CN111294715A

CN111294715A - Piezoelectric MEMS microphone

Info

Publication number: CN111294715A
Application number: CN202010135109.1A
Authority: CN
Inventors: 石正雨; 童贝; 李杨
Original assignee: AAC Acoustic Technologies Shenzhen Co Ltd
Current assignee: AAC Technologies Holdings Shenzhen Co Ltd
Priority date: 2020-03-02
Filing date: 2020-03-02
Publication date: 2020-06-16
Anticipated expiration: 2040-03-02
Also published as: WO2021174571A1; CN111294715B

Abstract

The present invention provides a piezoelectric MEMS microphone, comprising: a substrate having a back cavity; the piezoelectric diaphragm is arranged opposite to the back cavity and comprises a supporting part arranged above the back cavity; the support part divides the piezoelectric diaphragm into at least two vibration areas; the piezoelectric diaphragm also comprises at least one diaphragm arranged in each vibration area, the diaphragm comprises a fixed end connected with the substrate or the supporting part, a free end parallel to and opposite to the fixed end and a main body part connecting the fixed end and the free end, and the free end and the main body part are both suspended above the back cavity; the width of the main body portion gradually decreases from the fixed end toward the free end. Compared with the related art, the piezoelectric MEMS microphone has high resonant frequency and large sound pressure utilization area, and further improves the sensitivity of the microphone.

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 MEMS microphone.

[ background of the invention ]

MEMS microphones are microphones produced on the basis of MEMS (microelectromechanical systems) technology, i.e. miniature microphones produced on a silicon micro-substrate by means of MEMS processing, and are therefore also referred to as silicon miniature microphones.

Different from the traditional microphone, the MEMS microphone has the characteristics of small size, light weight, simplicity in installation, easiness in forming an array, low cost, batch manufacturing and the like, and is widely applied to mobile phones, notebook computers and the like in the field of consumer electronics, hand-free phones in the field of automobiles, hearing aids in the field of medicine and the like.

Related art piezoelectric MEMS microphone includes a plurality of convergent diaphragms, the diaphragm has stiff end, main part and free end in proper order, each the diaphragm the main part certainly the stiff end stretches out and assembles towards the same point, makes the free end gathers together. But the diaphragm length will inevitably be too long so that the microphone resonant frequency is too low, thereby reducing the microphone sensitivity.

Therefore, a new piezoelectric MEMS microphone must be provided to solve the above technical problems.

[ summary of the invention ]

The invention aims to provide a piezoelectric MEMS microphone with high sensitivity.

In order to achieve the above object, the present invention provides a piezoelectric MEMS microphone comprising:

a substrate having a back cavity; the piezoelectric diaphragm is arranged opposite to the back cavity and comprises a supporting part arranged above the back cavity; the support part divides the piezoelectric diaphragm into at least two vibration areas; the piezoelectric diaphragm also comprises at least one diaphragm arranged in each vibration area, the diaphragm comprises a fixed end connected with the substrate or the supporting part, a free end parallel to and opposite to the fixed end and a main body part connecting the fixed end and the free end, and the free end and the main body part are both suspended above the back cavity; the width of the main body portion gradually decreases from the fixed end toward the free end.

Preferably, the support portion divides the piezoelectric diaphragm into two vibration regions, and the two vibration regions are symmetrically disposed about the support portion.

Preferably, each vibration region is provided with at least two diaphragms, and the free ends of two adjacent diaphragms are oppositely arranged.

Preferably, each of the vibration regions has a trapezoidal shape, and each of the vibration regions includes four diaphragms, free ends of which extend toward a center of the vibration region.

Preferably, the piezoelectric diaphragm further includes a peripheral portion surrounding the vibration region, and the peripheral portion is stacked and fixed above the substrate.

Preferably, the main part is trapezoidal, its include with the first side that the stiff end is connected, set up in the second side of free end and connect two hypotenuses between first side and second side, the length of first side is greater than the length on second side, second side and two hypotenuses all suspend in the top in back of the body chamber.

Preferably, a gap is formed between part of the first side edge and the peripheral portion and/or the supporting portion.

Preferably, adjacent two in four diaphragms form between the second side gap, adjacent two form between the hypotenuse gap and adjacent the second side with all form between the hypotenuse the gap.

Preferably, the membrane comprises a first electrode layer, a piezoelectric layer and a second electrode layer which are sequentially stacked.

Preferably, the membrane comprises a first electrode layer, a piezoelectric layer, a second electrode layer, a piezoelectric layer and a first electrode layer, which are sequentially stacked.

Compared with the prior art, the piezoelectric MEMS microphone provided by the invention is provided with the supporting part on the substrate, the microphone is also provided with the piezoelectric diaphragm which is arranged opposite to the back cavity, and the piezoelectric diaphragm is divided into at least two vibration areas by the supporting part, so that the utilization area of sound pressure under the given area of the piezoelectric diaphragm is larger; at least one diaphragm is arranged in each vibration area, and the length of the diaphragm is shorter, so that the microphone has higher resonant frequency, and the sensitivity of the microphone is improved.

[ 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 perspective view of a piezoelectric MEMS microphone according to a preferred embodiment of the present invention;

fig. 2 is a schematic front projection structure view of the piezoelectric MEMS microphone shown in fig. 1;

FIG. 3 is a cross-sectional view of the piezoelectric MEMS microphone shown in FIG. 2 taken along line A-A;

FIG. 4 is an enlarged schematic view of the piezoelectric MEMS microphone shown in FIG. 2 at B;

fig. 5 is an enlarged structural schematic diagram of the piezoelectric MEMS microphone shown in fig. 2 at C.

[ 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.

Referring to fig. 1 to 5, a piezoelectric MEMS microphone 100 according to the present invention includes: a substrate 2 having a back cavity 20 and a piezoelectric diaphragm 1 disposed opposite to the back cavity 20.

The piezoelectric diaphragm 1 includes a support portion 12 disposed above the back cavity 20. The support portion 12 divides the piezoelectric diaphragm 1 into at least two vibration regions 10. In the present embodiment, the support portion 12 divides the piezoelectric diaphragm 1 into two vibration regions 10, thereby achieving a larger sound pressure utilization area for a given area of the piezoelectric diaphragm 1; it is understood that in other embodiments, the support portion 12 may divide the piezoelectric diaphragm 1 into more or fewer vibration regions 10. In the present embodiment, the front projection view of the vibration region 10 is substantially trapezoidal. The two vibration regions 10 are symmetrically arranged about the support portion 12.

The piezoelectric diaphragm 1 further includes a peripheral portion 15 disposed around the vibration region 10. The peripheral portion 15 is made of the same material as the support portion 12. The peripheral portion 15 is stacked and fixed on the substrate 2, and the supporting portion 12 and the peripheral portion 15 are formed by etching in the process of manufacturing the piezoelectric MEMS microphone.

The piezoelectric diaphragm 1 further includes at least one diaphragm 14 provided in each vibration region 10. Each membrane 14 is formed by stacking at least three layers of material. Optionally, the membrane 14 includes a first electrode layer 101, a piezoelectric layer 102, and a second electrode layer 103, which are stacked in sequence; alternatively, the membrane 14 comprises a first electrode layer 101, a piezoelectric layer 102, a second electrode layer 103, a piezoelectric layer 102 and a first electrode layer 101, which are stacked in this order. The peripheral portion 15, the support portion 12, and the diaphragm 14 are integrally molded using the same material, and each portion is formed by etching.

Specifically, the diaphragm 14 includes a fixed end 142 connected to the substrate 2 and/or the supporting portion 12, a free end 143 disposed parallel to and opposite to the fixed end 142, and a body portion 141 connecting between the fixed end 142 and the free end 143. The width of the body portion 141 gradually decreases from the fixed end 142 toward the free end 141. Both free end 143 and body portion 141 are suspended above back cavity 20. In the present embodiment, the fixed end 142 is substantially elongated, and the free end 143 is also substantially elongated and disposed parallel to the fixed end 142. In the present embodiment, the fixed end 142 is connected to the substrate 2 through the peripheral portion 15, thereby enhancing the connection strength between the fixed end 142 and the substrate 2.

In the present embodiment, the main body 141 is substantially trapezoidal and includes a first side 1411 connected to the fixed end 142, a second side 1412 overlapping the free end 142, and two oblique sides 1413 connected to the first side 1411 and the second side 1412 and spaced apart from each other. The first side 1411 and the second side 1412 are arranged in parallel and the length of the first side 1411 is greater than the length of the second side 1412. The second side edge 1412 and the two sloping sides 1413 each overhang the back cavity 20. When the fixed end 142 is connected to the peripheral portion 15, the first side 1411 is spaced apart from the peripheral portion 15 to form a gap 145. When the fixed end 142 is connected to the supporting portion 12, the first side 1411 is spaced from the supporting portion 12 to form a gap 145. By setting the slit structure to adjust the sensitivity of the microphone 100, the coverage area of the electrode layers (101, 102, 103) is also optimized according to the slit structure to obtain the optimal signal-to-noise ratio. When a plurality of diaphragms 14 are arranged in the vibration region 10, a gap 145 is formed between the adjacent second side edges 1412 of the two diaphragms 14, a gap 145 is also formed between the adjacent oblique edges 1413, and a gap 145 is also formed between the adjacent second side edges 1412 and the oblique edges 1413.

At least two diaphragms 14 may be disposed in the vibration region 10, and the free ends of the adjacent two diaphragms 14 are disposed opposite to each other. In the present embodiment, the vibration region 10 has a trapezoidal shape, and 4 diaphragms 14 are provided. A first diaphragm 1401, a second diaphragm 1402, a third diaphragm 1403, and a fourth diaphragm 1404, respectively. The free ends 142 of the first, second, third and

fourth diaphragms

1401, 1402, 1403 and 1404 each extend toward the center of the vibration region 10. Wherein the first diaphragm 1401 and the second diaphragm 1402 are symmetrically arranged, and the third diaphragm 1403 and the fourth diaphragm 1404 are respectively located at two opposite sides of the first diaphragm 1401 and the second diaphragm 1402. The first membrane 1401 is connected to the peripheral portion 15 via the fixed end 141, and a gap 145 is formed between the first side 1411 and the substrate 2. The second membrane 1402 is connected to the supporting portion 12 through the fixed end 142, and a gap 145 is formed between the first side 1411 of the second membrane 1402 and the supporting portion 12. The second side 1412 of the first diaphragm 1401 and the second side 1412 of the second diaphragm 1402 form a gap 145 therebetween. The third membrane 1403 is connected to one side of the substrate 2 by the fixed end 141, and the first side 1411 thereof forms a gap 145 with one side of the peripheral portion 15; a gap is formed between the second side edge 1412 of the third membrane 1403 and a sloping edge 1413 of the second membrane 1402, a gap 145 is formed between a sloping edge 1413 of the third membrane 1403 and the support portion 12, and a gap 145 is formed between the other sloping edge 1413 and one of the sloping edges 1413 of the first membrane 1401. The fourth diaphragm 1404 is connected to the other side of the peripheral portion 15 through the fixed end 141, and the first side 1411 of the fourth diaphragm forms a gap 145 with the other side of the peripheral portion 15; the second side 1412 of the fourth diaphragm 1404 forms a gap 145 with the other oblique side 1413 of the second diaphragm 1402; one of the oblique sides 1413 of the fourth diaphragm 1404 forms a gap 145 with the other oblique side 1413 of the first diaphragm 1401, and the other oblique side 1413 forms a gap 145 with the support portion 12.

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, comprising:

a substrate having a back cavity;

the piezoelectric diaphragm is arranged opposite to the back cavity and comprises a supporting part arranged above the back cavity; the support part divides the piezoelectric diaphragm into at least two vibration areas;

the piezoelectric diaphragm also comprises at least one diaphragm arranged in each vibration area, the diaphragm comprises a fixed end connected with the substrate or the supporting part, a free end parallel to and opposite to the fixed end and a main body part connecting the fixed end and the free end, and the free end and the main body part are both suspended above the back cavity; the width of the main body portion gradually decreases from the fixed end toward the free end.

2. The piezoelectric MEMS microphone of claim 1, wherein the support portion divides the piezoelectric diaphragm into two vibration regions, and the two vibration regions are symmetrically disposed about the support portion.

3. A piezoelectric MEMS microphone as defined in claim 2, wherein at least two of said diaphragms are provided for each of said vibration regions, and the free ends of two adjacent diaphragms are disposed to be opposed to each other.

4. A piezoelectric MEMS microphone as defined in claim 3, wherein each of the vibration regions has a trapezoidal shape, each of the vibration regions including four diaphragms, free ends of the four diaphragms each extending toward a center of the vibration region.

5. The piezoelectric MEMS microphone according to claim 4, wherein the piezoelectric diaphragm further includes a peripheral portion surrounding the vibration region, the peripheral portion being stacked and fixed above the substrate.

6. The piezoelectric MEMS microphone of claim 5, wherein the main body portion is trapezoidal and includes a first side connected to the fixed end, a second side disposed at the free end, and two oblique sides connected between the first side and the second side, wherein the length of the first side is greater than that of the second side, and the second side and the two oblique sides are both suspended above the back cavity.

7. The piezoelectric MEMS microphone of claim 6, wherein a gap is formed between a portion of the first side and the peripheral portion and/or the support portion.

8. The piezoelectric MEMS microphone of claim 7, wherein the gap is formed between two adjacent second sides of the four diaphragms, the gap is formed between two adjacent oblique sides, and the gap is formed between the second side and the oblique sides.

9. The piezoelectric MEMS microphone of claim 1, wherein the membrane comprises a first electrode layer, a piezoelectric layer, and a second electrode layer sequentially stacked.

10. The piezoelectric MEMS microphone of claim 1, wherein the membrane comprises a first electrode layer, a piezoelectric layer, a second electrode layer, a piezoelectric layer, and a first electrode layer, which are sequentially stacked.