WO2022110349A1

WO2022110349A1 - Piezoelectric microphone and method for manufacturing same

Info

Publication number: WO2022110349A1
Application number: PCT/CN2020/136636
Authority: WO
Inventors: 石正雨; 童贝
Original assignee: 瑞声声学科技(深圳)有限公司
Priority date: 2020-11-30
Filing date: 2020-12-16
Publication date: 2022-06-02
Also published as: CN112584289B; CN112584289A

Abstract

Provided is a piezoelectric microphone. The piezoelectric microphone comprises a base having a back cavity, and a piezoelectric cantilever beam vibrating diaphragm fixed above the base, wherein the piezoelectric cantilever beam vibrating diaphragm at least comprises a first vibrating sub-diaphragm and a second vibrating sub-diaphragm; one end of each vibrating sub-diaphragm is fixed to the base, so as to form a fixed end, and the other end thereof is suspended above the back cavity, so as to form a movable end that is connected to the fixed end; and the width of the movable end is not less than the width of the fixed end. The piezoelectric microphone further comprises an elastic telescopic member, wherein one end of the elastic telescopic member is connected to the movable end of the first vibrating sub-diaphragm, and the other end thereof is connected to the second vibrating sub-diaphragm and/or the base. In the present application, the width of a movable end of a cantilever beam is not less than the width of a fixed end, such that a greater moment will be generated under the action of a sound pressure, thereby improving the signal-to-noise ratio of the microphone.

Description

Piezoelectric microphone and method of making the same

technical field

The present application relates to a piezoelectric microphone, and in particular, to a piezoelectric microphone with a diaphragm having a large torque.

Background technique

There are many types of microphones, including moving coil, condenser, aluminum ribbon, carbon, etc. In mobile applications, electret (ECM) condenser microphones and microelectromechanical (MEMS) microphones are the most common. Compared with electret microphones, MEMS microphones are smaller in size and have stronger resistance to heat, vibration and radio frequency interference. Additionally, MEMS microphones can be produced using a fully automated surface mount (SMT) process, whereas most electret microphones require hand soldering.

In the MEMS microphone, it is divided into two types: capacitive and piezoelectric. Piezoelectric versus capacitive update. The main advantage of piezoelectric technology is that it is robust and unaffected by the environment, while capacitive technology suffers from performance degradation over time: in condenser microphones, if there is particulate contamination between the diaphragm and the backplate, the performance of the microphone will be reduced. Change. Another advantage of piezoelectric microphones is that the signal-to-noise ratio (SNR) is higher. Currently, according to known methods, a signal-to-noise ratio of more than 75dB can be obtained, and in theory, it can even exceed 80dB.

technical problem

However, the width of the free end of the piezoelectric microphone cantilever beam of the existing structure is smaller than that of the fixed end, the torque generated under the action of sound pressure is low, and the signal-to-noise ratio is low, and the free end warps under the residual stress, resulting in a large gap, which affects Microphone low frequency performance.

technical solutions

The purpose of this application is to provide a piezoelectric microphone. In one aspect of the technical solution of the application, it includes a base with a back cavity and a piezoelectric cantilever diaphragm fixed on the base; the piezoelectric cantilever vibrator The membrane at least includes a first sub-diaphragm and a second sub-diaphragm, one end of each sub-diaphragm is fixed with the base to form a fixed end, and the other end is suspended above the back cavity to form a movable end connected to the fixed end, and the width of the movable end is not less than Regarding the width of the fixed end, the piezoelectric microphone further includes an elastic elastic member, one end of the elastic elastic member is connected to the movable end of the first sub-diaphragm, and the other end is connected to the second sub-diaphragm and/or the base.

Preferably, the back cavity is in the shape of a square, and the elastic elastic member connecting the first sub-diaphragm and the second sub-diaphragm is located on the central axis of the square and is parallel to the fixed ends of the first and second sub-diaphragms.

Preferably, the back cavity is in the shape of an octagon, and the elastic expansion member connecting the first sub-diaphragm and the second sub-diaphragm is located on the central axis of the octagon, and is connected to the fixed ends of the first sub-diaphragm and the second sub-diaphragm. parallel.

Preferably, the back cavity is hexagonal, and the elastic expansion member connecting the first sub-diaphragm and the second sub-diaphragm is located on the central axis of the hexagon, and is connected to the fixed ends of the first sub-diaphragm and the second sub-diaphragm. parallel.

Preferably, the back cavity is in the shape of a cross, and the elastic expansion member connecting the first sub-diaphragm and the second sub-diaphragm is located on the central axis of the cross and is parallel to the fixed ends of the first and second sub-diaphragms.

Preferably, the elastic elastic member is a flexible spring structure.

Preferably, the elastic elastic member is a hollow pattern on the sub-diaphragm.

Preferably, the hollow pattern includes a zigzag groove, a swastika groove or a rhombus groove

Another aspect of the present application provides a method for making a piezoelectric microphone, comprising the following steps:

S1: deposit a layer of piezoelectric material on the substrate, so that the piezoelectric material is fixed on the substrate material;

S2: Divide the first sub-diaphragm and the second sub-diaphragm on the piezoelectric material, and fix one end of each sub-diaphragm with the base to form a fixed end, and the other end to form a free movable end, and the width of the movable end is not less than the fixed end the width of the end;

S3: generating an elastic elastic member, one end of the elastic elastic member is connected to the movable end of the first sub-diaphragm, and the other end is connected to the second sub-diaphragm and/or the substrate;

S4: A back cavity with a polygonal shape is etched on the substrate. Preferably, in the step S3, the elastic elastic member is a hollow pattern on the sub-diaphragm.

beneficial effect

The beneficial technical effects that can be achieved by the technical solution of the present application include: the width of the movable end of the cantilever beam in the structure of the piezoelectric microphone is not less than the width of the fixed end, and a larger torque will be generated under the action of sound pressure, thereby improving the signal-to-noise ratio of the microphone; A flexible spring structure is arranged on the free moving edge of the cantilever beam, so that when the cantilever beam is warped, the spring deforms with the cantilever beam, thereby avoiding the generation of gaps and improving the low-frequency performance of the microphone.

Description of drawings

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

FIG. 1 is a top view of a specific embodiment of the present application and an enlarged view of an elastic telescopic element;

FIG. 2 is a top view of a plurality of specific embodiments of the present application;

3 is a perspective view of a specific embodiment of the present application;

Fig. 4(a) is a schematic diagram of the prior art without elastic elastic members; Fig. 4(b) is a functional schematic diagram of the elastic elastic members in the present application and an enlarged view thereof.

Embodiments of the present invention

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application. 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," "left," "right," and similar expressions are used herein for illustrative purposes only.

Referring to FIGS. 1 and 3 , the present application provides a piezoelectric microphone 100 , which includes a substrate 10 having a back cavity 11 , and a piezoelectric cantilever diaphragm 20 fixed above the substrate 10 . The piezoelectric cantilever beam diaphragm 20 includes a pair of first sub-diaphragms 21 and second sub-diaphragms 22 arranged oppositely. The pair of sub-diaphragms of the piezoelectric cantilever beam diaphragm 20 will deform under the action of external sound pressure. , and the piezoelectric effect occurs to generate electrical signal output. The back cavity 11 is a cavity formed by the substrate 10 and the piezoelectric cantilever beam diaphragm 20. Due to the existence of the back cavity 11, when the same sound intensity acts on the piezoelectric cantilever beam diaphragm 20, the piezoelectric cantilever beam diaphragm 20 will vibrate. The displacement is greatly increased, and thus the increased strain produces more charge. The first sub-diaphragm 21 and the second sub-diaphragm 22 have the same shape, each sub-diaphragm has at least one fixed end 211, 221 fixed on the base 10, and at least one of the sub-diaphragms is elastically connected to the other sub-diaphragm. The movable ends 212 and 222 of the telescopic piece 30 are connected. The elastic elastic member 30 and the fixed ends connecting the first sub-diaphragm 21 and the second sub-diaphragm 22 with the base 10 form certain constraints on the first sub-diaphragm 21 and the second sub-diaphragm 22, so that the first sub-diaphragm 21 and the second sub-diaphragm 22 are bound to a certain extent. The membrane 21 and the second sub-diaphragm 22 are suspended above the back cavity 11 of the substrate 10, and make the two first sub-diaphragms 21 and the second sub-diaphragm 22 on the same plane as much as possible, so as to reduce the damage caused by the two diaphragms. The signal-to-noise ratio decreases due to the deformation of the first sub-diaphragm 21 and the second sub-diaphragm 22 . In addition, in order to further improve the signal-to-noise ratio, the lengths of the movable ends 212 and 222 of the sub-diaphragm are not less than the lengths of the fixed ends 211 and 221 .

The material of the substrate 10 may be a material such as silicon that can be processed by an etching process, so that the back cavity 11 can be etched on the base material of the substrate 10 . The material of the piezoelectric cantilever diaphragm 20 is a ceramic material capable of generating piezoelectric effect, such as AlN, perovskite oxide and the like. The material of the piezoelectric cantilever diaphragm 20 may be deposited on the base by methods such as physical vapor deposition.

At this time, the piezoelectric cantilever beam diaphragm 20 has only two first sub-diaphragms 21 and the fixed ends 211 and 221 of the second sub-diaphragm 22 connected to the base 10. In order to further improve the piezoelectric cantilever beam diaphragm 20 In a preferred embodiment, the piezoelectric cantilever beam diaphragm 20 is adjacent to the base 10 except for the fixed ends 211 and 221 of the first sub-diaphragm 21 and the second sub-diaphragm 22, The connection is also made using elastic elastic members 30 . In this preferred embodiment, all sides of the piezoelectric cantilever diaphragm 20 are connected to the base 10, which can further improve the stability.

In one embodiment, the piezoelectric cantilever beam vibrating film 20 includes at least three-layer structures, which respectively include a first electrode sheet, a piezoelectric diaphragm, and a second electrode sheet that are sequentially stacked along the vibration direction, and the first electrode sheet is provided with On the side of the piezoelectric cantilever diaphragm 20 close to the back cavity 11 . More specifically, the piezoelectric cantilever diaphragm 20 may also have a five-layer structure or a multi-layer structure.

In a specific embodiment, as can be seen from FIG. 4( b ), the elastic elastic member 30 is a soft spring structure, which connects the base 10 and the piezoelectric cantilever beam diaphragm 20 and connects the two first sub-diaphragms 21 , When the second sub-diaphragm 22 is used, when the cantilever beam is warped, the spring and the piezoelectric cantilever beam diaphragm 20 can be deformed together, thereby avoiding the generation of the gap as shown in FIG. 4(a), thereby improving the low frequency of the microphone. performance.

In a specific embodiment, as can be seen from the enlarged part in FIG. 1 , the soft spring structure as the elastic elastic member 30 is a hollow pattern etched on the first sub-diaphragm 21 and the second sub-diaphragm 22 . Specifically, the hollow pattern may be a zigzag groove, a swastika groove or a rhombus groove. Specifically, the above-mentioned hollow pattern is etched on the piezoelectric cantilever beam vibrating film 20 deposited on the base by a method such as physical vapor deposition by photolithography.

In a variant embodiment, the required movable ends 212 , 222 and the part where the piezoelectric cantilever beam diaphragm 20 is connected to the base 10 can be directly etched on a whole piece of the deposited piezoelectric cantilever beam diaphragm 20 . .

The present application also provides a method for making a piezoelectric microphone, comprising the following steps:

S2: Divide the first sub-diaphragm 21 and the second sub-diaphragm 22 on the piezoelectric material, and fix one end of each sub-diaphragm with the base 10 to form a fixed end, and the other end to form a free movable end. The width of the end is not less than the width of the fixed end.

On the first sub-diaphragm 21 and the second sub-diaphragm 22, through the flexible spring structure 30, the sides where the first sub-diaphragm 21 and the second sub-diaphragm 22 are connected to each other are set as the movable ends 212 and 222, which are connected with each other. The movable ends 212 and 222 are parallel and fixed on the base 10 as fixed ends.

S3 : generating an elastic elastic member 30 , one end of the elastic elastic member 30 is connected to the movable end 212 of the first sub-diaphragm 21 , and the other end is connected to the second sub-diaphragm 22 and/or the base 10 .

S4: The back cavity 11 having a polygonal shape is etched on the base material.

The shape of the back cavity 11 determines the shape of the piezoelectric cantilever beam diaphragm 20 covering the substrate 10 . Therefore, it is necessary to ensure that the length of the movable ends 212 and 222 of the sub-diaphragms 21 and 22 is not less than the length of the fixed ends 211 and 221 .

In an optional embodiment, in step S3, the elastic stretchable member is a hollow pattern on the piezoelectric cantilever beam diaphragm.

Various embodiments of the piezoelectric microphone 100 with different shapes of the back cavity 11 are listed below with reference to FIG. 2 . It should be noted that the following specific embodiments are only for the purpose of specifically illustrating the structure of the piezoelectric microphone 100 of the present application. , and does not constitute any limitation to this application.

Example 1

Referring to FIG. 2( a ), in a specific embodiment, a piezoelectric cantilever beam diaphragm 20 formed by a pair of first sub-diaphragms 21 and second sub-diaphragms 22 having the same shape is fixed and suspended on the substrate 10 with The octagonal shape is above the back cavity 11 to receive the external sound pressure and convert it into an electrical signal. Specifically, the movable ends 212 and 222 of the first sub-diaphragm 21 and the second sub-diaphragm 22 are connected to each other along the central axis of the octagon of the back cavity 11 through the elastic elastic member 30, so that the first sub-diaphragm 21, The second sub-diaphragm 22 is connected to form the piezoelectric cantilever beam diaphragm 20, and the fixed ends 211 and 221 of the first sub-diaphragm 21 and the second sub-diaphragm 22 are located on two opposite sides of the eight sides parallel to the central axis. on each side, and is fixedly connected with the base 10. In this embodiment, the lengths of the movable ends 212 and 222 of the first sub-diaphragm 21 and the second sub-diaphragm 22 are greater than the lengths of the fixed ends 211 and 221, which makes the piezoelectric cantilever beam diaphragm 20 play a role in the sound pressure. There is a larger torque under the lower, which can improve the signal-to-noise ratio.

Example 2

Referring to FIG. 2( b ), in a specific embodiment, a piezoelectric cantilever beam vibrating membrane 20 formed by a pair of the first sub-diaphragm 21 and the second sub-diaphragm 22 having the same shape is fixed and suspended on the substrate 10 having the same shape. Above the back cavity 11 in the shape of a hexagon to receive the external sound pressure and convert it into an electrical signal. Specifically, the movable ends 212 and 222 of the first sub-diaphragm 21 and the second sub-diaphragm 22 are connected to each other along the central axis of the hexagon by the elastic elastic member 30 , so that the first sub-diaphragm 21 and the second sub-diaphragm 22 are connected to each other along the central axis of the hexagon. The diaphragms 22 are connected to form the piezoelectric cantilever beam diaphragm 20, and the fixed ends 211 and 221 of the first sub-diaphragm 21 and the second sub-diaphragm 22 are located on two sides of the six sides that are parallel to and opposite to the central axis, and fixedly connected with the base 10 . In this embodiment, the lengths of the movable ends 212 and 222 of the first sub-diaphragm 21 and the second sub-diaphragm 22 are not less than the lengths of the fixed ends 211 and 221 , which makes the piezoelectric cantilever beam diaphragm 20 operate under the sound pressure. There is a larger moment under the action, which can improve the signal-to-noise ratio.

Example 3

Referring to FIG. 2( c ), in a specific embodiment, a piezoelectric cantilever beam vibrating membrane 20 formed by a pair of the first sub-diaphragm 21 and the second sub-diaphragm 22 having the same shape is fixed and suspended on the substrate 10 having the same shape. Above the back cavity 11 in the shape of a cross to receive the external sound pressure and convert it into an electrical signal. Specifically, the movable ends 212 and 222 of the first sub-diaphragm 21 and the second sub-diaphragm 22 are connected to each other along the central axis of the cross through the elastic elastic member 30 , so that the first sub-diaphragm 21 and the second sub-diaphragm 22 are connected to each other by the elastic expansion member 30 . 22 is connected to form a piezoelectric cantilever beam diaphragm 20, and the fixed ends 211 and 221 of the first sub-diaphragm 21 and the second sub-diaphragm 22 are located on two sides parallel to and opposite to the central axis of the cross, and are connected to the base. 10 are fixedly connected. It can be seen that in this embodiment, the lengths of the movable ends 212 and 222 of the first sub-diaphragm 21 and the second sub-diaphragm 22 are not less than the lengths of the fixed ends 211 and 221, which makes the piezoelectric cantilever beam diaphragm 20 in the sound Under the action of pressure, there is a larger moment, which can improve the signal-to-noise ratio.

Example 4

Referring to FIG. 2( d ), in a specific embodiment, a piezoelectric cantilever beam vibrating membrane 20 formed by a pair of the first sub-diaphragm 21 and the second sub-diaphragm 22 having the same shape is fixed and suspended on the substrate 10 having the same shape. Above the square-shaped back cavity 11 to receive the external sound pressure and convert it into an electrical signal. Specifically, the movable ends 212 and 222 of the first sub-diaphragm 21 and the second sub-diaphragm 22 are connected to each other along the central axis of the square by the elastic expansion member 30 , so that the first sub-diaphragm 21 and the second sub-diaphragm 22 The piezoelectric cantilever beam diaphragm 20 is formed by connection, and the fixed ends 211 and 221 of the first sub-diaphragm 21 and the second sub-diaphragm 22 are located on the two sides parallel to and opposite to the central axis of the square, and are fixed to the base 10 connected.

In this embodiment, the part of the piezoelectric cantilever beam diaphragm 20 adjacent to the base 10 except the fixed ends 211 and 221 of the first sub-diaphragm 21 and the second sub-diaphragm 22 also uses an elastic elastic member 30 to connect.

In this embodiment, the lengths of the movable ends 212 and 222 of the first sub-diaphragm 21 and the second sub-diaphragm 22 are greater than the lengths of the fixed ends 211 and 221, which makes the piezoelectric cantilever beam diaphragm 20 play a role in the sound pressure. There is a larger torque under the lower, which can improve the signal-to-noise ratio.

The technical features of the above embodiments can be combined arbitrarily. For the sake of brief description, all possible combinations of the technical features in the above embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, the It is considered to be the range described in this specification. Finally, it should also be noted that in this document, relational terms such as first and second are used only to distinguish one entity or operation from another, and do not necessarily require or imply these entities or that there is any such actual relationship or sequence between operations. Moreover, the terms "comprising", "comprising" or any other variation thereof are intended to encompass a non-exclusive inclusion such that a process, method, article or device comprising a list of elements includes not only those elements, but also includes not explicitly listed or other elements inherent to such a process, method, article or apparatus. Without further limitation, an element qualified by the phrase "comprising a..." does not preclude the presence of additional identical elements in a process, method, article or apparatus that includes the element.

The above examples 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 of the present application. It should be noted that, for those skilled 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 present application should be determined by the appended claims.

Claims

1. a piezoelectric microphone, it comprises a substrate with a back cavity and a piezoelectric cantilever beam vibrating film fixed above the substrate; the piezoelectric cantilever beam vibrating film at least comprises a first sub-diaphragm and a second sub-diaphragm. Diaphragm, one end of each sub-diaphragm is fixed with the base to form a fixed end, and the other end is suspended above the back cavity to form a movable end connected to the fixed end, characterized in that the width of the movable end is not less than The width of the fixed end, the piezoelectric microphone further includes an elastic elastic member, one end of the elastic elastic member is connected to the movable end of the first sub-diaphragm, and the other end is connected to the second sub-diaphragm and/or the base.

2. piezoelectric microphone according to claim 1, is characterized in that:

The back cavity is in the shape of a square, and the elastic elastic member connecting the first sub-diaphragm and the second sub-diaphragm is located at the center axis of the square, and is connected with the first sub-diaphragm and the second sub-diaphragm. The fixed ends of the two sub-diaphragms are parallel.

3. Piezoelectric microphone according to claim 1, is characterized in that:

The back cavity is in the shape of an octagon, and the elastic telescopic end connecting the first sub-diaphragm and the second sub-diaphragm is located at the center axis of the octagon, and is connected to the first sub-diaphragm. parallel to the fixed end of the second sub-diaphragm.

4. piezoelectric microphone according to claim 1, is characterized in that:

The back cavity is in the shape of a hexagon, and the elastic telescopic end connecting the first sub-diaphragm and the second sub-diaphragm is located at the central axis of the hexagon, and is connected to the first sub-diaphragm. parallel to the fixed end of the second sub-diaphragm.

5. The piezoelectric microphone according to claim 1, wherein:

The back cavity is in the shape of a cross, and the elastic telescopic end connecting the first sub-diaphragm and the second sub-diaphragm is located at the central axis of the cross, and is connected with the first sub-diaphragm and the second sub-diaphragm. The fixed ends of the second sub-diaphragm are parallel.

6. The piezoelectric microphone according to any one of claims 1 to 5, wherein the elastic elastic member is a flexible spring structure.

7. The piezoelectric microphone according to any one of claims 1 to 5, wherein the elastic elastic member is a hollow pattern on the piezoelectric cantilever beam diaphragm.

8. The piezoelectric microphone according to claim 7, wherein the hollow pattern comprises a zigzag groove, a swastika groove or a rhombus groove.

9. A method of making a piezoelectric microphone, characterized in that:

Include the following steps:

S1: depositing a layer of piezoelectric material on the substrate, so that the piezoelectric material is fixed on the substrate material;

S2: Divide the first sub-diaphragm and the second sub-diaphragm on the piezoelectric material, and fix one end of each sub-diaphragm with the base to form a fixed end, and the other end to form a free movable end, The width of the movable end is not less than the width of the fixed end;

S3: generating an elastic elastic member, one end of the elastic elastic member is connected to the movable end of the first sub-diaphragm, and the other end is connected to the second sub-diaphragm and/or the base;

S4: Etch a back cavity with a polygonal shape on the substrate.

10. preparation method according to claim 9, is characterized in that:

In the step S3, the elastic elastic member is a hollow pattern on the diaphragm of the piezoelectric cantilever beam.