Piezoelectric MEMS microphone

Abstract

The embodiment of the application provides a piezoelectric MEMS microphone, comprising: a first piezoelectric cantilever beam and a second piezoelectric cantilever beam, 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 electric signal and the second electric signal are opposite in phase, two groups of sensing signals are output through three channels, a differential subtraction circuit is passed through, a differential mode signal is enhanced, and a common mode noise signal is suppressed. Through the application, the problem of poor signal quality of the piezoelectric MEMS microphone is solved, and then the signal-to-noise ratio (SNR), noise resolution and other pickup characteristics of the piezoelectric MEMS microphone are improved.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to the technical field of microphones, in particular to a piezoelectric MEMS microphone. BACKGROUND

[0002] Micro-Electro-Mechanical System (MEMS) microphones are widely used in microphones, mobile phones, computers and vehicle voice devices, and have the advantages of small size, high sensitivity, low cost and the like. The commonly used MEMS microphone includes a capacitive microphone (silicon microphone) and a piezoelectric microphone (pressure microphone). The pressure microphone is composed of a single piezoelectric diaphragm, has a simple structure, and has the advantages of waterproof and dustproof, low power consumption, large dynamic response range, short start-up time, simple matching circuit and the like, meets the requirements of "multi-environment", "zero power consumption" and "long standby" wake-up scenes, and is very suitable for smart home, intelligent driving and wearable devices and the like. However, compared with the capacitive MEMS microphone, the piezoelectric MEMS microphone has a large background noise, and the prior art generally suppresses the background noise of the piezoelectric MEMS microphone by optimizing the structure parameters, reducing the material loss and expanding the volume of the back cavity and the like. However, due to the limitation, the signal-to-noise ratio (SNR) cannot be effectively improved, resulting in that the signal quality of the current piezoelectric MEMS microphone is generally poor.

[0003] In view of the problem of poor signal quality of the piezoelectric MEMS microphone in the related art, an effective solution has not been proposed. SUMMARY

[0004] Embodiments of the present application provide a piezoelectric MEMS microphone to at least solve the problem of poor signal quality of the piezoelectric MEMS microphone in the related art.

[0005] According to an embodiment of the present application, a piezoelectric MEMS microphone is provided, comprising: a first piezoelectric cantilever beam and a second piezoelectric cantilever beam, wherein,

[0006] The first piezoelectric cantilever beam is configured to convert a received sound signal into a first electric signal, and the second piezoelectric cantilever beam is configured to convert the received sound signal into a second electric signal.

[0007] The first electric signal and the second electric signal are opposite in phase.

[0008] In one exemplary embodiment, the first piezoelectric cantilever beam and the second piezoelectric cantilever beam are both piezoelectric single crystal wafers, wherein,

[0009] The piezoelectric single crystal wafer comprises: a substrate, a bottom electrode, a piezoelectric thin film and a top electrode.

[0010] The first piezoelectric cantilever outputs the first electric signal through the bottom electrode, and the top electrode is grounded.

[0011] The second piezoelectric cantilever outputs the second electric signal through the top electrode, and the bottom electrode is grounded.

[0012] In one example embodiment, the first piezoelectric cantilever and the second piezoelectric cantilever are both piezoelectric bimorphs, wherein,

[0013] The piezoelectric bimorph includes a lower electrode, a first piezoelectric film, a middle electrode, a second piezoelectric film, and an upper electrode;

[0014] The first piezoelectric cantilever outputs the first electric signal through the lower electrode and the upper electrode, and the middle electrode is grounded.

[0015] The second piezoelectric cantilever outputs the second electric signal through the middle electrode, and the lower electrode and the upper electrode are grounded.

[0016] In one example embodiment, the piezoelectric MEMS microphone further includes a fixed boundary, wherein,

[0017] The fixed boundary fixes one end of each of the first piezoelectric cantilever and the second piezoelectric cantilever, and the other end of each of the piezoelectric cantilevers forms a free end.

[0018] In one example embodiment, the first piezoelectric cantilever and the second piezoelectric cantilever form a working area of the piezoelectric MEMS microphone, wherein,

[0019] The fixed boundary is arranged at an outer periphery of the working area, or the fixed boundary is arranged at a middle portion of the working area.

[0020] In one example embodiment, in the case where the fixed boundary is arranged at the middle portion of the working area, the piezoelectric MEMS microphone further includes a connecting support, wherein,

[0021] The connecting support is arranged between every two piezoelectric cantilevers, and each piezoelectric cantilever is anchored at an outer periphery of the working area through the connecting support.

[0022] In one example embodiment, the piezoelectric MEMS microphone further includes a flexible structure, wherein,

[0023] Each piezoelectric cantilever is connected to the connecting support through the flexible structure.

[0024] The flexible structure controls the piezoelectric cantilevers to vibrate synchronously in the working area.

[0025] In one example embodiment, the piezoelectric MEMS microphone further comprises: a first signal port, a second signal port and a ground signal port, wherein,

[0026] the first signal port is connected to the electrode on the first piezoelectric cantilever beam outputting the first electric signal;

[0027] the second signal port is connected to the electrode on the second piezoelectric cantilever beam outputting the second electric signal;

[0028] the ground signal port is connected to the electrode on the first piezoelectric cantilever beam and the second piezoelectric cantilever beam grounded.

[0029] In one example embodiment, the piezoelectric MEMS microphone further comprises: a differential amplification circuit, wherein the differential amplification circuit comprises a first input end, a second input end and an output end,

[0030] the first input end is connected to the first signal port, and the second input end is connected to the second signal port;

[0031] 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; differentiates the first amplified signal and the second amplified signal to obtain a differential signal; and outputs the differential signal from the output end.

[0032] In one example embodiment, the number of the first piezoelectric cantilever beams is equal to the number of the second piezoelectric cantilever beams, and the first piezoelectric cantilever beams and the second piezoelectric cantilever beams are arranged alternately.

[0033] According to the piezoelectric MEMS microphone, two types of piezoelectric cantilever beams, i.e., the first piezoelectric cantilever beams and the second piezoelectric cantilever beams, are included, and the two types of piezoelectric cantilever beams are arranged alternately, which can respectively convert the received sound signals into induced electric signals with opposite phases, so that the signals of the piezoelectric MEMS microphone can form a differential signal, thereby suppressing the background noise, and the piezoelectric MEMS microphone can output signals with higher signal-to-noise ratio and higher noise resolution. 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. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a structure diagram of a piezoelectric MEMS microphone according to an embodiment of the present application Figure One ;

[0035] Figure 2Fig. 1 is a schematic diagram of a piezoelectric MEMS microphone according to an embodiment of the present application;

[0036] Figure 3 Fig. 2 is a schematic diagram of a piezoelectric MEMS microphone according to an embodiment of the present application;

[0037] Figure 4 Fig. 3 is a schematic diagram of a piezoelectric MEMS microphone according to an embodiment of the present application; Figure Two ;

[0038] Figure 5 Fig. 4 is a schematic diagram of a piezoelectric MEMS microphone according to an embodiment of the present application;

[0039] Figure 6 Fig. 5 is a schematic diagram of a piezoelectric MEMS microphone according to an embodiment of the present application; Figure Three ;

[0040] Figure 7 Fig. 6 is a schematic diagram of a piezoelectric MEMS microphone according to an embodiment of the present application;

[0041] Figure 8 Fig. 7 is a schematic diagram of a piezoelectric MEMS microphone according to an embodiment of the present application; Figure Four ;

[0042] Figure 9 Fig. 8 is a schematic diagram of a flexible structure according to an embodiment of the present application; Figure One ;

[0043] Figure 10 Fig. 9 is a schematic diagram of a flexible structure according to an embodiment of the present application; Figure Two ;

[0044] Figure 11 Fig. 10 is a schematic diagram of a piezoelectric MEMS microphone according to an embodiment of the present application; Figure Five ;

[0045] Figure 12 Fig. 11 is a schematic diagram of a piezoelectric MEMS microphone according to an embodiment of the present application;

[0046] Figure 13 Fig. 12 is a schematic diagram of a piezoelectric MEMS microphone according to an embodiment of the present application; Figure Six ;

[0047] Figure 14 Fig. 13 is a schematic diagram of a connection circuit of a microphone element according to an embodiment of the present application. DETAILED DESCRIPTION

[0048] The embodiments of the present application will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0049] It should be noted that the terms "first", "second" and the like in the description and claims of the present application and the above drawings are used to distinguish similar objects, and do not necessarily have to describe a specific order or sequence.

[0050] In the present embodiment, a piezoelectric MEMS microphone is provided, Figure 1 is a structural diagram of a piezoelectric MEMS microphone according to an embodiment of the present application Figure One As shown in the figure, it comprises a first piezoelectric cantilever beam 102 and a second piezoelectric cantilever beam 104, wherein the first piezoelectric cantilever beam 102 is used to convert the received sound signal into a first electric signal A, and the second piezoelectric cantilever beam 104 is used to convert the received sound signal into a second electric signal B; the first electric signal A and the second electric signal B are opposite in phase. Figure 1 Through the above structure, the piezoelectric MEMS microphone comprises two types of piezoelectric cantilever beams, i.e. the first piezoelectric cantilever beam and the second piezoelectric cantilever beam, which are arranged alternately, and can respectively convert the received sound signal into electric signals opposite in phase, so that the signals of the piezoelectric MEMS microphone can form differential signals, and then the differential mode signal and the common mode signal are processed by the differential amplification circuit, thereby suppressing the background noise, and the piezoelectric MEMS microphone can output signals with higher signal-to-noise ratio and resolution. Therefore, the problem of poor signal quality of the piezoelectric MEMS microphone can be solved, and the pickup effect of the piezoelectric MEMS microphone can be improved.

[0051] Optionally, in the present embodiment, the number of first piezoelectric cantilever beams is equal to the number of second piezoelectric cantilever beams, and the distribution mode of the first piezoelectric cantilever beams and the second piezoelectric cantilever beams can be staggered adjacent arrangement, or can also be random distribution.

[0052] Optionally, in the present embodiment, the first piezoelectric cantilever beam can also be referred to as the first type of piezoelectric cantilever beam, and the second piezoelectric cantilever beam can also be referred to as the second type of piezoelectric cantilever beam, the number of the first type of piezoelectric cantilever beam and the second type of piezoelectric cantilever beam is the same, and they are arranged alternately to form a working area, thereby forming a piezoelectric MEMS microphone with a single piezoelectric diaphragm, the first type of piezoelectric cantilever beam and the second type of piezoelectric cantilever beam output two types of electric signals opposite in phase, i.e. the first electric signal and the second electric signal, thereby forming a piezoelectric MEMS microphone realizing differential output through a single piezoelectric diaphragm.

[0053]

[0054] ​The piezoelectric diaphragm of the working area of the piezoelectric MEMS microphone is divided into two types of regions, the two types of regions are the same number and staggered arrangement, and the two types of regions output phase-opposite electric signals, thereby forming a differential output of the signal. Or, in a single working area, a plurality of piezoelectric cantilever beams output half of the signal A and the other half of the signal B for differential output.

[0055] Optionally, in the embodiment, the working area is a symmetrical structure, which can be an axisymmetric structure or a center-symmetric structure. The working area can be, but is not limited to, a circular area, an octagonal area, or a polygonal area with an even number of sides.

[0056] Optionally, in the embodiment, the first electric signal and the second electric signal are phase-opposite. For example, the first electric signal is a positive voltage, and the second electric signal is a negative voltage. Or, the first electric signal is a negative voltage, and the second electric signal is a positive voltage. The magnitudes of the first electric signal and the second electric signal are not necessarily equal, which can be equal or not equal.

[0057] Optionally, in the embodiment, the first sound signal is a sound signal received on the first piezoelectric cantilever beam, and the second sound signal is a sound signal received on the second piezoelectric cantilever beam. The first sound signal and the second sound signal can be the same or different.

[0058] Optionally, in the embodiment, the diaphragm structure of the piezoelectric MEMS microphone can include, but is not limited to, a piezoelectric single crystal wafer or a piezoelectric double crystal wafer, etc.

[0059] Optionally, in the embodiment, the first piezoelectric cantilever beam and the second piezoelectric cantilever beam can form phase-opposite electric signals through opposite electrode lead-out modes.

[0060] In an example embodiment, the first piezoelectric cantilever beam and the second piezoelectric cantilever beam are both piezoelectric single crystal wafers, wherein the piezoelectric single crystal wafer includes 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; and the second piezoelectric cantilever beam outputs the second electric signal through the top electrode, and the bottom electrode is grounded.

[0061] Optionally, in the present embodiment, if the piezoelectric cantilever beams deployed on the piezoelectric MEMS microphone are all piezoelectric single wafer structures, i.e., the piezoelectric MEMS microphone uses a piezoelectric diaphragm of a piezoelectric single wafer structure, the two types of piezoelectric cantilever beams can but are not limited to adopt opposite electrode leading modes to form electric signals of opposite phases. The first piezoelectric cantilever beam can output a first electric signal with the bottom electrode of the piezoelectric single wafer as a terminal and the top electrode grounded. The second piezoelectric cantilever beam can output a second electric signal with the top electrode of the piezoelectric single wafer as a terminal and the bottom electrode grounded.

[0062] In an optional embodiment, an example of a diaphragm structure of a piezoelectric MEMS microphone using a piezoelectric single wafer structure is provided. Figure 2 is a schematic diagram of a piezoelectric MEMS microphone with a diaphragm structure using a piezoelectric single wafer structure according to an optional embodiment of the present application, as Figure 2 shown, the piezoelectric single wafer 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 A-type cantilever beam (i.e., the second piezoelectric cantilever beam described above) is grounded and the top electrode 204 is a terminal, then the corresponding B-type cantilever beam (i.e., the first piezoelectric cantilever beam described above) has the bottom electrode 202 as a terminal and the top electrode 204 grounded.

[0063] In an exemplary embodiment, the first piezoelectric cantilever beam and the second piezoelectric cantilever beam are both piezoelectric double wafer structures, wherein the piezoelectric double wafer structure includes 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.

[0064] Optionally, in the present embodiment, if the piezoelectric cantilever beams deployed on the piezoelectric MEMS microphone are all piezoelectric double wafer structures, i.e., the piezoelectric MEMS microphone uses a piezoelectric diaphragm of a piezoelectric double wafer structure, the two types of piezoelectric cantilever beams can but are not limited to adopt opposite electrode leading modes to form electric signals of opposite phases. The first piezoelectric cantilever beam can output a first electric signal with the lower electrode and the upper electrode of the piezoelectric double wafer as terminals and the middle layer electrode grounded. The second piezoelectric cantilever beam can output a second electric signal with the middle layer electrode of the piezoelectric double wafer as a terminal and the lower electrode and the upper electrode grounded.

[0065] In an optional embodiment, an example of a diaphragm structure of a piezoelectric MEMS microphone using a piezoelectric double wafer structure is provided. Figure 3is a schematic diagram of a piezoelectric MEMS microphone according to an alternative embodiment of the present application, which is a diaphragm structure using a piezoelectric bimorph structure, as shown in Figure 3 The piezoelectric bimorph includes a lower electrode 301, a first piezoelectric film 302, a middle electrode 303, a second piezoelectric film 304, and an upper electrode 305. If the lower electrode 301 and the upper electrode 305 of the A-type cantilever beam (i.e., the first piezoelectric cantilever beam) are terminated, and the middle electrode 303 is grounded, the middle electrode 303 of the B-type cantilever beam (i.e., the second piezoelectric cantilever beam) corresponding thereto is terminated, and the lower electrode 301 and the upper electrode 305 are grounded.

[0066] 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 piezoelectric cantilever beam and the second piezoelectric cantilever beam, and the other end of each of the first piezoelectric cantilever beam and the second piezoelectric cantilever beam forms a free end.

[0067] Optionally, in the present embodiment, the piezoelectric MEMS microphone can, but is not limited to, form a vibratable structure with one end fixed and one end free for each piezoelectric cantilever beam through the fixed boundary.

[0068] In an exemplary embodiment, Figure 4 is a structural schematic diagram of a piezoelectric MEMS microphone according to an embodiment of the present application, Figure Two As shown in Figure 4 The first piezoelectric cantilever beam and the second piezoelectric cantilever beam form a working area 402 of the piezoelectric MEMS microphone, wherein the fixed boundary 404 is arranged at the outer periphery of the working area 402 (as shown by the solid fixed boundary 404 in Figure 4 ), or the fixed boundary 404 is arranged at the middle of the working area 402 (as shown by the dashed fixed boundary 404 in Figure 4 ).

[0069] Optionally, in the present embodiment, the piezoelectric MEMS microphone can adopt a peripheral fixing method or a middle fixing method for the piezoelectric cantilever beam.

[0070] In an alternative embodiment, a piezoelectric MEMS microphone capable of reducing the background noise and improving the signal-to-noise ratio (SNR) is provided. Figure 5 is a schematic diagram of a piezoelectric MEMS microphone according to an alternative embodiment of the present application, which is a diaphragm structure using a piezoelectric bimorph structure, as shown in Figure 5As shown, the piezoelectric MEMS microphone structure includes first type of cantilever beam 501, second type of cantilever beam 502 and fixed boundary 503, which is arranged at the outer periphery of the working area. The first type of cantilever beam 501 and the second type of cantilever beam 502 respectively output A signal and B signal, and the number of the two is the same. The overall working area of the piezoelectric MEMS microphone can be circular, octagonal and various even-sided polygon.

[0071] In one example embodiment, Figure 6 Figure 1 is a structural schematic diagram of a piezoelectric MEMS microphone according to an embodiment of the present application. Figure Three As shown in Figure 1, the piezoelectric MEMS microphone includes a plurality of piezoelectric cantilever beams 101 and a fixed boundary 102 arranged at the outer periphery of the working area. Figure 6 As shown, in the case where the fixed boundary 602 is arranged at the middle part 604 of the working area, the piezoelectric MEMS microphone further includes a connecting support 606, wherein the connecting support 606 is arranged between every two piezoelectric cantilever beams, and each piezoelectric cantilever beam is anchored at the outer periphery 608 of the working area through the connecting support 606.

[0072] Optionally, in the present embodiment, if the fixed boundary is arranged at the middle part of the working area, the connecting support can also be arranged between every two piezoelectric cantilever beams so that each piezoelectric cantilever beam is anchored at the outer periphery of the working area through the connecting support. On the one hand, it plays a role in fixing the piezoelectric cantilever beam, and on the other hand, the end of the piezoelectric cantilever beam with larger area becomes a free end that can vibrate, so that the output signal under unit sound pressure is larger, the sensitivity is higher, and it is more conducive to the miniaturization of the MEMS microphone and the improvement of SNR.

[0073] In one optional embodiment, a piezoelectric MEMS microphone with a fixed boundary arranged at the middle part of the working area is provided. Figure 7 Figure 1 is a structural schematic diagram of a piezoelectric MEMS microphone according to an embodiment of the present application. Figure 7 As shown, the fixed boundary 705 is arranged at the middle part of the working area, and a plurality of piezoelectric cantilever beams are anchored at the outer periphery non-working area 703 through the connecting support 704, and the first type of cantilever beam 701 and the second type of cantilever beam 702 are staggered to output differential signals. When the end of the piezoelectric cantilever beam with larger area is a free end, the output signal under unit sound pressure is larger, the sensitivity is higher, and it is conducive to the miniaturization of the overall structure and the improvement of signal-to-noise ratio.

[0074] In one example embodiment, Figure 8 Figure 1 is a structural schematic diagram of a piezoelectric MEMS microphone according to an embodiment of the present application. Figure Four As shown in Figure 1, the piezoelectric MEMS microphone includes a plurality of piezoelectric cantilever beams 101 and a fixed boundary 102 arranged at the outer periphery of the working area. Figure 8As shown, the piezoelectric MEMS microphone further comprises a flexible structure 802, wherein each piezoelectric cantilever beam is connected to the connecting support 804 through the flexible structure 802; the flexible structure 802 controls the synchronous vibration of the piezoelectric cantilever beam in the working area.

[0075] Optionally, in the embodiment, the number of flexible structures between each piezoelectric cantilever beam and the connecting support can be one or more, but is not limited to. The flexible structure can not limit the vibration while ensuring the synchronous vibration of the working area, and can be a low stiffness structure with a spring coefficient k, but is not limited to. For example, in the micro-nano preparation process, due to the different residual stresses of the thin film layers, if the stresses cannot be balanced and offset, the cantilever beams will be warped to different degrees, the synchronous vibration of the combined cantilever beam cannot be guaranteed, the A and B signals will have phase deviation, and the purpose of differential amplification signal cannot be achieved. The n "Z" type flexible structures arranged at each position adjacent to the connecting support of the free end of the cantilever beam can interconnect the cantilever beam and the connecting support, reduce the vibration cross talk, and ensure the synchronous vibration of the combined cantilever beam.

[0076] Optionally, in the embodiment, the flexible structure can be any shape that can achieve the above functions, such as "Z" shape or "π" shape. Figure 9 is a schematic diagram of a flexible structure shape according to an embodiment of the present application Figure One As shown in Figure 9 The connecting structure similar to (a) "Z" shape or (b) "π" shape is added to the edge of the free end of the cantilever beam, and the spring coefficient is k. Two anchor points of each flexible structure are arranged on the piezoelectric cantilever beam and the connecting support.

[0077] Figure 10 is a schematic diagram of a flexible structure shape according to an embodiment of the present application Figure Two As shown in Figure 10 Taking the "Z" type connecting structure as an example, the flexible structure can be in the form of the first type of flexible structure 1001 or the second type of flexible structure 1002, and the flexible structure connects the piezoelectric cantilever beam and the connecting support 1004. The combined cantilever beam with 2m degrees of freedom in the longitudinal direction is connected into a whole through a plurality of low stiffness connecting structures with a spring coefficient k, the overall stiffness and stability of the piezoelectric cantilever beam are increased, the size and number of the flexible structure can be adjusted according to the working requirements of the microphone, the resonant frequency and the acoustic pressure overload point (AOP) of the microphone can be adjusted. The addition of the flexible structure can ensure the phase synchronization of the displacement function of the combined cantilever beam, stably output the differential signal of the device, and can suppress the torsional vibration mode of the fan-shaped or inverted trapezoidal piezoelectric cantilever beam, and reduce the output of the cross talk signal.

[0078] In addition to the electrode terminal setting, a better differential signal can be obtained by controlling the synchronous vibration of the combined diaphragm, i.e. the displacement function is in phase. The main frequency of the MEMS microphone is less than 10 kHz, and the wavelength of the sound wave is much larger than the size (about 1 mm) of the microphone device. Within the effective working area of the MEMS microphone, the sound wave can be regarded as a uniform plane wave. To make the combined diaphragm vibrate synchronously, the structure can be completely symmetrical (axially symmetrical or centrally symmetrical), and the film coating thickness can be uniform and the stress can be balanced during micro-nano processing. Otherwise, the combined diaphragm can be deformed irregularly or warped due to residual stress when not working. 2

[0079] Since the residual stress in micro-nano processing cannot be completely eliminated, the above additional technical means can be used to add a low-rigidity connecting structure (i.e. a flexible structure) to the free end of each cantilever beam, so that the multiple cantilever beams are anchored to the same fixed frame. The purpose is to limit the degrees of freedom of the combined cantilever beam, and will not greatly suppress the vibration of the cantilever beam. The connecting structure can be a "Z" shape, a "π" shape, etc. 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 the one hand, it can reduce the warping of the diaphragm caused by residual stress in the micro-nano process preparation process. On the other hand, it can ensure that the two signals output by the microphone are opposite in phase, which is beneficial to subsequent differential amplification.

[0080] In an example embodiment, Figure 11 is a structure diagram of a piezoelectric MEMS microphone according to an embodiment of the present application Figure Five As shown in Figure 11 , the piezoelectric MEMS microphone further comprises 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 the electrode on the first piezoelectric cantilever beam for outputting the first electric signal; the second signal port 1104 is connected to the electrode on the second piezoelectric cantilever beam for outputting the second electric signal; and the ground signal port 1106 is connected to the ground electrode on the first piezoelectric cantilever beam and the second piezoelectric cantilever beam.

[0081] Optionally, in the embodiment, the first electric signal is led out through the first signal port, the second electric signal is led out through the second signal port, and the ground electrode on the piezoelectric cantilever beam is led out through the ground signal port, thereby forming a piezoelectric MEMS microphone with three-channel differential output realized by a single piezoelectric diaphragm.

[0082] In an optional embodiment, a piezoelectric MEMS microphone with three-channel differential output is provided. Figure 12 ​This is a schematic diagram of a three-channel differential output piezoelectric MEMS microphone according to an optional embodiment of this application, as shown below. Figure 12 As shown, in (1), the wiring of signal A and signal B is symmetrically distributed. The differential output piezoelectric MEMS microphone outputs through 3 ports, including signal A channel 1201, signal B channel 1202, and ground terminal 1203. Taking the piezoelectric bicrystalline electrode lead-out as an example, (2) and (3) are the lead-out methods of the terminal signal and ground terminal. The insulating layer 1206 is used to protect the electrode layer, and the lower electrode 1204 and upper electrode 1205 are led out as the signal A channel 1201 or ground terminal 1203. The middle layer electrode 1207 is led out as the signal B channel 1202 or ground terminal 1203. The common ground of signal A and signal B ultimately forms a 3-port differential output.

[0083] In one exemplary embodiment, Figure 13 This is a schematic diagram of the structure of a piezoelectric MEMS microphone according to an embodiment of this application. Figure Six ,like Figure 13 As shown, the piezoelectric MEMS microphone further includes a differential amplifier circuit 1302, wherein the differential amplifier circuit 1302 includes a first input terminal 1304, a second input terminal 1306, and an output terminal 1308. The first input terminal 1304 is connected to the first signal port 1102, and the second input terminal 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; differential operations are performed on the first amplified signal and the second amplified signal to obtain a differential signal; and the differential signal is output from the output terminal.

[0084] Optionally, in this embodiment, the 2m piezoelectric cantilever beams are configured as two parts, where m piezoelectric cantilever beams output signal A and the other m piezoelectric cantilever beams output signal B. The differential mode signal in signal A and signal B is mainly the useful signal, and the common mode signal is mainly common mode noise. After passing through the amplifier circuit and the subtraction circuit in the differential amplifier circuit, the output signal is effectively enhanced and the common mode noise is effectively suppressed.

[0085] Optionally, in this embodiment, the above-mentioned piezoelectric MEMS microphone differential output technology can effectively improve SNR and reduce nonlinear distortion. Compared with microphone structures such as dual-diaphragm and backplate three-layer differential capacitor microphones, it has the advantages of simple structure, low micro-nano processing cost, and is conducive to the miniaturization of microphone devices.

[0086] In an alternative implementation, a connection circuit for a three-channel differential output piezoelectric MEMS microphone element is provided. Figure 14is a schematic diagram of a connection circuit of a microphone element according to an alternative embodiment of the present application, as Figure 14 As shown, the microphone element can be any of the above-described piezoelectric MEMS microphone elements, the differential output piezoelectric MEMS microphone element matches the back-end differential amplification circuit, the sound wave signal is input into the microphone element, the output signals A and B are amplified through the two ports of the operational amplifier, and different amplification gain ratios can be obtained by adjusting R1, R2, R3, and Rf. The differential mode signal is enhanced and the common mode noise signal is suppressed by subtracting the two sets of amplified signals at the output end, the SNR of the entire microphone can be effectively improved, and the nonlinear distortion is suppressed.

[0087] Through the above structure, the differential output of the microphone signal can be realized by combining the piezoelectric diaphragm, the differential mode signal is enhanced, the common mode noise signal is suppressed, the sensitivity and signal-to-noise ratio (SNR) of the piezoelectric MEMS microphone can be effectively improved without increasing the working area. And the fixed boundary is adjusted to the middle of the working area by the above-mentioned connecting bracket, and the flexible structure such as "Z" shape is arranged at the edge of the free end of the cantilever beam and interconnected with the connecting bracket, which improves the sensitivity under unit sound pressure, suppresses the problems such as diaphragm warping and vibration out of sync caused by uneven residual stress, ensures the vibration of multiple cantilever beams in phase, effectively suppresses the nonlinear distortion caused by vibration crosstalk, and stably outputs the differential signal. The piezoelectric MEMS microphone structure proposed above improves the sensitivity, signal-to-noise ratio, and response linearity of the piezoelectric MEMS microphone.

[0088] Obviously, those skilled in the art should understand that the modules or steps of the present application described above can be realized by general computing devices, which can be concentrated on a single computing device or distributed on a network composed of multiple computing devices, and they can be realized by program codes executable by computing devices, so that they can be stored in storage devices and executed by computing devices, and in some cases, the steps shown or described can be executed in different order, or they can be manufactured into individual integrated circuit modules, or multiple modules or steps can be manufactured into a single integrated circuit module. Thus, the present application is not limited to any specific combination of hardware and software.

[0089] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Those skilled in the art can make various modifications and changes to the present application. Any modification, equivalent replacement, improvement, etc. made within the principles of the present application shall be included in the protection scope of the present application.

Claims

1. A piezoelectric MEMS microphone, characterized in that, include: The first piezoelectric cantilever beam and the second piezoelectric cantilever beam are of equal number and are arranged alternately and adjacently. The first piezoelectric cantilever beam is used to convert the received sound signal into a first electrical signal, and the second piezoelectric cantilever beam is used to convert the received sound signal into a second electrical signal. The first electrical signal is out of phase with the second electrical signal; 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 to the electrode on the first piezoelectric cantilever beam that outputs the first electrical signal; the second signal port is connected to the electrode on the second piezoelectric cantilever beam that outputs the second electrical signal; and the ground signal port is connected to the grounded electrodes on the first piezoelectric cantilever beam and the second piezoelectric cantilever beam. The piezoelectric MEMS microphone further includes a differential amplifier circuit, wherein the differential amplifier circuit includes a first input terminal, a second input terminal, and an output terminal, the first input terminal is connected to the first signal port, and the second input terminal is connected to the second signal port; the differential amplifier circuit amplifies the first electrical signal to obtain a first amplified signal, and amplifies the second electrical signal to obtain a second amplified signal; differential operation is performed on the first amplified signal and the second amplified signal to obtain a differential signal; and the differential signal is output from the output terminal.

2. The piezoelectric MEMS microphone according to claim 1, characterized in that, Both the first and second piezoelectric cantilever beams are piezoelectric single-crystal wafers, wherein... The piezoelectric single crystal wafer includes: a substrate, a bottom electrode, a piezoelectric thin film, and a top electrode; The first piezoelectric cantilever beam outputs the first electrical signal through the bottom electrode, and the top electrode is grounded; The second piezoelectric cantilever beam outputs the second electrical signal through the top electrode, and the bottom electrode is grounded.

3. The piezoelectric MEMS microphone according to claim 1, characterized in that, Both the first and second piezoelectric cantilever beams are piezoelectric bicrystalline wafers, wherein... The piezoelectric bicrystalline wafer includes: a lower electrode, a first piezoelectric thin film, a middle electrode, a second piezoelectric thin film, and an upper electrode; The first piezoelectric cantilever beam outputs the first electrical signal through the lower electrode and the upper electrode, and the middle layer electrode is grounded; The second piezoelectric cantilever beam outputs the second electrical signal through the middle layer electrode, and the lower electrode and the upper electrode are grounded.

4. The piezoelectric MEMS microphone according to claim 1, characterized in that, Also includes: Fixed boundary, where, The fixed boundary fixes one end of each of the first and second piezoelectric cantilever beams, while the other end of each piezoelectric cantilever beam becomes a free end.

5. The piezoelectric MEMS microphone according to claim 4, characterized in that, The first piezoelectric cantilever beam and the second piezoelectric cantilever beam form the working area of ​​the piezoelectric MEMS microphone, wherein... The fixed boundary is located on the outer periphery of the working area, or the fixed boundary is located in the middle of the working area.

6. The piezoelectric MEMS microphone according to claim 5, characterized in that, With the fixed boundary located in the middle of the working area, the piezoelectric MEMS microphone further includes: a connecting bracket, wherein, The connecting bracket is disposed between every two piezoelectric cantilever beams, and each piezoelectric cantilever beam is anchored to the outer periphery of the working area via the connecting bracket.

7. The piezoelectric MEMS microphone according to claim 6, characterized in that, Also includes: Flexible structures, among which, Each piezoelectric cantilever beam is connected to the connecting bracket via the flexible structure; The flexible structure controls the synchronous vibration of the piezoelectric cantilever beam within the working area.

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