Bulk acoustic wave filter for improving film layer binding force and manufacturing method thereof

Abstract

The invention discloses a bulk acoustic wave filter for improving film layer binding force and a manufacturing method of the bulk acoustic wave filter. Relates to the technical field of filtering. The bulk acoustic wave filter comprises a substrate and a resonant structure, the resonant structure is arranged on the substrate, the resonant structure comprises a working area and a non-working area surrounding the working area, and a buffer structure is arranged between a piezoelectric layer of the resonant structure and an adjacent film layer in the non-working area. By introducing the buffer structure into the non-working area, the stress distribution between the piezoelectric layer and the adjacent film layer is more uniform, the stress difference between the piezoelectric layer and the adjacent film layer is reduced, and the piezoelectric layer and the adjacent film layer can be effectively prevented from being separated or a wafer is prevented from warping, so that the firmness of a device is enhanced, and the reliability of the device is improved. Therefore, the technical problems of device structure damage and reliability reduction risk of the bulk acoustic wave filter in the prior art due to the stress difference between the piezoelectric layer and the adjacent film are solved.

Description

Technical Field

[0001] The present application relates to the field of filtering technology, and in particular to a bulk acoustic wave filter with improved film layer bonding strength and a manufacturing method thereof. 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 will cause damage to the BAW filter device structure and reduce the reliability of the BAW filter.

[0006] With respect to the technical problem that the BAW filter in the prior art has the stress difference between the piezoelectric layer and the adjacent film, there is a risk of device structure damage and reduced reliability, and no effective solution has been proposed so far. Summary of the invention

[0007] The embodiments of the present disclosure provide a bulk acoustic wave filter with improved film layer bonding and a method for manufacturing the same, so as to at least solve the problem of device structure damage and reduced reliability risk in the prior art bulk acoustic wave filter due to the stress difference between the piezoelectric layer and the adjacent film.

[0008] According to one aspect of an embodiment of the present disclosure, a bulk acoustic wave filter with improved membrane layer bonding force is provided, comprising: a substrate and a resonant structure, wherein the resonant structure is arranged on the substrate, and the resonant structure comprises a working area and a non-working area surrounding the working area, and a buffer structure is provided between the piezoelectric layer of the resonant structure and the adjacent membrane layer in the non-working area.

[0009] Optionally, the resonant structure includes a first electrode, a second electrode and a fence layer, wherein the first electrode is arranged on a side of the piezoelectric layer close to the substrate and exposes at least a portion of the surface of the piezoelectric layer, and a first buffer structure is provided between the first electrode and the piezoelectric layer in the non-working area; the second electrode is arranged on a side of the piezoelectric layer away from the substrate; and the fence layer is arranged between the first electrode and the substrate and covers a portion of the surface of the first electrode close to the substrate and a portion of the exposed surface of the piezoelectric layer, and a second buffer structure is provided between the piezoelectric layer and the fence layer in the non-working area.

[0010] Optionally, in the non-working area, a surface of the first electrode close to the substrate has a convex structure, and the fence layer covers the convex structure and a portion of the flat surface of the first electrode close to the substrate.

[0011] Optionally, the BAW filter further comprises a first protective structure and a second protective structure; wherein the first protective structure is arranged on a surface of the first electrode close to the substrate and covers the protruding structure; and the second protective structure is arranged on an exposed surface of the piezoelectric layer close to the substrate and covers the second buffer structure.

[0012] Optionally, the resonant structure includes a first electrode, a second electrode and a fence layer, wherein the first electrode is arranged on a side of the piezoelectric layer close to the substrate and exposes at least a portion of the surface of the piezoelectric layer; the second electrode is arranged on a side of the piezoelectric layer away from the substrate; and the fence layer is arranged between the first electrode and the substrate and covers a portion of the surface of the first electrode close to the substrate and a portion of the exposed surface of the piezoelectric layer, and in the non-working area, a second buffer structure is provided between the piezoelectric layer and the fence layer, and a third buffer structure is provided between the first electrode and the fence layer.

[0013] Optionally, the resonant structure includes a first electrode, a second electrode and a fence layer, wherein the first electrode is arranged on a side of the piezoelectric layer close to the substrate and exposes at least a portion of the surface of the piezoelectric layer, and a first buffer structure is provided between the first electrode and the piezoelectric layer in the non-working area; the second electrode is arranged on a side of the piezoelectric layer away from the substrate; and the fence layer is arranged between the first electrode and the substrate and covers a portion of the surface of the first electrode close to the substrate and a portion of the exposed surface of the piezoelectric layer, and a second buffer structure is provided between the piezoelectric layer and the fence layer in the non-working area, and a third buffer structure is provided between the first electrode and the fence layer.

[0014] Optionally, the resonant structure further includes a first protective structure and a second protective structure; wherein the first protective structure is arranged on a surface of the first electrode close to the substrate and covers the third buffer structure; and the second protective structure is arranged on an exposed surface of the piezoelectric layer close to the substrate and covers the second buffer structure.

[0015] Optionally, the material of the buffer structure is phosphosilicate glass, undoped silicate glass or borophosphosilicate glass.

[0016] Optionally, the film layer thickness of the buffer structure is 50-500 nm.

[0017] According to another aspect of an embodiment of the present disclosure, there is also provided a method for manufacturing a bulk acoustic wave filter having improved membrane layer bonding strength, comprising: manufacturing a substrate and a resonant structure, wherein the resonant structure is disposed on the substrate, and the resonant structure comprises a working area and a non-working area surrounding the working area, and a buffer structure is provided between the piezoelectric layer of the resonant structure and an adjacent membrane layer in the non-working area.

[0018] Optionally, the process of making a resonant structure includes: making a first electrode, a second electrode and a fence layer, wherein the first electrode is arranged on a side of the piezoelectric layer close to the substrate and exposes at least a portion of the surface of the piezoelectric layer, and a first buffer structure is provided between the first electrode and the piezoelectric layer in the non-working area; the second electrode is arranged on a side of the piezoelectric layer away from the substrate; and the fence layer is arranged between the first electrode and the substrate and covers a portion of the surface of the first electrode close to the substrate and a portion of the exposed surface of the piezoelectric layer, and a second buffer structure is provided between the piezoelectric layer and the fence layer in the non-working area; a protruding structure is provided on the surface of the first electrode close to the substrate in the non-working area, and the fence layer covers the protruding structure and a portion of the flat surface of the first electrode close to the substrate; and the manufacturing method also includes: making a first protective structure and a second protective structure; wherein the first protective structure is arranged on a side of the first electrode close to the substrate and covers the protruding structure; and the second protective structure is arranged on the exposed surface of the piezoelectric layer close to the substrate and covers the second buffer structure.

[0019] Optionally, the process of making a resonant structure includes: making a first electrode, a second electrode and a fence layer, wherein the first electrode is arranged on a side of the piezoelectric layer close to the substrate and exposes at least part of the surface of the piezoelectric layer; the second electrode is arranged on a side of the piezoelectric layer away from the substrate; and the fence layer is arranged between the first electrode and the substrate, and covers part of the surface of the first electrode close to the substrate and part of the exposed surface of the piezoelectric layer, and a second buffer structure is provided between the piezoelectric layer and the fence layer in the non-working area, and a third buffer structure is provided between the first electrode and the fence layer; or the process of making a resonant structure includes: making A first electrode, a second electrode and a fence layer are provided, wherein the first electrode is provided on a side of the piezoelectric layer close to the substrate and exposes at least a portion of the surface of the piezoelectric layer, and a first buffer structure is provided between the first electrode and the piezoelectric layer in the non-working area; the second electrode is provided on a side of the piezoelectric layer away from the substrate; and the fence layer is provided between the first electrode and the substrate and covers a portion of the surface of the first electrode close to the substrate and a portion of the exposed surface of the piezoelectric layer, and a second buffer structure is provided between the piezoelectric layer and the fence layer in the non-working area and a third buffer structure is provided between the first electrode and the fence layer.

[0020] Optionally, the manufacturing method also includes: manufacturing a first protective structure and a second protective structure; wherein the first protective structure is arranged on a surface of the first electrode close to the substrate and covers the third buffer structure; and the second protective structure is arranged on an exposed surface of the piezoelectric layer close to the substrate and covers the second buffer structure.

[0021] Optionally, the material of the buffer structure is phosphosilicate glass, undoped silicate glass or borophosphosilicate glass; the film thickness of the buffer structure is 50-500 nm.

[0022] In the bulk acoustic wave filter and its manufacturing method for improving the bonding force of the film layer proposed in the present application, the bulk acoustic wave filter includes a substrate and a resonant structure, wherein the resonant structure is arranged on the substrate, the resonant structure includes a working area and a non-working area surrounding the working area, and a buffer structure is provided between the piezoelectric layer of the resonant structure and the adjacent film layer in the non-working area. By introducing the buffer structure in the non-working area, the stress distribution between the piezoelectric layer and the adjacent film layer is made more uniform, rather than concentrated in certain specific areas (such as the interface), avoiding the occurrence of stress peaks (i.e., stress concentration) in local areas, reducing the stress difference between the piezoelectric layer and the adjacent film layers, and being able to effectively avoid separation or wafer warping between the piezoelectric layer and the adjacent film, thereby enhancing the firmness of the device and improving the reliability of the device. This solves the technical problem in the prior art that the bulk acoustic wave filter has the risk of device structure damage and reduced reliability due to the stress difference between the piezoelectric layer and the adjacent film. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings described herein are used to provide a further understanding of the present disclosure and constitute a part of the present application. The illustrative embodiments of the present disclosure and their descriptions are used to explain the present disclosure and do not constitute an improper limitation on the present disclosure. In the drawings: Figure 1 A structural schematic diagram of a process for manufacturing a bulk acoustic wave filter for improving the bonding strength of a membrane layer provided in Example 1 of the present application; Figure 2 It is another structural schematic diagram of the manufacturing process of the bulk acoustic wave filter with improved film layer bonding force provided in the first embodiment of the present application; Figure 3 It is another structural schematic diagram of the manufacturing process of the bulk acoustic wave filter with improved film layer bonding force provided in the first embodiment of the present application; Figure 4 It is another structural schematic diagram of the manufacturing process of the bulk acoustic wave filter with improved film layer bonding force provided in the first embodiment of the present application; Figure 5 It is another structural schematic diagram of the manufacturing process of the bulk acoustic wave filter with improved film layer bonding force provided in the first embodiment of the present application; Figure 6 It is another structural schematic diagram of the manufacturing process of the bulk acoustic wave filter with improved film layer bonding force provided in the first embodiment of the present application; Figure 7 It is another structural schematic diagram of the manufacturing process of the bulk acoustic wave filter with improved film layer bonding force provided in the first embodiment of the present application; Figure 8 A schematic diagram of the structure of a bulk acoustic wave filter for improving the bonding strength of a membrane layer provided in the second embodiment of the present application; Fig. 9 A schematic diagram of the structure of a bulk acoustic wave filter for improving the bonding strength of a membrane layer provided in the third embodiment of the present application; Fig.10 A schematic diagram of the structure of a bulk acoustic wave filter for improving the bonding strength of a membrane layer provided in the fourth embodiment of the present application; Fig.11 A schematic diagram of the structure of a bulk acoustic wave filter for improving the bonding strength of a membrane layer provided in Example 5 of the present application; Fig.12 This is a schematic diagram of the structure of a bulk acoustic wave filter with improved membrane layer bonding strength provided in Example 6 of the present application. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the technical solutions of the present disclosure, the technical solutions 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 embodiments of a part 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 this field without making creative work should fall within the scope of protection of the present disclosure.

[0025] 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 data used in this way can be interchangeable where appropriate, so that the embodiments of the present disclosure described herein can be implemented in an order other than those illustrated or 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 that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products, or devices.

[0026] 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.

[0027] Definition of terms: Working area: refers to the part that directly participates in the resonance of the acoustic wave, usually the overlapping area of ​​the piezoelectric layer and the upper and lower electrodes. The structure is designed to generate and maintain a body acoustic wave of a specific frequency; Non-working area: The structure surrounding the working area is used to support, isolate, and reflect sound waves, prevent energy leakage, suppress unwanted vibration modes, and ensure the performance of the working area.

[0028] As described in the background technology section, a bulk acoustic wave filter includes multiple layers of thin films, and each layer of thin films is bonded to each other to form a bulk acoustic wave filter. However, due to the different material properties, different thermal expansion coefficients, lattice constant mismatch, film thickness differences, defects and impurities between the piezoelectric layer and the adjacent thin films, there is a certain stress difference between the piezoelectric layer and the adjacent thin films of the bulk acoustic wave filter. And because there is a certain stress difference between the piezoelectric layer and the adjacent thin films, separation or wafer warping may occur between the piezoelectric layer and the adjacent thin films. This may cause damage to the structure of the bulk acoustic wave filter device and reduce the reliability of the bulk acoustic wave filter.

[0029] In view of this, the embodiments of the present application provide a bulk acoustic wave filter with improved film layer bonding strength and a method for manufacturing the same. By introducing a buffer structure between the piezoelectric layer of the resonant structure and the adjacent film layer in the non-working area, the stress distribution between the piezoelectric layer and the adjacent film layer is made more uniform, rather than concentrated in certain specific areas (such as the interface), thereby avoiding stress peaks (i.e., stress concentration) in local areas, reducing the stress difference between the piezoelectric layer and the adjacent film layers, and effectively avoiding separation or wafer warping between the piezoelectric layer and the adjacent film, thereby enhancing the firmness of the device and improving the reliability of the device.

[0030] The following describes a bulk acoustic wave filter with improved film layer bonding strength and a method for manufacturing the same in conjunction with specific embodiments.

[0031] Embodiment 1 For ease of understanding, the present application first describes the method for manufacturing a bulk acoustic wave filter with improved film layer bonding. The method for manufacturing a bulk acoustic wave filter with improved film layer bonding provided in an embodiment of the present application includes: like Figure 1As shown, a second electrode layer 110 and a piezoelectric layer 120 are sequentially fabricated on a first substrate 100 used as a temporary substrate. The second electrode layer is used for subsequent fabrication of a second electrode.

[0032] Optionally, in one embodiment of the present application, the first substrate 100 is a silicon substrate, a silicon substrate on an insulator, a glass substrate, a silicon carbide substrate or a gallium arsenide (GaAs) substrate, etc.; the second electrode layer 110 may be an Al layer, a Cu layer, a Mo layer, an Au layer or a Pt layer, and may be formed by a physical vapor deposition (PVD) process; the piezoelectric layer 120 may be an AlN layer, a scandium-doped aluminum nitride (AlxSc1-xN) layer, a lithium niobate (LiNbO3) layer, a lithium tantalate (LiTaO3) layer or a quartz layer, etc., and may be a polycrystalline layer or a single crystal layer, and may be formed by PVD or metal organic chemical vapor deposition (MOCVD), etc.

[0033] like Figure 2 As shown, a buffer structure is formed in a non-working area on a surface of the piezoelectric layer 120 away from the first substrate 100 , wherein the buffer structure includes a first buffer structure 132 and a second buffer structure 131 .

[0034] Optionally, the material of the buffer structure is phospho-silicate glass (PSG), undoped silicate glass (USG) or boro-phospho-silicate glass (BPSG); the film thickness of the buffer structure is 50-500nm; the stress of the buffer structure is 0±50MPa; the distance between the buffer structure and the boundary of the subsequent sacrificial layer after etching is >2um, and the damage to the piezoelectric layer during the etching process is less than 10nm; the side wall angle (Profile) of the buffer structure after etching is controlled at 45±15 degrees.

[0035] like Figure 3 As shown, a first electrode layer is formed on the piezoelectric layer 120, and then the first electrode layer is etched to obtain a first electrode 140. The first electrode 140 exposes at least a portion of the surface of the piezoelectric layer 120 and covers the first buffer structure 132. Optionally, the first electrode layer may be an Al layer, a Cu layer, a Mo layer, an Au layer or a Pt layer, and may be formed by a physical vapor deposition (PVD) process; Optionally, the resonant structure includes a working area and a non-working area surrounding the working area. A first buffer structure 132 is provided between the first electrode 140 and the piezoelectric layer 120 in the non-working area. The stress value of the first buffer structure 132 is designed to be between the stress of the first electrode 140 and the piezoelectric layer 120, which can gradually alleviate the stress difference between the first electrode 140 and the piezoelectric layer 120, avoid sudden changes in stress at the interface, reduce local stress peaks, and make the stress more evenly dispersed throughout the structure, thereby reducing stress concentration. In addition, the material of the first buffer structure 132 is a flexible medium such as phosphosilicate glass (PSG), undoped silicate glass (USG) or borophosphosilicate glass (BPSG), which can absorb and release part of the stress, reduce the stress transfer to adjacent film layers, and reduce the stress difference. In addition, the thermal expansion coefficient of the first buffer structure 132 is between the first electrode 140 and the piezoelectric layer 120, which can alleviate the thermal stress caused by temperature changes and further reduce the stress difference.

[0036] In one embodiment of the present application, the process of etching the first electrode layer may be a dry etching process or a wet etching process, but the present application does not limit this and it depends on the specific circumstances.

[0037] like Figure 4 As shown, a sacrificial layer 150 is formed in the working area of ​​the first electrode 140 away from the piezoelectric layer 120, and the sacrificial layer 150 covers a part of the exposed surface of the piezoelectric layer 120 and a part of the surface of the first electrode 140. Optionally, the material of the sacrificial layer 150 can be SiO2, PSG, USG, a-Si or photoresist, etc.; the formation process of the sacrificial layer 150 can be PVD, CVD or spin coating, etc.

[0038] like Figure 5 As shown, a fence layer 160 is deposited on the sacrificial layer 150 , wherein the fence layer 160 covers the second buffer structure 131 , the exposed surface of the piezoelectric layer 120 , the surface of the sacrificial layer 150 , and the exposed surface of the first electrode 140 .

[0039] Specifically, a second buffer structure 131 is provided between the fence layer 160 and the piezoelectric layer 120 in the non-working area. The stress value of the second buffer structure 131 is designed to be between the stress of the fence layer 160 and the piezoelectric layer 120, which can gradually alleviate the stress difference between the fence layer 160 and the piezoelectric layer 120, avoid sudden changes in stress at the interface, reduce local stress peaks, and make the stress more evenly dispersed throughout the structure, thereby reducing stress concentration. In addition, the material of the second buffer structure 131 is a flexible medium such as phosphosilicate glass (PSG), undoped silicate glass (USG) or borophosphosilicate glass (BPSG), which can absorb and release part of the stress, reduce the stress transfer to adjacent membrane layers, and reduce stress differences. In addition, the thermal expansion coefficient of the second buffer structure 131 is between the fence layer 160 and the piezoelectric layer 120, which can alleviate the thermal stress caused by temperature changes and further reduce stress differences.

[0040] Optionally, the uniformity of the fence layer 160 is required to be <5%.

[0041] Alternatively, if Figure 5 As shown, in the non-working area, the surface of the first electrode 140 away from the first substrate 100 has a protruding structure, and the fence layer 160 covers the protruding structure and a portion of the flat surface of the first electrode 140 away from the first substrate 100.

[0042] like Figure 6 As shown, a second substrate 170 serving as a carrier is bonded to a side of the fence layer 160 away from the piezoelectric layer 120 .

[0043] like Figure 7 As shown, the wafer composed of each structure obtained by the above manufacturing is turned over, and the first substrate 100 is removed from the side of the first substrate 100 away from the second substrate 170. Optionally, the removal process of the first substrate 100 can be grinding (grinding) or chemical mechanical polishing (CMP), which is not limited in this application and depends on the specific situation. Then, part of the second electrode layer 110 is etched to expose part of the surface of the piezoelectric layer 120 to form the second electrode 111.

[0044] Optionally, the etching process of the second electrode layer 110 may be wet etching or dry etching. During the etching process of the second electrode layer 110 , the damage to the buffer layer is less than 10 nm.

[0045] Continue as Figure 7As shown, the sacrificial layer 150 is released, and a resonant cavity 1501 is formed below the BAW resonator. Optionally, in one embodiment of the present application, the operation of releasing the sacrificial layer 150 includes: using a liquid phase etching method or a gas phase etching method to release the sacrificial layer 150, and forming a resonant cavity 1501 below the BAW resonator. The damage to the substrate during the etching process of the sacrificial layer 150 is less than 10nm.

[0046] Specifically, in one embodiment of the present application, the sacrificial layer 150 is released by liquid phase etching or gas phase etching, and the resonant cavity 1501 is formed below the BAW resonator, including: Using a liquid etching solution such as a hydrofluoric acid solution (HF) or a buffered oxide etchant (BOE) to etch a preset area of ​​the sacrificial layer to form a resonant cavity 1501 below the BAW resonator; Alternatively, the sacrificial layer 150 is etched using gas such as hydrogen fluoride (HF) or xenon difluoride (XeF 2 ) to form a resonant cavity 1501 below the BAW resonator.

[0047] In addition, the embodiments of the present application also provide a bulk acoustic wave filter with improved film layer bonding force manufactured by using the manufacturing method provided by any of the above embodiments.

[0048] like Figure 7 As shown, the bulk acoustic wave filter with improved membrane layer bonding force provided in an embodiment of the present application includes: a second substrate 170 and a resonant structure, wherein the resonant structure is arranged on the second substrate 170, and the resonant structure includes a working area and a non-working area surrounding the working area, and a buffer structure is provided between the piezoelectric layer 120 of the resonant structure and the adjacent membrane layer in the non-working area.

[0049] Optionally, the resonant structure includes a first electrode 140, a second electrode 111 and a fence layer 160, wherein the first electrode 140 is arranged on a side of the piezoelectric layer 120 close to the second substrate 170 and exposes at least a portion of the surface of the piezoelectric layer 120, and a first buffer structure 132 is provided between the first electrode 140 and the piezoelectric layer 120 in the non-working area; the second electrode 111 is provided on a side of the piezoelectric layer 120 away from the second substrate 170; and the fence layer 160 is provided between the first electrode 140 and the second substrate 170 and covers a portion of the surface of the first electrode 140 close to the second substrate 170 and a portion of the exposed surface of the piezoelectric layer 120, and a second buffer structure 131 is provided between the piezoelectric layer 120 and the fence layer 160 in the non-working area.

[0050] Optionally, in the non-working area, a surface of the first electrode 140 close to the second substrate 170 has a protruding structure, and the fence layer 160 covers the protruding structure and a portion of the flat surface of the first electrode 140 close to the second substrate 170 .

[0051] It should be noted that, since the detailed structure of the BAW filter has been described in detail in the method for manufacturing the BAW filter, it will not be described in detail here.

[0052] In summary, in the bulk acoustic wave filter and its manufacturing method for improving the bonding force of the film layer proposed in the present application, the bulk acoustic wave filter includes a substrate and a resonant structure, wherein the resonant structure is arranged on the substrate, the resonant structure includes a working area and a non-working area surrounding the working area, and in the non-working area, there is a buffer structure between the piezoelectric layer of the resonant structure and the adjacent film layer. By introducing the buffer structure in the non-working area, the stress distribution between the piezoelectric layer and the adjacent film layer is made more uniform, rather than concentrated in certain specific areas (such as the interface), avoiding the occurrence of stress peaks (i.e., stress concentration) in local areas, reducing the stress difference between the piezoelectric layer and the adjacent film layer, and being able to effectively avoid separation or wafer warping between the piezoelectric layer and the adjacent film, thereby enhancing the firmness of the device and improving the reliability of the device. This solves the technical problem that the bulk acoustic wave filter in the prior art has the risk of device structure damage and reduced reliability due to the stress difference between the piezoelectric layer and the adjacent film.

[0053] Embodiment 2 The invention scheme in this embodiment is basically the same as that in the first embodiment, except that in the invention scheme, Figure 8 As shown, the BAW filter also includes a first protective structure 182 and a second protective structure 181; wherein the first protective structure 182 is arranged on a side surface of the first electrode 140 close to the second substrate 170 and covers the protruding structure; and the second protective structure 181 is arranged on an exposed surface of the piezoelectric layer 120 close to the second substrate 170 and covers the second buffer structure 131.

[0054] Specifically, in the first embodiment Figure 3 On the basis of the first electrode 140, a first protective structure 182 is deposited, and a second protective structure 181 is deposited on the exposed surface of the piezoelectric layer 120 and the second buffer structure 131. The first protective structure 182 and the second protective structure 181 protect the first electrode 140 and the second buffer structure 131 to prevent damage in subsequent processes.

[0055] Next, the sacrificial layer 150, the fence layer 160 and the second substrate 170 are deposited according to the process flow of the first embodiment, and then the wafer composed of each structure is turned over, and the first substrate 100 is removed from the side of the first substrate 100 away from the second substrate 170. The second electrode layer 110 is partially etched to expose the surface of the piezoelectric layer 120 to form the second electrode 111, and finally the sacrificial layer 150 is released, so as to obtain the following Figure 8 The bulk acoustic wave filter.

[0056] Embodiment 3 The invention scheme in this embodiment is basically the same as that in the first embodiment, except that in the invention scheme, Fig. 9 As shown, in the non-working area, a first buffer structure is not arranged between the first electrode 140 and the piezoelectric layer 120, but a second buffer structure 131 is formed between the fence layer 160 and the piezoelectric layer 120 in the non-working area, and a third buffer structure 133 is formed between the first electrode 140 and the fence layer 160 in the non-working area.

[0057] Specifically, in the first embodiment Figure 1 On the basis of the first substrate 100, the second buffer structure 131 is formed only in the non-working area of ​​the surface of the piezoelectric layer 120 away from the first substrate 100. Then, the first electrode layer is made on the piezoelectric layer 120 according to the process flow of the first embodiment, and the first electrode layer is etched to obtain the first electrode 140. It should be noted that the first electrode 140 of this embodiment does not have a convex structure. Afterwards, a third buffer structure 133 is formed on the surface of the first electrode 140 away from the piezoelectric layer 120 in the non-working area.

[0058] Among them, the stress value of the third buffer structure 133 is designed to be between the stress of the fence layer 160 and the first electrode 140, which can gradually alleviate the stress difference between the fence layer 160 and the first electrode 140, avoid sudden changes in stress at the interface, reduce local stress peaks, and make stress more evenly dispersed throughout the structure, thereby reducing stress concentration. The material of the third buffer structure 133 is a flexible medium such as phosphosilicate glass (PSG), undoped silicate glass (USG) or borophosphosilicate glass (BPSG), which can absorb and release part of the stress, reduce stress transfer to adjacent film layers, and reduce stress differences. In addition, the thermal expansion coefficient of the third buffer structure 133 is between the fence layer 160 and the first electrode 140, which can alleviate thermal stress caused by temperature changes and further reduce stress differences.

[0059] Next, the sacrificial layer 150, the fence layer 160 and the second substrate 170 are continuously deposited on the piezoelectric layer 120 according to the process flow of the first embodiment, and then the wafer composed of each structure is flipped, and the first substrate 100 is removed from the side of the first substrate 100 away from the second substrate 170. The second electrode layer 110 is partially etched to expose the surface of the piezoelectric layer 120 to form the second electrode 111, and finally the sacrificial layer 150 is released, so as to obtain the following Fig. 9 The bulk acoustic wave filter.

[0060] Embodiment 4 The invention scheme in this embodiment is basically the same as that in the third embodiment, except that in the invention scheme, Fig.10 As shown, the BAW filter also includes a first protective structure 182 and a second protective structure 181; wherein the first protective structure 182 is arranged on a side surface of the first electrode 140 close to the second substrate 170 and covers the third buffer structure 133; and the second protective structure 181 is arranged on an exposed surface of the piezoelectric layer 120 close to the second substrate 170 and covers the second buffer structure 131.

[0061] Specifically, after manufacturing the first substrate 100, the piezoelectric layer 120, the second buffer structure 131, the first electrode 140 and the third buffer structure 133 according to the process of the third embodiment, the first protective structure 182 is deposited on the side surface of the first electrode 140 away from the piezoelectric layer 120 and the third buffer structure 133, and the second protective structure 181 is deposited on the exposed surface of the piezoelectric layer 120 and the second buffer structure 131. The first protective structure 182 and the second protective structure 181 protect the first electrode 140, the third buffer structure 133 and the second buffer structure 131 to prevent them from being damaged in subsequent processes.

[0062] Next, the sacrificial layer 150, the fence layer 160 and the second substrate 170 are deposited according to the process flow of the third embodiment, and then the wafer composed of each structure is turned over, and the first substrate 100 is removed from the side of the first substrate 100 away from the second substrate 170. The second electrode layer 110 is partially etched to expose the surface of the piezoelectric layer 120 to form the second electrode 111, and finally the sacrificial layer 150 is released, so as to obtain the following Fig.10 The bulk acoustic wave filter.

[0063] Embodiment 5 The invention scheme in this embodiment is basically the same as that in the third embodiment, except that in the invention scheme, Fig.11As shown, not only is a second buffer structure 131 formed between the fence layer 160 and the piezoelectric layer 120 in the non-working area, a third buffer structure 133 is formed between the first electrode 140 and the fence layer 160 in the non-working area, but also a first buffer structure 132 is formed between the first electrode 140 and the piezoelectric layer 120 in the non-working area.

[0064] Specifically, in Figure 1 On the basis of the first buffer structure 132 and the second buffer structure 131 are formed in the non-working area of ​​the surface of the piezoelectric layer 120 away from the first substrate 100. Then, a first electrode layer is made on the piezoelectric layer 120 according to the process flow of Example 3, and the first electrode layer is etched to obtain a first electrode 140. It should be noted that the first electrode 140 of this embodiment does not have a protruding structure either. Afterwards, a third buffer structure 133 is formed on the surface of the first electrode 140 away from the piezoelectric layer 120 in the non-working area.

[0065] Among them, the stress value of the third buffer structure 133 is designed to be between the stress of the fence layer 160 and the first electrode 140, which can gradually alleviate the stress difference between the fence layer 160 and the first electrode 140, avoid sudden changes in stress at the interface, reduce local stress peaks, and make stress more evenly dispersed throughout the structure, thereby reducing stress concentration. The material of the third buffer structure 133 is a flexible medium such as phosphosilicate glass (PSG), undoped silicate glass (USG) or borophosphosilicate glass (BPSG), which can absorb and release part of the stress, reduce stress transfer to adjacent film layers, and reduce stress differences. In addition, the thermal expansion coefficient of the third buffer structure 133 is between the fence layer 160 and the first electrode 140, which can alleviate thermal stress caused by temperature changes and further reduce stress differences.

[0066] Next, the sacrificial layer 150, the fence layer 160 and the second substrate 170 are continuously deposited on the piezoelectric layer 120 according to the process flow of the third embodiment, and then the wafer composed of each structure is flipped, and the first substrate 100 is removed from the side of the first substrate 100 away from the second substrate 170. The second electrode layer 110 is partially etched to expose the surface of the piezoelectric layer 120 to form the second electrode 111, and finally the sacrificial layer 150 is released, so as to obtain the following Fig.11 The bulk acoustic wave filter.

[0067] Embodiment 6 The invention scheme in this embodiment is basically the same as that in the fifth embodiment, except that in the invention scheme, Fig.12As shown, the BAW filter also includes a first protective structure 182 and a second protective structure 181; wherein the first protective structure 182 is arranged on a side surface of the first electrode 140 close to the second substrate 170 and covers the third buffer structure 133; and the second protective structure 181 is arranged on an exposed surface of the piezoelectric layer 120 close to the second substrate 170 and covers the second buffer structure 131.

[0068] Specifically, after manufacturing the first substrate 100, the piezoelectric layer 120, the first buffer structure 132, the second buffer structure 131, the first electrode 140 and the third buffer structure 133 according to the process of the fifth embodiment, the first protective structure 182 is deposited on the side surface of the first electrode 140 away from the piezoelectric layer 120 and the third buffer structure 133, and the second protective structure 181 is deposited on the exposed surface of the piezoelectric layer 120 and the second buffer structure 131. The first protective structure 182 and the second protective structure 181 protect the first electrode 140, the third buffer structure 133 and the second buffer structure 131 to prevent them from being damaged in subsequent processes.

[0069] Next, the sacrificial layer 150, the fence layer 160 and the second substrate 170 are deposited according to the process flow of the fifth embodiment, and then the wafer composed of each structure is turned over, and the first substrate 100 is removed from the side of the first substrate 100 away from the second substrate 170. The second electrode layer 110 is partially etched to expose the surface of the piezoelectric layer 120 to form the second electrode 111, and finally the sacrificial layer 150 is released, so as to obtain the following Fig.12 The bulk acoustic wave filter.

[0070] In summary, in the bulk acoustic wave filter and its manufacturing method for improving the bonding force of the film layer proposed in the present application, the bulk acoustic wave filter includes a substrate and a resonant structure, wherein the resonant structure is arranged on the substrate, the resonant structure includes a working area and a non-working area surrounding the working area, and a buffer structure is provided between the piezoelectric layer of the resonant structure and the adjacent film layer in the non-working area. By introducing the buffer structure in the non-working area, the stress distribution between the piezoelectric layer and the adjacent film layer is made more uniform, rather than concentrated in certain specific areas (such as the interface), so as to avoid the occurrence of stress peaks (i.e., stress concentration) in local areas, reduce the stress difference between the piezoelectric layer and the adjacent film layer, and effectively avoid separation or wafer warping between the piezoelectric layer and the adjacent film, thereby enhancing the firmness of the device and improving the reliability of the device. This solves the technical problem that the bulk acoustic wave filter in the prior art has the risk of device structure damage and reduced reliability due to the stress difference between the piezoelectric layer and the adjacent film.

[0071] The various parts in this manual are described in a progressive manner, and each part focuses on the differences from other parts. The same or similar parts between the various parts can be referenced to each other.

[0072] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A bulk acoustic wave filter with improved film bonding strength, characterized in that: include: A substrate and a resonant structure, wherein the resonant structure is arranged on the substrate, and the resonant structure comprises a working area and a non-working area surrounding the working area, and a buffer structure is provided between the piezoelectric layer of the resonant structure and an adjacent membrane layer in the non-working area.

2. The bulk acoustic wave filter according to claim 1, characterized in that The resonant structure includes a first electrode, a second electrode and a fence layer, wherein The first electrode is disposed on a side of the piezoelectric layer close to the substrate and exposes at least a portion of the surface of the piezoelectric layer, and a first buffer structure is provided between the first electrode and the piezoelectric layer in the non-working area; The second electrode is arranged on a side of the piezoelectric layer away from the substrate; as well as The fence layer is arranged between the first electrode and the substrate, and covers a portion of the surface of the first electrode close to the substrate and a portion of the exposed surface of the piezoelectric layer. A second buffer structure is provided between the piezoelectric layer and the fence layer in the non-working area.

3. The bulk acoustic wave filter according to claim 2, characterized in that In the non-working area, a surface of the first electrode close to the substrate has a convex structure, and the fence layer covers the convex structure and a portion of the flat surface of the first electrode close to the substrate.

4. The bulk acoustic wave filter according to claim 3, characterized in that The BAW filter further comprises a first protection structure and a second protection structure; wherein The first protection structure is disposed on a surface of the first electrode close to the substrate and covers the protruding structure; and The second protection structure is arranged on an exposed surface of the piezoelectric layer close to the substrate and covers the second buffer structure.

5. The bulk acoustic wave filter according to claim 1, wherein: The resonant structure includes a first electrode, a second electrode and a fence layer, wherein The first electrode is disposed on a side of the piezoelectric layer close to the substrate and exposes at least a portion of the surface of the piezoelectric layer; The second electrode is arranged on a side of the piezoelectric layer away from the substrate; as well as The fence layer is arranged between the first electrode and the substrate, and covers a portion of the surface of the first electrode close to the substrate and a portion of the exposed surface of the piezoelectric layer. In the non-working area, a second buffer structure is provided between the piezoelectric layer and the fence layer, and a third buffer structure is provided between the first electrode and the fence layer.

6. The bulk acoustic wave filter according to claim 1, wherein: The resonant structure includes a first electrode, a second electrode and a fence layer, wherein The first electrode is disposed on a side of the piezoelectric layer close to the substrate and exposes at least a portion of the surface of the piezoelectric layer, and a first buffer structure is provided between the first electrode and the piezoelectric layer in the non-working area; The second electrode is arranged on a side of the piezoelectric layer away from the substrate; as well as The fence layer is arranged between the first electrode and the substrate, and covers a portion of the surface of the first electrode close to the substrate and a portion of the exposed surface of the piezoelectric layer. In the non-working area, a second buffer structure is provided between the piezoelectric layer and the fence layer, and a third buffer structure is provided between the first electrode and the fence layer.

7. The bulk acoustic wave filter according to claim 5 or 6, characterized in that: The resonant structure also includes a first protection structure and a second protection structure; wherein The first protection structure is disposed on a surface of the first electrode close to the substrate and covers the third buffer structure; and The second protection structure is arranged on an exposed surface of the piezoelectric layer close to the substrate and covers the second buffer structure.

8. The bulk acoustic wave filter according to claim 1, wherein: The material of the buffer structure is phosphosilicate glass, undoped silicate glass or borophosphosilicate glass.

9. The bulk acoustic wave filter according to claim 1, wherein: The film thickness of the buffer structure is 50-500nm.

10. A method for manufacturing a bulk acoustic wave filter with improved film layer bonding strength, characterized in that: include: A substrate and a resonant structure are manufactured, wherein the resonant structure is arranged on the substrate, and the resonant structure comprises a working area and a non-working area surrounding the working area, and a buffer structure is provided between the piezoelectric layer of the resonant structure and an adjacent membrane layer in the non-working area.

11. The manufacturing method according to claim 10, characterized in that: The process of making a resonant structure includes: making a first electrode, a second electrode and a fence layer, wherein the first electrode is arranged on a side of the piezoelectric layer close to the substrate and exposes at least a portion of the surface of the piezoelectric layer, and a first buffer structure is provided between the first electrode and the piezoelectric layer in the non-working area; the second electrode is arranged on a side of the piezoelectric layer away from the substrate; and the fence layer is arranged between the first electrode and the substrate and covers a portion of the surface of the first electrode close to the substrate and a portion of the exposed surface of the piezoelectric layer, and a second buffer structure is provided between the piezoelectric layer and the fence layer in the non-working area; a convex structure is provided on a side of the first electrode close to the substrate in the non-working area, and the fence layer covers the convex structure and a portion of the flat surface of the first electrode close to the substrate; and The manufacturing method also includes: manufacturing a first protection structure and a second protection structure; wherein the first protection structure is arranged on a surface of the first electrode close to the substrate and covers the protruding structure; and the second protection structure is arranged on an exposed surface of the piezoelectric layer close to the substrate and covers the second buffer structure.

12. The manufacturing method according to claim 10, characterized in that: The process of making a resonant structure includes: making a first electrode, a second electrode and a fence layer, wherein the first electrode is arranged on a side of the piezoelectric layer close to the substrate and exposes at least part of the surface of the piezoelectric layer; the second electrode is arranged on a side of the piezoelectric layer away from the substrate; and the fence layer is arranged between the first electrode and the substrate, and covers part of the surface of the first electrode close to the substrate and part of the exposed surface of the piezoelectric layer, and in the non-working area, there is a second buffer structure between the piezoelectric layer and the fence layer and a third buffer structure between the first electrode and the fence layer; or The process of making a resonant structure includes: making a first electrode, a second electrode and a fence layer, wherein the first electrode is arranged on a side of the piezoelectric layer close to the substrate and exposes at least a portion of the surface of the piezoelectric layer, and a first buffer structure is provided between the first electrode and the piezoelectric layer in the non-working area; the second electrode is arranged on a side of the piezoelectric layer away from the substrate; and the fence layer is arranged between the first electrode and the substrate and covers a portion of the surface of the first electrode close to the substrate and a portion of the exposed surface of the piezoelectric layer, and a second buffer structure is provided between the piezoelectric layer and the fence layer in the non-working area, and a third buffer structure is provided between the first electrode and the fence layer.

13. The manufacturing method according to claim 12, characterized in that: The manufacturing method also includes: manufacturing a first protection structure and a second protection structure; wherein the first protection structure is arranged on a surface of the first electrode close to the substrate and covers the third buffer structure; and the second protection structure is arranged on an exposed surface of the piezoelectric layer close to the substrate and covers the second buffer structure.

14. The manufacturing method according to claim 10, characterized in that: The material of the buffer structure is phosphosilicate glass, undoped silicate glass or borophosphosilicate glass; the film thickness of the buffer structure is 50-500nm.

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