Bulk acoustic wave resonators, filters, communication devices and terminals

Abstract

The embodiment of the present application provides a bulk acoustic resonator, a filter, a communication device and a terminal, wherein the bulk acoustic resonator comprises: a first electrode, a second electrode and a piezoelectric layer with an arc-shaped surface; the arc-shaped surface is formed based on a target pre-stress, which is determined according to a stress generated in a process and a film layer fracture threshold; a closed first acoustic mirror cavity is formed between the first electrode, an exposed surface of the piezoelectric layer, a first supporting layer and a first substrate; a closed second acoustic mirror cavity is formed between the second electrode, an exposed surface of the piezoelectric layer, a second supporting layer and a second substrate; and the arc-shaped surface is located inside the second acoustic mirror cavity and the first acoustic mirror cavity. The bulk acoustic resonator provided by the embodiment of the present application can reduce the actual footprint of the bulk acoustic resonator.

Description

Technical Field

[0001] This invention relates to the field of resonator technology, specifically to a bulk acoustic resonator, filter, communication device, and terminal. Background Technology

[0002] Bulk acoustic wave (BAW) resonators are devices used to convert electrical energy into mechanical energy, playing a crucial role in radio frequency (RF) communication and sensing. The actual footprint of a BAW resonator is one of its core design specifications, directly impacting device integration density, manufacturing cost, performance limits, and application adaptability. Therefore, providing technical solutions to reduce the actual footprint of BAW resonators has become a pressing technical challenge. Summary of the Invention

[0003] In view of this, embodiments of the present invention provide a bulk acoustic resonator, a filter, a communication device, and a terminal to reduce the actual footprint of the bulk acoustic resonator.

[0004] This invention provides a bulk acoustic resonator, comprising: a first electrode, a second electrode, and a piezoelectric layer; The surfaces of the first electrode, the second electrode, and the piezoelectric layer all include arc-shaped surfaces, which are formed based on target prestress; the target prestress is determined based on the stress generated during the process and the film fracture threshold. A closed first acoustic mirror cavity is formed between the first electrode, the exposed surface of the piezoelectric layer, the first support layer located on the first electrode, and the first substrate bonded to the first electrode through the first support layer. A closed second acoustic mirror cavity is formed between the second electrode, the exposed surface of the piezoelectric layer, the second support layer located on the second electrode, and the second substrate bonded to the second electrode through the second support layer; The arc-shaped surface is located inside the second acoustic mirror cavity and the first acoustic mirror cavity.

[0005] Optionally, the first acoustic mirror cavity and the second acoustic mirror cavity are independent cavities, and no vent hole penetrates the first acoustic mirror cavity and the second acoustic mirror cavity. The overall profile of the bulk acoustic resonator is pentagonal; there are no additional openings or protrusions at the edges and corners of the pentagonal profile for sacrificial layer release.

[0006] Optionally, the arc-shaped surface formation area is: the effective area of ​​the bulk acoustic resonator and an area extending a predetermined distance from the outer edge of the effective area to the side where the first electrode and the second electrode do not overlap; the effective area is located in the central part of the overall structure of the bulk acoustic resonator, and is the area where the first acoustic mirror cavity and the second acoustic mirror cavity, the first electrode, the piezoelectric layer and the second electrode overlap.

[0007] Optionally, the first electrode has a top surface and a bottom surface opposite to each other; the arcuate surface of the first electrode includes an arcuate surface on the top surface of the first electrode and an arcuate surface on the bottom surface of the first electrode, and the arcuate direction of the arcuate surface on the top surface of the first electrode is the same as the arcuate direction of the arcuate surface on the bottom surface of the first electrode. The arc-shaped surface area formed by the first electrode top surface includes: the effective area and an area extending a predetermined distance from the outer edge of the effective area to the side where the first electrode and the second electrode do not overlap. The region where the arcuate surface of the bottom surface of the first electrode is formed is the same as the region where the arcuate surface of the top surface of the first electrode is formed. The arc-shaped surface of the top surface of the piezoelectric layer has the same arc direction as the arc-shaped surface of the bottom surface of the first electrode.

[0008] Optionally, the second electrode has a top surface and a bottom surface opposite each other; the arcuate surface of the second electrode includes an arcuate surface on the top surface and an arcuate surface on the bottom surface, and the arcuate direction of the arcuate surface on the top surface and the arcuate direction of the arcuate surface on the bottom surface are the same. The arc-shaped surface area formed by the second electrode top surface includes: the effective area and an area extending a predetermined distance from the outer edge of the effective area to the side where the second electrode and the first electrode do not overlap. The arcuate surface of the bottom surface of the piezoelectric layer has the same arcuate direction as the arcuate surface of the top surface of the second electrode; the bottom surface of the piezoelectric layer is relative to the top surface of the piezoelectric layer. The area where the arcuate surface of the bottom surface of the second electrode is formed is the same as the area where the arcuate surface of the top surface of the second electrode is formed.

[0009] Optionally, the curvature direction of the arcuate surface includes a first direction toward the first substrate and a second direction toward the second substrate; the stress generated during the process is a pre-stress generated during the fabrication of the bulk acoustic wave resonator, and the target pre-stress is used to enable the first electrode, the second electrode, and the piezoelectric layer to cope with the stress generated during the process, and the value of the target pre-stress is within the range of the film fracture threshold.

[0010] Optionally, the surfaces of the first electrode, the second electrode, and the piezoelectric layer further include: a flat surface; under the target prestress, the maximum vertical distance from the arcuate surface to the plane containing the flat surface is constrained by the stress generated during the process and the film fracture threshold. The flat surface is a stepless surface formed using a non-etching cavity process; and the vertical distance from any position on the upper surface of the flat surface of the piezoelectric layer to the corresponding position on the upper surface of the flat surface of the first electrode is fixed; the vertical distance from any position on the lower surface of the flat surface of the piezoelectric layer to the corresponding position on the lower surface of the flat surface of the second electrode is fixed.

[0011] Optionally, the bulk acoustic resonator further includes: a first electrode protection layer located on the first electrode and / or a second electrode protection layer located on the second electrode, and a piezoelectric layer protection layer located on the piezoelectric layer; The surface of the first electrode protective layer includes the arc-shaped surface; The surface of the second electrode protective layer includes the arc-shaped surface; The surface of the piezoelectric protective layer includes the arc-shaped surface.

[0012] Optionally, there is no stacked structure outside the regions where the first acoustic mirror cavity and the second acoustic mirror cavity are located; the stacked structure includes a structure formed by the overlapping of a first electrode, a piezoelectric layer, a second electrode, and a second support layer.

[0013] Optionally, the bulk acoustic resonator further includes: a through-hole; The through-hole is located on the piezoelectric layer outside the first acoustic mirror cavity and the second acoustic mirror cavity.

[0014] Optionally, the bulk acoustic resonator further includes: a boundary structure; within the effective region, located at the edge of the effective region, the boundary structure is disposed on the surface of the first electrode, and / or, disposed on the surface of the second electrode; The plane of the boundary structure forms a height difference with the plane in the effective area where the boundary structure is not formed in the direction perpendicular to the plane of the piezoelectric layer; the plane of the boundary structure is higher than the plane where the boundary structure is not formed, or the plane of the boundary structure is lower than the plane where the boundary structure is not formed.

[0015] This invention also provides a filter comprising: a plurality of bulk acoustic wave resonators, wherein at least one bulk acoustic wave resonator is a bulk acoustic wave resonator as described in any of the preceding embodiments.

[0016] This invention also provides a communication device, including the filter described in the foregoing embodiments.

[0017] This invention also provides a terminal, including the filter described in the foregoing embodiments.

[0018] The bulk acoustic resonator provided in this embodiment of the invention includes: a first electrode, a second electrode, and a piezoelectric layer; the surfaces of the first electrode, the second electrode, and the piezoelectric layer all include arc-shaped surfaces, which are formed based on a target prestress; the target prestress is determined according to the stress generated during the process and the film fracture threshold; a closed first acoustic mirror cavity is formed between the first electrode, the exposed surface of the piezoelectric layer, a first support layer located on the first electrode, and a first substrate bonded to the first electrode through the first support layer; a closed second acoustic mirror cavity is formed between the second electrode, the exposed surface of the piezoelectric layer, a second support layer located on the second electrode, and a second substrate bonded to the second electrode through the second support layer; the arc-shaped surface is located inside the second acoustic mirror cavity and the first acoustic mirror cavity.

[0019] As can be seen, the bulk acoustic wave resonator provided in this embodiment of the invention has arc-shaped surfaces on the piezoelectric layer, the first electrode, and the second electrode. The target prestress on which the arc-shaped surface is formed is determined based on the stress generated during the process and the membrane fracture threshold. Therefore, the arc-shaped surface formed under this target prestress can effectively support the stress generated during the process. Based on this, the bulk acoustic wave resonator provided in this embodiment of the invention can avoid the method of opening vent holes through the upper and lower cavities on the piezoelectric layer to balance the air pressure to cope with the stress generated during the process, thereby forming a closed first acoustic reflector cavity and a closed second acoustic reflector cavity. Compared with the structural characteristics of bulk acoustic wave resonators formed in related technologies, the original top acoustic reflector and the original bottom acoustic reflector in related technologies are interconnected and not closed. However, in the bulk acoustic wave resonator provided in this embodiment of the invention, since the surfaces of the first electrode, the second electrode, and the piezoelectric layer include arc-shaped surfaces, the arc-shaped surfaces can ensure that the first electrode, the second electrode, and the piezoelectric layer can cope with the stress generated during the process, while the curvature of the arc-shaped surface will not cause the membrane to fracture. Therefore, it is not necessary to open vent holes on the piezoelectric layer. The design of vent holes indirectly increases the area of ​​the auxiliary region, thereby increasing the actual footprint of the bulk acoustic wave resonator. In the bulk acoustic wave resonator provided in this embodiment of the invention, since vent holes are not opened on the piezoelectric layer, the area for setting vent holes can be saved. Therefore, the technical solution provided in this embodiment of the invention can reduce the actual footprint of the bulk acoustic wave resonator. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of a bulk acoustic resonator. Figure 2 This is another schematic diagram of a bulk acoustic resonator; Figure 3 yes Figure 1 A schematic diagram showing the stress simulation results of the bulk acoustic resonator is shown. Figure 4 yes Figure 2 A schematic diagram showing the stress simulation results of the bulk acoustic resonator is shown. Figure 5 yes Figure 1 A schematic diagram of the release channel and release hole in the solid acoustic resonator shown; Figure 6 yes Figure 2Another schematic diagram of a solid acoustic resonator is shown. Figure 7 yes Figure 6 The diagram shows the AA' cross-section of the solid acoustic resonator. Figure 8 This is a schematic diagram of the structure of a bulk acoustic resonator provided in an embodiment of the present invention; Figure 9 yes Figure 8 The diagram shows the LL' cross-sectional view of the solid acoustic resonator. Figure 10 This is a schematic flowchart of a method for forming a bulk acoustic resonator provided in an embodiment of the present invention; Figure 11 This is another schematic flowchart of the method for forming a bulk acoustic resonator provided in an embodiment of the present invention; Figure 12 This is a schematic diagram of the first structure obtained by the method for forming a bulk acoustic resonator provided in an embodiment of the present invention; Figure 13 This is a schematic diagram of the second structure obtained by the method for forming a bulk acoustic resonator provided in an embodiment of the present invention; Figure 14 This is a schematic diagram of the third structure obtained by the method for forming a bulk acoustic resonator provided in an embodiment of the present invention; Figure 15 This is a schematic diagram of the fourth structure obtained by the method for forming a bulk acoustic resonator provided in the embodiments of the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] With the continuous development of radio frequency (RF) front-ends, integration and miniaturization are the development trends. Filters enable frequency control and are required for both frequency transmission and reception. Filters are the main components of the RF front-end; therefore, miniaturization and integration of filters are extremely important.

[0024] Among them, BAW (Bulk Acoustic Wave) resonators, with their high power, high bandwidth, and excellent roll-off performance, can well meet the current needs of RF performance. Therefore, BAW resonators, as one of the core components of RF front-ends, are receiving increasing attention. In particular, compared with SAW (Surface Acoustic Wave) resonators, BAW resonators have a significant advantage in terms of high power. This is because BAW resonators use the longitudinal wave propagation mode of bulk acoustic waves and can utilize the excellent piezoelectric properties of AlN (aluminum nitride) material to better convert acoustic wave energy. Currently, BAW resonators are divided into FBAR (Film Bulk Acoustic Resonator) with a cavity structure and SMR (Solidly Mounted Resonator) with a Bragg reflector layer. The cavity structure of FBAR has a higher acoustic impedance difference, which can reflect more energy into the resonator interior. Therefore, the application of FBAR with a cavity structure is increasing.

[0025] Typically, bulk acoustic wave resonators (such as FBARs with cavity structures) are characterized by the following steps: etching a cavity into a substrate, depositing a piezoelectric layer and a top electrode on the etched bottom electrode, and finally releasing the material within the cavity to create the cavity. Please refer to [reference needed]. Figure 1 , Figure 1 This is a schematic diagram of a bulk acoustic resonator. like Figure 1 As shown, the bulk acoustic resonator includes an original support layer 01, an original bottom electrode 02 located above the original support layer 01, an original piezoelectric layer 03 located above the original bottom electrode 02, an original top electrode 04 located above the original piezoelectric layer 03, and an original frame structure 05 located above the original top electrode 04.

[0026] Figure 1 The bulk acoustic wave resonator shown is formed by etching a cavity on a substrate, filling the cavity with a sacrificial layer material, forming a primary bottom electrode 02 on the substrate with the sacrificial layer material; then etching the primary bottom electrode 02, depositing a primary piezoelectric layer 03 and a primary top electrode 04 on the primary bottom electrode 02, and finally releasing the sacrificial layer material in the cavity to form a primary support layer 01.

[0027] As you can see, Figure 1 The bulk acoustic resonator shown requires etching of the original bottom electrode 02. When forming the original piezoelectric layer 03 on the original bottom electrode 02, the piezoelectric layer material needs to cross the etching interface of the original bottom electrode 02, resulting in the original piezoelectric layer 03 growing along the Z-axis (vertical direction) being discontinuous and the lattice being deformed.

[0028] Figure 1 The bulk acoustic resonator shown typically has the following drawbacks: 1. The growth quality of the original piezoelectric layer 03 is reduced, resulting in a lower Q value for the bulk acoustic resonator; 2. At the connection edge, i.e. the etching interface, there is a large step difference and a large film structure, which makes the film prone to stress concentration, which is not conducive to improving device reliability. Especially at high power, this structure is prone to film fracture. 3. Additional release channels and release holes are required to release the cavity. The number of these release channels and release holes is generally no less than 5, which will occupy a lot of area and is not conducive to reducing the chip size and cost of the bulk acoustic wave resonator.

[0029] In another related technology, the manufacturing process of the bulk acoustic resonator was adjusted; please refer to [reference needed]. Figure 2 , Figure 2 This is another schematic diagram of a bulk acoustic resonator.

[0030] like Figure 2 As shown, Figure 2 The bulk acoustic resonator includes a second support layer (bottom support layer) 112, a stepless second electrode 017 (bottom electrode) located above the second support layer 112, a flat piezoelectric layer 016 located on the stepless second electrode 017, a stepless first electrode 014 (top electrode) located on the flat piezoelectric layer 016, and a frame structure 201 located on the stepless first electrode 014.

[0031] Figure 2 In the structure shown, a bulk acoustic wave resonator is fabricated by forming a second support layer 112 on a temporary substrate (not shown) using films such as a stepless first electrode 014, a stepless second electrode 017, and a flat piezoelectric layer 016. The second substrate is then bonded to the second support layer 112. This process is not achieved by... Figure 1 The bulk acoustic resonator is obtained in the manner shown, thereby avoiding the deformation of the lattice of the flat piezoelectric layer 016 along the Z-axis.

[0032] Figure 2 The fabrication process of the structure shown involves independently setting a second support layer 112 and a first support layer (top support layer, not shown in the figure) after forming the stepless first electrode 014, the flat piezoelectric layer 016, and the stepless second electrode 017, respectively. Figure 1 The method of etching cavities on the substrate and releasing the sacrificial layer material filled in the cavities to form the original support layer 01 can improve the degree of freedom in the manufacturing process.

[0033] To better understand the variation of film stress in bulk acoustic resonators under different piezoelectric layer structures, please refer to [reference needed]. Figure 3 and Figure 4 , Figure 3 yes Figure 1 The diagram shows the stress simulation results of the bulk acoustic resonator. Figure 4 yes Figure 2 The diagram shows the stress simulation results of the bulk acoustic resonator.

[0034] like Figure 3 As shown, a test was conducted at a location with a height difference and where the original frame structure 05 was installed. The simulated maximum stress value was 6.99 GPa. Figure 4 As shown, in a bulk acoustic wave resonator with a planar structure consisting of a flat piezoelectric layer 016, a first electrode 014 without step differences, and a second electrode 017 without step differences, the maximum simulated stress at the location where the frame structure 201 is added is 3.39 GPa. Since reducing the stress value can improve the uniformity of the bulk acoustic wave resonator and significantly enhance its power, it is evident that… Figure 2 The solid acoustic resonator shown has better structural reliability.

[0035] also, Figure 1 The cavity structure in the solid acoustic resonator shown is obtained by releasing the sacrificial layer material; therefore... Figure 1 The solid acoustic resonator shown must be designed with sufficient release channels and release holes to ensure complete release during the process (the sacrificial layer material can be completely released). Please refer to [reference needed]. Figure 5 , Figure 5 yes Figure 1 The diagram shows the structure of the release channel and release hole in the solid acoustic resonator.

[0036] like Figure 5 As shown, Figure 1 The bulk acoustic wave (BAW) resonator shown is typically pentagonal in shape. It requires the complete release of the sacrificial layer material beneath the BAW resonator through a chemical reaction. To ensure a thorough reaction, at least five release channels and release holes are needed, increasing the complexity of the manufacturing process. Furthermore, to maintain the structural integrity of the BAW resonator, the release channels need to extend beyond the device area, thus occupying a certain area. The release holes at the ends of the release channels facilitate a smoother reaction, and their diameter must be larger than the width of the release channels. Therefore, the presence of release channels and holes occupies a significant area, resulting in a BAW resonator with a footprint far exceeding its effective area. Moreover, in terms of manufacturing, using through-holes instead of stepped designs for the release holes may introduce more impurities into them during subsequent processes.

[0037] In order to solve Figure 1 The structure shown has problems (such as stepped edges, increasing the actual footprint of the bulk acoustic resonator), and adopts... Figure 2 The solid acoustic resonator shown has been improved; please refer to [the documentation / reference]. Figure 6 and Figure 7 , Figure 6 yes Figure 2 Another schematic diagram of a bulk acoustic resonator is shown. Figure 7 yes Figure 6 The diagram shows the AA' cross-section of the solid acoustic resonator.

[0038] like Figure 6 and Figure 7 As shown, in the flat piezoelectric layer 016 (flat structure), in order to balance the air pressure between the upper and lower cavities (the original top acoustic reflector 019-1 and the original bottom acoustic reflector 019-2) (to avoid additional stress on the membrane layer due to air pressure imbalance, which could cause membrane layer breakage), it is necessary to balance the air pressure at the edge of the effective region S of the bulk acoustic resonator (e.g., Figure 7 At least two vents (18-1 and 18-2) are provided at the positions shown in d3 and d4.

[0039] Figure 6 and Figure 7 The fabrication process of the solid acoustic resonator shown presents the following problems: 1. A process step is required to etch out the vent holes; 2. It is necessary to increase the area of ​​the ventilation holes (e.g., Figure 6 As shown in the figure, the actual footprint of the bulk acoustic resonator will also increase accordingly.

[0040] To address the above problems, embodiments of the present invention employ a preparation method... Figure 2 Based on the fabrication process of the bulk acoustic wave resonator shown, the structure of the bulk acoustic wave resonator is adjusted to reduce its actual footprint.

[0041] Please refer to Figure 8 and Figure 9 , Figure 8 This is a schematic diagram of a bulk acoustic resonator provided in an embodiment of the present invention. Figure 9 yes Figure 8 The figure shows the LL' cross-sectional view of the solid acoustic resonator.

[0042] like Figure 8 and Figure 9 As shown, the bulk acoustic resonator includes: a first electrode 14, a second electrode 17, and a piezoelectric layer 16; The surfaces of the first electrode 14, the second electrode 17, and the piezoelectric layer 16 all include an arc-shaped surface F1, which is formed based on a target prestress; the target prestress is determined based on the stress generated during the process and the film fracture threshold. A closed first acoustic mirror cavity 191 is formed between the first electrode 14, the exposed surface of the piezoelectric layer 16, the first support layer 111 located on the first electrode 14, and the first substrate 101 bonded to the first electrode 14 through the first support layer 111. A closed second acoustic mirror cavity 192 is formed between the second electrode 17, the exposed surface of the piezoelectric layer 16, the second support layer 112 located on the second electrode 17, and the second substrate 102 bonded to the second electrode 17 through the second support layer 112. The arc-shaped surface F1 is located inside the second acoustic mirror cavity 192 and the first acoustic mirror cavity 191.

[0043] The term "film layer" as used above refers to a thin film material layer, typically ranging from nanometer to micrometer thickness, formed on a substrate or other layered structure through a deposition process, and possessing specific functions. For example, the first electrode 14, the second electrode 17, and the piezoelectric layer 16 all fall under the category of film layers.

[0044] The membrane fracture threshold refers to the critical value at which the membrane undergoes macroscopic / microscopic fracture from a continuous state.

[0045] The stress generated during the process refers to the pre-stress involved in the pre-formation of cavities (i.e., the cavity structure pre-formed on a certain substrate / film layer before bonding the second substrate and the first substrate, and then forming a closed acoustic mirror cavity through bonding and encapsulation), such as bonding stress and residual stress caused by the bonding process.

[0046] The target prestress is a controllable parameter in the process of depositing materials to form the first electrode 14, the second electrode 17 and the piezoelectric layer 16. By adjusting the value of the target prestress, the first electrode 14, the second electrode 17 and the piezoelectric layer 16 that are finally formed can have sufficient prestress, so as to balance the stress (such as tensile stress and residual stress) generated during the (preparation) process, and finally control the total stress of the film layer within a safe range (below the film layer fracture threshold and without affecting the device performance).

[0047] like Figure 6 and Figure 7 In the related technologies shown, in order to avoid the stress generated during the process from damaging the membrane, ventilation holes (18-1 and 18-2) are opened at the edge of the effective area S to balance the air pressure, thereby avoiding additional stress on the membrane and causing the membrane to break.

[0048] Based on the foregoing analysis, it is known that the arrangement of vent holes would increase the actual footprint of the bulk acoustic resonator. Therefore, in the technical solution provided by the embodiments of the present invention, vent holes are no longer used. Instead, a closed first acoustic mirror cavity 191 is formed between the first electrode 14, the exposed surface of the piezoelectric layer 16, the first support layer 111 located above the first electrode 14, and the first substrate 101 bonded to the first electrode 14 through the first support layer 111; and a closed second acoustic mirror cavity 192 is formed between the second electrode 17, the exposed surface of the piezoelectric layer 16, the second support layer 112 located below the second electrode 17, and the second substrate 102 bonded to the second electrode 17 through the second support layer 112.

[0049] like Figure 9 As shown, the first acoustic mirror cavity 191 and the second acoustic mirror cavity 192 obtained without using a vent are independent cavities, and there is no vent penetrating the first acoustic mirror cavity 191 and the second acoustic mirror cavity 192. The overall outline of the bulk acoustic resonator is pentagonal (e.g., ...). Figure 8 (As shown); there are no additional openings or protrusions at any edge or corner of the pentagonal contour for sacrificial layer release.

[0050] The additional opening or protrusion structure, for example Figure 5 The release hole and release channel are shown.

[0051] Because the bulk acoustic resonator provided in the embodiments of the present invention employs, as Figure 2 The structure shown uses wafer bonding technology to form the cavity, and no vent holes are used, resulting in a final bulk acoustic resonator with the following overall profile: Figure 8 The pentagon shown has no additional openings or protrusions for sacrificial layer release, such as release channels or release holes, at any edge or corner of its pentagonal outline, which helps to improve the Q value and frequency stability of the bulk acoustic resonator.

[0052] To prevent the film from cracking under stress and causing structural instability, the technical solution provided in this embodiment of the invention uses target prestress to form a first electrode 14, a second electrode 17, and a piezoelectric layer 16, including an arc-shaped surface F1. The arc-shaped surface F1 is used to offset the stress generated during the process. At the same time, the arc-shaped surface F1 is within the film cracking threshold range, that is, the curvature of the arc-shaped surface F1 will not cause the film to crack.

[0053] Among them, the first acoustic reflector cavity 191 and the second acoustic reflector cavity 192 are reflective structures composed of air, mainly used to reflect sound waves in the resonator.

[0054] The materials of the first support layer 111 and the second support layer 112 may be monocrystalline silicon, polycrystalline silicon, silicon oxide, silicon nitride, gallium arsenide, sapphire, quartz, silicon carbide, SOI, and organic support layers, as well as a substrate composed of one or more of the above materials.

[0055] The materials of the first substrate 101 and the second substrate 102 may be monocrystalline silicon, polycrystalline silicon, gallium arsenide, sapphire, quartz, silicon carbide, SOI, organic second substrate, etc., as well as substrates composed of one or more of the above materials.

[0056] In one embodiment, the material of the piezoelectric layer 16 may be a single-crystal piezoelectric material, a polycrystalline piezoelectric material, or a rare-earth element doped material containing a certain atomic ratio of the above materials.

[0057] Specifically, single-crystal piezoelectric materials can be selected from single-crystal aluminum nitride, single-crystal gallium nitride, single-crystal lithium niobate, single-crystal lead zirconate titanate (PZT), single-crystal potassium niobate, single-crystal quartz film, or single-crystal lithium tantalate, etc.; polycrystalline piezoelectric materials (as opposed to single-crystal, non-single-crystal materials) can be selected from polycrystalline aluminum nitride, zinc oxide, PZT, etc.; rare earth element doped materials containing a certain atomic ratio of the above materials can be, for example, doped aluminum nitride, which contains at least one rare earth element, such as scandium (Sc), yttrium (Y), magnesium (Mg), titanium (Ti), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), etc.

[0058] In one embodiment, the material of the first electrode 14 may be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium, or a composite of the above metals or an alloy thereof.

[0059] In one embodiment, the material of the second electrode 17 can be the same as that of the first electrode 14, and the material can be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium, or a composite or alloy of the above metals. However, it should be understood that the materials of the second electrode 17 (top electrode) and the first electrode 14 (bottom electrode) can also be different.

[0060] The first electrode 14 and the second electrode 17 may also include a protective layer. The embodiments of the present invention do not limit the material of the protective layer; preferably, the material of the protective layer may be aluminum nitride, silicon oxide, or a combination of one or more layers of aluminum nitride.

[0061] Furthermore, since the technical solution provided in the embodiments of the present invention adopts Figure 2 The bulk acoustic wave resonator shown is fabricated using the same manufacturing process, so there is no need to set up additional structures such as release channels and release holes, which greatly reduces the actual footprint of the bulk acoustic wave resonator.

[0062] The arc-shaped surface F1 is located inside the first acoustic reflector cavity 191 and the second acoustic reflector cavity 192, so as to protect the core functional area of ​​the bulk acoustic resonator from the stress generated during the manufacturing process and ensure the performance of the bulk acoustic resonator.

[0063] As can be seen, in the bulk acoustic resonator provided in this embodiment of the invention, the surfaces of the piezoelectric layer 16, the first electrode 14, and the second electrode 17 have an arc-shaped surface F1. The target prestress on which the arc-shaped surface F1 is based is determined according to the stress generated during the process and the film fracture threshold. Therefore, the arc-shaped surface F1 formed under this target prestress can support and cope with the stress generated during the process. Based on this, the bulk acoustic resonator provided in this embodiment of the invention can avoid the method of opening a vent hole through the upper and lower cavities on the piezoelectric layer 16 to balance the air pressure to cope with the stress generated during the process, thereby forming a closed first acoustic reflector cavity 191 and second acoustic reflector cavity 192. Compared to the structural characteristics of bulk acoustic wave resonators formed in related technologies, where the original top and bottom acoustic reflectors are interconnected and unsealed, the bulk acoustic wave resonator provided in this embodiment of the invention features an arc-shaped surface F1 on the surfaces of the first electrode 14, the second electrode 17, and the piezoelectric layer 16. This arc-shaped surface F1 ensures that the first electrode 14, the second electrode 17, and the piezoelectric layer 16 can withstand the stress generated during the process without causing the film layer to break due to its curvature. Therefore, vent holes are not required on the piezoelectric layer 16. Vent holes indirectly increase the area of ​​the auxiliary region, thereby increasing the actual footprint of the bulk acoustic wave resonator. In the bulk acoustic wave resonator provided in this embodiment of the invention, since vent holes are not required on the piezoelectric layer 16, the area for vent holes can be saved. Therefore, the technical solution provided in this embodiment of the invention can reduce the actual footprint of the bulk acoustic wave resonator.

[0064] Please continue to refer to this. Figure 9The arc-shaped surface F1 is formed in the following areas: the effective region S of the bulk acoustic wave resonator and a region extending a predetermined distance from the outer edge of the effective region S towards the non-overlapping side of the first electrode 14 and the second electrode 17. The effective region S is located in the central part of the overall structure of the bulk acoustic wave resonator, and is the area where the first acoustic mirror cavity 191 and the second acoustic mirror cavity 192, the first electrode 14, the piezoelectric layer 16, and the second electrode 17 overlap. The arc-shaped surface F1 can cover areas prone to stress damage (such as the effective region S), ensuring the normal overall performance of the bulk acoustic wave resonator.

[0065] For example, the preset distance can be 10µm.

[0066] Please continue to refer to this. Figure 9 The first electrode 14 has a first electrode top surface 141 and a first electrode bottom surface 142; the arcuate surface of the first electrode 14 includes an arcuate surface on the first electrode top surface 141 and an arcuate surface on the first electrode bottom surface 142, and the arcuate direction of the arcuate surface of the first electrode top surface 141 is the same as the arcuate direction of the arcuate surface of the first electrode bottom surface 142. The arc-shaped surface of the top surface 141 of the first electrode is formed in the following areas: the effective area S and the area extending a predetermined distance from the outer edge of the effective area S to the side where the first electrode 14 and the second electrode 17 do not overlap. The area where the arcuate surface of the bottom surface 142 of the first electrode is formed is the same as the area where the arcuate surface of the top surface 141 of the first electrode is formed. The arc-shaped surface of the top surface of the piezoelectric layer 16 has the same arc direction as the arc-shaped surface of the bottom surface 142 of the first electrode.

[0067] The area where the first electrode 14, the second electrode 17, and the piezoelectric layer 16 overlap is the effective region. Taking the outer edge of the effective region S as a reference, the direction extending outward from the arc-shaped surface on the first electrode 14 is... Figure 9 The X1 direction shown includes the area covered by the first electrode 14 and the second electrode 17 that do not overlap.

[0068] Please continue to refer to this. Figure 9 The second electrode 17 has a top surface 171 and a bottom surface 172 opposite to each other; the arcuate surface of the second electrode 17 includes an arcuate surface on the top surface 171 and an arcuate surface on the bottom surface 172, and the arcuate direction of the arcuate surface of the top surface 171 and the arcuate direction of the arcuate surface of the bottom surface 172 are the same. The arc-shaped surface of the top surface 171 of the second electrode is formed in the following areas: the effective area S and the area extending a predetermined distance from the outer edge of the effective area S to the side where the second electrode 17 and the first electrode 14 do not overlap. The arcuate surface of the bottom surface of the piezoelectric layer 16 has the same arcuate direction as the arcuate surface of the top surface 171 of the second electrode; the bottom surface of the piezoelectric layer 16 is relative to the top surface of the piezoelectric layer 16. The area where the arcuate surface of the bottom surface 172 of the second electrode is formed is the same as the area where the arcuate surface of the top surface 171 of the second electrode is formed.

[0069] The piezoelectric layer 16, the first electrode 14, and the second electrode 17 are formed based on the same target prestress deposition, so the arc direction of the formed arc surface F1 is uniform.

[0070] For the arc-shaped surface on the second electrode 17, taking the outer edge of the effective area S as a reference, the direction extending outward is... Figure 9 The X2 direction shown covers the area where the first electrode 14 and the second electrode 17 do not overlap. The X2 direction is opposite to the X1 direction.

[0071] In one embodiment, the arcuate direction of the arcuate surface F1 includes a first direction Y1 toward the first substrate 101 and a second direction Y2 toward the second substrate 102; the stress generated during the process is a prestress generated during the fabrication of the bulk acoustic wave resonator, and the target prestress is used to enable the first electrode 14, the second electrode 17, and the piezoelectric layer 16 to cope with the stress generated during the process, and the value of the target prestress is within the range of the film fracture threshold.

[0072] Prestress can improve the piezoelectric coefficient of the piezoelectric layer, thereby enhancing performance such as the electromechanical coupling coefficient. Therefore, the performance of the resonator can be improved by setting and adjusting the prestress.

[0073] Figure 9 In the structure shown, the curvature direction of the arcuate surface F1 is the first direction Y1. In other embodiments, the curvature direction of the arcuate surface F1 can also be the second direction Y2 towards the second substrate 102. Figure 9 Only the direction is shown; a detailed structural diagram under Y2 is not shown.

[0074] Different designs can be used to form arc surfaces with different curvature directions to adapt to different application scenarios, improve design flexibility, and ensure that the target prestress can enable the first electrode 14, the second electrode 17 and the piezoelectric layer 16 to cope with the stress generated during the process, and the value of the target prestress is within the film fracture threshold range.

[0075] The target prestress control forms an arc-shaped surface, which in turn controls the degree of curvature of the arc-shaped surface F1, ensuring that the curvature does not cause film breakage while still being able to cope with the stress generated during the process. Please continue to refer to... Figure 9 The surfaces of the first electrode 14, the second electrode 17, and the piezoelectric layer 16 further include a flat surface F2; under the target prestress, the maximum vertical distance d from the arc-shaped surface F1 to the plane containing the flat surface F2 is constrained by the stress generated during the process and the film fracture threshold.

[0076] Because the bulk acoustic resonator provided in this embodiment of the invention employs a fabrication process of... Figure 2 The fabrication process of the bulk acoustic resonator shown indicates that the resulting piezoelectric layer 16, first electrode 14, and second electrode 17 have a perfectly flat surface F2. Figure 9 As shown, the flat surface F2 is a stepless surface formed by an etching-free cavity process; and the vertical distance from any position on the upper surface of the flat surface of the piezoelectric layer 16 to the corresponding position on the upper surface of the flat surface of the first electrode 14 is fixed; the vertical distance from any position on the lower surface of the flat surface of the piezoelectric layer 16 to the corresponding position on the lower surface of the flat surface of the second electrode 17 is fixed.

[0077] When an arc-shaped surface F1 is formed, the maximum vertical distance d reflects the degree of curvature of the arc-shaped surface F1. Based on the foregoing analysis, the arc-shaped surface is formed according to the target prestress, which is determined based on the stress generated during the process and the film fracture threshold. Therefore, the maximum vertical distance d reflecting the degree of curvature of the arc-shaped surface F1 formed based on the target prestress is also constrained by the stress generated during the process and the film fracture threshold, thus providing a basis for the implementation of the technical solution of this embodiment of the invention without setting vent holes.

[0078] In one embodiment, the bulk acoustic resonator may further include: a first electrode protection layer located on the first electrode 14 and / or a second electrode protection layer located on the second electrode 17, and a piezoelectric layer protection layer located on the piezoelectric layer. The surface of the first electrode protective layer includes the arc-shaped surface; The surface of the second electrode protective layer includes the arc-shaped surface; The surface of the piezoelectric protective layer includes the arc-shaped surface.

[0079] When a first electrode protective layer is formed on the first electrode 14, the first electrode protective layer can also be formed by deposition according to the target prestress, so that the surface of the first electrode protective layer also includes an arc-shaped surface, and the forming area of ​​the arc-shaped surface can be the same as the forming area of ​​the arc-shaped surface of the top surface 141 of the first electrode.

[0080] In the case where a second electrode protective layer 13 is formed on the second electrode 17 (e.g.) Figure 9 As shown), the second electrode protective layer 13 can also be formed by target prestress deposition, so that the surface of the second electrode protective layer 13 also includes an arc-shaped surface, and the forming area of ​​the arc-shaped surface can be the same as the forming area of ​​the arc-shaped surface of the bottom surface 172 of the second electrode.

[0081] Of course, if a protective layer (first electrode protective layer and second electrode protective layer) is formed on both the first electrode 14 and the second electrode 17, the protective layer is also formed by deposition according to the target prestress, so that the surface of the protective layer includes an arc-shaped surface. The formation area of ​​the arc-shaped surface can be referred to the above description, and will not be repeated here.

[0082] The piezoelectric protective layer can be formed on the upper and / or lower surface of the piezoelectric layer. The material of the piezoelectric protective layer can be the same as the material of the electrode protective layer (first electrode protective layer and second electrode protective layer) formed on the first electrode 14 and the second electrode 17, such as one or more layers of silicon nitride, silicon oxide, and aluminum nitride as described above.

[0083] The embodiments of the present invention do not limit the material of the protective layer (e.g., electrode protective layer, piezoelectric protective layer). The preferred material of the protective layer can be aluminum nitride, silicon oxide, or a combination of one or more layers of aluminum nitride.

[0084] In some embodiments, the bulk acoustic resonator provided in this invention does not have a stacked structure outside the regions where the first acoustic mirror cavity 191 and the second acoustic mirror cavity 192 are located; the stacked structure includes a structure formed by the overlapping of the first electrode 14, the piezoelectric layer 16, the second electrode 17 and the second support layer 112.

[0085] The overlap of the second electrode 17, the first electrode 14, the piezoelectric layer 16, and the second support layer 112 leads to a large passband ripple in the filter. Therefore, by using the first support layer 111 and the second support layer 112 as boundaries, and ensuring that the first substrate 101 and the second substrate 102 do not have an overlapping stacked structure of the second electrode 17, the first electrode 14, the piezoelectric layer 16, and the second support layer 112 outside the cavity region (the first acoustic mirror cavity 191 and the second acoustic mirror cavity 192), the ripple in the passband of the bulk acoustic resonator can be reduced, making the passband of the bulk acoustic resonator flat.

[0086] In other embodiments, the bulk acoustic resonator may further include a through-hole located on a piezoelectric layer 16 outside the first acoustic mirror cavity 191 and the second acoustic mirror cavity 192.

[0087] The vias are also formed on the piezoelectric layer 16, but they are not located at the edge of the effective region S; that is, they are not vent holes and do not penetrate the first acoustic mirror cavity 191 and the second acoustic mirror cavity 192. The vias can be used to adjust the film stress, optimize process compatibility, or achieve specific functional expansion to further optimize the performance of the bulk acoustic resonator.

[0088] In one embodiment, the bulk acoustic resonator may further include: a boundary structure; located at the edge of the effective region, the boundary structure is disposed on the surface of the first electrode and / or on the surface of the second electrode. The plane of the boundary structure forms a height difference with the plane in the effective area where the boundary structure is not formed in the direction perpendicular to the plane of the piezoelectric layer; the plane of the boundary structure is higher than the plane where the boundary structure is not formed, or the plane of the boundary structure is lower than the plane where the boundary structure is not formed.

[0089] The materials used to prepare the boundary structure can be molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium, or composites or alloys of the above metals.

[0090] This invention also provides a method for forming a bulk acoustic resonator, used to form the bulk acoustic resonator described in any of the foregoing embodiments.

[0091] Please refer to Figure 10 , Figure 10 This is a schematic flowchart of a method for forming a bulk acoustic resonator provided in an embodiment of the present invention.

[0092] like Figure 10 As shown, the method includes the following steps: Step S200: Provide a temporary substrate.

[0093] Step S201: A first electrode layer, a piezoelectric material layer, and a second electrode layer, comprising an arc-shaped surface, are formed on the temporary substrate based on the target prestress.

[0094] The target prestress is determined based on the stress generated during the process and the membrane fracture threshold.

[0095] The first electrode layer, the second electrode layer, and the piezoelectric material layer are formed according to the target prestress, so that the arc-shaped surface can compressively offset the stress generated by the film layer in the subsequent process, reduce the risk of film layer cracking, and extend fatigue life.

[0096] Step S202: The second electrode layer is processed to expose part of the piezoelectric material layer, thereby obtaining the second electrode.

[0097] In step S203, a second support layer is formed on the surface of the second electrode away from the exposed piezoelectric material layer, and on the surface of the exposed piezoelectric material layer.

[0098] Step S204: Bond the second substrate onto the second support layer to form a closed second acoustic mirror cavity.

[0099] Step S205: Remove the temporary substrate, process the first electrode layer to expose part of the piezoelectric material layer, and obtain the first electrode.

[0100] After processing the structural layout of the second electrode side, the first electrode layer side is processed. At this time, the first substrate side can be used as the bottom contacting the plane, and the first electrode layer can be used as the top process surface.

[0101] Step S206: Process the piezoelectric material layer to obtain a piezoelectric layer.

[0102] The piezoelectric material layer is processed, for example, by patterning one side of the piezoelectric material layer to form a wiring layer. This wiring layer can be used for electrical connections between the upper and lower electrodes, ensuring the electrical performance of the bulk acoustic wave resonator. Materials for the wiring layer can include molybdenum, ruthenium, gold, aluminum, magnesium, tungsten, copper, titanium, iridium, osmium, chromium, or composites or alloys of these metals.

[0103] Step S207: A first support layer is formed on the first substrate.

[0104] The first support layer corresponds to the side of the surface of the first electrode away from the exposed piezoelectric layer, and also corresponds to the surface of the exposed piezoelectric layer.

[0105] In step S208, the first substrate with the first support layer is bonded to the first electrode to form a closed first acoustic mirror cavity, thereby forming a bulk acoustic resonator.

[0106] The arc-shaped surface is located inside the second acoustic mirror cavity and the first acoustic mirror cavity.

[0107] As can be seen, the method for forming a bulk acoustic wave resonator provided in this embodiment of the invention does not involve setting vent holes at the edge of the effective region on the piezoelectric layer. Instead, it forms a first piezoelectric layer, a second piezoelectric layer, and another piezoelectric layer with arc-shaped surfaces through targeted prestress deposition. The target prestress is determined based on the stress generated during the process and the film fracture threshold. Therefore, this target prestress can cope with steps such as low vacuum levels in the process that may affect the stability of the film layer. Furthermore, the process steps of bonding a second substrate to a first support layer and bonding a first substrate to a second support layer ensure that the final first electrode, second electrode, and the arc-shaped surface of the piezoelectric layer are located inside the closed first and second acoustic mirror cavities. Therefore, the technical solution provided in this embodiment of the invention can reduce the actual footprint of the bulk acoustic wave resonator.

[0108] In some implementations, step S201 may include: On the temporary substrate, a first electrode layer material, a piezoelectric layer material, and a second electrode layer material are sequentially deposited based on the target prestress to form an arc-shaped surface in the target area, thereby obtaining a first electrode layer, a piezoelectric material layer, and a second electrode layer. The target area is: the effective area of ​​the bulk acoustic resonator and the area extending outward by a predetermined distance from the outer edge of the effective area, such that the outwardly extended area is the area on the side where the first electrode and the second electrode do not overlap.

[0109] The target area is a core region that is easily affected by stress generated during the process. Therefore, forming an arc-shaped surface in the target area can protect the film layer and prevent it from cracking.

[0110] In one embodiment, the step of sequentially depositing a first electrode layer material, a piezoelectric layer material, and a second electrode layer material on the temporary substrate based on a target prestress, forming an arc-shaped surface in the target region, to obtain the first electrode layer, the piezoelectric material layer, and the second electrode layer includes: According to the first type of target prestress, a first electrode layer material, a piezoelectric layer material, and a second electrode layer material are sequentially deposited on the temporary substrate based on the first type of target prestress, forming an arc-shaped surface with the curvature direction facing the first substrate in the target region, thus obtaining the first electrode layer, the piezoelectric material layer, and the second electrode layer. Alternatively, according to the second type of target prestress, a first electrode layer material, a piezoelectric layer material, and a second electrode layer material are sequentially deposited on the temporary substrate based on the second type of target prestress, forming an arc-shaped surface in the target area with the arc direction facing the second substrate, thereby obtaining a first electrode layer, a piezoelectric material layer, and a second electrode layer.

[0111] The arc-shaped surfaces formed by the first type of target prestress and the second type of target prestress have opposite curvature directions to adapt to different application scenarios.

[0112] Optionally, after the step of bonding the first substrate with the first support layer to the first electrode to form a closed first acoustic mirror cavity, the method further includes: A through hole is formed on the piezoelectric layer in the outer region of the first acoustic mirror cavity and / or the second acoustic mirror cavity.

[0113] The vias can be used to regulate film stress, optimize process compatibility, or enable specific functional extensions to further optimize the performance of the bulk acoustic wave resonator.

[0114] The specific implementation of the above-mentioned method for forming a bulk acoustic resonator will be further explained below.

[0115] Please refer to Figure 11 , Figure 11 This is another schematic diagram of the process for forming a bulk acoustic resonator provided in an embodiment of the present invention.

[0116] like Figure 11 As shown, the method includes the following steps: Step S300: Provide a temporary substrate.

[0117] Step S301: A first electrode layer, a piezoelectric material layer, and a second electrode layer, including an arc-shaped surface, are formed on the temporary substrate based on the target prestress.

[0118] The target prestress is determined based on the stress generated during the process and the membrane fracture threshold.

[0119] Please refer to Figure 12 , Figure 12 This is a schematic diagram of the first structure obtained by the method for forming a bulk acoustic resonator provided in an embodiment of the present invention.

[0120] Figure 12 The structure shown can be the structure obtained after performing the above step S301.

[0121] like Figure 12 As shown, a first electrode layer 140 is formed on a temporary substrate 00, followed by a piezoelectric material layer 160 on the first electrode layer 140, and a second electrode layer 170 on the piezoelectric material layer 160. It can be seen that the surfaces of the first electrode layer 140, the piezoelectric material layer 160, and the second electrode layer 170 formed on the temporary substrate 00 all include an arc-shaped surface F1, which can effectively offset the stress generated during the process and prevent the film from breaking due to the presence of the arc-shaped surface within the film fracture threshold range.

[0122] Of course, a protective material layer 130 can also be formed on the second electrode layer 170 based on the same target prestress deposition, such as Figure 12 As shown.

[0123] Step S302: The second electrode layer is patterned to expose part of the piezoelectric material layer, thus obtaining the second electrode.

[0124] After forming the first electrode layer 140, the piezoelectric material layer 160, and the second electrode layer 170, the following is obtained: Figure 12 After the structure shown, the second electrode layer 170 can be processed. Please refer to [the documentation / reference]. Figure 13 , Figure 13 This is a schematic diagram of the second structure obtained by the method for forming a bulk acoustic resonator provided in an embodiment of the present invention.

[0125] Figure 13 The structure shown can be a schematic diagram of the structure obtained after step S302 is executed. For example... Figure 13 As shown, for Figure 12 The second electrode layer 170 in the structure shown is patterned to obtain the second electrode.

[0126] Of course, if a protective material layer 130 is formed on the second electrode 17, the protective material layer 130 can also be patterned to obtain the second electrode protective layer 13, such as... Figure 13 As shown. Alternatively, boundary structures such as a frame structure can be set on the second electrode to improve performance.

[0127] In step S303, a second support layer is formed on the surface of the second electrode away from the exposed piezoelectric material layer, and on the surface of the exposed piezoelectric material layer.

[0128] Step S304: Bond the second substrate onto the second support layer to form a closed second acoustic mirror cavity, and remove the temporary substrate to use the second substrate as the bottom structure.

[0129] After obtaining the second electrode 17, further processing can proceed. Please refer to [the relevant documentation / reference]. Figure 14 , Figure 14 This is a schematic diagram of the third structure obtained by the method for forming a bulk acoustic resonator provided in the embodiments of the present invention.

[0130] Figure 14 The structure shown can be a schematic diagram of the structure obtained after steps S303 and S304 are executed.

[0131] exist Figure 13Based on the structure shown, a second support layer 112 is formed on one side edge of the second electrode 17 and on the edge region of the exposed piezoelectric material layer 160; then, a second substrate 102 is bonded to the second support layer 112 to form a closed second acoustic mirror cavity 192 (bottom acoustic mirror cavity) between the second support layer 112, the second substrate 102 and the second electrode 17, and the temporary substrate 00 is removed to obtain... Figure 14 The structure shown. The material used to prepare the second substrate 102 can be single-crystal silicon, gallium arsenide, sapphire, quartz, silicon carbide, SOI, etc.

[0132] Step S305: The first electrode layer is patterned to expose part of the piezoelectric material layer, thereby obtaining the first electrode, and the first and second etch holes that penetrate the first electrode and have the top surface of the exposed piezoelectric material layer as the bottom.

[0133] In obtaining Figure 14 After completing the structure shown, the first electrode layer 140 can be further processed. Please refer to [reference needed]. Figure 15 , Figure 15 This is a schematic diagram of the fourth structure obtained by the method for forming a bulk acoustic resonator provided in the embodiments of the present invention.

[0134] Figure 15 The structure shown can be a schematic diagram of the structure obtained after step S305 is executed. Figure 15 The first electrode layer 140 is patterned to obtain the first electrode 14, the first etch hole 220, and the second etch hole 21. The second etch hole 21 is an electrode etching groove.

[0135] Step S306: The piezoelectric material layer corresponding to the first etched hole is patterned to obtain a piezoelectric layer and a third etched hole penetrating the first electrode and the piezoelectric layer. The third etched hole is used to form a wiring layer.

[0136] Step S307: A first support layer is formed on the first substrate.

[0137] The first support layer corresponds to the side of the surface of the first electrode away from the exposed piezoelectric layer, and also corresponds to the surface of the exposed piezoelectric layer.

[0138] In step S308, the first substrate with the first support layer is bonded to the first electrode to form a closed first acoustic mirror cavity, thereby forming a bulk acoustic resonator.

[0139] The structural diagram obtained after steps S306-308 can be used for further reference. Figure 9 .like Figure 9As shown, a first substrate 101 with a first support layer 111 is bonded to one side edge region of the first electrode 14 and to the opposite side edge of the piezoelectric layer 16, so that a closed first acoustic mirror cavity 191 (top acoustic mirror cavity) is formed between the first support layer 111, the first substrate 101, the first electrode 14 and the exposed surface of the piezoelectric layer 16, where 22 is a wiring layer, to obtain the final bulk acoustic resonator.

[0140] This invention also provides a filter comprising a plurality of bulk acoustic wave resonators, wherein at least one bulk acoustic wave resonator is a bulk rising wave resonator as described in any of the foregoing embodiments.

[0141] This invention also provides a communication device, including the filter described in the foregoing embodiments.

[0142] This invention also provides a terminal, including the filter described in the above embodiments.

[0143] The foregoing describes multiple embodiments of the present invention. The optional methods described in each embodiment can be combined and cross-referenced without conflict, thereby extending to a variety of possible embodiments. These can all be considered as embodiments disclosed or made public by the present invention.

[0144] While the embodiments of the present invention have been disclosed above, the present invention is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A bulk acoustic resonator, characterized in that, include: First electrode, second electrode, and piezoelectric layer; The surfaces of the first electrode, the second electrode, and the piezoelectric layer all include arc-shaped surfaces, which are formed based on target prestress. The target prestress is determined based on the stress generated during the process and the membrane fracture threshold. A closed first acoustic mirror cavity is formed between the first electrode, the exposed surface of the piezoelectric layer, the first support layer located on the first electrode, and the first substrate bonded to the first electrode through the first support layer. A closed second acoustic mirror cavity is formed between the second electrode, the exposed surface of the piezoelectric layer, the second support layer located on the second electrode, and the second substrate bonded to the second electrode through the second support layer; The arc-shaped surface is located inside the second acoustic mirror cavity and the first acoustic mirror cavity.

2. The bulk acoustic resonator as described in claim 1, characterized in that, The first acoustic mirror cavity and the second acoustic mirror cavity are independent cavities, and there is no vent hole penetrating the first acoustic mirror cavity and the second acoustic mirror cavity; The overall profile of the bulk acoustic resonator is pentagonal; there are no additional openings or protrusions at the edges and corners of the pentagonal profile for sacrificial layer release.

3. The bulk acoustic resonator as described in claim 2, characterized in that, The arc-shaped surface formation area is: the effective area of ​​the bulk acoustic resonator and the area extending a predetermined distance from the outer edge of the effective area to the side where the first electrode and the second electrode do not overlap; The effective region is located in the central part of the overall structure of the bulk acoustic resonator, and is the area where the first acoustic mirror cavity, the second acoustic mirror cavity, the first electrode, the piezoelectric layer, and the second electrode overlap.

4. The bulk acoustic resonator as described in claim 3, characterized in that, The first electrode has a top surface and a bottom surface that are opposite each other; The arcuate surface of the first electrode includes an arcuate surface on the top surface of the first electrode and an arcuate surface on the bottom surface of the first electrode, and the arcuate direction of the arcuate surface on the top surface of the first electrode is the same as the arcuate direction of the arcuate surface on the bottom surface of the first electrode. The arc-shaped surface area formed by the first electrode top surface includes: the effective area and an area extending a predetermined distance from the outer edge of the effective area to the side where the first electrode and the second electrode do not overlap. The region where the arcuate surface of the bottom surface of the first electrode is formed is the same as the region where the arcuate surface of the top surface of the first electrode is formed. The arc-shaped surface of the top surface of the piezoelectric layer has the same arc direction as the arc-shaped surface of the bottom surface of the first electrode.

5. The bulk acoustic resonator as described in claim 4, characterized in that, The second electrode has a top surface and a bottom surface opposite each other; The arcuate surface of the second electrode includes an arcuate surface on the top surface of the second electrode and an arcuate surface on the bottom surface of the second electrode, and the arcuate direction of the arcuate surface on the top surface of the second electrode is the same as the arcuate direction of the arcuate surface on the bottom surface of the second electrode. The arc-shaped surface area formed by the second electrode top surface includes: the effective area and an area extending a predetermined distance from the outer edge of the effective area to the side where the second electrode and the first electrode do not overlap. The arcuate surface of the bottom surface of the piezoelectric layer has the same arcuate direction as the arcuate surface of the top surface of the second electrode; the bottom surface of the piezoelectric layer is relative to the top surface of the piezoelectric layer. The area where the arcuate surface of the bottom surface of the second electrode is formed is the same as the area where the arcuate surface of the top surface of the second electrode is formed.

6. The bulk acoustic resonator according to any one of claims 1-5, characterized in that, The arcuate direction of the arcuate surface includes a first direction toward the first substrate and a second direction toward the second substrate; the stress generated during the process is the prestress generated during the fabrication of the bulk acoustic wave resonator, and the target prestress is used to enable the first electrode, the second electrode, and the piezoelectric layer to cope with the stress generated during the process, and the value of the target prestress is within the range of the film fracture threshold.

7. The bulk acoustic resonator as described in claim 6, characterized in that, The surfaces of the first electrode, the second electrode, and the piezoelectric layer further include: a flat surface; under the target prestress, the maximum vertical distance from the arc-shaped surface to the plane containing the flat surface is constrained by the stress generated during the process and the film fracture threshold. The flat surface is a stepless surface formed using a non-etching cavity process; and the vertical distance from any position on the upper surface of the flat surface of the piezoelectric layer to the corresponding position on the upper surface of the flat surface of the first electrode is fixed; the vertical distance from any position on the lower surface of the flat surface of the piezoelectric layer to the corresponding position on the lower surface of the flat surface of the second electrode is fixed.

8. The bulk acoustic resonator as described in claim 1, characterized in that, Also includes: A first electrode protective layer located on the first electrode and / or a second electrode protective layer located on the second electrode, and a piezoelectric layer protective layer located on the piezoelectric layer; The surface of the first electrode protective layer includes the arc-shaped surface; The surface of the second electrode protective layer includes the arc-shaped surface; The surface of the piezoelectric protective layer includes the arc-shaped surface.

9. The bulk acoustic resonator according to any one of claims 1-5, characterized in that, Outside the regions where the first acoustic mirror cavity and the second acoustic mirror cavity are located, there is no stacked structure; the stacked structure includes a structure formed by the overlapping of a first electrode, a piezoelectric layer, a second electrode, and a second support layer.

10. The bulk acoustic resonator as claimed in claim 1, characterized in that, Also includes: Through hole; The through-hole is located on the piezoelectric layer outside the first acoustic mirror cavity and the second acoustic mirror cavity.

11. The bulk acoustic resonator as described in claim 3, characterized in that, Also includes: Boundary structure; within the effective region, at the edge of the effective region, the boundary structure is disposed on the surface of the first electrode, and / or on the surface of the second electrode; The plane of the boundary structure forms a height difference with the plane in the effective area where the boundary structure is not formed in the direction perpendicular to the plane of the piezoelectric layer; the plane of the boundary structure is higher than the plane where the boundary structure is not formed, or the plane of the boundary structure is lower than the plane where the boundary structure is not formed.

12. A filter, characterized in that, include: A plurality of bulk acoustic resonators, wherein at least one bulk acoustic resonator is the bulk acoustic resonator according to any one of claims 1-11.

13. A communication device, characterized in that, Includes the filter as described in claim 12.

14. A terminal, characterized in that, Includes the filter as described in claim 12.

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