Acoustic resonator and filter device with dielectric series capacitor

Abstract

A filter device is provided comprising: an acoustic resonator with a substrate; a piezoelectric layer coupled to the substrate by one or more intermediate layers; and a conductor pattern on a surface of the piezoelectric layer, the conductor pattern comprising a pair of busbars with a plurality of interlocked fingers extending therefrom to form an interdigital converter (IDT). The filter device further comprises a dielectric capacitor electrically coupled in series with the acoustic resonator.The dielectric capacitor comprises a dielectric layer on a surface of a first busbar from the pair of busbars and at least one metal layer on a surface of the dielectric layer, such that the dielectric layer is located between the first busbar and the at least one metal layer to form the dielectric capacitor.

Description

Cross-reference to related registrations

[0001] The present application claims priority over U.S. Preliminary Patent Application No. 63 / 701,013, filed on September 30, 2024, and U.S. Preliminary Patent Application No. 19 / 340,237, filed on September 25, 2025, the entire contents of which are incorporated herein by reference. Technical field

[0002] This disclosure relates to high-frequency filters that use acoustic wave resonators and, in particular, to filters that use capacitors in series with acoustic resonators for use in communications equipment. background

[0003] An RF filter is a two-terminal device configured to pass some frequencies and block others, where "pass" means transmission with relatively little signal loss and "block" means blocking or significant attenuation. The frequency range passed by a filter is called the filter's "passband." The frequency range blocked by a filter is called the filter's "stopband." A typical RF filter has at least one passband and at least one stopband. The specific requirements for a passband or stopband may depend on the specific application.For example, a “passband” may in some cases be defined as a frequency range in which the insertion loss of a filter is better than a defined value such as 1 dB, 2 dB or 3 dB, while a “stopband” may be defined as a frequency range in which the rejection by a filter is greater than a defined value such as 20 dB, 30 dB, 40 dB or higher, depending on the application.

[0004] RF filters are used in communication systems where information is transmitted wirelessly. For example, RF filters are found in the RF input stages of cell phone base stations, mobile phones and computers, satellite transceivers and ground stations, Internet of Things (IoT) devices, laptops and tablets, fixed-point radio links, and other communication systems. RF filters are also used in radar systems and electronic warfare and information warfare systems.

[0005] Improvements to the RF filters in a wireless system can have a broad impact on the system's performance. RF filter enhancements can lead to improvements in system performance, such as larger cell size, longer battery life, higher data rates, greater network capacity, lower costs, improved security, and higher reliability. These improvements can be implemented at many levels of the wireless system, both individually and in combination, for example, at the RF module level, RF transceiver level, mobile or fixed subsystems level, or at the network level.

[0006] The desire for wider communication channel bandwidth inevitably leads to the use of higher-frequency communication bands. Radio access technology for mobile networks has been standardized by 3GPP (the 3rd Generation Partnership Project). Radio access technology for fifth-generation mobile networks is defined in the 5G NR standard (5G standard for new radio technology). The 5G NR standard defines several new communication bands. Two of these new communication bands are n77, which uses the frequency range from 3300 MHz to 4200 MHz, and n79, which uses the frequency range from 4400 MHz to 5000 MHz. Bandpass filters for the n77 and n79 bands must be capable of handling the transmit power of the communication device.However, current acoustic resonators exhibit excessive coupling for narrow bands, such as n79, and thus there is a need for improved filters that can operate with narrow frequency bands, and at the same time an improvement in the manufacturing processes for such filters. Brief description

[0007] As described here, an acoustic resonator and a filter device containing it are provided, wherein a capacitor is coupled in series with an acoustic resonator (e.g. an XBAR) to reduce the effective coupling of the resonator and shift the resonance upwards in frequency.

[0008] According to an exemplary embodiment, a filter device is provided comprising: an acoustic resonator with a substrate; a piezoelectric layer coupled to the substrate by one or more intermediate layers; and a conductor pattern on a surface of the piezoelectric layer, the conductor pattern comprising a pair of busbars with a plurality of interlocking fingers extending therefrom to form an interdigital converter (IDT);and a dielectric capacitor electrically coupled in series with the acoustic resonator, the dielectric capacitor comprising a dielectric layer on a surface of a first busbar from the pair of busbars and at least one metal layer on a surface of the dielectric layer, such that the dielectric layer is located between the first busbar and the at least one metal layer to form the dielectric capacitor.

[0009] In another exemplary aspect of the filter device, the first busbar is configured as a first electrode of the dielectric capacitor, and the at least one metal layer is configured as a second electrode of the dielectric capacitor, so that the dielectric layer is sandwiched between the first and the second electrode.

[0010] In another exemplary aspect of the filter device, the at least one metal layer is further arranged on the surface of the piezoelectric layer such that the at least one metal layer is essentially coplanar with the first busbar, and wherein a space extends between the at least one metal layer and the first busbar in a top view of the surface of the piezoelectric layer.

[0011] In another exemplary aspect of the filter device, the pair of busbars extends in a first direction, and the interlocking fingers extend in a second direction, which is substantially perpendicular to the first direction, and the gap extends in the first direction along a side surface of the first busbar facing a side surface of the at least one metal layer. Furthermore, the dielectric layer can be silicon oxide and is also arranged in the gap between the at least one metal layer and the first busbar.

[0012] In another exemplary aspect of the filter device, the at least one metal layer has a plurality of metal layers, and the at least one metal layer corresponds in a top view of the surface of the piezoelectric layer to a shape of the dielectric layer.

[0013] In another example, the filter device includes an additional dielectric capacitor electrically coupled in series with the acoustic resonator, wherein the additional capacitor comprises a dielectric layer on a surface of a second busbar from the pair of busbars and at least one metal layer on a surface of the dielectric layer opposite the second busbar to form the additional dielectric capacitor, such that the acoustic resonator is electrically coupled in series between the dielectric capacitor and the additional dielectric capacitor.

[0014] In another exemplary aspect of the filter device, a section of the piezoelectric layer forms a membrane located above a cavity that extends at least partially into one or more intermediate layers, wherein the one or more intermediate layers comprise silicon oxide or silicon dioxide, and the dielectric capacitor does not overlap with the cavity in a top view of the piezoelectric layer.

[0015] In another exemplary aspect of the filter device, one or more intermediate layers feature a Bragg mirror positioned between the piezoelectric layer and the substrate.

[0016] In another exemplary aspect of the filter device, the IDT is configured such that a high-frequency signal applied to the IDT excites a bulk shear acoustic wave in the piezoelectric layer, with acoustic energy propagating along a direction substantially orthogonal to the surface of the piezoelectric layer and transverse to a direction of an electric field generated by the entangled fingers of the IDT.

[0017] In another example, a filter device is provided comprising: an acoustic resonator with a substrate; a piezoelectric layer coupled to the substrate by one or more intermediate layers; an interdigital converter (IDT) on a surface of the piezoelectric layer, the IDT comprising a pair of busbars with a plurality of interlocking fingers extending therefrom; and a capacitor electrically coupled in series with the acoustic resonator and integrated as a section of a first busbar from the pair of busbars, the capacitor and a pair of metal layers and a dielectric layer being arranged between them.

[0018] In another exemplary aspect of the filter device, the pair of metal layers of the capacitor has a first busbar from the pair of busbars opposite the piezoelectric layer; and at least one metal layer on a surface of the dielectric layer opposite the first busbar.

[0019] In another exemplary aspect, the filter device comprises an additional dielectric capacitor electrically coupled in series with the acoustic resonator, wherein the additional capacitor is integrated as a section of a second busbar from the pair of busbars, the additional capacitor comprising a dielectric layer on a surface of a second busbar from the pair of busbars and at least one metal layer on a surface of the dielectric layer opposite the second busbar to form the additional dielectric capacitor, such that the acoustic resonator is electrically coupled in series between the dielectric capacitor and the additional dielectric capacitor.

[0020] In another exemplary aspect, a high-frequency module is provided comprising: a filter device with a plurality of acoustic wave resonators connected in parallel and a high-frequency circuit coupled to the filter device, wherein the filter device and the high-frequency circuit are housed in a common enclosure. In this aspect, at least one acoustic wave resonator from the plurality of acoustic wave resonators of the filter device comprises a substrate; a piezoelectric layer coupled to the substrate by one or more intermediate layers; and a conductor pattern on a surface of the piezoelectric layer, wherein the conductor pattern comprises a pair of busbars with a plurality of interlocked fingers extending therefrom to form an interdigital converter (IDT).Furthermore, the filter device also includes a dielectric capacitor electrically coupled in series with the acoustic resonator, wherein the dielectric capacitor comprises a dielectric layer on a surface of a first busbar from the pair of busbars and at least one metal layer on a surface of the dielectric layer, such that the dielectric layer is located between the first busbar and the at least one metal layer to form the dielectric capacitor.

[0021] The above simplified summary of exemplary aspects is intended to provide a basic understanding of the present disclosure. This summary is not a comprehensive overview of all aspects under consideration and is not intended to identify decisive or critical elements of any or all aspects, nor to define the scope of any or all aspects of the present disclosure. Its sole purpose is to present one or more aspects in simplified form as an introduction to the subsequent, more detailed description of the disclosure. To achieve this, one or more aspects of the present disclosure include the features described and exemplified in the claims. Brief description of the drawings

[0022] The accompanying drawings, which are included in and form part of this specification, illustrate one or more exemplary aspects of the present disclosure and, together with the detailed description, serve to explain its principles and implementations. Fig. Figure 1A includes a schematic top view and a schematic cross-sectional view of a transversely excited film bulk acoustic resonator (XBAR). Fig. Figure 1B shows a schematic cross-sectional view of an alternative configuration of an XBAR. Fig. 2A is an enlarged schematic cross-sectional view of a section of the XBAR from Fig. 1A. Fig. 2B is an enlarged schematic cross-sectional view of an alternative configuration of the XBAR. Fig. 1A. Fig. 2C is an enlarged schematic cross-sectional view of another alternative configuration of the XBAR. Fig. 1A. Fig. 2D is an enlarged schematic cross-sectional view of another alternative configuration of the XBAR. Fig. 1A. Fig. 2E is an enlarged schematic cross-sectional view of a section of a solidly mounted XBAR (SM XBAR). Fig. Figure 3A is a schematic cross-sectional view of an XBAR according to an exemplary aspect. Fig. 3B is an alternative schematic cross-sectional view of an XBAR according to an exemplary aspect. Fig. Figure 4 is a graphic representing a horizontal acoustic shear mode in an XBAR. Fig. 5A is a schematic block diagram of a filter using XBARs from Fig. 1A and / or 1B. Fig. Figure 5B is a schematic diagram of a high-frequency module comprising an acoustic wave filter device according to an exemplary aspect. Fig. Figure 6A is a schematic view of a section of a filter device comprising an acoustic resonator with a series-coupled dielectric capacitor, according to an exemplary aspect. Fig. 6B is a top view of the in Fig. Section 6A of the filter device shown from above. Fig. 6C is another schematic view of the in Fig. Section 6A of the filter device shown, according to an exemplary aspect. Fig. Figure 7 is a top view of a section of a filter device comprising an acoustic resonator with a pair of dielectric capacitors coupled in series, according to an exemplary aspect. Fig. Figure 8 is a diagram of the admittance of a filter device with one or more acoustic resonators (e.g., XBARs) as a function of frequency with a series-coupled dielectric capacitor according to an exemplary aspect. Fig. Figure 9A is a schematic view of a section of a filter device comprising an acoustic resonator coupled in series with a dielectric capacitor, according to a further exemplary aspect. Fig. 9B is a detailed schematic view of the in Fig. Section 9A of the filter device shown. Fig. Figure 10A is a schematic view of a section of a filter device comprising an acoustic resonator with a dielectric capacitor coupled in series, according to an exemplary aspect. Fig. 10B is a detailed schematic view of the in Fig. Section 9A of the filter device shown. Fig. Figures 11A to 11C are diagrams of admittance as a function of the frequency of the filter device according to exemplary aspects.

[0023] In this description, the elements depicted in the figures are consistently designated by three- or four-digit reference symbols, where the two lowest digits are specific to the element and the one or two highest digits are the number of the figure in which the element is first introduced. For an element not described in connection with a figure, it can be assumed that it has the same properties and function as the previously described element with the same reference symbol. Detailed description

[0024] Various aspects of the disclosed acoustic volume resonator, a filter device, a high-frequency module, and a method for manufacturing the same are now described with reference to the drawings, where identical elements are consistently designated by the same reference numerals. For explanatory purposes, numerous specific details are provided in the following description to contribute to a thorough understanding of one or more aspects of the disclosure. In some or all cases, however, it may be clear that the aspects described below can be implemented without using the specific construction details described below. In other cases, known structures and devices are shown in the form of block diagrams to facilitate the description of one or more aspects.The following is a simplified summary of one or more aspects of the invention to provide a basic understanding of it.

[0025] Fig. Figure 1A shows a simplified schematic top view and an orthogonal cross-sectional view of an acoustic volume resonator device, namely a transversely excited acoustic film volume resonator (XBAR) 100. XBAR resonators, such as the Resonator 100, can be used in a variety of RF filters, including bandstop filters, bandpass filters, duplexers, and multiplexers. XBARs are particularly suitable for use in filters for communication bands with frequencies above 3 GHz.

[0026] In general, the XBAR 100 comprises a conductor pattern (e.g., a thin-film metal layer) formed on one or both surfaces of a piezoelectric layer 110 (piezoelectric plate and piezoelectric layer can be used interchangeably here), with parallel front 112 and back 114 (generally also referred to as the first and second surfaces, respectively). It should be noted that the term "parallel" generally refers to the fact that the front 112 and back 114 are opposite each other and that the surfaces are not necessarily flat and exactly parallel. As experts will recognize, for example, due to manufacturing variations resulting from the deposition process, the front 112 and back 114 may exhibit surface waviness. Furthermore, the term "essentially" used here describes that components, parameters, and the like are generally the same (i.e.,h. “essentially constant”), but in practice may vary slightly due to possible manufacturing variations (e.g., below an acceptable threshold or percentage), as those skilled in the art recognize. For the purposes of this disclosure, the use of the term “or” in the claims means “and / or” unless it is expressly stated that it denotes only alternatives or that the alternatives are mutually exclusive.

[0027] According to one exemplary aspect, the piezoelectric layer can be a thin single-crystal layer of a piezoelectric material, such as lithium niobate, lithium tantalate, lanthanum gallium silicate, gallium nitride, or aluminum nitride. It should be noted that the term "single crystal" does not necessarily mean "completely uniform in its crystal structure" and may include impurities due to manufacturing variations, as long as the crystal structure is within acceptable tolerances. The piezoelectric layer is cut such that the orientation of the crystalline X, Y, and Z axes with respect to the front and back surfaces is known and consistent. In the examples described here, the piezoelectric layers are Z-cut, meaning that the Z-axis is perpendicular to the front and back surfaces.However, XBARs can be fabricated on piezoelectric layers with other crystallographic orientations, including twisted Z-cut, Y-cut and twisted YX-cut.

[0028] The Y-section family, such as 120Y and 128Y, is typically designated 120YX or 128YX, where the "section angle" is the angle between the y-axis and the normal to the layer. The "section angle" is equal to β+90°. For example, a layer with Euler angles [0°, 30°, 0°] is commonly referred to as a "Y-section rotated by 120°" or "120Y". Thus, the Euler angles for 120YX and 128YX are (0, 120-90,0) and (0, 128-90,0), respectively. A "Z-section" is typically designated as a ZY-section, meaning that the surface of the layer is perpendicular to the Z-axis, but the wave propagates along the Y-axis. The Euler angles for the ZY section are (0, 0, 90).

[0029] The back side 114 of the piezoelectric layer 110 can be at least partially supported by a surface of the substrate 120, with the exception of a section of the piezoelectric layer 110 that forms a membrane 115 lying over (e.g., spanning or extending over) a cavity 140 in one or more layers below the piezoelectric layer 110, such as one or more intermediate layers above or within the substrate. In other words, the back side 114 of the piezoelectric layer 110 can be coupled or connected to a surface of the substrate 120 either directly or indirectly via one or more intermediate layers (e.g., a dielectric layer, such as a silicon oxide layer). Furthermore, the phrase "supported by" or "attached," used interchangeably here, can mean: directly attached, indirectly attached, mechanically supported, structurally supported, or any combination thereof.The section of the piezoelectric layer that lies above the cavity (e.g., spans or extends over it) can be referred to here as a “membrane” 115 due to its physical similarity to the diaphragm of a microphone. As in . Fig. As shown in Figure 1A, the membrane 115 is connected to the rest of the piezoelectric layer 110 around the entire circumference 145 of the cavity 140. "Connected" in this context means "continuously connected without an intervening element." However, in an exemplary aspect, the membrane 115 can be configured such that at least 50% of the edge surface of the membrane 115 is coupled to the edge of the piezoelectric layer 110.

[0030] According to the exemplary aspect, the substrate 120 is configured to provide mechanical support to the piezoelectric layer 110. The substrate 120 can, for example, consist of silicon, sapphire, quartz, or another material or material combination. The back surface 114 of the piezoelectric layer 110 can be bonded to the substrate 120 using a wafer bonding process. Alternatively, the piezoelectric layer 110 can be grown on the substrate 120, supported by the substrate, or attached to it in some other way.

[0031] For the purposes of this disclosure, “cavity” has the usual meaning of “an empty space in a solid.” The cavity 140 may be a hole passing completely through the substrate 120 (as shown in section AA), or a hole located wholly or partially within a dielectric layer (as shown in Fig. 1B shown), or to form a recess in the substrate 120. The cavity 140 can be formed, for example, by selectively etching the substrate 120 before or after the piezoelectric layer 110 and the substrate 120 are applied directly or indirectly.

[0032] As shown, the conductor pattern of the XBAR 100 includes an interdigital converter (IDT) 130. The IDT 130 comprises a first plurality of parallel fingers, such as finger 136, extending from a first bus bar 132, and a second plurality of fingers extending from a second bus bar 134. The first and second plurality of parallel fingers are intertwined and may be "substantially" parallel to each other, for example, due to small variations such as those caused by manufacturing tolerances. At least one segment of the intertwined fingers overlaps over a distance AP, commonly referred to as the "aperture" of the IDT. The center-to-center distance L between the outermost fingers of the IDT 130 is the "length" of the IDT.

[0033] In the example from Fig. In 1A, the IDT 130 is located on the surface of the front side 112 (e.g., the first surface) of the piezoelectric layer 110. However, as explained below, in other configurations the IDT 130 can be located on the surface of the back side 114 of the piezoelectric layer 110 (e.g., the second surface), or on both surfaces of the front side and the back side 112, 114 of the piezoelectric layer 110.

[0034] The first and second busbars 132, 134 are configured as connection points of the XBAR 100, with the majority of entangled fingers extending from them. A radio frequency or microwave signal applied between the two busbars 132, 134 of the IDT 130 primarily excites an acoustic mode (i.e., a primary acoustic shear mode) within the piezoelectric layer 110. As will be explained in more detail later, the primarily excited acoustic shear mode is a volume shear mode or acoustic volume wave, wherein the acoustic energy of an acoustic volume shear wave in the piezoelectric layer 110 is excited by the IDT 130 and propagates along a direction that is substantially, predominantly, and / or primarily orthogonal to the surface of the piezoelectric layer 110, which is also primarily normal, or transverse, to the direction of the electric field generated by the IDT fingers.This means that when a high-frequency or microwave signal is applied between the two busbars 132, 134, the RF voltage applied to the respective sets of IDT fingers generates a time-varying electric field that is laterally excited with respect to a surface of the piezoelectric layer 110. In some cases, the primarily excited acoustic mode can thus be generally referred to as a laterally excited acoustic volume wave, since a displacement, as opposed to propagation, occurs primarily in the direction of the volume of the piezoelectric layer, as shown below with respect to . Fig. 4 explained in more detail.

[0035] For the purposes of this disclosure, a “primary acoustic mode” can generally be defined as an operating mode in which a vibrational displacement is primarily induced in the thickness-shear direction (e.g., the X-direction), such that the wave propagates substantially and / or primarily in the direction connecting the opposing front and back surfaces of the piezoelectric layer, that is, in the Z-direction. In other words, the X-direction component of the wave is considerably smaller than the Z-direction component. The use of the term “primary” in “primarily excited acoustic mode” does not necessarily refer to a lower-order or higher-order mode. Thus, the XBAR is considered a transversely excited film volume wave resonator.One physical limitation is that when the high-frequency or microwave signal is applied between the two busbars 132 and 134 of the IDT 130, heat is generated, which must be dissipated from the resonator to improve performance. Generally, heat can be dissipated by lateral conduction across the membrane (e.g., in the electrodes themselves) and by vertical conduction through a cavity into the substrate.

[0036] In any case, the IDT 130 is positioned on or at the piezoelectric layer 110 such that at least the fingers of the IDT extend onto or at the section of the piezoelectric layer 110 that lies above the cavity 140, for example, the membrane 115 described here. As in Fig. As shown in Figure 1A, the cavity 140 has a rectangular cross-section with a larger extent than the aperture AP and length L of the IDT 130. According to other exemplary aspects, the cavity of an XBAR can have a different cross-sectional shape, such as that of an equilateral or asymmetrical polygon. The cavity of an XBAR can have more or fewer than four sides, which can be straight or curved.

[0037] According to one exemplary aspect, the area of ​​the XBAR 100 is determined as the area of ​​the IDT 130. For example, the area of ​​the IDT 130 can be determined based on the measurement of the length L, multiplied by the width of the aperture AP, of the interlocked fingers of the IDT 130. In the disclosure, the area is consistently given in µm². 2 The surface area of ​​the XBAR 100 can therefore be adjusted based on design decisions, as described below, thereby adjusting the overall capacity of the XBAR 100.

[0038] For easier presentation, in Fig. 1A The geometric spacing and width of the IDT fingers are greatly exaggerated in relation to the length (dimension L) and aperture (dimension AP) of the XBAR. A typical XBAR in the IDT has more than ten parallel fingers. For example, according to example aspects, an XBAR in the IDT can have hundreds, possibly thousands, of parallel fingers. Likewise, the thickness of the fingers in the cross-sectional views is greatly exaggerated.

[0039] Fig. Figure 1B shows a schematic cross-sectional view of an alternative 100' XBAR configuration. Fig. 1B is the cavity 140 of the resonator 100' (which is generally called cavity 140 from Fig. 1A can correspond) completely within a dielectric layer 124 (for example silicon oxide or silicon dioxide, as in Fig. 1B), which are located between the substrate 120 (in Fig. 1B as Si) and the piezoelectric layer 110 is located (in Fig. 1B shown as LN). Although a single dielectric layer 124 with a cavity 140 formed therein (e.g. by etching) is shown, it is pointed out that the dielectric layer 124 may be formed from a plurality of separate dielectric layers formed on top of each other to provide a stack of materials.

[0040] Furthermore, in the example from Fig. 1B the cavity 140 is defined on all sides by the dielectric layer 124. In other embodiments, however, one or more sides of the cavity 140 can be defined by the substrate 120 and / or the piezoelectric layer 110. In the example from Fig. In 1B, the cavity 140 has a trapezoidal shape. However, as noted above, the shape of the cavity is not restricted and can be rectangular, oval, or other shapes.

[0041] Fig. Figure 2A shows a detailed schematic cross-sectional view (labeled section C) of the XBAR 100. Fig. 1A or Fig. 1B. The piezoelectric layer 110 is a single-crystal layer of piezoelectric material with a thickness ts. Ts can be, for example, 100 nanometers (nm) to 1500 nm. When used in filters for 5G NR and Wi-Fi™ bands from 3.4 GHz to 7 GHz, the thickness ts can be, for example, 150 nm to 500 nm. The thickness ts can, in one exemplary aspect, be measured in a direction that is substantially perpendicular or orthogonal to a surface of the piezoelectric layer.

[0042] In this aspect, a front-side dielectric layer 212 (e.g., a first dielectric coating or a first dielectric material) can be formed on the front side 112 of the piezoelectric layer 110. The "front side" of the XBAR is, by definition, the surface facing away from the substrate. The front-side dielectric layer 212 has a thickness tfd. As in Fig. As shown in Figure 2A, the front-facing dielectric layer 212 covers the IDT fingers 238a, 238b, which may correspond to the fingers 136 as described above with reference to Fig. 1A described. Although in Fig. Since 2A is not shown, the front-side dielectric layer 212 may also be deposited only between the IDT fingers 238a, 238b. In this case, an additional thin dielectric layer (not shown) may be deposited over the IDT fingers to seal and passivate the fingers. Although in Fig. Since 2A is also not shown, the front-side dielectric layer 212 may, for example, only be deposited on selected IDT fingers 238a.

[0043] A backside dielectric layer 214 (e.g., a second dielectric coating or a second dielectric material) can also be formed on the back side 114 of the piezoelectric layer 110. For the purposes of this disclosure, the term "backside" generally means on one side opposite the conductor pattern of the IDT structure and / or opposite the frontside dielectric layer 212. Furthermore, the backside dielectric layer 214 has a thickness tbd. The frontside and backside dielectric layers 212, 214 can consist of a non-piezoelectric dielectric material, such as silicon oxide, silicon dioxide, or silicon nitride. Tfd and tbd can, for example, be from 0 to 500 nm. Tfd and tbd can be less than the thickness ts of the piezoelectric layer. Tfd and tbd are not necessarily the same, and the front and back dielectric layers 212, 214 are not necessarily made of the same material.In exemplary aspects, the front dielectric layer, the back dielectric layer 212, 214 or both can be formed from several layers of two or more materials according to various exemplary aspects.

[0044] The IDT fingers 238a, 238b may comprise aluminum, essentially (i.e., predominantly) aluminum alloys, copper, essentially (i.e., predominantly) copper alloys, beryllium, gold, or other conductive material. Thin layers (relative to the overall thickness of the conductors) of other metals, such as chromium or titanium, may be formed under and / or over the fingers to improve adhesion between the fingers and the piezoelectric layer 110 and / or to passivate or encapsulate the fingers. The busbars (132, 134 in Fig. 1A) The IDT fingers may be made of the same or different materials as the fingers. The cross-sectional shape of the IDT fingers may be trapezoidal (finger 238a) or rectangular (finger 238b) or other shapes in various exemplary aspects. It is generally noted that the terms "have," "have," "comprise," and "contain" (and their variants), as used herein, are open conjunctions and, when used in a claim, permit the addition of other elements. Furthermore, the use of the word "a" or "an" when used in conjunction with the expression "have" in the claims or the specification means one or more than one, unless otherwise indicated by the context.

[0045] The dimension p (i.e., the “distance”) can be considered the center-to-center spacing between adjacent IDT fingers, such as between IDT fingers 238a and 238b in Fig. 2A - 2D. The centers of the center-to-center distance can be measured at the center of the width "w" of a finger, as in Fig. Figure 2A shows that in some cases, the center-to-center distance can change if the width of a given finger changes along its length, 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 distance can be measured as the average center-to-center distance, maximum center-to-center distance, minimum center-to-center distance, or any variation thereof. Adjacent fingers may extend from a different busbar, and the center-to-center distance 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 extending from a second busbar.The center-to-center spacing can be constant along the length of the IDT, in which case dimension p can be referred to as the IDT spacing and / or the XBAR spacing. In an alternative exemplary aspect, however, the center-to-center spacing varies along the length of the IDT, in which case the IDT spacing can be the average value of dimension p over the length of the IDT. The center-to-center spacing from one finger to an adjacent finger can vary continuously relative to other adjacent fingers, in discrete segments of several adjacent pairs, or any combination thereof. Each IDT finger, such as IDT fingers 238a and 238b in [reference missing], exhibits this. Fig. 2A to 2D, has a width w, measured normal to the longitudinal direction of each finger. The width w can also be referred to here as the "marker". 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 explained below, the width of each IDT finger varies along the length of the IDT 130, in which case the dimension w can be the average value of the widths of the IDT fingers over the length of the IDT. It is noted that the spacing p and the width w of the IDT fingers are measured in a direction substantially parallel to the length L of the IDT, as in Fig. 1A defined.

[0046] In general, the IDT of an XBAR differs substantially from those used in surface acoustic wave (SAW) resonators, primarily in that the IDTs of an XBAR excite a primary acoustic shear mode (also referred to as primary shear mode, primary shear thickness mode, or the like), as shown below with reference to Fig. Section 4 describes in more detail how SAW resonators excite a surface wave during operation. Furthermore, in a SAW resonator, the spacing of the IDT is half the sound wavelength at the resonance frequency. Additionally, the marker-to-spacing ratio of a SAW resonator IDT is typically close to 0.5 (i.e., the marker or finger width is approximately one-quarter of the sound wavelength at resonance). In an XBAR, the spacing p of the IDT is typically 2 to 20 times the width w of the fingers. Furthermore, the spacing p of the IDT is typically 2 to 20 times the thickness ts of the piezoelectric layer 110. Moreover, the width of the IDT fingers in an XBAR is not limited to one-quarter of the sound wavelength at resonance. For example, the width of the XBAR IDT fingers can be 500 nm or more, allowing the IDT to be fabricated using optical lithography.The thickness tm of the IDT fingers can range from 100 nm to approximately the width w, since the lithography process typically cannot support a configuration where the thickness is greater than the width. The thickness of the busbars (132, 134 in . Fig. 1A) The thickness of the IDT can be equal to, less than, or greater than the thickness tm of the IDT fingers, or any combination thereof. It should be noted that the XBAR devices described herein are not limited to the dimensional ranges described herein.

[0047] Unlike a SAW filter, the resonant frequency of an XBAR also depends on the overall thickness of its diaphragm (i.e., in the vertical or thickness direction), including the piezoelectric layer 110 and the front and back dielectric layers 212, 214 arranged on it. As an example, the thickness of one or both dielectric layers (i.e., on the opposite surfaces of the piezoelectric layer) can be varied to change the resonant frequencies of different XBARs in a filter. For example, shunt resonators in a conductor filter circuit can have thicker dielectric layers to reduce the resonant frequencies of the shunt resonators relative to series resonators with thinner dielectric layers and thus a thinner overall thickness.

[0048] Again with reference to Fig. 2A The thickness tfd of the front-facing dielectric layer 212 over the IDT fingers 238a, 238b can be greater than or equal to a minimum thickness required to cover and passivate the IDT fingers and other conductors on the front face 112 to the other piezoelectric layer 110. According to one example, the minimum thickness can be, for instance, 10 nm to 50 nm, depending on the material of the front-facing dielectric layer and the deposition method. The thickness of the back-facing dielectric layer 214 can be configured to a specific thickness to match the resonant frequency of the resonator, as described in more detail below.

[0049] Although Fig. Figure 2A reveals a configuration in which the IDT fingers 238a and 238b are located on the front face 112 of the piezoelectric layer 110; however, alternative configurations may be provided. For example, Figure 2A shows that... Fig. 2B shows an alternative configuration (designated as cutout C') in which the IDT fingers 238a, 238b are located on the back 114 of the piezoelectric layer 110 (i.e., facing the cavity) and are covered with a back-side dielectric layer 214. A front-side dielectric layer 212 can cover the front 112 of the piezoelectric layer 110. In exemplary aspects, a dielectric layer placed on the diaphragm of each resonator can be cut or etched to match the resonant frequency. However, if the dielectric layer is located on the side of the diaphragm facing the cavity, there may be a change in interfering modes (e.g., generated by the coating on the fingers). Furthermore, the marking changes with the passivation layer applied on top of the IDTs, which can also cause interference.By arranging the IDT fingers 238a, 238b on the back side 114 of the piezoelectric layer 110, as in . Fig. As shown in Figure 2B, the need for a solution for both the frequency change and the effect it has on disturbances can therefore be eliminated, compared with IDT fingers 238a and 238b located on the front face 112 of the piezoelectric layer 110.

[0050] Fig. Figure 2C shows an alternative configuration (designated as section C'') in which the IDT fingers 238a, 238b are located on the front face 112 of the piezoelectric layer 110 and are covered with a front-facing dielectric layer 212. Additionally, the IDT fingers 238c, 238d are located on the back face 114 of the piezoelectric layer 110 and are also covered with a back-facing dielectric layer 214. As previously described, the front-facing and back-facing dielectric layers 212, 214 do not necessarily have the same thickness or consist of the same material.

[0051] Fig. Figure 2D shows another alternative configuration (designated as section C''') in which the IDT fingers 238a, 238b are located on the front face 112 of the piezoelectric layer 110 and are covered with a front-facing dielectric layer 212. The surface of the front-facing dielectric layer is planarized. The front-facing dielectric layer can be planarized, for example, by polishing or another method. A thin layer of dielectric material with a thickness tp can cover the IDT fingers 238a, 238b to seal and passivate the fingers. The dimension tp can be, for example, 10 nm to 50 nm.

[0052] The above with reference to Fig. The XBAR configurations described in sections 2A to 2D each comprise a membrane spanning a cavity. Alternatively, the acoustic volume resonator can be rigidly mounted, with the membrane attached to or above a Bragg mirror using IDT fingers, which in turn can be mounted on a substrate.

[0053] In particular, it shows Fig. 2E is a detailed schematic cross-sectional view of a fixed XBAR (SM-XBAR). It is noted that Fig. 2E generally has a similar cross-section to the one from Fig. Figure 1A reveals the configuration as fixed. In this aspect, the SM-XBAR comprises a piezoelectric layer 110 and an IDT (of which only two fingers 236 are visible), with a dielectric layer 212 arranged on the piezoelectric layer 110 and the IDT fingers 236. The piezoelectric layer 110 has parallel front and back surfaces similar to the configurations described above. 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 spacing is dimension p.

[0054] In contrast to the in Fig. The XBAR devices shown in 1A are not the IDT of an SM-XBAR in Fig. 2E is formed on a membrane spanning a cavity in the substrate. Instead, an acoustic Bragg reflector 240 (also called a Bragg mirror) is sandwiched between a surface 222 of the substrate 220 and the rear surface of the piezoelectric layer 110. The term "sandwiched" means that the acoustic Bragg reflector 240 is both positioned between and attached to a surface 222 of the substrate 220 and the rear surface of the piezoelectric layer 110. In some circumstances, layers of additional materials (e.g., one or more dielectric layers) may be positioned 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 additional material layers may be present, for example, to enable the bonding of the piezoelectric layer 110, the acoustic Bragg reflector 240 and the substrate 220.

[0055] The acoustic Bragg reflector 240 can be an acoustic mirror configured to reflect at least part of the primary acoustic mode excited in the piezoelectric element and comprises several dielectric layers alternating between materials with high and low acoustic impedance. The acoustic impedance of a material is the product of its shear wave velocity and density. "High" and "low" are relative terms. For each layer, the adjacent layers serve as the standard for comparison. Each "high" acoustic impedance layer has a higher acoustic impedance than the two adjacent layers with low acoustic impedance. Conversely, each "low" acoustic impedance layer has a lower acoustic impedance than the two adjacent layers with high acoustic impedance.As explained above, the primary acoustic mode in the piezoelectric layer of an XBAR is a shear volume wave. In an exemplary aspect, each layer of the acoustic Bragg reflector 240 has a thickness equal to or approximately equal to one-quarter of the wavelength in the shear volume wave layer with the same polarization as the primary acoustic mode at or near a resonant frequency of the SM-XBAR. Dielectric materials with comparatively low acoustic impedance include silicon dioxide, carbon-containing silicon dioxide, aluminum, and certain plastics such as cross-linked polyphenylene polymers.Materials with comparatively high acoustic impedance include hafnium oxide, silicon nitride, aluminum nitride, silicon carbide, tungsten carbide, tantalum carbide, rhenium oxide, chromium carbide silicide, niobium carbide, zinc carbide, zinc nitride, lanthanum boride, vanadium carbide, yttrium oxide, magnesium oxide, boron carbide, strontium fluoride, barium fluoride, tantalum oxide, tungsten oxide, hafnium nitride, tungsten nitride, platinum, tungsten, copper, gold, and silver. Not all layers with high acoustic impedance of the acoustic Bragg reflector 240 are necessarily made of the same material, nor are all layers with low acoustic impedance necessarily made of the same material. In the example from... Fig. The acoustic Bragg reflector 240 has a total of six layers in the 2E version, however, an acoustic Bragg reflector can have more or fewer than six layers in alternative configurations.

[0056] The IDT fingers, such as IDT fingers 236, 238a, and 238b, can be arranged on a surface of the front face 112 of the piezoelectric layer 110. Alternatively, the IDT fingers, such as IDT fingers 236, 238a, and 238b, can be arranged in grooves formed in the surface of the front face 112. The grooves can extend partially through the piezoelectric layer. Alternatively, the grooves can extend completely through the piezoelectric layer.

[0057] Fig. 3A and Fig. Figure 3B shows two exemplary cross-sectional views along the in Fig. 1A defined cutting plane AA of the XBAR 100. In Fig. 3A is a piezoelectric layer 310, corresponding to the piezoelectric layer 110, directly attached to a substrate 320, which corresponds to the substrate 120. Fig. 1A can correspond. In addition, a cavity 340, which does not go completely through the substrate 320, is formed in the substrate under the section (i.e. the membrane 315) of the piezoelectric layer 310, which contains the IDT of an XBAR.

[0058] In one exemplary aspect, cavity 340 can be compared to cavity 140. Fig. 1A and / or 1B. In one exemplary aspect, the cavity 340 can be formed, for example, by etching the substrate 320 before applying the piezoelectric layer 310. Alternatively, the cavity 340 can be formed by etching the substrate 320 with a selective etching agent that reaches the substrate through one or more openings provided in the piezoelectric layer 310.

[0059] Fig. 3B presents an alternative aspect in which the substrate 320 comprises a base 322 and an intermediate layer 324 arranged between the piezoelectric layer 310 and the base 322. The base 322 can, for example, be made of silicon (e.g., a silicon support substrate), and the intermediate layer 324 can be made of silicon dioxide, silicon nitride, or another material, e.g., a dielectric intermediate layer. That is, in this aspect, the base 322 and the intermediate layer 324 are considered together as the substrate 320. As further shown, the cavity 340 in the intermediate layer 324 is formed beneath the section (i.e., the membrane 315) of the piezoelectric layer 310 that contains the IDT fingers of an XBAR. The cavity 340 can be formed, for example, by etching the intermediate layer 324 prior to the application of the piezoelectric layer 310. Alternatively, the cavity 340 can be formed by etching the intermediate layer 324.In other embodiments, the cavity 340 in the intermediate layer 324 can be formed by means other than etching the intermediate layer 324 to define the cavity 340. In some cases, the etching can be carried out with a selective etching agent that reaches the substrate through one or more openings (not shown) provided in the piezoelectric layer 310.

[0060] In this case, the membrane 315, which for example is the membrane 115, can be used. Fig. 1A can correspond, in an exemplary aspect, to be connected with the rest of the piezoelectric layer 310 around a large portion of the circumference of the cavity 340. For example, the membrane 315 can be connected with the rest of the piezoelectric layer 310 around at least 50% of the circumference of the cavity 340. As in Fig. As shown in Figure 3B, the cavity 340 extends completely through the intermediate layer 324. This means that the membrane 315 can have an outer edge facing the piezoelectric layer 310, with at least 50% of the edge surface of the membrane 315 being coupled to the edge of the piezoelectric layer 310 facing the membrane 315. This configuration ensures increased mechanical stability of the resonator.

[0061] In other configurations, the cavity 340 can extend partially into, but not completely through, the intermediate layer 324 (i.e., the intermediate layer 324 can extend over the underside of the cavity on top of the base 322) or it can extend through the intermediate layer 324 and (partially or completely) into the base 322. It should be noted that, as described above, the interlocking fingers of the IDT can be positioned on one or both surfaces of the membrane 315 according to various exemplary aspects. Fig. 3A and Fig. They may be arranged in 3B.

[0062] Fig. Figure 4 is a graphical representation of the primary excited acoustic mode of interest in an XBAR. Fig. Figure 4 shows a small section of an XBAR 400 comprising a piezoelectric layer 410 and three interlocked IDT fingers 430. In general, the example configuration of the XBAR 400 can correspond to one of the configurations described above and in [reference to be added]. Fig. Figures 2A to 2D show this. It is indicated, for example, that the piezoelectric layer 410 can correspond to the piezoelectric layer 110 and that the IDT fingers 430 can be implemented according to one of the configurations of fingers 238a and 238b.

[0063] During operation, an RF voltage is applied to the interlocked fingers 430. This voltage generates a time-varying electric field between the fingers. The direction of the electric field is lateral (i.e., laterally excited), or primarily parallel to the surface of the piezoelectric layer 410, as indicated by the arrows labeled "electric field." Due to the high dielectric constant of the piezoelectric layer 410, the electric field is highly concentrated in the piezoelectric layer relative to the air. The lateral electric field introduces shear deformation into the piezoelectric layer 410 and thus strongly excites an acoustic shear mode in the piezoelectric layer 410. In this context, "shear deformation" is defined as deformation in which parallel planes in a material remain parallel and maintain a constant distance while shifting relative to each other.In other words, the parallel planes of the material are laterally displaced relative to each other. An "acoustic shear mode" is defined as an acoustic vibration mode in a medium that leads to shear deformation of the medium. The shear deformations in the XBAR 400 are represented by curves 460, where the adjacent small arrows schematically indicate the direction and magnitude of the atomic motion. It is noted that the degree of atomic motion, as well as the thickness of the piezoelectric layer 410, are shown in the figure. Fig. 4 are exaggerated for easier visualization. While the atomic motions are predominantly lateral (i.e., horizontal, as in Fig. 4 shown), the direction of the sound energy flow of the primarily excited acoustic shear mode is essentially and / or primarily orthogonal to the surface of the piezoelectric layer, as indicated by arrow 465.

[0064] An acoustic bulk resonator based on acoustic shear wave resonances can achieve better performance than current devices using film bulk acoustic resonators (FBARs) or solidly-mounted resonator bulk acoustic waves (SMR BAWs) according to the prior art, where the electric field is applied in the thickness direction. In such devices, the acoustic mode is compressive, with atomic motion and the direction of sound energy flow in the thickness direction. Furthermore, the piezoelectric coupling for shear wave XBAR resonances can be high (>20%) compared to other acoustic resonators. This high piezoelectric coupling thus enables the design and implementation of microwave and millimeter-wave filters with considerable bandwidth.

[0065] Fig. 5A is a schematic circuit diagram and layout for a 500 series bandpass filter for high frequencies with a plurality of acoustic volume wave resonators (e.g., XBARs), such as the general XBAR 100 configuration described above (e.g., the acoustic volume wave resonators). The 500 series filter has a conventional ladder filter architecture, which may include a split ladder filter architecture where the filter is divided across multiple chips, each containing a plurality of acoustic volume resonators, including four resonators 510A, 510B, 510C, and 510D, and three shunt resonators 520A, 520B, and 520C. The series resonators 510A, 510B, 510C, and 510D are connected in series between a first terminal and a second terminal (hence the term "series resonator"). Fig. 5A refers to the first and second terminals, labeled "input" and "output," respectively. However, the 500 filter is bidirectional, and either terminal can function as an input or output. At least two shunt resonators, such as the 520A and 520B shunt resonators, are connected to a ground terminal via nodes between the series resonators. A filter may also include additional reactive components, such as inductors, in Fig. 5A not shown. All shunt and series resonators are in the exemplary aspect of XBARs (e.g., one of the XBAR configurations 100 and / or 100' as explained above). The inclusion of three series resonators and two shunt resonators is an example. A filter may have more or fewer than five resonators in total, more or fewer than three series resonators, and more or fewer than two shunt resonators. Typically, in division-ladder and non-division-ladder filter architectures, all series resonators are connected in series between an input and an output of the filter, and all shunt resonators are typically connected between ground and the input, the output, or a node between two series resonators.

[0066] In the example filter 500, the series resonators 510A, 510B, 510C, and 510D, as well as the shunt resonators 520A, 520B, and 520C of the filter 500, can be formed on at least one piezoelectric layer 530 made of piezoelectric material, and in some cases, a single layer, which is bonded (not visible) to a silicon substrate. Alternatively, however, the individual resonators can each be formed on a corresponding separate piezoelectric layer for each resonator, with all resonators located on the same chip. In some cases, however, different resonators of a filter can be bonded to a separate substrate, for example.This can result in a division-ladder architecture comprising one or more separate chips, each containing separate piezoelectric layers and IDTs of one or more acoustic volume resonators, configured to form the division-ladder filter as a whole. Furthermore, each resonator includes a respective IDT (not shown), with at least the fingers of the IDT positioned above a cavity or acoustic mirror in the substrate. In this and similar contexts, the term "respective" means "each related to the other," that is, with a one-to-one correspondence. Fig. In 5A, the cavities are schematically represented as dashed rectangles (such as rectangle 535). In this example, each IDT is arranged over a specific cavity. In other filters, the IDTs of two or more resonators may be arranged over a single cavity.

[0067] Each of the resonators 510A, 510B, 510C, 5100, 520A, 520B, and 520C in the 500 filter has a resonance at which the resonator's admittance (interchangeably also referred to as the Y-parameter) is very high, and an antiresonance at which the resonator's admittance is very low. Resonance and antiresonance occur at a resonant frequency and an antiresonance frequency, respectively, which may be the same or different for the various resonators in the 500 filter. In simplified terms, each resonator can be considered short-circuited at its resonant frequency and open-circuited at its antiresonance frequency. The input-output transfer function is nearly zero at the resonant frequencies of the shunt resonators and at the antiresonance frequencies of the series resonators.In a typical filter, the resonant frequencies of the shunt resonators are below the lower edge of the filter's passband, and the antiresonant frequencies of the series resonators are above the upper edge of the passband.

[0068] The frequency range between the resonant and anti-resonant frequencies of a resonator corresponds to the coupling of the resonator. Depending on the design parameters of the Filter 500, each of the resonators 510A, 510B, 510C, 5100, 520A, 520B, and 520C can have a specific coupling parameter to which the respective resonator is tuned in order to achieve the required frequency response of the Filter 500.

[0069] According to one exemplary aspect, each of the series resonators 510A, 510B, 510C and 510D as well as the shunt resonators 520A, 520B and 520C can be configured as an XBAR, as above with reference to Fig. 1A - 2D described, in which a diaphragm with IDT fingers spans a cavity. Alternatively, each of the series resonators 510A, 510B, 510C, 510D and the shunt resonators 520A, 520B and 520C can have an XBAR configuration in which the series resonators 510A, 510B, 510C, 510D and / or the shunt resonators 520A, 520B, and 520C can be rigidly mounted on or above a Bragg mirror (e.g. as in Fig. (2E shown), which in turn can be mounted on a substrate. As described below, further exemplary aspects include a resonator coupled in series with a dielectric capacitor to shift the resonance (e.g., upwards), while simultaneously reducing the coupling coefficient and enabling the construction of filters with a narrower band than existing configurations. Accordingly, the Filter 500 can include one or more capacitors, each electrically coupled in series with a plurality of IDTs, as will be apparent to those skilled in the art.

[0070] Fig. Figure 5B is a schematic diagram of a high-frequency module comprising an acoustic wave filter device according to an exemplary aspect. In particular, it represents Fig. Figure 5B represents a high-frequency module 540 comprising one or more acoustic wave filters 544, according to an exemplary aspect. The illustrated high-frequency module 540 also comprises a high-frequency (HF) circuit arrangement (or high-frequency, “HF”, circuit) 543. In an exemplary aspect, the acoustic wave filters 544 can be one or more of the filters 500 with XBARs (e.g., the acoustic volume resonators described herein), as above with reference to Fig. 5A described, include.

[0071] The in Fig. The acoustic wave filter 544 shown in Figure 5B includes connection points 545A and 545B (e.g., first and second connection points). Connection points 545A and 545B can, for example, serve as the input and output contacts for the acoustic wave filter 544. Although two connection points are shown, any suitable number of connection points can be implemented for a given application. The acoustic wave filter 544 and the RF circuit arrangement 543 are located in Fig. 5B on a housing substrate 546 (e.g., a common substrate). The housing substrate 546 can be a laminate substrate. The connection points 545A and 545B can be electrically connected to the contacts 547A and 547B, respectively, via electrical connection elements 548A and 548B on the housing substrate 546. The electrical connection elements 548A and 548B can be, for example, solder joints or wire bonds. In one exemplary aspect, the acoustic wave filter 544 and the RF circuit arrangement 543 can be housed together in a common enclosure, with or without the use of the housing substrate 546.

[0072] The RF circuit arrangement 543 can comprise any suitable RF circuit arrangement. For example, the RF circuit arrangement can include: one or more RF amplifiers (e.g., one or more power amplifiers and / or one or more low-noise amplifiers), one or more RF 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. The RF circuit arrangement 543 can be electrically connected to the one or more acoustic wave filters 544. The RF module 540 can comprise one or more housing structures to provide, for example, protection and / or to facilitate handling of the RF module 540. Such a housing structure can include a molded structure formed over the housing substrate 546.The forming structure can encapsulate some or all of the components of the 540 high-frequency module.

[0073] As described above, existing electrical filters and resonators used in electrical signal processing are designed to allow specific signal frequencies (e.g., the passband) while blocking or attenuating unwanted frequencies (e.g., the stopband). However, existing methodologies often require different fabrication techniques and materials to provide passband resonators with narrower surface acoustic waves (SAW) and / or volumetric acoustic waves (BAW), leading to increased inventory requirements and additional qualification steps. Furthermore, the fluctuating electrical properties of these materials can compromise performance.

[0074] In light of these limitations, the exemplary aspects provide for the implementation of a dielectric capacitor coupled in series with an inductor damper (IDT) of an acoustic resonator, such as an XBAR, SAW, and / or BAW type resonator. This allows, for example, an upward shift of the resonator's resonance frequency and, in turn, permits the construction of narrower-band filters without the complications of sourcing and qualifying new materials. Furthermore, by utilizing existing materials and manufacturing processes, exemplary aspects of this disclosure provide a streamlined approach that not only improves filter design flexibility but also maintains or enhances performance consistency across applications of such filter devices.

[0075] Fig. Figure 6A is a schematic view of a section of a filter device 600 comprising an acoustic resonator (e.g., an XBAR) with a series-coupled dielectric capacitor 640, according to an exemplary aspect. In general, the filter device 600 comprises an acoustic resonator with one or a pair of dielectric capacitors on one or both sides of the IDT of the acoustic resonator. The Fig. The filter device 600 shown in Figures 6A-6C represents the integration of a series capacitor on one side of the IDT. The series capacitor(s) are electrically coupled in series with the acoustic resonator (e.g., an acoustic volume resonator) and, in one exemplary aspect, can be integrated as at least one section of a busbar (e.g., a first busbar) or as a pair of busbars (e.g., first and second busbars) of the IDT of the acoustic resonator.

[0076] As described in detail below, the series capacitor generally consists of a pair of metal busbar layers and a dielectric layer placed between them. Alternatively, the series capacitor(s) may be formed separately from the one or more busbars or from a wire extending from the one or more busbars. In either case, the acoustic resonator may be an XBAR (e.g., a membrane-based or fixed-mount XBAR, as described here). However, it should be noted that the configuration of the dielectric capacitor described here is implementable for other types of SAW or BAW resonators, as experts are aware.

[0077] Furthermore, it is noted that while the series capacitor described here can generally be considered a MIM (i.e., metal-insulator-metal) capacitor in the exemplary aspects, the series capacitor could be other types in other exemplary aspects, such as one or a pair of interdigitated capacitors (IDCs). As described here, the capacitor can be coupled in series with the IDT of the acoustic resonator, or a pair of capacitors can each be coupled in series with a respective busbar of the IDT, as described here. In other words, the IDT is located between the respective capacitors (which can be either a MIM capacitor or an IDC). An IDC is generally configured as a multi-fingered periodic structure that utilizes the capacitance occurring across a narrow gap between conducting fingers.However, there are compromises regarding which type of capacitor can be used, depending on the specific aspects. In particular, the integrated capacitor (IDC) can be physically large, depending on the required capacitance, and would therefore likely occupy more physical space in the layout. However, an IDC can exhibit better tolerance in terms of absolute capacitance (compared to a multi-impact capacitor structure) because the M1 power bandwidths are very controllable. As also described here, the capacitor can be partially or fully integrated with the acoustic resonator bus, depending on the specific aspect.

[0078] As shown in the partial view in Fig. Figure 6A shows in each case a section of a metal pattern (e.g., designated as metal 1 or M1) that forms a metal layer 632A, wherein the metal layer 632A can be a busbar corresponding to one of the pair of busbars 132 and 134, as shown, for example, in Fig. Figure 1A shows that, in this exemplary aspect, the metal layer M1 is configured as a busbar 632A (or section of the busbar), corresponding to a section of busbar 132. It is also noted that the busbars of the IDT, such as busbar 632A, can more generally be viewed as wire conduits (e.g., one or more wires) that connect the interlocking fingers of each resonator to the respective electrical potentials applied across the resonator surface, and / or connect different resonators of a filter to each other and / or to ground. Therefore, in this aspect, the metal layer M1 can also be configured as wiring or as a wire conduit of the acoustic resonator.

[0079] It is further noted that while the IDT is generally described as having interlocked fingers, as in Fig. Figure 1A shows, and as explained above, the example configuration can, however, have alternative IDT configurations. For example, in alternative aspects, the IDT electrodes can be arranged with positive and negative potentials on each side of the piezoelectric layer, similar to the one shown above. Fig. The configuration described in section 2C is also relevant. Furthermore, electrodes with positive and negative potentials can be arranged on one side of the piezoelectric layer, while a floating electrode can be arranged on the other side. Therefore, there is no restriction on the respective IDT configuration of the exemplary aspects in this regard.

[0080] In any case, a second metal pattern 642A (e.g., designated as metal 2 or M2) can be arranged on a surface of the busbar 632A during the formation of the acoustic resonator device. Accordingly, the metal layer M1 of the dielectric capacitor 640 can either be, in an exemplary aspect, part of the busbar 632A or, alternatively, be a wire conductor or other metal layer extending from the busbar of the acoustic resonator. In the Fig. In the configuration shown in Figure 6A, the dielectric capacitor 640 is integrated as part of the busbar, which comprises the metal layer 632A and metal layer 632B with an intermediate dielectric layer 644. In other words, the metal layer M1 is formed from the metal layer 632A of the acoustic resonator busbar, but there is no restriction on this.

[0081] In both cases, a dielectric capacitor 640 (also referred to in this disclosure as a series capacitor or simply a capacitor) is electrically coupled in series with the IDT of the acoustic resonator. Generally, the dielectric capacitor 640 is a capacitor electrically coupled in series with the acoustic resonator and comprises the dielectric layer 644 and a pair of metal layers on opposite surfaces of the dielectric layer 644, the metal layers being able to form the anode and cathode of the capacitor, which is integrated as part of the busbar. In one exemplary aspect, the dielectric capacitor 640 is formed by a dielectric layer 644 arranged on the metal pattern M1, thereby forming the section of the busbar 632A.A further metal layer 632B is then formed on the opposite surface of the dielectric layer 644, so that the dielectric layer 644 is sandwiched between them. That is, the metal layers 632A and 632B are arranged on opposite sides of the dielectric layer 644. As a result, the metal layer 632A and the metal layer 632B form the first and second electrodes of the dielectric layer 644 (e.g., a cathode and an anode, also referred to as the upper and lower electrodes). As further described, one or more additional metal layers 642B can be arranged on the metal layer 632B to adjust the thickness of the busbar. The one or more additional metal layers 642B are offset from the position where the metal layer 632B is arranged on the dielectric layer 644.Furthermore, the amount of series capacitance can be adjusted by changing several parameters, such as the busbar width, the overlap length, the thickness of the dielectric layer 644 and the area and thickness of the metal layers.

[0082] Furthermore, it is noted that, according to one exemplary aspect, the dielectric capacitor 640 does not overlap with the perimeter (or edges) of the cavity of the acoustic resonator. That is, if a dielectric capacitor 640 is implemented in a cavity-based acoustic resonator, such as the one described above and in Fig. 1A, Fig. 1B, Fig. 3A and Fig. As shown in Figure 3B, the dielectric capacitor 640 does not overlap with the cavity 140 / 340 in the top view of the piezoelectric layer 110 / 310, i.e., in the thickness direction of the acoustic resonator. Instead, the dielectric capacitor 640 is located outside the cavity in the top view and is formed, for example, from part or all of the busbar 132 or 134.

[0083] In yet another aspect, the dielectric capacitor 640 can be located outside the active area of ​​the acoustic resonator (i.e., not overlapping it in plan view), which can be considered the aperture of the IDT and the respective gaps between the ends of the interlocking fingers and opposing busbars. In some cases, the active area can be slightly larger than the aperture plus the respective gaps between the ends of the interlocking fingers and opposing busbars, in order to encompass an area equal to the aperture plus twice the distance between at least one of the gaps between the ends of the interlocking fingers and opposing busbars. In another embodiment, the dielectric capacitor 640 can be located as close to the active area as possible, provided it does not extend beyond the edge of any cavity in the resonator.This configuration can be implemented for cavity-based acoustic resonators, such as the one described above and in . Fig. 1A, Fig. 1B, Fig. 3A and Fig. 3B shown, as well as for permanently mounted acoustic resonators, such as the one in Fig. 2E shown and described above. In such a case, the dielectric capacitor 640 is again formed by a part of the or opposite busbar, or the entire respective busbar.

[0084] Fig. 6B is a top view of the in Fig. Section 6A of the filter device shown from above. As shown, the filter device 600 comprises an IDT 630 of an acoustic resonator (e.g., an XBAR) coupled in series with the dielectric capacitor 640 shown on one side of the IDT 630 of the acoustic resonator. As further shown, a wire conductor or other metal layer may be provided, directly coupled and extending from an edge of one of the pair of busbars 132 and 134, as shown in Fig. Figure 1A shows that, in an alternative aspect, the dielectric capacitor 640 can be configured such that the wire serves as its electrode. It is also noted that the IDT 630 is related to the IDT 130. Fig. can correspond to 1A, wherein the dielectric capacitor 640 is electrically coupled in series by one of the busbars of the IDT 630 with metal pattern formation (e.g. corresponding to the IDT 130).

[0085] The busbar length is shown and can be adjusted according to the required configuration of the filter device 600. It should be noted that the busbar length can be the same length “L” as that of the [unclear text]. Fig. 1A shown and described above IDT. Alternatively, the busbar length can be longer than the length of the IDT, for example, the one shown in Fig. The IDT 630 shown in Figure 6B. As also described, a wire line can be coupled to the busbar, as described above, and can be a separate component, a section or all of which can also be configured as one of the electrode layers of the dielectric capacitor described here. In one exemplary aspect, the one or more busbars can differ from the wire line in that the busbar(s) has at least one dimension that differs from the wire line, where the respective dimension (e.g., the busbar length) is defined as follows: Fig. 6B) is substantially similar throughout the entire busbar. In other words, the busbar may have a shape where at least one dimension is substantially similar to that of the wire conductor (e.g., within manufacturing tolerances), but otherwise differs from a dimension of a shape of the wire conductor. For example, in the Fig. In Figure 6B, a section of the wire line is shown that projects in a direction perpendicular to the length of the busbar in the plan view. According to one exemplary aspect, one or more of the dielectric capacitors 640 are arranged between or substantially between the IDTs 630 of adjacent resonators (e.g., approximately or substantially at the center with ± 10% from the center) (it is noted that in Fig. 6B a single resonator 630 is shown). In this aspect, potential manufacturing defects during the manufacture of the conductor filter, which incorporates a plurality of acoustic resonators as described here (e.g., as in Fig. 5A shown) comprising one or more dielectric capacitors 640.

[0086] Fig. 6C is another schematic view of the in Fig. Section 6A of the filter device shown, according to an exemplary aspect. The components in Fig. 6C generally correspond to those mentioned above with reference to Fig. Figure 6A describes the dielectric capacitor 640 as follows: the overlap width of the two opposing electrodes (i.e., the metal layers 632A and 632B) and the thickness 644A of the dielectric layer 644 are shown. As noted above, the capacitance of the dielectric capacitor 640 can be adjusted by modifying parameters such as the overlap width and the thickness of the dielectric 644A. Fig. 6C also represents the overlap between the busbar 632A and the dielectric layer 644, which can consist of silicon oxide or silicon dioxide, for example. Alternatively, in an exemplary aspect, a piezoelectric layer could be used as the dielectric layer 644. In both cases, and as described above, the metal layer M1 (e.g., 632A and 632B) and the metal layer M2 (e.g., 642A and 642B) can also be configured to influence the overall capacitance by changing the specified parameters.

[0087] Thus, according to an exemplary aspect that is in Fig. Figures 6A to 6C show a filter device 600 which is an acoustic volume resonator with a substrate (e.g. substrate 120 made of Fig. 1A) and a piezoelectric layer (e.g. layer 110 from Fig. 1A) comprises one or more intermediate layers (e.g. layer 124 made of Fig. 1B) is coupled to the substrate. In addition, a conductor pattern is provided on a surface of the piezoelectric layer, which includes a pair of busbars (e.g., busbars 132 and 134 from Fig. 1A) with interlocked fingers extending from it to form the IDT. Then, a dielectric capacitor 640 is electrically coupled in series with the IDT of the acoustic volume resonator and comprises a dielectric layer 644 on a surface of one of the busbars (e.g., the first busbar (e.g., 632A)) and at least one metal layer (e.g., the metal layers 632B and / or 642B) on a surface of the dielectric layer 644 opposite the first busbar (e.g., 632A) to form the dielectric capacitor 640.

[0088] Fig. Figure 7 is a top view of a section of a filter device 700 comprising an XBAR with a pair of series-coupled dielectric capacitors, according to an exemplary aspect. As with reference to Fig. As described in Figure 6B, a dielectric capacitor 640 can be coupled in series with one of the busbars of the acoustic resonator. In the alternative aspect described in Fig. As shown in Figure 7, dielectric capacitors 740A and 740B are arranged on opposite sides of the IDT 730 of an acoustic resonator, which is derived from the IDT 130. Fig. 1A can correspond to, as described above.

[0089] It should be noted that the two dielectric capacitors 740A and 740B generally have the same configuration as the one above with reference to Fig. 6A described dielectric capacitor 640. Thus, in this aspect, the filter device 700 includes an additional dielectric capacitor that is electrically coupled in series with the acoustic volume resonator. This additional capacitor also includes a dielectric layer on a surface of a second busbar (e.g., busbar 134). Fig. 1A) from the pair of busbars and at least one metal layer on a surface of the dielectric layer opposite the second busbar to form the additional dielectric capacitor. According to this configuration, the acoustic volume resonator (which includes, for example, the IDT 730) is electrically coupled in series between the dielectric capacitor 740A (e.g., a first series capacitor) and the additional dielectric capacitor 740B (e.g., a second series capacitor).

[0090] Fig. Figure 8 is a graph of the admittance of a filter device with one or more acoustic resonators (e.g., XBARs) as a function of frequency with a series-coupled dielectric capacitor according to an exemplary aspect. In particular, Figure 800 shows the admittance in dB as a function of frequency (GHz) for the filter device, comparing an acoustic resonator with a series capacitor according to the exemplary aspect to a filter device having an acoustic resonator without a series capacitor. The graph was simulated using finite element method (FEM) techniques.

[0091] Specifically, the admittance diagram shows 800 Fig. Figure 8 shows the reduced coupling achieved by adding the series capacitor. Furthermore, electromechanical coupling is defined as the frequency spacing between the resonance and the antiresonance. Reducing this spacing corresponds to reducing the coupling, thus enabling the construction of filters with narrower bands. In this respect, the admittance diagram shows two key resonances, labeled "resonances (fr)" and "antiresonances (fa)." Comparison with the example configuration including the series capacitor shows that the configuration without the series capacitor results in different coupling behavior. As is generally known to those skilled in the art, the definition of coupling is given as follows: Coupling=keff2=fr2−fa2fa2, which shows the relationship between the resonant frequencies and the coupling factor. As in diagram 800 from Fig. As shown in Figure 8, the change in admittance reflects a smaller equivalent capacitance achieved by adding the series capacitor (e.g., the dielectric capacitor 640, as described above).

[0092] In general, the equivalent capacitances can be evaluated as low and high frequencies using the modified Butterworth-Van-Dyke (mBVD) model. At low frequencies, a pair of parallel capacitance values ​​C0 and C is obtained. m , where Lm represents the inductance of the circuit according to the mBVD ​​model. In this aspect, the low-frequency behavior (e.g., the impedance) is given by the equation (Z L = jωL = 2πfL) is defined, which indicates the impedance of the inductor. As the frequency approaches zero, the impedance (Z) approaches zero. L ) zero, which leads to the equivalent capacity (C eq = C0 + C m ) where C0 is the basic capacity and C mThe additional capacitance is due to the mBVD ​​structure. The high-frequency behavior is also analyzed, with the impedance defined similarly; however, as the frequency approaches infinity, (Z) also changes. L ) to infinity. In this scenario, the equivalent capacity simplifies to (C eq = C0), which indicates that at high frequencies only the base capacitance is relevant. In this model, the circuit at low frequencies exhibits a short-circuit representation of C. m and the high-frequency circuit has an open-circuit representation.

[0093] As described above, the exemplary aspects utilize a dielectric capacitor coupled in series with an acoustic resonator. The impedance (Z) L When using the mBVD ​​model, at low frequencies, the impedance (jωL = 2πfL) is defined as (jωL = 2πfL). As the frequency (f) approaches zero, the impedance (Z) approaches zero.L ) zero, from which the equation (1Ceq=1Cseries+1(C0+Cm)) This results in the equivalent capacitance being determined by both the series capacitor (C). series ) as well as the sum of (C0) and (C m ) is affected. In this aspect, the circuit configuration for the mBVD ​​with a series capacitor, where (L m ) and (C m ) are parallel to (C0) and to (C series ) in series. At high frequency, the impedance (Z) L ) is defined similarly as (jωL = 2πfL). As the frequency (f) approaches infinity, the impedance (Z) also approaches infinity. L ) also infinity. The equation for the equivalent capacitance at this frequency is with (1Ceq=1Cseries+1C0) This reflects the fact that at high frequencies, the equivalent capacitance is predominantly determined by the series capacitor (C). series ) and (C0), is affected.

[0094] Fig. Figure 9A is a schematic view of a section of a filter device 900A, comprising an acoustic resonator with a series-coupled dielectric capacitor, according to a further exemplary aspect. In general, the filter device 900A has a similar configuration to that described above with reference to filter device 600. Fig. 6A described. That is, Fig. Figure 9A is a schematic view of a section of a filter device 900A comprising an acoustic resonator (e.g., an XBAR) with a series-coupled dielectric capacitor 940, according to an exemplary aspect. In the partial view in Fig. 9A is a section of the metal pattern shown (e.g., designated as metal 1 or M1) which can form a section of a busbar 932A, wherein the busbar 932A is, for example, one of the pair of busbars 132 and 134, as shown in Fig. 1A shown, can correspond. Furthermore, a second metal pattern 942A (e.g., designated as metal 2 or M2) can be arranged on a surface of the busbar 932A during the formation of the acoustic resonator device. As described above, the metal layer M1 can also be a wire conductor or another metal layer extending from the busbar of the acoustic resonator.

[0095] As further in Fig. As shown in 9B, the at least one metal layer (i.e., the metal layer 932B) can be arranged on a surface of a piezoelectric layer (e.g., the piezoelectric layer 110 in Fig. 1A, and as a piezoelectric layer 910 in Fig. (9B shown), such that the at least one metal layer 932B is essentially coplanar with the first busbar 932A, which is also arranged on the surface of the piezoelectric layer 910. As noted above, the term "essentially" is used here when components, parameters, and the like are generally the same, taking into account minor variations, for example, due to manufacturing fluctuations. Thus, in this context, the term "essentially coplanar" means, according to one exemplary aspect, coplanar or parallel and within the range of ±10% of the coplanarity or parallelism.

[0096] As also in Fig. As shown in Figure 9A, a space 946 extends between metal layer 932B and metal layer 932A in a top view of the surface of the piezoelectric layer 910. It is noted that, according to exemplary aspects, metal layer 932B may be formed by the same metal and metal deposition process as metal layer 932A (which may be a section of a busbar of the acoustic resonator) or it may be formed by separate metal layers. As further shown, one or more additional metal layers M2 (designated as metal layer with reference numeral 942B) may be arranged on top of metal layer 932B to provide a plurality of metal layers, which, in one exemplary aspect, may also be used to adjust the capacitance of the dielectric capacitor 940.As further shown, the filter device 600 has a gap between the metal layers 932A and 932B to prevent short-circuiting of the capacitor.

[0097] Fig. 9B represents a variant of the configuration of the in Fig. 9A shows the filter device 900A, in which the dielectric layer 944 further comprises the space 946 (in Fig. (9A shown) fills the space between the two metal layers M1 and M2 (i.e., metal layers 932A and 932B). In one exemplary aspect, the dielectric layer 944 can be formed by silicon oxide or silicon dioxide. This configuration advantageously enhances the capacitive properties of the filter device 900B. In particular, a metal-oxide-metal capacitor structure is provided with a dielectric layer, such as silicon oxide, that effectively fills the space 946 between the metal layers. In this configuration, the integrity and performance of the capacitor can be maintained to ensure optimized electrical properties for the filter application.

[0098] Fig. Figure 10A is a schematic view of a section of a filter device comprising an acoustic resonator with a dielectric capacitor coupled in series, according to an exemplary aspect. Fig. 10B is a detailed schematic view of the in Fig. Section 10A of the filter device is shown. In general, the filter device 1000 has a similar configuration to that shown above with reference to filter device 600. Fig. 6A and the filter device 900A / 900B from Fig. 9A and Fig. 9B described. That is, Fig. 10A and Fig. Figure 10B is a schematic view of a section of a filter device 1000 comprising an acoustic resonator (e.g., an XBAR) with a series-coupled dielectric capacitor, according to an exemplary aspect. The partial views show a section of a metal pattern (e.g., designated as Metal 1 or M1) forming a busbar 1032A, wherein the busbar 1032A may, for example, correspond to one of the pair of busbars 132 and 134, as shown in Fig. Figure 1A shows that in this exemplary aspect, busbar 1032A corresponds to a section of busbar 132. As described above, the metal layer M1 can also be a wire conductor or another metal layer extending from the busbar of the acoustic resonator. Furthermore, a second metal pattern 1042A (e.g., designated as metal 2 or M2) can be arranged on a surface of busbar 632A during the formation of the acoustic resonator device.

[0099] As described above, the metal layer M1 can also be a wire conductor or another metal layer extending from the busbar of the acoustic resonator. Furthermore, one or more of these layers (or all of them) can, in a top view of the surface of the piezoelectric layer of the filter device, generally correspond to a shape of the dielectric layer 644. It should be noted that this correspondence of one or more layers can arise, for example, from the deposition process for one or more metal layers. For instance, the metal layers 632B and 642B can, in a thickness direction based on the thickness of the dielectric layer 644, correspond at least partially to the dielectric layer 644.

[0100] According to the exemplary aspects from Fig. 10A and Fig. 10B, the metal layer 1042B can be deposited directly onto the dielectric layer 1044. In other words, a first metal pattern (e.g., the metal layer M1), which forms the metal layer 1032A (i.e., a section of the busbar of the acoustic resonator) and includes the metal layer 1032B, is formed on a surface of the piezoelectric layer 1010, which, for example, is the piezoelectric layer 110. Fig. 1A, as described above. In addition, a single metal pattern (e.g., metal layer M2) can be formed on the first metal layer M1 (which comprises metal layers 1032A and 1032B) and the dielectric layer 1044. Otherwise, the configurations of the dielectric capacitor and the filter device are those described above with reference to Fig. 6A to 6C, 7 and 9A - 9B are described similarly.

[0101] Fig. Figures 11A to 11C are graphs of admittance as a function of frequency of the filter device according to example aspects. In particular, the graphs show the admittance as a function of frequency (GHz) for the filter device, comparing an acoustic resonator with a series capacitor according to the example aspect to a filter device that has an acoustic resonator without a series capacitor. The graphs were simulated using finite element method (FEM) techniques.

[0102] A “noise resonance” in series resonators generally causes a loss in the passband, as shown in diagram 1100A in Fig. Figure 11A shows that in this example, resonators are used that have approximately twice the necessary coupling value k. 2exhibit. As described here, the addition of the dielectric capacitors in series allows decoupling of the resonators, effectively shifting the effects of the interference resonance below the passband. Fig. Figure 11B contains diagram 1100B, which illustrates that a capacitor has been added in parallel to the shunt resonators, as indicated by the dotted line in the center figure. In addition, a series capacitor (e.g., a dielectric capacitor, as described here) has also been inserted in series with the resonators, the effects of which are shown by the dashed line, shifting the resonator's resonant frequency upwards (i.e., to the right). Fig. Finally, Figure 11C shows a diagram 1100C representing the maximum available gain (gmax (dB), such as an ideal passband shape) for a typical line-type filter affected by interference resonance (shown as a dotted line), compared to a similar filter device (e.g., a line-type circuit) configured using the series capacitors with coupled resonators described herein (shown as a solid line). As shown, the frequency response of the example configuration (i.e., the solid line) demonstrates that the filter device is not affected by interference resonance. In other words, the dotted line without the dielectric capacitor exhibits a mid-passband disturbance, whereas this maximum interference resonance is eliminated by the series capacitor, as shown by the solid line.Based on the foregoing disclosure, a filter device is provided comprising a plurality of acoustic volume resonators. Furthermore, one or more of the acoustic volume resonators may comprise: a substrate; a piezoelectric layer coupled to the substrate by one or more intermediate layers; and an IDT on a surface of the piezoelectric layer. As described above, the IDT may be a pair of busbars (e.g., busbars 132 and 134 from [reference]). Fig. 1A) comprising a plurality of interlocking fingers extending from it. In an exemplary aspect, the pair of busbars may extend in a first direction, and the interlocking fingers may extend in a second direction that is substantially perpendicular to the first direction.

[0103] Furthermore, a capacitor (e.g., a dielectric capacitor) is electrically coupled in series with the acoustic volume resonator. The capacitor can be formed by a dielectric layer on a surface of a first busbar of the pair of busbars opposite the piezoelectric layer, and at least one metal layer on a surface of the dielectric layer opposite the first busbar. According to the exemplary aspect, the at least one metal layer is further arranged on the surface of the piezoelectric layer such that the at least one metal layer is coplanar with the first busbar. Additionally, a gap extends between the at least one metal layer and the first busbar in a top view of the surface of the piezoelectric layer.In one exemplary aspect, the gap extends in the first direction along a side surface of the first busbar that faces a side surface of the at least one metal layer, as can be seen, for example, in the perspective view from . Fig. Figure 6A shows that the dielectric layer can be arranged in the space between the layers, as also described above.

[0104] Furthermore, it is noted again that the dielectric capacitor can be implemented in series with an IDT of an acoustic resonator, such as the XBAR configurations described here, which combine an XBAR with a cavity (e.g. Fig. 1A, 1B, 2A - 2D, 3A and / or 3B) or include a permanently mounted XBAR, such as the one in Fig.2E shown and described above. Alternatively, the dielectric resonator can also be implemented with other types of SAW or BAW resonators. In both cases, by implementing the dielectric busbar capacitor in series with such acoustic resonators, the resonant frequency of the resonator can be shifted upwards, thereby reducing coupling and enabling the construction of narrower-band filters, as described here.

[0105] It is generally noted that in this description, the embodiments and other examples presented are to be regarded as illustrative and not as limitations of the disclosed or claimed devices and methods. Although many of the examples presented here involve specific combinations of process actions or system elements, it is understood that these actions and elements can be combined in other ways to achieve the same objectives. With reference to the flowcharts, more or fewer steps can be performed, and the steps shown can be combined or further refined to achieve the methods described herein. Actions, elements, and features discussed only in connection with one embodiment are not precluded from playing a similar role in other embodiments.

[0106] As used here, the pair of expressions "upper" and "lower" is interchangeable with the pair "front" and "rear". As used here, "plural" means two or more. As used here, a "set" of elements may comprise one or more such elements. As used here, whether in the descriptive text or the claims, the terms "have", "comprise", "bear", "have", "contain", "include", and the like are to be understood openly, i.e., they mean comprehensive but not limited to. Only the compounding phrases "consisting of" and "essentially consisting of" are closed or semi-closed compounding phrases with respect to the claims. The use of ordering terms such as "first", "second", "third", etc.The use of "and / or" in claims to modify a claim element does not per se imply a priority, precedence, or order of one claim element over another, nor does it indicate the temporal sequence in which actions of a method are performed. Rather, it is used merely as a distinguishing feature to differentiate one claim element with a particular name from another element with the same name (without using the concept of order). As used here, "and / or" means that the listed elements are alternatives, but the alternatives also include any combination of the listed elements. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 63 / 701,013

[0001] US 19 / 340,237

[0001]

Claims

[1] Filter device having the following features: an acoustic resonator that includes the following features: a substrate; a piezoelectric layer coupled to the substrate by one or more intermediate layers; and a conductor pattern on a surface of the piezoelectric layer, wherein the conductor pattern comprises a pair of busbars with a plurality of interlocked fingers extending therefrom to form an interdigital converter (IDT); and a dielectric capacitor electrically coupled in series with the acoustic resonator, wherein the dielectric capacitor comprises a dielectric layer on a surface of a first busbar from the pair of busbars and at least one metal layer on a surface of the dielectric layer, such that the dielectric layer is located between the first busbar and the at least one metal layer to form the dielectric capacitor. [2] Filter device according to claim 1, wherein the first busbar is configured as a first electrode of the dielectric capacitor and the at least one metal layer is configured as a second electrode of the dielectric capacitor, such that the dielectric layer is sandwiched between the first and the second electrode. [3] Filter device according to claim 1, wherein the at least one metal layer is further arranged on the surface of the piezoelectric layer, such that the at least one metal layer is substantially coplanar with the first busbar, and wherein a space extends between the at least one metal layer and the first busbar in a top view of the surface of the piezoelectric layer. [4] Filter device according to claim 3, wherein: the pair of busbars extends in a first direction and the interlocking fingers extend in a second direction, which is essentially perpendicular to the first direction, and wherein the gap extends in the first direction along a side surface of the first busbar which faces a side surface of the at least one metal layer. [5] Filter device according to claim 4, wherein the dielectric layer is silicon oxide and is also arranged in the space between the at least one metal layer and the first busbar. [6] Filter device according to claim 1, wherein the at least one metal layer comprises a plurality of metal layers and the at least one metal layer corresponds to a shape of the dielectric layer in a top view of the surface of the piezoelectric layer. [7] Filter device according to claim 1, further comprising an additional dielectric capacitor electrically coupled in series with the acoustic resonator, wherein the additional capacitor comprises a dielectric layer on a surface of a second busbar from the pair of busbars and at least one metal layer on a surface of the dielectric layer opposite the second busbar to form the additional dielectric capacitor, such that the acoustic resonator is electrically coupled in series between the dielectric capacitor and the additional dielectric capacitor. [8] Filter device according to claim 1, wherein a section of the piezoelectric layer forms a membrane located over a cavity which extends at least partially into one or more intermediate layers, wherein the one or more intermediate layers comprise silicon oxide or silicon dioxide and the dielectric capacitor does not overlap with the cavity in a top view of the piezoelectric layer. [9] Filter device according to claim 1, wherein one or more intermediate layers have a Bragg mirror arranged between the piezoelectric layer and the substrate. [10] Filter device according to claim 1, wherein the IDT is configured such that a high-frequency signal applied to the IDT excites an acoustic volume shear wave in the piezoelectric layer, wherein acoustic energy propagates along a direction substantially orthogonal to the surface of the piezoelectric layer, which is transverse to a direction of an electric field generated by the entangled fingers of the IDT. [11] Filter device having the following features: an acoustic resonator that includes the following features: a substrate; a piezoelectric layer that is coupled to the substrate by one or more intermediate layers; an interdigital converter (IDT) on a surface of the piezoelectric layer, wherein the IDT comprises a pair of busbars with a plurality of interlocking fingers extending therefrom; and a capacitor electrically coupled in series with the acoustic resonator and integrated as a section of a first busbar from the pair of busbars, wherein the capacitor and a pair of metal layers and a dielectric layer are arranged between them. [12] Filter device according to claim 11, wherein the pair of metal layers of the capacitor has the following features: a first busbar from the pair of busbars that is opposite the piezoelectric layer; and at least one metal layer on a surface of the dielectric layer opposite the first busbar. [13] Filter device according to claim 12, wherein the first busbar is configured as a first electrode of the capacitor and the at least one metal layer is configured as a second electrode of the capacitor. [14] Filter device according to claim 12, wherein the at least one metal layer is further arranged on the surface of the piezoelectric layer, such that the at least one metal layer is substantially coplanar with the first busbar, and wherein a space extends between the at least one metal layer and the first busbar in a top view of the surface of the piezoelectric layer. [15] Filter device according to claim 14, wherein: the pair of busbars extends in a first direction and the interlocking fingers extend in a second direction, which is essentially perpendicular to the first direction, wherein the gap extends in the first direction along a side surface of the first busbar which faces a side surface of the at least one metal layer, and the dielectric layer is silicon oxide and is also located in the space between the at least one metal layer and the first busbar. [16] Filter device according to claim 12, wherein the at least one metal layer comprises a plurality of metal layers and the at least one metal layer corresponds to a shape of the dielectric layer in a top view of the surface of the piezoelectric layer. [17] Filter device according to claim 12, which further comprises the following features: an additional dielectric capacitor electrically coupled in series with the acoustic resonator, wherein the additional capacitor is integrated as a section of a second busbar from the pair of busbars, the additional capacitor comprising a dielectric layer on a surface of a second busbar from the pair of busbars and at least one metal layer on a surface of the dielectric layer opposite the second busbar to form the additional dielectric capacitor, such that the acoustic resonator is electrically coupled in series between the dielectric capacitor and the additional dielectric capacitor. wherein the additional capacitor is essentially located midway between the IDT of the acoustic resonator and another acoustic resonator of the filter device. [18] Filter device according to claim 11, wherein a section of the piezoelectric layer forms a membrane located over a cavity which extends at least partially into one or more intermediate layers, wherein the one or more intermediate layers comprise silicon oxide or silicon dioxide and the capacitor does not overlap with the cavity in a top view of the piezoelectric layer. [19] Filter device according to claim 1, wherein one or more intermediate layers have a Bragg mirror arranged between the piezoelectric layer and the substrate. [20] High-frequency module which has the following features: a filter device comprising a plurality of acoustic wave resonators connected in parallel; and a high-frequency circuit coupled to the filter device, wherein the filter device and the high-frequency circuit are housed in a common enclosure, wherein at least one acoustic wave resonator from the plurality of acoustic wave resonators of the filter device comprises the following features: a substrate; a piezoelectric layer that is coupled to the substrate by one or more intermediate layers; a conductor pattern on a surface of the piezoelectric layer, wherein the conductor pattern comprises a pair of busbars with a plurality of interlocked fingers extending therefrom to form an interdigital converter (IDT), and wherein the filter device further comprises a dielectric capacitor which is electrically coupled in series with the acoustic resonator, wherein the dielectric capacitor comprises a dielectric layer on a surface of a first busbar from the pair of busbars and at least one metal layer on a surface of the dielectric layer, such that the dielectric layer is located between the first busbar and the at least one metal layer to form the dielectric capacitor.

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