Laterally excited thin film bulk acoustic resonator with multi-tag interdigital transducers

Abstract

The invention provides an acoustic resonator device and an acoustic filter device. The acoustic wave resonator includes a piezoelectric plate having a front surface and a back surface. The back side is attached to a surface of the substrate, and a portion of the piezoelectric plate forms a diaphragm spanning a cavity in the substrate. A conductor pattern is formed on the front surface. The conductor pattern includes a multi-mark interdigital transducer (IDT) with fingers of the IDT on the septum.

Description

[0001] This application is a divisional application of Chinese invention patent application No. 202210120097.4, filed on February 7, 2022, entitled "Transversely Excited Thin Film Bulk Acoustic Resonator with Multi-Marked Interdigital Transducers". Technical Field

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

[0003] Radio frequency (RF) filters are two-ended devices configured to allow some frequencies to pass while blocking others. "Passing" means transmitting with relatively low signal loss, while "blocking" means blocking or essentially attenuating the signal. The range of frequencies a filter can pass through is called its "passband." The range of frequencies blocked by such a filter is called its "stopband." A typical RF filter has at least one passband and at least one stopband. The specific requirements for the passband or stopband depend on the application. For example, a "passband" can be defined as a frequency range where the filter's insertion loss is better than defined values ​​such as 1 dB, 2 dB, or 3 dB. A "stopband" can be defined as a frequency range where the filter's rejection is greater than defined values, such as 20 dB, 30 dB, 40 dB, or greater, depending on the application.

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

[0005] RF filters typically require numerous design trade-offs to achieve the optimal balance between performance parameters such as insertion loss, rejection, isolation, power handling, linearity, size, and cost for each specific application. Specific design and manufacturing approaches and enhancements can simultaneously benefit one or more of these requirements.

[0006] Enhancements to the performance of RF filters in wireless systems can have a wide-ranging impact on system performance. Improvements to RF filters can lead to improvements such as larger cell size, longer battery life, higher data rates, greater network capacity, lower cost, enhanced security, and higher reliability. These improvements can be implemented individually or in combination at various levels of the wireless system, such as at the RF module, RF transceiver, mobile or fixed subsystem, or network level.

[0007] High-performance RF filters used in current communication systems typically incorporate acoustic resonators, including surface acoustic wave (SAW) resonators, bulk acoustic wave (BAW) resonators, thin-film bulk acoustic wave (FBAR) resonators, and other types of acoustic resonators. However, these existing technologies are not suitable for use at higher frequencies and bandwidths, which future communication networks require.

[0008] To obtain wider communication channel bandwidth, higher frequency communication bands are necessary. 3GPP (3rd Generation Partnership Project) has standardized radio access technologies for mobile phone networks. The 5G NR (New Radio) standard defines radio access technologies for fifth-generation mobile networks. The 5G NR standard defines several new communication bands. Among these new bands are n77 and n79, where n77 uses a frequency range of 3300 MHz to 4200 MHz, and n79 uses a frequency range of 4400 MHz to 5000 MHz. Both bands n77 and n79 use Time Division Duplex (TDD), therefore, communication devices operating in bands n77 and / or n79 will use the same frequencies for uplink and downlink transmissions. Bandpass filters in the n77 and n79 bands must be able to handle the transmit power of the communication devices. High frequencies and wide bandwidths are also required in the 5GHz and 6GHz radio bands. The 5G NR standard also defines millimeter wave communication bands between 24.25 GHz and 40 GHz.

[0009] The transversely excited film bulk acoustic resonator (XBAR) is an acoustic resonator structure used in microwave filters. Such an XBAR is described in U.S. Patent 10,491,291, entitled "TRANSVERSELY EXCITED FILM BULK ACOUSTIC RESONATOR". The XBAR resonator includes an interdigital transducer (IDT) formed on a thin floating layer or diaphragm of a single-crystal piezoelectric material. The IDT includes a first set of parallel fingers extending from a first busbar and a second set of parallel fingers extending from a second busbar. The first and second sets of parallel fingers are interleaved. A microwave signal applied to the IDT excites a sheared master acoustic wave in the piezoelectric diaphragm. The XBAR resonator provides high electromechanical coupling and high-frequency capability. XBAR resonators can be used in a variety of RF filters, including band-stop filters, band-pass filters, duplexers, and multiplexers. XBARs are particularly well-suited for use in filters in communication bands above 3 GHz. Matrix XBAR filters are also suitable for frequencies between 1 GHz and 3 GHz. Summary of the Invention

[0010] The present invention discloses an acoustic resonator comprising: a piezoelectric plate having a front side and a back side, the back side being attached to a surface of a substrate, a portion of the piezoelectric plate forming a diaphragm spanning a corresponding cavity in the substrate; and a conductor pattern located on the front side, the conductor pattern including a multi-marked interdigital transducer (IDT) and fingers of the IDT on the diaphragm.

[0011] The main shear acoustic mode is excited by the IDT in the piezoelectric plate.

[0012] The shearing master acoustic mode is excited in response to the radio frequency signal applied to the IDT.

[0013] The markings of the IDT vary along the length of the IDT.

[0014] The IDT is divided into two or more parts along its length, each part having a corresponding label that is different from the labels of each of the other parts.

[0015] The markings of the IDT change continuously along the length of the IDT.

[0016] The spacing of the IDT is constant throughout the entire IDT.

[0017] The spacing of the IDT varies along the length of the IDT.

[0018] The IDT is divided into two or more parts along its length, each part having a corresponding spacing that is different from the spacing of each other part.

[0019] The spacing of the IDT varies continuously along the length of the IDT.

[0020] The present invention also discloses a filter device comprising: a piezoelectric plate having a front side and a back side, the back side being attached to a surface of a substrate, a portion of the piezoelectric plate forming a plurality of diaphragms spanning corresponding cavities in the substrate; and a conductor pattern located on the front side, the conductor pattern including a plurality of interdigital transducers (IDTs), the fingers of the IDTs being on a corresponding diaphragm of the plurality of diaphragms, wherein the first IDT from the plurality of IDTs is a multi-marker IDT.

[0021] The main shear acoustic mode is excited by the corresponding IDT among the plurality of IDTs in the piezoelectric plate.

[0022] The shearing master mode is excited in response to the radio frequency signals applied to each IDT.

[0023] Among them, all multiple IDTs are multi-label IDTs.

[0024] The first IDT is divided into two or more parts along its length, each part having a corresponding label that is different from the labels of each of the other parts.

[0025] The markings of the first IDT change continuously along the length of the first IDT.

[0026] The spacing of the first IDT is constant throughout the first IDT.

[0027] The spacing of the first IDT varies along the length of the first IDT.

[0028] The first IDT is divided into two or more parts along its length, each part having a corresponding spacing that is different from the spacing of each other part.

[0029] The spacing of the first IDT varies continuously along the length of the first IDT. Attached Figure Description

[0030] Figure 1 Includes a schematic plan view, two schematic cross-sectional views, and a detailed view of the transversely excited membrane acoustic resonator (XBAR).

[0031] Figure 2 This is an alternative schematic cross-sectional view of XBAR.

[0032] Figure 3 This is a diagram illustrating the shearing of horizontal acoustic modalities in XBAR.

[0033] Figure 4 This is a plan view of a multi-marker interdigital transducer (IDT).

[0034] Figure 5 It is another planar diagram of a multi-labeled IDT.

[0035] Figure 6 This is a graph showing how the markers of a regular IDT and another multi-marker IDT vary along the length of the IDT.

[0036] Figure 7 It is the amplitude of the input transfer function as the frequency of the XBAR filter with a conventional IDT and the XBAR multi-label IDT varies.

[0037] Figure 8 yes Figure 7 The magnified portion of the image.

[0038] Figure 9 It is a planar diagram of a multi-marker, multi-spacing IDT.

[0039] Figure 10 It is another planar diagram of a multi-marker, multi-spacing IDT.

[0040] Throughout the specification, elements appearing in the accompanying drawings are assigned three- or four-digit reference numerals, where the two least significant digits are unique to that element, and one or two most significant digits are the drawing number in which the element is first shown. Elements not described in conjunction with the accompanying drawings may be assumed to have the same characteristics and functions as previously described elements with the same reference numerals. Detailed Implementation

[0041] Component Description

[0042] Figure 1 A simplified schematic top view, orthogonal cross-sectional view, and detailed cross-sectional view of a laterally excited thin-film bulk acoustic resonator (XBAR) 100 are shown. XBAR resonators, such as resonator 100, can be used in a variety of RF filters, including band-stop filters, band-pass filters, duplexers, and multiplexers. XBARs are particularly suitable for filters in communication frequency bands above 3 GHz.

[0043] XBAR 100 consists of a thin-film conductor pattern formed on the surface of a piezoelectric plate 110, which has a front side 112 and a back side 114 that are parallel to each other. The piezoelectric plate is a thin single-crystal layer made of a piezoelectric material, such as lithium niobate, lithium tantalate, lanthanum gallium silicate, gallium nitride, or aluminum nitride. The piezoelectric plate is cut such that the orientations of the X, Y, and Z crystal axes relative to the front and back sides are known and consistent. In the example presented in this patent, the piezoelectric plate may be Z-cut, that is, the Z axis is perpendicular to the front and back sides 112, 114. However, XBAR can be fabricated on piezoelectric plates with other crystal orientations.

[0044] The back surface 114 of the piezoelectric plate 110 is attached to the surface of the substrate 120, except for a portion of the piezoelectric plate 110 that is not attached to the surface of the substrate 120. This portion of the piezoelectric plate 110 forms a diaphragm 115, which spans a cavity 140 formed in the substrate. The portion of the piezoelectric plate 110 that spans the cavity is referred to herein as the "diaphragm" 115 because this portion is physically similar to the diaphragm of a microphone. Figure 1 As shown, the diaphragm 115 is adjacent to the remainder of the piezoelectric plate 110 around the entire periphery 145 of the cavity 140. In this case, "adjacent" means "continuous connection without any other items in between". In other configurations, the diaphragm 115 may be adjacent to the piezoelectric plate around at least 50% of the periphery 145 of the cavity 140.

[0045] Substrate 120 provides mechanical support for piezoelectric plate 110. Substrate 120 can be, for example, silicon, sapphire, quartz, or some other material, or a combination of these materials. The back surface 114 of piezoelectric plate 110 can be attached to substrate 120 using wafer bonding processes. Alternatively, piezoelectric plate 110 can be grown on substrate 120 or attached to the substrate in some other way. Piezoelectric plate 110 can be directly attached to the substrate, or it can be attached via one or more intermediate material layers (not on the substrate). Figure 1 (As shown in the figure) is attached to substrate 120.

[0046] The conventional meaning of "cavity" is "empty space within a solid". Cavity 140 can be a hole that passes completely through substrate 120 (as shown in cross sections AA and BB), or it can be a groove in substrate 120 below diaphragm 115. For example, cavity 140 can be formed by selectively etching substrate 120 before or after attaching piezoelectric plate 110 to substrate 120.

[0047] The conductor pattern of XBAR100 includes an interdigital transducer (IDT) 130. IDT 130 includes a first plurality of parallel fingers, such as fingers 136, and a second plurality of fingers, wherein the first plurality of parallel fingers extend from a first busbar 132, and the second plurality of fingers extend from a second busbar 134. The first and second plurality of parallel fingers are staggered. The staggered fingers overlap by a distance AP, which is commonly referred to as the “orifice” of the IDT. The center-to-center distance L between the outermost fingers of IDT 130 is the “length” of the IDT.

[0048] The first and second buses 132 and 134 serve as terminals of the XBAR 100. An radio frequency or microwave signal applied between the two buses 132 and 134 of the IDT 130 excites the primary acoustic mode within the piezoelectric plate 110. As discussed in detail below, the primary acoustic mode is a bulk shear mode, in which acoustic energy propagates in a direction substantially perpendicular to the surface of the piezoelectric plate 110, which is also perpendicular or transverse to the direction of the electric field generated by the IDT fingers. Therefore, the XBAR is considered a transversely excited thin-film bulk wave resonator.

[0049] IDT 130 is placed on piezoelectric plate 110 such that at least the fingers of IDT 130 are positioned on diaphragm 115 of the piezoelectric plate, which spans or hangs over cavity 140. Figure 1 As shown, the cavity 140 is rectangular, and the size of the rectangle is greater than the length L of the orifice AP and IDT 130. The cavity of the XBAR can have different shapes, such as regular or irregular polygons. The cavity of the XBAR can have more or fewer four sides, which can be straight or curved.

[0050] To facilitate Figure 1As shown, the geometric spacing and width of the IDT fingers are significantly enlarged relative to the length (dimension L) and orifice (dimension AP) of the XBAR. A typical XBAR in an IDT 110 has more than ten parallel fingers. A single XBAR in an IDT 110 may have hundreds of parallel fingers. Similarly, in the cross-sectional view, the thickness of the fingers is significantly enlarged.

[0051] Referring now to the detailed view, a front dielectric layer 150 may optionally be formed on the front side of the piezoelectric plate 110. By definition, the "front side" of XBAR refers to the side facing away from the substrate. The front dielectric layer 150 may be formed only between the IDT fingers (e.g., IDT fingers 138b), or it may be deposited as a capping layer such that the dielectric layer is formed between and on the IDT fingers (e.g., IDT fingers 138a). The front dielectric layer 150 may be a non-piezoelectric dielectric material, such as silicon dioxide or silicon nitride. The thickness of the front dielectric layer is typically less than or equal to the thickness of the piezoelectric plate. The front dielectric layer 150 may be formed from multiple layers of two or more materials.

[0052] IDT fingers 138a and 138b may be made of aluminum, aluminum alloy, copper, copper alloy, beryllium, gold, tungsten, molybdenum, chromium, titanium, or certain other conductive materials. If the IDT fingers are made of aluminum or an alloy containing at least 50% aluminum, the IDT fingers are considered "substantially aluminum." If the IDT fingers are made of copper or an alloy containing at least 50% copper, the IDT fingers are considered "substantially copper." A thin layer (relative to the total thickness of the conductor) of other metals (e.g., chromium or titanium) or other metal layers may be formed below and / or above the fingers as layers within the fingers to improve adhesion between the fingers and the piezoelectric plate 110 and / or passivate or encapsulate the fingers and / or improve power handling. The IDT busbars 132 and 134 may be made of the same or different materials as the fingers.

[0053] Dimension p is the center-to-center spacing or "pitch" of the IDT fingers, which can be referred to as the IDT pitch and / or XBAR pitch. Dimension w is the width or "mark" of the IDT fingers.

[0054] Figure 2A detailed schematic cross-sectional view of a solid-state assembled XBAR (SM XBAR) 200 is shown. Patent US 10,601,392 first described the SM XBAR. The SM XBAR 200 includes a piezoelectric plate 110 and an IDT (wherein only fingers 230 and 235 of the IDT are visible). The piezoelectric layer 110 has parallel front and back sides 112, 114. Dimension tp is the thickness of the piezoelectric plate 110. The width (or marking) of the IDT fingers 230, 235 is dimension m, the thickness of the IDT fingers is dimension tm, and the spacing of the IDTs is dimension p.

[0055] and Figure 1 Unlike the XBAR device shown, the IDT of the SM XBAR is not formed on the diaphragm spanning the cavity in the substrate. Figure 1 (120 in the original text). Instead, the acoustic Bragg reflector 240 is located between the surface 222 of the substrate 220 and the back surface 114 of the piezoelectric plate 110. The acoustic Bragg reflector 240 is disposed between the surface 222 of the substrate 220 and the back surface 114 of the piezoelectric plate 110 and is mechanically attached to the surface 222 of the substrate 220 and the back surface 114 of the piezoelectric plate 110. In some cases, a thin layer of additional material 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 114 of the piezoelectric plate 110. Such an additional material layer may be present, for example, to facilitate bonding of the piezoelectric plate 110, the acoustic Bragg reflector 240, and the substrate 220.

[0056] The acoustic Bragg reflector 240 comprises multiple dielectric layers alternating between materials with high acoustic impedance and materials with low acoustic impedance. "High" and "low" are relative terms. For each layer, the comparison is made against adjacent layers. The acoustic impedance of each "high" acoustic impedance layer is higher than that of the two adjacent low acoustic impedance layers. The acoustic impedance of each "low" acoustic impedance layer is lower than that of the two adjacent high acoustic impedance layers. As will be discussed later, the dominant acoustic mode in the XBAR piezoelectric plate is a shear volume wave. The thickness of each layer of the acoustic Bragg reflector 240 is equal to or approximately one-quarter the wavelength of the shear volume wave, which has the same polarization as the dominant acoustic mode at or near the resonant frequency of the SM XBAR 200. Dielectric materials with lower acoustic impedance include silicon dioxide, carbon-containing silicon oxide, and certain plastics, such as cross-linked polyphenylene polymers. Materials with higher acoustic impedance include hafnium dioxide, silicon nitride, aluminum nitride, silicon carbide, and diamond. All high acoustic impedance layers of the acoustic Bragg reflector 240 are not necessarily made of the same material, and all low acoustic impedance layers are not necessarily made of the same material. Figure 2 In the example, the acoustic Bragg reflector 240 has a total of six layers. An acoustic Bragg reflector can have more or fewer than six layers.

[0057] like Figure 2 As shown, IDT fingers 230 and 235 have rectangular cross-sections. IDT fingers 230 and 235 can have other cross-sections, such as trapezoidal, T-shaped, or stepped. IDT fingers 230 and 235 are shown as a single-layer structure that can be aluminum or some other metal. IDT fingers can include multiple layers of materials, which can be selected to have different acoustic losses and / or different acoustic impedances. When multiple material layers are used, the cross-sectional shapes of the layers can be different. Furthermore, a thin adhesive layer of another material, such as titanium or chromium, can be formed between the IDT fingers 230 and 235 and the piezoelectric plate 110. Although Figure 2 Not shown, but some or all of the IDT fingers may be provided in grooves or slots that extend partially or completely through the piezoelectric plate 110.

[0058] Figure 3 This is a diagrammatic explanation of the main vocalist of interest in XBAR. Figure 3 A small portion of the XBAR 300 is shown, comprising a piezoelectric plate 310 and three staggered IDT fingers 330, with electrodes of the IDT fingers alternating between the fingers. An RF voltage is applied to the staggered fingers 330. This voltage generates a time-varying electric field between the fingers. The direction of the electric field is primarily transverse, or parallel to the surface of the piezoelectric plate 310, as indicated by the arrow labeled “Electric Field.” Due to the high dielectric constant of the piezoelectric plate, the RF energy is highly concentrated within the plate relative to air. The transverse electric field introduces shear deformation, which is strongly coupled to the shear master acoustic modes in the piezoelectric plate 310 at the resonant frequency defined by the acoustic cavity formed by the volume between the two surfaces of the piezoelectric plate. In this context, “shear deformation” is defined as the deformation in a material where parallel planes remain primarily parallel and are kept constantly separated when translated relative to each other (within their respective planes). A “shear acoustic mode” is defined as an acoustic vibration mode in a medium that causes shear deformation of the medium. The shear deformation in XBAR 300 is represented by curve 360, with adjacent small arrows schematically indicating the direction and relative amplitude of atomic motion at the resonant frequency. For ease of observation, the extent of atomic motion, and the thickness of the piezoelectric plate 310, have been greatly exaggerated. Although the atomic motion is primarily transverse (i.e., as shown in the image),... Figure 3 (as shown in the horizontal direction), but as indicated by arrow 365, the direction of acoustic energy flow of the excited master acoustic mode is basically orthogonal to the surface of the piezoelectric plate.

[0059] Shear wave resonators can achieve performance superior to current state-of-the-art thin-film bulk acoustic resonators (FBARs) and solid-mount resonators (SMR BAWs) devices, where an electric field is applied along the thickness direction. In such devices, acoustic modes are compressed along the direction of atomic motion and acoustic energy flow in the thickness direction. Furthermore, shear wave XBAR resonators can exhibit piezoelectric coupling that is significantly higher (>20%) compared to other acoustic resonators. This high piezoelectric coupling enables the design and implementation of microwave and millimeter-wave filters with considerable bandwidth.

[0060] The primary acoustic mode of an XBAR is essentially volumetric, which may result in a weak frequency dependence on the markers and spacing. Therefore, the chirping (or variation) of the markers or the markers and spacing in the IDT of an XBAR may potentially suppress unwanted stray modes, such as metallic and propagating modes, that depend on the markers and / or spacing, with only a slight widening of the primary mode resonance.

[0061] Figure 4 This is a plan view of an exemplary multi-marker IDT 400. A "multi-marker IDT" is an IDT where the marks of the IDT fingers vary along the length of the IDT. At any given point along the length, the marks may not vary across the aperture of the IDT. Furthermore, the spacing may remain constant throughout the entire IDT. The multi-marker IDT 400 can be an XBAR, for example... Figure 1 Part of the XBAR 100.

[0062] The multi-marked IDT 400 includes a first busbar 432 and a second busbar 434, and a plurality of interleaved fingers, such as fingers 436. The interleaved fingers extend alternately from the first and second busbars 432 and 434. The marked IDT 400 is divided into three parts along the length L of the IDT, designated as part A, part B, and part C. Each of parts A, B, and C includes 20 fingers, for a total of 60 fingers in the multi-marked IDT 400. The use of three parts and 60 fingers is exemplary. An IDT may have more or less than 60 total fingers. An IDT may be divided into two or more parts along its length, each part including a plurality of adjacent fingers. The total number of fingers may be divided substantially equally between the two or more parts. In this case, "substantially" means "as close as possible". For example, an IDT with 100 fingers divided into 3 parts, with each part containing 33, 34, and 33 fingers, is considered to be roughly equal. The total number of fingers may be unequally divided among two or more parts.

[0063] In this example, the fingers in section B have a marker m, which is the nominal marker of the IDT. The fingers in section A have a marker m(1 – δm), and the fingers in section C have a marker m(1 + δm). δm is greater than 0 and less than or equal to 0.05. δm can typically be less than 0.01. δm can be selected during filter design to most effectively reduce spurious modes. At any point along the 400-degree length L of the IDT, the marker is constant on aperture A. The spacing of the IDT fingers is constant and the same in all sections. When the IDT is divided into two or more sections, the maximum marker may be m(1 + δm), and the minimum marker may be m(1 – δm).

[0064] In the example multi-label IDT 400, the labels monotonically increase from left to right (as shown in the figure). This is not necessarily the case in all multi-label IDTs. The parts of a multi-label IDT can be arranged in other orders. Furthermore, in multi-label IDT 400, the label variation between adjacent parts is constant. This is also not necessarily the case in all multi-label IDTs. The label variation between adjacent parts can be the same or different.

[0065] Figure 5 This is a plan view of another multi-marker IDT 500 with continuously varying markings. IDT 500 includes a first busbar 532 and a second busbar 534, and a plurality of interlaced fingers, such as fingers 536. The interlaced fingers extend alternately from the first and second busbars 532, 534. Instead of dividing the IDT 500 into multiple sections, the fingers 536 have continuously varying markings along their length L. IDT 500 has 60 fingers, which is exemplary. The total number of fingers in an IDT may be more or less than 60. The multi-marker IDT 500 can be an XBAR, for example... Figure 1 Part of the XBAR 100.

[0066] like Figure 5 As shown, the marker at the left edge of the IDT 500 is m(1 – δm), and the marker at the right edge is m(1 + δm). The marker varies continuously between these two extremes. The variation in the marker is typically, but not necessarily, a linear function of the position along the IDT length L. δm is greater than 0 and less than or equal to 0.05, typically less than 0.01. δm can be selected during filter design to most effectively reduce spurious modes. At any point along the length of the IDT 500, the marker is constant along the aperture A. The spacing of the IDT fingers is constant throughout the IDT.

[0067] Figure 6Illustration 600 shows the markings along the length of an IDT as a function of position for a conventional IDT and another exemplary multi-marker IDT. Dashed line 610 shows the markings along the length of an IDT as a function of position for a conventional IDT without chirp. Solid line 620 shows the markings along the length of an IDT with chirped markings as a function of position for a multi-marker IDT. In this example, a linear gradient is applied to the markings of the multi-marker IDT, resulting in a triangular profile for the chirp. The markings of each consecutive finger have a difference of 0.5 nm, such that the marking of the widest finger is 20 nm wider than the narrowest finger. Dashed line 630 shows the markings along the length of an IDT with chirped markings, where a linear gradient is applied to the markings of the multi-marker IDT. Other exemplary IDTs may have other differences in the markings between consecutive fingers, for example, differences ranging from 0.1 nm to 0.9 nm, and the difference between the widest and narrowest fingers may be other values, for example, ranging from 1 nm to 100 nm.

[0068] Figure 7 This is a graph 700 showing the magnitude of the input / output transfer function S2,1 for two bandpass filters implemented using XBAR devices. The S2,1 data was determined by simulating the two filters using the finite element method. The dashed line 710 is a graph of S2,1 for the first filter using an XBAR with a conventional IDT. The solid line 720 is a graph of S2,1 for the second bandpass filter with a multi-marked IDT, but it could also be the same as the first bandpass filter. A comparison of curves 710 and 720 shows that the passbands of the two filters are very similar. Compared to the first filter, the second filter with the multi-marked IDT exhibits a reduced peak admittance for spurious modes.

[0069] Slight changes to the IDT label in XBAR can lead to the destruction or destructive interference of spurious modes, while the effect on the shearing master mode is negligible. This effect is... Figure 8 As shown in the figure, Figure 8 yes Figure 7 A magnified view of a portion of the graph. Figure 8 In the diagram, dashed line 810 is a graph of S21 versus frequency for a filter with a conventional IDT. Solid line 820 is a graph of S21 versus frequency for a filter with a multi-marked IDT. Compared to a filter with a conventional IDT, a filter with a multi-marked IDT reduces spurious modes within the N79 passband, thus reducing losses. The chirp marking of the multi-marked IDT has a negligible effect on the resonant and anti-resonant frequencies of the XBAR's cut master mode.

[0070] Used to generate Figure 7 and Figure 8The filters shown in the data comprise four series resonators and four parallel resonators in a ladder-shaped filter circuit. All resonators are XBARs. These filters are exemplary. A filter may have fewer or more resonators, and more or fewer series and parallel resonators. A multi-marked IDT may be divided into two or more parts, or it may be continuous. The number of parts may vary for all resonators in the filter, and a filter may include both partial and continuous multi-marked IDTs. The value of δm may vary for some or all resonators. Filters may contain a combination of resonators with uniform marking and multi-marked resonators.

[0071] Figure 9 This is a plan view of an exemplary multi-spacing, multi-marker IDT 900. A “multi-spacing IDT” is an IDT where the spacing of the IDT fingers varies along the length of the IDT. At any given point along the length, the spacing may not vary along the aperture of the IDT. Furthermore, as described above, the marks can also vary along the length of the IDT, making the IDT a multi-marker, multi-spacing IDT. The multi-spacing, multi-marker IDT 900 can be an XBAR, for example... Figure 1 Part of the XBAR 100.

[0072] The multi-spacing, multi-marker IDT 900 includes a first busbar 932, a second busbar 934, and a plurality of interleaved fingers, such as fingers 936. The interleaved fingers extend alternately from the first and second busbars 932 and 934. (See above) Figure 4 Similar to the description, a multi-spacing multi-marker IDT 900 can be divided into three parts along the length L of the IDT: part A, part B, and part C. Each of parts A, B, and C includes 20 fingers, for a total of 60 fingers in the multi-spacing multi-marker IDT 900. The use of three parts and 60 fingers is exemplary. The total number of fingers in an IDT may be more or less than 60. An IDT can be divided into two or more parts along its length, each part including multiple adjacent fingers. The total number of fingers can be divided substantially equally between the two or more parts. In this case, "substantially" means "as close as possible." For example, an IDT with 100 fingers divided into three parts of 33, 34, and 33 fingers is considered substantially equally divided. The total number of fingers can be unequally divided between two or more parts. The division can be the same as or different from the division of the mark chirp.

[0073] In this example, the fingers in section B have a spacing p, which is the nominal pitch of the IDT. The spacing of the fingers in section A is p(1 – δp), and the spacing of the fingers in section C is p(1 + δp). δp is greater than 0 and less than or equal to 0.05. δp can typically be less than 0.01. δp can be selected during filter design to most effectively reduce spurious modes. At any point along the length L of the IDT900, the spacing across aperture A is constant. The markings of the IDT fingers also vary by section, similar to... Figure 4 The IDT 400 shown is a variation by section. The markings may vary according to the same spacing for the same section or according to the spacing for different sections. Alternatively, with... Figure 5 The continuous change of the marker shown is similar; the marker can also change continuously.

[0074] Figure 10 This is a plan view of another exemplary multi-spacing multi-marker IDT 1000. The multi-spacing multi-marker IDT 900 can be an XBAR, for example... Figure 1 This is part of the XBAR 100. The multi-spacing multi-marker IDT 1000 includes a first busbar 1032 and a second busbar 1034, and a plurality of interlaced fingers, such as fingers 1036. The interlaced fingers extend alternately from the first and second busbars 1032, 1034. In this example, the markings change continuously, similar to... Figure 5 The markings shown change continuously. The spacing, similar to the markings, also changes continuously. For example... Figure 10 As shown, both the markers and spacing increase continuously from left to right, as illustrated. Alternatively, either the markers or spacing can increase continuously from left to right, while the other of the markers or spacing decreases continuously from left to right.

[0075] In other examples, the spacing of the IDT can vary continuously, similar to... Figure 5 The markings shown are continuously changing. The spacing may change with the markings, or it may change at a different rate. Both the spacing and the markings can change continuously. The spacing and / or the markings can change between multiple maximum and minimum values ​​along the length of the IDT. The markings can change in sections while the spacing changes continuously, or the spacing can change in sections while the markings change continuously. The markings can increase in one direction (continuously or piecewise) along the length of the IDT, while the spacing decreases in the same direction (continuously or piecewise). The changes in markings and spacing can be optimized relative to each other; the changes in markings and spacing between one resonator and another can be different, thereby achieving maximum suppression of parasitic modes for optimal filter performance.

[0076] Conclusion

[0077] Throughout this specification, the embodiments and examples shown should be considered as examples and not as limitations on the disclosed or claimed devices and processes. While many of the examples provided herein relate to specific combinations of method actions or system elements, it should be understood that those actions and elements can be combined in other ways to achieve the same objective. Regarding the flowcharts, additional or fewer steps may be taken, and the steps shown may be combined or further refined to implement the methods described herein. Actions, elements, and features discussed in connection with only one embodiment are not intended to exclude their similarity in other embodiments.

[0078] As used herein, “multiple” means two or more. As used herein, a “group” of items may include one or more such items. As used herein, whether in the written description or in the claims, the terms “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” etc., shall be understood as open-ended, i.e., referring to including but not limited to. Only the transitional phrases “consisting of…” and “substantially consisting of…” are closed or semi-closed transitional phrases relative to the claims. Ordinal numbers used in the claims, such as “first,” “second,” “third,” etc., are used to modify claim elements. This does not in itself indicate the priority, order, or sequence of action of one claim element over another, but is merely used to distinguish one claim element with the same name from another element with the same name (but with ordinal numbers), thereby differentiating claim elements. As used herein, “and / or” means that the listed items are alternatives, but alternatives also include any combination of the listed items.

Claims

1. An acoustic resonator, comprising: A piezoelectric layer having a front side and a back side, a portion of the back side being attached to a substrate directly or via one or more intermediate layers, the piezoelectric layer including a diaphragm spanning a cavity; and A conductor pattern, located on the front side, includes a multi-marker, multi-spacing interdigitated transducer (IDT), the IDT having a plurality of interlaced fingers and a length between the outermost fingers of the interlaced fingers. The IDT is divided into at least three parts along its length, wherein each of the first, second, and third parts has multiple pairs of fingers among the plurality of interlaced fingers. The first portion is closer to the first outermost finger of the IDT, the third portion is closer to the last outermost finger of the IDT, and the second portion is located between the first portion and the third portion. In each of the first, second, and third parts, the markings and spacing of the interlaced fingers are constant in each part. The spacing within each section differs from the corresponding spacing in other sections. The spacing in each of the at least three portions is measured as the center-to-center interval between adjacent fingers extending from different generatrices in the respective portion. The acoustic resonator is either a series resonator or a parallel resonator with a passband trapezoidal filter, and... The effect of the spacing variation between the at least three parts on the resonant frequencies of the main shear modes of all the at least three parts of the acoustic resonator of the trapezoidal filter is less than the effect of the spacing variation on the in-band stray modes of the filter other than the main shear modes of all the at least three parts in the passband.

2. The acoustic resonator according to claim 1, wherein, The primary shear mode is excited in response to a radio frequency signal applied to the IDT.

3. The acoustic resonator according to claim 1, wherein, The first part is marked with interlaced fingers as m(1–δ) m ), The interlaced finger-like markings in the third part are m(1+δ) m ),and δ m Greater than 0 and less than or equal to 0.

05.

4. The acoustic resonator according to claim 1, wherein, The spacing p between the interlaced fingers in the second part is the nominal spacing of the IDT. The spacing between the interlaced fingers in the first part is p(1–δ) p ), The spacing between the interlaced fingers in the third part is p(1+δ) p ),and δ p Greater than 0 and less than or equal to 0.

05.

5. The acoustic resonator according to claim 1, wherein, The piezoelectric layer and the IDT are configured such that a radio frequency signal applied to the IDT excites a primary shear acoustic mode in the diaphragm, the primary shear acoustic mode being a bulk shear mode, wherein acoustic energy propagates in a direction substantially perpendicular to the front and back surfaces of the piezoelectric layer, the front and back surfaces of the piezoelectric layer being transverse to the direction of the electric field generated by the IDT.

6. The acoustic resonator according to claim 1, wherein, "Small impact" means that the change in the amplitude of the main shear mode is smaller than the change in the amplitude of the stray mode.

7. The acoustic resonator according to claim 1, wherein, The trapezoidal filter includes at least one additional acoustic resonator having an IDT divided into at least three sections along its length, each section having a plurality of interlaced fingers, wherein the markings of the interlaced fingers are constant in each of the at least three sections of the additional acoustic resonator and across each of the at least three sections.

8. A filter device having a passband, the filter device comprising: A piezoelectric layer having a front side and a back side, a portion of the back side being attached to a substrate directly or via one or more intermediate layers, the piezoelectric layer comprising a plurality of diaphragms spanning a respective cavity; and A conductor pattern is located on the front side, the conductor pattern comprising multiple interdigital transducers (IDTs) of multiple bulk acoustic resonators, wherein the interlaced fingers of the multiple IDTs are located on corresponding diaphragms of the multiple diaphragms. Wherein, each of the first IDT and the second IDT from the plurality of IDTs is a multi-marker multi-spacing IDT, having the length between the outermost fingers of the interlaced fingers of the corresponding IDT. in: The first IDT and the second IDT are divided into at least three parts along the length direction, wherein each of the first, second and third parts has multiple pairs of fingers among the plurality of interlaced fingers. The first portion is closer to the first outermost finger of the corresponding IDT, the third portion is closer to the last outermost finger of the corresponding IDT, and the second portion is located between the first portion and the third portion. Wherein, the markings and spacing of the interlaced fingers in each of the first, second, and third portions are constant in each portion of the corresponding IDT. The spacing between each part of the first IDT and the second IDT is different from the corresponding spacing between the other parts. The spacing in each of the at least three portions of the first IDT and the second IDT is measured as the center-to-center spacing between adjacent fingers extending from different busbars in the respective portion, and The effect of the spacing variation between the at least three parts on the resonant frequencies of the main shear modes of all the at least three parts of the corresponding bulk acoustic filter is less than the effect of the spacing variation on the in-band stray modes in the passband of the filter other than the main shear modes of all the at least three parts.

9. The filter device according to claim 8, wherein, The corresponding primary shear mode is excited by the corresponding IDT located in the corresponding diaphragm of the plurality of IDTs, and each primary shear mode is excited in response to the radio frequency signal applied to the corresponding IDT.

10. The filter device according to claim 8, wherein, In addition to the first IDT and the second IDT, one or more of the plurality of IDTs are multi-marker multi-spacing IDTs.

11. The filter device according to claim 8, wherein, For each of the first IDT and the second IDT: The first part is marked with interlaced fingers as m(1–δ) m ), The interlaced finger-like markings in the third part are m(1+δ) m ),and δ m Greater than 0 and less than or equal to 0.

05.

12. The filter device according to claim 8, wherein, For each of the first IDT and the second IDT: The spacing p between the interlaced fingers in the second part is the nominal spacing of the IDT. The spacing between the interlaced fingers in the first part is p(1–δ) p ), The spacing between the interlaced fingers in the third part is p(1+δ) p ),and δ p Greater than 0 and less than or equal to 0.

05.

13. The filter device according to claim 8, wherein, The piezoelectric layer and the plurality of IDTs are configured such that a radio frequency signal applied to a respective IDT excites a primary shear acoustic mode in the diaphragm, the primary shear acoustic mode being a bulk shear mode, wherein acoustic energy propagates in a direction substantially perpendicular to the front and back surfaces of the piezoelectric layer, the front and back surfaces of the piezoelectric layer being transverse to the direction of the electric field generated by the respective IDT.

14. The filter device according to claim 8, wherein, "Small impact" means that the change in the amplitude of the main shear mode is smaller than the change in the amplitude of the stray mode.

15. The filter device according to claim 8, wherein, The markings of the staggered fingers in each portion of the first IDT and the second IDT are the widths of each staggered finger within each of the first, second, and third portions, and the markings of the staggered fingers in each portion of the first, second, and third portions of at least one of the first and second IDTs are constant in each portion and across each of the first, second, and third portions of the first and second IDTs.

16. The filter device according to claim 11, wherein, The first IDT δ of the first bulk acoustic wave resonator in the plurality of bulk acoustic wave resonators is different from the second IDT δ of the second bulk acoustic wave resonator in the plurality of bulk acoustic wave resonators.

17. An acoustic resonator, comprising: piezoelectric layer; and A conductor pattern, located on the surface of the piezoelectric layer, includes a multi-marked, multi-spacing interdigitated transducer (IDT) with interlaced fingers. The IDT is divided into at least three parts along its length, including a first part, a second part, and a third part, such that the total number of interlaced fingers of the IDT is substantially evenly distributed among the at least three parts. In each of the first, second, and third portions, the markings and spacing of the interlaced fingers are constant, and the spacing is measured as the center-to-center interval between adjacent fingers extending from different generatrices in the respective portion. The spacing within each section differs from the corresponding spacing of the other sections in the at least three sections. The acoustic resonator is either a series resonator or a parallel resonator with a passband trapezoidal filter, and... The piezoelectric layer and the IDT are configured such that a radio frequency signal applied to the IDT excites a dominant shear acoustic mode in the piezoelectric layer. This dominant shear acoustic mode is a bulk shear mode, wherein acoustic energy propagates in a direction substantially perpendicular to the surface of the piezoelectric layer, the surface of the piezoelectric layer being transverse to the direction of the electric field generated by the IDT. The effect of the spacing variation between the at least three parts on the resonant frequency of the main shear mode of all the at least three parts is less than the effect of the spacing variation on the in-band stray modes in the passband of the filter other than the main shear modes of all the at least three parts.

18. The acoustic resonator according to claim 17, wherein, The first part is marked with interlaced fingers as m(1–δ) m ), The interlaced finger-like markings in the third part are m(1+δ) m ),and δ m Greater than 0 and less than or equal to 0.

05.

19. The acoustic resonator according to claim 17, wherein, The spacing p between the interlaced fingers in the second part is the nominal spacing of the IDT. The spacing between the interlaced fingers in the first part is p(1–δ) p ), The spacing between the interlaced fingers in the third part is p(1+δ) p ),and δ p Greater than 0 and less than or equal to 0.

05.

20. The acoustic resonator according to claim 17, wherein, "Small impact" means that the change in the amplitude of the main shear mode is smaller than the change in the amplitude of the stray mode.

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