An acoustic resonator device and its formation method, and a radio frequency filter.

Abstract

The application relates to an acoustic wave resonator device and a forming method thereof, and a radio frequency filter. The acoustic wave resonator device comprises a substrate layer, a sacrifice layer on the substrate layer, the sacrifice layer comprising a cavity, a piezoelectric thin film layer on the sacrifice layer, the piezoelectric thin film layer comprising at least one strip-shaped piezoelectric thin film and etching grooves on both sides of each strip-shaped piezoelectric thin film, the etching grooves being communicated with the cavity, a bottom conductor layer under the piezoelectric thin film layer, the bottom conductor layer comprising a bottom bus bar and at least one bottom finger electrode suspended in the cavity, a top conductor layer on the piezoelectric thin film layer, the top conductor layer comprising a top bus bar, a top terminal, a bottom terminal and at least one top finger electrode, and the top finger electrode, the bottom finger electrode and the strip-shaped piezoelectric thin film corresponding to each other. In the embodiment of the application, the suspended top finger electrode, the strip-shaped piezoelectric thin film and the bottom finger electrode are arranged in the device to support the mode of vertical electric field excitation double shear bulk acoustic wave, so that the device meets the demand of higher frequency and larger bandwidth.

Description

Technical Field

[0001] This invention belongs to the field of resonator technology, specifically an acoustic resonator device and its formation method, and a radio frequency filter. Background Technology

[0002] Radio frequency (RF) filters, as a crucial component of front-end modules, are two-port elements used to allow and control the passage of RF signals within a specific frequency range, while blocking or attenuating RF signals in other frequency ranges. RF filters are essential in systems using wireless communication networks, including base stations, mobile terminals, IoT devices, automobiles, and new industrial management systems. The performance of RF filters is primarily evaluated by parameters such as passband center frequency, bandwidth, insertion loss, rejection, isolation, and power handling capability. Using higher-performance RF filters in mobile communications, satellite communications, broadcasting, and other communication systems can achieve better signal quality, greater network capacity, and higher energy efficiency at various levels of the system, helping to separate different signal frequency bands, improve signal quality, and reduce interference.

[0003] With the rapid development of communication standards, the widely adopted 5G and future 6G communication standards have placed higher demands on radio frequency (RF) filters, primarily including higher frequencies, larger bandwidths, and smaller sizes. The bandwidth and insertion loss of RF filters, as crucial parameters, have a significant impact on the performance of the entire RF system. In the 5G communication spectrum specifications, the n77 and n79 bands in Frequency Range 1 (FR1) have bandwidths of 900 MHz and 600 MHz respectively at a center frequency of approximately 4 GHz. This poses a significant challenge to traditional film bulk acoustic resonators (FBARs) and surface acoustic wave (SAW) resonators used in RF filters. Furthermore, for the future 5G FR1 spectrum and the 6G communication spectrum (greater than 6 GHz), existing technologies struggle to simultaneously meet the high frequency and high performance requirements of RF filters. Therefore, a novel acoustic resonator is urgently needed to address the technical problem of traditional acoustic resonators failing to meet the demands for higher frequencies and greater bandwidths. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides an acoustic resonator device and its formation method, as well as a radio frequency filter.

[0005] In a first aspect, embodiments of this application disclose an acoustic resonator device, comprising:

[0006] Substrate layer;

[0007] A sacrificial layer is located on the substrate layer; the sacrificial layer includes at least one cavity;

[0008] A piezoelectric thin film layer is located on the sacrificial layer; the piezoelectric thin film layer includes at least one parallel strip-shaped piezoelectric thin film and etching grooves located on both sides of each strip-shaped piezoelectric thin film; the etching grooves communicate with the cavity;

[0009] A bottom conductor layer is located below the piezoelectric thin film layer; the bottom conductor layer is in contact with the strip-shaped piezoelectric thin film; the bottom conductor layer includes a bottom busbar and at least one bottom finger electrode, the at least one bottom finger electrode being connected to the bottom busbar; the bottom finger electrode is suspended in the cavity; the bottom finger electrode and the strip-shaped piezoelectric thin film correspond one-to-one;

[0010] A top conductor layer is located on the piezoelectric thin film layer; the top conductor layer is in contact with the strip-shaped piezoelectric thin film; the top conductor layer includes a top busbar, a top terminal, a bottom terminal, and at least one top finger bar electrode; one end of the top busbar is connected to the top terminal, and the other end is connected to at least one top finger bar electrode; the bottom terminal portion is located in the piezoelectric thin film layer and contacts the bottom busbar; the top finger bar electrode and the strip-shaped piezoelectric thin film correspond one-to-one.

[0011] In some possible embodiments,

[0012] The piezoelectric thin film layer includes a through-hole; the bottom terminal portion is located in the through-hole and contacts the bottom busbar.

[0013] In some possible embodiments,

[0014] At least one bottom finger strip electrode and its corresponding top finger strip electrode are configured to apply a corresponding radio frequency signal to excite a double shear body acoustic wave in the corresponding strip-shaped piezoelectric film.

[0015] In some possible embodiments,

[0016] The resonant frequency of the acoustic resonator device is determined by the width and thickness of the stack consisting of the top finger bar electrode, the bar piezoelectric film, and the bottom finger bar electrode.

[0017] In some possible embodiments,

[0018] The width of the strip piezoelectric film is less than or equal to the width of the bottom finger strip electrode, and the length of the strip piezoelectric film is greater than or equal to the length of the bottom finger strip electrode;

[0019] The width of the strip piezoelectric film is greater than or equal to the width of the top finger strip electrode, and the length of the strip piezoelectric film is greater than or equal to the length of the top finger strip electrode.

[0020] In some possible embodiments,

[0021] The ratio of the sum of the thicknesses of the top finger bar electrode, the bar piezoelectric film, and the bottom finger bar electrode to the width of the bar piezoelectric film ranges from 0.5 to 1.5.

[0022] In some possible embodiments,

[0023] The material of the piezoelectric thin film layer is at least one of lithium niobate, lithium tantalate, and aluminum nitride; the thickness of the piezoelectric thin film is 50-1000 nanometers.

[0024] The material of the top conductor layer is at least one of aluminum, molybdenum, chromium, gold, platinum, and titanium;

[0025] The material of the bottom conductor layer is at least one of aluminum, molybdenum, chromium, gold, platinum and titanium.

[0026] In some possible embodiments,

[0027] The substrate is a single-layer structure composed of silicon or silicon dioxide;

[0028] Alternatively; the substrate layer is a stacked structure composed of at least two of the following materials: silicon, silicon carbide, sapphire, or silicon dioxide.

[0029] In some possible embodiments,

[0030] The sacrificial layer is made of silicon or silicon dioxide.

[0031] Secondly, embodiments of this application disclose a radio frequency filter, including the acoustic resonator device described in any one of the above claims;

[0032] Multiple series resonators and multiple parallel resonators are required to form the topology of an RF filter by interconnecting multiple acoustic resonator devices. When the thickness of the top finger electrode, the thickness of the strip piezoelectric film, and the thickness of the bottom finger electrode in each acoustic resonator device are the same, the RF filter of the preset frequency band is obtained by adjusting the width of the top finger electrode, the width of the strip piezoelectric film, and the width of the bottom finger electrode. The width value in the parallel resonator is greater than the width value in the series resonator.

[0033] Thirdly, embodiments of this application disclose a method for forming an acoustic resonator device, including:

[0034] A bonding assembly is provided; the bonding assembly includes a substrate layer, a sacrificial layer on the substrate layer, an initial bottom conductor layer in the sacrificial layer, and a piezoelectric thin film layer on the sacrificial layer and the initial bottom conductor layer; the initial bottom conductor layer includes a bottom busbar and a bottom finger electrode portion;

[0035] Etching the piezoelectric thin film layer creates vias to expose part of the bottom busbar;

[0036] An initial top conductor layer is formed on the remaining piezoelectric thin film layer; the initial top conductor layer includes a top terminal, a bottom terminal, a top busbar, and a top finger electrode portion, the bottom terminal fills the through hole and contacts the bottom busbar, and the top terminal contacts the top busbar;

[0037] The stack consisting of the bottom finger bar electrode, the piezoelectric thin film layer and the top finger bar electrode is etched to obtain at least one resonator structure arranged in parallel and etching grooves located on both sides of each resonator structure; each resonator structure includes a top finger bar electrode, a strip-shaped piezoelectric thin film and a bottom finger bar electrode, the top finger bar electrode is connected to the top electrode busbar and the bottom finger bar electrode is connected to the bottom busbar.

[0038] A cavity is formed by removing part of the sacrificial layer located below the bottom finger electrode, resulting in an acoustic resonator device; the resonator structure is suspended in the cavity.

[0039] In some possible embodiments,

[0040] The combination provided includes:

[0041] Provides a transfer substrate layer and a piezoelectric thin film layer;

[0042] Bonding and transfer of substrate layer and piezoelectric thin film layer;

[0043] An initial bottom conductor layer is formed on the piezoelectric thin film layer;

[0044] A sacrificial layer is formed on the initial bottom conductor layer and the piezoelectric thin film layer not covered by the initial bottom conductor layer;

[0045] The interface above the sacrificial layer is bonded to the substrate layer;

[0046] The transfer substrate layer is removed to obtain the composite.

[0047] The technical solution provided in this application has the following technical effects:

[0048] The acoustic resonator device of this application includes a substrate layer; a sacrificial layer on the substrate layer; the sacrificial layer including at least one cavity; a piezoelectric thin film layer on the sacrificial layer; the piezoelectric thin film layer including at least one parallel strip-shaped piezoelectric thin film and etching grooves on both sides of each strip-shaped piezoelectric thin film; the etching grooves communicating with the cavity; a bottom conductor layer below the piezoelectric thin film layer; the bottom conductor layer in contact with the strip-shaped piezoelectric thin film; the bottom conductor layer including a bottom busbar and at least one bottom finger electrode, the at least one bottom finger electrode being connected to the bottom busbar; the bottom finger electrode being suspended in the cavity; the bottom finger electrode and the strip-shaped piezoelectric thin film corresponding one-to-one; a top conductor layer on the piezoelectric thin film layer; the top conductor layer in contact with the strip-shaped piezoelectric thin film; the top conductor layer including a top busbar, a top terminal, a bottom terminal and at least one top finger electrode; one end of the top busbar being connected to the top terminal and the other end being connected to at least one top finger electrode; the bottom terminal portion being located in the piezoelectric thin film layer and in contact with the bottom busbar; the top finger electrode and the strip-shaped piezoelectric thin film corresponding one-to-one. In this embodiment, by setting a suspended top finger bar electrode, a strip-shaped piezoelectric film, and a bottom finger bar electrode in the device, the dual shear body acoustic wave mode excited by the vertical electric field is supported, thereby enabling the device to meet the requirements of higher frequency and greater bandwidth. Attached Figure Description

[0049] To more clearly illustrate the technical solutions and advantages in the embodiments of this application 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 some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 This application provides a top-view structural schematic diagram of an acoustic resonator device;

[0051] Figure 2 This is a schematic diagram of the transverse cross-section of an acoustic resonator device provided in an embodiment of this application;

[0052] Figure 3 This is a schematic diagram of the longitudinal cross-section of an acoustic resonator device provided in an embodiment of this application;

[0053] Figure 4 This is a schematic diagram of a resonator structure provided in an embodiment of this application;

[0054] Figure 5 This application provides a top-view structural diagram of an acoustic resonator device comprising multiple resonator structures;

[0055] Figure 6This is a schematic diagram of the transverse cross-section of an acoustic resonator device including multiple resonator structures provided in an embodiment of this application;

[0056] Figure 7 This is a schematic flowchart of a method for forming an acoustic resonator device according to an embodiment of this application;

[0057] Figure 8 and Figure 10-18 This is a schematic diagram of the formation process of an acoustic resonator device provided in an embodiment of this application;

[0058] Figure 9 This is a flowchart illustrating a method for forming an assembly according to an embodiment of this application;

[0059] Figure 19 This is a schematic diagram of the displacement of the main resonant mode of an acoustic resonator device provided in an embodiment of this application;

[0060] Figure 20 This is a schematic diagram of the finite element simulation admittance curve of an acoustic resonator device provided in an embodiment of this application;

[0061] Figure 21 This is a schematic diagram of the finite element simulation admittance curve of an acoustic resonator device using strip-shaped piezoelectric films of different widths, provided in an embodiment of this application.

[0062] Figure 22 This is a schematic diagram showing the resonant frequencies of an acoustic resonator device using strip-shaped piezoelectric films of different widths for top and bottom finger electrodes made of different materials, as provided in an embodiment of this application.

[0063] Figure 23 This is a schematic diagram of a radio frequency filter including multiple acoustic resonator devices provided in an embodiment of this application;

[0064] Figure 24 This is a schematic diagram of the admittance curve of an acoustic resonator device in a radio frequency filter including multiple acoustic resonator devices, provided in an embodiment of this application.

[0065] Figure 25 This is a schematic diagram of the insertion loss curve of an acoustic resonator device in an RF filter that includes multiple acoustic resonator devices, provided in an embodiment of this application.

[0066] In the picture:

[0067] 100-Substrate layer, 200-Sacrificial layer, 201-Cavity, 300-Piezoelectric thin film layer, 301-Strip piezoelectric thin film, 302-Etching trench, 303-Through hole, 410-Initial bottom conductor layer, 411-Bottom finger strip electrode, 412-Bottom busbar, 413-Bottom terminal, 414-Bottom finger strip electrode portion, 420-Initial top conductor layer, 421-Top finger strip electrode, 422-Top busbar, 423-Top terminal, 424-Top finger strip electrode portion, 500-Transfer substrate layer. Detailed Implementation

[0068] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0069] It should be noted that the term "an embodiment" or "embodiment" in the specification of the embodiments of this application refers to a specific feature, structure, or characteristic that can be included in at least one implementation of this application. It should be understood that in the specification, claims, and accompanying drawings of the embodiments of this application, the terms "upper," "lower," "top," "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" and "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, in the description of this embodiment, unless otherwise stated, "a plurality of" means two or more. Additionally, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, for example, a process, method, system, or product that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices.

[0070] It should be understood that when an element or layer is referred to as "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it may be directly on, adjacent to, connected to, or coupled to other elements or layers, or there may be intervening elements or layers. Conversely, when an element is referred to as "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc., may be used to describe various elements, components, areas, layers, and / or portions, these elements, components, areas, layers, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, area, layer, or portion from another element, component, area, layer, or portion. Therefore, without departing from the teachings of this application, the first element, component, area, layer, or portion discussed below may be referred to as a second element, component, area, layer, or portion. And the discussion of a second element, component, area, layer, or portion does not imply that the first element, component, area, layer, or portion necessarily exists in this application.

[0071] To make the objectives, technical solutions, and advantages disclosed in the embodiments of this application clearer, the embodiments of this application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the embodiments of this application and are not intended to limit the embodiments of this application.

[0072] This application provides a novel acoustic resonator device to address the limitations of traditional acoustic resonators in handling higher frequencies and greater bandwidth requirements. This acoustic resonator device utilizes entirely new modes to achieve higher frequency selectivity, smaller size, and greater stability. Radio frequency (RF) filters fabricated using this acoustic resonator device can meet the higher frequency and greater bandwidth requirements of 5G and future 6G communication standards.

[0073] Figure 1 This application provides a top-view structural diagram of an acoustic resonator device. Figure 2 This is a schematic diagram of the transverse cross-section of an acoustic resonator device provided in an embodiment of this application. Figure 3 This is a schematic diagram of the longitudinal cross-section of an acoustic resonator device provided in an embodiment of this application. Figure 2 yes Figure 1 A schematic diagram of the cross section AA of the structure shown. Figure 3 yes Figure 1 A schematic diagram of the cross-section BB of the structure shown.

[0074] In the embodiments of this application, such as Figures 1-3As shown, the acoustic resonator device includes a substrate layer, a sacrificial layer on the substrate layer, a piezoelectric thin film layer on the sacrificial layer, a bottom conductor layer below the piezoelectric thin film layer, and a top conductor layer on the piezoelectric thin film layer. The sacrificial layer includes at least one cavity. The piezoelectric thin film layer includes at least one parallel strip-shaped piezoelectric thin film and etching grooves on both sides of each strip-shaped piezoelectric thin film, the etching grooves communicating with the cavity. The bottom conductor layer is in contact with the strip-shaped piezoelectric thin film. The bottom conductor layer includes a bottom busbar and at least one bottom finger electrode, the at least one bottom finger electrode being connected to the bottom busbar. The bottom finger electrode is suspended in the cavity, and the bottom finger electrode corresponds one-to-one with the strip-shaped piezoelectric thin film. The top conductor layer is in contact with the strip-shaped piezoelectric thin film. The top conductor layer includes a top busbar, a top terminal, a bottom terminal, and at least one top finger electrode; one end of the top busbar is connected to the top terminal, and the other end is connected to at least one top finger electrode; the bottom terminal portion is located in the piezoelectric thin film layer and contacts the bottom busbar. The top finger electrode corresponds one-to-one with the strip-shaped piezoelectric thin film.

[0075] In this embodiment, the substrate layer 100 and sacrificial layer 200 located at the bottom of the acoustic resonator device provide mechanical support for the piezoelectric thin film layer 300 located thereon.

[0076] In this embodiment, the substrate layer 100 can be a single-layer structure composed of silicon or silicon dioxide, or a stacked structure composed of at least two of silicon, silicon carbide, sapphire or silicon dioxide.

[0077] In this embodiment, the material of the sacrificial layer 200 is silicon or silicon dioxide.

[0078] In the embodiments of this application, such as Figure 2 and Figure 3 As shown, the cavity 201 located in the sacrificial layer 200 is obtained by etching the sacrificial layer 200 with an etchant. Generally, a sacrificial layer 200 of a certain thickness is still retained below the cavity 201.

[0079] In some possible embodiments, the cavity 201 extends vertically through the sacrificial layer 200 and communicates with the substrate layer 100. In some cases, the cavity 201 may also extend vertically into the substrate layer 100, or even extend vertically through the substrate layer 100.

[0080] In some possible embodiments, the cavity 201 can be of different shapes, such as a rectangle, a rounded rectangle, or an irregular polygon.

[0081] In the embodiments of this application, such as Figure 1-3As shown, the bottom conductor layer is located below the piezoelectric thin film layer 300 and contacts the bottom end of the strip-shaped piezoelectric thin film 301. The bottom conductor layer includes a bottom busbar 412 and at least one bottom finger electrode 411. All the bottom finger electrodes 411 are arranged side by side, and one end of each bottom finger electrode 411 is connected to the bottom busbar 412. All the bottom finger electrodes 411 are suspended in the cavity 201, and each bottom finger electrode 411 corresponds one-to-one with the strip-shaped piezoelectric thin film 301.

[0082] In the embodiments of this application, such as Figure 1-3 As shown, the top conductor layer is located above the piezoelectric thin film layer 300 and contacts the top end of the strip-shaped piezoelectric thin film 301. The top conductor layer includes a top busbar 422, a top finger 423, a bottom terminal 413, and at least one top finger electrode 421. All the top finger electrodes 421 are arranged side by side, and each top finger electrode 421 corresponds one-to-one with the strip-shaped piezoelectric thin film 301. One end of the top busbar 422 is connected to the top finger 423, and the other end is connected to all the top finger electrodes 421. The bottom terminal 413 is partially located on the piezoelectric thin film layer 300 and partially located in the piezoelectric thin film layer 300, and the portion of the bottom terminal 413 located in the piezoelectric thin film layer 300 contacts the bottom busbar 412. The space occupied by the portion of the bottom terminal 413 located in the piezoelectric thin film layer 300 does not need to be too large, just enough to achieve contact between the bottom terminal 413 and the bottom busbar 412.

[0083] In this application, the top busbar 422 and the top finger electrode 421 are made of the same material, and the bottom busbar 422 and the bottom finger electrode 411 are made of the same material. The materials of the top finger electrode 421, top busbar 422, bottom finger electrode 411, bottom busbar 412, top terminal 423, and bottom terminal 413 are all at least one of aluminum, molybdenum, chromium, gold, platinum, and titanium.

[0084] In some possible embodiments, the bottom finger bar electrode 411 and the top finger bar electrode 421 are made of the same material, and the top bus bar 422 and the bottom bus bar 422 are made of the same material.

[0085] In some possible embodiments, the bottom finger bar electrode 411 and the top finger bar electrode 421 are made of different materials, and the top bus bar 422 and the bottom bus bar 422 are made of different materials.

[0086] In this embodiment of the application, in order to achieve the connection between the bottom busbar 412 located below the piezoelectric thin film layer 300 and the bottom terminal 413 located above the piezoelectric thin film layer 300 during the fabrication of the top conductor layer, a through hole is formed in the piezoelectric thin film layer 300, and a portion of the bottom terminal 413 is filled into the through hole and made to contact the bottom busbar 412 during the fabrication of the top conductor layer, thereby achieving the connection between the bottom terminal 413 and the bottom busbar 412.

[0087] In some possible embodiments, during the fabrication of the top conductor layer, the vias in the piezoelectric thin film layer 300 are completely filled by the bottom terminal 413, resulting in no more vias in the piezoelectric thin film layer 300 in the final acoustic resonator device.

[0088] In some possible embodiments, during the fabrication of the top conductor layer, the vias in the piezoelectric thin film layer 300 are not completely filled by the bottom terminal 413, resulting in the presence of vias in the piezoelectric thin film layer 300 of the final acoustic resonator device, and the bottom terminal 413 is partially located in the vias and in contact with the bottom busbar 412.

[0089] In this embodiment, the portion of the piezoelectric thin film layer 300, excluding the strip-shaped piezoelectric thin film 301, the etched groove 302, and the bottom terminal 413 located in the piezoelectric thin film layer 300, is attached to the upper surface of the sacrificial layer 200.

[0090] In some possible embodiments, the thickness of the piezoelectric thin film layer 300 is 50-1000 nanometers.

[0091] Optionally, the thickness of the piezoelectric thin film layer 300 is 50 nanometers; optionally, the thickness of the piezoelectric thin film layer 300 is 525 nanometers; optionally, the thickness of the piezoelectric thin film layer 300 is 1000 nanometers.

[0092] In some possible embodiments, the thickness of the strip piezoelectric film 301 is 50-1000 nanometers.

[0093] Optionally, the thickness of the strip piezoelectric film 301 is 50 nanometers; optionally, the thickness of the strip piezoelectric film 301 is 525 nanometers; optionally, the thickness of the strip piezoelectric film 301 is 1000 nanometers.

[0094] In this embodiment, the piezoelectric thin film layer 300 can be made of piezoelectric materials such as lithium niobate, lithium tantalate, or aluminum nitride. Furthermore, it is preferred to select an X-tangential piezoelectric material (especially X-tangential lithium niobate) to form the piezoelectric thin film layer 300, so that the acoustic resonator device can obtain a larger electromechanical coupling coefficient. Figure 1 As shown in the figure, the arrow indicates the direction of the long side of the acoustic resonator device, which lies between the +Y and +Z axes.

[0095] In this embodiment, each strip-shaped piezoelectric film 301 has its corresponding top finger strip electrode 421 and bottom finger strip electrode 411, and each strip-shaped piezoelectric film 301, together with the top finger strip electrode 421 and the bottom finger strip electrode 411, forms a resonator structure. The resonator structure is located in the cavity 201. The bottom finger strip electrode 411 at the bottom of the resonator structure is suspended in the cavity 201, while the top finger strip electrode 421 at the top of the resonator structure is exposed to the external environment. The two sides of the strip-shaped piezoelectric film 301 in the resonator structure are etched grooves 302 communicating with the cavity 201. In the entire acoustic resonator device, the top and bottom surfaces and the left and right sides of each resonator structure are mechanically free interfaces that do not contact other objects.

[0096] In some possible embodiments, the strip piezoelectric film 301 is made of an X-tangential piezoelectric material, with α in its Euler angles (α, 90, -90) ranging from 90 to 180 degrees. Here, the Euler angles are defined using the order (Z, X, Z). The choice of Euler angles is crucial for determining the piezoelectric properties of the material, the electromechanical coupling coefficient, and the overall performance of the acoustic resonator. By optimizing the choice of Euler angles, a better-performing acoustic resonator device can be designed to meet the requirements. In this case, the orientation of the top finger strip electrode 421 and the bottom finger strip electrode 411 in each resonator structure is located between the +Y and +Z axes or between the -Y and -Z axes of the strip piezoelectric film 301.

[0097] In this embodiment, since the density and Young's modulus of the materials used for the top finger electrode 421 and the bottom finger electrode 411 will significantly affect the resonant frequency of the acoustic resonator device, it is necessary to select appropriate materials to prepare the top finger electrode 421 and the bottom finger electrode 411 according to the requirements.

[0098] In some possible embodiments, the top finger electrode 421 and the bottom finger electrode 411 are both made of at least one of aluminum, molybdenum, chromium, gold, platinum, and titanium. Both the top finger electrode 421 and the bottom finger electrode 411 can be composed of one or more layers of conductive material, each layer being aluminum, molybdenum, chromium, gold, platinum, titanium, or a combination thereof. Furthermore, when the uppermost and / or lowermost ends of the top finger electrode 421 and the bottom finger electrode 411 are made of a metallic material such as titanium or chromium, the adhesion between the top finger electrode 421 and the bottom finger electrode 411 and other structures can be improved, increasing power capacity and providing protection for the top finger electrode 421 and the bottom finger electrode 411.

[0099] In this embodiment, the top finger electrode 421 and the bottom finger electrode 411 have identical compositions. Furthermore, the top finger electrode 421 and the bottom finger electrode 411 have the same thickness. By providing the top finger electrode 421 and the bottom finger electrode 411 with the same composition and thickness, clutter modes can be reduced, thereby ensuring the flatness of the passband of the filter composed of this acoustic resonator device.

[0100] Figure 4 This is a schematic diagram of a resonator structure provided in an embodiment of this application, as shown below. Figure 4 As shown, the top finger electrode 421 has a width of Wt, a thickness of Ht, and a length of Lt; the strip-shaped piezoelectric film 301 has a width of Wp, a thickness of Hp, and a length of Lp; the bottom finger electrode 411 has a width of Wb, a thickness of Hb, and a length of Lb. Wt is less than or equal to Wp, and Wp is less than or equal to Wb, meaning the width of the top finger electrode 421 is less than or equal to the width of the strip-shaped piezoelectric film 301, and the width of the strip-shaped piezoelectric film 301 is less than or equal to the width of the bottom finger electrode 411. Both Lt and Lb are less than or equal to Lp, meaning the length of the strip-shaped piezoelectric film 301 is greater than or equal to the length of the bottom finger electrode 411, and the length of the strip-shaped piezoelectric film 301 is greater than or equal to the length of the top finger electrode 421. Figure 3 As shown, the bottom finger bar electrode 411, the top finger bar electrode 421, and the strip-shaped piezoelectric film 301 have an overlapping length, which is defined as the aperture Ap of the resonator structure.

[0101] In this embodiment, the width of the top finger electrode 421, the width of the strip piezoelectric film 301, and the width of the bottom finger electrode 411 are equal. At this time, the transverse cross-section of the resonator structure composed of the top finger electrode 421, the strip piezoelectric film 301, and the bottom finger electrode 411 is as follows: Figure 4 The rectangle shown.

[0102] In some possible embodiments, due to limitations in the fabrication process, the width of the entire resonator structure increases from the top of the top finger electrode 421 to the bottom of the bottom finger electrode 411, causing the shape of the transverse cross-section of the entire resonator structure to no longer be as... Figure 4 Instead of being a rectangle, it is a trapezoid that is narrower at the top and wider at the bottom. Although the width of the entire resonator structure increases from top to bottom, the change in width is so small that the performance of the resonator structure is not adversely affected.

[0103] In this embodiment, the ratio of the sum of the thicknesses of the top finger bar electrode 421, the strip piezoelectric film 301, and the bottom finger bar electrode 411 (i.e., the sum of Ht, Hp, and Hb) to the width Wp of the strip piezoelectric film 301 is in the range of 0.5-1.5.

[0104] In this embodiment, the resonant frequency of the acoustic resonator device is determined by the width and thickness of the stack formed by the top finger bar electrode 421, the strip piezoelectric film 301, and the bottom finger bar electrode 411.

[0105] In this embodiment, the cavity 201 is rectangular. The length of the rectangle is greater than the aperture Ap, and the width of the rectangle is greater than the width Wp of the strip-shaped piezoelectric film 301.

[0106] In some possible embodiments, the sacrificial layer 200 includes at least one cavity 201, and each cavity 201 contains at least one resonator structure. Depending on different requirements, the sacrificial layer 200 can contain a desired number and size of cavities 201, and different cavities 201 can contain the same or different numbers of resonator structures. Figures 1-3 The sacrificial layer 200 in the acoustic resonator device shown includes a cavity 201, and a resonator structure is disposed in the cavity 201.

[0107] In some possible embodiments, when the acoustic resonator device includes multiple resonator structures, the multiple resonator structures are arranged side by side, and the distance between any two adjacent resonator structures can be adjusted according to actual needs. All resonator structures can be arranged in a parallel or non-parallel manner.

[0108] In some possible embodiments, when multiple resonator structures are provided in the acoustic resonator device, all resonator structures are of the same size, that is, the strip piezoelectric film 301, bottom finger strip electrode 411 and top finger strip electrode 421 in all resonator structures are of the same size.

[0109] In this embodiment, the top terminal 423, which is in contact with the top busbar 422, and the bottom terminal 413, which is in contact with the bottom electrode busbar 311, are radio frequency terminals of the resonator structure, on which radio frequency signals required for the target mode of the acoustic resonator device can be applied.

[0110] In this embodiment, the target mode of the acoustic resonator device is a double-shear body acoustic wave excited by a vertical electric field. This double-shear body acoustic wave is generated by the coupling of a horizontal shear wave and a vertical shear wave. This mode has only half a wavelength in both the thickness and width of the structural cross-section. At least one bottom finger bar electrode 411 and its corresponding top finger bar electrode 421 in the acoustic resonator device are configured to apply a corresponding radio frequency signal to excite the double-shear body acoustic wave in the corresponding strip piezoelectric film 301. The resonator structure composed of the finger bar electrode 421, the strip piezoelectric film 301, and the bottom finger bar electrode 411 provides the necessary condition for the double-shear body acoustic wave to have four mechanically free interfaces in the structural cross-section. When the horizontal shear wave and the vertical shear wave have the same resonant frequency for a resonator structure of a specific size, the electromechanical coupling coefficient of the double-shear body acoustic wave reaches its maximum value.

[0111] Figure 5 This application provides a top-view structural diagram of an acoustic resonator device comprising multiple resonator structures. Figure 6 This is a schematic diagram of the transverse cross-section of an acoustic resonator device including multiple resonator structures provided in an embodiment of this application. Figure 6 yes Figure 5 A schematic diagram of the cross-section CC of the structure shown.

[0112] In the embodiments of this application, such as Figure 5 and Figure 6 As shown, the acoustic resonator device has multiple resonator structures arranged in parallel, each resonator structure consisting of a top finger bar electrode 421 ( Figure 6 There are 6 top finger strip electrodes 421, the serial number indicates one of them), and strip-shaped piezoelectric film 301 ( Figure 6 There are 6 strip-shaped piezoelectric films 301 (the serial number indicates one of them) and bottom finger strip electrodes 411 ( Figure 6 It consists of 6 bottom finger strip electrodes 411 (the serial number indicates one of them). By setting multiple resonator structures in the acoustic resonator device, the capacitance requirements of the RF filter composed of this acoustic resonator device can be met, thereby meeting the impedance requirements of the RF filter.

[0113] This application provides a method for forming an acoustic resonator device. Figure 7 This is a schematic flowchart illustrating a method for forming an acoustic resonator device according to an embodiment of this application. Figure 7 As shown, this flowchart includes at least the following steps S701-S705:

[0114] In step S701, a bonding body is provided; the bonding body includes a substrate layer, a sacrificial layer on the substrate layer, an initial bottom conductor layer in the sacrificial layer, and a piezoelectric thin film layer on the sacrificial layer and the initial bottom conductor layer; the initial bottom conductor layer includes a bottom busbar and a bottom finger electrode portion.

[0115] Figure 8 This is a schematic diagram of the formation process of an acoustic resonator device provided in an embodiment of this application. Figure 1 ,like Figure 8 As shown, the composite includes a substrate layer 100, a sacrificial layer 200 located on the substrate layer 100, an initial bottom conductor layer 410 located in the sacrificial layer 200, and a piezoelectric thin film layer 300 located on the sacrificial layer 200. The initial bottom conductor layer 410 includes a bottom busbar and a bottom finger electrode portion.

[0116] Figure 9 This is a flowchart illustrating a method for forming an assembly according to an embodiment of this application, as shown below. Figure 9 As shown, this flowchart includes at least the following steps S901-S906:

[0117] In step S901, a transfer substrate layer and a piezoelectric thin film layer are provided.

[0118] In this embodiment, the transfer substrate layer 500 includes a silicon material layer and a thin silicon dioxide layer on the silicon material layer. The piezoelectric thin film layer 300 is made of a piezoelectric material such as lithium niobate, lithium tantalate, or aluminum nitride.

[0119] In some possible embodiments, the material of the transfer substrate layer 500 may also be other combinations of materials that can be bonded to the piezoelectric thin film layer 300 and stripped by etching or other processes.

[0120] In some possible embodiments, the material of the piezoelectric thin film layer 300 may also be other single-crystal piezoelectric materials with excellent performance in terms of electromechanical coupling coefficient and quality factor.

[0121] In step S902, the substrate layer and the piezoelectric thin film layer are bonded and transferred.

[0122] Figure 10 This is a schematic diagram of the formation process of an acoustic resonator device provided in an embodiment of this application. Figure 2 .

[0123] In this embodiment, the surfaces to be bonded in the transfer substrate layer 500 and the piezoelectric thin film layer 300 are first polished, and then the transfer substrate layer 500 and the piezoelectric thin film layer 300 are bonded using a wafer bonding process to obtain the desired result. Figure 10 The structure shown includes a transfer substrate layer 500 and a piezoelectric thin film layer 300 located on the transfer substrate layer 500.

[0124] In step S903, an initial bottom conductor layer is formed on the piezoelectric thin film layer.

[0125] Figure 11 This is a schematic diagram of the formation process of an acoustic resonator device provided in an embodiment of this application. Figure 3 .

[0126] In the embodiments of this application, as shown in... Figure 10 Based on the structure shown, a piezoelectric thin film layer 300 is formed on its upper surface using a deposition / stripping process. Figure 11 The structure shown is the initial bottom conductor layer 410. The structure within the dashed box is the initial bottom conductor layer 410 from a top view. The initial bottom conductor layer 410 includes a bottom busbar 412 and a bottom finger electrode portion 414 that are in contact with each other. The bottom finger electrode portion 414 is patterned in subsequent operations to form at least one bottom finger electrode 411.

[0127] In some possible embodiments, the initial bottom conductor layer 410 is at least one of aluminum, molybdenum, chromium, gold, platinum, and titanium. The initial bottom conductor layer 410 may consist of one or more layers of conductive material, each layer being a material such as aluminum, molybdenum, chromium, gold, platinum, and titanium, or a combination thereof.

[0128] In step S904, a sacrificial layer is formed on the initial bottom conductor layer and the piezoelectric thin film layer not covered by the initial bottom conductor layer.

[0129] Figure 12 This is a schematic diagram of the formation process of an acoustic resonator device provided in an embodiment of this application. Figure 4 .

[0130] In the embodiments of this application, as shown in... Figure 11 Based on the structure shown, a sacrificial material is deposited on the initial bottom conductor layer 410 and the piezoelectric thin film layer 300 not covered by the initial bottom conductor layer 410 using a deposition process. The sacrificial material is then polished to planarize its surface, resulting in the structure shown. Figure 12 The sacrificial layer 200 in the structure shown.

[0131] In this embodiment, the material of the sacrificial layer 200 is silicon or silicon dioxide.

[0132] In step S905, the upper interface of the sacrificial layer is bonded to the substrate layer.

[0133] Figure 13 This is a schematic diagram of the formation process of an acoustic resonator device provided in an embodiment of this application. Figure 5 .

[0134] In this embodiment of the application, as follows Figure 12The structure shown is inverted and then bonded together using a wafer bonding process. Figure 12 In the structure shown, the sacrificial layer 200 is bonded to the substrate layer 100 to obtain the structure shown. Figure 13 The structure shown.

[0135] In this embodiment, the substrate layer 100 can be a single-layer structure composed of silicon or silicon dioxide, or a stacked structure composed of at least two of silicon, silicon carbide, sapphire or silicon dioxide.

[0136] In step S906, the transfer substrate layer is removed to obtain the composite.

[0137] In the embodiments of this application, as shown in... Figure 13 Based on the structure shown, the silicon material in the transfer substrate 500 is removed by a grinding process, and the silicon dioxide material in the transfer substrate 500 is removed by a chemical reagent that reacts with silicon dioxide. This process removes the transfer substrate 500, resulting in the structure shown. Figure 8 The combination shown.

[0138] By following the steps S901-S906 above, the result provided in this application can be obtained. Figure 8 The combination shown.

[0139] In step S702, the piezoelectric thin film layer is etched to form a through hole to expose part of the bottom busbar.

[0140] Figure 14 This is a schematic diagram of the formation process of an acoustic resonator device provided in an embodiment of this application. Figure 6 .like Figure 14 The structural diagram shown is a longitudinal cross-sectional view of the structure.

[0141] In the embodiments of this application, as shown in... Figure 8 Based on the structure shown, the piezoelectric thin film layer 300 on the bottom busbar 412 in the initial bottom conductor layer 410 is etched. By removing a portion of the piezoelectric thin film layer 300 located on the bottom busbar 412, a structure such as... can be formed in the piezoelectric thin film layer 300. Figure 14 The through-hole 303 in the structure shown exposes the bottom busbar 412 located below the piezoelectric thin film layer 300, so that the bottom busbar 412 located below the piezoelectric thin film layer 300 can be contacted and connected to the bottom terminal 413 located above the piezoelectric thin film layer 300 in subsequent processes.

[0142] In this embodiment, the through hole 303 does not need to be too large; it is sufficient to expose the bottom busbar 412.

[0143] In some possible embodiments, a dry etching process is used to remove a portion of the piezoelectric thin film layer 300 to form a via 303. Alternatively, a selective wet etching process using an isotropic etchant is used to remove a portion of the piezoelectric thin film layer 300 to form a via 303.

[0144] In step S703, an initial top conductor layer is formed on the remaining piezoelectric thin film layer; the initial top conductor layer includes a top terminal, a bottom terminal, a top busbar, and a top finger electrode portion, the bottom terminal fills the through hole and contacts the bottom busbar, and the top terminal contacts the top busbar.

[0145] Figures 15-17 This is a schematic diagram of the formation process of an acoustic resonator device provided in an embodiment of this application. Figures 7-9 .in, Figures 15-17 These are schematic diagrams of the same structure from different perspectives. Figure 15 This is a schematic diagram of the structure from a top view. Figure 16 A schematic diagram of the transverse cross-section of the structure (also) Figure 15 (A schematic diagram of the cross section AA of the structure shown). Figure 17 A schematic diagram of the longitudinal section of the structure (also) Figure 15 (Schematic diagram of the cross section BB of the structure shown).

[0146] In the embodiments of this application, as shown in... Figure 14 Based on the structure shown, a piezoelectric thin film layer 300 is formed on its upper surface using a deposition / stripping process. Figures 15-17 The structure shown includes an initial top conductor layer 420, which comprises a top terminal 423, a bottom terminal 413, a top busbar 422, and a top finger electrode portion 424. The two ends of the top busbar 422 are in contact with the top terminal 423 and the top finger electrode portion 424, respectively. The top finger electrode portion 424 is patterned in subsequent operations to form at least one top finger electrode 421. Since the bottom terminal 413 is formed above the through-hole 303 formed in step S702 by etching the piezoelectric thin film layer 300, a portion of the bottom terminal 413 fills the through-hole 303 and contacts the bottom busbar 412, thereby achieving the connection between the bottom terminal 413 and the bottom busbar 412.

[0147] In some possible embodiments, the via 303 is completely filled by the bottom terminal 413, resulting in no more via 303 in the piezoelectric thin film layer 300.

[0148] In some possible embodiments, the through hole 303 is not completely filled by the bottom terminal 413, resulting in the presence of the through hole 303 in the piezoelectric thin film layer 300, and the portion of the bottom terminal 413 located in the through hole 303 is in contact with the bottom busbar 412.

[0149] In this embodiment, the bottom conductor material and the top conductor material have the same composition. That is, the composition of the top terminal 423, bottom terminal 413, top busbar 422, and top finger electrode portion 424 formed by the top conductor material is exactly the same as the composition of the bottom busbar 412 and bottom finger electrode portion 414 formed by the bottom conductor material. Moreover, the top finger electrode portion 424 and the bottom finger electrode portion 414 have the same thickness.

[0150] In some possible embodiments, the initial top conductor layer 420 is made of at least one of aluminum, molybdenum, chromium, gold, platinum, and titanium. The initial top conductor layer 420 may consist of one or more layers of conductive material, each layer being a material such as aluminum, molybdenum, chromium, gold, platinum, and titanium, or a combination thereof.

[0151] In step S704, the stack consisting of the bottom finger bar electrode, the piezoelectric thin film layer, and the top finger bar electrode is etched to obtain at least one resonator structure arranged in parallel and etching grooves located on both sides of each resonator structure; each resonator structure includes a top finger bar electrode, a strip-shaped piezoelectric thin film, and a bottom finger bar electrode, the top finger bar electrode is connected to the top electrode busbar, and the bottom finger bar electrode is connected to the bottom busbar.

[0152] Figure 18 This is a schematic diagram of the formation process of an acoustic resonator device provided in an embodiment of this application. Figure 10 .

[0153] In the embodiments of this application, as shown in... Figures 15-17 Based on the structure shown, the stack consisting of the bottom finger electrode portion 410, the piezoelectric thin film layer 300, and the top finger electrode portion 420 is etched using a dry etching process or an etching process with high verticality to form a structure as shown. Figure 18 At least one resonator structure arranged in parallel in the structure shown ( Figure 18 There is one resonator structure and etching grooves 302 located on both sides of each resonator structure. Each resonator structure includes a top finger electrode 421, a strip-shaped piezoelectric film 301, and a bottom finger electrode 411, with the top finger electrode 421 connected to a top busbar 422 and the bottom finger electrode 411 connected to a bottom busbar 421. The presence of etching grooves 302 provides mechanically free interfaces on both sides of the top finger electrode 421, the strip-shaped piezoelectric film 301, and the bottom finger electrode 411 in the resonator structure, which helps the acoustic resonator device to be excited by a vertical electric field and generate double shear body acoustic waves. Moreover, the etching grooves 302 facilitate the etching of the sacrificial layer 200 in subsequent steps to form a cavity 201 in the sacrificial layer 200.

[0154] In step S705, a portion of the sacrificial layer located below the bottom finger electrode is removed to form a cavity, thereby obtaining an acoustic resonator device; the resonator structure is suspended in the cavity.

[0155] In this embodiment, an isotropic etchant is used to etch the sacrificial layer 200 from the location of the etching trench 302, removing a portion of the sacrificial layer 200 located below the bottom finger electrode 411 in the etching trench 302 and each resonator structure, forming a... Figure 2 and Figure 3 The cavity 201 in the structure shown. By forming the cavity 201 in the sacrificial layer 200, the bottom finger electrode 411 is suspended in the cavity 201, resulting in the structure shown. Figures 1-3 The acoustic resonator device shown.

[0156] In this embodiment of the application, a sacrificial layer 200 of a certain thickness is still retained below the cavity 201.

[0157] In some possible embodiments, the cavity 201 extends vertically through the sacrificial layer 200 and communicates with the substrate layer 100. In some cases, the cavity 201 may also extend vertically into the substrate layer 100, or even extend vertically through the substrate layer 100.

[0158] In some possible embodiments, the cavity 201 can be of different shapes, such as a rectangle, a rounded rectangle, or an irregular polygon.

[0159] In this embodiment of the application, the acoustic resonator device provided by the present application can be obtained through the above steps S701-S705.

[0160] This application also provides a radio frequency filter. The radio frequency filter includes multiple acoustic resonator devices provided in this application. The structure of each acoustic resonator device is as follows: Figures 1-3 As shown.

[0161] In this embodiment, multiple acoustic resonator devices in the radio frequency filter are interconnected to form multiple series resonators and multiple parallel resonators required for the topology of the radio frequency filter. The number of acoustic resonator devices and their connection method can be adjusted according to different frequency requirements or other needs of the radio frequency filter.

[0162] In some possible embodiments, in an RF filter composed of multiple acoustic resonator devices, when the thickness of the top finger electrode 421, the thickness of the strip piezoelectric film 301, and the thickness of the bottom finger electrode 411 are the same in all acoustic resonator devices, an RF filter with a preset frequency band can be obtained by adjusting the width of the top finger electrode 421, the width of the strip piezoelectric film 301, and the width of the bottom finger electrode 411 in each acoustic resonator device. Specifically, the width of the top finger electrode 421 in a parallel resonator is greater than the width of the top finger electrode 421 in a series resonator, the width of the strip piezoelectric film 301 in a parallel resonator is greater than the width of the strip piezoelectric film 301 in a series resonator, and the width of the bottom finger electrode 411 in a parallel resonator is greater than the width of the bottom finger electrode 411 in a series resonator.

[0163] In some possible embodiments, the multiple acoustic resonator devices in the radio frequency filter may have the same or different material compositions and dimensions. Each acoustic resonator device may include one or more resonator structures. The composition, materials, and dimensions of the acoustic resonator devices can be adjusted according to different frequency requirements or other requirements of the radio frequency filter.

[0164] Figure 19 This is a schematic diagram of the displacement of the main resonant mode of an acoustic resonator device provided in an embodiment of this application. The contour lines are used to represent the displacement distribution, and the arrows represent the direction and magnitude of the total displacement.

[0165] In the embodiments of this application, such as Figure 19 As shown, when a radio frequency signal is applied to the bottom finger strip electrode 411 and the top finger strip electrode 421 through the bottom terminal 413 and the top terminal 423 respectively, an alternating electric field is formed in the vertical direction of the strip piezoelectric film 301. Figure 19 As shown by the contour lines, relying on the strip-shaped piezoelectric film 301, the electric field simultaneously generates horizontal shear waves (i.e., horizontal shear waves) and vertical shear waves (i.e., vertical shear waves) in the strip structure composed of the bottom finger strip electrode 411, the strip-shaped piezoelectric film 301, and the top finger strip electrode 421. Shear deformation is defined as the structure being divided into two parts along a plane, with the two parts undergoing relative translational displacement along that plane. Since two mutually perpendicular shear deformations are generated simultaneously in the resonator structure, the coupling of the two shear deformations causes the displacement to mainly occur at the four corners. The shear stress located at the center of the structure causes the four corners to deform towards or away from the center.

[0166] In this embodiment, to simultaneously excite horizontal and vertical shear waves, the thickness and width of the resonator structure must simultaneously satisfy the excitation condition of horizontal and vertical shear waves at the same frequency. This results in the acoustic resonator device provided in this application, which generates dual-shear body acoustic waves through vertical electric field excitation, differing from existing surface acoustic wave resonators or transversely excited acoustic resonators. Specifically, the wave vector of the target mode in the acoustic resonator device provided in this application has components in both the horizontal and vertical directions. The target mode in the acoustic resonator device provided in this application does not use a multi-periodic structure in the horizontal direction; only half a wavelength exists in both the horizontal and vertical directions to avoid high-order mode coupling interference with low-order dominant modes in these two directions. To generate dual-shear body acoustic waves through vertical electric field excitation in this acoustic resonator device, the upper and lower bottom surfaces and the left and right sides of the resonator structure must be mechanically free interfaces.

[0167] In this embodiment, the bottom finger electrode 411 and top finger electrode 421 in the acoustic resonator device also strongly participate in the resonant mode (i.e., generating double-shear acoustic waves by vertical electric field excitation). Due to the characteristics of this resonant mode, the width and thickness of the resonator structure affect the resonant frequency. This allows for the creation of different acoustic resonator devices spanning a large frequency range by simply changing the width of the resonator structure without altering its thickness, for a specific frequency band. This feature simplifies the manufacturing process; unlike laterally excited Lamb wave resonators, it eliminates the need for an additional dielectric layer to adjust the frequency. Frequency adjustment can be achieved simply by adjusting the width of the resonator structure in a single photolithography process.

[0168] In this embodiment, compared with thin-film bulk acoustic resonators and solid-mount acoustic resonators in the prior art, the acoustic resonator device provided in this application has a larger coupling coefficient (>30%), and can also obtain strip-shaped piezoelectric films 301 of different widths by photolithography process to obtain etching grooves 302 of different widths in one step, thereby obtaining acoustic resonator devices with different resonant frequencies.

[0169] In this embodiment, the acoustic resonator device provided in this application also possesses the advantage of frequency adjustment compared to a transversely excited Lamb wave resonator capable of frequency adjustment. Simultaneously, due to the use of a stacked structure of top finger strip electrode 421, strip-shaped piezoelectric film 301, and bottom finger strip electrode 411, the acoustic resonator device in this application has a significantly larger capacitance per unit area compared to a transversely excited Lamb wave resonator. This provides a significant advantage in impedance matching of the RF filter, contributing to a substantial reduction in the area of ​​the RF filter. Compared to conventional surface acoustic wave resonators, the acoustic resonator device in this application, due to the use of a resonator structure suspended in the cavity 201 of the sacrificial layer 200, is freed from the sound velocity limitations in the substrate layer 100. This acoustic resonator device is more suitable for high-frequency applications and has the advantage of a small area.

[0170] Figure 20 This is a schematic diagram of the finite element simulation admittance curve of an acoustic resonator device provided in an embodiment of this application. In this simulation, the structure of the acoustic resonator device is as follows: Figures 1-3 As shown, the strip-shaped piezoelectric thin film 301 is made of X-tangential single-crystal lithium niobate, the bottom finger electrode 411 and the top finger electrode 421 are both made of copper, and the substrate layer 100 is made of silicon. The thickness Hp of the strip-shaped piezoelectric thin film 301 is 200 nm, the width Wp of the strip-shaped piezoelectric thin film 301 is 400 nm, the thickness Ht of the top finger electrode 421 is 100 nm, and the thickness Hb of the bottom finger electrode 411 is 100 nm. Figure 20 As shown, the resonant frequency of this acoustic resonator device is 4180 MHz, the anti-resonator frequency is 4860 MHz, the frequency difference between the two resonators is 680 MHz, and its electromechanical coupling coefficient is 43%. Here, the resonant frequency is the frequency corresponding to the maximum point of the admittance curve, the anti-resonant frequency is the frequency corresponding to the minimum point of the admittance curve, and the electromechanical coupling coefficient is the relative distance between the anti-resonant frequency and the resonant frequency. The larger the electromechanical coupling coefficient of the acoustic resonator device, the larger the upper limit of the bandwidth of the RF filter fabricated from the acoustic resonator device. This acoustic resonator device exhibits clean admittance characteristics and a large coupling coefficient in the frequency range of 2.5 GHz to 6 GHz, which allows it to meet the large bandwidth requirements in the definition of communication frequency bands.

[0171] Figure 21 This is a schematic diagram of the finite element simulation admittance curves of an acoustic resonator device using strip-shaped piezoelectric films of different widths, provided in an embodiment of this application. The constituent materials of each structure in the acoustic resonator device used in this simulation are similar to... Figure 20The acoustic resonator devices used in the corresponding simulations all use the same materials for their various structures. In this simulation, the thickness Hp of the strip piezoelectric film 301 is 300 nm, the thickness Ht of the top finger strip electrode 421 is 100 nm, and the thickness Hb of the bottom finger strip electrode 411 is 100 nm. This simulation uses acoustic resonator devices with strip piezoelectric film 301 widths Wp of 300 nm, 400 nm, and 500 nm. The acoustic resonator devices with strip piezoelectric film 301 widths of 300 nm, 400 nm, and 500 nm have resonant frequencies of 5440 MHz, 4720 MHz, and 3980 MHz, respectively, anti-resonant frequencies of 5960 MHz, 5600 MHz, and 4760 MHz, and electromechanical coupling coefficients of 25%, 50%, and 53%, respectively. Therefore, it can be seen that by increasing the width of the strip piezoelectric film 301 in the acoustic resonator device, the resonant frequency of the acoustic resonator device gradually decreases, the anti-resonant frequency gradually increases, and the electromechanical coupling coefficient gradually increases. By adjusting the width of the strip piezoelectric film 301 between 300 nm and 500 nm, a width adjustment range of 200 nm corresponds to a resonant frequency covering a frequency range of 1460 MHz.

[0172] Figure 22 This is a schematic diagram illustrating the resonant frequencies of an acoustic resonator device using strip-shaped piezoelectric films of different widths for top and bottom finger electrodes made of different materials, as provided in an embodiment of this application. In this simulation, the structure of the acoustic resonator device is as follows: Figures 1-3 As shown, the strip-shaped piezoelectric thin film 301 is made of X-cut single-crystal lithium niobate, the top finger electrode 421 and the bottom finger electrode 411 are made of copper or aluminum, and the second substrate layer 103 in the substrate layer 100 is made of silicon. The thickness Hp of the strip-shaped piezoelectric thin film 301 is 300 nm, the thickness Ht of the top finger electrode 421 is 100 nm, the thickness Hb of the bottom finger electrode 411 is 100 nm, and the width Wp of the strip-shaped piezoelectric thin film 301 increases from 200 nm to 1000 nm in successive increments of 100 nm.

[0173] In the embodiments of this application, such as Figure 22 As shown by the solid line, when both the top finger electrode 421 and the bottom finger electrode 411 are made of copper, and when the width Wp of the strip piezoelectric film 301 increases by 100 nanometers from 200 nanometers to 1000 nanometers, the corresponding resonant frequencies of the acoustic resonator devices are 5440 MHz, 4720 MHz, 3980 MHz, 3500 MHz, 3200 MHz, 2930 MHz, 2760 MHz, 2600 MHz, and 2435 MHz, respectively. Figure 22As shown by the dashed lines, when both the top finger electrode 421 and the bottom finger electrode 411 are made of aluminum, and when the width Wp of the strip piezoelectric film 301 increases by 100 nanometers from 200 nanometers to 1000 nanometers, the resonant frequencies are 7080 MHz, 6320 MHz, 5340 MHz, 4760 MHz, 4320 MHz, 4020 MHz, 3760 MHz, 3480 MHz, and 3200 MHz, respectively. Regardless of whether the top finger electrode 421 and the bottom finger electrode 411 are made of copper or aluminum, the resonant frequency of the acoustic resonator device decreases with the increase of the width Wp of the strip piezoelectric film 301. Because copper has a higher material density than aluminum, the acoustic resonator device with copper top finger electrodes 421 and bottom finger electrodes 411 has a larger mass load, resulting in a lower resonant frequency than the acoustic resonator device with aluminum top finger electrodes 421 and bottom finger electrodes 411.

[0174] Figure 23 This is a schematic diagram of a radio frequency filter including multiple acoustic resonator devices provided in an embodiment of this application, as shown below. Figure 23 As shown, this RF filter has a traditional trapezoidal filter structure, comprising three series-connected acoustic resonator devices and two parallel-connected acoustic resonator devices. The three series-connected acoustic resonator devices are Rs1, Rs2, and Rs3, connected between two ports, labeled "IN" and "OUT" respectively. The two parallel-connected acoustic resonator devices Rp are connected between the two series-connected acoustic resonator devices (Rs1 and Rs2) and the ground port GND, respectively.

[0175] Figure 24 This is a schematic diagram of the admittance curve of an acoustic resonator device in a radio frequency filter that includes multiple acoustic resonator devices, as provided in an embodiment of this application. Figure 24 The corresponding radio frequency filter is Figure 23 The radio frequency filter shown is described below. The structure of the acoustic resonator device (Rs1, Rs2, and Rp) in the radio frequency filter is as follows: Figures 1-3 As shown, the strip-shaped piezoelectric thin film 301 is made of X-cut single-crystal lithium niobate, the top finger electrode 421 and the bottom finger electrode 411 are both made of copper, and the substrate layer 100 is made of silicon. The thickness Hp of the strip-shaped piezoelectric thin film 301 is 300 nm, the thickness Ht of the top finger electrode 421 is 100 nm, and the thickness Hb of the bottom finger electrode 411 is 100 nm. The width Wp of the strip-shaped piezoelectric thin film 301 in the acoustic resonator device Rs1 is 340 nm, the width Wp of the strip-shaped piezoelectric thin film 301 in the acoustic resonator device Rs2 is 320 nm, and the width Wp of the acoustic resonator device Rp is 440 nm. Figure 24As shown, the resonant frequencies of the acoustic resonator devices Rs1, Rs2, and Rp are 4400MHz, 4560MHz, and 3775MHz, respectively, and their anti-resonant frequencies are 5251MHz, 5436MHz, and 4500MHz, respectively. Their electromechanical coupling coefficients are 52.3%, 52.0%, and 52.0%, respectively. Therefore, when the thicknesses of the top finger electrode 421, the strip piezoelectric film 301, and the bottom finger electrode 411 in the multiple acoustic resonator devices of the RF filter are all equal, the filter topology requirements can be met simply by adjusting the width of the strip piezoelectric film 301, without affecting the electromechanical coupling coefficient performance.

[0176] Figure 25 This is a schematic diagram of the insertion loss curve of an acoustic resonator device in an RF filter that includes multiple acoustic resonator devices, provided in an embodiment of this application. Figure 25 The corresponding radio frequency filter is Figure 23 The RF filter shown is an example. The insertion loss curve of an RF filter is the S21 curve, a crucial parameter describing its performance. The S21 curve represents the ratio in decibels (dB) between the output port signal power and the input port signal power after the signal passes through the RF filter. Figure 25 As shown, this RF filter has a 3dB bandwidth of 855 MHz, a center frequency of 4558 MHz, and a fractional bandwidth of 19%. The 3dB bandwidth is the frequency range corresponding to the power drop to half of the maximum power (or a 3dB gain drop) in the S21 curve; the center frequency is the center frequency point of the 3dB bandwidth; and the fractional bandwidth is the ratio of the 3dB bandwidth to the center frequency. Because this RF filter has a relatively large fractional bandwidth, it can allow a wide frequency range to pass through.

[0177] In this embodiment, a stacked structure of a suspended top finger electrode 421, a strip-shaped piezoelectric film 301, and a bottom finger electrode 411 is provided in the device to support the dual-shear body acoustic wave mode excited by a vertical electric field. The acoustic resonator based on this mode has a high coupling coefficient and high frequency, making it suitable for the higher frequency and wider bandwidth requirements of RF filters in the widely adopted 5G communication and future 6G communication standards.

[0178] It should be noted that the order of the embodiments described above is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. Furthermore, specific embodiments have been described above. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps described in the claims can be performed in a different order than that shown in the embodiments and still achieve the desired result. Additionally, the processes depicted in the drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0179] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the device embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0180] Those skilled in the art will understand that all or part of the steps of the above embodiments can be implemented by hardware or by a program instructing related hardware. The program can be stored in a computer-readable storage medium, such as a read-only memory, a disk, or an optical disk.

[0181] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An acoustic resonator device, comprising: include: Substrate layer; A sacrificial layer is located on the substrate layer; the sacrificial layer includes at least one cavity; A piezoelectric thin film layer is located on the sacrificial layer; the piezoelectric thin film layer includes at least one parallel strip-shaped piezoelectric thin film and etching grooves located on both sides of each strip-shaped piezoelectric thin film; the etching grooves communicate with the cavity; The bottom conductor layer located beneath the piezoelectric thin film layer; The bottom conductor layer is in contact with the strip-shaped piezoelectric film; the bottom conductor layer includes a bottom busbar and at least one bottom finger electrode, the at least one bottom finger electrode being connected to the bottom busbar; the bottom finger electrode is suspended in the cavity; the bottom finger electrode and the strip-shaped piezoelectric film correspond one-to-one; A top conductor layer is located on the piezoelectric thin film layer; the top conductor layer is in contact with the strip-shaped piezoelectric thin film; the top conductor layer includes a top busbar, a top terminal, a bottom terminal, and at least one top finger electrode; one end of the top busbar is connected to the top terminal, and the other end is connected to the at least one top finger electrode; the bottom terminal portion is located in the piezoelectric thin film layer and contacts the bottom busbar; The top finger bar electrode and the strip-shaped piezoelectric film correspond one-to-one; The at least one bottom finger strip electrode and its corresponding top finger strip electrode are configured to apply a corresponding radio frequency signal to excite a double shear body acoustic wave in the corresponding strip-shaped piezoelectric film; the double shear body acoustic wave is generated by coupling a horizontal shear wave and a vertical shear wave; the double shear body acoustic wave is excited by a vertical electric field; The top terminal and the bottom terminal are radio frequency (RF) terminals, used to apply an RF signal corresponding to the target mode of the acoustic resonator device.

2. The acoustic resonator device of Claim 1, wherein, The piezoelectric thin film layer includes a through hole; the bottom terminal portion is located in the through hole and contacts the bottom busbar.

3. The acoustic resonator device of Claim 1, wherein, The resonant frequency of the acoustic resonator device is determined by the width and thickness of the stack formed by the top finger electrode, the strip piezoelectric film, and the bottom finger electrode.

4. The acoustic resonator device of Claim 1, wherein, The width of the strip-shaped piezoelectric film is less than or equal to the width of the bottom finger strip electrode, and the length of the strip-shaped piezoelectric film is greater than or equal to the length of the bottom finger strip electrode; The width of the strip-shaped piezoelectric film is greater than or equal to the width of the top finger strip electrode, and the length of the strip-shaped piezoelectric film is greater than or equal to the length of the top finger strip electrode.

5. The acoustic resonator device of Claim 1, wherein, The ratio of the sum of the thicknesses of the top finger electrode, the strip-shaped piezoelectric film, and the bottom finger electrode to the width of the strip-shaped piezoelectric film ranges from 0.5 to 1.

5.

6. The acoustic resonator device of Claim 1, wherein, The piezoelectric thin film layer is made of at least one of lithium niobate, lithium tantalate, and aluminum nitride; the thickness of the piezoelectric thin film is 50-1000 nanometers. The material of the top conductor layer is at least one of aluminum, molybdenum, chromium, gold, platinum and titanium; The material of the bottom conductor layer is at least one of aluminum, molybdenum, chromium, gold, platinum and titanium.

7. The acoustic resonator device of Claim 1, wherein, The substrate layer is a single-layer structure composed of silicon or silicon dioxide; Alternatively, the substrate layer is a stacked structure composed of at least two materials selected from silicon, silicon carbide, sapphire, or silicon dioxide.

8. The acoustic resonator device of Claim 1, wherein, The material of the sacrificial layer is silicon or silicon dioxide.

9. A radio frequency filter, characterized by, Includes multiple acoustic resonator devices as described in any one of claims 1 to 8; The plurality of acoustic resonator devices are interconnected to form a plurality of series resonators and a plurality of parallel resonators required by a topology of the radio frequency filter; when the thickness of the top IDT electrode, the thickness of the strip-shaped piezoelectric thin film and the thickness of the bottom IDT electrode in each of the acoustic resonator devices are the same, the radio frequency filter of a preset frequency band is obtained by adjusting the width of the top IDT electrode, the width of the strip-shaped piezoelectric thin film and the width of the bottom IDT electrode, and the width in the parallel resonators is greater than the width in the series resonators.

10. A method of forming an acoustic wave resonator device, characterized by, Comprise: Provide a combination; The combination comprises a substrate layer, a sacrificial layer located on the substrate layer, an initial bottom conductor layer located in the sacrificial layer, and a piezoelectric thin film layer located on the sacrificial layer and the initial bottom conductor layer; The initial bottom conductor layer comprises a bottom bus bar and a bottom IDT electrode part; Etching the piezoelectric thin film layer forms a through hole to expose part of the bottom bus bar; Form an initial top conductor layer on the remaining piezoelectric thin film layer; the initial top conductor layer comprises a top terminal, a bottom terminal, a top bus bar and a top IDT electrode part, the bottom terminal fills the through hole and contacts the bottom bus bar, and the top terminal contacts the top bus bar; The etching process is performed on the stack of the bottom IDT electrode part, the piezoelectric thin film layer and the top IDT electrode part to obtain at least one parallelly arranged resonator structure and etching grooves located on both sides of each resonator structure; each resonator structure comprises a top IDT electrode, a strip-shaped piezoelectric thin film and a bottom IDT electrode, the top IDT electrode is connected to the top bus bar, and the bottom IDT electrode is connected to the bottom bus bar; Part of the sacrificial layer located below the bottom IDT electrode is removed to form a cavity to obtain an acoustic resonator device; the resonator structure is suspended in the cavity; The at least one bottom IDT electrode and its corresponding top IDT electrode are configured to apply a corresponding radio frequency signal to excite a corresponding double shear bulk acoustic wave in the strip-shaped piezoelectric thin film; the double shear bulk acoustic wave is generated by coupling horizontal shear waves and vertical shear waves; the double shear bulk acoustic wave is excited by a vertical electric field; The top terminal and the bottom terminal are radio frequency terminals for being applied with a radio frequency signal corresponding to a target mode of the acoustic resonator device.

11. The method of forming an acoustic resonator device of claim 10, wherein, The combination comprises: Providing a transfer substrate layer and the piezoelectric thin film layer; Bonding the transfer substrate layer and the piezoelectric thin film layer; Forming the initial bottom conductor layer on the piezoelectric thin film layer; Forming the sacrificial layer on the initial bottom conductor layer and the piezoelectric thin film layer not covered by the initial bottom conductor layer; Bonding the upper interface of the sacrificial layer with the substrate layer; Removing the transfer substrate layer to obtain the combination.

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