WO2022104932A1

WO2022104932A1 - Piezoelectric microphone

Info

Publication number: WO2022104932A1
Application number: PCT/CN2020/133741
Authority: WO
Inventors: 石正雨; 童贝
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: 2020-11-19
Filing date: 2020-12-04
Publication date: 2022-05-27
Also published as: CN213991016U

Abstract

Provided is a piezoelectric microphone, comprising: a substrate having an accommodation cavity; and a cantilever beam fixed to the substrate. The cantilever beam comprises a fixed portion fixed at the substrate and a free portion extending from the fixed portion and suspended above the accommodation cavity. The thickness of the free portion is less than the thickness of the fixed portion. Alternatively, the thickness of a portion of the free portion is less than the thickness of the fixed portion. The cantilever beam comprises an upper electrode layer and a lower electrode layer which are arranged in a stacked manner, and at least one piezoelectric layer sandwiched between the upper electrode layer and the lower electrode layer. In the piezoelectric microphone of the present invention, the cantilever beam has reduced mass, such that the resonance frequency of the cantilever beam can be improved, and noise of the microphone can be reduced.

Description

Piezo Microphone

technical field

The present application relates to the technical field of acoustic-electrical conversion, and in particular, to a piezoelectric microphone.

Background technique

Microphone is an acoustic-electrical conversion transducer, which can convert the sound pressure signal of external conditions into electrical signals for output, and form different electrical signals according to the different characteristics of the sound pressure signals for storage and transportation, and transmit signals.

The piezoelectric microphone in the prior art is a cantilever beam structure with 3 layers (electrode/piezoelectric material/electrode) or 5 layers (electrode/piezoelectric material/electrode/piezoelectric material/electrode). The beam is divided into a voltage sensing area and other areas. The edges of each cantilever beam are fixed, and the cantilever beam bends under the action of sound pressure, and the piezoelectric film at the voltage sensing part is subjected to force to generate an electrical signal. However, in order to ensure sufficient sensitivity of the microphone, it is usually necessary to increase the length of the cantilever beam, which reduces the resonant frequency of the microphone and thus increases the noise of the microphone.

Therefore, it is necessary to provide a new piezoelectric microphone to solve the above-mentioned defects.

technical problem

The purpose of the present application is to provide a piezoelectric microphone, which can reduce the mass of the cantilever beam, thereby increasing the resonance frequency of the cantilever beam and reducing the noise of the microphone.

technical solutions

The technical solution of the present application is as follows: a piezoelectric microphone is provided, including:

a base with a receiving cavity;

A cantilever beam fixed on the base, the cantilever beam includes a fixed part fixed on the base and a free part extended from the fixed part and suspended on the receiving cavity, the thickness of the free part is less than The thickness of the fixed part, or the thickness of the part of the free part is smaller than the thickness of the fixed part; the cantilever beam includes an upper electrode layer and a lower electrode layer that are stacked and sandwiched between the upper electrode layer and the lower electrode layer. at least one piezoelectric layer between the lower electrode layers.

According to an embodiment of the present application, the free portion is formed with a plurality of first groove structures arranged at intervals in a direction perpendicular to the vibration direction of the cantilever beam, and formed between two adjacent first groove structures There is the first reinforcement structure.

According to an embodiment of the present application, the first groove structure extends from the fixed portion toward the free portion, and the first groove structure is recessed along the vibration direction.

According to an embodiment of the present application, the free portion includes a connecting segment connected to the fixing portion and a free segment extending from the connecting segment in a direction away from the fixing portion, and the thickness of the free segment is smaller than that of the fixed portion. the thickness of the fixing part.

According to an embodiment of the present application, a plurality of second groove structures arranged at intervals are formed on the free section perpendicular to the vibration direction of the cantilever beam, and two adjacent second groove structures are formed between two adjacent groove structures. There is a second reinforcement structure.

According to an embodiment of the present application, the second groove structure extends from the connecting section in a direction away from the fixing portion, and the second groove structure is recessed along the vibration direction.

According to an embodiment of the present application, the shape of the orthographic projection of the cantilever beam on the base along the vibration direction of the cantilever beam is one of a rectangle, a trapezoid, a triangle and a fan.

According to an embodiment of the present application, a plurality of cantilever beams are provided, and a gap is provided between two adjacent cantilever beams.

According to an embodiment of the present application, at least two of the piezoelectric layers are sandwiched between the upper electrode layer and the lower electrode layer, and the cantilever beam further includes sandwiched between the adjacent piezoelectric layers. between the intermediate electrode layers.

beneficial effect

The beneficial effect of the present application is that: by setting the thickness of the free part to be smaller than the thickness of the fixed part, or the thickness of a part of the free part is smaller than the thickness of the fixed part, the mass of the cantilever beam can be reduced under the cantilever beam of the same area, thereby reducing the mass of the cantilever beam. Increase the resonant frequency of the cantilever beam and reduce the noise of the microphone.

Description of drawings

FIG. 1 is a schematic structural diagram of a piezoelectric microphone according to a first embodiment of the application;

Fig. 2 is the sectional view of the line A-A of Fig. 1;

3 is a schematic structural diagram of a piezoelectric microphone according to a second embodiment of the present application;

Fig. 4 is the sectional view of the line B-B of Fig. 3;

5 is a schematic structural diagram of a piezoelectric microphone according to a third embodiment of the present application;

Fig. 6 is the sectional view of the C-C line of Fig. 5;

FIG. 7 is a partial enlarged schematic diagram of the D area in FIG. 1 .

Embodiments of the present invention

The present application will be further described below with reference to the accompanying drawings and embodiments.

Referring to FIGS. 1 to 6 , the piezoelectric microphone 100 includes a substrate 10 , a cantilever beam 20 fixed on the substrate 10 , and a piezoelectric laminate structure 30 disposed on the cantilever beam 20 .

Further, the base 10 includes an accommodating cavity 11 and an annular peripheral wall 12 surrounding the accommodating cavity 11 , and the shape of the base 10 may be a circle or a polygon. The substrate 10 is a micro-silicon substrate.

Further, the cantilever beam 20 includes a fixed portion 21 fixed on the base 10 and a free portion 22 extending from the fixed portion 21 and suspended on the receiving cavity 11 . The thickness of the free portion 22 is smaller than the thickness of the fixed portion 21, or the free portion The thickness of the partial region of 22 is smaller than the thickness of the fixing portion 21 . Further, the thickness of the free part 22 is smaller than the thickness of the fixed part 21 can be understood as the thickness of the free part 22 gradually decreases from the fixed part 21 to the direction of the free part 22; The thickness can be understood as the thickness of the partial region of the free portion 22 gradually decreases from the fixed portion 21 to the direction of the free portion 22 .

The shape of the orthographic projection of the cantilever beam 20 on the base 10 along the vibration direction of the cantilever beam 20 is one of a rectangle, a trapezoid, a triangle and a fan. A plurality of cantilever beams 20 are provided, and a gap 23 is provided between two adjacent cantilever beams 20 . In this embodiment, each cantilever beam 20 includes a fixed portion 21 and a free portion 22 . The shape of the orthographic projection of the cantilever beam 20 on the substrate 10 along the vibration direction of the cantilever beam 20 in this embodiment is a rectangle, and the number is two.

In one embodiment, referring to FIGS. 1 and 2 , when the thickness of the free portion 22 is smaller than the thickness of the fixed portion 21 , further, referring to FIGS. 3 and 4 , the free portion 22 is perpendicular to the vibration direction of the cantilever beam 20 . A plurality of first groove structures 221 are formed at intervals, and a first reinforcing structure 222 is formed between two adjacent first groove structures 221 . The height of the first reinforcement structure 222 is smaller than the height of the fixed portion 21 and is equal to the height of the free portion 22 , and the height of the first groove structure 221 is smaller than that of the free portion 22 . The first groove structure 221 extends from the fixed portion 21 toward the free portion 22 , and the first groove structure 221 is recessed along the vibration direction.

In another embodiment, please refer to FIG. 5 and FIG. 6 , the thickness of a partial region of the free portion 22 is smaller than the thickness of the fixed portion 21 , specifically, the free portion 22 is formed with a plurality of intervals perpendicular to the vibration direction of the cantilever beam 20 . The second groove structures 223 are provided, and a second reinforcing structure 224 is formed between two adjacent second groove structures 223 . The height of the second reinforcing structure 224 is equal to the height of the fixing portion 21 , and the height of the second groove structure 223 is smaller than the height of the fixing portion 21 . The second groove structure 223 extends from the fixed portion 21 toward the free portion 22 , and the second groove structure 223 is recessed along the vibration direction.

In yet another embodiment, when the thickness of the partial area of the free portion 22 is smaller than the thickness of the fixed portion 21, further, the free portion 22 is divided into two partial areas, and the free portion 22 includes a connection segment connected to the fixed portion 21 (in the figure). (not shown) and a free segment (not shown in the figure) extending from the connecting segment in the direction away from the fixing part 21 , the thickness of the free segment is smaller than that of the fixing part 21 , and the thickness of the connecting segment is the same as the thickness of the fixing part 21 . A plurality of third groove structures (not shown in the figure) arranged at intervals are formed in the free section perpendicular to the vibration direction of the cantilever beam 20, and a third reinforcement structure ( not shown in the figure). The height of the third reinforcement structure is smaller than the height of the fixing portion 21 and is equal to the height of the free segment, and the height of the third groove structure is smaller than the height of the free segment. The third groove structure extends from the connecting section toward the direction away from the fixing portion 21 , and the third groove structure is recessed along the vibration direction.

Further, the piezoelectric laminated structure 30 includes an upper electrode layer and a lower electrode layer arranged in layers and at least one piezoelectric layer sandwiched between the upper electrode layer and the lower electrode layer.

In one embodiment, a piezoelectric layer is disposed between the upper electrode layer and the lower electrode layer, and the piezoelectric laminated structure 30 includes an upper electrode layer, a piezoelectric layer and a lower electrode layer stacked sequentially from top to bottom. The piezoelectric layer is made of aluminum nitride, scandium-doped aluminum nitride, zinc oxide or lead zirconate titanate piezoelectric ceramic material, or a combination of the above materials, and the upper electrode layer and the lower electrode layer are made of aluminum, molybdenum or titanium. , or a combination of the above materials.

In another embodiment, at least two piezoelectric layers are sandwiched between the upper electrode layer and the lower electrode layer, and the piezoelectric laminate structure 30 further includes a middle electrode layer sandwiched between adjacent piezoelectric layers. Referring to FIGS. 2 and 7 , two piezoelectric layers are disposed between the upper electrode layer 31 and the lower electrode layer 35 , and the piezoelectric laminated structure 30 includes an upper electrode layer 31 and an upper piezoelectric layer that are stacked in sequence from top to bottom. layer 32 , intermediate electrode layer 33 , lower piezoelectric layer 34 and lower electrode layer 35 . The upper piezoelectric layer 32 and the lower piezoelectric layer 34 are made of aluminum nitride, scandium-doped aluminum nitride, zinc oxide or lead zirconate titanate piezoelectric ceramic material, or a combination of the above-mentioned materials. The electrode layer 33 and the lower electrode layer 35 are made of aluminum, molybdenum or titanium, or a combination of the above-mentioned materials.

In other embodiments, the number of piezoelectric layers may also be three layers, four layers or more, which is not limited in this embodiment.

In the piezoelectric microphone 100 of this embodiment, when an external sound signal is transmitted from the sound hole, under the action of sound pressure, the free portion 22 vibrates, which drives the piezoelectric laminated structure 30 to vibrate, so that the fixed portion 21 is close to the piezoelectric microphone 100 . The piezoelectric laminate structure 30 generates a voltage signal. Under the cantilever beam 20 of the same area, by reducing the mass of the cantilever beam 20, the free part of the cantilever beam 20 can be deformed more, thereby increasing the resonance frequency of the cantilever beam 20 and reducing the noise of the microphone.

The piezoelectric microphone 100 of this embodiment can be used in a piezoelectric microphone device, and the piezoelectric microphone device includes a plurality of piezoelectric microphones distributed in an array structure. Multiple piezoelectric microphones can be connected in parallel or in series. Piezoelectric microphone devices include but are not limited to microphones, mobile phones, PCs, and vehicle-mounted voice recognition. By using multiple piezoelectric microphones, the generated voltage signals are superimposed on each other, thereby effectively enhancing the sensitivity of the piezoelectric microphone device.

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

Claims

1. A piezoelectric microphone, comprising:

a base with a receiving cavity;

2 . The piezoelectric microphone according to claim 1 , wherein the free portion is formed with a plurality of first groove structures arranged at intervals along the vibration direction perpendicular to the cantilever beam, and two adjacent groove structures are formed. A first reinforcement structure is formed between the first groove structures.

3. The piezoelectric microphone of claim 2, wherein the first groove structure extends from the fixed portion toward the free portion, and the first groove structure vibrates along the direction of the free portion. Directional depressions are formed.

4. The piezoelectric microphone according to claim 1, wherein the free portion comprises a connecting segment connected to the fixing portion and a free portion extending from the connecting segment in a direction away from the fixing portion. segment, the thickness of the free segment is smaller than the thickness of the fixed portion.

5. The piezoelectric microphone according to claim 4, wherein the free segment is formed with a plurality of second groove structures arranged at intervals along the vibration direction perpendicular to the cantilever beam, and two adjacent groove structures are formed. A second reinforcement structure is formed between the second groove structures.

6. The piezoelectric microphone of claim 5, wherein the second groove structure extends from the connecting section in a direction away from the fixing portion, and the second groove structure extends along the The vibration direction concave is formed.

7. The piezoelectric microphone according to claim 1, wherein the shape of the orthographic projection of the cantilever beam on the substrate along the vibration direction of the cantilever beam is a rectangle, a trapezoid, a triangle and a fan shape A sort of.

8. The piezoelectric microphone of claim 1, wherein a plurality of cantilever beams are provided, and a gap is provided between two adjacent cantilever beams.

9. The piezoelectric microphone of claim 1, wherein at least two piezoelectric layers are sandwiched between the upper electrode layer and the lower electrode layer, and the cantilever beam further comprises a sandwich The intermediate electrode layer is arranged between the adjacent piezoelectric layers.