Transversely excited bulk acoustic resonator having a nonlinear chirp profile

Abstract

An acoustic resonator is provided, the acoustic resonator comprising a piezoelectric layer; and an IDT on a surface of the piezoelectric layer. The IDT comprises three portions of interleaved fingers extending alternately from a first and a second busbar. Each portion has a respective length comprising at least two pairs of interleaved fingers. At least a last portion of the IDT comprises a non-linear chirp profile such that a variation of a pitch and / or a marking of the portion is non-linear over a length of at least one portion thereof. A first mathematical derivative of the non-linear chirp profile of the last portion is of a same sign and monotonically increasing, and a second mathematical derivative of the non-linear chirp profile of the last portion is non-zero, of a same sign and exponentially increasing.

Description

Cross-references to related applications

[0001] This patent application claims priority to U.S. Provisional Application No. 63 / 755,673, filed February 7, 2025, and U.S. Non-Provisional Application No. 19 / 461,834, filed January 28, 2026, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates to radio frequency filters using acoustic resonators, and more specifically, to filters for use in communication devices. Background Technology

[0003] Radio frequency (RF) filters are two-port devices configured to allow some frequencies to pass through and block others. "Pass through" means transmission with relatively low signal loss, and "block" means obstruction or significant attenuation. The range of frequencies a filter allows through is called its "passband." The range of frequencies a filter blocks is called its "stopband." A typical RF filter has at least one passband and at least one stopband. The specific requirements for the passband or stopband can depend on the application. For example, in some cases, the "passband" can be defined as the frequency range where the filter's insertion loss is better than defined values ​​such as 1 dB, 2 dB, or 3 dB, while the "stopband" can be defined as the frequency range where the filter's suppression is greater than defined values ​​such as 20 dB, 30 dB, 40 dB, or greater (depending on the application).

[0004] RF filters are used in communication systems that transmit information via wireless links. For example, RF filters can be found in the RF front-end of cellular base stations, mobile phones and computing devices, satellite transceivers and terrestrial base stations, IoT (Internet of Things) devices, laptops and tablets, fixed-point radio links, and other communication systems. RF filters are also used in radar, as well as electronic and information warfare systems.

[0005] Enhancements to RF filters in wireless systems can have a wide-ranging impact on system performance. Improvements in RF filters can provide system performance improvements such as larger cell size, longer battery life, higher data rates, greater network capacity, lower cost, enhanced security, and higher reliability. These improvements can be implemented individually and in combination at multiple levels of the wireless system, such as at the RF module, RF transceiver, mobile or fixed subsystem, or network level. With the increasing demand for RF filters operating at higher frequencies, there is a need for improved filters capable of operating in different frequency bands, along with improvements in the manufacturing processes for producing such filters.

[0006] Laterally excited thin-film bulk acoustic resonators (XBARs) are acoustic resonator structures used in microwave filters. XBAR resonators typically include interdigital transducers (IDTs) formed on a thin floating layer or diaphragm of a single-crystal piezoelectric material. The IDT comprises a first set of parallel fingers extending from a first busbar and a second set of parallel fingers extending from a second busbar. The first and second sets of parallel fingers are interleaved. A microwave signal applied to the IDT excites a sheared master acoustic wave in the piezoelectric diaphragm. XBAR resonators offer very high electromechanical coupling and high-frequency capability. XBAR resonators can be used in a variety of RF filters, including band-stop filters, band-pass filters, duplexers, and multiplexers. XBARs are particularly well-suited for use in filters for communication bands above 3 GHz. Summary of the Invention

[0007] According to an exemplary aspect, a bulk acoustic resonator including an interdigital transducer (IDT) is provided, the IDT having one or more portions of interlaced fingers having a nonlinear chirp profile to reduce spurious amplitudes in the acoustic resonator device to achieve small-signal or large-signal performance gain.

[0008] More specifically, in an exemplary aspect, an acoustic resonator is provided, comprising: a piezoelectric layer; and an interdigital transducer (IDT) having, on the surface of the piezoelectric layer, a plurality of interlaced fingers extending alternately from a first busbar and a second busbar. In this aspect, the IDT comprises at least three portions, including a first portion, a last portion, and a central portion disposed along the length of the IDT between the first and last portions. Each of the at least three portions has a corresponding length comprising at least two pairs of interlaced fingers. Furthermore, at least one of the first and last portions of the IDT comprises a non-linear chirp profile, such that the variation of at least one of the marking and pitch of the at least one portion is non-linear along the length of the at least one portion, the marking being the width of the at least two pairs of interlaced fingers, and the pitch being the center-to-center spacing between each pair of interlaced fingers. Furthermore, the first-order mathematical derivative of the nonlinear chirped profile of at least one part is monotonically increasing with the same sign, and the second-order mathematical derivative of the nonlinear chirped profile of at least one part is nonzero, with the same sign and exponentially increasing.

[0009] In another exemplary aspect, both the first and last portions of the IDT include recessed nonlinear chirped profiles such that at least one of the markings and pitches of each of the first and last portions becomes gentler as the respective portion extends toward the central portion and steeper as the respective portion extends away from the central portion.

[0010] In another exemplary aspect, the change in at least one of the markings and pitch of both the first and last parts is represented by A(x), where, , where k>0 and measures the curvature of the nonlinear chirped profile, and x is between -1 and +1.

[0011] In another exemplary aspect, both the first and last portions of the IDT include concave, non-linear chirped profiles, such that the variation of at least one of the marking and pitch in each of the first and last portions is steeper towards the central portion and becomes gentler as the respective portions extend away from the central portion. Furthermore, in this aspect, the variation of at least one of the marking and pitch in both the first and last portions can be represented by A(x), where, , where k>0 and measures the curvature of the nonlinear chirped profile, and x is between -1 and +1.

[0012] In another exemplary aspect, each of the central portion and at least one portion includes a plurality of sub-parts, each sub-part having at least three interlaced fingers, wherein the at least three interlaced fingers have at least one of a constant pitch or a constant mark.

[0013] In another exemplary aspect, the number of interlaced fingers in at least one portion is approximately 25% or less of the total number of fingers among the plurality of interlaced fingers of the IDT. Furthermore, in this aspect, the pitch variation of at least one portion increases exponentially, and the pitch variation of the central portion may be relatively linear relative to the pitch variation of at least one portion. Additionally, the marking may be substantially constant over the length of the IDT. Furthermore, the central portion may include a substantially linear chirped profile.

[0014] In another exemplary aspect, an acoustic resonator is provided, comprising: a piezoelectric layer; and an interdigital transducer (IDT) having, on the surface of the piezoelectric layer, a plurality of interlaced fingers extending alternately from a first busbar and a second busbar. In this aspect, the IDT comprises a plurality of portions, each portion having a respective length including at least two pairs of interlaced fingers, the IDT having an asymmetric chirped profile such that a variation in at least one of a marking and a pitch of a first portion of the plurality of portions is non-linear over the length of the first portion, the marking being the width of at least two pairs of interlaced fingers, and the pitch being the center-to-center spacing between each pair of interlaced fingers, and a variation in at least one of the marking and the pitch having less than 25% influence on the primary excitation acoustic mode of the acoustic resonator compared to a 1:1 influence of at least one of the pitch and the marking on modes other than the primary excitation acoustic mode.

[0015] In another exemplary aspect, a second portion of the plurality of portions of the IDT has a substantially linear pitch or marking profile that differs from the asymmetric chirped profile of the first portion. In this aspect, the plurality of portions of the IDT may include a first portion, a second portion, and a third portion, wherein the second portion is a central portion located between the first and third portions along the length of the IDT. Furthermore, both the first and third portions of the IDT may include concave, non-linear chirped profiles such that the variation in at least one of the marking and pitch of each of the first and third portions becomes gentler as the respective portion extends toward the central portion and steeper as the respective portion extends away from the central portion.

[0016] In another exemplary aspect, both the first and third portions of the IDT include recessed nonlinear chirped profiles such that at least one of the markings and pitches of each of the first and third portions changes steeper toward the central portion and becomes gentler as the respective portions extend away from the central portion.

[0017] In another exemplary aspect, the pitch or marking profile of the second part is substantially linear, and the variation of at least one of the marking and pitch of the first part increases as the first part extends away from the second part along the length direction of the IDT, and the first mathematical derivative of the asymmetric chirped profile of the first part is monotonically increasing with the same sign, and the second mathematical derivative of the asymmetric chirped profile of the first part is non-zero, with the same sign and exponentially increasing.

[0018] In another exemplary aspect, the number of interlaced fingers in the first portion is 25% or less of the total index of the plurality of interlaced fingers of the IDT, and the pitch of the first portion changes exponentially, while the pitch of the second portion changes relatively linearly relative to the pitch of at least one portion.

[0019] In another exemplary aspect, the first part includes a plurality of sub-parts, each sub-part having at least three interlaced fingers, wherein the at least three interlaced fingers have at least one of a constant pitch or a constant mark.

[0020] In another exemplary aspect, an acoustic resonator is provided, comprising: a piezoelectric layer; and an interdigital transducer (IDT) having, on the surface of the piezoelectric layer, a plurality of interlaced fingers extending alternately from a first busbar and a second busbar. In this aspect, the IDT includes a first portion and a second portion, each portion having a respective length comprising at least two pairs of interlaced fingers, the interlaced fingers of each of the first and second portions having an asymmetric chirped profile such that the variation of at least one of a marking and a pitch is non-linear over the length of the respective portion, the marking being the width of at least two pairs of interlaced fingers, and the pitch being the center-to-center spacing between each pair of interlaced fingers, and the variation of the pitch and at least one of the markings of each of the first and second portions increasing exponentially as the respective lengths of the first and second portions extend toward each other, such that the IDT comprising the first and second portions as a whole has a symmetrical chirped profile. Attached Figure Description

[0021] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate one or more exemplary aspects of this disclosure and, together with the detailed description, serve to explain the principles and implementation of one or more exemplary aspects of this disclosure.

[0022] Figure 1A Includes schematic plan view and schematic cross-sectional view of a transversely excited thin-film bulk acoustic resonator (XBAR).

[0023] Figure 1B A schematic cross-sectional view of an alternative configuration of XBAR is shown.

[0024] Figure 2A yes Figure 1A A magnified schematic cross-sectional view of a portion of the XBAR.

[0025] Figure 2B yes Figure 1A Enlarged schematic cross-sectional view of the alternative configurations of XBAR.

[0026] Figure 2C yes Figure 1A An enlarged schematic cross-sectional view of another alternative configuration of XBAR.

[0027] Figure 2D yes Figure 1A An enlarged schematic cross-sectional view of another alternative configuration of XBAR.

[0028] Figure 2E This is an enlarged schematic cross-sectional view of a portion of a securely mounted XBAR (SM XBAR).

[0029] Figure 3A It is a schematic cross-sectional view of XBAR based on an exemplary aspect.

[0030] Figure 3B This is an alternative schematic cross-sectional view of XBAR based on an exemplary aspect.

[0031] Figure 4 This is a diagram showing the shear level acoustic modes in XBAR.

[0032] Figure 5A Is using Figure 1A and / or Figure 1B A schematic block diagram of the XBAR filter.

[0033] Figure 5B This is a schematic diagram of an RF module including an acoustic filter device according to an exemplary aspect.

[0034] Figure 6 It is a plan view of a multi-marker multi-pitch IDT based on an exemplary aspect.

[0035] Figure 7A It is a graphic representation of the IDT chirp profile based on the position along the length of the IDT, according to an exemplary aspect.

[0036] Figure 7B It shows Figure 7A A graph showing the performance differences between the chirped profiles.

[0037] Figure 7C A graph illustrating the ratios of the effects of chirp on different vibration modes of an acoustic resonator is shown.

[0038] Figure 8A It is a graph of the IDT chirp profile based on the position along the length of the IDT, according to another exemplary aspect.

[0039] Figure 8B A graph showing the acoustic intensity relative to which sub-parts of the IDT should have a non-linear chirp configuration, according to an exemplary aspect, is shown.

[0040] Figure 8C It shows that it has Figure 8A The figure shows three graphs of the pitch profile p(x), the first derivative and the second derivative of the profile p(x) of the IDT.

[0041] Figure 9A It is a graph of the IDT chirp profile based on the position along the length of the IDT, according to another exemplary aspect.

[0042] Figure 9B It is a graph of the IDT chirp profile based on the position along the length of the IDT, according to another exemplary aspect.

[0043] Figure 9C It shows that it has Figure 9A The figure shows three graphs of the pitch profile p(x), the first derivative and the second derivative of the profile p(x) of the IDT.

[0044] Figure 10 A graph illustrating the effect on the A1 mode is shown, which is measured as a decrease in resonant Q that trades off with a reduction in spurious amplitude.

[0045] Throughout the description, elements appearing in the accompanying drawings are assigned three- or four-digit reference numerals, wherein the two least significant digits identify the element, and one or two most significant digits are the reference numerals used to first introduce the element. Elements not described in conjunction with the accompanying drawings may be assumed to have the same characteristics and functions as previously described elements with the same reference numerals. Detailed Implementation

[0046] Various aspects of the disclosed bulk acoustic resonators, filter devices, radio frequency modules, and methods of manufacturing thereof are now described with reference to the accompanying drawings, wherein the same reference numerals are used to denote the same elements throughout. In the following description, numerous specific details are set forth for illustrative purposes to facilitate a thorough understanding of one or more aspects of this disclosure. However, it will be apparent in some or all instances that any aspect described below can be practiced without employing the specific design details described below. In other instances, well-known structures and devices are shown in block diagram form to facilitate the description of one or more aspects. A simplified overview of one or more aspects of the invention is presented below to provide a basic understanding of the invention.

[0047] Figure 1A A simplified schematic top view and orthogonal cross-sectional view of a bulk acoustic resonator device (i.e., a laterally excited thin-film bulk acoustic resonator (XBAR) 100) are shown. XBAR resonators, such as resonator 100, can be used in a variety of RF filters, including band-stop filters, band-pass filters, duplexers, and multiplexers. XBARs are particularly suitable for use in filters for communication bands above 3 GHz.

[0048] Generally, XBAR 100 includes a conductor pattern (e.g., a thin-film metal layer) formed on one or both surfaces of a piezoelectric layer 110 (here, the terms piezoelectric plate and piezoelectric layer are used interchangeably), the piezoelectric layer 110 having parallel front sides 112 and rear sides 114 (also commonly referred to as the first surface and the second surface, respectively). It should be understood that the term "parallel" generally refers to the front sides 112 and rear sides 114 being opposite each other, and the surfaces are not necessarily flat and perfectly parallel. For example, due to manufacturing variations resulting from the deposition process, the front sides 112 and rear sides 114 may have surface undulations as will be understood by those skilled in the art. Furthermore, the term "substantially" as used herein is used to describe components, parameters, etc., that are substantially the same (i.e., "substantially constant"), but as will be understood by those skilled in the art, may vary slightly in practice (e.g., within an acceptable threshold or percentage) due to possible manufacturing variations. For the purposes of this disclosure, the use of the term "or" in the claims is used to mean "and / or" unless explicitly indicated to refer only to alternatives or if the alternatives are mutually exclusive.

[0049] According to an exemplary aspect, the piezoelectric layer can be a thin single-crystal layer of a piezoelectric material (e.g., lithium niobate, lithium tantalate, lanthanum gallium silicate, gallium nitride, or aluminum nitride). It should be understood that the term "single-crystal" does not necessarily mean a perfectly uniform crystal structure and may include impurities due to manufacturing variations, as long as the crystal structure is within acceptable tolerances. The piezoelectric layer is diced such that the orientation of the X, Y, and Z crystal axes relative to the front and back sides is known and consistent. In the example described herein, the piezoelectric layer is Z-cut, meaning the Z-axis is perpendicular to the front side 112 and the back side 114. However, XBARs can be fabricated on piezoelectric layers with other crystal orientations, including rotatable Z-cut, Y-cut, and rotatable YX-cut.

[0050] Y-cut series (e.g., 120Y and 128Y) are often referred to as 120YX or 128YX, where the "cut angle" is the angle between the y-axis and the normal to the layer. The "cut angle" is equal to β + 90°. For example, layers with Euler angles [0°, 30°, 0°] are often referred to as "120° rotated Y-cut" or "120Y". Therefore, the Euler angles for 120YX and 128YX are (0, 120 to 90, 0) and (0, 128 to 90, 0), respectively. "Z-cut" is often referred to as ZY-cut and is understood to mean that the layer surface is perpendicular to the Z-axis, but the wave propagates along the Y-axis. The Euler angle for ZY-cut is (0, 0, 90).

[0051] Except for the portion of the piezoelectric layer 110 formed above (e.g., spanning or extending over) a cavity 140 in one or more layers below the piezoelectric layer 110 (e.g., above the substrate or one or more intermediate layers in the substrate), the rear side 114 of the piezoelectric layer 110 may be at least partially supported by the surface of the substrate 120. In other words, the rear side 114 of the piezoelectric layer 110 may be directly or indirectly coupled or connected to the surface of the substrate 120 via one or more intermediate layers (e.g., dielectric layers such as silicon oxide layers). Furthermore, as may be used interchangeably herein, the phrases “supported by” or “attached” may mean direct attachment, indirect attachment, mechanical support, structural support, or any combination thereof. The portion of the piezoelectric layer above (e.g., spanning or extending over) a cavity may be referred to herein as “diaphragm” 115 because it is physically similar to the diaphragm of a microphone. Figure 1A As shown, the diaphragm 115 is continuous with the remainder of all perimeters 145 of the piezoelectric layer 110 surrounding the cavity 140. In this context, "continuous" means "continuously connected without any intermediate links." However, in an exemplary aspect, the diaphragm 115 may be configured such that at least 50% of the edge surface of the diaphragm 115 is coupled to the edge of the piezoelectric layer 110.

[0052] According to an exemplary aspect, substrate 120 is configured to provide mechanical support to piezoelectric layer 110. Substrate 120 may be, for example, silicon, sapphire, quartz, or some other material, or a combination of materials. The back side 114 of piezoelectric layer 110 may be bonded to substrate 120 using a wafer bonding process. Alternatively, piezoelectric layer 110 may be grown on substrate 120, or otherwise supported by or attached to substrate.

[0053] For the purposes of this disclosure, "cavity" has its conventional meaning as "empty space within a solid". Cavity 140 can be a hole that completely penetrates the substrate 120 (as shown in section AA), or a hole within the dielectric layer (as shown in section AA). Figure 1B (as shown) or a recess in the substrate 120. For example, the cavity 140 can be formed by selectively etching the substrate 120 before or after directly or indirectly attaching the piezoelectric layer 110 and the substrate 120.

[0054] As shown in the figure, the conductor pattern of XBAR 100 includes an interdigital transducer (IDT) 130. IDT 130 includes a first plurality of parallel fingers (e.g., fingers 136) extending from a first busbar 132 and a second plurality of fingers extending from a second busbar 134. The first and second plurality of parallel fingers are staggered, and may be "substantially" parallel to each other, for example, due to minor variations (e.g., due to manufacturing tolerances). At least a portion of the staggered fingers overlaps by a distance AP, which is generally referred to as the "aperture" of the IDT. The center-to-center distance L between the outermost fingers of IDT 130 is the "length" of the IDT.

[0055] exist Figure 1A In the example, IDT 130 is located on the surface of the front side 112 of the piezoelectric layer 110 (e.g., the first surface). However, as described below, in other configurations, IDT 130 may be located on the surface of the rear side 114 of the piezoelectric layer 110 (e.g., the second surface), or on both the surfaces of the front side 112 and the rear side 114 of the piezoelectric layer 110.

[0056] The first bus 132 and the second bus 134 are configured as terminals of the XBAR 100, from which a plurality of interleaved fingers extend. In operation, a radio frequency (RF) or microwave signal applied between the two buses 132, 134 of the IDT 130 primarily excites an acoustic mode (i.e., the primary shear acoustic mode) within the piezoelectric layer 110. As will be discussed in further detail, the primary excitation shear acoustic mode is a bulk shear mode or bulk acoustic wave, wherein the acoustic energy of the bulk shear acoustic wave is excited in the piezoelectric layer 110 by the IDT 130 and propagates in a direction substantially, primarily, and / or substantially orthogonal to the surface of the piezoelectric layer 110, which is also primarily perpendicular to or transverse to the direction of the electric field generated by the IDT fingers. That is, when an RF or microwave signal is applied between the two buses 132, 134, the RF voltage applied to each set of IDT fingers generates a time-varying electric field transversely excited relative to the surface of the piezoelectric layer 110. Therefore, in some cases, the dominant excitation acoustic mode can often be referred to as transversely excited volumetric acoustic wave because, contrary to propagation, displacement occurs primarily in the volume direction of the piezoelectric layer, as shown in the following reference. Figure 4 To be discussed in more detail.

[0057] For the purposes of this disclosure, "dominant acoustic mode" can generally refer to the operating mode that causes vibrational displacement in the dominant thickness shear direction (e.g., the X direction), so that the wave propagates substantially and / or primarily in the direction connecting the opposing front and rear surfaces of the piezoelectric layer (i.e., the Z direction). In other words, the X-direction component of the wave is significantly smaller than the Z-direction component. The use of the term "dominant" in "dominant excited acoustic mode" does not necessarily refer to a low-order or high-order mode. Therefore, the XBAR is considered a laterally excited thin-film bulk wave resonator. A physical constraint is that when an RF or microwave signal is applied between the two buses 132, 134 of the IDT 130, heat is generated, which must be dissipated from the resonator to improve performance. Generally, heat can be dissipated through lateral conduction on the film (e.g., in the electrodes themselves) and through vertical conduction from the cavity to the substrate.

[0058] In either case, the IDT 130 is located at or on the piezoelectric layer 110, such that at least the fingers of the IDT extend at or on the portion of the piezoelectric layer 110 above the cavity 140 (e.g., diaphragm 115), as described herein. Figure 1A As shown, cavity 140 has a rectangular cross-section, the extent of which is greater than the aperture AP and length L of IDT 130. According to other exemplary aspects, the cavity of the XBAR can have different cross-sectional shapes, such as regular or irregular polygons. The cavity of the XBAR can have more or fewer four sides, which can be straight or curved.

[0059] According to an exemplary aspect, the area of ​​XBAR 100 is determined as the area of ​​IDT 130. For example, the area of ​​IDT 130 can be determined based on the product of a measured length L and the width of the aperture AP of the interlaced fingers of IDT 130. As used herein by way of this disclosure, area is expressed in μm. 2 The unit is used for reference. Therefore, as described below, the area of ​​the XBAR 100 can be adjusted based on design choices, thereby adjusting the total capacitance of the XBAR 100.

[0060] To facilitate Figure 1A As shown, the geometric pitch and width of the IDT fingers are significantly exaggerated relative to the length (dimension L) and aperture (dimension AP) of the XBAR. A typical XBAR in an IDT has more than ten parallel fingers. For example, according to the exemplary aspect, an XBAR in an IDT can have hundreds or even thousands of parallel fingers. Similarly, the thickness of the fingers in the cross-sectional view is significantly exaggerated.

[0061] Figure 1B A schematic cross-sectional view of alternative XBAR configuration 100' is shown. Figure 1BIn the middle, the cavity 140 of the resonator 100' (which can typically correspond to Figure 1A The cavity 140 is completely formed on the dielectric layer 124 (e.g., silicon oxide or silicon dioxide, such as...). Figure 1B The dielectric layer 124 is located within the substrate 120 (as shown). Figure 1B The middle is indicated as Si) and the piezoelectric layer 110 (in Figure 1B The dielectric layer 124 is shown as having (e.g., by etching) a cavity 140 formed therein, but it should be understood that the dielectric layer 124 may be formed from multiple individual dielectric layers formed on top of each other to provide a stack of materials.

[0062] In addition, Figure 1B In this example, cavity 140 is defined by dielectric layer 124 on all sides. However, in other exemplary embodiments, one or more sides of cavity 140 may be defined by substrate 120 and / or piezoelectric layer 110. Figure 1B In the example, cavity 140 has a trapezoidal shape. However, as mentioned above, the shape of the cavity is not limited and can be rectangular, elliptical, or other shapes.

[0063] Figure 2A It shows Figure 1A or Figure 1B A detailed schematic cross-sectional view of XBAR 100 (labeled as detail C). Piezoelectric layer 110 is a single-crystal layer of piezoelectric material with a thickness ts. Ts can be, for example, 100 nm to 1500 nm. This is used in 5G NR and Wi-Fi applications from 3.4 GHz to 7 GHz. TM When used in bandgap filters, the thickness ts can be, for example, from 150 nm to 500 nm. In an exemplary aspect, the thickness ts can be measured in a direction substantially perpendicular or orthogonal to the surface of the piezoelectric layer.

[0064] In this respect, a front dielectric layer 212 (e.g., a first dielectric coating or material) can be formed on the front side 112 of the piezoelectric layer 110. By definition, the "front side" of an XBAR is the surface facing away from the substrate. The front dielectric layer 212 has a thickness tfd. Figure 2A As shown, the front dielectric layer 212 covers IDT fingers 238a and 238b, which can correspond to the above-mentioned... Figure 1A The described finger-like object 136. Although not in Figure 2A As shown, the front dielectric layer 212 may also be deposited only between the IDT fingers 238a and 238b. In this case, an additional thin dielectric layer (not shown) may be deposited on the IDT fingers to seal and passivate the fingers. Furthermore, although... Figure 2AThe front dielectric layer 212 is not shown, but it may also be deposited, for example, only on the selected IDT fingers 238a.

[0065] A rear dielectric layer 214 (e.g., a second dielectric coating or material) may also be formed on the rear side of the piezoelectric layer 110. Generally, for the purposes of this disclosure, the term "rear side" refers to the side opposite to the conductor pattern of the IDT structure and / or the side opposite to the front dielectric layer 212. Furthermore, the rear dielectric layer 214 has a thickness tbd. The front dielectric layer 212 and the rear dielectric layer 214 may be non-piezoelectric dielectric materials, such as silicon oxide, silicon dioxide, or silicon nitride. Tfd and tbd may, for example, be from 0 to 500 nm. Tfd and tbd may be less than the thickness ts of the piezoelectric layer. Tfd and tbd are not necessarily equal, and the front dielectric layer 212 and the rear dielectric layer 214 are not necessarily made of the same material. In exemplary aspects, according to various exemplary aspects, either or both of the front dielectric layer 212 and the rear dielectric layer 214 may be formed from multiple layers of two or more materials.

[0066] IDT fingers 238a, 238b may include aluminum, substantially (i.e., primarily) aluminum alloys, copper, substantially (i.e., primarily) copper alloys, beryllium, gold, or some other conductive material. A thin layer (relative to the total thickness of the conductor) of other metals such as chromium or titanium may be formed below and / or above the fingers to improve adhesion between the fingers and the piezoelectric layer 110, and / or passivate or encapsulate the fingers. The busbar of the IDT ( Figure 1A 132, 134) may be made of the same or different material as the fingers. In various exemplary aspects, the cross-sectional shape of the IDT fingers may be trapezoidal (finger 238a), rectangular (finger 238b), or some other shape. Generally, note that the terms “comprising,” “having,” “including,” and “containing” (and variations thereof) as used herein are open-ended connecting verbs and allow for the addition of other elements when used in the claims. Furthermore, unless the context otherwise indicates, the word “a” when used in conjunction with the term “comprising” in the claims or description means one or more.

[0067] Size p (i.e., “pitch”) can be considered as adjacent IDT fingers extending from different busbars (e.g., Figures 2A to 2D The center-to-center spacing between the IDT fingers 238a and 238b in the diagram. Figure 2AAs shown, the center point of the center-to-center spacing can be measured at the center of the width "w" of the finger. In some cases, the center-to-center spacing can change if the width of a given finger varies along the length of the finger, if the width and direction of extension change, or any variation thereof. In this case, for a given location along AP, the center-to-center spacing can be measured as the average center-to-center spacing, the maximum center-to-center spacing, the minimum center-to-center spacing, or any variation thereof. Adjacent fingers can each extend from different busbars, and the center-to-center spacing can be measured from the center of a first finger extending from a first busbar to the center of a second finger adjacent to the first finger and extending from a second busbar. The center-to-center spacing can be constant over the length of the IDT, in which case the dimension p can be referred to as the pitch of the IDT and / or the pitch of the XBAR. However, in an alternative exemplary aspect, the center-to-center spacing varies along the length of the IDT, in which case the pitch of the IDT can be the average value of the dimension p over the length of the IDT. The center-to-center spacing from one finger to an adjacent finger can vary continuously compared to other adjacent fingers, vary continuously in discrete portions of multiple adjacent pairs, or any combination thereof. Each IDT finger (e.g., Figures 2A to 2D The IDT fingers 238a, 238b in the diagram have a width w measured perpendicular to the longitudinal direction of each finger. The width w may also be referred to herein as a "mark". Generally, the width of the IDT fingers can be constant along the length of the IDT, in which case the dimension w can be the width of each IDT finger. However, in another exemplary aspect, as will be discussed below, the width of the individual IDT fingers varies along the length of the IDT 130, in which case the dimension w can be the average width of the IDT fingers along the length of the IDT. Note that the pitch p and width w of the IDT fingers are measured in a direction substantially parallel to the length L of the IDT, as shown below. Figure 1A Defined in [the document / reference].

[0068] Generally speaking, the IDT of XBAR is significantly different from that used in surface acoustic wave (SAW) resonators, mainly in the excitation of XBAR IDT as follows: Figure 4A more detailed description of the master shear acoustic mode (also known as the master shear mode, master shear thickness mode, etc.) is provided, in which the SAW resonator excites surface waves during operation. Furthermore, in the SAW resonator, the pitch of the IDT is half the wavelength of the acoustic wave at the resonant frequency. Additionally, the mark-to-pitch ratio of the SAW resonator IDT is typically close to 0.5 (i.e., the mark or finger width is approximately one-quarter of the wavelength of the acoustic wave at resonance). In XBAR, the IDT pitch p is typically 2 to 20 times the width w of the finger. Additionally, the IDT pitch p is typically 2 to 20 times the thickness ts of the piezoelectric layer 110. Furthermore, the width of the IDT fingers in XBAR is not limited to one-quarter of the wavelength of the acoustic wave at resonance. For example, the width of the XBAR IDT fingers can be 500 nm or greater, allowing the IDT to be fabricated using optical lithography. The thickness tm of the IDT fingers can range from 100 nm to approximately equal to the width w, because lithography processes typically cannot support configurations with a thickness greater than the width. The IDT's busbar ( Figure 1A The thickness of 132 and 134 in the document can be equal to, less than, greater than, or any combination thereof, the thickness tm of the IDT fingers. Note that the XBAR device described herein is not limited to the size range described herein.

[0069] Furthermore, unlike SAW filters, the resonant frequency of an XBAR depends on the total thickness of its diaphragm (i.e., in the vertical or thickness direction), including the piezoelectric layer 110 and the front dielectric layer 212 and rear dielectric layer 214 disposed thereon. In an exemplary aspect, the thickness of one or both dielectric layers (i.e., on opposite surfaces of the piezoelectric layers) can be varied to change the resonant frequency of various XBARs in a filter. For example, a parallel resonator in a trapezoidal filter circuit can contain a thicker dielectric layer to lower the resonant frequency of the parallel resonator relative to a series resonator with a thinner dielectric layer, thereby resulting in a thinner overall thickness.

[0070] Return to reference Figure 2A The thickness tfd of the front dielectric layer 212 above the IDT fingers 238a, 238b can be greater than or equal to the minimum thickness required to cover and passivate the IDT fingers and other conductors on the front side 112 of the piezoelectric layer 110. Depending on the material and deposition method of the front dielectric layer, the minimum thickness, according to an exemplary aspect, can be, for example, from 10 nm to 50 nm. The thickness of the rear dielectric layer 214 can be configured to a specific thickness to adjust the resonant frequency of the resonator, as will be described in more detail below.

[0071] although Figure 2A The configuration of IDT fingers 238a and 238b at the front side 112 of the piezoelectric layer 110 is disclosed, but alternative configurations may be provided. For example, Figure 2BAn alternative configuration (labeled as Detail C') is shown, in which IDT fingers 238a, 238b are located at the rear side 114 of the piezoelectric layer 110 (i.e., facing the cavity) and are covered by the rear dielectric layer 214. A front dielectric layer 212 may cover the front side 112 of the piezoelectric layer 110. In an exemplary aspect, the dielectric layer disposed on the diaphragm of each resonator can be trimmed or etched to adjust the resonant frequency. However, if the dielectric layer is on the cavity-facing side of the diaphragm, variations in stray modes (e.g., caused by coatings on the fingers) may exist. Furthermore, the markings can be altered by a passivation layer coated on top of the IDT, which can also lead to straying. Therefore, as... Figure 2B As shown, by placing IDT fingers 238a and 238b on the rear side 114 of the piezoelectric layer 110, compared to when the IDT fingers 238a and 238b are on the front side 112 of the piezoelectric layer 110, the need to address both frequency variations and their impact on stray emissions can be eliminated.

[0072] Figure 2C An alternative configuration (labeled as Detail C'') is shown, in which IDT fingers 238a, 238b are on the front side 112 of the piezoelectric layer 110 and are covered by the front dielectric layer 212. IDT fingers 238c, 238d are also on the rear side 114 of the piezoelectric layer 110 and are also covered by the rear dielectric layer 214. As previously described, the front dielectric layer 212 and the rear dielectric layer 214 are not necessarily of the same thickness or the same material.

[0073] Figure 2D Another alternative configuration (labeled as Detail C''') is shown, in which IDT fingers 238a, 238b are on the front side 112 of the piezoelectric layer 110 and are covered by the front dielectric layer 212. The surface of the front dielectric layer is planarized. Planarization can be performed, for example, by polishing or some other method. A thin layer of dielectric material with thickness tp can cover the IDT fingers 238a, 238b to seal and passivate the fingers. The size TP can be, for example, 10 nm to 50 nm.

[0074] The above about Figures 2A to 2D Each XBAR configuration described includes a diaphragm spanning above the cavity. Alternatively, however, a bulk acoustic resonator can be rigidly mounted, wherein a diaphragm with IDT fingers is mounted on or above a Bragg mirror, which in turn can be mounted on a substrate.

[0075] Specifically, Figure 2E A detailed schematic cross-sectional view of a rigidly mounted XBAR (SM-XBAR) is shown. Note that, in addition to having a rigidly mounted configuration, Figure 2E The information was largely disclosed regarding... Figure 1AThe cross-section is similar to that of the IDT. In this respect, the SM-XBAR includes a piezoelectric layer 110 and an IDT (where only two fingers 236 are visible), wherein a dielectric layer 212 is disposed on the piezoelectric layer 110 and the IDT fingers 236. Similar to the configuration described above, the piezoelectric layer 110 has parallel front and rear surfaces. Dimension ts is the thickness of the piezoelectric layer 110. The width of the IDT fingers 236 is dimension w, the thickness of the IDT fingers is dimension tm, and the IDT pitch is dimension p.

[0076] and Figure 1A The XBAR device shown is the opposite. Figure 2E The IDT of the SM XBAR is not formed on the diaphragm spanning the cavity in the substrate. Instead, the acoustic Bragg reflector 240 is sandwiched between the surface 222 of the substrate 220 and the rear surface of the piezoelectric layer 110. The term "sandwiched between" means that the acoustic Bragg reflector 240 is disposed between the surface 222 of the substrate 220 and the rear surface of the piezoelectric layer 110 and is mechanically attached to both the surface 222 of the substrate 220 and the rear surface of the piezoelectric layer 110. In some cases, a layer of additional material (e.g., one or more dielectric layers) may be disposed between the acoustic Bragg reflector 240 and the surface 222 of the substrate 220 and / or between the Bragg reflector 240 and the rear surface of the piezoelectric layer 110. Such an additional material layer may be present, for example, to facilitate bonding of the piezoelectric layer 110, the acoustic Bragg reflector 240, and the substrate 220.

[0077] The acoustic Bragg reflector 240 may be an acoustic mirror configured to reflect at least a portion of the dominant acoustic mode excited in a piezoelectric material, and includes multiple dielectric layers alternating between materials with high acoustic impedance and materials with low acoustic impedance. The acoustic impedance of a material is the product of the shear wave velocity and density of the material. “High” and “low” are relative terms. For each layer, the standard used for comparison is the adjacent layers. The acoustic impedance of each “high” acoustic impedance layer is higher than that of two adjacent low acoustic impedance layers. The acoustic impedance of each “low” acoustic impedance layer is lower than that of two adjacent high acoustic impedance layers. As discussed above, the dominant acoustic mode in the piezoelectric layers of the XBAR is a shear volume wave. In an exemplary aspect, the thickness of each layer of the acoustic Bragg reflector 240 is equal to or approximately one-quarter of the wavelength of a shear volume wave with the same polarization as the dominant acoustic mode in that layer at or near the resonant frequency of the SM XBAR. Dielectric materials with relatively low acoustic impedance include silicon dioxide, carbon-containing silicon oxide, and some kind of plastic such as cross-linked polystyrene polymers. Materials with relatively high acoustic impedance include hafnium oxide, silicon nitride, aluminum nitride, and silicon carbide. All high acoustic impedance layers of the acoustic Bragg reflector 240 need not be made of the same material, and all low acoustic impedance layers need not be made of the same material. Figure 2EIn the example, the acoustic Bragg reflector 240 has a total of six layers, but the acoustic Bragg reflector can have more or fewer than six layers in alternative configurations.

[0078] IDT fingers (e.g., IDT fingers 236, 238a, and 238b) may be disposed on the surface of the front side 112 of the piezoelectric layer 110. Alternatively, the IDT fingers (e.g., IDT fingers 236, 238a, and 238b) may be disposed in a groove formed in the surface of the front side 112. The groove may extend partially through the piezoelectric layer. Alternatively, the groove may extend completely through the piezoelectric layer.

[0079] Figure 3A and Figure 3B The XBAR 100 is shown along the edge. Figure 1A Two exemplary cross-sectional views of section AA as defined in the diagram. Figure 3A In this configuration, the piezoelectric layer 310, corresponding to the piezoelectric layer 110, is directly attached to the substrate 320, which can correspond to... Figure 1A The substrate 120. Furthermore, a cavity 340 that does not completely penetrate the substrate 320 is formed in the substrate beneath the portion of the piezoelectric layer 310 containing the XBAR-containing IDT (i.e., the diaphragm 315). In an exemplary aspect, the cavity 340 may correspond to... Figure 1A and / or Figure 1B Cavity 140. In an exemplary aspect, cavity 340 may be formed, for example, by etching substrate 320 prior to attaching piezoelectric layer 310. Alternatively, cavity 340 may be formed by etching substrate 320 with a selective etchant that reaches the substrate through one or more openings provided in piezoelectric layer 310.

[0080] Figure 3BAn alternative aspect is shown, wherein the substrate 320 includes a base 322 and an intermediate layer 324 disposed between the piezoelectric layer 310 and the base 322. For example, the base 322 may be silicon (e.g., a silicon support substrate), and the intermediate layer 324 may be silicon dioxide or silicon nitride or some other material, such as an intermediate dielectric layer. That is, in this aspect, the base 322 and the intermediate layer 324 are collectively referred to as the substrate 320. As further shown, a cavity 340 is formed in the intermediate layer 324 beneath the portion of the piezoelectric layer 310 containing the IDT fingers of the XBAR (i.e., the diaphragm 315). For example, the cavity 340 may be formed by etching the intermediate layer 324 before attaching the piezoelectric layer 310. Alternatively, the cavity 340 may be formed by etching the intermediate layer 324. In other example embodiments, the cavity 340 may be defined in the intermediate layer 324 in other ways, depending on whether the intermediate layer 324 is etched to define the cavity 340. In some cases, etching can be performed using a selective etchant that reaches the substrate through one or more openings (not shown) provided in the piezoelectric layer 310.

[0081] In this case, the diaphragm 315 (which may correspond, in an exemplary aspect, to, for example) Figure 1A The diaphragm 115 can be continuous with most of the remaining portion of the perimeter of the piezoelectric layer 310 surrounding the cavity 340. For example, the diaphragm 315 can be continuous with at least 50% of the remaining portion of the perimeter of the piezoelectric layer 310 surrounding the cavity 340. Figure 3B As shown, the cavity 340 extends completely through the intermediate layer 324. That is, the diaphragm 315 may have an outer edge facing the piezoelectric layer 310, wherein at least 50% of the edge surface of the diaphragm 315 is coupled to the edge of the piezoelectric layer 310 facing the diaphragm 315. This configuration provides increased mechanical stability to the resonator.

[0082] In other configurations, the cavity 340 may extend partially into the intermediate layer 324, but not completely through it (i.e., the intermediate layer 324 may extend over the bottom of the cavity on top of the substrate 322) or may extend through the intermediate layer 324 and (partially or entirely) into the substrate 322. As described above, it should be understood that, according to the various exemplary aspects, the interlaced fingers of the IDT may be provided... Figure 3A and Figure 3B On any or both surfaces of the diaphragm 315 in the middle.

[0083] Figure 4 This is a graphical illustration of the main excitation acoustic modes of interest in XBAR. Figure 4 A small portion of the XBAR 400 is shown, including a piezoelectric layer 410 and three interleaved IDT fingers 430. Generally, according to exemplary aspects, the exemplary configuration of the XBAR 400 may correspond to that described above and... Figures 2A to 2D The configuration shown is as described. Therefore, it should be understood that piezoelectric layer 410 may correspond to piezoelectric layer 110, and IDT fingers 430 may be implemented according to any configuration of, for example, fingers 238a and 238b.

[0084] In operation, an RF voltage is applied to the interlaced fingers 430. This voltage generates a time-varying electric field between the fingers. The direction of the electric field is transverse (i.e., laterally excited), or primarily parallel to the surface of the piezoelectric layer 410, as indicated by the arrow labeled “Electric Field”. Due to the high dielectric constant of the piezoelectric layer 410, the electric field is highly concentrated within the piezoelectric layer relative to air. The transverse electric field introduces shear deformation in the piezoelectric layer 410, thus strongly exciting shear acoustic modes within the piezoelectric layer 410. In this context, “shear deformation” is defined as the deformation of parallel planes in a material that remain parallel and at a constant distance while being translated relative to each other. In other words, the parallel planes of the material are laterally displaced relative to each other. A “shear acoustic mode” is defined as an acoustic vibration mode in a medium that causes shear deformation of the medium. The shear deformation in the XBAR 400 is represented by curve 460, where adjacent small arrows provide a schematic indication of the direction and amplitude of atomic motion. Note that, for ease of reference... Figure 4 The visualizations in the image, the degree of atomic motion, and the thickness of the piezoelectric layer 410 have been exaggerated. While atomic motion is primarily lateral (i.e., as shown in the image),... Figure 4 (As shown in the horizontal direction), but the direction of the acoustic energy flow that primarily excites the shear acoustic mode is substantially and / or primarily orthogonal to the surface of the piezoelectric layer, as indicated by arrow 465.

[0085] Shear wave-based bulk acoustic resonators can achieve better performance than current state-of-the-art thin-film bulk acoustic resonators (FBARs) and solid-mounted resonator bulk acoustic wave (SMR BAW) devices that apply an electric field in the thickness direction. In this device, the acoustic modes are compressed, with the direction of atomic motion and acoustic energy flow in the thickness direction. Furthermore, the piezoelectric coupling of shear wave XBAR resonators can be higher (>20%) compared to other acoustic resonators. Therefore, high piezoelectric coupling enables the design and implementation of microwave and millimeter-wave filters with considerable bandwidth.

[0086] Figure 5AThis is a schematic circuit diagram and layout of a high-frequency bandpass filter 500 using an XBAR (such as the aforementioned general XBAR configuration 100, e.g., bulk acoustic resonators). The filter 500 has a conventional trapezoidal filter architecture (which may include a segmented trapezoidal filter architecture in which the filter is divided among multiple chips), which has multiple bulk acoustic resonators, including four resonators 510A, 510B, 510C, and 510D, and three parallel resonators 520A, 520B, and 520C. Series resonators 510A, 510B, 510C, and 510D are connected in series between the first and second ports (hence the term "series resonators"). Figure 5A In this design, the first and second ports are labeled "In" and "Out," respectively. However, filter 500 is bidirectional, and either port can be used as either the input or output of the filter. At least two parallel resonators (such as parallel resonators 520A and 520B) are connected from the node between the series resonators to ground. The filter may contain... Figure 5A Additional reactive components, such as inductors, are not shown. In an exemplary aspect, all parallel and series resonators are XBARs (e.g., any of XBAR configurations 100 and / or 100' as described above). Including three series resonators and two parallel resonators is an example. Filters may have more or fewer than five resonators in total, more or fewer than three series resonators, and more or fewer than two parallel resonators. Typically, for both split and non-split trapezoidal filter architectures, all series resonators are connected in series between the filter's input and output, and all parallel resonators are typically connected between ground and the nodes of the input, output, or two series resonators.

[0087] In the exemplary filter 500, the series resonators 510A, 510B, 510C, and 510D, and the parallel resonators 520A, 520B, and 520C of the filter 500 can be formed on at least one (and in some cases a single) piezoelectric layer 530 of piezoelectric material bonded to a silicon substrate (not visible). Alternatively, however, each resonator can be formed on a separate, respective piezoelectric layer for each resonator, wherein all resonators are located on the same chip. However, in some cases, for example, the different resonators of the filter can be bonded to separate substrates. This can produce a segmented trapezoidal architecture that can include one or more separate chips comprising separate piezoelectric layers and IDTs for one or more bulk acoustic resonators, which are then configured together to form the entire segmented trapezoidal filter. Furthermore, each resonator includes a corresponding IDT (not shown), wherein at least the fingers of the IDT are disposed above a cavity or acoustic mirror in the substrate. In this context and similar contexts, the term "corresponding" means "to relate things to each other," that is, to have a one-to-one correspondence. Figure 5A In the diagram, the cavity is schematically shown as a dashed rectangle (e.g., rectangle 535). In this example, each IDT is positioned above the corresponding cavity. In other filters, the IDTs of two or more resonators may be positioned above a single cavity.

[0088] Each of the resonators 510A, 510B, 510C, 510D, 520A, 520B, and 520C in filter 500 exhibits a resonant frequency with very high admittance (also interchangeably referred to as the Y-parameter) and an anti-resonant frequency with very low admittance. Resonance and anti-resonance occur at the resonant and anti-resonant frequencies, respectively, and for each resonator in filter 500, the resonant and anti-resonant frequencies may be the same or different. In short, each resonator can be considered a short circuit at its resonant frequency and an open circuit at its anti-resonant frequency. At the resonant frequencies of the parallel resonators and the anti-resonant frequencies of the series resonators, the input-output transfer function will approach zero. In a typical filter, the resonant frequencies of the parallel resonators are below the lower edge of the filter's passband, and the anti-resonant frequencies of the series resonators are above the upper edge of the passband.

[0089] The frequency range between the resonant frequency and the anti-resonant frequency of a resonator corresponds to the coupling of the resonator. Depending on the design parameters of filter 500, each of resonators 510A, 510B, 510C, 510D, 520A, 520B, and 520C can have specific coupling parameters, and the corresponding resonator is tuned to those coupling parameters to achieve the frequency response required by filter 500.

[0090] According to an exemplary aspect, each of the series resonators 510A, 510B, 510C, and 510D, and the parallel resonators 520A, 520B, and 520C, may have the features described above. Figures 1A to 2D The described XBAR configuration, wherein a diaphragm with IDT fingers spans over the cavity. Alternatively, each of the series resonators 510A, 510B, 510C, 510D and the parallel resonators 520A, 520B, and 520C can have an XBAR configuration, wherein the series resonators 510A, 510B, 510C, 510D and / or the parallel resonators 520A, 520B, and 520C can be securely mounted on or above the Bragg mirror (e.g., as shown in the image). Figure 2E As shown, the Bragg mirror can then be mounted on a substrate.

[0091] Figure 5B This is a schematic diagram of an RF module including an acoustic wave filter device, based on an exemplary aspect. Specifically, Figure 5B An RF module 540, including one or more acoustic filters 544, is shown according to an exemplary aspect. The RF module 540 also includes RF circuitry (or RF lines) 543. In an exemplary aspect, as described above regarding... Figure 5A As described, acoustic filter 544 may include one or more of filters 500, which include XBARs (e.g., bulk acoustic resonators described herein).

[0092] Figure 5B The acoustic filter 544 shown includes terminals 545A and 545B (e.g., a first terminal and a second terminal). Terminals 545A and 545B can be used as, for example, input and output contacts of the acoustic filter 544. Although two terminals are shown, any suitable number of terminals can be implemented for a particular application. The acoustic filter 544 and the RF circuit 543 are... Figure 5B The package substrate 546 (e.g., a common substrate) is used. The package substrate 546 may be a laminated substrate. Terminals 545A and 545B can be electrically connected to contacts 547A and 547B on the package substrate 546 via electrical connectors 548A and 548B, respectively. Electrical connectors 548A and 548B may be, for example, bumps or wiring connections. In an exemplary aspect, the acoustic filter 544 and the RF circuit 543 may be packaged together within a common package, with or without using the package substrate 546.

[0093] RF circuitry 543 may include any suitable RF circuitry. For example, RF circuitry may include one or more radio frequency amplifiers (e.g., one or more power amplifiers and / or one or more low-noise amplifiers), one or more radio frequency switches, one or more additional RF filters, one or more RF couplers, one or more delay lines, one or more phase shifters, or any suitable combination thereof. RF circuitry 543 may be electrically connected to one or more acoustic wave filters 544. RF module 540 may include one or more package structures to, for example, provide protection and / or facilitate easier handling of RF module 540. Such package structures may include overmolded structures formed over package substrate 546. Overmolded structures may encapsulate some or all of the components of RF module 540.

[0094] As described above, the pitch p is the center-to-center spacing between adjacent IDT fingers extending from different busbars. Furthermore, the mark is the width of a given finger of the IDT. That is, each finger of the IDT has a mark (e.g., Figure 2A The width w in the mark can usually be measured in the same direction as the pitch, which is usually orthogonal to the direction in which the interlacing fingers extend from the corresponding generatrix. Figure 1A The exemplary aspect shown can be considered, for example, to have a pitch and marking that are substantially constant over the length L of the IDT 130.

[0095] However, since the primary acoustic modes of an XBAR are predominantly bulk-wave characteristics, this configuration can result in a weak frequency dependence on the pitch and marking. Therefore, the pitch, marking, or chirp (or variation of both) in the XBAR's IDT can be used to suppress unwanted spurious amplitudes to achieve small-signal or large-signal performance gains that would otherwise depend on pitch and / or marking, such as metallic and propagating modes, while only slightly widening the primary mode resonance. It should be noted that, in general, IDT chirp is defined by pitch variation (e.g., multi-pitch) or marking variation (e.g., multi-mark) along the device length.

[0096] Figure 6 This is a plan view of a multi-marker, multi-pitch IDT 600 according to an exemplary aspect. A “multi-marker IDT” is an IDT where the markings of the IDT fingers vary along the length of the IDT. Similarly, a “multi-pitch IDT” is an IDT where the pitch of the IDT fingers varies along the length of the IDT. As shown, the multi-marker IDT 600 includes a first busbar 632 and a second busbar 634, and a plurality of interlaced fingers 636 extending alternately from the first busbar 632 and the second busbar 634. Generally, it should be understood that the busbars 632 and 634 may correspond to those described above. Figure 1ABusbars 132 and 134. Furthermore, interlaced fingers 636 can correspond to, for example, fingers 136 of IDT 130. The main difference is that IDT 600 has an interlaced finger configuration as multiple markings and multiple pitches.

[0097] As further shown, the multi-marker IDT 600 is divided into three parts along its length L, designated as part A, part B, and part C. In an exemplary aspect, parts A, B, and C can generally be considered as a first part, a second part, and a third part, respectively, wherein the second part is the central part located between the first and third parts in the length direction of the IDT. In another exemplary aspect, parts A, B, and C can generally be considered as a first part, a last part, and a central part located between the first and last parts in the length direction of the IDT. In either case, it should be understood that, alternatively, the IDT 600 may include more than three separate parts.

[0098] In the exemplary aspect, each of segments A, B, and C includes 20 fingers, and the multi-marker IDT 600 has a total of 60 fingers. The use of three segments and 60 fingers is exemplary. The IDT may have more or fewer than the total of 60 fingers. For example, according to the exemplary aspect, each segment of the IDT 600 may have fewer fingers, as long as each segment is considered to have at least two pairs of staggered fingers (i.e., a total of four fingers, or a total of at least three staggered fingers, wherein the second finger is counted twice—once for the first pair and once for the second pair). Furthermore, in the exemplary aspect, the total number of fingers may be divided substantially equally between two or more segments (e.g., segment A and segment B). In this context, "substantially" means "as close as possible." For example, an IDT with 100 fingers divided into three segments with 33, 34, and 33 fingers is considered substantially equal. However, the total number of fingers can also be divided unequally between two or more parts.

[0099] In an exemplary aspect of IDT 600, the fingers in portion B have a mark m, which can be considered a nominal mark of IDT 600. The fingers in portion A have a mark m(1-δ) m ), and some of the C-shaped fingers have the marking m(1+δ) m In an exemplary aspect, δ m It can be greater than 0 and less than or equal to 0.05. Furthermore, δ mTypically, it can be less than 0.01 and can be selected during filter design to achieve the most effective reduction of spurious modes. In an exemplary aspect, when the IDT is divided into two or more parts, the maximum value can be m(1+δ). m And the minimum label can be m(1-δ) m ).

[0100] As further shown, the fingers in portion B have a pitch p, which can be considered as the nominal pitch of IDT 600. The fingers in portion A can have a pitch p(1-δ) p Furthermore, some of the C-shaped fingers can have a pitch p(1+δ) p In this respect, δ p It can be greater than 0 and less than or equal to 0.10. Furthermore, δ p Typically, it can be less than 0.01 and can be selected during filter design to achieve the most effective reduction of spurious modes.

[0101] In the example multi-marker multi-pitch IDT 600, the marks and pitch can monotonically increase from left to right (as shown in the figure). Therefore, the IDT 600 typically exhibits a chirped profile where the chirped pattern (i.e., the increasing variation of the pitch and / or marks) varies linearly along the length of the IDT. However, as will be discussed below, in exemplary aspects of this disclosure, the IDT and / or one or more portions of the IDT may have a chirped pattern with a non-linear (e.g., concave in or concave out) profile. In this document, the pitch profile and / or mark profile may be referred to together or separately as a chirped profile. For example, a pitch profile may refer to the shape of a line fitting points on a graph having a pitch on one axis and the position of IDT fingers along the length of the IDT on another axis. Similarly, a mark profile may refer to the shape of a line fitting points on a graph having marks on one axis and the position of IDT fingers along the length of the IDT on another axis. Examples of pitch profiles can be found at least in… Figure 7A , Figure 8A , Figure 8B and Figure 9A As seen in the figure, even if a portion or sub-portion with at least three interlaced fingers has the same pitch, a shape showing pitch variation (i.e., pitch profile) can be observed.

[0102] Figure 7AThis is a graphic 700A showing the IDT chirp profile based on the position along the length of multiple IDTs according to an exemplary aspect. Generally, in the exemplary aspect, the X-axis represents the position along the length of the IDT, which can be represented as "x". Thus, x ranges from -1 to +1, where x=0 at the center position of the IDT. The Y-axis represents the relative IDT chirp (variation of pitch and / or variation of markings) for a given position along the length of the IDT.

[0103] As further shown, line 740A illustrates, for an IDT with linear chirp variation, the adjustment (also referred to as variation) based on the pitch (or marking) at the position along the length of the IDT, as described above regarding, for example... Figure 6 The pitch is described above, wherein the pitch is from p(1-δ) in part A. p The linear increase to p in part B, and to p(1+δ) in part C p ), and / or similarly, labeling p(1-δ) from part A m The linear increase extends to m in part B and to p(1+δ) in part C. m In contrast, lines 740B and 740C illustrate IDTs for acoustic resonator devices with chirped modes exhibiting nonlinear profiles.

[0104] More specifically, line 740B illustrates, for an IDT with a “recessed” chirped profile, an adjustment (i.e., variation) based on the pitch (or marking) at a position along the length of the IDT, wherein the variation in pitch and / or marking is gentler towards the center of the IDT (relative to its total length) and steeper at the edges of the IDT farther from the center. On the other hand, line 740C illustrates, for an IDT with a “recessed” chirped profile, an adjustment (i.e., variation) based on the pitch (or marking) at a position along the length of the IDT, wherein the variation in pitch and / or marking is steeper towards the center of the IDT (relative to its total length) and gentler at the edges of the IDT farther from the center.

[0105] According to the exemplary aspects described above, the pitch and / or chirp (or variation) of the IDT of the XBAR suppresses unwanted spurious amplitudes to achieve small-signal or large-signal performance gains. Figure 7B The above shows the illustration regarding... Figure 7B A graph 700B depicts the performance differences between the linear chirped profile 740A, the recessed chirped profile 740B, and the indented chirped profile 740C. The graph was simulated using the finite element method (FEM) technique, where the X-axis represents the resonant frequency (in MHz) and the Y-axis represents the real part of the admittance Y (in dB) as a function of frequency.

[0106] As shown in Figure 700B, three chirp profiles with the same chirp amplitude are compared, and the degree of suppression varies greatly among the profiles for unwanted spurious modes. In this example, the "recessed" chirp profile exhibits the best spurious suppression, which can be perceived by the fewest peaks in the corresponding frequency response, especially at the upper and lower edges of the passband.

[0107] Therefore, return to the reference. Figure 7A An IDT can typically be divided into at least two parts, and in this case, the IDT is... Figure 7A The figure 700A is shown in relation to the above regarding Figure 6 The description is similar, divided into three parts 710, 720, and 730. Therefore, according to an exemplary aspect, an acoustic resonator is provided comprising a piezoelectric layer and an interdigital transducer (IDT) located on the surface of the piezoelectric layer. In this aspect, the IDT may have a plurality of interlaced fingers extending alternately from a first busbar and a second busbar. That is, the IDT may include at least three parts, including a first part 710, a last part 730, and a central part 720 disposed in the length direction of the IDT between the first part 710 and the last part 730. Alternatively, the three parts may be considered as a first part 710, a second part 720, and a third part 730.

[0108] Although in graphic 700A at least three portions are visually shown as having substantially similar lengths, it should be understood that each of the first portion 710, the central portion 720, and the final portion 730 may have different numbers of fingers than each other, provided that each of the at least three portions has a corresponding length including at least two pairs of interlaced fingers in each portion.

[0109] Related to the above Figure 6 The configuration of the IDT 600 described is different. Figure 7A The nonlinear chirp profiles 740B and 740C of the exemplary aspects shown include one or more portions of an IDT having a nonlinear chirp profile. Thus, according to the exemplary aspects, at least one portion of the first portion 710 and the last portion 730 of each IDT includes a nonlinear chirp profile, such that the variation of at least one of the marking and pitch of the at least one portion is nonlinear over the length of the at least one portion. As described above, the marking is the width of each of at least two pairs of interlaced fingers, and the pitch is the center-to-center spacing between each pair of interlaced fingers. As further shown, the central portion 720 has a pitch or marking profile different from that of the at least one portion (e.g., either portion 710 or 730). As will be described in more detail below, the at least one portion can be configured to have a nonlinear chirp profile to effectively suppress "hot spots" of spurious modes.

[0110] According to an exemplary aspect, line 740B shows a recessed chirped profile. In this case, at least the first portion 710 and the last portion 730 of the IDT include recessed non-linear chirped profiles, such that the change in at least one of the marking and pitch of each of the first portion 710 and the last portion 730 is gentler towards the central portion 720 and steeper as the respective portion extends away from the central portion 720. In this aspect, the change in at least one of the marking and pitch of both the first portion 710 and the last portion 730 can be represented by A(x), where, Where k > 0 and x is between -1 and +1, it represents the length of the IDT. Furthermore, K is a measure of the curvature of the nonlinear chirped profile (e.g., a hyperbola), such as... Figure 7A As shown above regarding... Figure 1A In one exemplary aspect, the length of the IDT is the center-to-center distance L between the outermost fingers of the IDT.

[0111] According to another exemplary aspect, line 740C shows a concave chirped profile. In this case, at least the first portion 710 and the last portion 730 of the IDT include concave, non-linear chirped profiles, such that the change in at least one of the marking and pitch of each of the first portion 710 and the last portion 730 is steeper towards the central portion 720 and becomes gentler as the respective portions extend away from the central portion 720. In this aspect, the change in at least one of the marking and pitch of both the first portion 710 and the last portion 730 is represented by A(x), where: , where k>0 and x is between -1 and +1, which again represents the length of the IDT. Note that although line 740B shows an outward chirped profile of the IDT and line 740C shows an inward chirped profile of the IDT, alternatively, the first portion 710 may have an inward chirped profile and the last portion 730 may have an outward chirped profile, and vice versa.

[0112] Figure 7C A graph 700C is provided showing the ratio of the effect of chirp on different vibration modes of an acoustic resonator. The graph was simulated using the finite element method (FEM) technique, where the X-axis represents the resonant frequency (in MHz) and the Y-axis represents the real part of the admittance Y (in dB) as a function of frequency.

[0113] Specifically, Figure 700C illustrates how pitch variation affects the master mode (e.g., the primary excitation acoustic mode) and other spurious modes. For each spurious mode at different frequencies, the following is illustrated: Values ​​(discussed below). Specifically, Figure 700C illustrates two spurious categories: (i) chirpable (e.g., values ​​"0.93", "1.0", "1.5", "0.95", "1.3", and "0.89") and (ii) main XBAR main (e.g., value "0.11"). For the purposes of this disclosure, "chirpable" generally refers to the undesirable spurious effect of pitch variation (i.e., pitch chirp) on the resonant frequency response.

[0114] According to an exemplary aspect, the spurious response to chirp can be evaluated based on the following ratios:

[0115]

[0116] In this respect, It is the nominal pitch of the acoustic resonator device, and This is the nominal spurious frequency. Furthermore, It is a change in frequency, and This refers to the pitch variation. As shown in the figure and according to an exemplary aspect, the spurious category of the main XBAR mode has a value of less than 0.25. .

[0117] Furthermore, for chirpable spurious or SAW devices, ≈1, where the resonant frequency of the resonator device is primarily controlled by the pitch of its IDT. However, for the bulk acoustic resonator described herein according to an exemplary aspect, the main excited master acoustic mode has ≈0.1, and in this particular exemplary case, The value is 0.11.

[0118] Therefore, in an exemplary aspect, The precise value typically depends on the ratio of the IDT pitch to the piezoelectric layer thickness. Exemplary acoustic resonator devices of the spurious category in the master XBAR mode have a small pitch-to-piezoelectric layer thickness ratio (e.g., ~5.3), therefore, for typical XBAR devices, The value will be in a high range. However, note that in other exemplary aspects, the upper limit of 0.25 can be reduced, and the interval between chirpable and non-chirpable can be widened.

[0119] Therefore, according to Figure 7C The exemplary aspect shown in Figure 700C, when When the frequency is close to or greater than 1, specific unwanted frequencies become more "chirable," while the main XBAR mode has a frequency of less than 0.25. In practice, compared to SAW devices, the effect of pitch (or marking) variation on the XBAR master mode is less than 25%. In other words, the effect of pitch and / or marking variation on the primary excitation acoustic mode of the acoustic resonator device according to the exemplary aspects described above is less than 25%, compared to a 1:1 effect of pitch and / or marking on the master mode. That is, the effect of pitch variation on the master A1 mode of the acoustic resonator according to the exemplary acoustic resonator device described herein is less than 25%, compared to a 1:1 effect of at least one of pitch and marking on modes other than the primary excitation acoustic mode and associated frequencies. As for marking, while marking variation can help balance the effect of pitch variation, the effect may not be significantly different in the master mode from other modes.

[0120] Figure 8A This is a graphic 800A showing the IDT chirp profile based on position along the length of the IDT, according to another exemplary aspect. Again, in the exemplary aspect, the X-axis represents the position along the length of the IDT, which can be represented as "x". Thus, x ranges from -1 to +1, where x=0 at the center of the IDT. The Y-axis represents the relative IDT chirp for a given position along the length of the IDT. Specifically, in the exemplary aspect, the Y-axis represents the relative IDT chirp for a pitch (in µm) in the range of 1.500 µm to 1.700 µm. In this exemplary aspect, the marker is shown as being constant at 0.44 µm along the length of the IDT. However, in another exemplary aspect, the marker may have a linear gradient (at least in linear segments) opposite to the pitch variation to balance the chirp profile, except where the pitch increases exponentially towards the ends of the IDT.

[0121] Therefore, according to Figure 8A In an exemplary aspect, the chirp profile is asymmetric and provides large chirp gradients only at hotspots of stray modes (e.g., the local curvature of selected sub-parts of the IDT). In other words, the pitch chirp of the IDT is substantially linear, except that the nonlinear portion is limited to sub-parts of the IDT. Note that the term "substantially linear" indicates that the pitch chirp increases, for example, in a linear manner, taking into account possible variations in this linearity due to manufacturing tolerances (e.g., ±5%). Furthermore, with Figure 7A The graphic is similar to that of the 700A. Figure 8A The illustrated IDT profile can be divided into three sections 810, 820, and 830. That is, an acoustic resonator is provided, comprising a piezoelectric layer; and an IDT, on the surface of the piezoelectric layer. In this respect, the IDT may have a plurality of interlaced fingers extending alternately from a first busbar and a second busbar (e.g., busbars 632 and 634).

[0122] An IDT may include at least three portions, including a first portion 810, a final portion 830, and a central portion 820 disposed along the length of the IDT between the first portion 810 and the final portion 830. Alternatively, the three portions may be considered as a first portion 810, a second portion 820, and a third portion 830. Furthermore, it should be understood that each of the first portion 810, the second portion 820, and the third portion 830 may be divided into one or more sub-portions. While the pitch and / or marking of each portion is chirped as described herein, within each portion, the sub-portions may have a constant pitch or marking. In other words, each of the first portion 810, the second portion 820, and the third portion 830 may include multiple sub-portions, each sub-portion having at least three interlaced fingers having at least one of a constant marking and a constant marking. In other words, each sub-portion may include three or more interlaced fingers having the same pitch and / or the same marking within that sub-portion. Figure 8A The diagram shows each small horizontal dashed line of the marker as an exemplary aspect that is constant for multiple fingers.

[0123] According to an exemplary aspect, Figure 8A The chirp profile of the IDT is configured such that the pitch (or marking profile) of the central portion 720 (e.g., the middle of the IDT) is substantially linear (e.g., with a first changing slope), and the pitch of at least one of the final portions 730 changes with the final portion 730 extending away from the central portion 720 along the length direction of the IDT (e.g., a second changing slope). In this exemplary aspect, the chirp profile of the first portion 710 is shown to be substantially linear. Therefore, in this exemplary aspect, the first portion 710 and the central portion 720 can be considered as single portions having the same linear chirp profile. In this aspect, the first portion 710 and / or the central portion 720 have a pitch (or marking) with a first profile or slope (e.g., linear or substantially linear), and the third portion or the final portion 730 has a second profile or slope (e.g., exponential), which is different from and generally greater than the first profile or slope, as described herein and for example... Figure 8A As shown.

[0124] Figure 8BFigure 800B illustrates, according to the exemplary aspects described herein, a diagram of graph 800C showing which sub-sections of an IDT should have a non-linear chirped configuration relative to the acoustic intensity. Importantly, the sub-sections of the IDT that should have a non-linear chirped profile are determined based on the confinement of acoustic energy to a spatial segment of the IDT due to chirping. In other words, the “hot spots” shown in Figure 800B indicate where the chirped profile variation should be amplified to reduce the amplitude of the hot spots, which are identified by circles. Based on the hot spots that an IDT with a linear IDT chirped profile would otherwise experience, sub-sections of the IDT can be chirped to have a rapidly increasing slope at the edges, as... Figure 8A The third or final portion 830 is shown. In each example in Figures 800A and 800C, the total number of fingers of the IDT is shown as 160, with portion 830 starting approximately at the 120th finger of the IDT. Thus, in an exemplary aspect, the number of interlaced fingers in a portion (e.g., portion 83) with a non-linear chirped profile is 25% or less of the total number of fingers in the plurality of interlaced fingers of the IDT.

[0125] Figure 8C Three graphs are shown, illustrating the pitch profile p(x), the first derivative, and the second derivative of the profile p(x) of an IDT with the chirped profile shown in Graph 800A. In general, the first derivative of a function gives the slope of the graph at a point, while the second derivative indicates whether the curve is concave upwards or downwards at that point. If the second derivative is positive, the graph bends upwards at that point, and if the second derivative is negative, the graph is concave downwards. The second derivative also indicates the shape of the graph and the concavity and inflection points of the function's graph.

[0126] exist Figure 8C In the figure, the pitch profile p(x) is shown in Figure 850A, the first derivative of the pitch profile p(x) is shown in Figure 850B, and the second derivative of the pitch profile p(x) is shown in Figure 850C. As mentioned above, the pitch profile p(x) shown in Figure 850A can generally correspond to Figure 8AThe pitch profile in Figure 800A is shown. Furthermore, the first derivative shown in Figure 850B indicates that the pitch profile p(x) is monotonic (e.g., completely non-decreasing), and the sign can be positive or negative. As used herein, a pitch profile can be "monotonic" if it is completely non-decreasing or completely non-increasing. A monotonically increasing pitch profile does not necessarily have to be increasing, but it cannot be decreasing, and vice versa for a monotonically decreasing pitch profile. Finally, the second derivative shown in Figure 850C indicates that concavity is the same sign. Thus, according to the exemplary aspect, the last or third portion 830 of the IDT has a chirped profile configured such that the first mathematical derivative of the nonlinear chirped profile is of the same sign and monotonically increasing, and the second mathematical derivative of the nonlinear chirped profile is non-zero and of the same sign and exponentially increasing. Furthermore, the first portion 810 and the central portion or the second portion 820 have chirped profiles that vary substantially linearly along the respective lengths of each portion as described above. Note that the first and second derivatives of the exemplary nonlinear chirped profiles are typically estimated, and the actual chirped profiles may vary in practice, taking into account, for example, manufacturing tolerances.

[0127] Furthermore, it should be emphasized again that although three sections 810, 820, and 830 are shown in the exemplary embodiment, the IDT in this example typically has an asymmetric chirped profile, such that the pitch (and / or marking) variation of one of the sections (e.g., the last section 830) is non-linear over the length of that section. Additionally, a second section of the IDT (e.g., the central section 820, or a combination of the first section 810 and the central section 820) has a substantially linear pitch profile that differs from the asymmetric chirped profile of said section.

[0128] Figure 9A This is a graphic 900A showing the IDT chirp profile based on the position along the length of the IDT, according to another exemplary aspect. Again, in the exemplary aspect, the X-axis represents the position along the length of the IDT, which can be represented as "x". Therefore, x ranges from -1 to +1, where X=0 at the center of the IDT. In this example, the IDT has approximately 160 fingers, so X=0 would be approximately at finger ID 80. Furthermore, the Y-axis represents the relative IDT chirp for a given position along the length of the IDT. Specifically, in the exemplary aspect, the Y-axis represents the relative IDT chirp for a pitch (in µm and represented by multiple "O") in the range of 1.5525µm to 1.5725µm. In this exemplary aspect, the markings (represented by multiple "X") are shown as constant at 0.44µm along the length of the IDT, but alternatively, the markings can vary linearly or non-linearly.

[0129] Therefore, the above about Figure 7A and Figure 7B The described hyperbolic or nonlinear profile is not necessarily monotonic. Instead, Figure 900A shows a hyperbolic triangle with a large gradient at the edges to provide good spurious suppression at local hotspots and also provides symmetry for good harmonic cancellation characteristics. As shown, the maximum pitch is at the center of the IDT and decreases exponentially towards the outer edge of the IDT.

[0130] therefore, Figure 9A The exemplary embodiment shown provides an IDT having at least a first portion and a second portion (generally shown as the left and right sides of a “finger ID”). In this respect, the staggered fingers of each of the first and second portions have an asymmetrical chirped profile, such that the variation of at least one of the markings and pitch is non-linear over the length of the respective portion. Furthermore, the variation of at least one of the markings and pitch of each of the first and second portions increases exponentially as the respective lengths of each of the first and second portions extend toward each other (e.g., toward the peak or center of the IDT around the finger ID 80). Thus, in the exemplary aspect, the IDT as a whole (e.g., as a whole) has a symmetrical chirped profile, which is shown as a hyperbolic triangle.

[0131] Figure 9B This is a graph of the IDT chirp profile based on the position along the length of the IDT, according to another exemplary aspect. Note that graph 900B provides an IDT chirp profile similar to that of graph 900A, where the profile is a function of the position along the length of the IDT. Similarly, the markings (represented by multiple "X"s) are shown as being constant at 0.44 µm along the length of the IDT, but alternatively, the markings may vary linearly or non-linearly.

[0132] Therefore, the above about Figure 7A and Figure 7B The described hyperbolic or nonlinear profile is not necessarily monotonic. However, instead of the hyperbolic triangle of Figure 900A, Figure 900B includes a pitch distribution that flattens out (approximately zero) in the middle of the IDT length, followed by larger gradients at the edges to provide good spurious suppression at local hotspots and to provide symmetry for good harmonic cancellation characteristics. Similarly, the maximum pitch is at the central portion of the IDT and decreases exponentially towards the outer edges of the IDT.

[0133] therefore, Figure 9BThe exemplary embodiment shown provides an IDT having at least a first portion and a second portion (generally shown as the left and right sides of a “finger ID”). In this respect, the staggered fingers of each of the first and second portions have an asymmetrical chirped profile, such that the variation of at least one of the markings and pitch is non-linear over the length of the respective portion. Furthermore, the variation of at least one of the markings and pitch of each of the first and second portions increases as the respective lengths of each of the first and second portions extend toward each other (e.g., toward the center of the IDT around the finger ID 80), and then tends to level off before decreasing toward the edges. Thus, in the exemplary aspect, the IDT as a whole (e.g., as a whole) has a symmetrical chirped profile, which is essentially shown as an inverted U-shape.

[0134] Note that while Figures 900A and 900B show the pitch being minimum at the outer edge of the IDT, this configuration can be reversed. In other words, alternatively, the pitch at the outer edge of the IDT can be maximum, allowing the contours in Figures 900A and 900B to be effectively inverted.

[0135] Figure 9C Three graphs are shown illustrating the pitch profile p(x), the first derivative, and the second derivative of the profile p(x) of an IDT with the chirped profile shown in graph 900A. More specifically, the pitch profile p(x) is shown in graph 950A, the first derivative of the pitch profile p(x) is shown in graph 950B, and the second derivative of the pitch profile p(x) is shown in graph 950C. In an exemplary aspect, the pitch profile p(x) shown in graph 950A corresponds to... Figure 7A The pitch profile of concave line 740B is shown in Figure 950B. Furthermore, the first derivative shown in Figure 950B indicates that the pitch profile p(x) is monotonic, and the sign can be positive or negative. The second derivative shown in Figure 950C indicates that the concavity is of the same sign. It should be understood that the chirped profile is not necessarily symmetric about the center point of the IDT. It should also be noted again that the first and second derivatives used to plot the exemplary nonlinear chirped profiles are typically estimated, and the actual chirped profile can vary in practice, taking into account, for example, manufacturing tolerances.

[0136] According to an exemplary configuration, the pitch and / or marking chirp (or variation) of the IDT of a bulk acoustic resonator can be configured to suppress unwanted spurious amplitudes to achieve small-signal or large-signal performance gain. However, as the amplitude of the chirp increases, both the problematic spurious and the dominant A1 mode degrade. Therefore, to counteract this effect, the degradation of the A1 mode can be minimized by utilizing a balanced chirp. For example, if the dominant mode has a frequency response to the marking and pitch of... And select the chirp outline. Then you can select the corresponding chirp outline. , making The chirp is kept constant to minimize the degradation of the main mode. Therefore, even considering the chirp of the balance, it is beneficial to utilize the chirp profile that maximizes spurious suppression at the lowest cost to the main A1 mode, as those skilled in the art will understand.

[0137] Figure 10 A graph 1000 illustrating the effect on the A1 mode is shown, measured as a reduction in resonant Q that trades off with a reduction in spurious amplitude. The X-axis of graph 1000 shows the spurious amplitude, and the Y-axis shows the resonant Q. The optimal chirped surface is shown as a dashed line (i.e., maximizing resonant Q for a given spurious reduction). Linear chirping is shown as an "o" reference, and hyperbolic chirped profiles (i.e., concave and convex profiles) are shown as "+" references, where concave is dark gray and convex is light gray. As clearly shown, the convex chirped profile best matches the optimal chirped surface.

[0138] Generally speaking, it should be understood that, although the above regarding, for example Figure 8A Chirp pitch has been described, but the nonlinear chirp profile described herein can be combined with fully or partially balanced profiles, and the nonlinear chirp profile can be used for marking or pitch. Furthermore, the precise optimal shape (in terms of spurious suppression) can depend on a specific spurious mode (e.g., A0). n Pattern and S0 n model).

[0139] Throughout this specification, the embodiments and examples shown should be considered as examples and not as limitations on the disclosed or claimed apparatus. Although many of the examples presented herein involve specific combinations of elements, it should be understood that these actions and these elements can be combined in other ways to achieve the same objective.

[0140] Finally, as used herein, “a plurality of” means two or more. As used herein, a “set” of items may include one or more such items. As used herein, whether in the written description or in the claims, the terms “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” etc., should be understood as open-ended (i.e., meaning including but not limited to). Only the transitional phrases “consisting of…” and “substantially consisting of…” are closed or semi-closed transitional phrases relative to the claims, respectively. The use of sequential terms such as “first,” “second,” “third,” etc., to modify a claim element itself in a claim does not imply any priority, precedence, or order of one claim element relative to another claim element or the chronological order of actions of the method, but is merely used as labels to distinguish one claim element with a specific name from another element with the same name (but using sequential terms) to differentiate claim elements. As used herein, “and / or” indicates that the listed items are alternatives, but the alternatives also include any combination of the listed items.

Claims

1. An acoustic resonator, comprising: piezoelectric layer; An interdigital transducer (IDT) has multiple interlaced fingers extending alternately from a first busbar and a second busbar on the surface of the piezoelectric layer. The IDT comprises at least three parts, including a first part, a last part, and a central part disposed between the first part and the last part along the length direction of the IDT. Each of the at least three portions has a corresponding length comprising at least two pairs of interlaced fingers. Wherein, at least one of the first portion and the last portion of the IDT includes a non-linear chirp profile, such that the variation of at least one of the marking and pitch of the at least one portion is non-linear over the length of the at least one portion, the marking being the width of the at least two pairs of interlaced fingers, and the pitch being the center-to-center spacing between each pair of interlaced fingers, and Wherein, the first-order mathematical derivative of the nonlinear chirped profile of at least one part is monotonically increasing with the same sign, and the second-order mathematical derivative of the nonlinear chirped profile of at least one part is non-zero, and is exponentially increasing with the same sign.

2. The acoustic resonator according to claim 1, wherein, Both the first portion and the last portion of the IDT include a recessed non-linear chirped profile, such that the variation of at least one of the markings and pitches of each of the first portion and the last portion becomes gentler as the respective portion extends toward the central portion, and steeper as the respective portion extends away from the central portion.

3. The acoustic resonator according to claim 2, wherein, The change in at least one of the labeling and pitch of both the first part and the last part is represented by A(x), where: , where k>0 and measures the curvature of the nonlinear chirped profile, and x is between -1 and +1.

4. The acoustic resonator according to claim 1, wherein, Both the first portion and the last portion of the IDT include a concave, non-linear chirped profile, such that at least one of the markings and pitches of each of the first portion and the last portion changes steeper toward the central portion and becomes gentler as the respective portions extend away from the central portion.

5. The acoustic resonator according to claim 4, wherein, The change in at least one of the labeling and pitch of both the first part and the last part is represented by A(x), where: , where k>0 and measures the curvature of the nonlinear chirped profile, and x is between -1 and +1.

6. The acoustic resonator according to claim 1, wherein, Each of the central portion and the at least one portion includes a plurality of sub-parts, each sub-part having at least three interlaced fingers, wherein the at least three interlaced fingers have at least one of a constant pitch or a constant mark.

7. The acoustic resonator according to claim 1, wherein, The number of interlaced fingers in at least one portion is about 25% or less of the total number of fingers in the plurality of interlaced fingers of the IDT.

8. The acoustic resonator according to claim 7, wherein, The pitch of the at least one portion changes exponentially, and the pitch of the central portion changes relatively linearly with respect to the pitch of the at least one portion.

9. The acoustic resonator according to claim 8, wherein, The marker is substantially constant over the length of the IDT.

10. The acoustic resonator according to claim 8, wherein, The central portion comprises a generally linear chirped profile.

11. An acoustic resonator, comprising: piezoelectric layer; An interdigital transducer (IDT) has multiple interlaced fingers extending alternately from a first busbar and a second busbar on the surface of the piezoelectric layer. The IDT comprises multiple parts, each part having a corresponding length including at least two pairs of interlaced fingers. The IDT has an asymmetric chirped profile such that the variation of at least one of the markings and pitches of the first portion of the plurality of portions is non-linear over the length of the first portion, wherein the markings are the widths of the at least two pairs of interlaced fingers, and the pitches are the center-to-center spacing between each pair of interlaced fingers. Wherein, the change of at least one of the pitch and the marking has less than 25% of the effect on the main excitation acoustic mode of the acoustic resonator, compared to a 1:1 effect of at least one of the pitch and the marking on modes other than the main excitation acoustic mode.

12. The acoustic resonator according to claim 11, wherein, The second portion of the plurality of portions of the IDT has a pitch or marking profile that is substantially linear and different from the asymmetric chirped profile of the first portion.

13. The acoustic resonator according to claim 12, wherein, The plurality of portions of the IDT include a first portion, a second portion, and a third portion, wherein the second portion is a central portion located between the first portion and the third portion in the length direction of the IDT.

14. The acoustic resonator according to claim 13, wherein, Both the first and third portions of the IDT include concave, non-linear chirped profiles, such that at least one of the markings and pitches of each of the first and third portions becomes gentler as the respective portion extends toward the central portion and steeper as the respective portion extends away from the central portion.

15. The acoustic resonator according to claim 14, wherein, The change in at least one of the labeling and pitch of both the first part and the third part is represented by A(x), where: , where k>0 and measures the curvature of the nonlinear chirped profile, and x is between -1 and +1.

16. The acoustic resonator according to claim 13, wherein, Both the first and third portions of the IDT include concave, non-linear chirped profiles, such that at least one of the markings and pitches of each of the first and third portions becomes steeper towards the central portion and becomes gentler as the respective portions extend away from the central portion.

17. The acoustic resonator according to claim 16, wherein, The change in at least one of the labeling and pitch of both the first part and the third part is represented by A(x), where: , where k>0 and measures the curvature of the nonlinear chirped profile, and x is between -1 and +1.

18. The acoustic resonator according to claim 13, wherein: The pitch or marking profile of the second portion is substantially linear, and the variation of at least one of the marking and pitch of the first portion increases as the first portion extends away from the second portion along the length direction of the IDT. The first-order mathematical derivative of the asymmetric chirped profile of the first part is monotonically increasing with the same sign, and the second-order mathematical derivative of the asymmetric chirped profile of the first part is non-zero with the same sign and exponentially increasing.

19. The acoustic resonator according to claim 12, in, The number of interlaced fingers in the first portion is approximately 25% or less of the total number of fingers among the plurality of interlaced fingers of the IDT, and The pitch of the first part changes exponentially, and the pitch of the second part changes relatively linearly relative to the pitch of at least one part.

20. An acoustic resonator, comprising: piezoelectric layer; An interdigital transducer (IDT) has multiple interlaced fingers extending alternately from a first busbar and a second busbar on the surface of the piezoelectric layer. The IDT comprises a first part and a second part, each part having a corresponding length including at least two pairs of interlaced fingers. Wherein, the interlaced fingers of each of the first and second portions have an asymmetric chirped profile, such that the variation of at least one of the markings and the pitch is non-linear over the length of the respective portion, the marking being the width of the at least two pairs of interlaced fingers, and the pitch being the center-to-center spacing between each pair of interlaced fingers, and The pitch and at least one of the markings of each of the first and second portions vary exponentially as the respective lengths of each of the first and second portions extend toward each other, such that the IDT as a whole, including the first and second portions, has a symmetrical chirped profile.

Images