diaphragm 2 is provided with a first piezoelectric diaphragm 3 and a second piezoelectric diaphragm 4 on both sides of the diaphragm 2 along the vibration direction of the diaphragm 2, and the second piezoelectric diaphragm 4 is connected in parallel with the first piezoelectric diaphragm 3.

In this design, the second piezoelectric diaphragm 4 opposite to the first piezoelectric diaphragm 3 is mainly prepared under the diaphragm 2, and the second piezoelectric diaphragm 4 is connected in parallel with the first piezoelectric diaphragm 3. This design method will The sensitivity is slightly reduced, but the noise will be greatly reduced due to the increase of the capacitance after the parallel connection, so the overall signal-to-noise ratio (SNR) will be considerably improved.

When the diaphragm 2 vibrates under the action of sound waves, the distance between the diaphragm 2 and the substrate 1 will change, and the first piezoelectric diaphragm 3 and the second piezoelectric diaphragm 4 will then generate electric charge output, thereby transferring the sound wave The signal is converted into an electrical signal to realize the corresponding function of the microphone.

Preferably, the first piezoelectric diaphragm 3 and the second piezoelectric diaphragm 4 have the same structure. Due to the same structure of the two, the capacitance is doubled after parallel connection, and the noise will be greatly reduced, so the overall signal-to-noise ratio (SNR) will be considerably improved.

Preferably, the first piezoelectric diaphragm 3 and the second piezoelectric diaphragm 4 are directly opposite and symmetrically arranged on both sides of the diaphragm 2. Further reduce noise and improve signal-to-noise ratio (SNR).

Preferably, the first piezoelectric diaphragm 3 is circular, rectangular or square. Please refer to FIG. 1, the first piezoelectric diaphragm 3 is in the shape of a strip and is arranged in two, and the two first piezoelectric diaphragms 3 are center-symmetrical and enclose a rectangle.

Please refer to FIG. 4, the structure of the first piezoelectric film 3 preferably includes two electrode layers 31 and a piezoelectric layer 32 sandwiched between the two electrode layers 31. The two electrode layers 31 are one positive and one negative, so as to be connected to the piezoelectric layer 32.

3, preferably the elastic support member 5 extends from the edge of the diaphragm 2 toward the direction of the base, the base 1 corresponds to the elastic support member 5 recessed to form an escape portion, the elastic support member 5 is accommodated in In the avoidance part, in this way, the compactness and consistency of the structure are good.

Preferably, the elastic support member 5 includes an extension arm 51 extending from the edge of the diaphragm 2 toward the base and spaced apart from the base, and an end bent and extended from the extension arm 51 away from the diaphragm 2. And a connecting wall connected to the substrate. The connecting arm 52 has elasticity, so that the diaphragm 2 can vibrate relative to the base.

Preferably, the connecting arms 52 are formed on opposite sides of the extension arm 51, and the connecting arms 52 are symmetrically located on both sides of the end of the extension arm 51. In this way, the structure is compact and consistent. It is preferable that the two connecting arms 52 are in one. In a straight line.

Preferably, each of the connecting arms 52 includes at least one connecting bar 521 parallel to the extension arm 51. The connecting strips 521 are formed in an arcuate shape or a plurality of arcuate shapes, and the displacement between adjacent connecting strips 521 provides flexibility.

Preferably, at least two of the elastic support members 5 are symmetrically connected to the outer periphery of the diaphragm 2 so that the diaphragm 2 is balanced in force. Further, it is preferable that the diaphragm 2 has a rectangular shape, and each of the four corners of the diaphragm 2 is provided with an elastic support member. 5.

Referring to FIG. 5, in other embodiments, the piezoelectric MENS microphone is not limited to a single model, and can also be made into an array structure of 2x2, 3x3, 4x4 or more.

The above are only the embodiments of the present utility model. It should be pointed out here that for those of ordinary skill in the art, improvements can be made without departing from the inventive concept of the present utility model, but these all belong to The scope of protection of the utility model.

Claims

A piezoelectric MEMS microphone, characterized in that a substrate with a back cavity, a diaphragm suspended in the back cavity, and an elastic support connected between the diaphragm and the substrate, the diaphragm along A first piezoelectric diaphragm and a second piezoelectric diaphragm are respectively provided on both sides of the vibration direction of the diaphragm, and the second piezoelectric diaphragm is connected in parallel with the first piezoelectric diaphragm.
The piezoelectric MEMS microphone according to claim 1, wherein the first piezoelectric diaphragm and the second piezoelectric diaphragm have the same structure.
The piezoelectric MEMS microphone according to claim 1, wherein the first piezoelectric diaphragm and the second piezoelectric diaphragm are directly opposite and symmetrically arranged on both sides of the vibrating diaphragm.
The piezoelectric MEMS microphone according to claim 2, wherein the first piezoelectric diaphragm is circular, rectangular or square.
The piezoelectric MEMS microphone according to claim 1, wherein the first piezoelectric diaphragm structure includes two electrode layers and a piezoelectric layer sandwiched between the two electrode layers.
The piezoelectric MEMS microphone according to claim 1, wherein the elastic support extends from the edge of the diaphragm toward the base, and the base is recessed to form an escape portion corresponding to the elastic support, and The elastic support is contained in the avoiding part.
The piezoelectric MEMS microphone according to claim 6, wherein the elastic support includes an extension arm extending from the edge of the diaphragm toward the substrate and spaced apart from the substrate, and an extension arm from the extension arm. A connecting wall that is bent and extended at one end away from the diaphragm and connected to the base.
8. The piezoelectric MEMS microphone according to claim 7, wherein the connecting arms are respectively formed on opposite sides of the extension arm.
8. The piezoelectric MEMS microphone according to claim 7, wherein each of the connecting arms includes at least one connecting bar parallel to the extension arm.
The piezoelectric MEMS microphone according to claim 1, wherein at least two of the elastic support members are symmetrically connected to the outer periphery of the diaphragm.