Bulk acoustic wave filter manufacturing method and bulk acoustic wave filter

Abstract

The invention discloses a manufacturing method of a bulk acoustic wave filter and the bulk acoustic wave filter. The manufacturing method comprises the following steps: manufacturing a first substrate; a resonant structure is formed on the first substrate, the resonant structure comprises a working area and a non-working area surrounding the working area, and a concave-convex structure is formed between at least one surface of the piezoelectric layer of the resonant structure and the adjacent film layer in the non-working area. Therefore, the technical effects of guaranteeing the service life of the bulk acoustic wave filter and improving the reliability of the bulk acoustic wave filter are achieved.

Description

Technical Field

[0001] The present application relates to the technical field of filter manufacturing, and in particular to a method for manufacturing a bulk acoustic wave filter and a bulk acoustic wave filter. Background Art

[0002] In the field of wireless communication technology, SAW filters and BAW filters are two crucial components that play a key role in different application scenarios.

[0003] BAW filter, or bulk acoustic wave filter, is based on bulk acoustic wave technology. When an alternating electric field is applied to both ends of a piezoelectric material, the material will generate mechanical vibrations, which propagate inside the material in the form of bulk acoustic waves. By cleverly designing the structure and size of the bulk acoustic wave filter, bulk acoustic waves of a specific frequency can be propagated smoothly in the filter, while suppressing sound waves of other frequencies, thereby achieving a filtering function.

[0004] D-BAW filter, that is, double-sided graphic process bulk acoustic wave filter. The bulk acoustic wave filter structure is made by double-sided bonding. That is, in the production process, several steps of preparation process are first implemented on the front side of the wafer, and then the wafer is turned over through bonding to implement subsequent preparation processes. During packaging, the wafer is flipped over through bonding, and several steps of preparation process are implemented on the back side, thus realizing the double-sided process in this way.

[0005] BAW filters include multiple layers of thin films, and each layer of thin film is bonded to each other to form a BAW filter. However, due to the different material properties, thermal expansion coefficients, lattice constant mismatch, film thickness differences, defects and impurities between the piezoelectric layer and the adjacent thin film, there is a certain stress difference between the piezoelectric layer and the adjacent thin film of the BAW filter. And because there is a certain stress difference between the piezoelectric layer and the adjacent thin film, separation or wafer warping may occur between the piezoelectric layer and the adjacent thin film. This may cause damage to the BAW filter device structure and reduce the reliability of the BAW filter.

[0006] The publication number is CN114978095A, and the name is a temperature-compensated thin film bulk acoustic wave resonator, a manufacturing method thereof, and a filter. The resonator includes a first substrate and a piezoelectric stack structure, a first cavity is arranged on the top of the first substrate; the piezoelectric stack structure is located on the first substrate, and the piezoelectric stack structure includes a seed layer, a bottom electrode, an adhesion layer, a temperature compensation layer, a piezoelectric layer, a top electrode, and a protective layer from bottom to top; a second cavity is arranged around the edge of the temperature compensation layer.

[0007] The publication number is CN117060875A, and the name is a bulk acoustic wave filter and its manufacturing method and electronic device. The bulk acoustic wave filter includes: a device substrate; a semiconductor cap substrate, a cap metal layer is formed on the first surface of the semiconductor cap substrate, a bonding portion is formed on the cap metal layer, and the cap metal layer is connected to the device substrate through the bonding portion, wherein the semiconductor cap substrate is also formed with a plurality of holes penetrating the semiconductor cap substrate, and the cap metal layer also fills the plurality of holes.

[0008] With regard to the technical problem existing in the above-mentioned prior art that a certain stress difference exists between the piezoelectric layer of the BAW filter and the adjacent film, which may cause separation between the piezoelectric layer and the adjacent film or wafer warping, thereby possibly causing damage to the BAW filter device structure and reducing the reliability of the BAW filter, no effective solution has been proposed so far. Summary of the invention

[0009] The present disclosure provides a method for manufacturing a bulk acoustic wave filter and a bulk acoustic wave filter, so as to at least solve the technical problem in the prior art that a certain stress difference exists between the piezoelectric layer of the bulk acoustic wave filter and an adjacent film, which may cause separation between the piezoelectric layer and the adjacent film or wafer warping, thereby causing damage to the bulk acoustic wave filter device structure and reducing the reliability of the bulk acoustic wave filter.

[0010] According to one aspect of the present application, a method for manufacturing a bulk acoustic wave filter is provided, comprising: manufacturing a first substrate; and forming a resonant structure on the first substrate, wherein the resonant structure comprises a working area and a non-working area surrounding the working area, and wherein a concave-convex structure is formed between at least one surface of a piezoelectric layer of the resonant structure and an adjacent membrane layer in the non-working area.

[0011] Optionally, the process of forming a bulk acoustic wave resonance structure on a first substrate includes: depositing a first electrode on the first substrate; and depositing a piezoelectric layer on the first electrode.

[0012] Optionally, the process of forming a resonant structure on the first substrate also includes: forming a concave-convex structure in a non-working area of ​​the piezoelectric layer; and depositing a second electrode on the piezoelectric layer, wherein a second concave-convex structure corresponding to the first concave-convex structure of the piezoelectric layer is formed on a surface of the second electrode adjacent to the piezoelectric layer in the non-working area.

[0013] Optionally, the process of forming a resonant structure on the first substrate also includes: forming a fence layer on the piezoelectric layer and the second electrode, wherein a fourth concave-convex structure corresponding to the third concave-convex structure of the piezoelectric layer is formed on the surface of the fence layer adjacent to the piezoelectric layer in the non-working area.

[0014] Optionally, a sixth concave-convex structure corresponding to the fifth concave-convex structure of the second electrode is formed on a surface of the fence layer adjacent to the second electrode in the non-working area.

[0015] Optionally, the operation of forming a fence layer on the piezoelectric layer and the second electrode includes: depositing a sacrificial layer on the working areas of the piezoelectric layer and the second electrode; and depositing the fence layer on the piezoelectric layer, the sacrificial layer and the second electrode.

[0016] Optionally, the process of forming a resonant structure on a first substrate further includes: depositing a second substrate on the fence layer; flipping the entire layer and removing the first substrate; and corroding the sacrificial layer to form a resonant cavity in the resonant structure.

[0017] Optionally, the process of depositing the first electrode on the first substrate includes: depositing a blocking layer on the first substrate, and forming a seventh concave-convex structure on the surface of the non-working area of ​​the blocking layer; and depositing the first electrode on the blocking layer, wherein an eighth concave-convex structure corresponding to the seventh concave-convex structure is formed on the surface of the first electrode adjacent to the blocking layer in the non-working area, and a ninth concave-convex structure corresponding to the eighth concave-convex structure is formed on the surface opposite to the blocking layer.

[0018] Optionally, the operation of forming a concave-convex structure in the non-working area of ​​the piezoelectric layer includes: forming a tenth concave-convex structure corresponding to the ninth concave-convex structure on a surface adjacent to the first electrode, and forming an eleventh concave-convex structure corresponding to the tenth concave-convex structure on a surface away from the first electrode.

[0019] Optionally, the operation of depositing the second electrode on the piezoelectric layer includes: forming a twelfth concave-convex structure corresponding to the eleventh concave-convex structure on a surface adjacent to the piezoelectric layer; and forming a thirteenth concave-convex structure corresponding to the twelfth concave-convex structure on a surface away from the piezoelectric layer.

[0020] Optionally, the process of forming a resonant structure on the first substrate includes: forming a fence layer on the piezoelectric layer and the second electrode, wherein a fourteenth concave-convex structure corresponding to the eleventh concave-convex structure of the piezoelectric layer is formed on the surface of the fence layer adjacent to the piezoelectric layer in the non-working area.

[0021] Optionally, a fifteenth concave-convex structure corresponding to the thirteenth concave-convex structure of the second electrode is formed on a surface of the fence layer adjacent to the second electrode in the non-working area.

[0022] According to another aspect of the present application, a bulk acoustic wave filter is provided, comprising: a second substrate and a resonant structure, wherein the resonant structure is formed on the second substrate, and wherein the resonant structure comprises a working area and a non-working area surrounding the working area, and a concave-convex structure is formed between at least one surface of the piezoelectric layer of the resonant structure in the non-working area and an adjacent membrane layer.

[0023] Optionally, the resonant structure includes: a fence layer and a second electrode, wherein the fence layer is formed on the second substrate, and a sixth concave-convex structure is formed on the surface of the fence layer in the non-working area opposite to the second substrate; and the second electrode is formed on the fence layer, and a fifth concave-convex structure corresponding to the sixth concave-convex structure is formed on the surface of the second electrode in the non-working area close to the fence layer.

[0024] Optionally, a second concave-convex structure corresponding to the fifth concave-convex structure is formed on a surface of the second electrode in the non-working area which is away from the fence layer.

[0025] Optionally, the resonant structure also includes: a piezoelectric layer and a first electrode, wherein a fourth concave-convex structure is formed on a surface of the fence layer in a non-working area that is opposite to the second substrate; the piezoelectric layer is formed on the fence layer and the second electrode, and wherein a third concave-convex structure corresponding to the fourth concave-convex structure is formed on a surface of the piezoelectric layer in the non-working area that is close to the fence layer, and a first concave-convex structure corresponding to the second concave-convex structure is formed on a surface of the piezoelectric layer in the non-working area that is close to the second electrode; and the first electrode is formed on the piezoelectric layer.

[0026] Optionally, the resonant structure includes: a fence layer and a second electrode, wherein the fence layer is formed on the second substrate, and a fifteenth concave-convex structure is formed on the surface of the fence layer in the non-working area opposite to the second substrate; and the second electrode is formed on the fence layer, and a thirteenth concave-convex structure corresponding to the fifteenth concave-convex structure is formed on the surface of the second electrode in the non-working area close to the fence layer.

[0027] Optionally, a twelfth concave-convex structure corresponding to the thirteenth concave-convex structure is formed on a surface of the second electrode in the non-working area which is away from the fence layer.

[0028] Optionally, the resonant structure also includes: a piezoelectric layer and a first electrode, wherein a fourteenth concave-convex structure is formed on a surface of the fence layer in the non-working area that is opposite to the second substrate; the piezoelectric layer is formed on the fence layer and the second electrode, and wherein an eleventh concave-convex structure corresponding to the fourteenth concave-convex structure is formed on a surface of the piezoelectric layer in the non-working area that is close to the fence layer, and a tenth concave-convex structure corresponding to the twelfth concave-convex structure is formed on a surface of the piezoelectric layer in the non-working area that is close to the second electrode; and the first electrode is formed on the piezoelectric layer, and a ninth concave-convex structure is formed on a surface of the first electrode that is close to the non-working area of ​​the piezoelectric layer, and an eighth concave-convex structure corresponding to the ninth concave-convex structure is formed on a surface of the first electrode that is close to the non-working area of ​​the piezoelectric layer.

[0029] In order to solve the problems existing in the prior art, the present application forms a concave-convex structure between at least one surface of the non-working area of ​​the piezoelectric layer and the adjacent film layer in advance when making the resonant structure. The concave-convex structure can change the surface morphology of the piezoelectric layer and increase the contact area between the piezoelectric layer and the adjacent film layer. Thus, when the contact area between the piezoelectric layer and the adjacent film layer is increased, local stress concentration can be effectively avoided, and stress distribution can be made more uniform, thereby reducing stress difference.

[0030] Furthermore, since the technical solution provided in the present application reduces the stress difference between the piezoelectric layer and the adjacent film, separation or wafer warping between the piezoelectric layer and the adjacent film can be effectively avoided, thereby ensuring the life of the BAW filter and increasing the reliability of the BAW filter.

[0031] This solves the technical problem in the prior art that a certain stress difference between the piezoelectric layer of the BAW filter and the adjacent film may cause separation between the piezoelectric layer and the adjacent film or wafer warping, which may cause damage to the BAW filter device structure and reduce the reliability of the BAW filter.

[0032] Based on the detailed description of the specific embodiments of the present application in combination with the accompanying drawings below, those skilled in the art will become more aware of the above and other objects, advantages and features of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Hereinafter, some specific embodiments of the present application will be described in detail in an exemplary and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the accompanying drawings: Figure 1 is a flow chart of a method for manufacturing a bulk acoustic wave filter according to an embodiment of the present application; Figure 2 is a schematic diagram of depositing a first electrode and a piezoelectric layer on a first substrate according to an embodiment of the present application; Figure 3 is a schematic diagram of forming a concave-convex structure in a non-working area of ​​a piezoelectric layer according to an embodiment of the present application; Figure 4 is a schematic diagram of a working area and a non-working area according to an embodiment of the present application; Figure 5 is a schematic diagram of depositing a second electrode on one side of a first electrode according to an embodiment of the present application; Figure 6 is a schematic diagram of depositing a sacrificial layer on the working area of ​​the piezoelectric layer and the second electrode according to an embodiment of the present application; Figure 7is a schematic diagram of depositing a fence layer on a piezoelectric layer, a sacrificial layer and a second electrode according to an embodiment of the present application; Figure 8 is a schematic diagram of depositing a second substrate on one side of the piezoelectric layer of the fence layer according to an embodiment of the present application; Fig. 9 is a schematic diagram of a bulk acoustic wave filter according to an embodiment of the present application; Fig.10 is a schematic structural diagram of another bulk acoustic wave filter according to an embodiment of the present application; Fig.11 is a schematic diagram of forming a seventh concave-convex structure on a barrier layer according to an embodiment of the present application; Fig.12 is a schematic diagram of depositing a first electrode on a barrier layer according to an embodiment of the present application; Fig.13 is a schematic diagram of depositing a piezoelectric layer on one side of a first electrode according to an embodiment of the present application; Fig.14 is a schematic diagram of another BAW filter according to an embodiment of the present application. DETAILED DESCRIPTION

[0034] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present disclosure may be combined with each other. The present disclosure will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0035] In order to enable those skilled in the art to better understand the scheme of the present disclosure, the technical scheme in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present disclosure.

[0036] It should be noted that the terms "first", "second", etc. in the specification and claims of the present disclosure and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchanged where appropriate, so as to describe the embodiments of the present disclosure described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0037] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0038] Secondly, the present application is described in detail with reference to the schematic diagram. When describing the embodiments of the present application in detail, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present application. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0039] According to a first aspect of the present embodiment, a method for manufacturing a bulk acoustic wave filter is provided. Figure 1 A schematic diagram showing the process of the method is shown in FIG. Figure 1 As shown, the method includes: S101: manufacturing a first substrate; and S102: forming a resonant structure on a first substrate, wherein the resonant structure includes a working area and a non-working area surrounding the working area, and wherein a concave-convex structure is formed between at least one surface of a piezoelectric layer of the resonant structure and an adjacent membrane layer in the non-working area.

[0040] The method for manufacturing a bulk acoustic wave filter provided by an embodiment of the present disclosure is adopted, by manufacturing a first substrate and forming a resonant structure on the first substrate. The resonant structure includes a working area and a non-working area surrounding the working area. And a concave-convex structure is formed between at least one surface of the piezoelectric layer of the resonant structure and the adjacent film layer in the non-working area. The working area is used to indicate the part directly involved in the resonance of the acoustic wave, usually the overlapping area of ​​the piezoelectric layer and the upper and lower electrodes, and the structure is designed to generate and maintain a bulk acoustic wave of a specific frequency. The non-working area is used to indicate the structure surrounding the working area, which is used to support, isolate, and reflect the sound waves, prevent energy leakage, suppress unnecessary vibration modes, and ensure the performance of the working area.

[0041] Therefore, what is different from the prior art is that, when making the resonant structure, the present application pre-forms a concave-convex structure between at least one surface of the non-working area of ​​the piezoelectric layer and the adjacent film layer. The concave-convex structure can change the surface morphology of the piezoelectric layer and increase the contact area between the piezoelectric layer and the adjacent film layer. Therefore, when the contact area between the piezoelectric layer and the adjacent film layer is increased, local stress concentration can be effectively avoided, and it helps to make the stress distribution more uniform, thereby reducing the stress difference. Furthermore, since the technical solution provided by the present application reduces the stress difference between the piezoelectric layer and the adjacent film, it can effectively avoid separation or wafer warping between the piezoelectric layer and the adjacent film, thereby ensuring the life of the bulk acoustic wave filter and increasing the reliability of the bulk acoustic wave filter.

[0042] This solves the technical problem in the prior art that a certain stress difference between the piezoelectric layer of the BAW filter and the adjacent film may cause separation between the piezoelectric layer and the adjacent film or wafer warping, which may cause damage to the BAW filter device structure and reduce the reliability of the BAW filter.

[0043] Example 1 The following are specific steps for manufacturing a bulk acoustic wave filter provided in an embodiment of the present application: refer to Figure 2 As shown, first, a first substrate 110 to be removed is prepared. Optionally, the first substrate 110 is made of silicon, silicon carbide or sapphire. Further, a first electrode 120 is deposited on one side of the first substrate 110, and a piezoelectric layer 130 is deposited on a side of the first electrode 120 away from the first substrate 110. The first electrode 120 can be, for example, an upper electrode layer.

[0044] refer to Figure 3 As shown, after the piezoelectric layer 130 is deposited on the side of the first electrode 120 away from the first substrate 110, a concave-convex structure is further formed in the non-working area of ​​the piezoelectric layer 130. The concave-convex structure in the non-working area of ​​the piezoelectric layer 130 includes a first concave-convex structure 131 and a third concave-convex structure 132, and the first concave-convex structure 131 and the third concave-convex structure 132 are arranged relative to the working area.

[0045] In addition, a protective layer may be deposited on the surface of the piezoelectric layer 130. The protective layer is used to protect the piezoelectric layer 130 corresponding to the working area to prevent the piezoelectric layer 130 from being contaminated by subsequent processes. The film thickness of the protective layer is 100-500nm, and the uniformity is less than 5%.

[0046] Further, refer to Figure 4 As shown, in this embodiment, Figure 4The pentagonal part in the figure represents the working area, and the area other than the pentagonal part is the non-working area, and the non-working area is provided with a plurality of through holes 135 of different shapes. Among them, the borders of the working areas of the plurality of BAW filters and the plurality of through holes 135 in the non-working areas are the piezoelectric layer etching areas. Thus, when a plurality of through holes 135 are etched in the non-working area of ​​each BAW filter and the borders of the plurality of BAW filters are etched, the stress can be further reduced.

[0047] Optionally, the shape of the through hole 135 may be, for example, square, triangle, or circle, which is not limited here. And the etching depth (ie, the height of the etched through hole) needs to be less than the thickness of the piezoelectric layer 130, for example, the etching depth is 10 nm to 1000 nm.

[0048] Further, refer to Figure 5 As shown in FIG. 1 , the second electrode 140 is deposited on the side of the piezoelectric layer 130 away from the first electrode 120. When the second electrode 140 is deposited, a portion of the non-working area of ​​the second electrode 140 is etched to form a Figure 4 In addition, since the piezoelectric layer 130 is formed with the first concavo-convex structure 131, when the second electrode 140 is deposited, the second electrode 140 has a second concavo-convex structure 141 corresponding to the first concavo-convex structure 131 formed on the surface adjacent to the piezoelectric layer 130 in the non-working area. The second electrode 140 may be, for example, a lower electrode layer.

[0049] With reference to the above, it can be seen that, since the corresponding concave-convex structures (i.e., the first concave-convex structure 131 and the second concave-convex structure 141) are formed between the piezoelectric layer 130 and the second electrode 140, the contact area between the piezoelectric layer 130 and the second electrode 140 is further increased. Thus, the stress difference between the piezoelectric layer 130 and the second electrode 140 can be reduced, and the film separation or wafer warping between the piezoelectric layer 130 and the second electrode 140 can be effectively avoided.

[0050] In addition, since the first concave-convex structure 131 is etched in the non-working area of ​​the piezoelectric layer 130, when the second electrode 140 is deposited, a fifth concave-convex structure 142 corresponding to the second concave-convex structure 141 is formed on the surface of the second electrode 140 opposite to the piezoelectric layer 130 in the non-working area.

[0051] Then, refer to Figure 6 As shown, a sacrificial layer 150 is deposited in the working area of ​​the piezoelectric layer 130 and the second electrode 140, and the fifth concavo-convex structure 142 of the second electrode 140 and the third concavo-convex structure 132 of the piezoelectric layer 130 are exposed to the outside. Figure 7As shown, a fence layer 160 is deposited on the piezoelectric layer 130, the sacrificial layer 150 and the second electrode 140. Since the piezoelectric layer 130 is formed with a third concave-convex structure 132, when the fence layer 160 is deposited, a fourth concave-convex structure 161 corresponding to the third concave-convex structure 132 is formed on the surface of the fence layer 160 adjacent to the piezoelectric layer 130 in the non-working area. Similarly, since the second electrode 140 is formed with a fifth concave-convex structure 142, when the fence layer 160 is deposited, a sixth concave-convex structure 162 corresponding to the fifth concave-convex structure 142 of the second electrode 140 is formed on the surface of the fence layer 160 adjacent to the second electrode 140 in the non-working area.

[0052] With reference to the above, it can be seen that, since corresponding concave-convex structures (i.e., the third concave-convex structure 132 and the fourth concave-convex structure 161) are formed between the fence layer 160 and the piezoelectric layer 130, the contact area between the fence layer 160 and the piezoelectric layer 130 is further increased. Thus, the stress difference between the fence layer 160 and the piezoelectric layer 130 can be reduced, and thus, film separation or wafer warping between the fence layer 160 and the piezoelectric layer 130 can be effectively avoided.

[0053] Similarly, since corresponding concave-convex structures (i.e., the fifth concave-convex structure 142 and the sixth concave-convex structure 162) are formed between the second electrode 140 and the fence layer 160, the contact area between the second electrode 140 and the fence layer 160 is further increased. Thus, the stress difference between the second electrode 140 and the fence layer 160 can be reduced, and the film separation or wafer warping between the second electrode 140 and the fence layer 160 can be effectively avoided.

[0054] Further, refer to Figure 8 As shown, a second substrate 170 is then deposited on the side of the fence layer 160 away from the piezoelectric layer 130. Then, the whole is turned over and the first substrate 110 is removed. Further, the sacrificial layer 150 is etched to form a resonant cavity in the resonant structure. Finally, the first electrode 120 is etched to finally form Fig. 9 A bulk acoustic wave filter is shown.

[0055] Optionally, the first electrode 120 may be etched by dry etching or wet etching.

[0056] Example 2 The following are specific steps for manufacturing another bulk acoustic wave filter provided in an embodiment of the present application: Specific steps are as follows: Figure 2~Figure 8First, a first substrate 110 to be removed is prepared. Optionally, the first substrate 110 is made of silicon, silicon carbide or sapphire. Further, a first electrode 120 is deposited on one side of the first substrate 110, and a piezoelectric layer 130 is deposited on a side of the first electrode 120 away from the first substrate 110. The first electrode 120 may be, for example, an upper electrode layer.

[0057] Then, a concavo-convex structure is formed in the non-working area of ​​the piezoelectric layer 130. The concavo-convex structure in the non-working area of ​​the piezoelectric layer 130 includes a third concavo-convex structure 132. Optionally, the non-working area of ​​the piezoelectric layer 130 can be etched by dry etching or wet etching to form the third concavo-convex structure 132. Therefore, unlike the above-mentioned embodiment 1, in this embodiment, only the piezoelectric layer 130 is etched to generate the third concavo-convex structure 132, and both ends of the non-working area of ​​the piezoelectric layer 130 are not etched.

[0058] Then, the second electrode 140 is deposited on the end of the piezoelectric layer 130 where the first concavo-convex structure 131 is not formed, and the surface of the second electrode 140 away from the piezoelectric layer 130 is etched to form a fifth concavo-convex structure 142 .

[0059] Optionally, the non-working area of ​​the second electrode 140 may be etched by dry etching or wet etching to form the fifth concave-convex structure 142 .

[0060] Furthermore, a sacrificial layer 150 is deposited in the working areas of the piezoelectric layer 130 and the second electrode 140 , so that the fifth concavo-convex structure 142 of the second electrode 140 and the third concavo-convex structure 132 of the piezoelectric layer 130 are exposed to the outside.

[0061] And a fence layer 160 is deposited on the piezoelectric layer 130, the sacrificial layer 150 and the second electrode 140. Among them, since the piezoelectric layer 130 is formed with a third concave-convex structure 132, when the fence layer 160 is deposited, a fourth concave-convex structure 161 corresponding to the third concave-convex structure 132 is formed on the surface of the fence layer 160 adjacent to the piezoelectric layer 130 in the non-working area. Similarly, since the second electrode 140 is formed with a fifth concave-convex structure 142, when the fence layer 160 is deposited, a sixth concave-convex structure 162 corresponding to the fifth concave-convex structure 142 of the second electrode 140 is formed on the surface of the fence layer 160 adjacent to the second electrode 140 in the non-working area.

[0062] With reference to the above contents, it can be known that, since corresponding concave-convex structures (i.e., the third concave-convex structure 132 and the fourth concave-convex structure 161) are formed between the fence layer 160 and the piezoelectric layer 130, the contact area between the fence layer 160 and the piezoelectric layer 130 is further increased. Thus, the stress difference between the fence layer 160 and the piezoelectric layer 130 can be reduced, and thus, film separation or wafer warping between the fence layer 160 and the piezoelectric layer 130 can be effectively avoided.

[0063] Similarly, since corresponding concave-convex structures (i.e., the fifth concave-convex structure 142 and the sixth concave-convex structure 162) are formed between the second electrode 140 and the fence layer 160, the contact area between the second electrode 140 and the fence layer 160 is further increased. Thus, the stress difference between the second electrode 140 and the fence layer 160 can be reduced, and the film separation or wafer warping between the second electrode 140 and the fence layer 160 can be effectively avoided.

[0064] Then, a second substrate 170 is deposited on the side of the fence layer 160 away from the piezoelectric layer 130. Then, the whole is turned over and the first substrate 110 is removed. Further, the sacrificial layer 150 is etched to form a resonant cavity in the resonant structure. Finally, the first electrode 120 is etched to finally form the following structure: Fig.10 A bulk acoustic wave filter is shown.

[0065] Optionally, the first electrode 120 may be etched by dry etching or wet etching.

[0066] Example 3 The following are specific steps for manufacturing another BAW filter provided in the embodiment of the present application: refer to Fig.11 As shown, first, a first substrate 110 to be removed is prepared. Optionally, the first substrate 110 is made of silicon, silicon carbide or sapphire. Further, a barrier layer 180 is deposited on one side of the first substrate 110, and the surface of the non-working area of ​​the barrier layer 180 is etched to form the seventh concave-convex structure 181.

[0067] Optionally, the non-working area of ​​the blocking layer 180 may be etched by dry etching or wet etching to form the seventh concavo-convex structure 181 .

[0068] Further, refer to Fig.12As shown, the first electrode 120 is deposited on the barrier layer 180. And because the seventh concavo-convex structure 181 is formed in the non-working area of ​​the barrier layer 180 away from the first substrate 110, when the first electrode 120 is deposited, the surface of the first electrode 120 adjacent to the barrier layer 180 in the non-working area is formed with an eighth concavo-convex structure 121 corresponding to the seventh concavo-convex structure 181, and the surface of the first electrode 120 opposite to the barrier layer 180 in the non-working area is formed with a ninth concavo-convex structure 122 corresponding to the eighth concavo-convex structure 121. The first electrode 120 may be, for example, an upper electrode layer.

[0069] Then, refer to Fig.13 As shown, the piezoelectric layer 130 is deposited on the side of the first electrode 120 away from the first substrate 110. And because the first electrode 120 is formed with the ninth concavo-convex structure 122, when the piezoelectric layer 130 is deposited, the piezoelectric layer 130 is formed with the tenth concavo-convex structure 133 corresponding to the ninth concavo-convex structure 122 on the surface adjacent to the first electrode 120 in the non-working area. Further, because the first electrode 120 is formed with the tenth concavo-convex structure 133, the piezoelectric layer 130 is formed with the eleventh concavo-convex structure 134 corresponding to the tenth concavo-convex structure 133 on the surface opposite to the first electrode 120 in the non-working area. Therefore, in this embodiment, since the barrier layer 180 is deposited in advance and the barrier layer 180 is etched, it is not necessary to etch the surface of the piezoelectric layer 130, and the concavo-convex structure can also be formed on the surface of the piezoelectric layer 130.

[0070] Specific steps are as follows: Figure 5~Figure 8 , and then the second electrode 140 is deposited on the side of the piezoelectric layer 130 away from the first electrode 120. And because the piezoelectric layer 130 is formed with the eleventh concave-convex structure 134, when the second electrode 140 is deposited, the surface of the second electrode 140 adjacent to the piezoelectric layer 130 in the non-working area is formed with the twelfth concave-convex structure 143 corresponding to the eleventh concave-convex structure 134, and the surface of the second electrode 140 opposite to the piezoelectric layer 130 in the non-working area is formed with the thirteenth concave-convex structure 144 corresponding to the twelfth concave-convex structure 143. The second electrode 140 may be, for example, a lower electrode layer.

[0071] Further, a sacrificial layer 150 is deposited in the working area of ​​the piezoelectric layer 130 and the second electrode 140, and the thirteenth concavo-convex structure 144 of the second electrode 140 and the eleventh concavo-convex structure 134 of the piezoelectric layer 130 are exposed to the outside. A fence layer 160 is deposited on the piezoelectric layer 130, the sacrificial layer 150 and the second electrode 140. Among them, since the piezoelectric layer 130 is formed with the eleventh concavo-convex structure 134, when the fence layer 160 is deposited, the fence layer 160 is formed with a fourteenth concavo-convex structure 163 corresponding to the eleventh concavo-convex structure 134 on the surface adjacent to the piezoelectric layer 130 in the non-working area. Similarly, since the second electrode 140 is formed with the thirteenth concavo-convex structure 144, when the fence layer 160 is deposited, the fence layer 160 is formed with a fifteenth concavo-convex structure 164 corresponding to the thirteenth concavo-convex structure 144 of the second electrode 140 on the surface adjacent to the second electrode 140 in the non-working area.

[0072] With reference to the above contents, it can be known that, since the first electrode 120 and the piezoelectric layer 130 have corresponding concave-convex structures (i.e., the ninth concave-convex structure 122 and the tenth concave-convex structure 133), the contact area between the first electrode 120 and the piezoelectric layer 130 is further increased. Thus, the stress difference between the first electrode 120 and the piezoelectric layer 130 can be reduced, and the film separation or wafer warping between the first electrode 120 and the piezoelectric layer 130 can be effectively avoided.

[0073] Similarly, since corresponding concave-convex structures (i.e., the eleventh concave-convex structure 134 and the twelfth concave-convex structure 143) are formed between the piezoelectric layer 130 and the second electrode 140, the contact area between the piezoelectric layer 130 and the second electrode 140 is further increased. Thus, the stress difference between the piezoelectric layer 130 and the second electrode 140 can be reduced, and the film separation or wafer warping between the piezoelectric layer 130 and the second electrode 140 can be effectively avoided.

[0074] Similarly, since corresponding concave-convex structures (i.e., the eleventh concave-convex structure 134 and the fourteenth concave-convex structure 163) are formed between the piezoelectric layer 130 and the fence layer 160, the contact area between the piezoelectric layer 130 and the fence layer 160 is further increased. Thus, the stress difference between the piezoelectric layer 130 and the fence layer 160 can be reduced, and the film separation or wafer warping between the piezoelectric layer 130 and the fence layer 160 can be effectively avoided.

[0075] Similarly, since corresponding concave-convex structures (i.e., the thirteenth concave-convex structure 144 and the fifteenth concave-convex structure 164) are formed between the second electrode 140 and the fence layer 160, the contact area between the second electrode 140 and the fence layer 160 is further increased. Thus, the stress difference between the second electrode 140 and the fence layer 160 can be reduced, and the film separation or wafer warping between the second electrode 140 and the fence layer 160 can be effectively avoided.

[0076] Then, a second substrate 170 is deposited on the side of the fence layer 160 away from the piezoelectric layer 130. Then, the whole is turned over, and the first substrate 110 and the barrier layer 180 are removed. Further, the sacrificial layer 150 is etched to form a resonant cavity in the resonant structure. Finally, the first electrode 120 is etched, and a part of the concave-convex structure of the non-working area of ​​the first electrode 120 is removed, so as to finally form the following structure: Fig.14 A bulk acoustic wave filter is shown.

[0077] According to another aspect of the present application, a bulk acoustic wave filter is also provided, comprising: a second substrate 170 and a resonant structure, wherein the resonant structure is formed on the second substrate 170, and wherein the resonant structure comprises a working area and a non-working area surrounding the working area, and a concave-convex structure is formed between at least one surface of the piezoelectric layer 130 of the resonant structure in the non-working area and an adjacent membrane layer.

[0078] Optionally, the resonant structure includes: a fence layer 160 and a second electrode 140, wherein the fence layer 160 is formed on the second substrate 170, and a sixth concave-convex structure 162 is formed on the surface of the fence layer 160 in the non-working area opposite to the second substrate 170; and the second electrode 140 is formed on the fence layer 160, and a fifth concave-convex structure 142 corresponding to the sixth concave-convex structure 162 is formed on the surface of the second electrode 140 in the non-working area close to the fence layer 160.

[0079] Optionally, a second concave-convex structure 141 corresponding to the fifth concave-convex structure 142 is formed on a surface of the second electrode 140 in the non-working area which is away from the fence layer 160 .

[0080] Optionally, the resonant structure also includes: a piezoelectric layer 130 and a first electrode 120, wherein a fourth concave-convex structure 161 is formed on the surface of the fence layer 160 in the non-working area opposite to the second substrate 170; the piezoelectric layer 130 is formed on the fence layer 160 and the second electrode 140, and wherein a third concave-convex structure 132 corresponding to the fourth concave-convex structure 161 is formed on the surface of the piezoelectric layer 130 in the non-working area close to the fence layer 160, and a first concave-convex structure 131 corresponding to the second concave-convex structure 141 is formed on the surface of the piezoelectric layer 130 in the non-working area close to the second electrode 140; and the first electrode 120 is formed on the piezoelectric layer 130.

[0081] Optionally, the resonant structure includes: a fence layer 160 and a second electrode 140, wherein the fence layer 160 is formed on the second substrate 170, and a fifteenth concave-convex structure 164 is formed on the surface of the fence layer 160 in the non-working area opposite to the second substrate 170; and the second electrode 140 is formed on the fence layer 160, and a thirteenth concave-convex structure 144 corresponding to the fifteenth concave-convex structure 164 is formed on the surface of the second electrode 140 in the non-working area close to the fence layer 160.

[0082] Optionally, a twelfth concave-convex structure 143 corresponding to the thirteenth concave-convex structure 144 is formed on a surface of the second electrode 140 that is away from the fence layer 160 in the non-working area.

[0083] Optionally, the resonant structure also includes: a piezoelectric layer 130 and a first electrode 120, wherein a fourteenth concave-convex structure 163 is formed on the surface of the fence layer 160 in the non-working area opposite to the second substrate 170; the piezoelectric layer 130 is formed on the fence layer 160 and the second electrode 140, and wherein an eleventh concave-convex structure 134 corresponding to the fourteenth concave-convex structure 163 is formed on the surface of the piezoelectric layer 130 in the non-working area close to the fence layer 160, and a tenth concave-convex structure 133 corresponding to the twelfth concave-convex structure 143 is formed on the surface of the piezoelectric layer 130 in the non-working area close to the second electrode 140; and the first electrode 120 is formed on the piezoelectric layer 130, and a ninth concave-convex structure 122 is formed on the surface of the first electrode 120 close to the non-working area of ​​the piezoelectric layer 130, and an eighth concave-convex structure 121 corresponding to the ninth concave-convex structure 122 is formed on the surface of the first electrode 120 opposite to the non-working area of ​​the piezoelectric layer 130.

[0084] In order to solve the problems existing in the prior art, the present application forms a concave-convex structure between at least one surface of the non-working area of ​​the piezoelectric layer and the adjacent film layer in advance when making the resonant structure. The concave-convex structure can change the surface morphology of the piezoelectric layer and increase the contact area between the piezoelectric layer and the adjacent film layer. Thus, when the contact area between the piezoelectric layer and the adjacent film layer is increased, local stress concentration can be effectively avoided, and stress distribution can be made more uniform, thereby reducing stress difference.

[0085] Furthermore, since the technical solution provided in the present application reduces the stress difference between the piezoelectric layer and the adjacent film layer, it can effectively avoid separation or wafer warping between the piezoelectric layer and the adjacent film, thereby ensuring the life of the BAW filter and increasing the reliability of the BAW filter.

[0086] This solves the technical problem in the prior art that a certain stress difference exists between the thin film layers of the BAW filter, which may cause separation between the thin film layers or wafer warping, thereby possibly causing damage to the BAW filter device structure and reducing the reliability of the BAW filter.

[0087] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values ​​do not limit the scope of the present disclosure. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0088] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0089] In the description of the present disclosure, it is necessary to understand that the orientation or positional relationship indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present disclosure and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the scope of protection of the present disclosure; the directional words "inside and outside" refer to the inside and outside relative to the outline of each component itself.

[0090] The above is only a preferred specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for manufacturing a bulk acoustic wave filter, characterized in that: include: Manufacturing a first substrate (110); as well as A resonant structure is formed on the first substrate (110), wherein the resonant structure comprises a working area and a non-working area surrounding the working area, and wherein a concave-convex structure is formed between at least one surface of the piezoelectric layer (130) of the resonant structure and an adjacent membrane layer in the non-working area.

2. The method according to claim 1, characterized in that: The process of forming the resonant structure on the first substrate (110) comprises: depositing a first electrode (120) on the first substrate (110); and A piezoelectric layer (130) is deposited on the first electrode (120), wherein The process of forming the resonant structure on the first substrate (110) further includes: forming a concavo-convex structure in a non-working area of ​​the piezoelectric layer (130); and A second electrode (140) is deposited on the piezoelectric layer (130), wherein The second electrode (140) has a second concave-convex structure (141) formed on a surface adjacent to the piezoelectric layer (130) in a non-working area, corresponding to the first concave-convex structure (131) of the piezoelectric layer (130), wherein The process of forming the resonant structure on the first substrate (110) further includes: A fence layer (160) is formed on the piezoelectric layer (130) and the second electrode (140), wherein The fence layer (160) has a fourth concave-convex structure (161) formed on a surface adjacent to the piezoelectric layer (130) in the non-working area, the fourth concave-convex structure (161) corresponding to the third concave-convex structure (132) of the piezoelectric layer (130).

3. The method according to claim 2, characterized in that The fence layer (160) has a sixth concave-convex structure (162) formed on a surface adjacent to the second electrode (140) in a non-working area, corresponding to the fifth concave-convex structure (142) of the second electrode (140), wherein The operation of forming a fence layer (160) on the piezoelectric layer (130) and the second electrode (140) comprises: Depositing a sacrificial layer (150) on the working areas of the piezoelectric layer (130) and the second electrode (140); and The fence layer (160) is deposited on the piezoelectric layer (130), the sacrificial layer (150) and the second electrode (140).

4. The method according to claim 3, characterized in that The process of forming the resonant structure on the first substrate (110) further includes: Depositing a second substrate (170) on the fence layer (160); Turning the entire device over and removing the first substrate (110); and The sacrificial layer (150) is corroded to form a resonant cavity in the resonant structure.

5. The method according to claim 2, characterized in that: The process of depositing a first electrode (120) on the first substrate (110) comprises: Depositing a barrier layer (180) on the first substrate (110), and forming a seventh concavo-convex structure (181) on the surface of a non-working area of ​​the barrier layer (180); and The first electrode (120) is deposited on the barrier layer (180), wherein an eighth concave-convex structure (121) corresponding to the seventh concave-convex structure (181) is formed on a surface of the first electrode (120) adjacent to the barrier layer (180) in a non-working area, and a ninth concave-convex structure (122) corresponding to the eighth concave-convex structure (121) is formed on a surface opposite to the barrier layer (180).

6. The method according to claim 5, characterized in that The operation of forming a concave-convex structure in a non-working area of ​​the piezoelectric layer (130) comprises: A tenth concave-convex structure (133) corresponding to the ninth concave-convex structure (122) is formed on a surface adjacent to the first electrode (120), and an eleventh concave-convex structure (134) corresponding to the tenth concave-convex structure (133) is formed on a surface opposite to the first electrode (120).

7. The method according to claim 6, characterized in that The operation of depositing a second electrode (140) on the piezoelectric layer (130) comprises: forming a twelfth concave-convex structure (143) corresponding to the eleventh concave-convex structure (134) on a surface adjacent to the piezoelectric layer (130); and A thirteenth concave-convex structure (144) corresponding to the twelfth concave-convex structure (143) is formed on a surface opposite to the piezoelectric layer (130).

8. The method according to claim 7, characterized in that The process of forming the resonant structure on the first substrate (110) comprises: A fence layer (160) is formed on the piezoelectric layer (130) and the second electrode (140), wherein The fence layer (160) is formed with a fourteenth concave-convex structure (163) corresponding to the eleventh concave-convex structure (134) of the piezoelectric layer (130) on a surface adjacent to the piezoelectric layer (130) in the non-working area, wherein A fifteenth concave-convex structure (164) corresponding to the thirteenth concave-convex structure (144) of the second electrode (140) is formed on a surface of the fence layer (160) adjacent to the second electrode (140) in a non-working area.

9. The method according to claim 2, characterized in that: The method further comprises: etching and forming a plurality of through holes (135) in the non-working area, wherein the plurality of through holes (135) penetrates the piezoelectric layer (130), wherein The operation of etching and forming a plurality of through holes in the non-working area comprises: Etching the through hole (135) in a non-working area of ​​the piezoelectric layer (130) close to the first concavo-convex structure (131), wherein the depth of the through hole (135) is greater than or equal to the thickness of the piezoelectric layer (130); and / or The through hole (135) is etched in a non-working area of ​​the piezoelectric layer (130) close to the second concave-convex structure (141), wherein the depth of the through hole (135) is greater than or equal to the sum of the thicknesses of the first electrode (120) and the piezoelectric layer (130).

10. A bulk acoustic wave filter, characterized in that: include: A second substrate (170) and a resonant structure, wherein the resonant structure is formed on the second substrate (170), and wherein the resonant structure comprises a working area and a non-working area surrounding the working area, and a concave-convex structure is formed between at least one surface of the piezoelectric layer (130) of the resonant structure and an adjacent membrane layer in the non-working area.

11. The bulk acoustic wave filter according to claim 10, characterized in that The resonant structure comprises: a fence layer (160) and a second electrode (140), wherein The fence layer (160) is formed on the second substrate (170), and a sixth concavo-convex structure (162) is formed on a surface of the fence layer (160) in the non-working area that is away from the second substrate (170); and The second electrode (140) is formed on the fence layer (160), and a fifth concave-convex structure (142) corresponding to the sixth concave-convex structure (162) is formed on the surface of the second electrode (140) in the non-working area close to the fence layer (160).

12. The bulk acoustic wave filter according to claim 11, characterized in that The second electrode (140) is formed with a second concave-convex structure (141) corresponding to the fifth concave-convex structure (142) on a surface of the non-working area that is away from the fence layer (160).

13. The bulk acoustic wave filter according to claim 12, characterized in that The resonant structure further comprises: a piezoelectric layer (130) and a first electrode (120), wherein The fence layer (160) is formed with a fourth concavo-convex structure (161) on a surface of the non-working area that is away from the second substrate (170); The piezoelectric layer (130) is formed on the fence layer (160) and the second electrode (140), and a third concave-convex structure (132) corresponding to the fourth concave-convex structure (161) is formed on a surface of the piezoelectric layer (130) close to the fence layer (160) in the non-working area. The piezoelectric layer (130) has a first concave-convex structure (131) corresponding to the second concave-convex structure (141) formed on a surface of the non-working area close to the second electrode (140); and The first electrode (120) is formed on the piezoelectric layer (130).

14. The bulk acoustic wave filter according to claim 10, characterized in that The resonant structure comprises: a fence layer (160) and a second electrode (140), wherein The fence layer (160) is formed on the second substrate (170), and a fifteenth concavo-convex structure (164) is formed on a surface of the fence layer (160) in the non-working area that is away from the second substrate (170); and The second electrode (140) is formed on the fence layer (160), and a thirteenth concave-convex structure (144) corresponding to the fifteenth concave-convex structure (164) is formed on the surface of the second electrode (140) in the non-working area close to the fence layer (160).

15. The bulk acoustic wave filter according to claim 14, characterized in that The second electrode (140) is formed with a twelfth concave-convex structure (143) corresponding to the thirteenth concave-convex structure (144) on a surface of the non-working area that is away from the fence layer (160).

16. The bulk acoustic wave filter according to claim 15, characterized in that The resonant structure further comprises: a piezoelectric layer (130) and a first electrode (120), wherein The fence layer (160) is formed with a fourteenth concavo-convex structure (163) on a surface of the non-working area that is away from the second substrate (170); The piezoelectric layer (130) is formed on the fence layer (160) and the second electrode (140), and an eleventh concave-convex structure (134) corresponding to the fourteenth concave-convex structure (163) is formed on a surface of the piezoelectric layer (130) close to the fence layer (160) in the non-working area, The piezoelectric layer (130) is provided with a tenth concave-convex structure (133) corresponding to the twelfth concave-convex structure (143) on a surface of the non-working area close to the second electrode (140); and The first electrode (120) is formed on the piezoelectric layer (130), and a ninth concave-convex structure (122) is formed on a surface of the first electrode (120) close to a non-working area of ​​the piezoelectric layer (130), and an eighth concave-convex structure (121) corresponding to the ninth concave-convex structure (122) is formed on a surface of the first electrode (120) opposite to the non-working area of ​​the piezoelectric layer (130).

17. The bulk acoustic wave filter according to claim 13, wherein: The device further comprises: a plurality of through holes (135) etched and formed in the non-working area, wherein the plurality of through holes (135) penetrate the piezoelectric layer (130), wherein The through hole (135) is etched in a non-working area of ​​the piezoelectric layer (130) close to the first concavo-convex structure (131), wherein the depth of the through hole (135) is greater than or equal to the thickness of the piezoelectric layer (130); and / or The through hole (135) is etched in a non-working area of ​​the piezoelectric layer (130) close to the second concave-convex structure (141), wherein the depth of the through hole (135) is greater than or equal to the sum of the thicknesses of the first electrode (120) and the piezoelectric layer (130).

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