acoustic resonator

Abstract

An acoustic resonator (100) provides high-voltage electrical coupling and exhibits improved power handling characteristics and Q factor at the resonant frequency. The acoustic resonator (100) includes an interdigital transducer (IDT) (102) formed on a piezoelectric substrate (104). Each staggered finger electrode of the IDT (102) has a multilayer structure comprising a first layer (200) and a second layer (202), the second layer being disposed above the first layer (200) and separated from the first layer (200) by one or more bases (204). The thickness and width of the first layer (200), the second layer (202), and the one or more bases (204) are defined based on the wavelength of the sound wave to be generated by the IDT (102) at the resonant frequency of the acoustic resonator (100). The thickness of the first layer (200) is less than the thickness of each of the one or more bases (204) and the second layer (202), and the width of the one or more bases (204) is less than the width of each of the first layer (200) and the second layer (202).

Description

Technical Field

[0001] This invention generally relates to the field of acoustic devices. Specifically, this invention relates to an acoustic resonator comprising an interdigital transducer (IDT), wherein each staggered finger electrode of the IDT has a multilayer structure, the multilayer structure being designed to improve the quality factor (Q factor), enhance heat dissipation capability, and provide high-voltage electrical coupling at the resonant frequency of the acoustic resonator. Background Technology

[0002] Acoustic resonators can be used to implement signal processing functions in a variety of electronic applications. For example, acoustic resonators are used in existing wireless and wired communication devices, such as mobile phones, to implement frequency filters and / or multiplexers for transmitting and / or receiving wireless and / or wired signals. Some examples of acoustic resonators include different types of surface acoustic wave (SAW) resonators, bulk acoustic wave (BAW) resonators, film bulk acoustic resonators (FBAR), laterally excited bulk acoustic wave resonators (XBAR), transversally excited shear wave resonators (YBAR), stacked bulk acoustic resonators (SBAR), double bulk acoustic resonators (DBAR), and solidly mounted resonators (SMR).

[0003] In SAW resonators, FBARs, XBARs, YBARs, and similar acoustic resonators, electrodes are typically formed on the top surface of a piezoelectric material to transmit signals and generate an electric field within the material for resonant excitation. However, electrodes formed in this way can introduce various problems into the acoustic resonator, namely: excessive resistance, reduced power handling capability, mass loading effects, acoustic attenuation, parasitic modes, etc. More specifically, when electrodes are too thin, they can lead to high electrode resistance, resulting in impedance degradation at the resonant frequency. Furthermore, poor heat dissipation along thin electrodes can cause power handling problems. On the other hand, electrodes that are too thick can cause vibration damping and reduce piezoelectric coupling (due to the lossy nature of their metallic material and the concentration of vibrational energy in the passive (i.e., non-piezoelectric) portion of the resonator structure), and may also (due to mass loading effects) cause a decrease in the resonant frequency of the acoustic resonator. In addition, electrodes of varying thicknesses can also introduce parasitic modes.

[0004] Given the above, further engineering design is needed to improve the characteristics of the electrodes contained in the acoustic resonator. Summary of the Invention

[0005] This invention has briefly introduced some concepts, which will be further described in the specific embodiments below. The purpose of this invention is not to identify its key features, nor to limit its scope.

[0006] The object of the present invention is to provide an acoustic resonator that provides high-voltage electrical coupling and exhibits improved power handling characteristics and Q factor at the resonant frequency (e.g., compared to existing XBAR and YBAR).

[0007] The above-mentioned objectives are achieved by the features of the independent claims in the appended claims. Further embodiments and examples will be apparent from the dependent claims, detailed descriptions, and drawings.

[0008] According to one aspect, an acoustic resonator is provided. The acoustic resonator includes a piezoelectric substrate and an individual digital transducer (IDT), the IDT disposed on the piezoelectric substrate. The IDT includes a set of staggered finger electrodes, each finger electrode serving as a multilayer structure comprising a first layer and a second layer. The second layer is disposed above the first layer and separated from the first layer by at least one base. The thickness and width of each of the first layer, the second layer, and the at least one base are defined based on the wavelength λ of the sound wave to be generated by the IDT in the piezoelectric substrate at the resonant frequency of the acoustic resonator. The thickness of the first layer is less than the thickness of each of the at least one base and the second layer, and the width of the at least one base is less than the width of each of the first layer and the second layer. In this acoustic resonator configuration, the first (bottom) layer, with higher amplitude acoustic vibrations, is responsible for generating an electric field in the piezoelectric substrate, while the second (top) layer, with lower amplitude acoustic vibrations, is responsible for conducting current and removing heat (due to ohmic losses). Thus, the essential function of each finger electrode (or in other words, electrode) is divided between the first and second layers. All of these can achieve the aforementioned goals, namely, to provide high-voltage electrical coupling and to improve power handling characteristics and Q factor at the resonant frequency.

[0009] In one exemplary embodiment, the at least one base of each of the set of staggered finger electrodes includes a single base configured such that a gap is formed between the first layer and the second layer, on either side of the base. In this embodiment, the acoustic resonator can be used as an XBAR.

[0010] In one exemplary embodiment, the base of each of the set of staggered finger electrodes is positioned corresponding to (e.g., adjacent or neighboring) a node of the acoustic wave. By positioning the base in this manner, the transmission of acoustic vibrations from the piezoelectric substrate to the second layer of each of the set of staggered finger electrodes can be minimized.

[0011] In one exemplary embodiment, the at least one base of each of the set of staggered finger electrodes includes two bases spaced apart from each other, such that a closed gap is formed between the two bases and each of the first and second layers. In this embodiment, the acoustic resonator can be used as a YBAR.

[0012] In one exemplary embodiment, each of the two bases of each of the set of staggered finger electrodes is positioned corresponding to (e.g., adjacent or neighboring) the node of the acoustic wave. By positioning the bases in this manner, the transmission of vibrations from the piezoelectric substrate to the second layer of each of the set of staggered finger electrodes can be minimized.

[0013] In one exemplary embodiment, the gap (between the first and second layers) is filled with a material whose acoustic impedance is at least three times lower than that of each of the set of staggered finger electrodes. This simplifies the manufacturing process of the acoustic resonator and strengthens the multilayer structure of each of the set of staggered finger electrodes, while ensuring adequate acoustic isolation between the first and second layers.

[0014] In one exemplary embodiment, the first layer is made of a first conductive material, the second layer is made of a second conductive material, and the at least one base is made of a third conductive material. In this embodiment, the first conductive material may be different from or the same as the second conductive material, and the third conductive material may be different from or the same as either the first or second conductive material. Therefore, the structural elements of each finger electrode in the set of staggered finger electrodes can be made of the same or different materials, depending on the specific application. This provides flexibility in the manufacturing process of the acoustic resonator.

[0015] In one exemplary embodiment, the first conductive material has lower acoustic loss compared to the second conductive material; and the second conductive material has higher electrical conductivity and higher thermal conductivity compared to the first conductive material. By using such materials, the aforementioned primary functions of each finger electrode can be better defined between the first and second layers.

[0016] In one exemplary embodiment, the piezoelectric substrate is composed of lithium niobate (LN), lithium tantalate (LT), aluminum scandium nitride (AlScN), and lithium iodate (…). It is made of one of zinc oxide (ZnO) and lead zirconate titanate (PZT). These materials exhibit suitable piezoelectric properties, enabling the acoustic resonator to operate efficiently.

[0017] In one exemplary embodiment, the piezoelectric substrate serves as a layered structure comprising a non-piezoelectric support layer and a piezoelectric thin film disposed on the non-piezoelectric support layer. In this embodiment, the IDT is disposed on the piezoelectric thin film, the thickness of which ranges from 0.1λ to 2λ. In this case, the non-piezoelectric support layer can provide additional mechanical support for the piezoelectric thin film, which can be bonded to the non-piezoelectric support layer using wafer bonding processes, grown on the non-piezoelectric support layer, or attached to the non-piezoelectric support layer in some other way. Similarly, all of these provide flexibility in the fabrication process of the acoustic resonator.

[0018] In one exemplary embodiment, the piezoelectric thin film is composed of LN, LT, AlScN, It is made from one of ZnO and PZT. These materials exhibit suitable piezoelectric properties, enabling the acoustic resonator to operate efficiently.

[0019] In one exemplary embodiment, the non-piezoelectric support layer is made of a material whose sound wave velocity is equal to or greater than 4000 m / s. Such a non-piezoelectric support layer can help achieve better piezoelectric coupling, thereby improving the operation of the acoustic resonator.

[0020] In one exemplary embodiment, the non-piezoelectric support layer is made of one of silicon (Si), silicon carbide (SiC), boron nitride (BN), diamond, and quartz. These materials exhibit good mechanical and dielectric properties, thus providing strong support for the thin film carrying the set of staggered finger electrodes.

[0021] In one exemplary embodiment, the non-piezoelectric support layer has a cavity, and the piezoelectric thin film is disposed on the non-piezoelectric support layer such that the set of staggered finger electrodes of the IDT are suspended above the cavity. In this embodiment, the thickness of the piezoelectric thin film is approximately λ / 2. Therefore, the portion of the piezoelectric thin film containing the IDT is suspended above the cavity without contacting the non-piezoelectric support layer, thereby further improving the Q factor and enhancing the piezoelectric coupling.

[0022] Other features and advantages of the invention will become apparent after reading the following detailed description and viewing the accompanying drawings. Attached Figure Description

[0023] The invention is explained below with reference to the accompanying drawings, wherein:

[0024] Figure 1A and Figure 1B A different schematic diagram of an acoustic resonator provided in an exemplary embodiment is shown, namely: Figure 1A A top view of the acoustic resonator is shown. Figure 1B The input of the acoustic resonator is shown by using... Figure 1A The side view of the cross section obtained by section line AA in the figure;

[0025] Figure 2 An enlarged cross-sectional side view of a period is shown, the enlarged cross-sectional side view including two staggered finger electrodes of an interdigital transducer (IDT) included in an acoustic resonator provided in a first exemplary embodiment, the enlarged cross-sectional side view being in the form of... Figure 1B It is extracted from the region defined by the ellipse B in the image;

[0026] Figure 3 The A1 mode of an acoustic wave excited in the piezoelectric thin film of an acoustic resonator is schematically shown.

[0027] Figure 4 An enlarged cross-sectional side view of a period is shown, the enlarged cross-sectional side view including two staggered finger electrodes of an IDT included in an acoustic resonator provided in a second exemplary embodiment, the enlarged cross-sectional side view being in the form of... Figure 1B It is extracted from the region defined by the ellipse B in the image;

[0028] Figures 5A to 5C Exemplary admittance curves are shown, each curve plotted on a logarithmic y-bar for one of three different A1 mode XBARs. The curves show the absolute value (solid line) and real part Re(Y11) (dashed line) of the admittance Y11, i.e.: Figure 5A The admittance curve of the XBAR is shown, which includes a thin monolayer of staggered finger electrodes. Figure 5B The admittance curve of the XBAR is shown, which includes a thick monolayer of staggered finger electrodes. Figure 5C It shows including Figure 2 The admittance curve of the X-BAR of the staggered finger electrodes;

[0029] Figures 6A to 6C Exemplary admittance curves are shown. Each admittance curve is plotted on a logarithmic y-bar for one of the three different A1 modes YBAR, showing the absolute value of admittance Y11 (solid line curve) and its real part Re(Y11) (dashed line curve), i.e.: Figure 6A The admittance curve of YBAR, comprising a thin monolayer of staggered finger electrodes, is shown. Figure 6B The admittance curve of YBAR, which includes a thick monolayer of staggered finger electrodes, is shown. Figure 6C It shows including Figure 3 The admittance curve of YBAR for interleaved finger electrodes;

[0030] Figures 7A to 7CExemplary admittance curves are shown, each curve displaying the absolute value Y11 (solid line curve) and its real part Re(Y11) (dashed line curve) for one of the three different SH1 modes YBAR, using a logarithmic y-bar. Figure 7A The admittance curve of YBAR, comprising a thin monolayer of staggered finger electrodes, is shown. Figure 7B The admittance curve of YBAR, which includes a thick monolayer of staggered finger electrodes, is shown. Figure 7C It shows including Figure 3 Admittance curves of YBAR for interleaved finger electrodes. Detailed Implementation

[0031] Various embodiments of the invention have been described in further detail with reference to the accompanying drawings. However, the invention may be embodied in many other forms and should not be construed as limited to any particular structure or function disclosed in the following description. Rather, these embodiments are provided to describe the invention in detail and completely.

[0032] As will be apparent to those skilled in the art from the specific embodiments described herein, the scope of this invention covers any embodiment disclosed herein, whether implemented independently or in conjunction with any other embodiments of the invention. For example, the apparatus disclosed herein can be implemented in practice using any number of the embodiments provided herein. Furthermore, it should be understood that any embodiment of the invention can be implemented using one or more features set forth in the appended claims.

[0033] As used herein, the term "exemplary" means "for illustration." Unless otherwise stated, any embodiment described herein as "exemplary" should not be construed as preferred or having an advantage over other embodiments.

[0034] For convenience, any positioning terms such as "left," "right," "top," "bottom," "above," "below," "upper," "lower," "horizontal," and "vertical" may be used herein to describe the relationship of an element or feature to one or more other elements or features according to the accompanying drawings. It should be understood that positioning terms are intended to include different orientations of the apparatus disclosed herein, in addition to one or more orientations depicted in the figures. For example, if the apparatus in the figures is envisioned to be rotated 90 degrees clockwise, the elements or features described as "left" and "right" relative to other elements or features would be oriented "above" and "below" the other elements or features, respectively. Therefore, the positioning terms used herein should not be construed as any limitation on the invention.

[0035] Furthermore, although counting terms such as “first” and “second” may be used herein to describe various embodiments, elements, or features, it should be understood that these embodiments, elements, or features should not be limited by such counting terms. The numerical terms used herein are merely for distinguishing one embodiment, element, or feature from another. For example, the first layer discussed below may be referred to as the second layer without departing from the teachings of the invention, and vice versa.

[0036] The exemplary embodiments disclosed herein relate to an acoustic resonator that provides high-voltage electrical coupling and exhibits improved power handling characteristics and Q factor at its resonant frequency (e.g., compared to existing XBARs and YBARs). More specifically, the acoustic resonator includes an interdigital transducer (IDT) formed on a piezoelectric substrate. Each staggered finger electrode or electrode of the IDT has a multilayer structure comprising a first layer and a second layer. The second layer is disposed above the first layer and separated from the first layer by one or more bases. The thickness and width of each of the first layer, the second layer, and the one or more bases are defined based on the wavelength λ of the sound wave to be generated by the IDT in the piezoelectric substrate at the resonant frequency of the acoustic resonator. The acoustic resonator is characterized in that, in each finger electrode or electrode, the thickness of the first layer is less than the thickness of each of the one or more bases and the second layer, and the width of the one or more bases is less than the width of each of the first layer and the second layer.

[0037] Figure 1A and Figure 1B A different schematic diagram of an acoustic resonator 100 provided in an exemplary embodiment is shown. More specifically, Figure 1A A top view of the acoustic resonator 100 is shown. Figure 1B The acoustic resonator 100 is shown as being used by Figure 1A The cross-sectional side view obtained by section line AA in the figure. The acoustic resonator 100 includes an IDT, which includes a set of staggered finger electrodes or electrodes 102 formed on a piezoelectric substrate.

[0038] In this embodiment, the piezoelectric substrate serves as a layered structure, the layered structure including a piezoelectric thin film 104 disposed on a non-piezoelectric support layer 106 (see...). Figure 1BThe set of staggered finger electrodes 102 are disposed on the piezoelectric thin film 104. A non-piezoelectric support layer 106 provides mechanical support for the piezoelectric thin film 104. Preferably, the non-piezoelectric support layer 106 is made of a material whose sound velocity is equal to or greater than 4000 m / s. Some examples of such high-velocity sound materials may include, but are not limited to, silicon (Si), silicon carbide (SiC), boron nitride (BN), diamond, and quartz. The piezoelectric thin film 104 may be made of lithium niobate (LN), lithium tantalate (LT), aluminum scandium nitride (AlScN), lithium iodate (… It is made of zinc oxide (ZnO), lead zirconate titanate (PZT), or any other suitable piezoelectric material. Furthermore, the thickness of the piezoelectric film can range from 0.1 mm. Up to 2 The piezoelectric thin film 104 can be bonded to the non-piezoelectric support layer 106 using wafer bonding technology, or grown on the non-piezoelectric support layer 106, or attached to the non-piezoelectric support layer 106 in some other way. Alternatively, the piezoelectric thin film 104 can be directly attached to the non-piezoelectric support layer 106, or it can be attached to the non-piezoelectric support layer 106 via one or more intermediate layers (e.g., a set of alternating low acoustic impedance and high acoustic impedance layers).

[0039] like Figure 1A and Figure 1B As shown, the non-piezoelectric support layer 106 has a cavity 108, which is formed such that a portion of the piezoelectric film 104 including the IDT is suspended above the cavity 108 without contacting the non-piezoelectric support layer 106. Although the cavity 108 is... Figure 1B The hole shown is completely through the non-piezoelectric support layer 106, which should not be construed as a limitation of the invention. In other embodiments, the cavity 108 may be implemented as a dead hole or a notch. Generally, the term "cavity" as used herein should be understood as a hollow space within a solid object. Similarly, as... Figure 1B As shown, the cavity 108 has a rectangular shape, but it is worth noting again that any other shape of the cavity 108 (e.g., a regular or irregular polygon) is also possible, as long as the entire set of staggered finger electrodes 102 are suspended above it. The cavity 108 can be formed in the non-piezoelectric support layer 106 before or after the piezoelectric member 104 is attached. For this purpose, different techniques can be used, such as bulk micromachining, selective etching, etc.

[0040] like Figure 1AAs shown, the set of staggered finger electrodes 102 includes a first subset of finger electrodes extending from a first busbar 110 and a second subset of finger electrodes extending from a second busbar 112. The two subsets of finger electrodes are staggered. The staggered finger electrodes 102 overlap by a distance AP, which is commonly referred to as the “aperture” of the IDT. Busbars 110 and 112 serve as terminals of two different polarities of the acoustic resonator 100. During operation, a radio frequency (RF) or microwave signal having a frequency comparable to the resonant frequency of the acoustic resonator 100 is applied to busbars 110 and 112. Due to the piezoelectric effect, acoustic waves are excited within the piezoelectric film 104. For example, the acoustic waves may have an SH1 mode or an A1 mode, depending on the configuration of the staggered finger electrodes 102 (discussed in more detail below) and the material of the piezoelectric film 104 (e.g., a notch with a specific Euler angle).

[0041] It should be noted that the number, shape, and arrangement of the structural elements constituting the acoustic resonator 100 (such as...) Figure 1A and Figure 1B (As shown) is not intended to limit the invention, but merely to provide a general idea of ​​how the structural elements can be implemented within the acoustic resonator 100. For example, the cavity 108 may be absent in the non-piezoelectric support layer 106, such that the portion of the piezoelectric thin film 104 including the set of staggered finger electrodes 102 is not suspended, but is in direct contact with the non-piezoelectric support layer 106. Furthermore, the piezoelectric substrate used in the acoustic resonator 100 can be fully realized as a piezoelectric sheet or wafer (i.e., without using any support layer like layer 106).

[0042] Figure 2 A magnified cross-sectional side view of a period is shown, the magnified cross-sectional side view including two staggered finger electrodes 102 of an IDT included in an acoustic resonator 100 provided in a first exemplary embodiment. More specifically, the magnified cross-sectional side view is in the form of... Figure 1B It is extracted from the region defined by the ellipse B in the image. Figure 2 In this example, it is assumed that the left finger electrode 102 is connected to bus 110 and the right finger electrode 102 is connected to bus 112, where buses 110 and 112 serve as terminals for feeding RF potentials of opposite polarities. It should be noted that, for convenience, Figure 2 The dimensions of the staggered finger electrodes 102 and the piezoelectric film 104 are magnified. In reality, the thickness of the staggered finger electrodes 102 is usually smaller than the thickness of the piezoelectric film 104.

[0043] In a first exemplary embodiment, each finger electrode 102 serves as a multilayer structure including a first (bottom) layer 200 and a second (top) layer 202. The second layer 202 is separated from the first layer 200 by a base 204. The thickness and width of the first layer 200, the second layer 202, and the base 204 are based on the wavelength of the sound wave generated by the IDT in the piezoelectric film 104 at the resonant frequency of the acoustic resonator 100. The thickness of the first layer 200 is less than the thickness of the base 204 and the second layer 202, and the width of the base 204 is less than the width of each of the first layer 200 and the second layer 202. The center-to-center spacing (or in other words, the pitch p) of the finger electrodes 102 is also defined based on λ, and it is assumed that they are much larger than the total thickness of each finger electrode 102. The base 204 is configured such that a gap is formed between the first layer 200 and the second layer 202, on either side of the base 204. Preferably, the base 204 is positioned corresponding to the node of the sound wave. In some embodiments, the gap... It may be filled with a material (e.g., polymer, photoresist, etc.) whose acoustic impedance is at least 3 times lower than that of each finger electrode 102.

[0044] The materials for the first layer 200, the second layer 202, and the base 204 can be selected based on the following considerations. The primary function of the first layer 200 is to generate an electric field within the piezoelectric film 104; therefore, it can be made of a conductive material with moderate conductivity (since current will primarily pass through the second layer 202) and low acoustic loss. Suitable conductive materials for the first layer 200 may include, but are not limited to, molybdenum (Mo), beryllium (Be), platinum (Pt), titanium (Ti), and tungsten (W). The primary function of the second layer 202 is to provide a path for removing current and heat; therefore, it can be made of a conductive material with higher electrical and thermal conductivity compared to the first layer 200. Suitable conductive materials for the second layer 202 may include, but are not limited to, aluminum (Al), copper (Cu), silver (Ag), and gold (Au). The base 204 can be made of the same conductive material as the first layer 200 or the second layer 202, or of a different conductive material (e.g., a different metal).

[0045] It should be noted that, including, Figure 2 The acoustic resonator 100 of the set of finger electrodes 102 shown in the configuration can be used as an XBAR. In this case, preferably, if the piezoelectric film 104 has a near- The thickness of the IDT is determined by a piezoelectric material having cuts corresponding to the lateral excitation of the A1 mode (where acoustic vibrations are primarily concentrated between staggered finger electrodes 102), and each staggered finger electrode 102 of the IDT has a width comparable to the thickness of the piezoelectric film 104. In this case, the pitch p is typically large compared to the thickness of the piezoelectric film 104.

[0046] Figure 3 The A1 mode of the sound wave excited in the piezoelectric thin film 104 of the acoustic resonator 100 is schematically shown. For simplicity, Figure 3 Only two staggered finger electrodes 102 (i.e., one pitch, or in other words, half the structural period) on the piezoelectric film 104 of the acoustic resonator 100 are shown. The configuration of each finger electrode in the two staggered finger electrodes 102 is similar to... Figure 2 The method shown is the same, and represents a portion of the periodic structure shown in Figure 1, thus the acoustic resonator 100 can be used as an XBAR. Periodically opposite polarity RF potentials are fed to staggered finger electrodes 102, thereby generating a time-varying electric field between the finger electrodes. The direction of the electric field E is transverse, and opposite in direction in adjacent portions of the piezoelectric film 104, as indicated by the solid line arrow labeled "E". For those with a larger... With the correct selection of piezoelectric materials for the piezoelectric module, the transverse electric field will induce shear deformation, thereby leading to the excitation of the A1 mode of acoustic waves in the piezoelectric film 104. Figure 3 Curve 300 illustrates the shear deformation, with adjacent small dashed arrows indicating the direction and amplitude of the acoustic vibration. Essentially, it is a standing wave shear wave resonance. Similarly... Figure 3 As shown, there is essentially no electric field beneath the staggered finger electrodes 102 themselves, and the A1 mode acoustic waves are minimally excited only in region 302 beneath the staggered finger electrodes 102. Along the vertical line passing through the middle of each finger electrode 102, the amplitudes of the horizontal electric field and horizontal displacement become zero due to the symmetry of the field between adjacent pitches of the IDT. Since almost no acoustic vibrations are excited beneath the staggered finger electrodes 102, the acoustic energy coupled to the staggered finger electrodes 102 is low (i.e., almost all acoustic energy is retained in the piezoelectric film 104). The schematic illustration of the A1 mode of the acoustic waves also shows that the base of the staggered finger electrodes 102 is located at the node 304 of the acoustic waves (i.e., at the point where the acoustic waves have zero or minimal amplitude).

[0047] Figure 4 An enlarged cross-sectional side view of a period is shown, the enlarged cross-sectional side view including two staggered finger electrodes 102 of the IDT included in the acoustic resonator 100 provided in a second exemplary embodiment. Similarly, the enlarged cross-sectional side view is in the form of... Figure 1BIt is extracted from the region defined by the ellipse B in the image. Figure 4 In this example, it is assumed that the left finger electrode 102 is connected to bus 110, and the right finger electrode 102 is connected to bus 112, where buses 110 and 112 serve as terminals for feeding alternating (opposite polarity) RF potentials. It should be noted that, for convenience, Figure 4 The dimensions of the staggered finger electrodes 102 and the piezoelectric film 104 are magnified. In reality, the thickness of the staggered finger electrodes 102 is usually smaller than the thickness of the piezoelectric film 104.

[0048] In a second exemplary embodiment, each finger electrode 102 also serves as a multilayer structure comprising a first (bottom) layer 400 and a second (top) layer 402. However, the second exemplary embodiment differs from the first exemplary embodiment in that the second layer 402 is separated from the first layer 400 by two bases 404 and 406. The bases 404 and 406 are spaced apart from each other, forming a closed gap between them and each of the first layer 400 and the second layer 402. Similarly, each of bases 404 and 406 can be positioned near a node corresponding to the node of the acoustic wave to be generated by the IDT in the piezoelectric film 104 at the resonant frequency. It is worth noting that bases 404 and 406 do not necessarily need to be aligned with the edges of layers 400 and 402; for convenience, this is not necessary. Figure 4 The first layer 400 and the second layer 402 can be made of the same material as the first layer 200 and the second layer 202, respectively. Each of the bases 404 and 406 can be made of the same material as base 204. Similarly, the dimensions (i.e., thickness and width) of the first layer 400, the second layer 402, and the bases 404 and 406 can be based on... To define; for pitch That's also true.

[0049] It should be noted that, including, Figure 4 The acoustic resonator 100 with a set of finger electrodes 102 as shown can be used as a YBAR and excite either the SH1 mode or the A1 mode, depending on the piezoelectric material used in the acoustic resonator 100 (e.g., an X-cut LN with Euler angles of (90, 90, 30) or (0, 90, 0) can excite the SH1 mode). In this case, it is also preferable that the width of each finger electrode 102 is 0.5 mm. Up to 10.0 Within this range, the bases 404 and 406 are much narrower than the finger electrodes 102, and the gaps are... Less than or equal to Furthermore, the metallization rate of YBAR (i.e., the ratio of finger electrode width to pitch) is typically greater than 0.7.

[0050] In some embodiments, some of the finger electrodes (such as those in the staggered arrangement of the finger electrodes 102 at the end of the IDT of the acoustic resonator 100) Figure 2 or Figure 4 The configuration shown can be implemented as a short-circuit electrode for use as a reflector. In other embodiments, the acoustic resonator 100 may also have a groove or etched edge on either side of the IDT.

[0051] Figures 5A to 5C Exemplary admittance curves are shown, each curve plotted with a logarithmic y-bar for one of three different A1 mode XBARs, illustrating the absolute value (solid line) and real part Re(Y11) (dashed line). More specifically, Figure 5A The admittance curves of XBAR are shown for a single layer of Al interleaved finger electrodes with a thickness of 10 nm (i.e., as if only the bottom layer 200 is used in each finger electrode). Figure 5B The admittance curves of XBAR for a finger electrode consisting of a monolayer of Al with an interleaved arrangement of 210 nm thickness are shown (i.e., as if only the top layer 202 is used in each finger electrode). Figure 5C It shows including, for example Figure 2 The admittance curves of the XBAR (i.e., acoustic resonator 100) of the multilayered, staggered finger electrodes 102 configured as shown are illustrated. It is assumed that each XBAR excitation is along direction 1 (i.e., Figure 2 The A1 mode (horizontal displacement) occurs in the XBAR, while the acoustic vibration mainly occurs between the staggered finger electrodes. The acoustic resonator 100 used as the A1 mode XBAR in this case has the following parameters:

[0052]

[0053] It should be noted that the given number of staggered finger electrodes 102 (i.e., "100") should not be construed as any limitation on the invention—it can be smaller or larger, depending on the required admittance level.

[0054] like Figure 5C As shown, the resonant frequency Fr is 3125 MHz, the anti-resonant frequency Fa is 3775 MHz, and the piezoelectric coupling factor is... It equals 36.1%, and the resonant-anti-resonant (R-aR) frequency interval equals 18.9%. For comparison, Figure 5AThe admittance curves of XBARs with thin, monolayered, staggered finger electrodes shown indicate that the Q factor at the resonant frequency Fr is much lower and the impedance at resonance is higher due to the high resistivity of such thin, monolayered, staggered finger electrodes. For XBARs with thick, monolayered, staggered finger electrodes, the admittance curves are unsuitable for filter design, such as... Figure 5B As shown—this is because thick finger electrodes can lead to two strong parasitic resonances.

[0055] Therefore, there is a gap between the first layer 200 and the second layer 202. The multilayer finger electrode design not only improves the Q factor (see...) Figure 4 C), and will also provide a low level of ohmic / resistive heating in the second (top) electrode 202 (due to its low resistivity), and will also ensure efficient heat dissipation along the second (top) electrode 202 made of a material with excellent thermal conductivity.

[0056] Figures 6A to 6C Exemplary admittance curves are shown, each curve plotted with a logarithmic y-bar for one of three different A1 modes YBAR, showing the absolute value of admittance Y11 (solid line curve) and its real part Re(Y11) (dashed line curve). More specifically, Figure 6A The admittance curves of YBAR are shown for a single layer of Al with staggered finger electrodes of 10 nm thickness (i.e., as if only the bottom layer 400 is used in each finger electrode). Figure 6B The admittance curves of YBAR are shown for a single layer of Al with staggered finger electrodes of 230 nm thickness (i.e., as if only the top layer 402 is used in each finger electrode). Figure 6C It shows including, for example Figure 4 The admittance curves of the YBAR (i.e., acoustic resonator 100) of the multilayered, staggered finger electrodes 102 configured as shown are presented. It is assumed that each YBAR excitation is along direction 1 (i.e., Figure 4 The A1 mode (horizontal displacement) occurs, while the acoustic vibration mainly occurs below the staggered finger electrodes of the YBAR. In this case, the acoustic resonator 100 used as the A1 mode YBAR has the following parameters:

[0057]

[0058] It should be noted that other cuts of LN can also be used, such as cuts with a larger modulus e3,13 (here, as an example, it is an LN cut determined by Euler angles (0.90,90)).

[0059] like Figure 6C As shown, Fr equals 3358 MHz, Fa equals 3651 MHz. It equals 18.3%, and the R-aR frequency spacing equals 8.4%. For comparison, such as... Figure 6A and Figure 6B As shown, the admittance curve of YBAR, which includes thin and thick monolayers of staggered finger electrodes, is compared with that of YBAR, which includes... Figure 4 The YBAR admittance curve of the finger electrode 102 with the configuration shown is worse. In the case of thin monolayer staggered finger electrodes, the Q factor becomes worse at the resonant frequency, while in the case of thick monolayer staggered finger electrodes, the R-aR frequency interval is significantly reduced.

[0060] Figures 7A to 7C Exemplary admittance curves are shown, each curve displaying the absolute value (solid line) and real part Re(Y11) (dashed line) of admittance Y11 against one of the three different SH1 modes YBAR. More specifically, Figure 7A The admittance curves of YBAR are shown for a single layer of Al with staggered finger electrodes of 20 nm thickness (i.e., as if only the bottom layer 400 is used in each finger electrode). Figure 7B The admittance curves of YBAR are shown for a single layer of Al interleaved finger electrodes with a thickness of 360 nm (i.e., as if only the top layer 402 is used in each finger electrode). Figure 7C It shows including, for example Figure 4 The admittance curves of the YBAR (i.e., acoustic resonator 100) of the multilayered, staggered finger electrodes 102 configured as shown are illustrated. It is assumed that each YBAR excitation is along direction 2 (i.e., along the direction perpendicular to...). Figure 4 The SH1 mode is a displacement of the plane, while the acoustic vibration mainly occurs below the staggered finger electrodes of the YBAR. In this case, the acoustic resonator 100 used as the SH1 mode YBAR has the following parameters:

[0061]

[0062] As described above, the number of staggered finger electrodes 102 (i.e., "100") and the value of aperture AP (i.e., "40") The figure is given as an example and can be modified over a wide range to achieve the required static capacitance level of the acoustic resonator 100 and the abs(Y11) far from resonance. In this case, a Y-cut of LN (0, 90, 0) is used to provide the SH1 mode. It should also be noted that the given parameters above for the acoustic resonator used as the SH1 mode YBAR are not optimized to achieve, for example, maximum piezoelectric coupling.

[0063] like Figure 7C As shown, Fr equals 2078 MHz, Fa equals 2268 MHz. It equals 19.1%, and the R-aR frequency spacing equals 8.8%. From Figure 7A It can be concluded that thin, monolayered, staggered finger electrodes provide additional resistivity and reduce the Q factor. According to... Figure 7B The thick, monolayered, staggered finger electrode shape reduces piezoelectric coupling and may generate additional parasitic resonances, rendering such YBARs unusable in many cases. The proposed... Figure 4 The finger electrode design shown solves these problems while providing a high Q factor at the resonant frequency, strong piezoelectric coupling, and good power handling capability (due to low heat generation and fast heat dissipation).

[0064] Although exemplary embodiments of the invention have been described herein, it should be noted that various changes and modifications may be made to the embodiments of the invention without departing from the scope of legal protection defined by the appended claims. In the appended claims, the word "comprising" does not exclude other elements or operations, and the indefinite articles "a" or "an" do not exclude a plurality. The enumeration of certain measures in dissimilar dependent claims does not imply that combinations of these measures cannot be effectively used.

Claims

1. An acoustic resonator, characterized in that, include: Piezoelectric substrate; An interdigital transducer (IDT) is disposed on the piezoelectric substrate; The IDT includes a set of staggered finger electrodes, each finger electrode serving as a multilayer structure, the multilayer structure including a first layer and a second layer, the second layer being disposed above the first layer and separated from the first layer by at least one base; The thickness and width of each of the first layer, the second layer, and the at least one base are based on the wavelength of the sound wave generated by the IDT in the piezoelectric substrate at the resonant frequency of the acoustic resonator. To define; The thickness of the first layer is less than the thickness of each of the at least one base and the second layer, and the width of the at least one base is less than the width of each of the first layer and the second layer.

2. The acoustic resonator according to claim 1, characterized in that, The at least one base in each of the set of staggered finger electrodes includes a single base, the single base being configured such that a gap is formed between the first layer and the second layer, on either side of the base.

3. The acoustic resonator according to claim 2, characterized in that, The base of each of the set of staggered finger electrodes is positioned at a location corresponding to a node of the sound wave.

4. The acoustic resonator according to claim 1, characterized in that, The at least one base of each of the set of staggered finger electrodes includes two bases spaced apart from each other, such that a closed gap is formed between the two bases and each of the first layer and the second layer.

5. The acoustic resonator according to claim 4, characterized in that, Each of the two bases in each of the set of staggered finger electrodes is positioned at a location corresponding to a node of the sound wave.

6. The acoustic resonator according to any one of claims 2 to 5, characterized in that, The gap is filled with a material whose acoustic impedance is at least three times lower than that of each of the set of staggered finger electrodes.

7. The acoustic resonator according to any one of claims 1 to 6, characterized in that, The first layer is made of a first conductive material, the second layer is made of a second conductive material, and the at least one base is made of a third conductive material. The first conductive material may be different from or the same as the second conductive material, and the third conductive material may be different from or the same as the first or second conductive material.

8. The acoustic resonator according to claim 7, characterized in that, Compared with the second conductive material, the first conductive material has lower acoustic loss; compared with the first conductive material, the second conductive material has higher electrical conductivity and higher thermal conductivity.

9. The acoustic resonator according to any one of claims 1 to 8, characterized in that, The piezoelectric substrate is composed of lithium niobate (LN), lithium tantalate (LT), aluminum scandium nitride (AlScN), and lithium iodate (…). It is made from one of zinc oxide (ZnO) and lead zirconate titanate (PZT).

10. The acoustic resonator according to any one of claims 1 to 8, characterized in that, The piezoelectric substrate is used as a layered structure, which includes a non-piezoelectric support layer and a piezoelectric thin film. The piezoelectric thin film is disposed on the non-piezoelectric support layer, and the IDT (independent polarized thermocouple) is disposed on the piezoelectric thin film. The thickness of the piezoelectric thin film is in the range of 0.1 mm. Up to 2 .

11. The acoustic resonator according to claim 10, characterized in that, The piezoelectric film is composed of LN, LT, Al(Sc)N, It is made from one of ZnO and PZT.

12. The acoustic resonator according to claim 10 or 11, characterized in that, The non-piezoelectric support layer is made of a material with a sound velocity equal to or greater than 4000 m / s.

13. The acoustic resonator according to claim 12, characterized in that, The non-piezoelectric support layer is made of one of silicon (Si), silicon carbide (SiC), boron nitride (BN), diamond, and quartz.

14. The acoustic resonator according to any one of claims 10 to 13, characterized in that, The non-piezoelectric support layer has a cavity, and the piezoelectric thin film is disposed on the non-piezoelectric support layer, such that the set of staggered finger electrodes of the IDT are suspended above the cavity, and the thickness of the piezoelectric thin film is approximately equal to .

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