Double-face-driven piezoelectric micro-electro-mechanical system loudspeaker and electronic equipment

Abstract

The double-face-driven piezoelectric micro electro mechanical system loudspeaker comprises a substrate with a concave cavity, a supporting layer, a framework layer and an acoustic unit, the acoustic unit is arranged on the framework layer, and the acoustic unit comprises a first vibrating diaphragm and a second vibrating diaphragm; the supporting layer is arranged on the outer surface of the substrate, a framework layer stretching across the opening direction of the concave cavity of the substrate is arranged on the supporting layer, a first vibrating diaphragm is arranged on the lower surface of the framework layer, and a second vibrating diaphragm is arranged on the upper surface of the framework layer; the first vibrating diaphragm comprises a first sandwich structure, and the second vibrating diaphragm comprises a second sandwich structure. The thickness of the piezoelectric layer and the thickness of the framework layer are set, the output sound pressure level and sensitivity of the piezoelectric micro-electro-mechanical system loudspeaker are improved, the sound pressure output efficiency of the piezoelectric micro-electro-mechanical system loudspeaker is improved, meanwhile, the reliability and manufacturing consistency of the piezoelectric micro-electro-mechanical system loudspeaker are improved, meanwhile, the piezoelectric micro-electro-mechanical system loudspeaker has better high-frequency response compared with existing multiple schemes, and the application range is wide. And thus, the full-bandwidth response is better.

Description

TECHNICAL FIELD

[0001] The present application relates to a piezoelectric micro-electro-mechanical system (MEMS) loudspeaker and electronic equipment, and more particularly, to a piezoelectric micro-electro-mechanical system (MEMS) loudspeaker with a double-sided driving structure and electronic equipment. BACKGROUND

[0002] The piezoelectric micro-electro-mechanical system (MEMS) ultrasonic transducer has the advantages of easy mass production, compatibility with CMOS (Complementary Metal-Oxide-Semiconductor), and other advantages that traditional ultrasonic transducers cannot have. However, the current development of the piezoelectric micro-electro-mechanical system (MEMS) ultrasonic transducer has encountered the problem of difficulty in obtaining high sensitivity.

[0003] The current piezoelectric MEMS ultrasonic transducer needs to achieve the following goals:

[0004] 1. Higher output sound pressure level with smaller driving voltage;

[0005] 2. Higher output sound pressure level with smaller driving power.

[0006] Some solutions to this problem have been proposed previously, such as mechanically decoupling the complete diaphragm into a multi-lobe structure to obtain higher degrees of freedom, or using a four-side cantilever beam to drive the center diaphragm to achieve piston vibration mode. These solutions have good effects on improving vibration displacement, but in essence, they all sacrifice the forward resonance frequency as a trade-off. However, the resonance frequency is one of the design indicators and cannot be arbitrarily selected. The existing solutions are a trade-off between sensitivity and resonance frequency, and often one is lost for the other.

[0007] The current piezoelectric MEMS ultrasonic transducer has the following significant problems:

[0008] 1. Sensitivity and resonance frequency are traded off, there is no unified evaluation standard and formula to ensure sensitivity and resonance frequency at the same time.

[0009] 2. The diaphragm of the MEMS ultrasonic transducer is relatively thin, and the equivalent mechanical stiffness is low, which is prone to breakage during use, especially under impact, and the device reliability is low.

[0010] 3. The sensitivity of MEMS ultrasonic transducers is not only related to the planar structure design, but also to the thickness of the membrane layer. The unoptimized thickness of the piezoelectric layer and the thickness ratio of the piezoelectric layer to other membrane layers are one of the main reasons for the low sensitivity of MEMS transducers made of piezoelectric thin films. On the other hand, the manufacturing method of piezoelectric MEMS transducers will also limit the range of film thickness options. For example, piezoelectric MEMS transducers based on cavity SOI have requirements for the minimum thickness of the diaphragm, such as greater than 1 micron. However, a thicker diaphragm thickness will reduce the sensitivity of the transducer.

[0011] Therefore, the problems existing in the prior art need to be further improved and developed. Summary of the Invention

[0012] (1) Purpose of the Invention: To solve the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a piezoelectric MEMS speaker with an optimized piezoelectric layer thickness and a thickness ratio between the piezoelectric layer and other film layers.

[0013] 18. (II) Technical Solution: To address the above-mentioned technical issues, this technical solution provides a double-sided driven piezoelectric MEMS loudspeaker comprising a substrate with a concave cavity, a support layer, a skeleton layer, and an acoustic unit, wherein the acoustic unit is disposed on the skeleton layer, wherein:

[0014] The acoustic unit includes a first diaphragm and a second diaphragm;

[0015] The supporting layer is arranged on the outer surface of the substrate, and a skeleton layer is arranged on the supporting layer and spans the opening direction of the concave cavity of the substrate. A first diaphragm is arranged on the lower surface of the skeleton layer, and a second diaphragm is arranged on the upper surface of the skeleton layer; the first diaphragm includes a first sandwich structure having a first piezoelectric layer, and the second diaphragm includes a second sandwich structure having a second piezoelectric layer.

[0016] The double-sided driven piezoelectric MEMS speaker, wherein the first sandwich structure includes a first bottom electrode, a first piezoelectric layer, and a first top electrode, and the second sandwich structure includes a second bottom electrode, a second piezoelectric layer, and a second top electrode.

[0017] In the double-sided driven piezoelectric MEMS loudspeaker, the thickness of the skeleton layer is less than or equal to 1 micron, and the thickness of the first piezoelectric layer and the second piezoelectric layer is less than or equal to 0.5 micron.

[0018] The double-sided driven piezoelectric MEMS speaker, wherein a figure of merit (FOM) value representing the acoustic characteristics of the piezoelectric MEMS speaker is set, and the FOM value calculation formula is as follows:

[0019]

[0020] wherein γ represents the specific heat capacity ratio of air; P0 represents atmospheric pressure; S represents the diaphragm area; E P represents the Young's modulus of the piezoelectric layer material; d 31 represents the piezoelectric coefficient of the piezoelectric layer material; U represents the driving voltage; V 711 represents the volume of the artificial ear; p P represents the density of the piezoelectric layer material; p n represents the density of the skeleton layer; t p represents the total thickness of the two piezoelectric layers; t n represents the thickness of the skeleton layer.

[0021] The double-sided driven piezoelectric micro-electro-mechanical system loudspeaker, wherein the piezoelectric layer material is PZT, the specific heat capacity ratio γ of air, the atmospheric pressure P0, the Young's modulus E P of the PZT layer material, the piezoelectric coefficient d 31 of the PZT layer, the driving voltage U, the volume of the artificial ear V 711 , the density p P of the PZT layer material, and the density p n of the skeleton layer are substituted into the figure of merit FOM value formula to obtain the figure of merit FOM value formula of the loudspeaker containing the PZT layer:

[0022]

[0023] wherein S represents the diaphragm area; t p represents the total thickness of the two piezoelectric layers; t n represents the thickness of the skeleton layer.

[0024] The double-sided driven piezoelectric micro-electro-mechanical system loudspeaker, wherein the logarithm of the figure of merit FOM value represents the sound pressure level under a certain resonance frequency:

[0025] log(FOM) = 20*log 10 (P*f).

[0026] The double-sided driven piezoelectric micro-electro-mechanical system loudspeaker, wherein the logarithm log(FOM) of the figure of merit FOM value is greater than 112.

[0027] The double-sided driven piezoelectric micro-electro-mechanical system loudspeaker, wherein the logarithm log(FOM) of the figure of merit FOM value is greater than 118.

[0028] The double-sided driven piezoelectric micro-electro-mechanical system loudspeaker, wherein the single-layer piezoelectric layer thickness is less than or equal to 0.25 microns.

[0029] The double-sided driving piezoelectric MEMS speaker, wherein the material of the skeleton layer comprises monocrystalline silicon, polycrystalline silicon, silicon oxide or silicon nitride; and the support layer is a non-conductive material or an amorphous material.

[0030] The double-sided driving piezoelectric MEMS speaker, wherein the material of the support layer comprises silicon dioxide and silicon nitride.

[0031] The double-sided driving piezoelectric MEMS speaker, wherein the support layer comprises a continuous stepped structure for bearing the first sandwich structure of the skeleton layer and the first diaphragm.

[0032] The double-sided driving piezoelectric MEMS speaker, wherein the stepped structure comprises three steps successively lowered towards the inside of the cavity, the top layer plane of the stepped structure is used for bearing the skeleton layer, the first step bears the first bottom electrode of the first sandwich unit, and the second step bears the first piezoelectric layer and the first top electrode of the first sandwich unit.

[0033] The double-sided driving piezoelectric MEMS speaker, wherein a second protective film is arranged at the connection between the support layer and the first diaphragm, and a first protective film is arranged at the connection surface between the first diaphragm and the concave cavity of the substrate.

[0034] The double-sided driving piezoelectric MEMS speaker, wherein the first protective film and the second protective film are passivation layers, and the material of the first protective film and the second protective film comprises silicon nitride.

[0035] The double-sided driving piezoelectric MEMS speaker, wherein the skeleton layer is a planar structure.

[0036] The double-sided driving piezoelectric MEMS speaker, wherein the first piezoelectric layer and the second piezoelectric layer are planar structures.

[0037] The double-sided driving piezoelectric MEMS speaker, wherein the first piezoelectric layer and the first bottom electrode and the first top electrode are surrounded and covered by the support layer at the end surface of the root side of the acoustic unit.

[0038] The double-sided driving piezoelectric MEMS speaker, wherein a second protective film is arranged at the connection between the support layer and the first diaphragm, and a first protective film is arranged at the connection surface between the first diaphragm and the concave cavity of the substrate.

[0039] The double-sided driving piezoelectric MEMS speaker, wherein the first protective film and the second protective film are passivation layers, and the material of the first protective film and the second protective film comprises silicon nitride.

[0040] The double-sided driving piezoelectric micro-electro-mechanical system loudspeaker, wherein the first protective film covers the continuous stepped structure surface of the support layer; the end surface of the first diaphragm at the root side thereof, and the first top electrode lower surface of the first sandwich structure of the first diaphragm are a continuous surface layer protective film.

[0041] The double-sided driving piezoelectric micro-electro-mechanical system loudspeaker, wherein the second protective film covers the continuous stepped structure surface of the support layer, and separates the support layer and the concave cavity.

[0042] An electronic device comprising a processor, a memory, a communication interface and a communication bus, the processor, the memory and the communication interface complete communication with each other through the communication bus, and the processor is connected with any one of the double-sided driving piezoelectric micro-electro-mechanical system loudspeakers.

[0043] (Three) beneficial effects: the double-sided driving piezoelectric micro-electro-mechanical system loudspeaker provided by the application sets the thickness of the piezoelectric layer and the skeleton layer, improves the output sound pressure level and sensitivity of the piezoelectric micro-electro-mechanical system loudspeaker, improves the efficiency of the output sound pressure, and improves the reliability and manufacturing consistency of the piezoelectric micro-electro-mechanical system loudspeaker, and has better high-frequency response than many existing schemes, that is, better full-bandwidth response. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 It is the merit distribution diagram of the piezoelectric layer and the skeleton layer of the double-sided driving piezoelectric micro-electro-mechanical system loudspeaker of the application at different thicknesses;

[0045] Figure 2 It is a schematic view of the top view of the double-sided driving piezoelectric micro-electro-mechanical system loudspeaker of the application;

[0046] Figure 3 It is a longitudinal sectional view of the double-sided driving piezoelectric micro-electro-mechanical system loudspeaker of the application in the OA direction;

[0047] Figure 4 It is a first structure schematic view of the double-sided driving piezoelectric micro-electro-mechanical system loudspeaker of the application with a protective film structure;

[0048] Figure 5 It is a second structure schematic view of the double-sided driving piezoelectric micro-electro-mechanical system loudspeaker of the application with a protective film structure;

[0049] Figure 6 It is a structure schematic view of an electronic device with a double-sided driving piezoelectric micro-electro-mechanical system loudspeaker of the application. DETAILED DESCRIPTION

[0050] The application will be described in further detail below with reference to the preferred embodiments. The following description is presented to enable any person skilled in the art to make or use the application. Descriptions of specific embodiments are included for purposes of illustration only and are not intended to be limiting of the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without the use of the inventive faculty. Therefore, the present application is not intended to be limited to the embodiments described herein but is to be accorded the widest scope consistent with the claims.

[0051] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the principles of the application. The drawings are intended for illustrative purposes and should not be considered to limit the scope of the present application.

[0052] The piezoelectric micro-electro-mechanical system loudspeaker provided by the application is driven on both sides, and comprises a substrate with a concave cavity, a support layer, a framework layer and an acoustic unit. The acoustic unit comprises a first diaphragm and a second diaphragm. The outer surface of the substrate is provided with the support layer, the support layer is provided with the framework layer which is transverse to the opening direction of the concave cavity of the substrate, the lower surface of the framework layer is provided with the first diaphragm, and the upper surface of the framework layer is provided with the second diaphragm. The first diaphragm comprises a first sandwich structure with a first piezoelectric layer, and the second diaphragm comprises a second sandwich structure with a second piezoelectric layer. The first sandwich structure comprises a first bottom electrode, a first piezoelectric layer and a first top electrode, and the second sandwich structure comprises a second bottom electrode, a second piezoelectric layer and a second top electrode. The framework layer, the first diaphragm and the second diaphragm arranged above and below are collectively referred to as a diaphragm, that is, the acoustic unit.

[0053] The thickness of the framework layer is less than or equal to 1 micrometer, and the thickness of the first piezoelectric layer and the second piezoelectric layer is less than or equal to 0.5 micrometer.

[0054] The piezoelectric micro-electro-mechanical system loudspeaker provided by the application is driven on both sides, and comprises a first diaphragm and a second diaphragm.

[0055] The application defines a figure of merit representing the acoustic performance of the piezoelectric micro-electro-mechanical system loudspeaker, that is, the figure of merit FOM value. The larger the figure of merit, the higher the sound pressure sensitivity of the loudspeaker, the better the performance of the output sound pressure, and the better the loudspeaker effect. The figure of merit is described as formula (1):

[0056]

[0057] Wherein, γ represents the specific heat capacity ratio of air; P0 represents atmospheric pressure; S represents the diaphragm area; E P represents the Young's modulus of the piezoelectric layer material; d 31 represents the piezoelectric coefficient of the piezoelectric layer material; U represents the driving voltage; V 711 represents the volume of the simulated ear; pP represents the density of the piezoelectric layer material; ρ n represents the density of the skeleton layer; t p represents the total thickness of the two piezoelectric layers; t n It can be seen from formula (1) that the figure of merit is related to the material of the piezoelectric layer and the thickness of the skeleton layer.

[0058] In the figure of merit formula of the present invention, P represents the quasi-steady-state response sensitivity of the output sound pressure at medium and low frequencies, and f represents the first-order resonant frequency. The product of the two can be used to evaluate the overall performance of a loudspeaker.

[0059] Preferably, the material of the piezoelectric layer of the present invention is single crystal lead zirconate titanate (PZT), and the material of the skeleton layer is silicon Si. Wherein, when the piezoelectric layer material is PZT, the figure of merit FOM value of the loudspeaker including the PZT layer can be obtained by calculating the specific heat capacity ratio γ of air, atmospheric pressure P0, Young's modulus E of the PZT layer material, and the following equations: P , the piezoelectric coefficient d of the PZT layer 31 , driving voltage U, artificial ear volume V 711 , the density of the PZT layer material ρ P and the density of the skeleton layer ρ n Substituting this into the figure of merit FOM value formula, we obtain the following formula (2) for the figure of merit FOM value of the loudspeaker including the PZT layer:

[0060]

[0061] Where S represents the diaphragm area; t p represents the total thickness of the two piezoelectric layers; t n Indicates the thickness of the skeleton layer.

[0062] The present invention can take the logarithm of the figure of merit FOM value to express the sound pressure level at a certain resonant frequency, as shown in formula (3):

[0063] log(FOM)=20*log 10 (P*f) (3)

[0064] The present invention can obtain different figure of merit FOM values ​​by changing the thickness of the piezoelectric layer and the skeleton layer, thereby obtaining a high figure of merit FOM value and improving the performance of the piezoelectric micro-electromechanical system speaker.

[0065] The performance indicators of the double-sided driven piezoelectric micro-electromechanical system speaker structure of the present invention are determined according to the thickness of the piezoelectric layer and the thickness of the skeleton layer. It can effectively improve the quasi-steady-state response sound pressure level of the speaker without changing the resonant frequency. At the same time, it also has a better high-frequency response than many existing solutions, that is, a better full-bandwidth response.

[0066] The piezoelectric micro-electro-mechanical system loudspeaker of the present application is preferably characterized by a log(FOM) greater than 112; further, preferably, a log(FOM) greater than 118, as shown in Figure 1 .

[0067] The piezoelectric layer P100 of the first diaphragm and the piezoelectric layer P200 of the second diaphragm of the present application are preferably of the same thickness. When the piezoelectric layer P100 of the first diaphragm and the piezoelectric layer P200 of the second diaphragm are PZT layers, the piezoelectric layer of the present application is preferably characterized by a figure of merit FOM value less than or equal to 0.5 microns, greater than a figure of merit FOM value of a piezoelectric layer thickness greater than 0.5 microns, as shown in Figure 1 .

[0068] Preferably, the piezoelectric layer of the first diaphragm and the piezoelectric layer of the second diaphragm of the present application are less than or equal to 0.5 microns in thickness, and the sum of the thicknesses of the piezoelectric layer P100 in the first diaphragm and the piezoelectric layer P200 in the second diaphragm is less than or equal to 1 micron.

[0069] Preferably, as shown in Figure 1 , the figure of merit FOM value of the single-layer piezoelectric layer of the present application is less than or equal to 0.25 microns in thickness, greater than a figure of merit FOM value of a single-layer piezoelectric layer thickness greater than 0.25 microns. The degree of influence of the reasonable selection of the thickness of the skeleton layer on the improvement of the FOM value when the thickness of the piezoelectric layer is less than or equal to 0.25 microns is greater than the degree of influence of the change in the thickness of the skeleton layer when the thickness of the piezoelectric layer is greater than 0.25 microns. The thickness of the piezoelectric layer of the first diaphragm and the second diaphragm of the present application is preferably less than or equal to 0.25 microns.

[0070] The first preferred embodiment of the piezoelectric micro-electro-mechanical system loudspeaker of the present application is shown in Figure 2 and Figure 3As shown, the substrate S100 includes a concave cavity, the outer surface of the cavity wall, the outer surface of the substrate S100 is provided with a support layer F200, the support layer F200 is provided with a skeleton layer D100 across the opening direction of the concave cavity of the substrate, and the skeleton layer D100 is provided with an acoustic unit. The acoustic unit includes a second diaphragm provided on the skeleton layer D100, and a first diaphragm provided below the skeleton layer D100. The material of the skeleton layer D100 is generally single crystal silicon, polycrystalline silicon, silicon oxide or silicon nitride, and the thickness is not more than 1 microns. The support layer F200 is generally selected from non-conductive materials or amorphous materials, such as silicon dioxide and silicon nitride. The first diaphragm can be a first sandwich piezoelectric unit, and the second diaphragm can be a second sandwich piezoelectric unit.

[0071] The first sandwich piezoelectric unit is provided on the lower surface of the skeleton layer D100, and the first sandwich piezoelectric unit includes a first bottom electrode B100, a first piezoelectric layer P100, and a first top electrode T100. The first bottom electrode B100 is formed on the lower surface of the skeleton layer D100, the first piezoelectric layer P100 is provided on the lower surface of the first bottom electrode B100, and the first top electrode T100 is provided on the lower surface of the first piezoelectric layer P100.

[0072] The second sandwich piezoelectric unit is provided on the upper surface of the skeleton layer D100, and the second sandwich piezoelectric unit includes a second bottom electrode B200, a second piezoelectric layer P200, and a second top electrode T200. The second bottom electrode B200 is formed on the upper surface of the skeleton layer D100, the second piezoelectric layer P200 is provided on the upper surface of the second bottom electrode B200, and the second top electrode T200 is provided on the upper surface of the second piezoelectric layer P200.

[0073] The first bottom electrode B100, the first piezoelectric layer P100, and the first top electrode T100 of the first sandwich piezoelectric unit, and the second bottom electrode B200 of the second sandwich piezoelectric unit are electrically connected through the metal layers M120, M110, and M100 in the through holes penetrating these structure layers.

[0074] The support layer F200 is used to support the skeleton layer D100 and the first sandwich piezoelectric unit, and the substrate S100 is bonded to the bottom of the support layer F200. Preferably, the support layer F200 includes a continuous stepped structure, and the stepped structure is used to carry the skeleton layer D100 and the first sandwich structure of the first diaphragm. The stepped structure includes a plurality of steps that are sequentially lowered towards the inside of the cavity, and the steps are used to carry the skeleton layer D100 and the first sandwich unit.

[0075] Preferably, the step-like structure can include three steps which are sequentially lower to the inside of the cavity. The top layer of the step-like structure is used to carry the skeleton layer D100, the first step carries the first bottom electrode B100 of the first sandwich unit, the second step carries the first piezoelectric layer P100 and the first top electrode T100 of the first sandwich unit, and the third step is empty. The specific structure of the step layer carrying the first sandwich unit is not limited.

[0076] The step-like structure of the present application is used to carry the lower part near the edge of the first sandwich unit. The concave cavity boundary of the substrate S100 of the present application is located inside the opening boundary line which is in contact with the first top electrode T100 of the first sandwich unit, that is, away from the side of the diaphragm root, so as to ensure the accuracy of the diaphragm size control. The first piezoelectric layer P100, the second piezoelectric layer P200, the first top electrode T100, the second top electrode T200, the first bottom electrode B100, and the second bottom electrode B200 of the present application can completely cover the skeleton layer D100, or partially cover the skeleton layer D100 as the first bottom electrode B100 and the first piezoelectric layer P100 do.

[0077] In order to avoid mechanical fatigue and stress concentration points in the skeleton layer D100 of the diaphragm, and ultimately improve the mechanical reliability of the piezoelectric micro-electro-mechanical system loudspeaker, the skeleton layer D100 is set as a planar structure. In order to avoid the decrease of piezoelectric coefficient and the decrease of electric field breakdown strength due to the bending of the piezoelectric layer, improve the displacement of the diaphragm under the action of electric field excitation and the highest bearing voltage, and ultimately improve the acoustic performance and electrical reliability of the piezoelectric micro-electro-mechanical system loudspeaker, the first piezoelectric layer P100 and the second piezoelectric layer P200 are also set as a planar structure. The planar structure is that there is no step coverage or bending in the thickness direction in the entire structure of the piezoelectric micro-electro-mechanical system loudspeaker. The first piezoelectric layer P100 and the first bottom electrode B100, the first top electrode T100 are surrounded and covered by the support layer F200 at the end face of the diaphragm root, that is, the acoustic unit root side, which can improve the mechanical reliability and electrical reliability of the piezoelectric micro-electro-mechanical system loudspeaker. In the plan view of the diaphragm, the edge part of the diaphragm is called the root of the diaphragm. Because the stress of the diaphragm root is the largest when the diaphragm vibrates to produce sound, and the electrical failure and mechanical failure of the piezoelectric layer and the electrode layer often occur at the end face, the non-conductive amorphous support layer F200 is surrounded and covered to provide larger mechanical support and electrical isolation, and the negative effects of stress concentration effect and end face effect can be greatly reduced.

[0078] The acoustic unit is square as a whole, the diaphragm is divided into four triangular diaphragms by cross-shaped slits, the first triangular diaphragm comprises a first top electrode T200 on the upper layer, the second triangular diaphragm comprises a second top electrode T200a on the upper layer, the third triangular diaphragm comprises a third top electrode T200b on the upper layer, and the fourth triangular diaphragm comprises a fourth top electrode T200c on the upper layer, and the triangular diaphragm comprises four top electrodes of acoustic area surfaces.

[0079] The present application sets several contacts for inputting electrical signals and other electrical connection structures beside the triangular diaphragm of the second diaphragm, as shown in Figure 2 Taking the first triangular diaphragm as an example, the first contact metal layer M101, the second contact metal layer M111, the third contact metal layer M121, and the fourth contact metal layer M131 are distributed on the left side of the edge of the first triangular diaphragm. The fourth contact metal layer M131 is directly connected to the second top electrode T200 through a surface conductor structure. The first contact metal layer M101, the second contact metal layer M111, and the third contact metal layer M121 are connected to the first metal layer M100, the second metal layer M110, and the third metal layer M120 respectively through the surface conductor structure, and the first metal layer M100, the second metal layer M110, and the third metal layer M120 are further connected to the second bottom electrode B200, the first bottom electrode B100, and the first top electrode T100 located in the deep layer, as shown in Figure 3 The contacts and electrical connection structures of the second triangular diaphragm, the third triangular diaphragm, and the fourth triangular diaphragm are the same as those of the first triangular diaphragm, and will not be described here.

[0080] A second preferred embodiment of the piezoelectric micro-electro-mechanical system loudspeaker of the present application is shown in Figure 4 Preferably, a second protective film L200 is arranged at the connection between the support layer and the first diaphragm, and a first protective film L100 is arranged at the connection surface between the first diaphragm and the concave cavity of the substrate. The protective film comprises the first protective film L100 and the second protective film L200, and the protective film is a passivation layer, and the material can be selected from silicon nitride.

[0081] The first protective film L100 covers the continuous step-shaped structure surface of the support layer F200, and the end surface of the first diaphragm on one side of the root thereof and the lower surface of the first top electrode T100 of the first sandwich structure of the first diaphragm are a continuous surface layer protective film. The first protective film L100 achieves the purpose of protecting the first sandwich structure of the first diaphragm by reducing the invasion of corrosive molecules, and the material of the first protective film L100 can be selected from silicon nitride and the like, as shown in Figure 3

[0082] ​The second protective film L200 covers the stepped surface of the support layer F200 continuously, and separates the support layer F200 and the concave cavity (obtained after the filling layer F100 is removed), so that the support layer F200 is not etched when the filling layer F100 is removed, thereby defining the boundary of the obtained concave cavity, as shown in Figure 5 The material of the second protective film L200 can be silicon nitride or the like.

[0083] The double-sided driving piezoelectric micro-electro-mechanical system loudspeaker provided by the application is a composite membrane layer structure formed by a multi-step processing technology. When the filling layer is released to form a slit structure in Figure 2 , stress will cause the composite membrane layer of each small block to warp, and the low-frequency energy absorption will decrease. In order to significantly reduce the deformation of the composite diaphragm structure, the slit in Figures 2-4 is cancelled, so that the first top electrode T200 and the second top electrode T200a, the third top electrode T200b, and the fourth top electrode T200c form an integral diaphragm, which can significantly reduce the deformation of the composite diaphragm structure.

[0084] The material of the first bottom electrode B100 and the second bottom electrode B200 is a composite layer material, and the arrangement order of the composite layer material (from the skeleton layer to the piezoelectric layer) is: zirconium oxide, platinum, SRO or titanium, titanium oxide, platinum, and a buffer layer. The material of the first top electrode T100 and the second top electrode T200 includes but is not limited to molybdenum, platinum, magnesium, aluminum, ruthenium, titanium, iridium, osmium, silver, gold, and alloys or composite layers of the above-mentioned metals. The material of the first piezoelectric layer P100 and the second piezoelectric layer P200 is lead zirconate titanate or doped lead zirconate titanate, which is a PZT layer. Preferably, the thickness of the first piezoelectric layer P100 or the second piezoelectric layer P200 is less than or equal to 0.5 microns.

[0085] According to the figure of merit FOM, the thickness of the first piezoelectric layer P100 and the second piezoelectric layer P200 can also be less than or equal to 0.25 microns, so as to obtain a better figure of merit FOM.

[0086] The double-sided driving piezoelectric micro-electro-mechanical system loudspeaker provided by the application can effectively improve the quasi-steady response sound pressure level of the loudspeaker without changing the resonance frequency. By setting the thickness of the single-layer piezoelectric layer of the double-sided driving loudspeaker to be less than or equal to 0.5 microns, and the sum of the thicknesses of the double-layer piezoelectric layer to be less than or equal to 1 micron. Or more preferably, the thickness of the single-layer piezoelectric layer of the double-sided driving loudspeaker is set to be less than 0.25 microns, and the sum of the thicknesses of the double-layer piezoelectric layer is less than or equal to 0.5 microns. The piezoelectric micro-electro-mechanical system loudspeaker has a higher figure of merit, and has good sound pressure sensitivity, output sound pressure performance, and loudspeaker effect. In addition, the piezoelectric micro-electro-mechanical system loudspeaker can also improve the output pressure of the sound, and improve the reliability of the device.

[0087] The present application improves the output sound pressure level and sensitivity of the piezoelectric micro-electro-mechanical system loudspeaker by setting the thickness of the piezoelectric layer and the skeleton layer, improves the efficiency of the output sound pressure, and improves the reliability and manufacturing consistency of the piezoelectric micro-electro-mechanical system loudspeaker, and has better high-frequency response than many existing solutions, that is, better full-bandwidth response.

[0088] The present application also includes an electronic device comprising the technical features of any of the above embodiments of the double-sided driven piezoelectric micro-electro-mechanical system loudspeaker, as shown in the accompanying drawings, which can include: a processor 1002, a communications interface 1004, a digital-to-analog converter 1012, a memory 1006, a power amplifier 1014, and a communications bus 1008. Figure 6

[0089] The processor 1002, the communications interface 1004, the digital-to-analog converter 1012, and the memory 1006 communicate with each other through the communications bus 1008.

[0090] The communications interface 1004 is used to communicate with network elements of other devices such as clients or other servers.

[0091] The processor 1002 is used to execute the program 1010, specifically, the program 1010 can include program code including computer operation instructions, which can be responsible for sending digital signals to the DAC.

[0092] The processor 1002 can be a central processing unit CPU, or an application specific integrated circuit ASIC, or one or more integrated circuits configured to implement embodiments of the present application. The one or more processors included in the terminal can be the same type of processor, such as one or more CPUs; or can be different types of processors, such as one or more CPUs and one or more ASICs.

[0093] The memory 1006 is used to store the program 1010. The memory 1006 can include a high-speed RAM memory, and can also include a non-volatile memory such as at least one disk memory.

[0094] The digital-to-analog converter 1012 is used to convert digital quantities into analog waveforms.

[0095] ​Power amplifier 1014, for increasing signal power to drive the load (Speaker).

[0096] The load (Speaker) is the preferred embodiment of any of the embodiments of the piezoelectric micro-electro-mechanical system loudspeaker with double-sided driving structure in the embodiments of the present application.

[0097] The above is a description of the preferred embodiments of the present application, which can help those skilled in the art to more fully understand the technical solutions of the present application. However, these embodiments are only illustrative and cannot be regarded as limiting the specific embodiments of the present application to the description of these embodiments. For those skilled in the art to which the present application belongs, without departing from the concept of the present application, a number of simple deductions and transformations can be made, which should be regarded as falling within the protection scope of the present application.

Claims

1. A piezoelectric MEMS loudspeaker driven on both sides, comprising a substrate with a concave cavity, a support layer, a skeleton layer and an acoustic unit, wherein the acoustic unit is disposed on the skeleton layer, and characterized in that: the acoustic unit comprises a first diaphragm and a second diaphragm; the outer surface of the substrate is provided with the support layer, the support layer is provided with the skeleton layer across the opening direction of the concave cavity of the substrate, the lower surface of the skeleton layer is provided with the first diaphragm, and the upper surface of the skeleton layer is provided with the second diaphragm; the first diaphragm comprises a first sandwich structure with a first piezoelectric layer, and the second diaphragm comprises a second sandwich structure with a second piezoelectric layer; the first sandwich structure comprises a first bottom electrode, a first piezoelectric layer and a first top electrode, and the second sandwich structure comprises a second bottom electrode, a second piezoelectric layer and a second top electrode; the thickness of the skeleton layer is less than or equal to 1 micrometer, and the thickness of the first piezoelectric layer and the second piezoelectric layer is less than or equal to 0.5 micrometer; an FOM value representing the acoustic characteristics of the piezoelectric MEMS loudspeaker is provided, and the FOM value is calculated according to the following formula: the logarithm of the FOM value is taken to represent the sound pressure level at a certain resonance frequency: the logarithm of the FOM value log(FOM) is greater than 112; the logarithm of the FOM value log(FOM) is greater than 118; the thickness of the single piezoelectric layer is less than or equal to 0.25 micrometer; the material of the skeleton layer comprises single crystal silicon, polycrystalline silicon, silicon oxide or silicon nitride; the support layer is a non-conductive material or an amorphous material; the material of the support layer comprises silicon dioxide and silicon nitride; the end surface of the first piezoelectric layer and the first bottom electrode and the first top electrode on one side of the root of the acoustic unit is surrounded and covered by the support layer; a second protective film is provided at the connection between the support layer and the first diaphragm, and a first protective film is provided at the connection surface between the first diaphragm and the concave cavity of the substrate; the first protective film and the second protective film are passivation layers, and the material of the first protective film and the second protective film comprises silicon nitride; the first protective film covers the continuous stepped structure surface of the support layer; the end surface of the first diaphragm on one side of the root thereof, and the lower surface of the first top electrode of the first sandwich structure of the first diaphragm, are a continuous surface layer protective film; the second protective film covers the continuous stepped structure surface of the support layer, and isolates the support layer and the concave cavity; a processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface complete communication with each other through the communication bus, and the processor is connected to the piezoelectric MEMS loudspeaker driven on both sides according to any one of claims 1-16. ​ ​ 2. The biaπally driven piezoelectric microelectromechanical system loudspeaker of claim 1, wherein, ​ 3. The biaπally driven piezoelectric microelectromechanical system loudspeaker of claim 1, wherein, ​ 4. The biaπally driven piezoelectric microelectromechanical system loudspeaker of claim 1, wherein, ​ wherein γ represents the specific heat capacity ratio of air; P0represents atmospheric pressure; S represents the diaphragm area; E P represents the Young's modulus of the piezoelectric layer material; d 31 represents the piezoelectric coefficient of the piezoelectric layer material; U represents the driving voltage; V 711 represents the volume of the simulated ear; p P represents the density of the piezoelectric layer material; p n represents the density of the skeleton layer; t p represents the total thickness of the two piezoelectric layers; t n represents the thickness of the skeleton layer.

5. The biaπally driven piezoelectric microelectromechanical system loudspeaker of claim 4, wherein, The piezoelectric layer material is PZT, the specific heat capacity ratio γ of air, the atmospheric pressure P0, the Young's modulus E of the PZT layer material P The piezoelectric coefficient d of the PZT layer 31 The driving voltage U, the simulated ear volume V 711 The density ρ of the PZT layer material P The density ρ of the skeleton layer n Substitute the FOM value formula to obtain the FOM value formula of the loudspeaker containing the PZT layer: where S represents the diaphragm area; t p represents the total thickness of the two piezoelectric layers; t n represents the thickness of the skeleton layer.

6. The biaπally driven piezoelectric microelectromechanical system loudspeaker of claim 5, wherein, ​ log(FOM) = 20*log 10 (P*f).

7. The biaπally driven piezoelectric microelectromechanical system loudspeaker of claim 6, wherein, ​ 8. The biaπally driven piezoelectric microelectromechanical system loudspeaker of claim 6, wherein, ​ 9. The biaπally driven piezoelectric microelectromechanical system loudspeaker of claim 8, wherein, ​ 10. The bi- driven piezoelectric microelectromechanical system loudspeaker of claim 1, wherein, ​ 11. The bi- driven piezoelectric microelectromechanical system loudspeaker of claim 1, wherein, ​ 12. The bi- driven piezoelectric microelectromechanical system loudspeaker of claim 1, wherein, ​ 13. The bi- driven piezoelectric microelectromechanical system loudspeaker of claim 1, wherein, ​ 14. The biaπally driven piezoelectric microelectromechanical system loudspeaker of claim 13, wherein, ​ 15. The biaπally driven piezoelectric microelectromechanical system loudspeaker of claim 13, wherein, ​ 16. The bi- driven piezoelectric microelectromechanical system loudspeaker of claim 13, wherein, ​ 17. An electronic device comprising: ​

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