CN115278490A

CN115278490A - Piezoelectric MEMS microphone

Info

Publication number: CN115278490A
Application number: CN202211071657.8A
Authority: CN
Inventors: 胡博豪; 杨超翔; 刘文娟; 孙博文; 孙成亮
Original assignee: Wuhan Memsonics Technologies Co Ltd
Current assignee: Wuhan Memsonics Technologies Co Ltd
Priority date: 2022-09-02
Filing date: 2022-09-02
Publication date: 2022-11-01

Abstract

The embodiment of the application provides a piezoelectric type MEMS microphone, includes: the first piezoelectric cantilever beam is used for converting a received sound signal into a first electric signal, and the second piezoelectric cantilever beam is used for converting the received sound signal into a second electric signal; the first electric signal and the second electric signal have opposite phases, the two groups of induction signals are output through the 3 channels, differential mode signals are enhanced through the differential subtraction circuit, and common mode noise signals are suppressed. Through the method and the device, the problem of poor signal quality of the piezoelectric MEMS microphone is solved, and then pickup characteristics such as signal-to-noise ratio (SNR) and noise resolution of the piezoelectric MEMS microphone are improved.

Description

Piezoelectric MEMS microphone

Technical Field

The embodiment of the application relates to the technical field of microphones, in particular to a piezoelectric type MEMS microphone.

Background

Micro-Electro-Mechanical System (MEMS) microphones are widely used in microphones, mobile phones, computers, and vehicle-mounted voice devices, and have the advantages of small size, high sensitivity, low cost, and the like. MEMS microphones that are common today include capacitive microphones (silicon microphones) and piezoelectric microphones (piezo microphones). The piezoelectric microphone is composed of a single piezoelectric vibrating diaphragm, has the advantages of being waterproof, dustproof, low in power consumption, large in dynamic response range, short in starting time, simple in matching circuit and the like, meets requirements of 'multi-environment', 'zero power consumption', 'long standby' awakening scenes, and is very suitable for being applied to intelligent home, intelligent driving, wearable equipment and the like. However, compared with a capacitive MEMS microphone, the piezoelectric MEMS microphone has a larger background noise, and the background noise of the piezoelectric MEMS microphone is generally suppressed by optimizing parameters such as structural parameters, reducing material loss, and expanding the back cavity volume in the prior art, but due to a limited level, a signal-to-noise ratio (SNR) cannot be effectively improved, so that the signal quality of the existing piezoelectric MEMS microphone is generally poor.

Aiming at the problem of poor signal quality of the piezoelectric MEMS microphone in the related art, an effective solution is not provided yet.

Disclosure of Invention

The embodiment of the application provides a piezoelectric type MEMS microphone, which at least solves the problem that the signal quality of the piezoelectric type MEMS microphone in the related technology is poor.

According to an embodiment of the present application, there is provided a piezoelectric MEMS microphone including: a first piezoelectric cantilever and a second piezoelectric cantilever, wherein,

the first piezoelectric cantilever beam is used for converting a received sound signal into a first electric signal, and the second piezoelectric cantilever beam is used for converting the received sound signal into a second electric signal;

the first electrical signal is in opposite phase to the second electrical signal.

In one exemplary embodiment, the first piezoelectric cantilever and the second piezoelectric cantilever are each a piezoelectric unimorph, wherein,

the piezoelectric monocrystal piece comprises: the piezoelectric device comprises a substrate, a bottom electrode, a piezoelectric film and a top electrode;

the first piezoelectric cantilever beam outputs the first electric signal through the bottom electrode, and the top electrode is grounded;

the second piezoelectric cantilever beam outputs the second electric signal through the top electrode, and the bottom electrode is grounded.

In one exemplary embodiment, the first piezoelectric cantilever and the second piezoelectric cantilever are each a piezoelectric bimorph, wherein,

the piezoelectric bimorph includes: the piezoelectric device comprises a lower electrode, a first piezoelectric film, a middle layer electrode, a second piezoelectric film and an upper electrode;

the first piezoelectric cantilever beam outputs the first electric signal through the lower electrode and the upper electrode, and the middle layer electrode is grounded;

the second piezoelectric cantilever beam outputs the second electric signal through the middle layer electrode, and the lower electrode and the upper electrode are grounded.

In an exemplary embodiment, the piezoelectric MEMS microphone further includes: fixing the boundary, wherein,

the fixed boundary fixes one end of each of the first piezoelectric cantilever beam and the second piezoelectric cantilever beam, and the other end of each piezoelectric cantilever beam forms a free end.

In one exemplary embodiment, the first piezoelectric cantilever and the second piezoelectric cantilever form an active area of the piezoelectric MEMS microphone, wherein,

the fixed boundary is arranged at the periphery of the working area, or the fixed boundary is arranged in the middle of the working area.

In an exemplary embodiment, in a case where the fixed boundary is disposed at a middle portion of the working area, the piezoelectric MEMS microphone further includes: a connecting bracket, wherein,

the connecting support is arranged between every two piezoelectric cantilever beams, and each piezoelectric cantilever beam is anchored on the periphery of the working area through the connecting support.

In one exemplary embodiment, the piezoelectric MEMS microphone further includes: a flexible structure having, therein,

each piezoelectric cantilever beam is connected to the connecting support through the flexible structure;

the flexible structure controls the piezoelectric cantilever beam to synchronously vibrate in the working area.

In an exemplary embodiment, the piezoelectric MEMS microphone further includes: a first signal port, a second signal port, and a ground signal port, wherein,

the first signal port is connected with an electrode which is arranged on the first piezoelectric cantilever beam and outputs the first electric signal;

the second signal port is connected with an electrode which is arranged on the second piezoelectric cantilever beam and outputs the second electric signal;

and the grounding signal port is connected with the electrodes which are grounded on the first piezoelectric cantilever beam and the second piezoelectric cantilever beam.

In an exemplary embodiment, the piezoelectric MEMS microphone further includes: a differential amplification circuit, wherein the differential amplification circuit comprises a first input terminal, a second input terminal, and an output terminal,

the first input end is connected with the first signal port, and the second input end is connected with the second signal port;

the differential amplification circuit amplifies the first electric signal to obtain a first amplified signal, and amplifies the second electric signal to obtain a second amplified signal; carrying out differential operation on the first amplified signal and the second amplified signal to obtain a differential signal; and outputting the differential signal by the output end.

In one exemplary embodiment, the number of the first piezoelectric cantilevers is equal to the number of the second piezoelectric cantilevers, and the first piezoelectric cantilevers and the second piezoelectric cantilevers are arranged in a staggered manner.

Through this application, including two types of piezoelectricity cantilever beams in the piezoelectric type MEMS microphone, first piezoelectricity cantilever beam and second piezoelectricity cantilever beam promptly, two types of piezoelectricity cantilever beam staggered arrangement, it can convert received sound signal into opposite-phase's response signal of telecommunication respectively to make the signal of piezoelectric type MEMS microphone can form differential signal, thereby restrain the background noise, piezoelectric type MEMS microphone can output the signal that SNR is higher, and noise resolution is higher. Therefore, the problem of poor signal quality of the piezoelectric MEMS microphone can be solved, and the pickup effect of the piezoelectric MEMS microphone is improved.

Drawings

FIG. 1 is a first schematic diagram of a piezoelectric MEMS microphone according to an embodiment of the present disclosure;

FIG. 2 is a schematic diagram of a piezoelectric MEMS microphone with a diaphragm structure of a piezoelectric single crystal structure according to an alternative embodiment of the present application;

FIG. 3 is a schematic diagram of a piezoelectric MEMS microphone with a diaphragm structure using a piezoelectric bimorph structure according to an alternative embodiment of the present disclosure;

FIG. 4 is a second schematic structural diagram of a piezoelectric MEMS microphone according to an embodiment of the present disclosure;

FIG. 5 is a schematic diagram of a piezoelectric MEMS microphone in accordance with an alternative embodiment of the present application;

fig. 6 is a schematic structural diagram of a piezoelectric MEMS microphone according to an embodiment of the present disclosure;

FIG. 7 is a schematic diagram of a piezoelectric MEMS microphone with a fixed boundary disposed in the middle of the active area according to an alternative embodiment of the present application;

FIG. 8 is a fourth schematic structural diagram of a piezoelectric MEMS microphone according to an embodiment of the present application;

FIG. 9 is a first schematic view of a flexible structure shape according to an embodiment of the present application;

FIG. 10 is a second schematic view of a flexible structure shape in accordance with embodiments of the present application;

fig. 11 is a schematic structural diagram of a piezoelectric MEMS microphone according to an embodiment of the present disclosure;

FIG. 12 is a schematic diagram of a three-channel differential output piezoelectric MEMS microphone according to an alternative embodiment of the present application;

FIG. 13 is a sixth schematic diagram of a piezoelectric MEMS microphone according to an embodiment of the present application;

FIG. 14 is a schematic diagram of a connection circuit for a microphone element according to an alternative embodiment of the present application.

Detailed Description

Embodiments of the present application will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.

It should be noted that the terms "first," "second," and the like in the description and claims of this application and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.

In this embodiment, a piezoelectric MEMS microphone is provided, and fig. 1 is a schematic structural diagram of a piezoelectric MEMS microphone according to an embodiment of the present application, as shown in fig. 1, the piezoelectric MEMS microphone includes: a first piezoelectric cantilever 102 and a second piezoelectric cantilever 104, wherein the first piezoelectric cantilever 102 is configured to convert a received acoustic signal into a first electrical signal a and the second piezoelectric cantilever 104 is configured to convert a received acoustic signal into a second electrical signal B; the first electrical signal a is in phase opposition to the second electrical signal B.

Through the structure, the piezoelectric MEMS microphone comprises two types of piezoelectric cantilevers, namely the first piezoelectric cantilever and the second piezoelectric cantilever, the two types of piezoelectric cantilevers are arranged in a staggered mode and can respectively convert received sound signals into electric signals with opposite phases, so that the signals of the piezoelectric MEMS microphone can form differential signals, and the differential signals and the common-mode signals are processed through the differential amplification circuit, so that background noise is suppressed, and the piezoelectric MEMS microphone can output signals with higher signal-to-noise ratio and resolution ratio. Therefore, the problem of poor signal quality of the piezoelectric MEMS microphone can be solved, and the pickup effect of the piezoelectric MEMS microphone is improved.

Optionally, in this embodiment, the number of the first piezoelectric cantilevers is equal to the number of the second piezoelectric cantilevers, and the first piezoelectric cantilevers and the second piezoelectric cantilevers may be distributed in a staggered and adjacent manner, or may also be randomly distributed.

Optionally, in this embodiment, the first piezoelectric cantilever beam may also be referred to as a first type piezoelectric cantilever beam, the second piezoelectric cantilever beam may also be referred to as a second type piezoelectric cantilever beam, the first type piezoelectric cantilever beam and the second type piezoelectric cantilever beam are the same in number and are arranged in a staggered manner to form a working area, so as to form the piezoelectric MEMS microphone with a single piezoelectric diaphragm, and the first type piezoelectric cantilever beam and the second type piezoelectric cantilever beam output two types of electrical signals with opposite phases, that is, the first electrical signal and the second electrical signal, so as to form the piezoelectric MEMS microphone which implements differential output through the single piezoelectric diaphragm.

The piezoelectric diaphragm of the working area of the piezoelectric MEMS microphone is divided into two types of areas, the two types of areas are arranged in a staggered mode, and the two types of areas output electric signals with opposite phases respectively, so that differential output of the signals is formed. Or, half of the piezoelectric cantilevers in a single working area output the signal A, and the other half of the piezoelectric cantilevers output the signal B, so as to perform differential output.

Optionally, in this embodiment, the working area has a symmetric structure, and may have an axisymmetric structure, or may have a centrosymmetric structure. The working area may be, but is not limited to, a circular area, an octagonal area, or various even-sided polygonal areas.

Optionally, in this embodiment, the first electrical signal is opposite in phase to the second electrical signal. Such as: the first electrical signal is a positive voltage, and the second electrical signal is a negative voltage. Alternatively, the first electrical signal is a negative voltage and the second electrical signal is a positive voltage. The first electrical signal and the second electrical signal are not necessarily equal in magnitude, and may be equal or different.

Optionally, in this embodiment, the first acoustic signal is an acoustic signal received on the first piezoelectric cantilever, and the second acoustic signal is an acoustic signal received on the second cantilever. The first and second sound signals may be the same or different.

Optionally, in this embodiment, the diaphragm structure adopted by the piezoelectric MEMS microphone may include, but is not limited to, a piezoelectric single crystal wafer or a piezoelectric bimorph, and the like.

Alternatively, in the present embodiment, the first piezoelectric cantilever and the second piezoelectric cantilever may be, but not limited to, form electrical signals with opposite phases by means of opposite electrode leading-out.

In one exemplary embodiment, the first piezoelectric cantilever and the second piezoelectric cantilever are each a piezoelectric unimorph, wherein the piezoelectric unimorph includes: the piezoelectric device comprises a substrate, a bottom electrode, a piezoelectric film and a top electrode; the first piezoelectric cantilever beam outputs the first electric signal through the bottom electrode, and the top electrode is grounded; the second piezoelectric cantilever beam outputs the second electric signal through the top electrode, and the bottom electrode is grounded.

Optionally, in this embodiment, if the piezoelectric cantilever beams disposed on the piezoelectric MEMS microphone are both of a piezoelectric unimorph structure, that is, the piezoelectric MEMS microphone uses a piezoelectric diaphragm of a piezoelectric unimorph structure, the two types of piezoelectric cantilever beams may be, but not limited to, form electrical signals with opposite phases by using opposite electrode leading-out manners, that is, the first piezoelectric cantilever beam outputs the first electrical signal using the bottom electrode of the piezoelectric unimorph as a terminal, and the top electrode of the piezoelectric unimorph is grounded. The second piezoelectric cantilever beam outputs a second electric signal by taking the top electrode of the piezoelectric single crystal wafer as a terminal, and the bottom electrode of the piezoelectric single crystal wafer is grounded.

In an alternative embodiment, an example is provided in which a diaphragm structure of a piezoelectric MEMS microphone is a piezoelectric single crystal structure. Fig. 2 is a schematic diagram of a piezoelectric MEMS microphone with a diaphragm structure adopting a piezoelectric single crystal structure according to an alternative embodiment of the present application, where, as shown in fig. 2, the piezoelectric single crystal includes a substrate layer 201, a bottom electrode 202, a piezoelectric film 203, and a top electrode 204. If the bottom electrode 202 of the class a cantilever (i.e., the second piezoelectric cantilever) is grounded and the top electrode 204 is terminated, the bottom electrode 202 of the class B cantilever (i.e., the first piezoelectric cantilever) corresponding thereto is terminated and the top electrode 204 is grounded.

In one exemplary embodiment, the first piezoelectric cantilever and the second piezoelectric cantilever are each a piezoelectric bimorph, wherein the piezoelectric bimorph includes: the piezoelectric device comprises a lower electrode, a first piezoelectric film, a middle layer electrode, a second piezoelectric film and an upper electrode; the first piezoelectric cantilever beam outputs the first electric signal through the lower electrode and the upper electrode, and the middle layer electrode is grounded; the second piezoelectric cantilever beam outputs the second electric signal through the middle layer electrode, and the lower electrode and the upper electrode are grounded.

Optionally, in this embodiment, if the piezoelectric cantilever beams disposed on the piezoelectric MEMS microphone are both of a piezoelectric bimorph structure, that is, the piezoelectric MEMS microphone uses a piezoelectric diaphragm of a piezoelectric bimorph structure, the two types of piezoelectric cantilever beams may be, but are not limited to, form electrical signals with opposite phases by using opposite electrode leading-out manners, that is, the first piezoelectric cantilever beam outputs a first electrical signal by using the lower electrode and the upper electrode of the piezoelectric bimorph as terminals, and the middle electrode of the piezoelectric bimorph is grounded; the second piezoelectric cantilever beam outputs a second electric signal by taking the middle layer electrode of the piezoelectric bimorph as a terminal, and the lower electrode and the upper electrode of the piezoelectric bimorph are grounded.

In an alternative embodiment, an example is provided in which the diaphragm structure of the piezoelectric MEMS microphone adopts a piezoelectric bimorph structure. Fig. 3 is a schematic diagram of a piezoelectric MEMS microphone with a diaphragm structure adopting a piezoelectric bimorph structure according to an alternative embodiment of the present disclosure, as shown in fig. 3, the piezoelectric bimorph includes a lower electrode 301, a first piezoelectric film 302, a middle layer electrode 303, a second piezoelectric film 304, and an upper electrode 305. If the lower electrode 301 and the upper electrode 305 of the type a cantilever (i.e., the first piezoelectric cantilever) are terminated and the middle electrode 303 is grounded, the middle electrode 303 of the corresponding type B cantilever (i.e., the second piezoelectric cantilever) is terminated and the lower electrode 301 and the upper electrode 305 are grounded.

In an exemplary embodiment, the piezoelectric MEMS microphone further includes: a fixed boundary, wherein the fixed boundary fixes one end of each of the first and second piezoelectric cantilevers, and the other end of each piezoelectric cantilever forms a free end.

Alternatively, in this embodiment, the piezoelectric MEMS microphone may be, but is not limited to, a vibratable structure with a fixed end and a free end formed by each piezoelectric cantilever beam by a fixed boundary.

In an exemplary embodiment, fig. 4 is a second structural schematic diagram of a piezoelectric MEMS microphone according to an embodiment of the present application, and as shown in fig. 4, the first piezoelectric cantilever and the second piezoelectric cantilever form an operating area 402 of the piezoelectric MEMS microphone, wherein the fixed boundary 404 is disposed at an outer periphery of the operating area 402 (as shown by a solid fixed boundary 404 in fig. 4), or the fixed boundary 404 is disposed at a middle portion of the operating area 402 (as shown by a dashed fixed boundary 404 in fig. 4).

Optionally, in this embodiment, the piezoelectric cantilever of the piezoelectric MEMS microphone may be fixed in a peripheral manner, or may be fixed in a central manner.

In an alternative embodiment, a piezoelectric MEMS microphone is provided that reduces noise floor and improves signal-to-noise ratio (SNR). Fig. 5 is a schematic diagram of a piezoelectric MEMS microphone according to an alternative embodiment of the present application, and as shown in fig. 5, the piezoelectric MEMS microphone structure includes a first type cantilever 501, a second type cantilever 502, and a fixed boundary 503, and the fixed boundary 503 is disposed at the periphery of the working area. The first type cantilever 501 and the second type cantilever 502 output a signal a and a signal B respectively, and the number of the two signals is the same. The overall working area of the piezoelectric MEMS microphone can be circular, octagonal and various polygons with even sides.

In an exemplary embodiment, fig. 6 is a schematic structural diagram of a piezoelectric MEMS microphone according to an embodiment of the present application, where, as shown in fig. 6, the fixed boundary 602 is disposed in a middle portion 604 of the working area, the piezoelectric MEMS microphone further includes: a connecting bracket 606, wherein the connecting bracket 606 is disposed between every two piezoelectric cantilevers, each of which is anchored at the periphery 608 of the active area by the connecting bracket 606.

Optionally, in this embodiment, if the fixed boundary is disposed in the middle of the working area, the connecting support may be disposed between every two piezoelectric cantilevers so that each piezoelectric cantilever is anchored at the periphery of the working area through the connecting support, on one hand, the piezoelectric cantilever is fixed, and on the other hand, the end with the larger area of the piezoelectric cantilever becomes a free end capable of vibrating, so that the output signal under the unit sound pressure is larger, the sensitivity is higher, and the miniaturization of the MEMS microphone and the improvement of the SNR are more facilitated.

In an alternative embodiment, a piezoelectric MEMS microphone is provided with a fixed boundary disposed in the middle of the active area. Fig. 7 is a schematic diagram of a piezoelectric MEMS microphone with a fixed boundary disposed in the middle of the working area according to an alternative embodiment of the present application, as shown in fig. 7, a fixed boundary 705 is disposed in the middle of the working area, a plurality of piezoelectric cantilevers are anchored in the peripheral non-working area 703 through a connecting support 704, and the first type cantilevers 701 and the second type cantilevers 702 are distributed in a staggered manner to output differential signals. When the larger end of the piezoelectric cantilever beam is a free end, the output signal under unit sound pressure is larger, the sensitivity is higher, and the miniaturization of the whole structure and the improvement of the signal to noise ratio are facilitated.

In an exemplary embodiment, fig. 8 is a schematic structural diagram of a piezoelectric MEMS microphone according to an embodiment of the present application, and as shown in fig. 8, the piezoelectric MEMS microphone further includes: a flexible structure 802, wherein each piezoelectric cantilever is connected to the connection bracket 804 through the flexible structure 802; the flexible structure 802 controls the piezoelectric cantilever beam to synchronously vibrate in the working area.

Optionally, in the present embodiment, the number of the flexible structures between each piezoelectric cantilever and the connection bracket may be, but is not limited to, one or more. The flexible structure can ensure synchronous vibration of the working area without limiting the vibration of the working area, and the flexible structure can be but is not limited to a low-rigidity structure with a spring coefficient k. Such as: in the micro-nano preparation process, because different residual stresses exist in each film layer, if the stresses cannot be balanced and offset, the cantilever beams are easy to warp in different degrees, the synchronous vibration of the combined cantilever beams cannot be ensured, the phase deviation of signals A and B occurs, and the purpose of differentially amplifying the signals cannot be achieved. The free end of the cantilever beam and each position adjacent to the connecting support are provided with n Z-shaped flexible structures to interconnect the cantilever beam and the connecting support, so that vibration crosstalk can be reduced, and synchronous vibration of the combined cantilever beam is ensured.

Alternatively, in this embodiment, the flexible structure may be, but is not limited to, any shape that can achieve the above-mentioned functions, such as: a "Z" shape or a "pi" shape. Fig. 9 is a schematic diagram showing a shape of a flexible structure according to an embodiment of the present application, as shown in fig. 9, a connection structure similar to (a) "Z" shape or (b) "pi" shape is added to a free end edge of a cantilever beam, and a spring constant is k. One of the two anchor points of each flexible structure is arranged on the piezoelectric cantilever beam, and the other anchor point is arranged on the connecting support.

Fig. 10 is a second schematic diagram of the shape of a flexible structure according to an embodiment of the present application, and as shown in fig. 10, taking a "Z" shaped connection structure as an example, the flexible structure may be in the form of a first type of flexible structure 1001 or a second type of flexible structure 1002, and the flexible structure connects the piezoelectric cantilever to the connection bracket 1004. The combined cantilever beam with 2m degrees of freedom in the longitudinal direction is connected into a whole through the low-rigidity connecting structures with the spring coefficients of k, the integral rigidity and the stability of the piezoelectric cantilever beam are improved, the size and the number of the flexible structures can be adjusted according to the working requirements of the microphone, and the resonant frequency and the sound pressure overload point (AOP) of the microphone can be adjusted. The added flexibility can ensure the phase synchronization of the displacement function of the combined cantilever beam, the device can stably output differential signals, and the torsional vibration mode of the fan-shaped or inverted trapezoid piezoelectric cantilever beam can be inhibited, so that the output of crosstalk signals is reduced.

In addition to the arrangement of the electrode terminals, differential signals with better effect can be obtained by controlling the synchronous vibration of the combined diaphragm, namely the synchronous vibration of the combined diaphragm is in phase with the displacement function. The main frequency of operation of the MEMS microphone is less than 10kHz, and the wavelength of sound wave is far larger than the size of the microphone device (about 1 mm) ² ) In order to make the combined diaphragm vibrate synchronously, firstly, the structure of the combined diaphragm is completely symmetrical (axisymmetric or centrosymmetric), secondly, the thickness of a film coating is uniform and the stress is balanced during micro-nano processing, otherwise, the combined diaphragm is possibly influenced by residual stress when not in operationIrregular deformation, warping.

Because the residual stress in the micro-nano processing can not be completely eliminated, the extra technical means can be adopted, and the low-rigidity connecting structure (namely the flexible structure) is added at the free end of each cantilever beam, so that a plurality of cantilever beams are anchored on the same fixed frame, the purpose is to limit the freedom degree of the combined cantilever beam, and the vibration of the cantilever beam can not be greatly inhibited. The connecting structure can be a Z-shaped structure, a Pi-shaped structure and the like, one anchor point is arranged on the fixed frame, and the other anchor point is arranged at the free end of the cantilever beam. On one hand, the diaphragm warping caused by residual stress in the micro-nano process preparation process can be reduced, and on the other hand, two signals output by the microphone during working are ensured to be opposite in phase, so that the subsequent differential amplification is facilitated.

In an exemplary embodiment, fig. 11 is a schematic structural diagram of a piezoelectric MEMS microphone according to an embodiment of the present application, and as shown in fig. 11, the piezoelectric MEMS microphone further includes: a first signal port 1102, a second signal port 1104 and a ground signal port 1106, wherein the first signal port 1102 is connected to an electrode of the first piezoelectric cantilever beam, which outputs the first electrical signal; the second signal port 1104 is connected to an electrode of the second piezoelectric cantilever, which outputs the second electrical signal; the ground signal port 1106 connects the electrodes on the first and second piezoelectric cantilevers that are grounded.

Optionally, in this embodiment, the first electrical signal is led out through the first signal port, the second electrical signal is led out through the second signal port, and then the grounded electrode on the piezoelectric cantilever is led out through the grounded signal port, so as to form the piezoelectric MEMS microphone that realizes three-channel differential output through a single piezoelectric diaphragm.

In an alternative embodiment, a three-channel differential output piezoelectric MEMS microphone is provided. Fig. 12 is a schematic diagram of a three-channel differential output piezoelectric MEMS microphone according to an alternative embodiment of the present application, as shown in fig. 12, in (1), the signal a and the signal B are distributed symmetrically, and the differential output piezoelectric MEMS microphone is output through a 3-port, and includes an a signal channel 1201, a B signal channel 1202, and a ground terminal 1203. Taking the extraction of the electrodes of the piezoelectric bimorph as an example, the extraction modes of the terminal signal and the grounding port are shown in (2) and (3). The insulating layer 1206 is used to protect the electrode layer, and the lead-out lower electrode 1204 and upper electrode 1205 serve as the a signal channel 1201 or the ground 1203. The extraction middle layer electrode 1207 serves as the B signal path 1202 or the ground terminal 1203. The common ground of the A signal and the B signal finally forms 3 ports for differential output.

In an exemplary embodiment, fig. 13 is a sixth schematic structural diagram of a piezoelectric MEMS microphone according to an embodiment of the present application, as shown in fig. 13, the piezoelectric MEMS microphone further includes: a differential amplifier circuit 1302, wherein the differential amplifier circuit 1302 includes a first input port 1304, a second input port 1306 and an output port 1308, the first input port 1304 is connected to the first signal port 1102, and the second input port 1306 is connected to the second signal port 1104; the differential amplifier circuit 1302 amplifies the first electrical signal to obtain a first amplified signal, and amplifies the second electrical signal to obtain a second amplified signal; carrying out differential operation on the first amplified signal and the second amplified signal to obtain a differential signal; and outputting the differential signal by the output end.

Optionally, in this embodiment, 2m piezoelectric cantilevers are provided as two parts, where m piezoelectric cantilevers output a signal a, and the other m piezoelectric cantilevers output a signal B, a differential mode signal body in the signal a and the signal B is a useful signal, and a common mode signal body is common mode noise, and after passing through an amplifier circuit and a subtraction circuit in a differential amplification circuit, the output signal is effectively enhanced, and the common mode noise is effectively suppressed.

Optionally, in this embodiment, the piezoelectric MEMS microphone differential output technical solution can effectively improve SNR and reduce nonlinear distortion, and compared with microphone structures such as a three-layer differential condenser microphone with a dual diaphragm and a back plate, the piezoelectric MEMS microphone differential output technical solution has the advantages of simple structure, low micro-nano processing cost, and being beneficial to miniaturization of a microphone pressing device.

In an alternative embodiment, a three-channel differential output piezoelectric MEMS microphone element connection circuit is provided. Fig. 14 is a schematic diagram of a connection circuit of a microphone element according to an alternative embodiment of the present application, and as shown in fig. 14, the microphone element may be a piezoelectric MEMS microphone element of any one of the above structures, the differential output piezoelectric MEMS microphone element is matched with a rear end differential amplification circuit, a sound wave signal is input to the microphone element, a signal a and a signal B are output, and the signal a and the signal B are amplified respectively through two ports of an operational amplifier, and different amplification gain ratios can be obtained by adjusting R1, R2, R3, and Rf. And then two groups of amplified signals at the output end are subtracted, so that the differential mode signal is enhanced, the common mode noise signal is inhibited, the SNR of the whole microphone can be effectively improved, and the nonlinear distortion is inhibited.

Through the structure, the differential output of the microphone signals can be realized by combining the piezoelectric diaphragms, the differential mode induction signals are enhanced, the common mode noise signals are suppressed, and the sensitivity and the signal-to-noise ratio (SNR) of the piezoelectric MEMS microphone can be effectively improved on the premise of not increasing the working area. The fixed boundary is adjusted to the middle of the working area through the connecting support, and the edge of the free end of the cantilever beam is provided with a Z-shaped flexible structure which is connected with the connecting support, so that the sensitivity under unit sound pressure is improved, the problems of warping of a vibrating diaphragm, unsynchronized vibration and the like caused by unbalanced residual stress are solved, the vibration of a plurality of cantilever beams is ensured to be in the same phase, nonlinear distortion caused by vibration crosstalk is effectively inhibited, and differential signals can be stably output. The piezoelectric MEMS microphone structure improves the sensitivity, the signal-to-noise ratio and the response linearity of the piezoelectric MEMS microphone.

It will be apparent to those skilled in the art that the various modules or steps of the present application described above may be implemented using a general purpose computing device, they may be centralized on a single computing device or distributed across a network of multiple computing devices, and they may be implemented using program code executable by the computing devices, such that they may be stored in a memory device and executed by the computing devices, and in some cases, the steps shown or described may be performed in an order different than that described herein, or they may be separately fabricated into separate integrated circuit modules, or multiple ones of them may be fabricated into a single integrated circuit module. Thus, the present application is not limited to any specific combination of hardware and software.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the principle of the present application shall be included in the protection scope of the present application.

Claims

1. A piezoelectric MEMS microphone, comprising: a first piezoelectric cantilever and a second piezoelectric cantilever, wherein,

2. The piezoelectric MEMS microphone of claim 1, wherein the first piezoelectric cantilever and the second piezoelectric cantilever are each a single piezoelectric crystal, wherein,

the piezoelectric single crystal wafer includes: the piezoelectric device comprises a substrate, a bottom electrode, a piezoelectric film and a top electrode;

3. The piezoelectric MEMS microphone of claim 1, wherein the first piezoelectric cantilever and the second piezoelectric cantilever are each a piezoelectric bimorph, wherein,

4. The piezoelectric MEMS microphone of claim 1, further comprising: fixing the boundary, wherein,

5. The piezoelectric MEMS microphone of claim 4, wherein the first piezoelectric cantilever beam and the second piezoelectric cantilever beam form an active area of the piezoelectric MEMS microphone, wherein,

6. The piezoelectric MEMS microphone according to claim 5, further comprising, in a case where the fixed boundary is provided in a middle of the working area: a connecting bracket, wherein,

7. The piezoelectric MEMS microphone of claim 6, further comprising: a flexible structure having, therein,

8. The piezoelectric MEMS microphone of claim 1, further comprising: a first signal port, a second signal port, and a ground signal port, wherein,

the grounding signal port is connected with the electrodes which are grounded on the first piezoelectric cantilever beam and the second piezoelectric cantilever beam.

9. The piezoelectric MEMS microphone of claim 8, further comprising: a differential amplification circuit, wherein the differential amplification circuit comprises a first input terminal, a second input terminal, and an output terminal,

10. The piezoelectric MEMS microphone of any one of claims 1 to 9, wherein the number of the first piezoelectric cantilevers is equal to the number of the second piezoelectric cantilevers, the first piezoelectric cantilevers and the second piezoelectric cantilevers being staggered.