CN116887153A

CN116887153A - Piezoelectric MEMS sounder, loudspeaker and sounder manufacturing method

Info

Publication number: CN116887153A
Application number: CN202311014275.6A
Authority: CN
Inventors: 黄湘俊; 朱莉莉; 石正雨
Original assignee: Hubei Jiufengshan Laboratory
Current assignee: Hubei Jiufengshan Laboratory
Priority date: 2023-08-11
Filing date: 2023-08-11
Publication date: 2023-10-13

Abstract

The invention provides a piezoelectric MEMS sounder, a loudspeaker and a sounder manufacturing method.A cavity is arranged in the bottom center area of a substrate, and an insulating layer is arranged on the upper surface of the substrate; at least one piezoelectric composite unit is arranged in the central area of the upper surface of the substrate, and other piezoelectric composite units are arranged in the edge area of the upper surface of the substrate; the preset position of each piezoelectric composite unit is provided with a bonding pad formed by depositing a metal layer, and other areas are deposited with passivation layers; at the upper part of the substrate corresponding to the cavity, at least one groove is formed, the preset area in each groove and at the opening position is covered and filled with flexible materials, and a vibrating film is formed at the upper area of the substrate with at least one groove. The sounder is provided with the groove in the upper area of the substrate, so that stress of the piezoelectric composite unit and the vibrating membrane can be released, flexible materials can be covered and filled in the groove, sound leakage can be prevented, meanwhile, the quality of the vibrating membrane can be reduced, and then the sound pressure level can be improved.

Description

Piezoelectric MEMS sounder, loudspeaker and sounder manufacturing method

Technical Field

The invention relates to the technical field of sounders, in particular to a piezoelectric MEMS sounder, a loudspeaker and a sounder manufacturing method.

Background

Compared with the traditional device, the novel MEMS device manufactured by utilizing the MEMS (Micro-Electro-Mechanical System) technology processing technology has the characteristics of small size, thin thickness and the like in structure, has better performance consistency in performance, lower power consumption, easy integration, intellectualization and the like; sounders have different performance requirements in different applications, not only requiring a good sound pressure level output at low frequencies, but also requiring good acoustic performance at high frequencies. In the related art, the piezoelectric MEMS acoustic generator manufactured by using the MEMS technology has limited capacity of reducing the mass of the vibrating membrane, and thus has limited capacity of improving the sound pressure level.

Disclosure of Invention

The invention aims to provide a piezoelectric MEMS sounder, a loudspeaker and a sounder manufacturing method, which are used for reducing the quality of a vibrating membrane and further improving the sound pressure level.

The invention provides a piezoelectric MEMS sounder, comprising: a substrate and a plurality of piezo-electric composite units; the bottom center area of the substrate is provided with a cavity, and the upper surface of the substrate is provided with an insulating layer; the at least one piezoelectric composite unit is arranged in the central area of the upper surface of the substrate, and other piezoelectric composite units except the at least one piezoelectric composite unit are arranged in the edge area of the upper surface of the substrate; the preset position of each piezoelectric composite unit is provided with a bonding pad formed by depositing a metal layer, and other areas of each piezoelectric composite unit except the preset position are deposited with passivation layers; at least one groove is formed in the upper portion of the substrate corresponding to the cavity except the area where each piezoelectric composite unit is located, the preset area in each groove and at the opening position is covered and filled with flexible materials, and a vibrating film is formed in the upper portion of the substrate with the at least one groove.

Further, each piezoelectric composite unit sequentially comprises a bottom electrode layer, an intermediate layer and a top electrode layer from bottom to top; the middle layer is a piezoelectric layer, or the middle layer is formed by overlapping and stacking a plurality of piezoelectric layers and a plurality of electrode layers; wherein, the upper layer of the bottom electrode layer and the lower layer of the top electrode layer are both piezoelectric layers.

Further, each groove is completely filled with a flexible material.

The invention provides a loudspeaker, which comprises a plurality of piezoelectric MEMS sounders.

Further, the piezoelectric MEMS sounders are arranged in a preset arrangement mode; the preset arrangement mode comprises at least one of the following steps: a honeycomb arrangement mode, a horizontal axis linear arrangement mode and a vertical axis linear arrangement mode.

The invention provides a method for manufacturing a piezoelectric MEMS sounder, which comprises the following steps: respectively thermally oxidizing the upper surface and the lower surface of a preset substrate to grow an insulating layer; wherein, the substrate comprises an insulating buried layer; sequentially depositing a seed layer, a bottom electrode layer, an intermediate layer and a top electrode layer on an insulating layer on the upper surface of a substrate from bottom to top to obtain a first device; the middle layer is a piezoelectric layer, or the middle layer is formed by overlapping and stacking a plurality of piezoelectric layers and a plurality of electrode layers; the upper layer of the bottom electrode layer and the lower layer of the top electrode layer are both piezoelectric layers; processing the bottom electrode layer, the middle layer and the top electrode layer in the first device to form a plurality of piezoelectric composite units, so as to obtain a processed second device; wherein, at least one piezoelectric composite unit is arranged in the central area of the upper surface of the substrate, and other piezoelectric composite units except for the at least one piezoelectric composite unit are arranged in the edge area of the upper surface of the substrate; processing the second device to obtain a piezoelectric MEMS sounder; the bottom center area of the substrate of the piezoelectric MEMS sounder is provided with a cavity, the upper part of the substrate corresponding to the cavity is provided with at least one groove except the area where each piezoelectric composite unit is located, the preset area in each groove and at the opening position is covered and filled with flexible materials, and the upper area of the substrate with the at least one groove forms a vibrating film.

Further, the steps of processing the bottom electrode layer, the middle layer and the top electrode layer in the first device to form a plurality of piezoelectric composite units, and obtaining the processed second device include: patterning the top electrode layer of the first device to obtain a third device after patterning; carrying out dry etching treatment on the intermediate layer and the bottom electrode layer of the third device according to a preset etching angle to obtain a treated fourth device; and carrying out wet etching treatment on the intermediate layer of the fourth device to obtain a treated second device.

Further, the range of the preset etching angle is as follows: 30-60 deg..

Further, the step of processing the second device to obtain the piezoelectric MEMS acoustic generator includes: depositing a passivation layer on the second device to isolate the electrical connection of each top electrode layer, and performing graphical treatment on the passivation layer to form a bonding pad area so as to lead out the bottom electrode layer and/or the top electrode layer of each piezoelectric composite unit, thereby obtaining a fifth device; depositing a metal layer on each bonding pad area in the fifth device to form bonding pads, so as to obtain a sixth device; and processing the sixth device to obtain the piezoelectric MEMS sounder.

Further, the step of processing the sixth device to obtain the piezoelectric MEMS acoustic generator includes: etching the upper surface of the sixth device except the areas of the piezoelectric composite units in the positions close to the central area of the upper surface to form at least one groove, and covering and filling flexible materials in each groove and in a preset area of the opening position to obtain a seventh device; thinning and etching the bottom surface of the substrate of the seventh device to obtain a piezoelectric MEMS sounder; wherein the etched cavity is positioned in the bottom central area of the substrate

The invention provides a piezoelectric MEMS sounder, a loudspeaker and a sounder manufacturing method, wherein the sounder comprises: a substrate and a plurality of piezo-electric composite units; the bottom center area of the substrate is provided with a cavity, and the upper surface of the substrate is provided with an insulating layer; the at least one piezoelectric composite unit is arranged in the central area of the upper surface of the substrate, and other piezoelectric composite units except the at least one piezoelectric composite unit are arranged in the edge area of the upper surface of the substrate; the preset position of each piezoelectric composite unit is provided with a bonding pad formed by depositing a metal layer, and other areas of each piezoelectric composite unit except the preset position are deposited with passivation layers; at least one groove is formed in the upper portion of the substrate corresponding to the cavity except the area where each piezoelectric composite unit is located, the preset area in each groove and at the opening position is covered and filled with flexible materials, and a vibrating film is formed in the upper portion of the substrate with the at least one groove. The sounder is provided with the groove in the upper area of the substrate, so that stress of the piezoelectric composite unit and the vibrating membrane can be released, flexible materials can be covered and filled in the groove, sound leakage can be prevented, meanwhile, the quality of the vibrating membrane can be reduced, and then the sound pressure level can be improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic structural diagram of a piezoelectric MEMS acoustic generator according to an embodiment of the present invention;

FIG. 2 is a schematic structural diagram of a piezoelectric MEMS acoustic generator according to an embodiment of the present invention;

fig. 3 (a) is a schematic structural diagram of a piezoelectric composite unit according to an embodiment of the present invention;

fig. 3 (b) is a schematic structural diagram of a piezoelectric composite unit according to an embodiment of the present invention;

fig. 3 (c) is a schematic structural diagram of a piezoelectric composite unit according to an embodiment of the present invention;

FIG. 4 (a) is a schematic structural diagram of a piezoelectric MEMS acoustic generator according to an embodiment of the present invention;

FIG. 4 (b) is a schematic structural diagram of a piezoelectric MEMS acoustic generator according to an embodiment of the present invention;

FIG. 4 (c) is a schematic structural diagram of a piezoelectric MEMS acoustic generator according to an embodiment of the present invention;

FIG. 4 (d) is a schematic structural diagram of a piezoelectric MEMS acoustic generator according to an embodiment of the present invention;

FIG. 4 (e) is a schematic structural diagram of a piezoelectric MEMS acoustic generator according to an embodiment of the present invention;

FIG. 4 (f) is a schematic structural diagram of a piezoelectric MEMS acoustic generator according to an embodiment of the present invention;

FIG. 4 (g) is a schematic structural diagram of a piezoelectric MEMS acoustic generator according to an embodiment of the present invention;

FIG. 4 (h) is a schematic structural diagram of a piezoelectric MEMS acoustic generator according to an embodiment of the present invention;

FIG. 4 (i) is a schematic structural diagram of a piezoelectric MEMS acoustic generator according to an embodiment of the present invention;

FIG. 4 (j) is a schematic structural diagram of a piezoelectric MEMS acoustic generator according to an embodiment of the present invention;

FIG. 4 (k) is a schematic structural diagram of a piezoelectric MEMS acoustic generator according to an embodiment of the present invention;

FIG. 4 (l) is a schematic structural diagram of a piezoelectric MEMS acoustic generator according to an embodiment of the present invention;

FIG. 5 (a) is a schematic diagram of an array structure of a piezoelectric MEMS acoustic generator according to an embodiment of the present invention;

FIG. 5 (b) is a schematic diagram of an array structure of a piezoelectric MEMS acoustic generator according to an embodiment of the present invention;

FIG. 5 (c) is a schematic diagram of an array structure of a piezoelectric MEMS acoustic generator according to an embodiment of the present invention;

FIG. 5 (d) is a schematic diagram of an array structure of a piezoelectric MEMS acoustic generator according to an embodiment of the present invention;

FIG. 5 (e) is a schematic diagram of an array structure of a piezoelectric MEMS acoustic generator according to an embodiment of the present invention;

FIG. 5 (f) is a schematic diagram of an array structure of a piezoelectric MEMS acoustic generator according to an embodiment of the present invention;

FIG. 6 is a schematic diagram of polarization and electrical connection of a piezoelectric MEMS acoustic generator according to an embodiment of the present invention;

FIG. 7 is a schematic diagram of polarization and electrical connection of a piezoelectric MEMS acoustic generator according to an embodiment of the present invention;

FIG. 8 is a schematic diagram of simulation results of a piezoelectric MEMS acoustic generator without flexible material filling according to an embodiment of the present invention;

FIG. 9 is a schematic diagram of simulation results of a piezoelectric MEMS acoustic generator filled with a flexible material according to an embodiment of the present invention;

FIG. 10 is a schematic cross-sectional view of a substrate with an insulating layer grown thereon according to an embodiment of the present invention;

FIG. 11 is a schematic cross-sectional view of a bottom electrode layer after growth according to an embodiment of the present invention;

FIG. 12 is a schematic cross-sectional view of an embodiment of the present invention after growing an intermediate layer and a top electrode layer;

FIG. 13 is a schematic cross-sectional view of a patterned top electrode according to an embodiment of the present invention;

FIG. 14 is a schematic cross-sectional view of a dry etching process after etching an intermediate layer and a bottom electrode layer according to an embodiment of the present invention;

FIG. 15 is a schematic cross-sectional view of a wet etching interlayer according to an embodiment of the present invention;

FIG. 16 is a schematic cross-sectional view of a passivation layer after deposition and patterning according to an embodiment of the present invention;

FIG. 17 is a schematic cross-sectional view of a metal wire after deposition and patterning according to an embodiment of the present invention;

FIG. 18 is a schematic cross-sectional view of an SOI top layer silicon trench etched according to an embodiment of the present invention;

FIG. 19 is a schematic cross-sectional view of a flexible material coated according to an embodiment of the present invention;

fig. 20 is a schematic cross-sectional view of a thinned wafer according to an embodiment of the present invention.

Icon: 01-SOI substrate silicon; 02-BOX layer; 03-SOI top layer silicon; 04-insulating layer; 05-a seed layer; 06-a bottom electrode layer; 07-a piezoelectric layer; 08-top electrode layer; 09-groove; 10-a flexible material; 11-a passivation layer; 12-bonding pads; 13-a welding disc; 14-cavity; 15-vibrating a film; 60-fixing constraint; 10 a-a first piezoelectric composite unit; 10 b-a second piezoelectric composite unit; 10 c-a piezoelectric composite unit III; a 10 d-piezoelectric composite unit IV; 10 e-a piezoelectric composite unit; 10 f-a piezoelectric composite unit six; 10 g-a piezoelectric composite unit seven; 30 a-etching the first region; 30 b-etching the second region; 30 c-etching the third region; 30 d-etching the fourth region; 30 e-etching the region five; 30 f-etching a region six; 40 a-flexible material region one; 40 b-flexible material region one; 40 c-flexible material region one; 40d—flexible material region one; 40 e-flexible material region one; 40 f-flexible material region one; 40 g-flexible material region seven; 50-dividing areas of the inner layer of the diaphragm.

Detailed Description

The technical solutions of the present invention will be clearly and completely described in connection with the embodiments, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

At present, compared with the traditional device, the novel MEMS device manufactured by utilizing the Micro-Electro-Mechanical System MEMS technology processing technology has the characteristics of small size, thin thickness and the like in structure, the product can be produced in batches, the full-automatic assembly has the advantage of cost, and the device has the characteristics of MEMS technology, good performance consistency, low power consumption, easy integration, intellectualization and the like in performance. Microphones in mobile communication devices such as cell phones and tablets have been miniaturized by MEMS technology.

The sounder has different performance requirements in different applications, not only needs to have good sound pressure level output at low frequency, but also needs to have good acoustic performance at high frequency stage, and the primary task of the high-pitch sounder is to realize high sound pressure level at high frequency. To achieve this, the moving mass needs to be small because the lower the mass, the higher the vibrating membrane acceleration and therefore the higher the SPL (Sound Pressure Level, sound pressure) at high frequencies when the forces of the motors are equal. Moving coil acoustic generators have a lower limit on moving mass due to the heavy copper coil, balanced armature designs can reduce mass, but their stiff vibrating membranes typically have strong resonances, and their front cavity dimensions limit high frequency performance by creating resonances. MEMS technology therefore has inherent advantages in this respect, as the mass of silicon is very light, and MEMS technology shows the greatest potential in designing an ideal tweeter. MEMS sounders are lighter and produce significantly less mechanical vibration. This is important not only for hearing aids but also for modern TWS headphones.

The related art provides a MEMS piezoelectric sound generator with a soft supporting structure, wherein a composite vibrating membrane layer in a central area is formed by a piezoelectric layer and a composite dielectric layer, the periphery of the composite vibrating membrane layer in the central area is provided with an annular groove and the soft supporting membrane layer positioned on the annular groove, so that the soft supporting structure at the edge is formed, the stress of the composite vibrating membrane layer is released, the vibration amplitude and the radiation sound pressure are improved, and the sensitivity of the MEMS piezoelectric sound generator is improved; the organic film is adopted as a soft support film layer, so that the structure has good elasticity and sealing performance, a hard material is formed in a central area, and a flexible material is formed in an edge support area, so that the vibration amplitude is improved, and meanwhile, the problems of sound leakage and radiation area reduction are prevented. However, in this technology, the soft supporting structure at the edge may reduce the rigidity of the whole device, so that the first-order resonant frequency of the speaker moves to a low frequency, and correspondingly, the higher-order high-frequency resonant frequency also moves to a low frequency, so that the higher-order high-resonant frequency occurs in the range of the auditory sense of the human ear (20 Hz-20 kHz), not only reduces the sound pressure level, but also increases the harmonic distortion, and affects the auditory sense. In addition, the method adopts a sacrificial material filling and releasing process, the process is complex, and the uniformity of filling and releasing leads to poor consistency of device performance.

In another implementation of the related art, a microelectromechanical sound transducer with a polymer coating is provided, which has another advantage in that a cured polymer is formed after the polymer has cured. Both the coating formed by the cured polymer and the piezoelectric assembly form a composite structure. The piezoelectric assembly may be formed of ceramic, for example. Further, if the piezoelectric assembly is relatively thin, the vibration performance for the piezoelectric assembly is better. However, this increases the risk of cracking the piezoelectric assembly. The piezoelectric component can be stabilized by a coating formed of a cured polymer, which has elasticity and flexibility even after curing. The coating made of cured polymer and the piezoelectric assembly form a composite system such that the piezoelectric assembly is stabilized by the coating. However, the film formed by the polymer cured in this way only acts as a protective structure and does not reduce the quality of the vibrating membrane. In addition, the composite structure is formed by the coating film formed by the solidified polymer and the piezoelectric component, and the process and the stress limitation of each layer structure can cause larger harmonic distortion (Total Harmonic Distortion, THD) and the lifting capability of the Sound Pressure Level (SPL) is limited.

In summary, in the related art, the piezoelectric MEMS acoustic generator manufactured by using the MEMS technology has limited capability of reducing the mass of the vibrating membrane, and thus has limited capability of improving the sound pressure level. Based on the above, the embodiment of the invention provides a piezoelectric MEMS sounder, a loudspeaker and a sounder manufacturing method, and the technology can be applied to the application needing to improve the sound pressure level of the piezoelectric MEMS sounder.

For the convenience of understanding the present embodiment, a piezoelectric MEMS acoustic generator disclosed in the embodiment of the present invention will be described first, and the piezoelectric MEMS acoustic generator includes: a substrate and a plurality of piezo-electric composite units; the bottom center area of the substrate is provided with a cavity, and the upper surface of the substrate is provided with an insulating layer; the at least one piezoelectric composite unit is arranged in the central area of the upper surface of the substrate, and other piezoelectric composite units except the at least one piezoelectric composite unit are arranged in the edge area of the upper surface of the substrate; the preset position of each piezoelectric composite unit is provided with a bonding pad formed by depositing a metal layer, and other areas of each piezoelectric composite unit except the preset position are deposited with passivation layers; at least one groove is formed in the upper portion of the substrate corresponding to the cavity except the area where each piezoelectric composite unit is located, the preset area in each groove and at the opening position is covered and filled with flexible materials, and a vibrating film is formed in the upper portion of the substrate with the at least one groove.

The substrate can be made of SOI (Silicon-On-Insulator), monocrystalline Silicon, polycrystalline Silicon, glass, sapphire and other materials, and can be specifically selected according to actual requirements; the number of the piezoelectric composite units is usually multiple, wherein one or more piezoelectric composite units are usually arranged above the insulating layer in the central area of the upper surface of the substrate, and other piezoelectric composite units are usually arranged above the insulating layer in the area close to the edge of the upper surface of the substrate; the piezoelectric composite layer unit can deform the vibrating film under the drive of the electric signal, so that sound waves can be generated, the vibration sound of the piezoelectric MEMS sounder is realized, and the vibrating film is formed by laminating a rigid material and a flexible material capable of being bonded and patterned by MEMS technology; the size, the appearance and the like of the cavity can be set according to actual requirements, the back of the substrate can be etched to form a back cavity, namely the cavity, and the resonant frequency and the sound pressure level output of the piezoelectric MEMS sounder device can be changed by designing cavity structures with different sizes; the preset position may include an upper surface and/or a side surface of the piezoelectric composite unit, wherein if the preset position is the upper surface of the piezoelectric composite unit, a pad on the upper surface may form an electrical connection with an upper electrode layer of the piezoelectric composite unit; if the preset position is a side position of the piezoelectric composite unit, a bonding pad at the side position can be electrically connected with the lowest electrode layer of the piezoelectric composite unit; the passivation layer is deposited to insulate the piezoelectric composite units and isolate the electrical connection of the electrode layers of each layer, thus playing a role in protecting the electrodes, the passivation layer needs to have good step coverage and can be tightly attached to each film layer to play roles in electrical isolation and protection, and the material of the passivation layer can comprise one or a combination of the following materials: TEOS (Tetra-Ethyl OrthoSilicate, tetraethyl orthosilicate), silicon dioxide, aluminum nitride, PI (Polyimide), aluminum oxide, and other oxide insulating materials, or non-conductive organic compounds, etc.

And etching the passivation layer to form a through hole on the bottom electrode and the top electrode, forming PAD and a metal connecting wire through metal layer deposition, and when the polarization directions of the piezoelectric layers in the central area of the vibrating film and the peripheral piezoelectric composite units are the same, depositing to form PAD and the metal connecting wire, wherein the metal connecting wire can be connected with the piezoelectric composite units on the periphery of the vibrating film in parallel, the bottom electrode is connected with the bottom electrode, the top electrode is connected with the top electrode, and the piezoelectric composite units are electrically connected in parallel. The metal wire can be connected in series with the central area and the peripheral piezoelectric composite units of the vibrating film, and the bottom electrode of the central piezoelectric composite unit is connected with the top electrode of the peripheral piezoelectric composite unit in series.

A schematic structural diagram of a piezoelectric MEMS acoustic generator as shown in fig. 1, where the substrate is made of SOI material, includes: SOI base silicon 01, BOX layer 02, SOI top layer silicon 03; an insulating layer 04 formed on the SOI top layer silicon 03; a seed layer 05 formed on the insulating layer 04; a bottom electrode layer 06, a piezoelectric layer 07 and a top electrode layer 08 of the piezoelectric composite unit; the groove 09 etched on the SOI top layer silicon 03 is a square groove, the groove 09 is positioned above the hollow area and at two sides of the piezoelectric composite unit in the central area, the groove 09 is completely covered and filled by adopting the flexible material 10, and the covering width is larger than the etched groove width; a passivation layer 11 is included, primarily for electrical insulation and isolation; the bonding pad 12 is positioned at a preset position of the piezoelectric composite unit; a metal wire 13 located at the edge of the piezoelectric composite unit and deposited on the passivation layer 11; the central region of the device is also a hollow region, namely a cavity 14, wherein the SOI top layer silicon 03 positioned after etching the groove 09 and the flexible material 10 form a rigid-flexible combined vibrating film 15. In order to facilitate the electrical connection between the top electrode layer 08 and the bottom electrode layer 06 in the device, an opening is etched away from the portion above the bottom electrode layer 06, so that the bottom electrode is exposed to form a PAD on the deposited metal layer, which serves as a bottom electrode bonding hole.

Referring to a schematic structural diagram of a piezoelectric MEMS acoustic generator shown in fig. 2, where fig. 1 corresponds to a cross-sectional view corresponding to fig. 2, a black thick solid line in fig. 2 is a cutting line of the piezoelectric MEMS acoustic generator, and after the cutting, a cross-sectional view of the piezoelectric MEMS acoustic generator in fig. 1 is obtained. In fig. 2, the SOI top layer silicon 03 has a fixed constraint 60 around, and the fixed constraint 60 may correspond to the SOI substrate silicon 01 in fig. 1, and fig. 2 further includes: the piezoelectric composite unit of the silicon vibration film outer area of the piezoelectric MEMS sounder can be an independent execution unit, the piezoelectric composite unit is divided into six areas, namely a piezoelectric composite unit I10 a, a piezoelectric composite unit II 10b, a piezoelectric composite unit III 10c, a piezoelectric composite unit IV 10d, a piezoelectric composite unit V10 e and a piezoelectric composite unit VI 10f, in addition, the piezoelectric composite unit seven 10g in the silicon vibration film middle area is further included, a white dotted line in fig. 2 represents an etched area of SOI silicon, the outer piezoelectric composite layer unit is divided into six areas by an etched area I30 a, an etched area II 30b, an etched area III 30c, an etched area IV 30d, an etched area V30 e and an etched area VI 30f, the shape is an equal trapezoid structure, and the etched area V30 g is a hexagonal linear structure and is connected with the etched area I30 a, the etched area II 30b, the etched area III 30c, the etched area IV 30d, the etched area V30 e and the etched area VI f. The device can be decoupled in structure through the etching area, and meanwhile, the process internal stress of each film layer is released, so that larger driving displacement and sound pressure level output can be obtained. The figure 2 further includes a first flexible material region 40a, a second flexible material region 40b, a third flexible material region 40c, a fourth flexible material region 40d, a fifth flexible material region 40e, a sixth flexible material region 40f, and a seventh flexible material region 40g, and covers each etching region, the width of each etching region is greater than the etching width, black dot and dash lines 20a, 20b, 20c, 20d, 20e, and 20f in the figure are connected to form a hexagon, back cavity deep silicon etching etches back SOI bottom silicon and Box layers to form a hollow cavity hexagon structure, and the hollow cavity hexagon structure is released into a vibrating film structure of the MEMS piezoelectric sounder, and the figure 2 further includes a diaphragm inner layer dividing region 50.

The piezoelectric composite unit seven 10g located in the middle area in fig. 2 has a hexagonal structure, but the shape of the piezoelectric composite unit seven 10g may have other irregular graphic structures such as a rectangle, a circle, a polygon, etc., and meanwhile, the piezoelectric composite unit one 10a, the piezoelectric composite unit two 10b, the piezoelectric composite unit three 10c, the piezoelectric composite unit four 10d, the piezoelectric composite unit five 10e, the piezoelectric composite unit six 10f, and the piezoelectric composite unit seven 10g may be subdivided into two or more parts, and the shape of the piezoelectric composite unit seven may have a plurality of different graphic structures; the black dashed line in fig. 2 indicates the etched area of the SOI, and the etched area may have a rectangular, circular, polygonal, or other irregular pattern structure, and the position of the etched area in the diaphragm and the size of the etched area may vary widely, not only as shown in the figure.

One or more grooves are etched in the upper area of the substrate corresponding to the cavity, and it can be understood that the top layer of the substrate is etched to obtain one or more grooves, the grooves can be annular, long grooves and etched area layers with other shapes, including square, rectangle or polygon, flexible materials are covered and filled in the grooves, and meanwhile, flexible materials are filled in preset areas at the periphery of the opening positions of the grooves, namely, the width covered by the flexible materials is larger than the width of the grooves; the flexible material can be selected from PI, PVI-3 (PVI English is Poly Vinyl Isobutyl ether, vinyl isobutyl ether), flexfin SA, polyurethane, parylene C, polyimide, parylene, polyurethane, flexfiner or other organic films, and the like, and the flexible material can be selected according to actual requirements, wherein the flexible material generally needs to meet the following conditions: 1) The MEMS device is compatible with MEMS technology, and can carry out the technologies of pasting, exposing, etching and the like; 2) The reliability problem, dust prevention, water prevention and insulation, and simultaneously, the plate blocks of rigid materials are attached, and the phenomena of film tearing, layering, stripping and the like can not occur under the conditions of different humidity and stress or excitation; 3) The flexible material can resist high temperature and bear the temperature of the patch packaging process without causing reliability problems of the device, such as cracking of the rigid material; 4) At a certain stretching rate, the flexible material is not damaged when the device deflects.

The upper region of the substrate having at least one recess forms a vibration film, and generally the upper surface of the substrate is parallel to the vibration film, and it is understood that the vibration film has a recess so that stress of the piezoelectric composite unit and the vibration film is released, and at the same time, the recess is filled with a flexible dry film material, which serves to connect the rigid grooved portions and fill the grooved gaps, and sound leakage occurs when the vibration film vibrates. The groove part is covered or filled with a flowable and curable polymer flexible material, and the coating is formed after curing, so that gas cannot flow out of a slot when the piezoelectric MEMS sounder vibrates and sounds, and the low-frequency output sound pressure level of the piezoelectric MEMS sounder is improved; the groove part is covered or filled by flexible materials, the vibration film is combined with rigidity and flexibility, the moving mass of the vibration film is reduced, when the force of the motor is equal, the lower the mass is, the higher the acceleration of the vibration film is, and the high sound pressure level SPL is realized under high frequency. The piezoelectric MEMS sounder prepared from the flexible material can bear stronger drop and impact resistance, and has strong device reliability. In addition, the flexible material has a certain stretching rate, and the vibration deflection of the device is larger under the excitation action, so that more air quantity can be pushed to improve the sound pressure level output. In the present embodiment, "rigid" and "flexible" refer to the characteristics of the material, and "rigid" refers to hardness and strength; "Flexible" means that the material is flexible.

The thickness of the flexible material is 1-50 μm. Specifically, proper thickness can be selected according to actual demands, and the sound pressure level can be effectively improved while the quality of the vibrating film is reduced through selecting proper thickness.

The thickness of the vibration film is 0.1-100 μm. In particular, the thickness of the vibrating membrane can be selected to be suitable according to practical requirements, and the vibrating membrane is anchored on the substrate as can be seen from the above description. The stress of the piezoelectric composite unit and the vibrating membrane can be released by selecting proper thickness, so that the sound pressure level is improved.

Further, the thickness of each piezoelectric layer is in the range of 0.1 μm to 50. Mu.m, and the thickness of each electrode layer is in the range of 0.05 μm to 5. Mu.m. If the piezoelectric composite unit comprises a plurality of piezoelectric layers, the materials of each piezoelectric layer can be the same material or different materials, the thicknesses of different piezoelectric layers can be the same or different, the thickness interval of the piezoelectric layers is usually between 0.1 mu m and 50 mu m, and the proper materials or thicknesses can be selected according to actual requirements. Similarly, if the piezoelectric composite unit includes multiple electrode layers, the materials of each electrode layer may be the same material or different materials, the thicknesses of different electrode layers may be the same or different, the thickness interval of the electrode layers is usually between 0.05 μm and 5 μm, and a suitable material or thickness may be selected according to actual requirements.

Further, the material of the piezoelectric layer and the material of the electrode layer may be monocrystalline or polycrystalline.

The material of each electrode layer in the bottom electrode layer, the top electrode layer and the intermediate layer may be a single crystal material, a polycrystalline material, a metal or nonmetal conductive film, or may be a single crystal metal material or an alloy material, for example, the material of each electrode layer may be one of the following materials or a combination thereof, but not limited to: single-crystal or polycrystalline metal thin films of aluminum, copper, gold, platinum, molybdenum, chromium, titanium, etc., metal conductive films of Lanthanum Nickelate (LNO), SRO (strontium oxide), etc., or composite metal layers such as: gold/chromium composite layer. Among them, the platinum PT electrode preferably has a thickness of 0.1 μm to 5 μm, for example, the platinum PT electrode has a thickness of 0.15 μm or the like.

The material of the piezoelectric layer may be, but is not limited to, one or a combination of the following materials: polycrystalline or monocrystalline piezoelectric films such as ZnO, monocrystalline AlN, monocrystalline PZT (lead zirconate titanate film), PVDF (polyvinylidene fluoride), or doped piezoelectric films such as doped AlN, doped PZT, or the like; the thickness of the piezoelectric layer is between 0.2 μm and 15 μm. For example, a single crystal PZT thin film having a thickness of 2um.

Further, the width of the groove ranges from 1 μm to 200 μm. The internal stress of the piezoelectric composite unit and the vibrating membrane can be released through the grooves, and the internal stress is decoupled structurally, and in actual implementation, the thickness interval of the vibrating membrane is usually between 0.1 and 100 mu m, and the width of the grooves is usually between 1 and 200 mu m.

In this embodiment, the piezoelectric MEMS acoustic generator is generally designed to have a symmetrical structure, so that the neutral layer of the entire vibrating membrane of the piezoelectric MEMS acoustic generator is located at the center of the vibrating membrane, and applies appropriate driving to the piezoelectric composite unit, so that the output sound pressure level of the piezoelectric MEMS acoustic generator can be improved; the neutral layer is referred to as a stress neutral layer, for example, in which the outer layer of the vibration film is subjected to tensile stress and the inner side is subjected to compressive stress, and there is always zero stress at a point between the tensile stress and the compressive stress, and the layer equal to zero stress is the stress neutral layer.

Above-mentioned piezoelectricity MEMS sounder sets up the recess in the upper portion region of basement, helps releasing the stress of piezoelectricity recombination unit and vibrating membrane, covers in the recess and fills flexible material, can prevent that sound from revealing, can reduce vibrating membrane's quality simultaneously, and then promotes the sound pressure level.

In actual implementation, each piezoelectric composite unit may be a single piezoelectric layer structure, i.e., an electrode layer/a piezoelectric layer/an electrode layer; can be a double piezoelectric layer structure: electrode layer/piezoelectric layer/electrode layer, and multi-piezoelectric layer structure: electrode layer/piezoelectric layer/electrode layer … …/piezoelectric layer/electrode layer; specifically, a proper structure can be selected according to actual requirements. The application of an electric field to the piezoelectric layers of each piezoelectric composite unit is closely related to the polarization direction of the piezoelectric layers, and the reasonable treatment of the relationship between the two makes the output deflection of the piezoelectric MEMS sounder maximum.

The structure of a piezoelectric composite unit shown in fig. 3 (a), the structure of a piezoelectric composite unit shown in fig. 3 (b) and the structure of a piezoelectric composite unit shown in fig. 3 (c) are shown, wherein the piezoelectric composite unit in fig. 3 (a) is a single piezoelectric layer, and the piezoelectric composite unit is a bottom electrode layer, a piezoelectric layer and a top electrode layer from bottom to top respectively; the piezoelectric composite unit in fig. 3 (b) is a double piezoelectric layer, and the piezoelectric composite units are respectively from bottom to top: a bottom electrode layer, a piezoelectric layer, an electrode layer, a piezoelectric layer, a top electrode layer; the piezoelectric composite unit in fig. 3 (c) is a multi-piezoelectric layer structure, and the multi-piezoelectric layer structure can be analogized in sequence, and the description thereof is omitted.

In practical implementation, the distribution of the piezoelectric composite units on the vibration film may adopt other modes besides the distribution mode in fig. 2, such as a structural schematic diagram of a piezoelectric MEMS acoustic generator shown in fig. 4 (a), a structural schematic diagram of a piezoelectric MEMS acoustic generator shown in fig. 4 (b), a structural schematic diagram of a piezoelectric MEMS acoustic generator shown in fig. 4 (c), a structural schematic diagram of a piezoelectric MEMS acoustic generator shown in fig. 4 (d), a structural schematic diagram of a piezoelectric MEMS acoustic generator shown in fig. 4 (e), a structural schematic diagram of a piezoelectric MEMS acoustic generator shown in fig. 4 (f), a structural schematic diagram of a piezoelectric MEMS acoustic generator shown in fig. 4 (g), a structural schematic diagram of a piezoelectric MEMS acoustic generator shown in fig. 4 (h), a structural schematic diagram of a piezoelectric MEMS acoustic generator shown in fig. 4 (j), a structural schematic diagram of a piezoelectric MEMS acoustic generator shown in fig. 4 (k), a structural schematic diagram of a piezoelectric MEMS acoustic generator shown in fig. 4 (l), and the structural schematic diagram of a piezoelectric MEMS acoustic generator shown in fig. 4 (j) may be selected according to practical demands. For example, compared with the piezoelectric MEMS piezoelectric acoustic generator in fig. 2, the piezoelectric MEMS piezoelectric acoustic generator in fig. 4 (a) has a circular structure of the piezoelectric composite unit inside the diaphragm of the piezoelectric MEMS piezoelectric acoustic generator in fig. 4 (a), and has two white dashed etched areas with hexagonal structures in the middle, which are regularly distributed inside the diaphragm, and has a symmetrical structure on the horizontal and vertical axes.

Further, each groove is completely filled with a flexible material. In this embodiment, each groove is typically filled with a flexible material.

The resonant frequency of the piezoelectric MEMS acoustic generator is related to the stiffness and mass of the diaphragm, and the flexible material filling will increase the elastic coefficient, reduce the mass of the diaphragm, reduce the stiffness of the diaphragm, and should improve the low frequency characteristics of the speaker at the same mass. Too low a frequency drop of the vibrating membrane affects the high frequency effect, since at high frequencies split modes of vibration occur, avoiding too low a resonant frequency as a relative area of the flexible material is properly controlled. The rigidity is unchanged, the medium-high frequency performance of the device is improved, and the device performance can be optimized through the optimal design.

The MEMS piezoelectric sounder works at a mechanical resonance point and can be designed to be within the range of 20Hz-20KHz of audio frequency or be out of the range of 20KHz of the audio frequency through the thickness of the film layer and the size of the cavity, and even in an ultrasonic frequency band.

An embodiment of the present invention provides a loudspeaker comprising a plurality of piezoelectric MEMS acoustic generators as defined in any one of the preceding claims. The number of the piezoelectric MEMS sounders can be set according to actual requirements; the piezoelectric MEMS sounders are arranged in a preset arrangement mode; the preset arrangement mode comprises at least one of the following steps: a honeycomb arrangement mode, a horizontal axis linear arrangement mode and a vertical axis linear arrangement mode.

If the size of a single piezoelectric MEMS acoustic generator is smaller, the acoustic output is smaller, and a plurality of piezoelectric MEMS acoustic generators can be arranged and combined, for example, the plurality of piezoelectric MEMS acoustic generators can be arranged in an array form and driven by electric parallel connection, so that the output sound pressure level can be further improved, wherein the vibrating films of the plurality of piezoelectric MEMS acoustic generators need to be coplanar. The polarization directions of the piezoelectric layers in all piezoelectric composite units at the upper periphery of the vibrating film structure are the same (upward or downward), and the polarization directions of the piezoelectric composite units in the central area are opposite to those of the piezoelectric composite units in the peripheral area, so that the bottom electrode layers of the piezoelectric composite units in the peripheral area are connected with the bottom electrodes of the piezoelectric composite units in the central area, and the top electrode layers of the piezoelectric composite units in the peripheral area are connected with the top electrodes of the piezoelectric composite units in the central area in series. When a plurality of piezoelectric composite units exist at the periphery or the middle area of the upper side of the vibrating membrane structure and the polarization directions of piezoelectric layers of the composite units are inconsistent, the polarization is connected in parallel in the same direction, and the polarization is connected in series in opposite directions.

Generally, the larger the effective radiation area, the higher the generated sound pressure. The greater the displacement of the radiating area of the vibrating membrane, the higher the sound pressure generated. In order to generate sound, when the single piezoelectric MEMS sounder outputs a limited sound pressure level SPL under excitation, a plurality of piezoelectric MEMS sounders can be distributed in an array structure, so that the sounding area of the sounder is increased, and the sound pressure level output of the device is improved. An array structure of a piezoelectric MEMS acoustic generator as shown in fig. 5 (a), an array structure of a piezoelectric MEMS acoustic generator as shown in fig. 5 (b), and an array structure of a piezoelectric MEMS acoustic generator as shown in fig. 5 (c).

The array structure of the piezoelectric MEMS acoustic generators in fig. 5 (a) adopts the piezoelectric MEMS acoustic generators with the same structure, and the size parameters, the structural shape and the performance of unit devices (i.e. each piezoelectric MEMS acoustic generator) in the array are consistent. The array structure is arranged in a honeycomb structure, and the unit devices in the array are closely arranged, so that the array arrangement can be performed for two unit devices in fig. 4 (a), three unit devices and the like, and various other unit arrangements and the like; the array structure of the piezoelectric MEMS acoustic generator in fig. 5 (a) may adopt the piezoelectric MEMS acoustic generator in fig. 2, or may adopt any one of the piezoelectric MEMS acoustic generators in fig. 4, etc., to form an array structure of a plurality of identical and/or different devices.

The array structure of the piezoelectric MEMS acoustic generator in fig. 5 (b) is arranged in such a manner that the array structure is arranged as a single or a plurality of identical unit devices in fig. 4 (b) and 4 (c), and the arranged devices may be identical or different, as compared with the array structure of the piezoelectric MEMS acoustic generator in fig. 5 (a). With the unit devices in fig. 4 (b) and fig. 4 (c), the unit devices in the array structure in fig. 5 (b) may be other devices, such as the piezoelectric MEMS acoustic generator in fig. 4 (c) and/or the piezoelectric MEMS acoustic generator in fig. 4 (d), for example.

In the array structure of the piezoelectric MEMS acoustic generator in fig. 5 (c), compared with the array structure of the piezoelectric MEMS acoustic generator in fig. 5 (a), the layout of the array structure is that the single or multiple units in fig. 4 (e) and fig. 4 (f) are arranged, and the arranged devices are different unit arrangements, three, four, five unit devices and various different array structures, and it should be noted that the unit devices in the array structure in fig. 5 (b) may be other devices, such as the piezoelectric MEMS acoustic generator in fig. 2 and/or the piezoelectric MEMS acoustic generator in fig. 4 (a).

The array structure of the piezoelectric MEMS acoustic generator in fig. 5 (d) adopts the same structure of the piezoelectric MEMS acoustic generator, and the size parameters, the structural shape and the performance of the unit devices in the array are consistent. The array structure is arranged in a linear structure, has a horizontal axis and a vertical axis, can be arranged in the direction of the horizontal axis X to form two unit devices in fig. 4 (g) for array arrangement, and can be three unit devices and the like and various other unit arrangements; one unit device of 4 (g) may be arranged in the longitudinal axis Y direction, four unit devices, etc., and various other unit arrangements; meanwhile, the array structure can be linearly arranged on the horizontal axis and the vertical axis, and one unit device in 4 (g) is arranged in an array structure of 1x 1, 2x2, 3x3, 2x3, 3x2, 4x4 and the like. In the array structure in fig. 5 (c), the unit devices in 4 (h) may be used, or any of the piezoelectric MEMS acoustic generators in fig. 4 may be used, so as to form an array structure of a plurality of identical and/or different devices.

The array structure of the piezoelectric MEMS acoustic generator in fig. 5 (e), compared with the array structure of the piezoelectric MEMS acoustic generator in fig. 5 (a), has an array structure in which the horizontal axis and the vertical axis are arranged linearly, and the arrangement in the X direction of the horizontal axis is that the arrangement of single or multiple identical unit devices in fig. 4 (h), and the devices in the X direction of the horizontal axis are identical; the single or multiple identical unit device arrangements in fig. 4 (i) are arranged in the Y-direction of the longitudinal axis, the devices in the Y-direction of the longitudinal axis being identical; the unit devices in fig. 4 (h) and the unit devices in fig. 4 (i) may be arranged in a plurality of different array structures such as 2x2, 3x3, 4x4, 2x3, and 3x2, and it should be noted that the unit devices in the array structure in fig. 5 (e) may be other devices, such as the piezoelectric MEMS acoustic generator in fig. 4 (j) and/or the piezoelectric MEMS acoustic generator in fig. 4 (k).

The array structure of the piezoelectric MEMS acoustic generator in fig. 5 (f), compared with the array structure of the piezoelectric MEMS acoustic generator in fig. 5 (a), has an array structure in which the horizontal axis and the vertical axis are linearly arranged, and the arrangement in the direction of the horizontal axis X is that the arrangement of single or multiple unit devices in fig. 4 (j), and the devices in the direction of the horizontal axis X are different; an arrangement of single or multiple unit devices in the vertical axis Y direction shown in fig. 4 (k), the devices in the vertical axis Y direction being different; the unit devices in fig. 4 (l) may be arranged linearly along the horizontal axis and the vertical axis, the horizontal axis X direction is the unit device in fig. 4 (l), the vertical axis Y direction is the unit device in fig. 4 (j) and fig. 4 (k), and the unit devices in the array structure in fig. 5 (b) may be other devices, such as the piezoelectric MEMS acoustic generator in fig. 4 (g) and/or the piezoelectric MEMS acoustic generator in fig. 4 (h), for example, are arranged in a plurality of different array structures such as 2X2, 3X3, 4X4, 2X3, 3X2, etc.

The schematic illustration of polarization and electrical connection of a piezoelectric MEMS acoustic generator as shown in fig. 6 is provided below, where the directions of the arrows in the piezoelectric layers in the first piezoelectric composite unit 10a, the seventh piezoelectric composite unit 10g, and the fourth piezoelectric composite unit 10d are upward (Z-axis direction) and are the polarization directions of the piezoelectric layer 07. In the piezoelectric MEMS acoustic generator, the first piezoelectric composite unit 10a, the seventh piezoelectric composite unit 10g, and the fourth piezoelectric composite unit 10d are respectively connected to the bottom electrodes (e.g., the bottom electrode layer 06 and the top electrode layer 08) and the top electrodes are respectively connected to each other in parallel. The first piezoelectric composite unit 10a, the fourth piezoelectric composite unit 10d and the middle piezoelectric composite unit seven 10g are electrically connected, wherein the bottom electrode of the first piezoelectric composite unit 10g is connected with the top electrode of the first piezoelectric composite unit 10a and the top electrode of the fourth piezoelectric composite unit 10d, and the top electrode of the first piezoelectric composite unit 10g is connected with the bottom electrode of the first piezoelectric composite unit 10a and the bottom electrode of the fourth piezoelectric composite unit 10d in a series connection mode.

The polarization mode and electrical connection of a piezoelectric MEMS acoustic generator shown in fig. 7 are schematically shown, in which the direction of the arrow pointing upwards (Z-axis direction) in the piezoelectric layer is the polarization direction of the piezoelectric layer 07, and the positive and negative symbols in the upper and lower electrodes (e.g., bottom electrode 06 and top electrode 08) of the piezoelectric composite unit represent the positive and negative electrodes. As shown in the figure, the directions of the piezoelectric layers in the first piezoelectric composite unit 10a and the fourth piezoelectric composite unit 10d are upward (the Z-axis direction is upward) as the polarization directions of the piezoelectric layers, and the polarization directions of the piezoelectric layers in the seventh piezoelectric composite unit 10g are opposite to those of the first piezoelectric composite unit 10a and the fourth piezoelectric composite unit 10d, and are downward, so that the polarization directions of all the piezoelectric layers of the device are inconsistent. The piezoelectric composite units 10a and 10d with consistent polarization directions are electrically connected by respective bottom electrodes, and the respective top electrodes are connected in parallel. The piezoelectric composite unit seven 10g with inconsistent polarization direction is that the bottom electrode is connected with the bottom electrodes of the piezoelectric composite unit one 10a and the piezoelectric composite unit four 10d with opposite polarization, and the top electrode of the piezoelectric composite unit seven 10g is connected with the top electrodes of the piezoelectric composite unit one 10a and the piezoelectric composite unit four 10d with opposite polarization in parallel connection.

The mechanical resonance point of the piezoelectric MEMS sounder provided by the embodiment of the invention can be designed to be 20Hz-20kHz in the audible sound range, when the first-order resonance frequency of the piezoelectric MEMS sounder is 4-10KHz or 2-5KHz, the driving displacement of the vibrating membrane is larger under the driving of a piezoelectric signal, and the output sound pressure level of the MEMS sounder in the low-frequency range is larger, so that the piezoelectric MEMS sounder can be used in a low-frequency sounder. The mechanical resonance point of the piezoelectric MEMS sounder can be designed to be larger than 20kHz outside audible sound, the first harmonic and the third harmonic of the sound of the piezoelectric MEMS sounder are outside the audible frequency range, the nonlinearity of the sounder is low, the THD is low, and the piezoelectric MEMS sounder can be used in a high-frequency sounder.

The piezoelectric MEMS sounder is a piezoelectric MEMS sounder with rigid-flexible combination, can be used for generating sound waves in an audible wavelength range and/or an ultrasonic range, and forms a vibrating film of a device through the combination of rigid-flexible materials, and a plurality of piezoelectric composite units are arranged on the vibrating film and connected with a substrate. Under the action of electric drive, the piezoelectric composite unit enables the vibration film with rigidity and flexibility to easily generate larger-amplitude vibration, thereby obtaining larger deflection, driving force or deflection and improving the low-frequency emission sound pressure level of the piezoelectric MEMS sounder. Meanwhile, the flexible material fills the rigid area, so that the moving mass of the vibrating membrane is reduced, when the forces of the motors are equal, the lower the mass is, the higher the acceleration of the vibrating membrane is, and the high sound pressure level SPL is realized at high frequency.

The piezoelectric MEMS sounder comprises a piezoelectric composite layer unit and a rigid-flexible vibration film, wherein the piezoelectric composite layer unit and the rigid-flexible vibration film form a driving and sounding unit of the piezoelectric MEMS sounder, SOI top silicon of a substrate is etched through an MEMS technology to form a groove structure, and the groove structure is filled or covered with a flexible material to form the rigid-flexible combined vibration film. Etching the piezoelectric composite unit and SOI top silicon is helpful for releasing stress of each film layer, and improving vibration deflection and output sound pressure, so that the emission sensitivity of the piezoelectric MEMS sounder is improved, and the preparation process is simple; in addition, the vibration film combining rigidity and flexibility is adopted, so that the vibration film has better rigidity and sealing performance, and the structure that the partial area is made of rigid materials and the partial area is made of flexible materials can prevent the problem of low-frequency output sound pressure level caused by sound leakage while obtaining larger deflection, driving force or deflection. Meanwhile, the moving mass of the vibrating membrane is reduced, and when the forces of the motors are equal, the lower the mass is, the higher the acceleration of the vibrating membrane is, and the high sound pressure level SPL is realized at high frequency.

The following provides a schematic diagram of simulation results of a piezoelectric MEMS acoustic generator filled with no flexible material as shown in fig. 8, and a schematic diagram of simulation results of a piezoelectric MEMS acoustic generator filled with flexible material as shown in fig. 9, where fig. 8 and fig. 9 are comparison results of piezoelectric MEMS acoustic generators with the same structure under the same excitation, the piezoelectric MEMS acoustic generator has a hexagonal structure, the side length of the hexagon is 2.5mm, and the piezoelectric acoustic generator has a single piezoelectric layer structure: the SOI substrate silicon wafer, si/PT/PZT/PT=5 μm/0.15 μm/2 μm/0.15 μm, the flexible material is a dry film material-flexfin SA, the external electrode structure excites piezoelectric DC:15V.

Under the same excitation, the MEMS piezoelectric speaker with the same structure is simulated by the device with or without the flexible material, so that the simulation results are shown in fig. 8 and 9, and it can be seen from the figures: the resonant frequency of the device filled with the flexible material is 17.17kHz, and the maximum displacement of the vibrating film is 24.9um. The device resonance frequency without filling the flexible material was 21.16kHz, and the maximum displacement of the vibrating membrane was 17.6um. Comparing the two, the device filled with the flexible material has reduced resonant frequency, better elasticity and easy generation of larger-amplitude vibration under the action of electric drive, thereby improving the vibration amplitude and the emission sound pressure level of the piezoelectric MEMS sounder.

Above-mentioned piezoelectricity MEMS sound generator, fluting is carried out on piezoelectricity MEMS sound generator's rigid material silicon, fills and covers with flexible material, forms just flexible vibration film that combines together, can prevent that the device during operation from revealing, and the vibration film that just combines together simultaneously can promote piezoelectricity MEMS sound generator's low frequency SPL. In addition, the larger the effective radiation area is, the higher the generated sound pressure is, so that the piezoelectric MEMS sounder units are distributed in different forms to form various array structures, the sounding area of the sounder is increased, and the sound pressure level output of the device is improved. The vibration film with rigidity and flexibility reduces the moving mass of the vibration film, and when the forces of the motors are equal, the higher the acceleration of the vibration film is, the higher the output sound pressure level at medium and high frequencies can be improved, and the problem of medium frequency valley of the piezoelectric MEMS sounder is solved. The greater the displacement of the radiating area of the vibrating membrane, the higher the sound pressure generated. The performance of the piezoelectric MEMS sounder is closely related to the relation between the polarization direction of the piezoelectric layer and the applied electric field, and the relation between the piezoelectric layer and the applied electric field is optimized to maximize the output deflection of the piezoelectric MEMS sounder and maximize the output sound pressure level.

The embodiment of the invention also provides a manufacturing method of the piezoelectric MEMS sounder, which comprises the following steps:

step 1, respectively thermally oxidizing the upper surface and the lower surface of a preset substrate to grow an insulating layer; wherein, include insulating buried layer in the basement.

The preset substrate can be an SOI substrate, a silicon substrate, glass, sapphire and the like; taking a preset substrate as an SOI substrate, the SOI substrate is usually provided with an insulating buried layer, which may also be called a BOX layer, the BOX layer may divide the substrate into two parts, the BOX layer may correspond to the SOI top layer silicon, and the BOX layer may correspond to the SOI substrate silicon, so that parasitic junction capacitance may be reduced through the BOX layer; the insulating layer may be silicon dioxide, and the thickness of the silicon dioxide is usually 0.1 μm to 5 μm, or may be an insulating material such as silicon nitride or aluminum oxide.

Step 2, sequentially depositing a seed layer, a bottom electrode layer, an intermediate layer and a top electrode layer on an insulating layer on the upper surface of a substrate from bottom to top to obtain a first device; the middle layer is a piezoelectric layer, or the middle layer is formed by overlapping and stacking a plurality of piezoelectric layers and a plurality of electrode layers; the upper layer of the bottom electrode layer and the lower layer of the top electrode layer are both piezoelectric layers.

The seed layer can be amorphous silicon and other materials, and is formed at the early stage of electrodeposition, so that the high-quality growth of the piezoelectric layer is facilitated. Specifically, a seed layer can be grown on an insulating layer on the upper surface of a substrate, a bottom electrode layer is deposited on the seed layer, and then an intermediate layer and a top electrode layer are grown on the bottom electrode layer; for example, the piezoelectric layer may be a single crystal PZT thin film having a thickness of 2um, a top electrode of Pt, a thickness of 0.15um, and the like.

Step 3, processing the bottom electrode layer, the middle layer and the top electrode layer in the first device to form a plurality of piezoelectric composite units, and obtaining a processed second device; wherein, at least one piezoelectricity compound unit sets up in the central region of basement upper surface, and other piezoelectricity compound units except at least one piezoelectricity compound unit set up in the marginal region of basement upper surface.

Specifically, the bottom electrode layer, the middle layer and the top electrode layer in the first device can be etched layer by layer in a dry etching mode, a wet etching mode and the like, so that a plurality of piezoelectric composite units are formed.

Step 4, processing the second device to obtain a piezoelectric MEMS sounder; the bottom center area of the substrate of the piezoelectric MEMS sounder is provided with a cavity, the upper part of the substrate corresponding to the cavity is provided with at least one groove except the area where each piezoelectric composite unit is located, the preset area in each groove and at the opening position is covered and filled with flexible materials, and the upper area of the substrate with the at least one groove forms a vibrating film.

According to the manufacturing method of the piezoelectric MEMS sounder, insulating layers are grown on the upper surface and the lower surface of a preset substrate respectively through thermal oxygen; wherein, the substrate comprises an insulating buried layer; sequentially depositing a seed layer, a bottom electrode layer, an intermediate layer and a top electrode layer on an insulating layer on the upper surface of a substrate from bottom to top to obtain a first device; the middle layer is a piezoelectric layer, or the middle layer is formed by overlapping and stacking a plurality of piezoelectric layers and a plurality of electrode layers; the upper layer of the bottom electrode layer and the lower layer of the top electrode layer are both piezoelectric layers; processing the bottom electrode layer, the middle layer and the top electrode layer in the first device to form a plurality of piezoelectric composite units, so as to obtain a processed second device; wherein, at least one piezoelectric composite unit is arranged in the central area of the upper surface of the substrate, and other piezoelectric composite units except for the at least one piezoelectric composite unit are arranged in the edge area of the upper surface of the substrate; processing the second device to obtain a piezoelectric MEMS sounder; according to the mode, the seed layer, the bottom electrode layer, the middle layer and the top electrode layer can be sequentially deposited and formed on the upper surface of the substrate on which the insulating layer grows, the piezoelectric MEMS sounder can be obtained through processing, the manufacturing process is simple, the sounder is provided with the groove in the upper area of the substrate, stress of the piezoelectric composite unit and the vibrating film is released, flexible materials are covered and filled in the groove, sound leakage can be prevented, meanwhile, the quality of the vibrating film can be reduced, and then the sound pressure level is improved.

The invention provides a method for manufacturing a piezoelectric MEMS sounder, which is realized on the basis of the method in the embodiment, and comprises the following steps:

firstly, respectively thermally oxidizing the upper surface and the lower surface of a preset substrate to grow an insulating layer; wherein, include insulating buried layer in the basement. As shown in fig. 10, a cross-sectional view of a substrate with an insulating layer grown thereon is shown, wherein the upper and lower black areas are the insulating layers.

Sequentially depositing a seed layer, a bottom electrode layer, an intermediate layer and a top electrode layer on an insulating layer on the upper surface of a substrate from bottom to top to obtain a first device; the middle layer is a piezoelectric layer, or the middle layer is formed by overlapping and stacking a plurality of piezoelectric layers and a plurality of electrode layers; the upper layer of the bottom electrode layer and the lower layer of the top electrode layer are both piezoelectric layers.

A schematic cross-section of the substrate after growth of the bottom electrode layer is shown in fig. 11, and a schematic cross-section of the substrate after growth of the intermediate layer and the top electrode layer is shown in fig. 12, the intermediate layer being illustrated in fig. 12 by way of example as a single piezoelectric layer.

And thirdly, performing patterning treatment on the top electrode layer of the first device to obtain a third device after the patterning treatment. A schematic cross-sectional view of a patterned top electrode is shown in fig. 13.

And step four, performing dry etching treatment on the intermediate layer and the bottom electrode layer of the third device according to a preset etching angle to obtain a treated fourth device. A schematic cross-sectional view of the intermediate layer and bottom electrode layer after dry etching is shown in fig. 14. Dry method IBE etches PZT & bottom electrode, PZT piezoelectric film & bottom electrode etching angle, step coverage of passivation layer is facilitated, PZT piezoelectric film & bottom electrode etching angle: 30 ° -60 °, over-etch <10%; PZT sidewall roughness: the smaller the better the goal is that there is no delamination between the slice PZT and the passivation layer after the passivation layer deposition is completed.

And fifthly, carrying out wet etching treatment on the intermediate layer of the fourth device to obtain a treated second device. A schematic cross-sectional view after wet etching of the intermediate layer is shown in fig. 15. The critical dimension between the layers after the top electrode, the piezoelectric layer and the bottom electrode layer are patterned is smaller than 3um. And the redundant piezoelectric layer and electrode layer in the vibration area are completely removed, so that the symmetry of the structure is maintained, and the consistency of the vibration mode is ensured.

Depositing a passivation layer on the second device to isolate the electrical connection of each top electrode layer, and performing graphical treatment on the passivation layer to form a bonding pad area so as to lead out the bottom electrode layer and/or the top electrode layer of each piezoelectric composite unit, thereby obtaining a fifth device;

As shown in a schematic cross-sectional view of fig. 16 after passivation layer deposition and patterning, passivation layer deposition is performed on the second device, for example, the passivation layer may be silicon dioxide, with a thickness of 0.75um, etc., and patterning is performed on the deposited passivation layer, so that a bottom electrode layer and/or a top electrode layer of a corresponding piezoelectric composite unit may be led out, which is specifically related to the position, the function, etc. of the piezoelectric composite unit. In actual implementation, through holes can be formed in the passivation layer through etching, the electrode layer is led out through PAD formed by metal layer deposition, and a grounding and driving welding disk position is formed and used for gold wire welding of a PCB circuit.

And seventhly, depositing a metal layer on each bonding pad area in the fifth device to form bonding pads, and obtaining the sixth device.

As shown in fig. 17, which is a schematic cross-sectional view of a deposited and patterned metal line, a metal line deposition and patterning process may be performed on each pad area, and a liftoff process may be used, where the material may be, but is not limited to, one of the following materials or a combination thereof: gold, copper, aluminum, and other metallic materials, or conductive alloy materials, etc., for example, the deposited material may be gold AU, with a thickness of 0.75 μm; specifically, the top electrode layer and the bottom electrode layer can be led out to the welding disk PAD and the composite piezoelectric unit connected with each area,

And step eight, processing the sixth device to obtain the piezoelectric MEMS sounder.

The eighth step can be specifically realized by the following steps a to B:

step A, etching the upper surface of a sixth device except the area where each piezoelectric composite unit is located at the position of a central area close to the upper surface to form at least one groove, and covering and filling flexible materials in each groove and a preset area of the opening position to obtain a seventh device;

as shown in fig. 18, taking a substrate as an example of an SOI material, a DRIE (Deep Reactive Ion Etching ) process may be used to etch the SOI top silicon, where the etching thickness is 5um, and a good aspect ratio may be obtained. The shape of the etched groove may be: the inner ring-shaped and the outer ring-shaped and long grooves are formed, but the inner ring-shaped and the outer ring-shaped and the long grooves can also be etching area layers with other shapes, including square, rectangle or polygon, and the etching thickness is between 1um and 15um, and the width of the ring in the circular or square annular groove is between 1um and 1500 um. A schematic cross-sectional view of a plated flexible material is shown in fig. 19, wherein a predetermined area in each recess and the opening is filled with a flexible dry film material. The flexible dry film material not only can cover and fill the notch gap, but also can serve as an insulating layer material to cover the metal connecting wire, thereby playing roles of electric insulation, water resistance and the like.

The flexible dry film material is selected to be compatible with MEMS technology, graphical, and the like, works for a long time, resists aging, and has good mechanical property and temperature stability. The flexible dry film material requires a certain elongation and the CTE (Coefficient of Thermal Expansion ) difference between the material and the substrate minimizes wafer warpage.

Step B, thinning and etching the cavity treatment are carried out on the bottom surface of the substrate of the seventh device, and a piezoelectric MEMS sounder is obtained; the cavity obtained by etching is positioned in the bottom center area of the substrate.

Taking the substrate as the SOI material as an example, as shown in a cross-sectional schematic view of fig. 20 after wafer thinning, wafer thinning can be performed on the seventh device, in this embodiment, wafer thinning CMP (Chemical-Mechanical Planarization, chemical mechanical polishing) to 250 μm is beneficial to thinning the thickness of the device, and the etching time of back cavity DRIE can be reduced. And (3) temporarily bonding the wafer and the carrier substrate by adopting bonding glue to thin the wafer, and then removing the bonding glue. Carrying out DRIE etching on the thinned seventh device to form a back cavity, releasing the back cavity through process hollowing to form a cavity structure, and etching a BOX layer of the SOI; and etching the back cavity and the BOX layer of the SOI by adopting a double-sided exposure technology DRIE, thereby obtaining the piezoelectric MEMS sounder, as shown in figure 1.

The DRIE etch back cavity etch accuracy of the device has a significant impact on device performance, especially width dimension variations. Therefore, strict control technology is required for the accuracy of the alignment marks, whether the etching of the device is accurate, whether the etching is complete and whether the over etching exists. Back cavity etching angle is required: 90 degrees plus or minus 1.5 degrees, no residue and no over etching.

The MEMS acoustic generator may be used to generate acoustic waves in the audible wavelength range and/or the ultrasonic range. Sounders that can be used in MEMS technology for applications such as generating music, full frequency of speech, or specifically for high-pitched sound, such as sound waves in the ultrasonic range, can be used for example in ultrasonic detection devices or ultrasonic devices for testing ultrasonic waves.

The manufacturing method of the piezoelectric MEMS sounder is simple in manufacturing process, and the sounder is provided with the grooves in the upper area of the substrate, so that stress of the piezoelectric composite unit and stress of the vibrating membrane can be released, flexible materials are filled in the grooves, sound leakage can be prevented, meanwhile, the quality of the vibrating membrane can be reduced, and further the sound pressure level is improved.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.

Claims

1. A piezoelectric MEMS acoustic generator, comprising: a substrate and a plurality of piezo-electric composite units; the bottom center area of the substrate is provided with a cavity, and the upper surface of the substrate is provided with an insulating layer; at least one piezoelectric composite unit is arranged in the central area of the upper surface of the substrate, and other piezoelectric composite units except for the at least one piezoelectric composite unit are arranged in the edge area of the upper surface of the substrate; the preset position of each piezoelectric composite unit is provided with a bonding pad formed by depositing a metal layer, and other areas of each piezoelectric composite unit except the preset position are deposited with passivation layers;

at least one groove is formed in other areas except the area where each piezoelectric composite unit is located on the upper portion of the substrate corresponding to the cavity, the preset area in each groove and at the opening position is covered and filled with flexible materials, and a vibrating film is formed in the upper area of the substrate with the at least one groove.

2. The piezoelectric MEMS acoustic generator of claim 1 wherein,

each piezoelectric composite unit comprises a bottom electrode layer, an intermediate layer and a top electrode layer from bottom to top in sequence; the middle layer is a piezoelectric layer, or the middle layer is formed by overlapping and stacking a plurality of piezoelectric layers and a plurality of electrode layers; wherein, the upper layer of the bottom electrode layer and the lower layer of the top electrode layer are both piezoelectric layers.

3. The piezoelectric MEMS acoustic generator of claim 1, wherein each of the grooves is completely filled with the flexible material.

4. A loudspeaker comprising a plurality of piezoelectric MEMS acoustic generators as claimed in any one of claims 1-3.

5. The loudspeaker of claim 4, wherein a plurality of the piezoelectric MEMS acoustic generators are arranged in a predetermined arrangement; wherein, the preset arrangement mode comprises at least one of the following: a honeycomb arrangement mode, a horizontal axis linear arrangement mode and a vertical axis linear arrangement mode.

6. A method of making a piezoelectric MEMS acoustic generator, the method comprising:

respectively thermally oxidizing the upper surface and the lower surface of a preset substrate to grow an insulating layer; wherein the substrate comprises an insulating buried layer;

sequentially depositing a seed layer, a bottom electrode layer, an intermediate layer and a top electrode layer on an insulating layer on the upper surface of the substrate from bottom to top to obtain a first device; the middle layer is a piezoelectric layer, or the middle layer is formed by overlapping and stacking a plurality of piezoelectric layers and a plurality of electrode layers; the upper layer of the bottom electrode layer and the lower layer of the top electrode layer are both piezoelectric layers;

Processing the bottom electrode layer, the middle layer and the top electrode layer in the first device to form a plurality of piezoelectric composite units, so as to obtain a processed second device; wherein at least one piezoelectric composite unit is arranged in the central area of the upper surface of the substrate, and other piezoelectric composite units except at least one piezoelectric composite unit are arranged in the edge area of the upper surface of the substrate;

processing the second device to obtain a piezoelectric MEMS sounder; the piezoelectric MEMS sounder comprises a substrate, a piezoelectric composite unit, a flexible material, a vibrating film, a cavity, a plurality of grooves and a plurality of openings, wherein the bottom center area of the substrate of the piezoelectric MEMS sounder is provided with the cavity, the upper portion of the substrate corresponding to the cavity is provided with the at least one groove except the area where each piezoelectric composite unit is located, the preset area in each groove and at the opening position is covered and filled with the flexible material, and the vibrating film is formed in the upper area of the substrate with the at least one groove.

7. The method of claim 6, wherein processing the bottom electrode layer, the intermediate layer, and the top electrode layer in the first device to form a plurality of piezo-electric composite elements, the step of obtaining a processed second device comprises:

Patterning the top electrode layer of the first device to obtain a third device after patterning;

carrying out dry etching treatment on the intermediate layer and the bottom electrode layer of the third device according to a preset etching angle to obtain a treated fourth device;

and carrying out wet etching treatment on the intermediate layer of the fourth device to obtain a treated second device.

8. The method of claim 7, wherein the range of preset etching angles is: 30-60 deg..

9. The method of claim 6, wherein the step of processing the second device to obtain a piezoelectric MEMS acoustic generator comprises:

depositing a passivation layer on the second device to isolate electrical connection of each top electrode layer, and performing graphical treatment on the passivation layer to form a pad area so as to lead out a bottom electrode layer and/or a top electrode layer of each piezoelectric composite unit, thereby obtaining a fifth device;

depositing a metal layer on each bonding pad area in the fifth device to form bonding pads, so as to obtain a sixth device;

and processing the sixth device to obtain the piezoelectric MEMS sounder.

10. The method of claim 9, wherein the step of processing the sixth device to obtain a piezoelectric MEMS acoustic generator comprises:

Etching the upper surface of the sixth device except the central area of the other areas except the area where each piezoelectric composite unit is located to form at least one groove, and covering and filling flexible materials in each groove and in a preset area of the opening position to obtain a seventh device;

thinning and etching the cavity treatment are carried out on the bottom surface of the substrate of the seventh device, so that a piezoelectric MEMS sounder is obtained; and the cavity obtained by etching is positioned in the bottom center area of the substrate.