MEMS acoustic transducer and manufacturing method thereof

Abstract

The present invention provides a MEMS acoustic transducer and a manufacturing method, comprising: a substrate, the upper surface of which is covered with a dry film layer, a transducer diaphragm assembly is arranged above the dry film layer, including: a support layer and at least one piezoelectric composite layer; a cavity is formed between the middle area of ​​the substrate and the middle area of ​​the dry film layer, and a diaphragm structure is formed in the area opposite to the cavity in the transducer diaphragm assembly; the shape of the dry film layer is obtained by graphical processing. In the MEMS acoustic transducer, a cavity is formed by the middle area of ​​the substrate and the middle area of ​​the dry film layer. Since the inner side surface of the dry film corresponding to the dry film layer in the inner side surface of the cavity is perpendicular to the diaphragm structure, and the size of the middle area of ​​the dry film layer is a preset target size, the phenomenon of over-etching or under-etching the top of the cavity can be avoided, the accuracy and consistency of the cavity etching are improved, and then the performance of the MEMS acoustic transducer device and the yield rate of the on-chip devices of the entire wafer can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of acoustic transducers, and in particular to a MEMS acoustic transducer and a manufacturing method thereof. Background Art

[0002] MEMS (Micro-Electro-Mechanical System) acoustic transducer devices usually use the MEMS bulk silicon process DRIE (Deep Reactive Ion Etching) to obtain silicon grooves or back cavity structures. However, due to the complexity of the DRIE process and the many process parameters, each process parameter will affect the etching morphology (sidewalls and bottom), verticality and in-plane uniformity to varying degrees. It is usually difficult to fully meet the morphology, verticality and in-plane uniformity. Generally, based on the performance requirements of a specific device, certain morphology requirements are sacrificed to meet high verticality requirements while meeting the in-plane uniformity, and vice versa. Therefore, for MEMS acoustic transducer devices with cavity structures, in the process of DRIE silicon grooves and silicon cavities, there will be problems such as rough etching bottom, grassy sidewalls, and poor verticality, which easily leads to over-etching or incomplete etching of the top of the cavity, resulting in inaccurate cavity etching and poor consistency, which greatly affects the performance of the MEMS acoustic transducer device and the yield of the on-chip device of the entire wafer. Summary of the invention

[0003] The object of the present invention is to provide a MEMS acoustic transducer and a manufacturing method thereof, so as to improve the accuracy and consistency of cavity etching, improve the performance of the MEMS acoustic transducer, and improve the on-chip device yield of the entire wafer.

[0004] A MEMS acoustic transducer provided by the present invention comprises: a substrate, the upper surface of the substrate is covered with a dry film layer, a transducer diaphragm assembly is arranged above the dry film layer, and the transducer diaphragm assembly comprises: a supporting layer and at least one piezoelectric composite layer; a middle area of ​​the substrate and a middle area of ​​the dry film layer form a cavity, and in the transducer diaphragm assembly, an area opposite to the cavity forms a diaphragm structure; wherein the shape of the dry film layer is obtained by graphical processing; in the inner side surface of the cavity, the inner side surface of the dry film corresponding to the dry film layer is perpendicular to the diaphragm structure; and the size of the middle area of ​​the dry film layer is a preset target size.

[0005] Furthermore, in the inner side surface of the cavity, the inner side surface of the dry film corresponding to the dry film layer is aligned or not aligned with the inner side surface of the substrate corresponding to the substrate.

[0006] Furthermore, the support layer is arranged on the upper surface of the dry film layer; each piezoelectric composite layer is arranged on the upper surface of the support layer; a passivation layer is deposited on the upper surface of the support layer except for each piezoelectric composite layer, and on the upper surface and each side of each piezoelectric composite layer.

[0007] Furthermore, a passivation layer is deposited on the lower surface of each piezoelectric composite layer, and each piezoelectric composite layer deposited with the passivation layer is arranged on the upper surface of the dry film layer, and a support layer is covered above each piezoelectric composite layer.

[0008] Furthermore, a plurality of gaps are provided on the piezoelectric composite layer and the support layer.

[0009] Furthermore, in the diaphragm structure, a preset position of the support layer close to the inner boundary of the piezoelectric composite layer is etched into a spring structure.

[0010] Furthermore, the dry film layer and the support layer are made of the same material.

[0011] The present invention provides a method for manufacturing a MEMS acoustic transducer, the method comprising: covering a dry film layer on the upper surface of a preset first substrate; performing a patterning process on the dry film layer to obtain a first device; thermally growing an oxide layer on the upper surface and the lower surface of a preset second substrate respectively to obtain a second substrate with an oxide layer; depositing a transducer diaphragm assembly on the oxide layer on the upper surface of the second substrate with the oxide layer to obtain a second device, so as to obtain a MEMS acoustic transducer based on the first device and the second device; wherein the transducer diaphragm assembly comprises: a supporting layer and at least one piezoelectric composite layer; a cavity is formed between the middle area of ​​the substrate of the MEMS acoustic transducer and the middle area of ​​the dry film layer, and a diaphragm structure is formed in the area opposite to the cavity in the transducer diaphragm assembly; wherein the shape of the dry film layer is obtained by patterning; in the inner side surface of the cavity, the inner side surface of the dry film corresponding to the dry film layer is perpendicular to the diaphragm structure; and the size of the middle area of ​​the dry film layer is a preset target size.

[0012] Furthermore, a transducer diaphragm assembly is deposited on the oxide layer on the upper surface of the second substrate with the oxide layer to obtain a second device, and the steps of obtaining a MEMS acoustic transducer based on the first device and the second device include: depositing a bottom electrode layer, an intermediate layer and a top electrode layer in sequence from bottom to top on the oxide layer on the upper surface of the second substrate with the oxide layer to obtain a third device; depositing a support layer on the upper surface of the third device to obtain a fourth device; flipping the fourth device and bonding the flipped fourth device to the upper surface of the first device so that the dry film layer of the first device is combined with the support layer of the fourth device to obtain a fifth device; removing the second substrate with the oxide layer in the fifth device The bottom of the sixth device is formed into a sixth device; the bottom electrode layer, the middle layer and the top electrode layer in the sixth device are patterned to form at least one piezoelectric composite layer to obtain a patterned seventh device; a passivation layer is deposited on the upper surface of the seventh device to isolate the electrical connection of each top electrode layer, and the passivation layer is patterned to form a pad area to lead out the bottom electrode layer and / or the top electrode layer of each piezoelectric composite unit to obtain an eighth device; a metal layer is deposited on each pad area in the eighth device to form a pad, and a metal wire is bonded to obtain a ninth device; the bottom surface of the first substrate of the ninth device is thinned and a cavity is etched to obtain a MEMS acoustic transducer.

[0013] Furthermore, a transducer diaphragm assembly is deposited on the oxide layer on the upper surface of the second substrate with the oxide layer to obtain a second device, and the steps of obtaining a MEMS acoustic transducer based on the first device and the second device include: depositing a support layer on the oxide layer on the upper surface of the second substrate with the oxide layer to obtain a tenth device; depositing a bottom electrode layer, an intermediate layer and a top electrode layer in sequence from bottom to top on the support layer of the tenth device to obtain an eleventh device; patterning the bottom electrode layer, the intermediate layer and the top electrode layer in the eleventh device to form at least one piezoelectric composite layer to obtain a patterned twelfth device; and depositing a top electrode layer on the upper surface of the twelfth device. A passivation layer is deposited on the surface of the first device to isolate the electrical connection of each top electrode layer, and the passivation layer is patterned to form a pad area to lead out the bottom electrode layer and / or the top electrode layer of each piezoelectric composite unit to obtain a thirteenth device; a metal layer is deposited on each pad area in the thirteenth device to form a pad, and a metal wire is bonded to obtain a fourteenth device; the fourteenth device is flipped over, and the flipped fourteenth device is bonded to the upper surface of the first device to combine the dry film layer of the first device with the passivation layer of the fourteenth device to obtain a fifteenth device; the bottom surface of the first substrate of the fifteenth device is thinned and a cavity is etched to obtain a MEMS acoustic transducer.

[0014] The present invention provides a MEMS acoustic transducer and a manufacturing method, wherein the MEMS acoustic transducer comprises: a substrate, the upper surface of the substrate is covered with a dry film layer, a transducer diaphragm assembly is arranged above the dry film layer, and the transducer diaphragm assembly comprises: a support layer and at least one piezoelectric composite layer; a cavity is formed between the middle region of the substrate and the middle region of the dry film layer, and a diaphragm structure is formed in the region opposite to the cavity in the transducer diaphragm assembly; wherein the shape of the dry film layer is obtained by graphical processing; in the inner side surface of the cavity, the inner side surface of the dry film layer corresponding to the dry film layer is perpendicular to the diaphragm structure; and the size of the middle region of the dry film layer is a preset target size. The cavity is formed by the middle region of the substrate and the middle region of the dry film layer, and since in the inner side surface of the cavity, the inner side surface of the dry film layer corresponding to the dry film layer is perpendicular to the diaphragm structure, and the size of the middle region of the dry film layer is a preset target size, the phenomenon of over-etching or under-etching the top of the cavity can be avoided, and the accuracy and consistency of the cavity etching are improved, thereby improving the performance of the MEMS acoustic transducer device and the yield rate of the on-chip device of the entire wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 A schematic diagram of a cross-sectional view of a MEMS acoustic transducer provided in an embodiment of the present invention;

[0017] Figure 2 A schematic diagram of a cross-sectional view of a MEMS acoustic transducer provided in an embodiment of the present invention;

[0018] Figure 3 A schematic diagram of a cross-sectional view of another MEMS acoustic transducer provided in an embodiment of the present invention;

[0019] Figure 4 A schematic diagram of a cross-sectional view of another MEMS acoustic transducer provided in an embodiment of the present invention;

[0020] FIG5( a ) is a schematic structural diagram of a piezoelectric composite layer provided in an embodiment of the present invention;

[0021] FIG5( b ) is a schematic structural diagram of a piezoelectric composite layer provided in an embodiment of the present invention;

[0022] FIG5( c ) is a schematic structural diagram of a piezoelectric composite layer provided in an embodiment of the present invention;

[0023] FIG6( a) is a front view of a MEMS acoustic transducer provided in an embodiment of the present invention;

[0024] FIG6( b ) is a front view of another MEMS acoustic transducer provided in an embodiment of the present invention;

[0025] FIG6( c ) is a front view of another MEMS acoustic transducer provided in an embodiment of the present invention;

[0026] FIG. 7( a ) is a schematic diagram of an array of MEMS acoustic transducers provided in an embodiment of the present invention.

[0027] FIG7( b ) is a schematic diagram of another array of MEMS acoustic transducers provided in an embodiment of the present invention;

[0028] FIG7( c ) is a schematic diagram of another array of MEMS acoustic transducers provided in an embodiment of the present invention;

[0029] FIG8( a) is a schematic diagram of a simulation frequency provided by an embodiment of the present invention;

[0030] FIG8( b ) is a schematic diagram of another simulation frequency provided by an embodiment of the present invention;

[0031] FIG8( c ) is a schematic diagram of another simulation frequency provided by an embodiment of the present invention;

[0032] FIG9( a) is a schematic diagram of a simulated vibration displacement provided by an embodiment of the present invention;

[0033] FIG9( b ) is a schematic diagram of another simulated vibration displacement provided by an embodiment of the present invention;

[0034] FIG9( c ) is a schematic diagram of another simulated vibration displacement provided by an embodiment of the present invention;

[0035] Fig.10 A schematic diagram of a first substrate covered with a dry film layer provided by an embodiment of the present invention;

[0036] Fig.11 A schematic diagram of a first device provided by an embodiment of the present invention;

[0037] Fig.12 A schematic diagram of a second substrate with an oxide layer provided by an embodiment of the present invention;

[0038] Fig.13 A schematic diagram of a third device provided by an embodiment of the present invention;

[0039] Fig.14 A schematic diagram of a fourth device provided by an embodiment of the present invention;

[0040] Fig.15 A schematic diagram of a fifth device provided by an embodiment of the present invention;

[0041] Fig.16 A schematic diagram of a sixth device provided by an embodiment of the present invention;

[0042] Fig.17 A schematic diagram of an eighth device provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0043] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] In recent years, MEMS acoustic transducers, such as piezoelectric speakers, piezoelectric microphones, piezoelectric micromachined ultrasonic transducers PMUT (Piezoelectric Micromachined Ultrasonic Transducer) and other actuators or sensors have become a research hotspot. Compared with traditional transducer devices, new piezoelectric transducer devices manufactured using MEMS processing technology have the characteristics of small size and thin thickness in structure. The products can be mass-produced, and fully automated assembly has cost advantages. The devices use MEMS technology, have good performance consistency and low power consumption, and are easy to integrate and intelligent.

[0045] This type of MEMS acoustic transducer usually uses MEMS bulk silicon process deep reactive ion etching (DRIE) to obtain silicon groove or back cavity structure. However, due to the complexity of the DRIE process and the many process parameters, including etching gas flow, passivation gas flow, etching time / passivation time ratio, reaction chamber pressure, RF power and flat electrode power, each process parameter will affect the etching morphology (sidewall and bottom), verticality and in-plane uniformity to varying degrees. It is usually difficult to meet all the morphology, verticality and in-plane uniformity. Generally, based on the performance requirements of a specific device, on the premise of meeting the in-plane uniformity, certain morphology requirements are sacrificed to meet the high verticality requirements, and vice versa. Therefore, for MEMS piezoelectric devices with cavity structures, during the DRIE silicon groove and silicon cavity process, there will be problems such as rough etching bottom, rough sidewalls, and poor verticality. In addition, due to inconsistent etched cavity sizes and different distribution positions of the cavities across the wafer, the top of the cavity may be over-etched or not completely etched, resulting in inaccurate and inconsistent cavity etching, which has a great impact on device performance. Over-etching or incomplete etching will affect the vibration frequency and sensitivity of the device, and in severe cases may damage the device structure and cause it to fail. In addition to affecting the performance of a single device, the unevenness of cavity etching across the wafer will also affect the consistency of device performance and the yield of on-chip devices on the entire wafer.

[0046] For example, Figure 1 The schematic diagram of a cross-sectional view of a MEMS acoustic transducer shown in the figure shows that in the cross-sectional view, the left side of the top of the cavity is located on the left side of the preset etching position line, and there is a problem of over-etching; in the cross-sectional view, the right side of the top of the cavity is located on the left side of the preset etching position line, and there is a problem of incomplete etching.

[0047] The related art provides a method for manufacturing a semiconductor structure, including: providing a substrate with an annular groove; forming a barrier layer on the upper surface of the substrate, the barrier layer filling the annular groove; forming a functional layer above the barrier layer; etching the lower surface of the substrate to form a cavity, and stopping etching when the functional layer is reached. This solution has the following problems: 1) A barrier layer is formed to fill the annular groove, and DRIE etches the lower surface of the substrate to form a cavity. Since the barrier layer is thin, DRIE cannot stop at the barrier layer, and over-etching occurs. 2) The depth-to-width ratio of the structure of the etching annular groove cannot be too large, and it is not easy to fill the annular groove by depositing and forming a barrier layer.

[0048] The related art also provides another solution to the problem of piezoelectric MEMS cavity etching, in which a ring groove structure is etched by DRIE on substrate A, with an etching depth of 1-10um. Thermal oxidation deposition is performed on the upper and lower surfaces of substrate B to form a barrier layer BOX, and then a piezoelectric composite layer and a device layer are formed above the barrier layer BOX. Then wafer B and wafer A are bonded by bonding, the silicon and oxide layer of substrate B are removed, and the piezoelectric composite layer is patterned. Finally, DRIE etches the lower surface of the substrate to form a cavity until the etching barrier layer is stopped. This solution has the following problems: 1) Etching a silicon groove on the upper surface of substrate A to form a cavity structure can easily cause the entire wafer to bend and deform. When the silicon groove area is large and the etching is deep, the wafer may even bend and cannot be successfully bonded to substrate B. 2) After substrate A is bonded to substrate B, due to the large area of ​​the silicon groove and the influence of the subsequent MEMS process temperature, the formed device diaphragm is easily concave or even broken.

[0049] In summary, the related technology is still prone to over-etching or incomplete etching of the top of the cavity, resulting in inaccurate and poor consistency of cavity etching, which greatly affects the performance of the MEMS acoustic transducer device. Based on this, an embodiment of the present invention provides a MEMS acoustic transducer and a manufacturing method, which can be applied to applications that need to improve the accuracy and consistency of cavity etching and improve the performance of the MEMS acoustic transducer.

[0050] To facilitate understanding of the present embodiment, a MEMS acoustic transducer disclosed in an embodiment of the present invention is first introduced, and the MEMS acoustic transducer includes: a substrate, the upper surface of the substrate is covered with a dry film layer, a transducer diaphragm assembly is arranged above the dry film layer, and the transducer diaphragm assembly includes: a supporting layer and at least one piezoelectric composite layer; a middle area of ​​the substrate and a middle area of ​​the dry film layer form a cavity, and in the transducer diaphragm assembly, an area opposite to the cavity forms a diaphragm structure; wherein the shape of the dry film layer is obtained by graphical processing; in the inner side surface of the cavity, the inner side surface of the dry film corresponding to the dry film layer is perpendicular to the diaphragm structure; the size of the middle area of ​​the dry film layer is a preset target size.

[0051] The material of the substrate can be silicon, glass, sapphire, etc., which can be selected according to actual needs; the dry film layer is usually a photosensitive cover film, such as Flexfiner SA or PVI-3 (the full name of PVI in English is Polyvinyl Isobutyl Ether), and benzocyclobutene BCB (Benzocyclobutene) material can also be used. BCB-based resin is an interlayer dielectric material with excellent comprehensive performance. BCB has a strong bonding effect, high flatness, good thermal stability, and high inertness to various chemicals in III-V material process (referring to the process technology of manufacturing semiconductor devices using III-group and V-group elements), and is very suitable for wafer bonding of III-V materials and silicon materials.

[0052] The relative positions of the support layer and at least one piezoelectric composite layer in the above-mentioned transducer diaphragm assembly can be set according to actual needs, for example, each piezoelectric composite layer can be set on the upper surface of the support layer, or, the support layer can be set on the upper surface of each piezoelectric composite layer, etc.; wherein, the support layer usually adopts a low-density flexible material, for example, the material of the support layer can be selected but not limited to one of the following materials or a combination thereof: silicon nitride, aluminum nitride, TEOS (Tetraethoxysilane), silicon dioxide, silicon nitride, PI (Polyimide), silicon carbide and other organic film materials with strong bonding effect, high flatness and good thermal stability, Flexfiner SA, PVI-3, polyimide, polyparaxylene, BCB-based resin, polyurethane, etc., and the thickness is usually between 0.5μm and 30μm; the material of the dry film layer and the support layer can be the same or different, and can be selected according to actual needs. The size, shape, etc. of the above-mentioned cavity can be set according to actual needs, and the corresponding area is the diaphragm structure when vertically mapped from the cavity to the direction of the transducer diaphragm assembly; the inner side surface of the above-mentioned cavity can be understood as the side surface forming the cavity; since the middle area of ​​the substrate and the middle area of ​​the dry film layer form the cavity, the inner side surface of the dry film can be understood as the area corresponding to the side surface of the dry film layer in the side surface forming the cavity; the shape of the dry film layer can be obtained through graphical processing, so it can be ensured that the inner side surface of the dry film layer is perpendicular to the diaphragm structure; the above-mentioned target size can be understood as the size of the cavity area pre-set to ensure the sound effect of the MEMS acoustic transducer.

[0053] For easier understanding, see Figure 2The schematic diagram of a cross-sectional view of a MEMS acoustic transducer shown in the figure can meet the requirements of device miniaturization. The upper surface of the substrate of the MEMS acoustic transducer is covered with a dry film layer, the upper surface of the dry film layer is covered with a support layer, the upper surface of the support layer has a piezoelectric composite layer, and the upper surface of the entire MEMS acoustic transducer is also deposited with a passivation layer. Each piezoelectric composite layer includes: a bottom electrode layer, a piezoelectric layer, and a top electrode layer structure; Figure 2 In the present invention, the left and right sides of the transducer diaphragm assembly can be anchoring edges, and the upper and lower sides can be free movable edges. The anchoring edges are completely or partially fixed on the device substrate, and the dry film layer is made into a barrier layer through the wafer bonding process and vacuum lamination.

[0054] like Figure 3 A schematic diagram of a cross-sectional view of another MEMS acoustic transducer is shown, and Figure 2 Compared with the structure of the MEMS acoustic transducer in Figure 3 The number of piezoelectric composite layers of the MEMS acoustic transducer has increased and is distributed in the middle area of ​​the diaphragm. The size of the cavity has also increased. The number, position, shape, and size of the piezoelectric composite layers can be set according to actual needs, making the application more flexible.

[0055] like Figure 4 A schematic diagram of a cross-sectional view of another MEMS acoustic transducer is shown, and Figure 3 Compared with the structure of the MEMS acoustic transducer in Figure 4 In the MEMS acoustic transducer, a piezoelectric composite layer with a passivation layer deposited on the upper surface of the dry film layer is formed, and the passivation layer is combined with the dry film layer, and a support layer is covered on the upper surface of the piezoelectric composite layer, and the support layer material can be a dry film. That is, the relative position of the support layer and each piezoelectric composite layer in the transducer diaphragm assembly can be set according to actual needs, further improving the application flexibility.

[0056] The above-mentioned MEMS acoustic transducer forms a cavity by the middle area of ​​the substrate and the middle area of ​​the dry film layer. Since the inner side surface of the dry film corresponding to the dry film layer in the inner side surface of the cavity is perpendicular to the diaphragm structure, and the size of the middle area of ​​the dry film layer is a preset target size, it is possible to avoid over-etching or incomplete etching of the top of the cavity, thereby improving the accuracy and consistency of cavity etching, thereby improving the performance of the MEMS acoustic transducer device and the on-chip device yield of the entire wafer.

[0057] Further, in the inner side of the cavity, the inner side of the dry film layer corresponding to the inner side of the substrate corresponding to the substrate is aligned or not aligned. The inner side of the substrate can be understood as the area corresponding to the side of the substrate in the side forming the cavity; in one implementation, the inner side of the dry film layer can be aligned with the inner side of the substrate, for example, referring to Figure 2 From the perspective of FIG. 1 , the distance between the left and right inner sides of the substrate can be set to be the same as the distance between the left and right inner sides of the dry film layer, that is, in the cross-sectional view, the shape of the entire cavity is a rectangle; in another implementation, the inner side of the dry film layer and the inner side of the substrate may not be aligned, for example, Figure 2 For example, the distance between the left and right inner sides of the substrate is greater than the distance between the left and right inner sides of the dry film layer; in addition, since the shape of the dry film layer can be obtained in advance through graphic processing, and the inner side of the dry film is guaranteed to be perpendicular to the diaphragm structure, the size of the middle area of ​​the dry film layer is a preset target size. Therefore, in the process of etching the cavity on the substrate, even if the inner side of the substrate is roughly etched or the verticality is poor, it will not have a significant impact on the performance of the MEMS acoustic transducer.

[0058] Furthermore, the support layer is arranged on the upper surface of the dry film layer; each piezoelectric composite layer is arranged on the upper surface of the support layer; a passivation layer is deposited on the upper surface of the support layer except for each piezoelectric composite layer, and on the upper surface and each side of each piezoelectric composite layer.

[0059] Specifically, Figure 2 and Figure 3 As shown, the support layer is below the piezoelectric composite layer, and one or more piezoelectric composite layers located on its upper surface are supported by the support layer.

[0060] Furthermore, a passivation layer is deposited on the lower surface of each piezoelectric composite layer, and each piezoelectric composite layer deposited with the passivation layer is arranged on the upper surface of the dry film layer, and a support layer is covered above each piezoelectric composite layer.

[0061] Specifically, Figure 4 As shown, the piezoelectric composite layer is below the support layer, and the support layer supports one or more piezoelectric composite layers located on its lower surface. In actual implementation, low-density flexible materials are usually used as support layers, which reduces the mass of the diaphragm structure, is conducive to improving the sound pressure level curve, and improves the mid-frequency performance. The system damping can be increased to reduce its resonance Q value, thereby making the sound pressure level curve smoother and reducing the total harmonic interference THD (Total Harmonic Distortion).

[0062] Furthermore, a plurality of gaps are provided on the piezoelectric composite layer and the support layer.

[0063] As shown in Figure 5(a), there is a schematic diagram of the structure of a piezoelectric composite layer, as shown in Figure 5(b), and there is a schematic diagram of the structure of a piezoelectric composite layer as shown in Figure 5(c), wherein the piezoelectric composite layer in Figure 5(a) is a single piezoelectric layer, and the piezoelectric composite layers are, from bottom to top, a bottom electrode layer, a piezoelectric layer, and a top electrode layer; the piezoelectric composite layer in Figure 5(b) is a double piezoelectric layer, and the piezoelectric composite layers are, from bottom to top, a bottom electrode layer, a piezoelectric layer, an electrode layer, a piezoelectric layer, and a top electrode layer; the piezoelectric composite layer in Figure 5(c) is a multi-piezoelectric layer structure, and the multi-piezoelectric layer structure can be inferred accordingly, which will not be repeated here, and piezoelectric composite layers with different numbers of layers can be selected according to actual needs.

[0064] In actual implementation, multiple gaps can be set on the piezoelectric composite layer and the support layer, and the position, number, and length of the gaps can be set according to actual needs; a front schematic diagram of a MEMS acoustic transducer as shown in FIG6(a) is similar to FIG6(a). Figure 2 6(a) represents the upper surface of the silicon substrate wafer, and the device is surrounded by fixed constraints. Regions 10a, 10b, 10c, 10d, 10e, and 10f in FIG6(a) represent the edges of the etching size of the back cavity of the MEMS acoustic transducer, respectively. The six line segments form a regular hexagonal structure, which is also the boundary line of the device's vibrating film. The deep silicon etching process etches away the middle layer of silicon in the back cavity, thereby forming a hollow hexagonal structure cavity, which is released into the vibrating film structure of the MEMS acoustic transducer. 40a represents the piezoelectric composite layer of the MEMS acoustic transducer, 20a, 20b, 20c, 20d, 20e, and 20f are linear grooves, which extend beyond the edge area of ​​the cavity, and the other end does not exceed the middle area of ​​the piezoelectric composite layer 40a. The linear grooves divide the piezoelectric composite layer 40a near the edge of the cavity. It can be seen that it is divided into six areas, but the piezoelectric composite layer 40a is still a whole, and the upper and lower electrical connections are the same; at the same time, through the etching process, the linear grooves will also etch the supporting layer 50 into a groove structure, which can reduce the residual stress of the diaphragm and improve the performance of the device.

[0065] FIG6(b) shows another front view of a MEMS acoustic transducer. Unlike FIG6(a), the regions 10a, 10b, 10c, 10d, 10e, and 10f in FIG6(b) represent the edges of the back cavity etching size of the MEMS acoustic transducer, and 20a, 20b, 20c, 20d, 20e, and 20f are linear grooves. The linear grooves do not extend beyond the edge of the cavity, but the other end exceeds the middle area of ​​the piezoelectric composite layer 40a. In addition, there is a piezoelectric composite layer 40b in the center of the diaphragm, which can be electrically connected in series with the piezoelectric composite layer 40a at the edge to form an internal and external double electrode structure. At the same time, through the etching process, the linear grooves will also etch the support layer 50 into a groove structure.

[0066] The piezoelectric composite layer 40b in the middle of Figure 6(b) is a hexagonal structure, but its shape can be other irregular graphic structures such as rectangle, circle, polygon, etc. At the same time, the straight grooves 20a, 20b, 20c, 20d, 20e, 20f can also be divided into two or more line segments, and its shape can be a variety of different graphic structures, such as S curve, semi-ellipse, arc, etc.; the position of the etched area on the diaphragm and the size of the etched area can have many variations, not limited to those shown in the figure.

[0067] Furthermore, in the diaphragm structure, a preset position of the support layer close to the inner boundary of the piezoelectric composite layer is etched into a spring structure.

[0068] The above-mentioned preset positions can be set according to actual needs. For example, as shown in FIG. 6(c), another front schematic diagram of a MEMS acoustic transducer is different from FIG. 6(a) in that the region in FIG. 6(c) has spring structures of 30a, 30b, 30c, 30d, 30e, and 30f, that is, this region is etched at intervals, which is conducive to increasing the displacement of the diaphragm structure. The structure is formed near the six boundaries inside the piezoelectric composite layer 40a by etching. The spring structure can be in the shape of an S, a semi-ellipse, a tree branch, etc. When the MEMS acoustic transducer is driven by piezoelectric, the diaphragm vibrates up and down like a piston. The linear groove etching regions of 20a, 20b, 20c, 20d, 20e, and 20f can decouple the device structure and release the process internal stress of each membrane layer, thereby reducing the risk of deformation or even rupture of the diaphragm caused by stress, and at the same time, the device can obtain a larger driving displacement and sound pressure level output.

[0069] The MEMS acoustic transducer can also adopt other structures, such as the front schematic diagram of another MEMS acoustic transducer as shown in Figure 6(d); the front schematic diagram of another MEMS acoustic transducer as shown in Figure 6(e); the front schematic diagram of another MEMS acoustic transducer as shown in Figure 6(f); and the front schematic diagram of another MEMS acoustic transducer as shown in Figure 6(g). A 50 dry film structure is added to the surface of these four structures. The dry film structure has a long rib shape and can also be in various other shapes. The rigid-flexible diaphragm form can reduce the Q value of the MEMS device, thereby reducing the THD of the device. Different structural forms can be set according to actual needs, which will not be repeated here.

[0070] In order to generate sound, generally 1) the larger the effective radiation area, the higher the sound pressure generated. 2) the greater the displacement of the diaphragm radiation area, the higher the sound pressure generated. When a single MEMS acoustic transducer has a limited output sound pressure level SPL (Sound Pressure Level) under excitation, multiple MEMS acoustic transducers can be distributed in an array structure to increase the sound area of ​​the sound generator, thereby improving the sound pressure level output of the device, such as the array schematic diagram of a MEMS acoustic transducer shown in Figure 7(a), the array schematic diagram of another MEMS acoustic transducer shown in Figure 7(b), and the array schematic diagram of another MEMS acoustic transducer shown in Figure 7(c).

[0071] The array structure S01 of the MEMS acoustic transducer in FIG7(a) adopts the MEMS acoustic transducer of the same structure, and the size parameters, structural shape and performance of each MEMS acoustic transducer in the array are consistent. The array structure layout is a linear structure, with a horizontal axis and a vertical axis arranged linearly. Two MEMS acoustic transducers in FIG6(a) can be arranged in the horizontal axis X direction, or three MEMS acoustic transducers in FIG6(a) and other units can be arranged; one or two MEMS acoustic transducers in FIG6(a) can be arranged in the vertical axis Y direction, or four MEMS acoustic transducers in FIG6(a) and other units can be arranged; at the same time, the MEMS acoustic transducers in FIG6(a) can be arranged linearly in the horizontal axis and the vertical axis, and the MEMS acoustic transducers in FIG6(a) can be arranged in an array structure of 1×1, 2×2, 3×3, 2×3, 3×2, 4×4, etc.

[0072] In the array structure S02 of the MEMS acoustic transducer in Figure 7(b), the MEMS acoustic transducer in device Figure 6(b) may be used, or other devices, such as the MEMS acoustic transducer in Figure 6(c), etc., to form an array structure of multiple identical and / or different devices. Compared with the array structure S01, the array structure S02 of the MEMS acoustic transducer has the same size parameters of the unit devices in the array, but their structural shapes and performances are different. The array structure layout has a linear arrangement of the horizontal axis and the vertical axis. In the Y direction of the vertical axis, a single or multiple MEMS acoustic transducers in FIG. 6(b) are arranged, and the devices in the Y direction of the vertical axis can be the same or different; in the X direction of the horizontal axis, a single or multiple MEMS acoustic transducers in FIG. 6(a) are arranged, and the devices in the X direction of the horizontal axis can be the same or different; the MEMS acoustic transducers in FIG. 6(a), FIG. 6(b), and FIG. 6(c) can be arranged linearly in both the horizontal and vertical axes, and the MEMS acoustic transducers in FIG. 6(a), FIG. 6(b), and FIG. 6(c) can be arranged in various array structures such as 2×2, 3×3, 4×4, 2×3, and 3×2. It should be noted that the devices of the array S02 can be devices of other structural forms.

[0073] In the array structure S03 of the MEMS acoustic transducer in FIG7(c), compared with the array structure S01, the size parameters, structural shape and performance of each MEMS acoustic transducer in the array can be different, and the array structure layout also has a horizontal axis and a vertical axis linear arrangement. In the horizontal axis X direction, there is one MEMS acoustic transducer in FIG6(b) and two MEMS acoustic transducers in FIG6(a), and the two MEMS acoustic transducers in FIG6(a) are arranged in the vertical axis Y direction, and the left and right arrangements are 1×2, 1×3, etc., or 2×4. , 2×6, etc., for example, the up-down arrangement can be changed to down-up, left-right, right-left, etc. For example, in the array structure S04 of the MEMS acoustic transducer in FIG7(d), a MEMS acoustic transducer in FIG6(a) is used in the longitudinal direction Y, and two MEMS acoustic transducers in FIG6(b) or the MEMS acoustic transducers in FIG6(c) are arranged in the horizontal direction X above the MEMS acoustic transducer, or in the arrangement form of up-middle-down, left-middle-right, etc. It should be noted that the devices of the array S03 can be other devices and are not limited here.

[0074] To further verify this solution, the three MEMS acoustic transducers in Figure 6(a), Figure 6(b) and Figure 6(c) are simulated and verified respectively. The sizes of these three MEMS acoustic transducers are: 3mm×3mm, the piezoelectric layer is a single-layer thin film structure, Si substrate, the supporting layer is a dry film material Flexfiner SA, and the excitation piezoelectric DC is: 10Vp.

[0075] A schematic diagram of a simulation frequency as shown in FIG8(a) is a characteristic frequency obtained after simulating the MEMS acoustic transducer in FIG6(a). A schematic diagram of another simulation frequency as shown in FIG8(b) is a characteristic frequency obtained after simulating the MEMS acoustic transducer in FIG6(b). A schematic diagram of another simulation frequency as shown in FIG8(c) is a characteristic frequency obtained after simulating the MEMS acoustic transducer in FIG6(c).

[0076] A schematic diagram of a simulated vibration displacement as shown in FIG9(a) is a simulated displacement obtained after simulating the MEMS acoustic transducer in FIG6(a). Another schematic diagram of a simulated vibration displacement as shown in FIG9(b) is a simulated displacement obtained after simulating the MEMS acoustic transducer in FIG6(b). Another schematic diagram of a simulated vibration displacement as shown in FIG9(c) is a simulated displacement obtained after simulating the MEMS acoustic transducer in FIG6(c).

[0077] The three MEMS acoustic transducers in Figures 6(a), 6(b) and 6(c) are simulated respectively to obtain the resonant frequency of the MEMS acoustic transducers of the corresponding structures and the maximum vibration displacement of the diaphragm. The simulation results are shown in Figures 8(a), 8(b), 8(c), 9(a), 9(b) and 9(c). It can be seen from the figures that the resonant frequencies of the diaphragms of the three MEMS acoustic transducers are 12.3kHz, 10.6kHz and 13.3kHz respectively, and the maximum displacements are 24.6um, 29.2um and 18.3um respectively. The displacement of the device diaphragm is integrated, and the volume of air pushed by each device is 0.035mm^ 3 , 0.021mm^ 3 , 0.015mm^ 3 Comparing the three MEMS acoustic transducers, the smaller the first-order resonance frequency of the MEMS acoustic transducer, the smaller the stiffness of the diaphragm structure of the MEMS acoustic transducer. Under the action of electric drive, the larger the maximum displacement of the diaphragm structure, the more air the MEMS acoustic transducer pushes, that is, the higher the emission sound pressure level of the MEMS acoustic transducer.

[0078] The above-mentioned MEMS acoustic transducer uses a flexible dry film material as a barrier layer and a low-density flexible material as a support layer, which has the following beneficial effects:

[0079] 1) Through wafer bonding and vacuum lamination, the dry film layer is used as a barrier layer, so that the lower surface silicon layer of the substrate is etched by DRIE to obtain a cavity structure perpendicular to the diaphragm, thereby improving the accuracy of cavity etching. The good consistency of the cavity edge is conducive to maintaining the consistency of the diaphragm functional layer, and there is no over-etching or incomplete etching, so that the vibration frequency and sensitivity performance of the device will not be affected, and the device structure will not be damaged to cause failure.

[0080] 2) In addition to improving the performance of a single MEMS acoustic transducer, the cavity sizes in the edge and middle areas of the entire wafer are relatively consistent, which improves the consistency and uniformity of the cavity etching structure of the entire wafer. The resulting MEMS acoustic transducer device has good performance consistency, greatly improving the yield of the entire on-chip device.

[0081] 3) The use of flexible dry film materials can reduce the mass of diaphragm vibration, which is beneficial to improving the sound pressure level curve of the MEMS acoustic transducer and improving the mid-frequency performance. At the same time, it can increase system damping to reduce its resonance Q value and reduce total harmonic interference THD.

[0082] 4) Multiple MEMS acoustic transducers are arranged in an array to increase the amount of air pushed by increasing the generating area, thereby improving the emission sound pressure level of the device.

[0083] The embodiment of the present invention further provides a method for manufacturing a MEMS acoustic transducer, the method comprising the following steps:

[0084] Step 1, covering the upper surface of the preset first substrate with a dry film layer;

[0085] The first substrate can be represented by a common silicon wafer substrate A. In actual implementation, the first substrate can be subjected to conventional surface treatment, and then a photosensitive cover film Flexfiner SA or PVI-3 can be vacuum-laminated on the upper surface of the first substrate. Other commonly used wafer bonding BCB materials can also be used to obtain the following: Fig.10 The schematic diagram of a first substrate covered with a dry film layer is shown in the figure, where substrate A is the first substrate; the flexible dry film material used in the dry film layer not only needs to be compatible with the MEMS process, can be patterned, work for a long time, and resist aging, but also has good mechanical properties and temperature stability. The flexible dry film material requires a certain stretch rate, and the CTE (Coefficient of thermal expansion) difference between the material and the substrate minimizes the wafer bending. The flexible dry film material can not only cover the groove gap, but also can be used as an insulating layer material to cover the metal connection, playing the role of electrical insulation and waterproofing.

[0086] Step 2, performing a patterning process on the dry film layer to obtain a first device;

[0087] like Fig.11 The schematic diagram of a first device shown in FIG. Fig.10 The dry film layer in the device is imaged, and then goes through processes such as light exposure, PEB / pre-bake (Post Exposure Bake), development, and post-curing to obtain a first device.

[0088] Step 3, thermally growing an oxide layer on the upper surface and the lower surface of the preset second substrate, respectively, to obtain a second substrate with an oxide layer;

[0089] The second substrate can be represented by a common silicon wafer substrate. Fig.12 A schematic diagram of a second substrate with an oxide layer is shown, in which the B substrate is the second substrate. Silicon dioxide layers can be grown on both sides of the second substrate by thermal oxidation in a thermal oxidation furnace, 1KA; the thickness of the SiO2 layer is between 0.01 and 5 um, and can be made of insulating materials such as silicon nitride and aluminum oxide.

[0090] Step four, depositing a transducer diaphragm assembly on the oxide layer on the upper surface of the second substrate with the oxide layer to obtain a second device, so as to obtain a MEMS acoustic transducer based on the first device and the second device; wherein the transducer diaphragm assembly includes: a supporting layer and at least one piezoelectric composite layer; a cavity is formed in the middle area of ​​the substrate of the MEMS acoustic transducer and the middle area of ​​the dry film layer, and a diaphragm structure is formed in the area opposite to the cavity in the transducer diaphragm assembly; wherein the shape of the dry film layer is obtained by graphical processing; in the inner side surface of the cavity, the inner side surface of the dry film corresponding to the dry film layer is perpendicular to the diaphragm structure; the size of the middle area of ​​the dry film layer is a preset target size.

[0091] In actual implementation, a transducer diaphragm assembly can be deposited on the oxide layer on the upper surface of the second substrate with the oxide layer to obtain a second device, and a MEMS acoustic transducer can be obtained by bonding the first device and the second device.

[0092] In the manufacturing method of the above-mentioned MEMS acoustic transducer, a cavity is formed by the middle area of ​​the substrate and the middle area of ​​the dry film layer. Since the inner side surface of the dry film corresponding to the dry film layer in the inner side surface of the cavity is perpendicular to the diaphragm structure, and the size of the middle area of ​​the dry film layer is a preset target size, it is possible to avoid over-etching or incomplete etching of the top of the cavity, thereby improving the accuracy and consistency of cavity etching, thereby improving the performance of the MEMS acoustic transducer device and the on-chip device yield of the entire wafer.

[0093] The embodiment of the present invention further provides another method for manufacturing a MEMS acoustic transducer. The method is implemented on the basis of the method of the above embodiment, and the method comprises the following steps:

[0094] Step 11, covering the upper surface of the preset first substrate with a dry film layer;

[0095] Step 12, performing a patterning process on the dry film layer to obtain a first device;

[0096] Step 13, thermally grow an oxide layer on the upper surface and the lower surface of the preset second substrate respectively to obtain a second substrate with an oxide layer;

[0097] Step 14, on the oxide layer on the upper surface of the second substrate with the oxide layer, depositing a bottom electrode layer, a middle layer and a top electrode layer in sequence from bottom to top to obtain a third device;

[0098] In actual implementation, the seed layer, ZrO2, Y2O3 and bottom electrode layer can be grown by RF (Radio Frequency) magnetron sputtering; the seed layer is conducive to the high-quality growth of the piezoelectric layer, the piezoelectric layer is grown by RF magnetron sputtering and the top electrode layer is deposited by DC magnetron sputtering, and the following can be obtained: Fig.13A schematic diagram of a third device is shown, in which the piezoelectric layer is a single crystal PZT (lead zirconate titanate) film with a thickness of 2 um, and the top electrode layer is Pt with a thickness of 0.1 um.

[0099] The material of the electrode layer may be selected from but not limited to one of the following materials or a combination thereof: single crystal or polycrystalline metal films such as aluminum, copper, gold, platinum, molybdenum, chromium, titanium, etc., metal conductive films such as lanthanum nickel oxide LaNiO3 (LNO), SrRuO3 (SRO), etc., or composite metal layers, such as: gold / chromium composite layers. Preferably, the thickness of the Pt electrode is between 0.01 μm and 5 μm.

[0100] The material of the piezoelectric layer may be selected from but not limited to one or a combination of the following materials: polycrystalline or single crystal piezoelectric films such as ZnO, AlN, PZT, PVDF, or doped piezoelectric films, such as AlN doped piezoelectric films; the thickness of the piezoelectric layer is between 0.1 μm and 15 μm.

[0101] Step 15, depositing a support layer on the upper surface of the third device to obtain a fourth device;

[0102] like Fig.14 As shown in the schematic diagram of a fourth device, a support layer can be formed on the upper surface of the third device by using a MEMS semiconductor process such as deposition or vacuum lamination.

[0103] Step 16, flipping the fourth device, and bonding the flipped fourth device to the upper surface of the first device, so that the dry film layer of the first device is combined with the support layer of the fourth device, to obtain a fifth device;

[0104] like Fig.15 The schematic diagram of a fifth device shown is that the structure of the fourth device can be flipped over, and the first device and the flipped fourth device can be permanently bonded to obtain the fifth device.

[0105] Step 17, removing the second substrate with the oxide layer in the fifth device to obtain a sixth device;

[0106] like Fig.16 The schematic diagram of a sixth device shown is a diagram of a sixth device, and the second substrate in the fifth device and the oxide layer covering the second substrate are removed to obtain the sixth device.

[0107] Step 18, patterning the bottom electrode layer, the middle layer and the top electrode layer in the sixth device to form at least one piezoelectric composite layer, thereby obtaining a patterned seventh device;

[0108] The top electrode layer, piezoelectric layer, bottom electrode layer, etc. in the piezoelectric composite layer are etched in sequence, and a passivation layer is deposited to isolate the electrical connections of each electrode layer to play an insulating and protective role. The passivation layer is patterned to lead out the bottom electrode layer and the top electrode layer for electrical connections between different piezoelectric composite layers and connecting pads PAD. The passivation layer material can be silicon dioxide with a thickness of 0.5um. The lift-off process is used to make metal PADs and traces. The material can be selected from but not limited to one of the following materials or a combination thereof: gold, copper, aluminum, and other metal materials, or conductive alloy materials, etc.

[0109] The PZT piezoelectric layer is etched at an angle, which is beneficial to the step coverage of the passivation layer. The etching angle of the PZT piezoelectric layer is 30°-60°, and the over-etching amount of the bottom electrode layer is <10%. The side wall roughness of the PZT piezoelectric layer is as small as possible. The goal is that after the passivation layer deposition is completed, there is no delamination between the sliced ​​PZT and the passivation layer.

[0110] Step 19, depositing a passivation layer on the upper surface of the seventh device to isolate the electrical connection of each top electrode layer, and patterning the passivation layer to form a pad area to lead out the bottom electrode layer and / or the top electrode layer of each piezoelectric composite unit, thereby obtaining an eighth device;

[0111] like Fig.17 The schematic diagram of an eighth device is shown; the passivation layer needs to have good step coverage and can be closely attached to each film layer. The material can be selected from but not limited to one or a combination of the following materials: TEOS, silicon dioxide, aluminum nitride, PI, aluminum oxide and other oxide insulating materials, or non-conductive organic compounds, etc.

[0112] Step 20, depositing a metal layer on each pad region in the eighth device to form a pad, and bonding a metal wire to obtain a ninth device;

[0113] The metal wire deposition and patterning may be performed using a lift-off process, and the material may be selected from but not limited to one of the following materials or a combination thereof: gold, copper, aluminum, and other metal materials, or conductive alloy materials, and the like.

[0114] Step twenty-one, thinning and cavity etching the bottom surface of the first substrate of the ninth device to obtain a MEMS acoustic transducer; wherein the transducer diaphragm assembly includes: a supporting layer and at least one piezoelectric composite layer; a cavity is formed in the middle area of ​​the substrate of the MEMS acoustic transducer and the middle area of ​​the dry film layer, and in the transducer diaphragm assembly, a diaphragm structure is formed in the area opposite to the cavity; wherein the shape of the dry film layer is obtained by graphical processing; in the inner side surface of the cavity, the inner side surface of the dry film corresponding to the dry film layer is perpendicular to the diaphragm structure; the size of the middle area of ​​the dry film layer is a preset target size.

[0115] In actual implementation, wafer thinning to 300um by CMP is conducive to the thinning of the device thickness, and the double-sided exposure technology DRIE is used to etch the back cavity silicon layer, thereby releasing the vibration film of the MEMS acoustic transducer. Figure 2 MEMS acoustic transducer in.

[0116] In the manufacturing method of the above-mentioned MEMS acoustic transducer, a cavity is formed by the middle area of ​​the substrate and the middle area of ​​the dry film layer. Since the inner side surface of the dry film corresponding to the dry film layer in the inner side surface of the cavity is perpendicular to the diaphragm structure, and the size of the middle area of ​​the dry film layer is a preset target size, it is possible to avoid over-etching or incomplete etching of the top of the cavity, thereby improving the accuracy and consistency of cavity etching, thereby improving the performance of the MEMS acoustic transducer device and the on-chip device yield of the entire wafer.

[0117] The embodiment of the present invention further provides a method for manufacturing a MEMS acoustic transducer. The method is implemented on the basis of the method of the above embodiment, and the method comprises the following steps:

[0118] Step 30, covering the upper surface of the preset first substrate with a dry film layer;

[0119] Step 31, performing a patterning process on the dry film layer to obtain a first device;

[0120] Step 32, thermally grow an oxide layer on the upper surface and the lower surface of the preset second substrate, respectively, to obtain a second substrate with an oxide layer;

[0121] Step 33, depositing a support layer on the oxide layer on the upper surface of the second substrate with the oxide layer to obtain a tenth device;

[0122] In actual implementation, the support layer may be formed on the upper surface of the second substrate with the oxide layer by using a MEMS semiconductor process such as deposition or vacuum lamination.

[0123] Step 34, depositing a bottom electrode layer, a middle layer and a top electrode layer in sequence from bottom to top on the support layer of the tenth device to obtain an eleventh device;

[0124] In actual implementation, the seed layer, ZrO2, Y2O3 and the bottom electrode layer, piezoelectric layer and top electrode layer can be grown by RF magnetron sputtering. For details, please refer to the relevant description in the above step fourteen, which will not be repeated here.

[0125] Step 35, patterning the bottom electrode layer, the middle layer and the top electrode layer in the eleventh device to form at least one piezoelectric composite layer, thereby obtaining a patterned twelfth device;

[0126] For details, please refer to the relevant description in the above step 18, which will not be repeated here.

[0127] Step thirty-six, depositing a passivation layer on the upper surface of the twelfth device to isolate the electrical connection of each top electrode layer, and patterning the passivation layer to form a pad area to lead out the bottom electrode layer and / or the top electrode layer of each piezoelectric composite unit, thereby obtaining a thirteenth device;

[0128] For details, please refer to the relevant description in the above step 19, which will not be repeated here.

[0129] Step 37, depositing a metal layer on each pad region in the thirteenth device to form a pad, and bonding a metal wire to obtain a fourteenth device;

[0130] For details, please refer to the relevant description in the above step 20, which will not be repeated here.

[0131] Step 38, flipping the fourteenth device, and bonding the flipped fourteenth device to the upper surface of the first device, so that the dry film layer of the first device is combined with the passivation layer of the fourteenth device, to obtain the fifteenth device;

[0132] The structure of the fourteenth device can be flipped over, and the first device can be permanently bonded to the flipped fourteenth device to obtain the fifteenth device.

[0133] Step thirty-nine, thinning and cavity etching the bottom surface of the first substrate of the fifteenth device to obtain a MEMS acoustic transducer; wherein the transducer diaphragm assembly includes: a supporting layer and at least one piezoelectric composite layer; the middle area of ​​the substrate of the MEMS acoustic transducer and the middle area of ​​the dry film layer form a cavity, and in the transducer diaphragm assembly, the area opposite to the cavity forms a diaphragm structure; wherein the shape of the dry film layer is obtained by graphical processing; in the inner side surface of the cavity, the inner side surface of the dry film corresponding to the dry film layer is perpendicular to the diaphragm structure; the size of the middle area of ​​the dry film layer is a preset target size.

[0134] In the manufacturing method of the above-mentioned MEMS acoustic transducer, a cavity is formed by the middle area of ​​the substrate and the middle area of ​​the dry film layer. Since the inner side surface of the dry film corresponding to the dry film layer in the inner side surface of the cavity is perpendicular to the diaphragm structure, and the size of the middle area of ​​the dry film layer is a preset target size, it is possible to avoid over-etching or incomplete etching of the top of the cavity, thereby improving the accuracy and consistency of cavity etching, thereby improving the performance of the MEMS acoustic transducer device and the on-chip device yield of the entire wafer.

[0135] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A MEMS acoustic transducer, characterized in that: It comprises: a substrate, the upper surface of which is covered with a dry film layer, a transducer diaphragm assembly is arranged above the dry film layer, and the transducer diaphragm assembly comprises: a supporting layer and at least one piezoelectric composite layer; a middle area of ​​the substrate and a middle area of ​​the dry film layer form a cavity, and in the transducer diaphragm assembly, an area opposite to the cavity forms a diaphragm structure; wherein the shape of the dry film layer is obtained by graphical processing; in the inner side surface of the cavity, the inner side surface of the dry film corresponding to the dry film layer is perpendicular to the diaphragm structure; and the size of the middle area of ​​the dry film layer is a preset target size.

2. The acoustic transducer according to claim 1, characterized in that: In the inner side surface of the cavity, the inner side surface of the dry film corresponding to the dry film layer is aligned with or not aligned with the inner side surface of the substrate corresponding to the substrate.

3. The acoustic transducer according to claim 1, characterized in that: The support layer is arranged on the upper surface of the dry film layer; each piezoelectric composite layer is arranged on the upper surface of the support layer; a passivation layer is deposited on the area on the upper surface of the support layer except each piezoelectric composite layer, and on the upper surface and each side surface of each piezoelectric composite layer.

4. The acoustic transducer according to claim 1, characterized in that: A passivation layer is deposited on the lower surface of each piezoelectric composite layer, and each piezoelectric composite layer deposited with the passivation layer is arranged on the upper surface of the dry film layer. A support layer is covered above each piezoelectric composite layer.

5. The acoustic transducer according to claim 1, characterized in that: A plurality of gaps are arranged on the piezoelectric composite layer and the supporting layer.

6. The acoustic transducer according to claim 1, characterized in that: In the diaphragm structure, a preset position of the support layer close to the inner boundary of the piezoelectric composite layer is etched into a spring structure.

7. The acoustic transducer according to claim 1, characterized in that: The dry film layer and the support layer are made of the same material.

8. A method for manufacturing a MEMS acoustic transducer, characterized in that: The method comprises: Covering the upper surface of the preset first substrate with a dry film layer; Performing a patterning process on the dry film layer to obtain a first device; Thermally grow oxide layers on the upper surface and the lower surface of the preset second substrate respectively to obtain a second substrate with an oxide layer; A transducer diaphragm assembly is deposited on the oxide layer on the upper surface of the second substrate with the oxide layer to obtain a second device, so as to obtain a MEMS acoustic transducer based on the first device and the second device; wherein the transducer diaphragm assembly includes: a supporting layer and at least one piezoelectric composite layer; a cavity is formed between the middle area of ​​the substrate of the MEMS acoustic transducer and the middle area of ​​the dry film layer, and a diaphragm structure is formed in the area opposite to the cavity in the transducer diaphragm assembly; wherein the shape of the dry film layer is obtained by graphical processing; in the inner side surface of the cavity, the inner side surface of the dry film corresponding to the dry film layer is perpendicular to the diaphragm structure; and the size of the middle area of ​​the dry film layer is a preset target size.

9. The method according to claim 8, characterized in that The steps of depositing a transducer diaphragm assembly on the oxide layer on the upper surface of the second substrate with the oxide layer to obtain a second device, and obtaining a MEMS acoustic transducer based on the first device and the second device include: On the oxide layer on the upper surface of the second substrate with the oxide layer, depositing a bottom electrode layer, an intermediate layer and a top electrode layer in sequence from bottom to top to obtain a third device; Depositing a supporting layer on the upper surface of the third device to obtain a fourth device; Turning over the fourth device, and bonding the turned over fourth device to the upper surface of the first device so that the dry film layer of the first device is combined with the support layer of the fourth device, thereby obtaining a fifth device; removing the second substrate with the oxide layer in the fifth device to obtain a sixth device; Performing patterning on the bottom electrode layer, the middle layer and the top electrode layer in the sixth device to form at least one piezoelectric composite layer, thereby obtaining a patterned seventh device; Depositing a passivation layer on the upper surface of the seventh device to isolate the electrical connection of each top electrode layer, and patterning the passivation layer to form a pad area to lead out the bottom electrode layer and / or the top electrode layer of each piezoelectric composite unit, thereby obtaining an eighth device; Depositing a metal layer on each pad region in the eighth device to form a pad, and bonding a metal wire to obtain a ninth device; The bottom surface of the first substrate of the ninth device is subjected to thinning processing and cavity etching processing to obtain a MEMS acoustic transducer.

10. The method according to claim 8, characterized in that The steps of depositing a transducer diaphragm assembly on the oxide layer on the upper surface of the second substrate with the oxide layer to obtain a second device, and obtaining a MEMS acoustic transducer based on the first device and the second device include: Depositing a support layer on the oxide layer on the upper surface of the second substrate having the oxide layer to obtain a tenth device; Depositing a bottom electrode layer, a middle layer and a top electrode layer in sequence from bottom to top on the support layer of the tenth device to obtain an eleventh device; Performing patterning on the bottom electrode layer, the middle layer and the top electrode layer in the eleventh device to form at least one piezoelectric composite layer, thereby obtaining a patterned twelfth device; Depositing a passivation layer on the upper surface of the twelfth device to isolate the electrical connection of each top electrode layer, and patterning the passivation layer to form a pad area to lead out the bottom electrode layer and / or the top electrode layer of each piezoelectric composite unit, thereby obtaining a thirteenth device; Depositing a metal layer on each pad region in the thirteenth device to form a pad, and bonding a metal wire to obtain a fourteenth device; flipping the fourteenth device, and bonding the flipped fourteenth device to the upper surface of the first device so that the dry film layer of the first device is combined with the passivation layer of the fourteenth device, thereby obtaining a fifteenth device; The bottom surface of the first substrate of the fifteenth device is thinned and etched to form a cavity, so as to obtain a MEMS acoustic transducer.

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