CN109495829B

CN109495829B - Piezoelectric MEMS microphone

Info

Publication number: CN109495829B
Application number: CN201811650270.1A
Authority: CN
Inventors: 段炼; 张睿
Original assignee: AAC Acoustic Technologies Shenzhen Co Ltd
Current assignee: AAC Technologies Holdings Shenzhen Co Ltd
Priority date: 2018-12-31
Filing date: 2018-12-31
Publication date: 2021-12-03
Anticipated expiration: 2038-12-31
Also published as: CN109495829A

Abstract

The invention provides a piezoelectric type MEMS microphone, which comprises a substrate with a back cavity and a piezoelectric diaphragm arranged on the substrate, wherein the piezoelectric diaphragm comprises a plurality of diaphragms, each diaphragm comprises a fixed end connected with the substrate and a free end connected with the fixed end and suspended above the back cavity, two adjacent diaphragms are arranged at intervals or contacted with each other, the piezoelectric type EMES microphone also comprises a constraint structure positioned in the central area of the piezoelectric diaphragm, and the free ends of at least two diaphragms are connected with the constraint structure. Compared with the prior art, the piezoelectric MEMS microphone provided by the invention has the advantages that the free ends of the diaphragms are limited in the same plane by arranging the constraint structure, the uniformity of the product performance is improved, and the drop resistance is better.

Description

Piezoelectric MEMS microphone

[ technical field ] A method for producing a semiconductor device

The invention relates to the technical field of acoustoelectric technology, in particular to a piezoelectric type MEMS microphone.

[ background of the invention ]

In recent years, more and more mobile devices have started to use Micro Electro Mechanical Systems (MEMS) instead of the original electret microphone. As the use environment of the mobile device is variable, this puts higher demands on the reliability of the MEMS microphone.

At present, MEMS microphones are mainly classified into capacitive MEMS microphones and piezoelectric MEMS microphones. The piezoelectric MEMS microphone can overcome the defects of the traditional capacitance type MEMS microphone, has better performance in the aspects of dust prevention, water prevention and the like, and has wider application field. Different from the diaphragm structure of a condenser microphone, as shown in fig. 1, the diaphragm of a piezoelectric MEMS microphone is composed of a plurality of diaphragms 21, one end of each diaphragm 21 is connected to the substrate 1, and the other end of each diaphragm 21 is of a cantilever structure to avoid the influence of residual stress in the process on the acoustic performance. However, under the action of residual stress, the free end of the diaphragm 21 deforms, and due to uneven stress distribution of the whole diaphragm 2 in the processing process, the diaphragms 21 of different pressure sensor chips deform differently, and the difference in the cantilever beam structure further affects the performance of the microphone, so that the difference in the sensitivity, the drop resistance and the like of the microphone is large, and the actual requirements cannot be met.

As shown in fig. 2, different diaphragms 21 have slightly different deformations due to different residual stresses, and gaps between the diaphragms 21 may also change, which may further cause different acoustic resistances of different pressure sensing chips, thereby affecting different performance differences of different piezoelectric MEMS microphones.

Therefore, it is necessary to improve the cantilever structure of the diaphragm to reduce the performance difference caused by the deformation caused by the processing.

[ summary of the invention ]

The invention provides a piezoelectric MEMS microphone with a novel structure, and aims to solve the technical problem that the sensitivity and the drop resistance of the microphone are affected due to the fact that the deformation of the free end of a piezoelectric MEMS microphone diaphragm is not uniform in the processing process in the related art.

The utility model provides a piezoelectric type MEMS microphone, is in including the basement that has the back of the body chamber and setting piezoelectric diaphragm on the basement, piezoelectric diaphragm includes a plurality of diaphragms, each the diaphragm include with stiff end that the basement is connected and with the stiff end is connected and is suspended in the free end of back of the body chamber top, adjacent two the interval sets up or contacts between the diaphragm, piezoelectric type EMES microphone is still including being located the restraint structure of piezoelectric diaphragm central zone, and at least two the free end of diaphragm with restraint structural connection.

Preferably, the constraint structure and the piezoelectric diaphragm are integrally formed.

Preferably, the constraint structure and the piezoelectric diaphragm are in the same plane.

Preferably, the connection of the free end to the constraint structure includes at least one of a rigid connection or a flexible connection.

Preferably, the constraining structure includes a body portion and a plurality of apertures disposed through the body portion, the free end being connected to the body portion.

Preferably, the constraint structure is a symmetrical structure or an asymmetrical structure.

Preferably, the plurality of diaphragms are identical in size and shape, and cooperate with the constraint structure to enclose a circular structure.

Preferably, a plurality of diaphragms and the constraint structure are matched to enclose a regular polygon structure.

Preferably, the cross-sectional area of the back cavity is smaller than the cross-sectional area of the piezoelectric diaphragm, and the cross-sectional area of the constraint structure is smaller than the cross-sectional area of the back cavity.

Compared with the prior art, the free ends of the diaphragms are limited in the same plane by arranging the constraint structure, when the diaphragms are released from the substrate, the deformation degree of the diaphragms can be limited by the constraint structure, so that the gaps between the two adjacent diaphragms are consistent, the structural difference caused by deformation of different pressure sensor chips is reduced, and the uniformity of product performance is improved; meanwhile, the constraint structure is favorable for improving the anti-falling performance of the microphone.

[ description of the drawings ]

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without inventive efforts, wherein:

fig. 1 is a schematic plan view of a piezoelectric MEMS microphone in the related art;

FIG. 2 is a cross-sectional view of the piezoelectric MEMS microphone of FIG. 1;

FIG. 3 is a schematic plan view of a piezoelectric MEMS microphone according to a first embodiment of the present invention;

FIG. 4 is a cross-sectional view of the piezoelectric MEMS microphone of FIG. 3 taken along line A-A;

FIG. 5 is a schematic plan view of a piezoelectric MEMS microphone according to a second embodiment of the invention.

[ detailed description ] embodiments

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example one

Referring to fig. 3 and 4, the present invention provides a piezoelectric MEMS microphone 100, which includes a substrate 1 having a back cavity 10, a piezoelectric diaphragm 2 disposed on the substrate 1, and a constraint structure 3 located in a central region of the piezoelectric diaphragm 2. The substrate 1 is made of a semiconductor material, such as silicon, and the back cavity 10 extends longitudinally through the substrate 1, wherein the back cavity 10 may be formed by a bulk silicon process or dry etching. The cross-sectional area of the back cavity 10 is smaller than that of the piezoelectric diaphragm 2, and the cross-sectional area of the constraint structure 3 is smaller than that of the back cavity 10.

The piezoelectric diaphragm 2 is circular as a whole, the periphery of the piezoelectric diaphragm is fixed with the substrate 1, and the other parts of the piezoelectric diaphragm are suspended above the back cavity 10 of the substrate 1. The piezoelectric diaphragm 2 includes a plurality of diaphragms 21. Two adjacent diaphragms 21 are arranged at intervals or are in contact with each other. Wherein each of the diaphragms 21 comprises a fixed end 211 connected with the substrate 1 and a free end 212 connected with the fixed end 211 and suspended above the back cavity 10. The free end 212 of the diaphragm 21 is deformed under the action of external sound pressure to sense a sound pressure signal. At least two of the free ends 212 of the diaphragms 21 are connected to the constraining structure 3, and in this embodiment, the free end 212 of each diaphragm 21 is connected to the constraining structure 3.

By connecting the constraining structure 3 to the free ends 212 of the diaphragms 21, the free ends 212 of a plurality of diaphragms 21 can be confined in the same plane. When the diaphragm 21 is released from the substrate 1, the free end 212 is connected and restrained by the restraining structure 3, so that the deformation degree of warping, curling and the like of the diaphragm 21 under the action of residual stress is limited, the structural difference of different pressure sensor chips caused by deformation is reduced, and the uniformity of product performance is further improved.

The constraint structure 3 is a circular net structure, and includes a body 31 and a plurality of openings 32 disposed through the body 31. The shape of the plurality of openings 32 may be the same or different, and the additional provision of the openings 32 is more advantageous for releasing residual stress. The free end 212 of the diaphragm 21 is connected to the body portion 31. The free end 212 and the constraining structure 3 can be connected rigidly or flexibly or a combination of both. Alternatively, the constraint structure 3 may be a symmetrical structure or an asymmetrical structure.

The plurality of diaphragms 21 may have the same size and shape, or may have different sizes and shapes, that is, the piezoelectric diaphragm 2 may have a symmetrical structure or an asymmetrical structure. When the plurality of diaphragms 21 are the same in size and shape, the resonant frequency of each diaphragm 21 is the same, that is, only one resonant frequency of the whole piezoelectric diaphragm 2 is provided, and the bandwidth of the piezoelectric diaphragm is narrow; when the sizes and shapes of the plurality of diaphragms 21 are different, the resonant frequency of each diaphragm 21 is also different, that is, the whole piezoelectric diaphragm 2 has different resonant frequencies, and the bandwidth of the piezoelectric diaphragm is wide, so that the size and shape of each diaphragm 21 can be set according to actual needs. In this embodiment, the plurality of diaphragms 21 have the same size and shape, and are symmetrical structures, and the plurality of diaphragms 21 and the constraint structure 3 cooperate to form a circular structure. Preferably, the constraint structure 3 is integrally formed with the piezoelectric diaphragm 2. Preferably, the constraint structure 3 and the piezoelectric diaphragm 2 are in the same plane.

Optionally, an insulating layer (not shown) is further disposed between the piezoelectric diaphragm 2 and the substrate 1, which not only can support the piezoelectric diaphragm 2, but also can ensure insulation between the piezoelectric diaphragm 2 and the substrate 1.

Example two

Referring to fig. 5, the piezoelectric MEMS microphone 200 of the present embodiment is substantially the same as the piezoelectric MEMS microphone 100 of the first embodiment, and the main differences are as follows: a plurality of said membranes 21 cooperate with said constraining structure 3 to enclose a square structure. The piezoelectric diaphragm 2 includes four diaphragms 21, and the constraint structure 3 located in the central area of the piezoelectric diaphragm 2 is a square net structure, and other structures are substantially the same and are not repeated.

Compared with the prior art, the piezoelectric MEMS microphone has the advantages that the free ends 212 of the diaphragms 21 are limited in the same plane by arranging the constraint structures 3, when the diaphragms 21 are released from the substrate 1, the constraint structures 3 can limit the deformation degree of the diaphragms 21, so that gaps between every two adjacent diaphragms 21 are consistent, the structural difference caused by deformation of different pressure sensor chips is reduced, and the uniformity of product performance is improved; meanwhile, the constraint structure 3 is also beneficial to improving the anti-falling performance of the microphone.

While the foregoing is directed to embodiments of the present invention, it will be understood by those skilled in the art that various changes may be made without departing from the spirit and scope of the invention.

Claims

1. A piezoelectric MEMS microphone comprises a substrate with a back cavity and a piezoelectric diaphragm arranged on the substrate, the piezoelectric diaphragm comprises a plurality of diaphragms, each diaphragm comprises a fixed end connected with the substrate and a free end connected with the fixed end and suspended above the back cavity, two adjacent diaphragms are arranged at intervals or in contact with each other, characterized in that the piezoelectric MEMS microphone further comprises a constraint structure positioned in the central area of the piezoelectric diaphragm, and the free ends of at least two of the diaphragms are connected with the constraint structure, the constraint structure comprises a body part and four openings which are arranged through the body part, the four openings are arranged around the center of the body part at equal angular intervals, the free end is connected with the body part, a hole structure is formed between the free end and the body part and is wrapped outside the body part;

the open pores and the pore structures are both fan-shaped; or the open holes are L-shaped, and the hole structures are all in a straight line shape.

2. The piezoelectric MEMS microphone of claim 1, wherein a free end of each of the diaphragms is connected to the constraining structure.

3. The piezoelectric MEMS microphone of claim 1 or 2, wherein the constraining structure is integrally formed with the piezoelectric diaphragm.

4. The piezoelectric MEMS microphone of claim 3, wherein the constraining structure is in the same plane as the piezoelectric diaphragm.

5. The piezoelectric MEMS microphone of claim 1, wherein the free end is coupled to the constraining structure in a manner comprising at least one of a rigid connection or a flexible connection.

6. The piezoelectric MEMS microphone of claim 1, wherein the constraining structure is a symmetric structure or an asymmetric structure.

7. The piezoelectric MEMS microphone of claim 1, wherein the plurality of diaphragms are all the same size and shape, and cooperate with the constraining structure to form a circular structure.

8. The piezoelectric MEMS microphone of claim 1, wherein the plurality of diaphragms are identical in size and shape, and cooperate with the constraining structure to form a regular polygon structure.

9. The piezoelectric MEMS microphone of claim 1, wherein a cross-sectional area of the back cavity is smaller than a cross-sectional area of the piezoelectric diaphragm, and a cross-sectional area of the constraining structure is smaller than a cross-sectional area of the back cavity.