Acoustic filter device with interleaved grounded inductors

Abstract

There is provided a filter device including: a series resonator connected between a pair of ports; a parallel resonator connected between the ground connection and a node between one or more of the series resonators and one of the pair of ports; and inductors connected between the ground connection and the parallel resonators, respectively. The inductors have interleaved inductance values different from each other. Each of the resonators includes: a substrate; a piezoelectric layer attached to the substrate directly or via one or more intermediate layers; and an interdigital transducer (IDT) on a surface of the piezoelectric layer and including interleaved IDT fingers extending from the first bus bar and the second bus bar, respectively.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Patent Provisional Application No. 63 / 586,277 filed on September 28, 2023 and U.S. Patent Non-Provisional Application No. 18 / 894,037 filed on September 24, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present disclosure relates to radio frequency filters using acoustic wave resonators, and more particularly to filters for communication devices. Background Art

[0003] A radio frequency (RF) filter is a two-port device that is configured to pass certain frequencies and block other frequencies, where "pass" means to transmit with relatively low signal loss, and "block" means to block or significantly attenuate. The frequency range passed by a filter is called the "passband" of the filter. The frequency range blocked by such a filter is called the "stopband" of the filter. Typical RF filters have at least one passband and at least one stopband. The specific requirements for the passband or stopband can depend on the specific application. For example, in some cases, a "passband" can be defined as a frequency range where the insertion loss of the filter is better than a defined value such as 1dB, 2dB, or 3dB, while a "stopband" can be defined as a frequency range where the rejection of the filter is greater than a defined value such as 20dB, 30dB, 40dB, or more (depending on the application).

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

[0005] Performance enhancements of RF filters in wireless systems can have a wide range of impacts on system performance. Improvements in RF filters can be used to provide system performance improvements, such as larger unit sizes, longer battery life, higher data rates, greater network capacity, lower costs, enhanced security, higher reliability, etc. These improvements can be implemented individually and in combination at multiple levels of the wireless system (e.g., at the RF module, RF transceiver, mobile or fixed subsystem, or network level). As the demand for RF filters operating at higher frequencies continues to increase, there is a need for improved filters that can operate at different frequency bands, as well as a need for improved manufacturing processes for making such filters. Summary of the invention

[0006] Currently, RF filters operating at such high frequencies are designed to improve the rejection of stopband frequencies. As described in more detail below, one technique for doing this is to use a grounded inductor in series with the parallel resonator of the RF filter. Providing a tuned inductor to the parallel resonator will produce a transmission zero (T z ) to improve rejection. However, this grounded inductor also produces “flyback” at higher frequencies, which results in worse broadband rejection. In other words, this RF filter experiences flyback, which is a problem with the filter at higher ranges (e.g., F Range2 The degradation within the range of RF frequencies reduces the overall performance of these RF filters. Therefore, the acoustic filter device disclosed herein is configured to suppress flyback while still improving the broadband suppression of the frequency response.

[0007] Therefore, in an exemplary embodiment, a filter device is provided, which includes: at least one series resonator connected between a pair of ports; a plurality of parallel resonators connected between a ground connection and a node between the at least one series resonator and one of the pair of ports; and a plurality of inductors, each of which is connected in series between the ground connection and the plurality of parallel resonators. In addition, at least two of the plurality of inductors have interleaved inductance values ​​that are different from each other. In addition, each of the at least one series resonator and the plurality of parallel resonators includes: a substrate; a piezoelectric layer attached to the substrate directly or via one or more intermediate layers; and an interdigital transducer (IDT) on a surface of the piezoelectric layer and including a plurality of interleaved IDT fingers extending from a first busbar and a second busbar, respectively.

[0008] In another exemplary aspect of the filter device, a plurality of inductors are connected in parallel to each other.

[0009] In another exemplary aspect of the filter device, at least one series resonator includes a plurality of series resonators connected in series between the pair of ports. In addition, each of the plurality of parallel resonators is coupled to a node between a pair of adjacent resonators in the plurality of series resonators or a node between one of the plurality of series resonators and one of the pair of ports.

[0010] In another exemplary aspect of the filter device, the piezoelectric layer and IDT of each of the series resonator and the parallel resonator are configured such that a radio frequency signal applied to the IDT excites a bulk shear acoustic wave in the piezoelectric layer, wherein the acoustic energy propagates in a direction substantially orthogonal to a surface of the piezoelectric layer, the direction being transverse to a direction of an electric field generated by the interlaced fingers of the IDT.

[0011] In another exemplary aspect of the filter device, the substrate of each of the resonators includes a base and an intermediate layer, and the piezoelectric layer includes a portion located above the cavity, and the cavity extends at least partially in the intermediate layer of the substrate. In addition, in an exemplary aspect, the surface of the piezoelectric layer provided with the IDT faces the cavity.

[0012] In another exemplary aspect of the filter device, at least one of the at least one series resonator and the plurality of parallel resonators further includes a Bragg reflector disposed between the substrate and the piezoelectric layer.

[0013] In another exemplary aspect of the filter device, each of the plurality of parallel resonators includes at least two sub-resonators. In addition, a first sub-resonator of each of the at least two sub-resonators is coupled to an inductor of the plurality of inductors, and a second sub-resonator of each of the at least two sub-resonators is directly coupled to a ground connection.

[0014] In another exemplary aspect, a filter device is provided, the filter device comprising: at least one series resonator connected between a pair of ports; a plurality of parallel resonators connected between a ground connection and a node, the node being between the at least one series resonator and one of the pair of ports; and a plurality of inductors, each of which is connected in series between the ground connection and the plurality of parallel resonators. In addition, at least two of the plurality of inductors have interleaved inductance values ​​different from each other. At least one series resonator and each of the plurality of parallel resonators include a piezoelectric layer and an interdigital transducer (IDT) located on a surface of the piezoelectric layer. In this aspect, the piezoelectric layer and the IDT of each of the series resonator and the parallel resonator are configured so that a radio frequency signal applied to the IDT excites a bulk shear acoustic wave in the piezoelectric layer, wherein the acoustic energy propagates in a direction substantially orthogonal to the surface of the piezoelectric layer, the direction being transverse to the direction of the electric field generated by the interleaved fingers of the IDT.

[0015] In another exemplary aspect, a radio frequency module is provided, the radio frequency module comprising: a filter device having at least one series resonator connected between a pair of ports, a plurality of parallel resonators connected between a ground connection and a node (the node is located between the at least one series resonator and one of the pair of ports), and a plurality of inductors respectively connected between the ground connection and the plurality of parallel resonators; and a radio frequency circuit coupled to the filter device, the filter device and the radio frequency circuit being packaged in a common package. In this aspect, at least two of the plurality of inductors have interleaved inductance values ​​different from each other. In addition, at least one series resonator and each of the plurality of parallel resonators include a piezoelectric layer and an interdigital transducer (IDT) located on a surface of the piezoelectric layer. In this aspect, the piezoelectric layer and the IDT of each of the respective resonators are configured so that a radio frequency signal applied to the IDT excites a volume shear acoustic wave in the piezoelectric layer, wherein the acoustic energy propagates in a direction substantially orthogonal to the surface of the piezoelectric layer, the direction being transverse to the direction of the electric field generated by the interleaved fingers of the IDT.

[0016] The simplified overview of the above exemplary aspects is intended to provide a basic understanding of the present disclosure. This overview is not an extensive overview of all conceived aspects, and is neither intended to identify the key or decisive elements of all aspects of the present disclosure, nor to delimit the scope of any or all aspects of the present disclosure. Its sole purpose is to present one or more aspects in a simplified form as a preface to a more detailed description of the present disclosure that follows. In order to achieve the aforementioned objectives, one or more aspects of the present disclosure include the features described in the claims and exemplarily pointed out. . BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate one or more example aspects of the disclosure and, together with the detailed description, explain principles and implementations of one or more example aspects of the disclosure.

[0018] Figure 1A Schematic plan view and schematic cross-sectional view of a film bulk acoustic resonator (XBAR) including lateral excitation.

[0019] Figure 1B Schematic cross-sectional views showing alternative configurations of XBARs.

[0020] Figure 2A yes Figure 1A An enlarged schematic cross-sectional view of a portion of an XBAR.

[0021] Figure 2B yes Figure 1A An enlarged schematic cross-sectional view of an alternative configuration of an XBAR.

[0022] Figure 2C yes Figure 1AAn enlarged schematic cross-sectional view of another alternative configuration of an XBAR.

[0023] Figure 2D yes Figure 1A An enlarged schematic cross-sectional view of another alternative configuration of an XBAR.

[0024] Figure 2E is an enlarged schematic cross-sectional view of a portion of a solidly-mounted XBAR (SM XBAR).

[0025] Figure 3A is a schematic cross-sectional view of an XBAR according to an exemplary aspect.

[0026] Figure 3B is an alternative schematic cross-sectional view of an XBAR according to an exemplary aspect.

[0027] Figure 4 is a graph showing the shear horizontal acoustic modes in the XBAR.

[0028] Figure 5A is used Figure 1A and / or Figure 1B Schematic block diagram of the XBAR filter.

[0029] Figure 5B is a schematic diagram of a radio frequency module including an acoustic wave filtering device according to an exemplary aspect.

[0030] Fig. 6A is a circuit diagram of a filter using a resonator according to an exemplary aspect.

[0031] Figure 6B According to the exemplary aspects Fig. 6A An exemplary graph of the filter response of the circuit diagram shown.

[0032] Fig. 7A is a circuit diagram of a filter using resonators having an interleaved inductor configuration according to an exemplary aspect.

[0033] Figure 7B According to the exemplary aspects Fig. 7A An exemplary graph of the filter response of the circuit diagram shown.

[0034] Fig. 8A is an exemplary layout of a filter device according to an exemplary aspect.

[0035] Figure 8B is an exemplary layout of a filter device having an interleaved inductor configuration incorporating exemplary aspects of the present disclosure.

[0036] Figure 8CAn exemplary graph illustrating a filter response implementation of a filter device according to an exemplary aspect is shown.

[0037] Throughout this specification, elements appearing in the figures are assigned three-digit or four-digit reference numerals, wherein the two least significant digits are specific to the element and the one or two most significant digits are the figure number in which the element is first introduced. Elements not described in conjunction with a figure may be assumed to have the same properties and functions as previously described elements having the same reference numeral. DETAILED DESCRIPTION

[0038] Various aspects of the disclosed bulk acoustic resonator, filter device, and radio frequency module are now described with reference to the accompanying drawings, wherein the same reference numerals may be used to represent the same elements throughout. In the following description, for the purpose of illustration, many specific details are set forth to facilitate a thorough understanding of one or more aspects of the present disclosure. However, it is apparent in some or all instances that any aspect described below may be practiced without adopting the specific design details described below. In other instances, well-known structures and devices are shown in block diagram form to facilitate description of one or more aspects. A simplified overview of one or more aspects of the present invention is given below to provide a basic understanding of the present invention.

[0039] Figure 1A Simplified schematic top view and orthogonal cross-sectional views of a bulk acoustic resonator device, i.e., a laterally excited film bulk acoustic resonator (XBAR) 100, are shown. XBAR resonators, such as resonator 100, can be used in a variety of RF filters, including band-stop filters, band-pass filters, duplexers, and multiplexers. XBARs are particularly suitable for filters for communication bands with frequencies above 3 GHz.

[0040] In general, the XBAR 100 includes a conductor pattern (e.g., a thin film metal layer) formed at one or both surfaces of a piezoelectric layer 110 (piezoelectric plate or piezoelectric layer may be used interchangeably herein), respectively, and the piezoelectric layer 110 has a parallel front side 112 and a rear side 114 (also commonly referred to as a first surface and a second surface, respectively). It should be understood that the term "parallel" generally refers to the front side 112 and the rear side 114 being opposite to each other, and these surfaces are not necessarily flat and precisely parallel to each other. For example, due to manufacturing variations caused by a deposition process, the front side 112 and the rear side 114 may have surface undulations as will be understood by those skilled in the art. In addition, the term "substantially" as used herein is used to describe the situation when components, parameters, etc. are approximately the same (i.e., "substantially constant"), but may vary slightly in practice (e.g., within an acceptable threshold or percentage) due to possible manufacturing variations, as will be understood by those skilled in the art. For the purposes of this disclosure, the use of the term "or" in the claims is used to mean "and / or" unless it is explicitly indicated that only alternatives are referred to or if the alternatives are mutually exclusive.

[0041] According to an exemplary aspect, the piezoelectric layer can be a thin single crystal layer of a piezoelectric material (e.g., lithium niobate, lithium tantalate, lanthanum gallium silicate, gallium nitride, or aluminum nitride). It should be understood that the term "single crystal" does not necessarily mean a completely uniform crystal structure, but can include impurities due to manufacturing differences, as long as the crystal structure is within acceptable tolerances. The piezoelectric layer is cut so that the orientation of the X, Y, and Z crystal axes relative to the front and back sides are known and consistent. In the examples described herein, the piezoelectric layer is Z-cut, that is, the Z axis is perpendicular to the front side 112 and the back side 114. However, XBARs can be manufactured on piezoelectric layers with other crystal orientations, including rotated Z-cut, Y-cut, and rotated YX-cut.

[0042] The Y-cut series (e.g., 120Y and 128Y) is often referred to as 120YX or 128YX, where the "cut angle" is the angle between the y-axis and the normal to the layer. The "cut angle" is equal to β+90°. For example, a layer with Euler angles [0°, 30°, 0°] is often referred to as a "120° rotated Y-cut" or "120Y". Therefore, the Euler angles for 120YX and 128YX are (0, 120-90, 0) and (0, 128-90, 0), respectively. "Z-cut" is often referred to as ZY-cut and is understood to mean that the layer surface is perpendicular to the Z-axis, but the wave propagates along the Y-axis. The Euler angles for ZY-cut are (0, 0, 90).

[0043] In addition to a portion of the piezoelectric layer 110 that forms a diaphragm 115 (the diaphragm 115 is located above the cavity 140 in one or more layers below the piezoelectric layer 110 (e.g., above the substrate or one or more intermediate layers in the substrate) (e.g., spanning the cavity 140 or extending above the cavity 140)), the back side 114 of the piezoelectric layer 110 can be at least partially supported by the surface of the substrate 120. In other words, the back side 114 of the piezoelectric layer 110 can be directly or indirectly coupled or connected to the surface of the substrate 120 via one or more intermediate layers (e.g., a dielectric layer such as a silicon oxide layer). Furthermore, as used interchangeably herein, the phrases "supported by..." or "attached" can mean directly attached, indirectly attached, mechanically supported, structurally supported, or any combination thereof. The portion of the piezoelectric layer located above the cavity (e.g., spanning the cavity or extending above the cavity) may be referred to herein as the "diaphragm" 115 because it is physically similar to the diaphragm of a microphone. As Figure 1A As shown, the diaphragm 115 is adjacent to the rest of the piezoelectric layer 110 around the entire perimeter 145 of the cavity 140. In this context, "adjacent" means "continuously connected without any intermediate." However, in an exemplary aspect, the diaphragm 115 can be configured such that at least 50% of the edge surface of the diaphragm 115 is coupled to the edge of the piezoelectric layer 110.

[0044] According to an exemplary aspect, substrate 120 is configured to provide mechanical support to piezoelectric layer 110. Substrate 120 may be, for example, silicon, sapphire, quartz, or some other material, or combination of materials. Back side 114 of piezoelectric layer 110 may be bonded to substrate 120 using a wafer bonding process. Alternatively, piezoelectric layer 110 may be grown on substrate 120, or supported by or attached to the substrate in some other manner.

[0045] For the purposes of this disclosure, "cavity" has the conventional meaning of "empty space within a solid body". Cavity 140 may be a hole that passes completely through substrate 120 (as shown in section AA), a hole in a dielectric layer (as shown in section AA), or a hole in a dielectric layer (as shown in section AA). Figure 1B 1) or a groove in the substrate 120. For example, the cavity 140 may be formed by selectively etching the substrate 120 before or after directly or indirectly attaching the piezoelectric layer 110 and the substrate 120.

[0046] As shown, the conductor pattern of XBAR 100 includes an interdigital transducer (IDT) 130. IDT 130 includes a first plurality of parallel fingers (e.g., finger 136) extending from a first busbar 132 and a second plurality of fingers extending from a second busbar 134. The first plurality of parallel fingers and the second plurality of parallel fingers are staggered with each other, and they may be "substantially" parallel to each other, for example, due to minor variations (e.g., due to manufacturing tolerances). At least a portion of the staggered fingers overlap a distance AP, which is generally referred to as the "aperture" of the IDT. The center-to-center distance L between the outermost fingers of IDT 130 is the "length" of the IDT.

[0047] exist Figure 1A In the example of FIG. 1 , the IDT 130 is at a surface (e.g., a first surface) of the front side 112 of the piezoelectric layer 110. However, as described below, in other configurations, the IDT 130 may be at a surface (e.g., a second surface) of the back side 114 of the piezoelectric layer 110, or at surfaces of both the front side 112 and the back side 114 of the piezoelectric layer 110, respectively.

[0048] The first busbar 132 and the second busbar 134 are configured as terminals of the XBAR 100, from which a plurality of interlaced fingers extend. In operation, a radio frequency signal or a microwave signal applied between the two busbars 132, 134 of the IDT 130 primarily excites an acoustic mode (i.e., a primary shear acoustic mode) within the piezoelectric layer 110. As will be discussed in further detail, the primary excited shear acoustic mode is a bulk shear mode or bulk acoustic wave, wherein the acoustic energy of the bulk shear acoustic wave is excited by the IDT 130 in the piezoelectric layer 110 and propagates in a direction that is substantially, predominantly, and / or primarily orthogonal to the surface of the piezoelectric layer 110, which direction is also primarily perpendicular or transverse to the direction of the electric field generated by the IDT fingers. That is, when a radio frequency or microwave signal is applied between the two busbars 132, 134, the RF voltage applied to each set of IDT fingers generates a time-varying electric field that is excited laterally relative to the surface of the piezoelectric layer 110. Therefore, in some cases, the predominantly excited acoustic mode can often be referred to as a transversely excited bulk acoustic wave, since, contrary to propagation, displacement occurs primarily in the bulk direction of the piezoelectric layer, as described below with reference to Figure 4 discussed in more detail.

[0049] For the purposes of this disclosure, a "primary acoustic mode" may generally refer to an operating mode that causes a vibration displacement in a primary thickness shear direction (e.g., the X direction), so that the wave propagates substantially and / or primarily in the direction connecting the relative front and rear surfaces of the piezoelectric layer (i.e., the Z direction). In other words, the X-direction component of the wave is significantly smaller than the Z-direction component. The use of the term "primary" in "primary excited acoustic mode" does not necessarily refer to a low-order or high-order mode. Therefore, an XBAR is considered to be a laterally excited thin film bulk wave resonator. One physical constraint is that when a radio frequency or microwave signal is applied between the two busbars 132, 134 of the IDT 130, heat is generated, which must be dissipated from the resonator to improve performance. In general, the heat can be dissipated by lateral conduction across the membrane (e.g., in the electrode itself) and vertical conduction through the cavity to the substrate.

[0050] In either case, the IDT 130 is located at or on the piezoelectric layer 110 such that at least the fingers of the IDT extend at or on a portion of the piezoelectric layer 110 that is located above the cavity 140 (eg, the diaphragm 115), as described herein. Figure 1A As shown, the cavity 140 has a rectangular cross-section, which is larger than the aperture AP and length L of the IDT 130. According to other exemplary aspects, the cavity of the XBAR can have different cross-sectional shapes, such as regular or irregular polygons. The cavity of the XBAR can have more or less than four sides, which can be straight or curved.

[0051] According to an exemplary aspect, the area of ​​XBAR 100 is determined as the area of ​​IDT 130. For example, the area of ​​IDT 130 may be determined based on a measurement of length L multiplied by the width of the aperture AP of the interleaved fingers of IDT 130. As used herein in this disclosure, area is measured in μm. 2 Therefore, as described below, the area of ​​XBAR 100, and thus the total capacitance of XBAR 100, can be adjusted based on design choices.

[0052] In order to facilitate Figure 1A As presented in the sectional view, the geometric pitch and width of the IDT fingers are greatly exaggerated relative to the length (dimension L) and aperture (dimension AP) of the XBAR. A typical XBAR has more than ten parallel fingers in the IDT. For example, according to exemplary aspects, the XBAR may have hundreds or even thousands of parallel fingers in the IDT. Similarly, the thickness of the fingers in the cross-sectional view is greatly exaggerated.

[0053] Figure 1B A schematic cross-sectional view of an alternative XBAR configuration 100' is shown. Figure 1BIn the resonator 100', the cavity 140 (which may generally correspond to Figure 1A The cavity 140 is formed completely in the dielectric layer 124 (eg, silicon oxide or silicon dioxide, such as Figure 1B As shown), the dielectric layer 124 is located on the substrate 120 (in Figure 1B ) and the piezoelectric layer 110 (indicated as Si in Figure 1B Although a single dielectric layer 124 is shown as having a cavity 140 formed therein (eg, by etching), it should be understood that dielectric layer 124 may be formed of multiple individual dielectric layers stacked on top of each other to provide a stack of materials.

[0054] In addition, Figure 1B In the example of FIG. 1 , all sides of the cavity 140 are defined by the dielectric layer 124. However, in other exemplary embodiments, one or more sides of the cavity 140 may be defined by the substrate 120 and / or the piezoelectric layer 110. Figure 1B In the example of FIG. 1 , the cavity 140 has a trapezoidal shape. However, as described above, the cavity shape is not limited and may be a rectangular, elliptical, or other shapes.

[0055] Figure 2A Shows Figure 1A or Figure 1B Detailed schematic cross-sectional view of XBAR 100 (labeled as detail C). Piezoelectric layer 110 is a single crystalline layer of piezoelectric material with a thickness ts. ts may be, for example, 100 nm to 1500 nm. When used for 5G NR and Wi-Fi from 3.4 GHZ to 7 GHz TM When the filter has a frequency band of 100,0 ...

[0056] In this aspect, a front dielectric layer 212 (eg, a first dielectric coating or material) may be formed on the front side 112 of the piezoelectric layer 110. By definition, the "front side" of the XBAR is the surface facing away from the substrate. The front dielectric layer 212 has a thickness tfd. Figure 2A As shown, the front side dielectric layer 212 covers the IDT fingers 238a, 238b, which may correspond to the above with respect to Figure 1A The finger 136 described. Although not in Figure 2A , 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 on the IDT fingers to seal and passivate the fingers. Figure 2A Also not shown in FIG. 2 , the front-side dielectric layer 212 may, for example, also be deposited only on selected IDT fingers 238 a .

[0057] A backside dielectric layer 214 (e.g., a second dielectric coating or material) may also be formed on the back side of the back side 114 of the piezoelectric layer 110. Generally speaking, for the purposes of this disclosure, the term "backside" refers to the side opposite to the conductor pattern of the IDT structure and / or the side opposite to the front side dielectric layer 212. In addition, the backside dielectric layer 214 has a thickness tbd. The front side dielectric layer 212 and the back side dielectric layer 214 may be non-piezoelectric dielectric materials, such as silicon oxide, silicon dioxide, or silicon nitride. Tfd and tbd may be, for example, 0 to 500 nm. Tfd and tbd may be less than the thickness ts of the piezoelectric layer. Tfd and tbd are not necessarily equal, and the front side dielectric layer 212 and the back side dielectric layer 214 are not necessarily the same material. In exemplary aspects, according to various exemplary aspects, either or both of the front side dielectric layer 212 and the back side dielectric layer 214 may be formed of multiple layers of two or more materials.

[0058] The IDT fingers 238a, 238b may include aluminum, substantially (i.e., primarily) aluminum alloys, copper, substantially (i.e., primarily) copper alloys, beryllium, gold, or some other conductive material. A thin (relative to the total thickness of the conductor) layer of another metal 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 ( Figure 1A 132, 134 in the claims) can be made of the same or different materials as these fingers. In various exemplary aspects, the cross-sectional shape of the IDT fingers can be trapezoidal (finger 238a), rectangular (finger 238b), or some other shape. In general, note that the terms "include," "have," "include," and "contain" (and variations thereof) as used herein are open conjunctions and allow for the addition of other elements when used in the claims. In addition, unless the context dictates otherwise, "a" or "an" when used in conjunction with the term "comprising" in a claim or specification means one or more than one.

[0059] The dimension p (i.e., “pitch”) can be considered as the distance between adjacent IDT fingers (e.g., FIG. 2A to FIG. 2D The center-to-center spacing between the IDT fingers 238a, 238b. Figure 2AAs shown, the center point of the center-to-center spacing can be measured at the center of the width "w" of the finger. In some cases, the center-to-center spacing may change if the width of a given finger changes along the length of the finger, if the width and extension direction change, or any variation thereof. In this case, for a given position along the AP, the center-to-center spacing can be measured as an average center-to-center spacing, a maximum center-to-center spacing, a minimum center-to-center spacing, or any variation thereof. Adjacent fingers can each extend from a different busbar, and the center-to-center spacing can be measured from the center of a first finger extending from a first busbar to the center of a second finger adjacent to the first finger and extending from a second busbar. The center-to-center spacing can be constant over the length of the IDT, in which case the dimension p can be referred to as the pitch of the IDT and / or the pitch of the XBAR. However, in alternative exemplary aspects, the center-to-center spacing varies along the length of the IDT, in which case the pitch of the IDT can be the average value of the dimension p over the length of the IDT. The center-to-center spacing from one finger to an adjacent finger when compared to other adjacent fingers may vary continuously in discrete portions of a plurality of adjacent pairs or in any combination thereof. Each IDT finger (e.g., FIG. 2A to FIG. 2D The IDT fingers 238a, 238b in the IDT 130 have a width w measured perpendicular to the long direction of each finger. The width w may also be referred to as a "mark" herein. In general, the width of the IDT fingers can be constant over the length of the IDT, in which case the dimension w can be the width of each IDT finger. However, in another exemplary aspect as will be discussed below, the width of the individual IDT fingers varies along the length of the IDT 130, in which case the dimension w can be the average of the widths of the IDT fingers over the length of the IDT. Note that the pitch p and width w of the IDT fingers are measured in a direction substantially parallel to the length L of the IDT, as shown in FIG. Figure 1A As defined in .

[0060] In general, the IDT of an XBAR is significantly different from the IDT used in a surface acoustic wave (SAW) resonator, mainly in that the IDT excitation of an XBAR is as follows: Figure 4The principal shear acoustic mode (also referred to as the principal shear mode, principal shear thickness mode, etc.) described in more detail is a mode in which the SAW resonator excites surface waves during operation. In addition, in a SAW resonator, the pitch of the IDT is one-half the wavelength of the acoustic wave at the resonant frequency. In addition, the mark-to-pitch ratio of the SAW resonator IDT is typically close to 0.5 (i.e., the mark or finger width is approximately one-quarter the wavelength of the acoustic wave at resonance). In an XBAR, the pitch p of the IDT is typically 2 to 20 times the width w of the finger. In addition, the pitch p of the IDT is typically 2 to 20 times the thickness ts of the piezoelectric layer 110. In addition, the width of the IDT fingers in the XBAR is not limited to one-quarter the wavelength of the acoustic wave at resonance. For example, the width of the XBAR IDT fingers can be 500nm or greater, so that the IDT can be manufactured using optical lithography. The thickness tm of the IDT fingers can be from 100nm to about equal to the width w, because the lithography process generally cannot support a configuration in which the thickness is greater than the width. The busbar of the IDT ( Figure 1A The thickness of the IDT finger 132, 134) may be equal to the thickness tm of the IDT finger, less than the thickness tm of the IDT finger, greater than the thickness tm of the IDT finger, or any combination thereof. Note that the XBAR device described herein is not limited to the size range described herein.

[0061] Furthermore, unlike a SAW filter, the resonant frequency of an XBAR depends on the total thickness (i.e., in the vertical or thickness direction) of its diaphragm, including the piezoelectric layer 110 and the front and back dielectric layers 212 and 214 disposed thereon. In an exemplary aspect, the thickness of one or both dielectric layers (i.e., on opposite surfaces of the piezoelectric layer) may be varied to change the resonant frequency of various XBARs in the filter. For example, a parallel resonator in a ladder filter circuit may include a thicker dielectric layer to reduce the resonant frequency of the parallel resonator relative to a series resonator having a thinner dielectric layer, thereby reducing the overall thickness.

[0062] Return to reference Figure 2A , the thickness tfd of the front dielectric layer 212 above the IDT fingers 238a, 238b can be greater than or equal to the minimum thickness required to process and passivate the IDT fingers and other conductors on the front side 112 of the piezoelectric layer 110. According to an exemplary aspect, the minimum thickness can be, for example, 10nm to 50nm, depending on the material of the front dielectric layer and the method of deposition. The thickness of the back dielectric layer 214 can be configured to a specific thickness to adjust the resonant frequency of the resonator, as will be described in more detail below.

[0063] although Figure 2A The configuration of the IDT fingers 238a and 238b at the front side 112 of the piezoelectric layer 110 is disclosed, but alternative configurations may be provided. For example, Figure 2BAn alternative configuration is shown (labeled as detail C') in which the IDT fingers 238a, 238b are at the back side 114 of the piezoelectric layer 110 (i.e., facing the cavity) and are covered by the back side dielectric layer 214. The front side dielectric layer 212 can cover the front side 112 of the piezoelectric layer 110. In an exemplary aspect, the dielectric layer disposed on the diaphragm of each resonator can be trimmed or etched to adjust the resonant frequency. However, if the dielectric layer is on the side of the diaphragm facing the cavity, there will be changes in the stray modes (e.g., caused by the coating on the fingers). In addition, the signature will change due to the passivation layer coated on top of the IDT, which can also cause strays. Therefore, as Figure 2B As shown, by positioning the IDT fingers 238a, 238b at the back side 114 of the piezoelectric layer 110, the need to account for frequency variations and their impact on spurs may be eliminated compared to when the IDT fingers 238a and 238b are on the front side 112 of the piezoelectric layer 110.

[0064] Figure 2C An alternative configuration is shown (labeled as detail C"), in which the IDT fingers 238a, 238b are on the front side 112 of the piezoelectric layer 110 and are covered by the front side dielectric layer 212. The IDT fingers 238c, 238d are also on the back side 114 of the piezoelectric layer 110 and are also covered by the back side dielectric layer 214. As previously described, the front side dielectric layer 212 and the back side dielectric layer 214 are not necessarily the same thickness or the same material.

[0065] Figure 2D Another alternative configuration is shown (labeled as detail C''') in which the IDT fingers 238a, 238b are on the front side 112 of the piezoelectric layer 110 and are covered by the front side dielectric layer 212. The surface of the front side dielectric layer is planarized. The front side dielectric layer may be planarized, for example, by polishing or some other method. A thin layer of dielectric material having a thickness tp may cover the IDT fingers 238a, 238b to seal and passivate the fingers. The dimension tp may be, for example, 10 nm to 50 nm.

[0066] Above about FIG. 2A to FIG. 2D Each of the described XBAR configurations includes a diaphragm spanning a cavity. However, in alternative aspects, the bulk acoustic resonator may be rigidly mounted, with the diaphragm having IDT fingers mounted on or over a Bragg mirror, which in turn may be mounted on a substrate.

[0067] Specifically, Figure 2E A detailed schematic cross-sectional view of a securely mounted XBAR (SM-XBAR) is shown. Note that in addition to having a securely mounted configuration, Figure 2E Generally speaking, Figure 1A. In this aspect, the SM-XBAR includes a piezoelectric layer 110 and an IDT (of which only two fingers 236 are visible), wherein the dielectric layer 212 is disposed on the piezoelectric layer 110 and the IDT fingers 236. Similar to the above configuration, the piezoelectric layer 110 has parallel front and rear surfaces. Dimension ts is the thickness of the piezoelectric layer 110. The width of the IDT fingers 236 is dimension w, the thickness of the IDT fingers is dimension tm, and the IDT pitch is dimension p.

[0068] and Figure 1A The XBAR device shown is opposite, Figure 2E The IDT of the SMXBAR in the embodiment of the present invention is not formed on the diaphragm that spans the cavity in the substrate. Instead, the acoustic Bragg reflector 240 is sandwiched between the surface 222 of the substrate 220 and the back surface of the piezoelectric layer 110. The term "sandwiched between" means that the acoustic Bragg reflector 240 is disposed between the surface 222 of the substrate 220 and the back surface of the piezoelectric layer 110 and is mechanically attached to the surface 222 of the substrate 220 and the back surface of the piezoelectric layer 110. In some cases, additional material layers (e.g., one or more dielectric layers) may be disposed between the acoustic Bragg reflector 240 and the surface 222 of the substrate 220 and / or between the Bragg reflector 240 and the back surface of the piezoelectric layer 110. Such additional material layers may be present, for example, to facilitate bonding of the piezoelectric layer 110, the acoustic Bragg reflector 240, and the substrate 220.

[0069] The acoustic Bragg reflector 240 may be an acoustic mirror configured to reflect at least a portion of a primary acoustic mode excited in a piezoelectric body, and includes a plurality of dielectric layers alternating between a material having a high acoustic impedance and a material having a low acoustic impedance. The acoustic impedance of a material is the product of the shear wave velocity and density of the material. "High" and "low" are relative terms. For each layer, the standard for comparison is an adjacent layer. The acoustic impedance of each "high" acoustic impedance layer is higher than the acoustic impedance of two adjacent low acoustic impedance layers. The acoustic impedance of each "low" acoustic impedance layer is lower than the acoustic impedance of two adjacent high acoustic impedance layers. As discussed above, the primary acoustic mode in the XBAR piezoelectric layer is a shear bulk wave. In an exemplary aspect, the thickness of each layer of the acoustic Bragg reflector 240 is equal to or approximately one-quarter of the wavelength in the layer of a shear bulk wave having the same polarization as the primary acoustic mode at or near the resonant frequency of the SM XBAR. Dielectric materials with relatively low acoustic impedance include silicon dioxide, carbon-containing silicon oxide, and certain plastics such as cross-linked polyphenylene polymers. Materials with relatively high acoustic impedance include hafnium oxide, silicon nitride, aluminum nitride, silicon carbide. All high acoustic impedance layers of the acoustic Bragg reflector 240 do not have to be the same material, and all low acoustic impedance layers do not have to be the same material. Figure 2EIn the example of , the acoustic Bragg reflector 240 has a total of six layers, but the acoustic Bragg reflector may have more or less than six layers in alternative configurations.

[0070] The IDT fingers (e.g., IDT fingers 236, 238a, and 238b) may be disposed on the surface of the front side 112 of the piezoelectric layer 110. Alternatively, the IDT fingers (e.g., IDT fingers 236, 238a, and 238b) may be disposed in a groove formed in the surface of the front side 112. The groove may extend partially through the piezoelectric layer. Alternatively, the groove may extend completely through the piezoelectric layer.

[0071] Figure 3A and Figure 3B The XBAR 100 is shown along Figure 1A Two exemplary cross-sectional views of the section AA defined in FIG. Figure 3A In the embodiment, the piezoelectric layer 310 corresponding to the piezoelectric layer 110 is directly attached to the substrate 320, which may correspond to Figure 1A In addition, a cavity 340 that does not completely penetrate the substrate 320 is formed in the substrate below the portion of the piezoelectric layer 310 that includes the IDT of the XBAR (ie, the diaphragm 315). In an exemplary aspect, the cavity 340 may correspond to Figure 1A and / or Figure 1B In an exemplary aspect, the cavity 340 can be formed, for example, by etching the substrate 320 before attaching the piezoelectric layer 310. Alternatively, the cavity 340 can be formed by etching the substrate 320 with a selective etchant that reaches the substrate through one or more openings provided in the piezoelectric layer 310.

[0072] Figure 3BAn alternative aspect is shown, in which the substrate 320 includes a substrate 322, and an intermediate layer 324 disposed between the piezoelectric layer 310 and the substrate 322. For example, the substrate 322 can be silicon (e.g., a silicon support substrate), and the intermediate layer 324 can be silicon dioxide or silicon nitride or some other material, such as an intermediate dielectric layer. That is, in this aspect, the substrate 322 and the intermediate layer 324 are collectively referred to as the substrate 320. As further shown, a cavity 340 is formed in the intermediate layer 324 below the portion of the piezoelectric layer 310 that contains the IDT fingers of the XBAR (i.e., the diaphragm 315). For example, the cavity 340 can be formed by etching the intermediate layer 324 before attaching the piezoelectric layer 310. Alternatively, the cavity 340 can be formed by etching the intermediate layer 324. In other example embodiments, the cavity 340 can be defined in the intermediate layer 324 by other means, which is different from whether the intermediate layer 324 is etched to define the cavity 340. In some cases, etching may be performed using a selective etchant that reaches the substrate through one or more openings (not shown) provided in piezoelectric layer 310 .

[0073] In this case, the diaphragm 315 (which in exemplary aspects may correspond to, for example, Figure 1A The diaphragm 115 of the piezoelectric layer 310 may be adjacent to the remaining portion of the piezoelectric layer 310 surrounding most of the periphery of the cavity 340. For example, the diaphragm 315 may be adjacent to the remaining portion of the piezoelectric layer 310 surrounding at least 50% of the periphery of the cavity 340. Figure 3B As shown, cavity 340 extends completely through intermediate layer 324. That is, diaphragm 315 may have an outer edge facing piezoelectric layer 310, wherein at least 50% of the edge surface of diaphragm 315 is coupled to the edge of piezoelectric layer 310 facing diaphragm 315. This configuration provides increased mechanical stability of the resonator.

[0074] In other configurations, the cavity 340 may extend partially into the intermediate layer 324 but not completely through the intermediate layer 324 (i.e., the intermediate layer 324 may extend over the bottom of the cavity on top of the substrate 322) or may extend through the intermediate layer 324 and (partially or completely) into the substrate 322. As described above, it should be understood that the interleaved fingers of the IDT may be arranged in accordance with various exemplary aspects. Figure 3A and Figure 3B On either surface or both surfaces of the diaphragm 315.

[0075] Figure 4 is a graphical illustration of the principal excited acoustic modes of interest in the XBAR. Figure 4A small portion of an XBAR 400 is shown, including a piezoelectric layer 410 and three interleaved IDT fingers 430. In general, according to exemplary aspects, an exemplary configuration of the XBAR 400 may correspond to that described above and in FIG. 2A to FIG. 2D Thus, it should be understood that piezoelectric layer 410 may correspond to piezoelectric layer 110 and IDT fingers 430 may be implemented according to any configuration of fingers 238a and 238b, for example.

[0076] In operation, an RF voltage is applied to the interlaced fingers 430. This voltage produces a time-varying electric field between these fingers. The direction of the electric field is transverse (i.e., transversely excited) or primarily parallel to the surface of the piezoelectric layer 410, as indicated by the arrow labeled "Electric Field." Due to the high dielectric constant of the piezoelectric layer 410, the electric field is highly concentrated in the piezoelectric layer relative to air. The transverse electric field induces shear deformation in the piezoelectric layer 410, thereby strongly exciting shear acoustic modes in the piezoelectric layer 410. In this context, "shear deformation" is defined as a deformation in which parallel planes in a material remain parallel and maintain a constant distance while translating relative to each other. In other words, parallel planes of the material are displaced laterally relative to each other. "Shear acoustic modes" are defined as acoustic vibration modes in a medium that cause shear deformation of the medium. The shear deformation in the XBAR 400 is represented by curve 460, where the adjacent small arrows provide a schematic indication of the direction and amplitude of the atomic motion. Note that for ease of illustration in Figure 4 In the visualization in FIG. 4 , the extent of atomic motion and the thickness of the piezoelectric layer 410 have been exaggerated. Although the atomic motion is primarily lateral (i.e., Figure 4 ), but the direction of the acoustic energy flow of the primarily excited shear acoustic mode is substantially and / or primarily normal to the surface of the piezoelectric layer, as indicated by arrow 465.

[0077] BARs based on shear acoustic wave resonances can achieve better performance than the current state-of-the-art film bulk acoustic resonator (FBAR) and firmly mounted resonator bulk acoustic wave (SMR BAW) devices with an electric field applied in the thickness direction. In such devices, the acoustic mode is compressed, with atomic motion and acoustic energy flow in the thickness direction. In addition, the piezoelectric coupling of shear wave XBAR resonances can be high (>20%) compared to other acoustic resonators. Therefore, high piezoelectric coupling enables the design and realization of microwave and millimeter wave filters with considerable bandwidth.

[0078] Figure 5A1 is a schematic circuit diagram and layout of a high frequency bandpass filter 500 using XBARs, such as the general XBAR configuration 100 described above (e.g., bulk acoustic resonators). The filter 500 has a conventional ladder filter architecture (which may include a split ladder filter architecture in which the filter is split between multiple chips) having multiple bulk acoustic resonators, including four resonators 510A, 510B, 510C, and 510D and three parallel resonators 520A, 520B, and 520C. As discussed in more detail below, the filter 500 may also include additional reactive components, such as inductors ( Figure 5A not shown).

[0079] The series resonators 510A, 510B, 510C, and 510D are connected in series between the first port and the second port (hence the term "series resonator"). Figure 5A , the first port and the second port are labeled "In" and "Out", respectively. However, the filter 500 is bidirectional and either port can be used as the input or output of the filter. At least three parallel resonators (e.g., parallel resonators 520A, 520B, and 520C) are each connected from a node between adjacent series resonators to a ground connection. For example, parallel resonator 520A is connected between the ground connection and a node between adjacent series resonators 510A and 510B. In addition, the filter may include Figure 5A , and additional reactive components (e.g., inductors) not shown. In an exemplary aspect, all parallel resonators and series resonators are XBARs (e.g., any of the XBAR configurations 100 and / or 100' as described above). Including four series resonators and three parallel resonators is an example. The filter can have more or less than seven total resonators, more or less than four series resonators, and more or less than three parallel resonators. Typically, for split ladder filter and non-split ladder filter architectures, all series resonators are connected in series between the input and output of the filter, and all parallel resonators are typically connected between ground and the input, output, or a node between two series resonators.

[0080] In the exemplary filter 500, the series resonators 510A, 510B, 510C, and 510D and the parallel resonators 520A, 520B, and 520C of the filter 500 can be formed on at least one piezoelectric material layer 530 (and in some cases, a single piezoelectric material layer 530) bonded to a silicon substrate (not visible). However, in alternative aspects, each resonator can be formed on a separate corresponding piezoelectric layer of each resonator, wherein all resonators are located on the same chip. However, in some cases, for example, different resonators of the filter can be bonded to separate substrates. This can produce a split ladder architecture that can include one or more separate chips that include separate piezoelectric layers and IDTs of one or more bulk acoustic resonators, which are then constructed together to form the entire split ladder filter. In addition, each resonator includes a corresponding IDT (not shown), wherein at least the fingers of the IDT are disposed above a cavity or acoustic reflector in the substrate. In this and similar contexts, the term "corresponding" means "relating things to one another," that is, having a one-to-one correspondence. Figure 5A In FIG. 5 , a cavity is schematically shown as a dashed rectangle (eg, rectangle 535 ). In this example, each IDT is disposed above a corresponding cavity. In other filters, the IDTs of two or more resonators may be disposed above a single cavity.

[0081] Each of the resonators 510A, 510B, 510C, 510D, 520A, 520B, and 520C in the filter 500 has a resonance where the admittance of the resonator (also interchangeably referred to as a Y parameter) is very high and an anti-resonance where the admittance of the resonator is very low. The resonance and anti-resonance occur at the resonant frequency and the anti-resonance frequency, respectively, and the resonant frequency and the anti-resonance frequency can be the same or different for the various resonators in the filter 500. In short, each resonator can be regarded as a short circuit at its resonant frequency and an open circuit at its anti-resonance frequency. At the resonant frequency of the parallel resonator and the anti-resonance frequency of the series resonator, the input-output transfer function will be close to zero. In a typical filter, the resonant frequency of the parallel resonator is below the lower edge of the filter passband, and the anti-resonance frequency of the series resonator is above the upper edge of the passband.

[0082] The frequency range between the resonant frequency and the anti-resonant frequency of the resonator corresponds to the coupling of the resonator. Depending on the design parameters of the filter 500, each of the resonators 510A, 510B, 510C, 510D, 520A, 520B, and 520C can have a specific coupling parameter to which the corresponding resonator is tuned in order to achieve the desired frequency response of the filter 500.

[0083] According to an exemplary aspect, each of the series resonators 510A, 510B, 510C, and 510D and the parallel resonators 520A, 520B, and 520C may have a configuration as described above with respect to Figures 1A to 2D Alternatively, each of the series resonators 510A, 510B, 510C, 510D and the parallel resonators 520A, 520B, and 520C may have an XBAR configuration, wherein the series resonators 510A, 510B, 510C, 510D and / or the parallel resonators 520A, 520B, and 520C may be securely mounted on or above a Bragg reflector (e.g., as Figure 2E As shown), the Bragg reflector can then be mounted on a substrate.

[0084] Figure 5B is a schematic diagram of a radio frequency module including an acoustic wave filter device according to an exemplary aspect. Specifically, Figure 5B A radio frequency module 540 is shown including one or more acoustic wave filters 544 according to an exemplary aspect. The radio frequency module 540 shown also includes a radio frequency (RF) circuit (or RF circuit) 543. In an exemplary aspect, as described above with reference to Figure 5A As depicted, acoustic wave filter 544 may include one or more filters 500 including an XBAR (eg, a bulk acoustic resonator as described herein).

[0085] Figure 5B The acoustic wave filter 544 shown includes terminals 545A and 545B (e.g., a first terminal and a second terminal). Terminals 545A and 545B can be used, for example, as input contacts and output contacts of the acoustic wave filter 544. Although two terminals are shown, any suitable number of terminals may be implemented for a particular application. The acoustic wave filter 544 and the RF circuit 543 are Figure 5B The package substrate 546 (e.g., a common substrate) in the embodiment of the present invention is a package substrate 546 (e.g., a common substrate). The package substrate 546 can be a laminate substrate. The terminals 545A and 545B can be electrically connected to the contact portions 547A and 547B on the package substrate 546 through electrical connectors 548A and 548B, respectively. For example, the electrical connectors 548A and 548B can be bumps or wire bonds. In an exemplary aspect, by using or not using the package substrate 546, the acoustic wave filter 544 and the RF circuit 543 can be packaged together in a common package.

[0086] The RF circuit 543 may include any suitable RF circuit. For example, the RF circuit may 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 543 may be electrically connected to one or more acoustic wave filters 544. The RF module 540 may include one or more packaging structures, for example, to provide protection and / or facilitate easier handling of the RF module 540. Such a packaging structure may include an overmolded structure formed above the packaging substrate 546. The overmolded structure may encapsulate some or all components of the RF module 540.

[0087] As described above, an RF filter (eg, filter 500) may be configured to use a grounded inductor in series with a parallel resonator to create a transmission zero (T z ), thereby improving the rejection of the frequency response. Fig. 6A A circuit diagram of a filter (or portion of a filter) using a resonator with a series grounded inductor according to an exemplary aspect is shown.

[0088] As shown in the figure, Fig. 6A Schematic circuit diagrams and layouts of filters 600 and 602 using resonators (e.g., XBARs such as the general XBAR configuration 100 described above) are shown. The filters 600 and 602 have filter architectures that include series resonators 610A and 610A', respectively, and parallel resonators 620A and 620A', respectively. The parallel resonators 620A and 620A' each include at least two parallel resonators (e.g., a pair of parallel resonators or at least two parallel sub-resonators) connected in parallel. The series resonators 610A and 610A' are connected in series between a first port and a second port, which may be, for example, the input and output of the filters 600 and 602. That is, at Fig. 6A In the embodiment of the present invention, the first and second ports of 600 and 602 are labeled as "In", "In'" and "Out", "Out'", respectively. However, filters 600 and 602 are bidirectional, and either port can serve as the input or output of the filter. Parallel resonators 610A and 610A' are connected to ground from the node between the series resonators. If filters 600 and / or 602 are implemented in a ladder filter architecture as described above, the In port and the Out port can correspond to the above description of Figure 5A Describes the port.

[0089] As further shown and described below, filter 602 includes an additional reactive component, namely inductor 660. In either case, the parallel resonator and the series resonator can be XBARs. As an example, one series resonator and two parallel resonators are included in filters 600 and 602. As will be appreciated by those skilled in the art, according to various ladder filter architectures, the filter can have more or less than three resonators, more or less than one series resonator, and more or less than two parallel resonators in total. Typically, all series resonators are connected in series between the input and output of the filter. All parallel resonators are typically connected between a ground point and an input, an output, or a node between two adjacent series resonators.

[0090] As generally described above, filter devices (eg, filters 600 and 602 ) are configured to pass signals of certain frequencies (or frequency bands) and block signals of other frequencies (or frequency bands). Figure 6B According to the exemplary aspects Fig. 6A More specifically, Figure 6B The admittance (in dB) of filters 600 and 602 as a function of frequency is shown, which was simulated using finite element method (FEM) simulation techniques.

[0091] As shown, filter 600 has a Range1 The filter 600 has a stop band (interchangeably referred to herein as a rejection band) within the Range2 There is no effective suppression in the filter 600, as shown by the dashed line marked by "Δ". To improve the suppression of the filter 600, a grounded inductor 660 can be added in series with the parallel resonator 620A'. By doing so, Figure 6B As shown by the dashed line marked with “□”, filter 602 has a larger F than filter 600. Range1 That is, arrow 682 indicates that the F Range1 Improved response (ie, steeper edge with lower admittance) between the inner filters 600 and 602. In an exemplary aspect, as shown at m1, at a frequency of 7.55 GHz, the admittance is -21.61 dB, which is within the first frequency range F Range1 However, compared to filter 600, the trade-off is that filter 602 has a Range2 For example, arrow 684 indicates that in the frequency range F Range2 The reduced response between the inner filters 600 and 602. Frequency Range F Range2 This admittance within may be considered as flyback and may result in the erroneous passage of unwanted high frequency signals that would otherwise be blocked from passing through filter 602 .

[0092] Thus, according to this aspect, adding the inductor 660 in series with the parallel resonator 620A' can shift the resonance of the filter to a lower frequency while maintaining the same anti-resonance, thereby effectively increasing the coupling of the resonators, but at the expense of flyback. That is, for the filter 602, placing the inductor 660 in series with the parallel resonator 620A' can increase the resonance of the filter to a lower frequency in the first frequency range F Range1 provides improved performance within the second frequency F Range2 The result is a reduction in the overall performance of filter 602 compared to filter 600, thereby creating a "flyback" or filter degradation within the filter 602. In other words, the tuned inductor with parallel resonator 620A' will create a transmission zero (T z ) to improve suppression, but inductor 660 produces flyback at higher frequencies, resulting in lower suppression of certain data signals in this high frequency range.

[0093] Given that Fig. 6A To overcome the limitations of the filter 602 shown, exemplary aspects provide a filter having improved broadband rejection while reducing flyback in the high frequency range. Specifically, Fig. 7A is a circuit diagram of a filter implementing resonators with an interleaved inductor configuration according to an exemplary aspect. Figure 7B According to the exemplary aspects Fig. 7A An exemplary graph of the filter response of the circuit diagram shown.

[0094] Generally speaking, Fig. 7A Shown above about Fig. 6A The filter 600 described above is identical to the filter 600, and therefore, the details of the filter 600 will not be repeated here. However, Fig. 7A A schematic circuit diagram and layout of a filter 700 using an XBAR resonator (e.g., XBAR configuration 100) according to an exemplary aspect is shown. Specifically, the filter 700 has a filter architecture that includes a series resonator 710A and parallel resonators 720A and 720B (e.g., a pair of parallel resonators or a pair of parallel sub-resonators). The series resonator 710A is connected in series between a first port and a second port. Likewise, Fig. 7A The first and second ports of the filter 700 are shown, which are labeled "In", "In'" and "Out", "Out'". However, the filter 700 is bidirectional and either port can be used as the input or output of the filter. The parallel resonators 720A and 720B are connected in parallel from the node between the series resonators to ground. According to an exemplary aspect, Fig. 7A The filter shown can be based on the above Figure 5AA similar ladder filter configuration as described is implemented.

[0095] According to an exemplary aspect, filter 700 includes a pair of inductors 760 and 762 coupled in parallel to each other. Note again that, as an example, one series resonator (e.g., resonator 710A) and two parallel resonators (e.g., resonators 720A and 720B) are included in filter 700. The filter (e.g., a ladder filter configuration) can have more or less than three resonators in total, more or less than one series resonator, and more or less than two resonators. Typically, all series resonators are connected in series between the input and output of the filter. All parallel resonators are typically connected between ground and the input, output, or a node between two adjacent series resonators. Each resonator of filter 700 can be represented by the above description of Figure 1A to Figure 1B , FIG. 2A to FIG. 2E as well as FIG. 3A to FIG. 3B Any of the XBAR resonators shown and described may be implemented.

[0096] According to an exemplary embodiment, filter 700 implements different inductors on each ground branch of the parallel resonator (ie, parallel resonators 720A and 720B). By using inductors 760 and 762, multiple tunable frequencies T can be generated. zs According to an exemplary aspect, filter 700 has a ground inductance of 1.3 nH that is effectively split into separate inductances (eg, 0.3 nH and 1.0 nH) of inductors 760 and 762 that are connected to each branch of parallel resonators 720A and 720B, respectively.

[0097] Thus, according to an exemplary aspect, a filter 700 is provided, which includes one or more series resonators (e.g., 710A) connected between a pair of ports (e.g., "IN" and "OUT" ports), a plurality of parallel resonators (e.g., 720A and 720B) connected between a ground connection and a node between at least one series resonator and one of the pair of ports; and a plurality of inductors (e.g., 760 and 762), connected in parallel with each other and respectively located between the ground connection and the plurality of parallel resonators (e.g., 720A and 720B). In addition, at least two or more of the plurality of inductors have interleaved inductance values ​​different from each other, so that the plurality of inductors are configured to reduce the flyback effect in the high frequency range. As described above and in an exemplary aspect, each of the series resonators and the parallel resonators includes: a substrate; at least one piezoelectric layer, which is attached to the substrate directly or via one or more intermediate layers; and an interdigital transducer (IDT), at at least one piezoelectric layer and including a plurality of interleaved IDT fingers extending from a first busbar and a second busbar, respectively.

[0098] As further described above, Figure 7B According to the exemplary aspects Fig. 7A More specifically, Figure 7B The admittance (in dB) of filters 600 and 700 as a function of frequency is shown, which was simulated using finite element method (FEM) simulation techniques.

[0099] Generally speaking, filters 600 and 700 are configured to pass signals of certain frequencies and block signals of other frequencies, as generally described above. By adding interleaved ground inductors 760 and 762 to resonators 720A and 720B, filter 700 is configured to pass signals of certain frequencies and block signals of other frequencies in a first frequency range F Range1 However, this configuration also addresses the "flyback" effect that filter 602 would otherwise encounter, such as Figure 6B Specifically, arrow 782 indicates the improved response and rejection between filters 600 and 700. As shown at m1, at a frequency of 11.45 GHz, the admittance is -18.12 dB, 11.45 GHz being within the second frequency range F Range2 Inside.

[0100] In addition, filter 700 has a second rejection compared to filter 600. For example, arrow 784 indicates an increased response of filter 700 (as shown by the dashed line labeled "□" of filter 700) compared to the frequency response of filter 600 (as shown by the dashed line labeled "Δ"). For reference, the frequency of filter 602 is shown as a dashed line labeled "◊".

[0101] Specifically, as shown at m2, at a frequency of 20.65 GHz, the admittance is -20.51 dB, and 20.65 GHz is also within the second higher frequency range F Range2 Therefore, the interleaved inductor configuration of filter 700 reduces the Figure 7B Flyback shown. The specific frequency response of a pair of parallel resonators 720A and 720B with staggered inductors 760 and 762 is shown as having anti-resonance peaks at 11.45 GHz (identified as m3) and 20.65 GHz (identified as m4), respectively. In fact, this configuration pulls the overall frequency response of the filter 700 downward at points m1 and m2 (as shown by the dotted line marked by "□". In fact, staggered grounded inductors 760 and 762 with staggered inductance values ​​can also be implemented in such high frequency filters for spurious suppression in, for example, S2 mode, A3 mode, and for example, improved suppression in the Wi-Fi 6 GHz region. According to an exemplary aspect, the use of staggered grounded inductors 760 and 762 improves suppression near the target high frequency (e.g., 28 GHz).

[0102] Fig. 8A and Figure 8B The reference is merged Fig. 6A and Fig. 7A Specifically, Fig. 8A is an exemplary layout of filter 800 according to an exemplary aspect. In addition, Figure 8B An exemplary layout of a filter 800 ′ having an interleaved inductor configuration incorporating exemplary aspects of the present disclosure is shown.

[0103] As generally shown, both filters 800 and 800' have filter architectures that include four series resonators 810A (e.g., Se1), 810B (e.g., Se3), 810C (e.g., Se5), 810D (e.g., Se7) and 810A' (e.g., Se2), 810B' (e.g., Se4), 810C' (e.g., Se6), 810D' (e.g., Se8), respectively. In addition, filter 800 includes four parallel resonators 820A (e.g., Sh2), 820B (e.g., Sh4), 820C (e.g., Sh6), and 820D (e.g., Sh8). Filter 800' includes five parallel resonators 820A' (e.g., Sh1), 820B' (e.g., Sh3), 820C' (e.g., Sh5), 820D' (e.g., Sh7), and 820E' (e.g., Sh9). It should be understood that Fig. 8A and Figure 8B The filter configuration shown is similar to Figure 5A The resonator layout shown is similar and can be used with Figure 1A to Figure 1B , FIG. 2A to FIG. 2E as well as FIG. 3A to FIG. 3B Any combination of resonators in the configurations shown may be implemented.

[0104] In addition, similar to the above configuration, the series resonators of filters 800 and 800' are connected in series between the first port and the second port. Fig. 8A and Figure 8B In the embodiment, the first port and the second port are marked as "In" and "Out", respectively. In addition, the parallel resonators 820A, 820B, 820C, 820D of the filter 800 and the parallel resonators 820A', 820B', 820C', 820D' and 820E' of the filter 800' are connected to the ground point from the node between the adjacent series resonator pairs.

[0105] According to an exemplary aspect, Fig. 8A and Figure 8B800 and 800' are schematic circuit diagrams and layouts of filters 800 and 800', which can be implemented, for example, using XBARs (e.g., the general XBAR configuration 100 described above). It should be understood that the inclusion of the stated number of series resonators and parallel resonators is merely an example. Specifically, each of filters 800 and 800' can have more or fewer resonators in total, for example, more or less than four series resonators and more or less than four / five parallel resonators. In addition, in an exemplary aspect, each resonator can be split into two or more sub-resonators. For example, Fig. 8A The sub-resonator in is labeled "D", and Figure 8B The resonators in the sub-resonator can have similar configurations. Resonators that include a pair (or more pairs) of sub-resonators typically have the same configuration as each other, including the same aperture, approximately the same length, and the same stack. Splitting an acoustic resonator into multiple sub-resonators has the following main benefits: if each acoustic resonator has a single large diaphragm, the peak stress that would be generated is reduced.

[0106] In the exemplary filters 800 and 800', the series resonators 810A, 810B, 810C and 810D and 810A', 810B', 810C' and 810D', and the parallel resonators 820A, 820B, 820C and 820D and the parallel resonators 820A', 820B', 820C', 820D and 820E' of the filters 800 and 800' are respectively formed on at least one piezoelectric material layer (and in some cases a single piezoelectric material layer) bonded to a silicon substrate (not visible). As described above, each resonator includes a corresponding IDT (not shown).

[0107] In one aspect of the present disclosure, each output of the parallel resonators 820A, 820B, 820C, and 820D and 820A', 820B', 820C', 820D, and 820E' of the filters 800 and 800' is connected to its own corresponding ground bump. Fig. 8A As shown, a single inductor 860A is provided between each pair of sub-resonators of parallel resonators 820A and 820B and the ground point. This configuration is similar to the above description of Fig. 6A The configuration of filter 602 is described.

[0108] on the contrary, Figure 8B Filter 800' having an interleaved inductor configuration according to an exemplary aspect is shown. Specifically, filter 800' includes three inductors 860A', 860B', and 860C' each connected in series between a ground connection (e.g., "PKG GND") and one or more sub-resonators of one or more parallel resonators (e.g., resonators 820A' to 820E'). Note that as Figure 8B The inductance values ​​(H) noted in are provided for exemplary purposes only, and as will be appreciated by those skilled in the art, the values ​​of these inductors 860A', 860B', and 860C' may be configured based on a preferred optimization of the filter 800'. For example, to obtain T at higher frequencies z According to an exemplary aspect, the interleaved inductor configuration using inductors 860A', 860B', and 860C' (each coupled to one or more separate parallel resonators and ground) provides improved broadband suppression while reducing the flyback effect, as described above with respect to Figure 7B described.

[0109] As mentioned above, Fig. 6A , Fig. 7A , Fig. 8A and Figure 8B Each of the exemplary filters shown includes a plurality of resonators, wherein one or more of the individual resonators (e.g., parallel resonators and / or series resonators) may be divided into two or more separate sub-resonators. For example, filter 800' shows each of parallel resonators 820A' to 820E' formed by a pair of sub-resonators, each parallel resonator having a first sub-resonator coupled to a ground inductor and a second sub-resonator directly connected to a ground connection. That is, the aspect of splitting the resonator into sub-resonators allows each output of each respective resonator to be connected to a respective ground bump. In another aspect of the present disclosure, the split / separated resonator outputs additionally allow for the placement of staggered inductors, which provides correction for flyback and for T z Specific adjustments to the values, as described above.

[0110] Figure 8C The above description of the exemplary aspects is shown Fig. 8A and Figure 8B Exemplary graphs of filter responses for the depicted filters 800 and 800'. The frequency response of filter 800 is denoted by "◊" and the frequency response of filter 800' is denoted by "Δ". Figure 8C A graph showing the admittance (in dB) of filters 800 and 800 as a function of frequency is provided, the admittance being simulated using finite element method (FEM) simulation techniques.

[0111] As shown, each filter has a first frequency range (e.g., F as described above). Range1 ) has a similar filter response within the range of frequencies, but the filter 800′ has a similar filter response within the range of frequencies (eg, the second frequency F as described above). Range2 ) has an improved frequency in the higher frequency range, which solves the "flyback" or filter degradation in this higher frequency range, as described above. That is, in the higher frequency range FRange2 Within the first frequency range (F Range1 ) within the passband and may allow unwanted signals (e.g., signals that would otherwise be outside the passband) to pass impurely through the filter. Figure 8C It is shown that the interleaved inductor configuration of filter 800 ′ provides a dramatically improved frequency response with reduced bandwidth compared to filter 800 .

[0112] See also Figure 8B And as described herein, the filter 800' uses a split ladder architecture, wherein the series resonators 810A' to 810D' can be fabricated on a first chip and the parallel resonators 820A' to 820E' can be fabricated on a second chip. Then, for example, the first chip and the second chip can be mounted on a circuit board that provides interconnections between the first chip and the second chip, as described above with respect to Figure 5A described.

[0113] In addition, multiple parallel resonators 820A' to 820E' have four ground contact pads labeled "GND BUMPS". Inductors 860A', 860B', and 860C' represent conductor paths through corresponding ground contact pads to a system ground point (i.e., "PKGGND"). In an exemplary aspect, inductors 860A', 860B', and 860C' can be part of a second chip, but each inductor can include conductors on the second chip and outside the second chip. For example, according to various exemplary aspects, each inductor can include a conductor on the second chip, a conductive bump or ball connecting the second chip to a circuit board within a filter package, one or more conductors on the circuit board, and a conductive bump or ball connecting the package to a system ground plane.

[0114] In addition, filter 800' includes four instances of "partial inductive cross-coupling" using staggered grounded inductors described herein. Partial inductive cross-coupling occurs when at least one sub-resonator of the first parallel resonator (e.g., one of the sub-resonators of 820A') and at least one (but not all) sub-resonators of the second parallel resonator (e.g., one of the sub-resonators of 820B' and 820C') share the same ground contact pad, which helps to reduce the overall size of the filter components on each corresponding chip. In filter 800', one of the sub-resonators of each of parallel resonators 820A', 820B' and 820C' is connected to the system ground point via inductor 860A'. Another sub-resonator of each of parallel resonators 820A', 820B' and 820C' is directly connected to the system ground point without any inductor. It should be understood that this direct grounding will still pass through the circuit board (e.g., PCB), which may show some parasitic inductance. However, this impedance value will be significantly lower than the impedance value of each of the inductors 860A', 860B', and 860C', which are configured to have staggered inductance values ​​to eliminate or minimize the "flyback" effect at higher frequencies as described above.

[0115] In addition, one of the sub-resonators of each of the parallel resonators 820D' and 820E' is connected to the system ground via each inductor 860B' and 860C', respectively. As described above, each inductor has a different inductance (i.e., they are "interleaved"), with example inductances of 0.2nH, 0.35nH, and 0.15nH. As described above, these inductors can be set in the chip design to adjust the overall frequency response of the filter 800' according to the exemplary aspects.

[0116] Throughout this specification, the illustrated embodiments and examples should be considered as examples, rather than limitations of the disclosed or claimed devices and processes. Although many of the examples presented herein involve specific combinations of method actions or system elements, it should be understood that these actions and these elements can be combined in other ways to achieve the same goals. The actions, elements, and features discussed only in conjunction with one embodiment are not intended to exclude similar effects in other embodiments.

[0117] As used herein, "plurality" means two or more. As used herein, a "set" of items may include one or more such items. As used herein, whether in a written specification or in a claim, the terms "comprise", "include", "carry", "have", "contain", "involve", etc. should be understood as open-ended, i.e., meaning including but not limited to. Only the transition phrases "consisting of..." and "consisting essentially of..." are closed or semi-closed transition phrases for the claims, respectively. The use of sequential terms such as "first", "second", "third", etc. in the claims to modify the claim elements themselves does not imply any priority, priority or order of one claim element relative to another claim element or the temporal order of the actions of the execution method, but is only used as a label to distinguish a claim element with a specific name from another element with the same name (but using sequential terms) to distinguish the claim elements. As used herein, "and / or" means that the listed items are alternatives, but the alternatives also include any combination of the listed items.

Claims

1. A filter device, comprising: at least one series resonator connected between the pair of ports; a plurality of parallel resonators connected between a ground connection and a node between the at least one series resonator and one of the pair of ports; as well as a plurality of inductors, each of which is connected in series between the ground connection and the plurality of parallel resonators, wherein at least two of the plurality of inductors have interleaved inductance values ​​different from each other, and Wherein, each of the at least one series resonator and the plurality of parallel resonators comprises: substrate; a piezoelectric layer, attached to the substrate directly or via one or more intermediate layers, and An interdigital transducer (IDT) is on the surface of the piezoelectric layer and includes a plurality of staggered IDT fingers extending from a first busbar and a second busbar, respectively.

2. The filter device according to claim 1, wherein: The plurality of inductors are connected in parallel to each other.

3. The filter device according to claim 1, wherein: The at least one series resonator includes a plurality of series resonators connected in series between the pair of ports.

4. The filter device according to claim 3, wherein: Each of the plurality of parallel resonators is coupled to a node between a pair of adjacent resonators among the plurality of series resonators or a node between one of the plurality of series resonators and one of the pair of ports.

5. The filter device according to claim 1, wherein: The piezoelectric layer and IDT of each of the series resonator and the parallel resonator are configured such that a radio frequency signal applied to the IDT excites bulk shear acoustic waves in the piezoelectric layer, wherein the acoustic energy propagates in a direction substantially orthogonal to a surface of the piezoelectric layer and transverse to a direction of an electric field generated by the interlaced fingers of the IDT.

6. The filter device according to claim 1, wherein: The substrate of each of the respective resonators comprises a base and an intermediate layer, and the piezoelectric layer comprises a portion located above a cavity extending at least partially in the intermediate layer of the substrate.

7. The filter device according to claim 6, wherein: A surface of the piezoelectric layer on which the IDT is provided faces the cavity.

8. The filter device according to claim 1, wherein: At least one of the at least one series resonator and the plurality of parallel resonators further includes a Bragg reflector disposed between the substrate and the piezoelectric layer.

9. The filter device according to claim 1, wherein: Each of the plurality of parallel resonators includes at least two sub-resonators.

10. The filter device according to claim 9, wherein: A first sub-resonator of the at least two sub-resonators is coupled to an inductor of the plurality of inductors, and a second sub-resonator of the at least two sub-resonators is directly coupled to the ground connection.

11. A filter device, comprising: at least one series resonator connected between the pair of ports; a plurality of parallel resonators connected between a ground connection and a node between the at least one series resonator and one of the pair of ports; as well as a plurality of inductors, each of which is connected in series between the ground connection and the plurality of parallel resonators, wherein at least two of the plurality of inductors have interleaved inductance values ​​different from each other, wherein each of the at least one series resonator and the plurality of parallel resonators comprises a piezoelectric layer and an interdigital transducer (IDT) located on a surface of the piezoelectric layer, and The piezoelectric layer and IDT of each of the series resonator and the parallel resonator are configured so that a radio frequency signal applied to the IDT excites a bulk shear acoustic wave in the piezoelectric layer, wherein the acoustic energy propagates in a direction substantially orthogonal to a surface of the piezoelectric layer, and the direction is transverse to a direction of an electric field generated by the interlaced fingers of the IDT.

12. The filter device according to claim 11, wherein: Each of the at least one series resonator and the plurality of parallel resonators further includes a substrate, and the piezoelectric layer is attached to the substrate directly or via one or more intermediate layers.

13. The filter device according to claim 11, wherein: The plurality of inductors are connected in parallel to each other.

14. The filter device according to claim 11, in, The at least one series resonator includes a plurality of series resonators connected in series between the pair of ports, and Each of the plurality of parallel resonators is coupled to a node between adjacent resonators in the plurality of series resonators or a node between one of the series resonators and one of the pair of ports.

15. The filter device according to claim 12, wherein: The substrate of each of the respective resonators comprises a base and an intermediate layer, and the piezoelectric layer comprises a portion located in a cavity extending at least partially in the intermediate layer of the substrate.

16. The filter device according to claim 15, wherein: A surface of the piezoelectric layer on which the IDT is provided faces the cavity.

17. The filter device according to claim 12, wherein: At least one of the at least one series resonator and the plurality of parallel resonators further includes a Bragg reflector disposed between the substrate and the piezoelectric layer.

18. The filter device according to claim 11, wherein: Each of the plurality of parallel resonators includes at least two sub-resonators.

19. The filter device according to claim 18, wherein: A first sub-resonator of the at least two sub-resonators is coupled to an inductor of the plurality of inductors, and a second sub-resonator of the at least two sub-resonators is directly coupled to the ground connection.

20. A radio frequency module, comprising: A filter device having at least one series resonator connected between a pair of ports, a plurality of parallel resonators connected between a ground connection and a node between the at least one series resonator and one of the pair of ports, and a plurality of inductors respectively connected between the ground connection and the plurality of parallel resonators; as well as A radio frequency circuit is coupled to the filter device, the filter device and the radio frequency circuit are packaged in a common package, wherein at least two of the plurality of inductors have interleaved inductance values ​​different from each other, wherein each of the at least one series resonator and the plurality of parallel resonators comprises a piezoelectric layer and an interdigital transducer (IDT) located on a surface of the piezoelectric layer, and The piezoelectric layer and IDT of each of the individual resonators are configured such that a radio frequency signal applied to the IDT excites bulk shear acoustic waves in the piezoelectric layer, wherein the acoustic energy propagates in a direction substantially orthogonal to a surface of the piezoelectric layer and transverse to a direction of an electric field generated by the interlaced fingers of the IDT.

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