Piezoelectric trenches inserted with heavy metal electrodes of surface acoustic wave resonators

Abstract

The invention relates to a piezoelectric trench interposed with a heavy metal electrode of a surface acoustic wave resonator. A surface acoustic wave (SAW) resonator apparatus is provided. The SAW resonator device includes a first electrode positioned on an upper surface of a piezoelectric film. The first electrode may include a plurality of layers, wherein one layer of the plurality of layers is a first heavy metal layer. The SAW resonator device may also include a first piezoelectric trench (PZT) positioned adjacent to the first electrode. The first PZT includes a recess in the piezoelectric film.

Description

Technical Field

[0001] The present disclosure generally relates to acoustic wave resonators. Specifically, an acoustic wave resonator may include a piezoelectric trench interposed between electrodes including a heavy metal layer to deflect and reduce spurious content, thereby reducing interference and increasing signal quality. Background Art

[0002] Acoustic wave (AW) resonators are devices that use piezoelectric materials to convert between electrical energy and mechanical vibrations to filter and process electrical signals. AW resonators are commonly used in electronic communication devices. AW resonators are small, low-cost, and highly reliable resonators used in electronic filters for multiplexers, which makes them very suitable for use in small electronic devices.

[0003] The use of acoustic wave (AW) resonators is more common in communication applications due to several performance advantages, including low insertion loss, high selectivity and small size. Aspects of acoustic wave (AW) resonators include bulk acoustic wave (BAW) and surface acoustic wave (SAW) resonators. Designing AW filters with low insertion loss, sufficiently large passband width, good out-of-band rejection and good isolation requires optimizing the technology and resonator geometry to achieve sufficient coupling, high quality factor, large suppression of all pseudo-mode types and reduction of loss mechanisms in all three dimensions. Following these principles generally enables the construction of AW filters with sufficiently high signal quality by minimizing ripples and loss mechanisms in the filter response. Unwanted responses can be caused by the same filter or other filters within the multiplexer circuit. Therefore, cleaning up the resonator response in a large frequency range is an important goal for improving existing AW resonator technology. Summary of the invention

[0004] Embodiments of the present disclosure include devices, systems, and methods for piezoelectric grooves (PZT) between electrodes, and the electrodes include heavy metal layers within SAW resonators to improve performance. Aspects of the present disclosure advantageously provide significantly reduced interference between filters in a multiplexer circuit. In addition, aspects of the present disclosure advantageously allow the pseudo content of the surface acoustic wave resonator to shift higher in the spectrum, and shift the fundamental resonant frequency to shift lower in the spectrum, which can assist various telecommunications circuit designers in avoiding interference between resonators or filters in the circuit, thereby resulting in improved performance. In some aspects, a SAW resonator having electrodes including heavy metal layers and piezoelectric grooves between these electrodes advantageously reduces interference, shifts the pseudo content higher in the spectrum and away from the passband of other resonators or filters in the circuit, and shifts the fundamental frequency to a lower level, to a greater extent than a SAW resonator having only a heavy metal layer or PZT.

[0005] In an exemplary aspect, a surface acoustic wave (SAW) resonator device is provided. The SAW resonator device includes a first electrode positioned on an upper surface of a piezoelectric film, the first electrode comprising a plurality of layers, wherein one of the plurality of layers is a first heavy metal layer; and a first piezoelectric trench (PZT) positioned adjacent to the first electrode, the first PZT comprising a recess in the piezoelectric film.

[0006] In some aspects, the heavy metal layer of the first electrode is made of platinum. In some aspects, the heavy metal layer of the first electrode is made of tungsten. In some aspects, the heavy metal layer of the first electrode is made of gold. In some aspects, the first electrode further includes a second heavy metal layer. In some aspects, the first heavy metal layer and the second heavy metal layer are separated by a conductive layer. In some aspects, the first PZT is positioned between the first electrode and the second electrode positioned on the upper surface of the piezoelectric film. In some aspects, the SAW resonator device further includes a second electrode, and the second electrode includes a second heavy metal layer. In some aspects, the second electrode includes a third heavy metal layer. In some aspects, the first PZT is an upper PZT formed in the upper surface of the piezoelectric film. In some aspects, the first PZT is a lower PZT formed in the lower surface of the piezoelectric film. In some aspects, the first groove depth of the first PZT is equal to or less than the thickness of the piezoelectric film. In some aspects, a groove depth equal to the thickness of the piezoelectric film corresponds to a fully etched PZT. In some aspects, the SAW resonator device further includes a second PZT, and the second PZT is positioned on a side of the piezoelectric film opposite the first electrode from the first PZT.

[0007] In an exemplary aspect, a surface acoustic wave (SAW) resonator device is provided. The SAW resonator device includes a plurality of electrodes positioned on an upper surface of a piezoelectric film of a first thickness, each of the plurality of electrodes including at least one heavy metal layer; and a plurality of piezoelectric trenches (PZTs) formed in the piezoelectric film between the plurality of electrodes, wherein the plurality of PZTs correspond to regions of the piezoelectric film having a second thickness less than the first thickness.

[0008] In some aspects, the plurality of electrodes are spaced apart from each other by a first spacing, and the plurality of PZTs are spaced apart from each other by a second spacing. In some aspects, the first spacing is different from the second spacing. In some aspects, the plurality of electrodes are spaced apart from each other by an adjusted spacing such that two or more electrodes of a first subset are spaced apart from each other by a first spacing, and two or more interdigital transducers of a second subset are spaced apart from each other by a second spacing.

[0009] In an exemplary aspect, a method is provided. The method includes receiving a surface acoustic wave (SAW) resonator device, the device including: a piezoelectric film; an interdigital transducer including a plurality of interposed electrodes positioned on the piezoelectric film, each of the plurality of interposed electrodes including a heavy metal layer; and a sacrificial layer positioned on the plurality of interposed electrodes; and applying an ion beam to an upper surface of the SAW resonator device such that the sacrificial layer is removed and a piezoelectric trench (PZT) is formed between the plurality of interposed electrodes.

[0010] In some aspects, the method further includes patterning the plurality of interposed electrodes on the piezoelectric film; and patterning the sacrificial layer on the plurality of interposed electrodes. In some aspects, the interposed electrodes and sacrificial material are patterned by sputtering, photolithography, and dry etching.

[0011] Additional aspects, features, and advantages of the present disclosure will become apparent from the ensuing detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Illustrative embodiments of the present disclosure will be described with reference to the accompanying drawings, in which:

[0013] Figure 1 is a perspective view of a representative surface acoustic wave (SAW) device according to aspects of the present disclosure.

[0014] Figure 2 is a cross-sectional side view of a SAW resonator having a piezoelectric trench and a heavy metal electrode according to aspects of the present disclosure.

[0015] Figure 3A is a graphical representation of the absolute value of the admittance of a SAW resonator with and without a piezoelectric trench and a heavy metal electrode according to aspects of the present disclosure.

[0016] Figure 3B is a graphical representation of the conductance of a SAW resonator with and without a piezoelectric trench and a heavy metal electrode according to aspects of the present disclosure.

[0017] Figure 3C is a graphical representation of the quality factor of a SAW resonator with and without a piezoelectric trench and a heavy metal electrode according to aspects of the present disclosure.

[0018] Figure 3D is a graphical representation of the power consumed by a SAW resonator with and without a piezoelectric trench and a heavy metal electrode according to aspects of the present disclosure.

[0019] Figure 4A is a graphical representation of the absolute value of the admittance normalized to a common resonant frequency for SAW resonators with and without piezoelectric trenches and heavy metal electrodes according to aspects of the present disclosure.

[0020] Figure 4B is a graphical representation of the conductance normalized to a common resonant frequency of a SAW resonator having a piezoelectric trench and heavy metal electrodes according to aspects of the present disclosure.

[0021] Figure 4C is a graphical representation of the quality factor normalized to a common resonant frequency for a SAW resonator having a piezoelectric trench and a heavy metal electrode according to aspects of the present disclosure.

[0022] Figure 4D is a graphical representation of power consumption normalized to a common resonant frequency for SAW resonators with and without piezoelectric trenches and heavy metal electrodes according to aspects of the present disclosure.

[0023] Figure 5A is a graphical representation of the absolute values ​​of the admittance of SAW resonators with and without piezoelectric trenches and heavy metal electrodes normalized to a common resonant frequency and showing an extended high frequency range according to aspects of the present disclosure.

[0024] Figure 5B is a graphical representation of the conductance of a SAW resonator having a piezoelectric trench and heavy metal electrodes normalized to a common resonant frequency and showing an extended high frequency range according to aspects of the present disclosure.

[0025] Figure 5C is a graphical representation of the quality factor of a SAW resonator having a piezoelectric trench and heavy metal electrodes normalized to a common resonant frequency and showing an extended high frequency range according to aspects of the present disclosure.

[0026] Figure 5D is a graphical representation of the power consumption of a SAW resonator having a piezoelectric trench and heavy metal electrodes normalized to a common resonant frequency and showing an extended high frequency range according to aspects of the present disclosure.

[0027] Figure 6 is a graph comparing the performance of SAW ladder filters including series and parallel resonators based on resonators with and without piezoelectric trenches and heavy metal electrodes according to aspects of the present disclosure.

[0028] Figure 7 is a comparative graph of the performance of a SAW ladder filter including series and parallel resonators based on resonators with and without piezoelectric trenches and heavy metal electrodes showing an extended high frequency range according to aspects of the present disclosure.

[0029] Fig. 8A is a graph showing the relationship between the thickness of the heavy metal layer, the depth of the piezoelectric trench, and the normalized stopband width of a SAW resonator according to aspects of the present disclosure.

[0030] Figure 8B is a graph showing the relationship between the thickness of the heavy metal layer, the depth of the piezoelectric trench, and the coupling of a SAW resonator according to aspects of the present disclosure.

[0031] Figure 8C is a graph showing the relationship between the thickness of the heavy metal layer, the depth of the piezoelectric trench, and the quality factor of a SAW resonator according to aspects of the present disclosure.

[0032] Fig.8D FIG. 4 is a graph showing the relationship between the thickness of the heavy metal layer, the depth of the piezoelectric groove, and the capacitance per unit area of ​​a SAW resonator according to aspects of the present disclosure.

[0033] Fig. 9 is a graph showing ideal piezoelectric trench depth and heavy metal layer thickness according to aspects of the present disclosure.

[0034] Fig.10 is a cross-sectional side view of a SAW resonator having a piezoelectric trench and heavy metal electrodes, wherein the thickness of the heavy metal layer varies between the electrodes, according to aspects of the present disclosure.

[0035] Fig.11 is a cross-sectional side view of a SAW resonator having a piezoelectric trench and a heavy metal electrode, wherein the depth of the piezoelectric trench is adjusted, according to aspects of the present disclosure. DETAILED DESCRIPTION

[0036] For the purpose of promoting understanding of the principles of the present disclosure, reference will now be made to the embodiments shown in the drawings, and specific terms will be used for description. However, it should be understood that the scope of the present disclosure is not intended to be limited. As would be generally expected by a technician in the field to which the present disclosure belongs, any changes and further modifications made to the devices, systems and methods, and any further application of the principles of the present disclosure are fully considered and included in the present disclosure. In particular, it is fully considered that the features, components and / or steps described in one embodiment can be combined with the features, components and / or steps described in other embodiments of the present disclosure. However, for the sake of simplicity, these large amounts of repeated combinations will not be described separately.

[0037] Exemplary embodiments of the present disclosure relate to SAW resonators having electrodes, including a heavy metal layer and a piezoelectric trench (PZT) between the electrodes. In some aspects, the guided SAW type technology has a high quality factor, high coupling, and low TCF. In some aspects, the SAW resonator, such as Figure 1As shown and described in, may be otherwise referred to as LRT-SAW, multilayer SAW, thin film SAW or any other suitable term. Any of these terms may be used in the present disclosure and are not intended to be limiting. The key improvement point of this type of technology is the reduction of existing loss mechanisms and pseudo acoustic modes. For challenging applications, these can currently affect in-band and near-band performance (e.g., limited stopband width, limited distance to the carrier substrate of the body wave start) as well as affect out-of-band specifications and make multiplexing with other filters challenging. The invention disclosed herein improves these major challenges of guided SAW type technology.

[0038] Figure 1 is a perspective view of a representative surface acoustic wave (SAW) device according to aspects of the present disclosure. Although the present disclosure describes the principles of the present disclosure in the context of a SAW resonator, it should be understood that the presented technology can be equally applied to any suitable type of acoustic wave (AW) resonator, including SAW resonators and BAW resonators. It is particularly applicable to any AW resonator that employs an interdigital transducer electrode for various orientations of acoustic wave propagation and displacements relative to the arrangement of the electrodes. The SAW device 10 includes a substrate 12, a piezoelectric layer 14 on the substrate 12, an interdigital transducer (IDT) 16 including an electrode 22 on the surface of the piezoelectric layer 14 relative to the substrate 12, a first reflector structure 18A adjacent to the interdigital transducer 16 on the surface of the piezoelectric layer 14, and a second reflector structure 18B adjacent to the interdigital transducer 16 on the surface of the piezoelectric layer 14 and opposite to the first reflector structure 18A. In some aspects, an interdigital transducer may also be referred to as an interdigital transducer. In certain aspects, the substrate 12 may be referred to as a carrier substrate, and the overall SAW device 10 may be referred to as a guided SAW device.

[0039] The interdigital transducer 16 includes a first electrode 20A and a second electrode 20B, each of which includes a plurality of electrodes 22 interposed with each other, as shown. The first electrode 20A and the second electrode 20B may also be referred to as comb electrodes. The lateral distance between the adjacent electrodes 22 of the first electrode 20A and the second electrode 20B defines the spacing P between the adjacent electrodes 22. The spacing P may at least partially define the resonant frequency of (multiple) corresponding electrodes 22. In this regard, in an embodiment where the spacing P between the electrodes 22 is uniform, all electrodes 22 may be configured to correspond to the same resonant frequency. This resonant frequency may be the resonant frequency of the SAW device 10. The resonant frequency may be the center frequency or main frequency of the mechanical wave generated in the piezoelectric layer 14 by one or more electrodes 22. The electrode width W of the adjacent electrodes 22 and the spacing P may define the metallization ratio or task factor of the electrode 22.

[0040] In operation, the AC input signal provided at the first electrode 20A is converted into a mechanical signal in the piezoelectric layer 14, thereby obtaining one or more acoustic waves therein. In the case of the SAW device 10, the obtained acoustic waves are mostly surface acoustic waves. As discussed above, based on the pitch P of the interdigital transducer 16 and the metallization ratio, the characteristics of the material of the piezoelectric layer 14 and other factors, the magnitude and frequency of the acoustic waves converted in the piezoelectric layer 14 depend on the frequency of the AC input signal. This frequency dependence is usually described by using the change in impedance and / or the phase shift between the first electrode 20A and the second electrode 20B relative to the frequency of the AC input signal. The AC potential between the first electrode 20A and the second electrode 20B induces an electric field in the piezoelectric material that generates the acoustic wave. The acoustic wave travels on the surface and is eventually transmitted back to the electrical signal between the electrodes 20A and 20B. The first reflector structure 18A and the second reflector structure 18B reflect the acoustic waves in the piezoelectric layer 14 back toward the interdigital transducer 16 to confine the acoustic waves to a region surrounding the interdigital transducer 16. The substrate 12 may include various materials, including glass, sapphire, quartz, diamond, silicon (Si) or gallium arsenide (GaAs), among which Si is a common choice. The piezoelectric layer 14 may be formed of any (multiple) suitable piezoelectric materials. In certain embodiments described herein, the piezoelectric layer 14 is formed of lithium tantalate (LT) or lithium niobate (LiNbO3 or LN), but is not limited thereto. In certain embodiments, the piezoelectric layer 14 is thick enough or rigid enough to be used as a piezoelectric substrate. Therefore, Figure 1 The substrate 12 in the embodiment may be omitted. It should be understood by those skilled in the art that the principles of the present disclosure may be applied to other materials for the substrate 12 and the piezoelectric layer 14. The interdigital transducer 16, the first reflector structure 18A and the second reflector structure 18B may include one or more conductive materials, including titanium (Ti), aluminum (Al), copper (Cu) and alloys thereof, and alloys with other suitable materials, and may be made of a single layer or a multilayer arrangement, etc. Although not shown to avoid obscuring the drawings, an additional dielectric layer or any other layer may be disposed over all or part of the exposed surfaces of the piezoelectric layer 14, the interdigital transducer 16, the first reflector structure 18A and the second reflector structure 18B. Such additional passivation layers may form any surface topology, including but not limited to conformal coatings and flat surfaces. Such additional dielectric layers may be provided for reasons such as passivation, for frequency trimming, for temperature compensation purposes and / or improved thermal conductivity. Suitable materials for such layers include silicon oxide, silicon nitride, titanium oxide, aluminum oxide, and may also include dopants such as fluorine. Furthermore, in various embodiments, one or more layers may be provided between the substrate 12 and the piezoelectric layer 14 .

[0041] In some aspects, a SAW resonator, such as Figure 1 The SAW resonator shown and described in may alternatively be referred to as a guided SAW, LRT-SAW, multilayer SAW, thin film SAW, or any other suitable terminology.

[0042] Figure 2 2 is a cross-sectional side view of a SAW resonator 200. The SAW resonator 200 includes various components, including a carrier substrate 245, a dielectric layer 240, a dielectric layer 235, a piezoelectric film 230, and two electrodes 222A and 222B.

[0043] The carrier substrate 245 forms the base of the SAW resonator 200 and provides structural support for the device. It can be made of a variety of materials, including glass, silicon, silicon carbide, quartz, diamond, sapphire, or any other suitable material. In some embodiments, the carrier substrate 245 can be selected based on its mechanical, thermal, or electrical properties to meet specific application requirements.

[0044] The dielectric layer 240 is positioned on top of the carrier substrate 245 and provides electrical insulation between the carrier substrate 245 and the rest of the SAW resonator 200. In some aspects, the dielectric layer 240 can additionally provide a velocity contrast with the piezoelectric layer to help guide the waves that are primarily concentrated in the piezoelectric layer. The dielectric layer 240 can additionally help avoid losses due to overlap with the carrier material and reduce TCF. The dielectric layer 240 can be made of a variety of materials, including silicon dioxide, silicon oxide, silicon nitride, or aluminum oxide, or any other material, depending on the specific application requirements.

[0045] In some aspects, the dielectric layer 240 may alternatively be a high trapping layer (TRL). The TRL may, for example, be silicon based, such as polysilicon or an implanted layer near the top surface of the carrier wafer itself.

[0046] The dielectric layer 235 is positioned on top of the dielectric layer 240 and serves as a second electrically insulating layer. It can also be made of a variety of materials, including any of those described with reference to layer 240. In some aspects, a resonator can include any suitable number of dielectric layers in any suitable arrangement.

[0047] The piezoelectric film 230 is positioned on top of the dielectric layer 235 and converts electrical energy into mechanical energy. The piezoelectric film 230 can be made of various materials, including lithium tantalate, lithium niobate, zinc oxide, aluminum nitride, scandium aluminum nitride or any other material. In operation, the piezoelectric film 230 is excited by the electrodes 222A and 222B to generate acoustic waves. A common choice for the piezoelectric layer may be a thickness less than five times the wavelength λ of the acoustic wave. It is generally advantageous to have a thickness less than one wavelength and may be between 5% and 60% of the wavelength, but the invention disclosed herein is not limited to these examples. A common choice for the piezoelectric material may be lithium tantalate, where the orientation is typically between Y+0° and Y+60° and propagates along the x-axis of the crystal. An orientation close to 42° YX LT is a common choice, while an orientation close to 30° YX LT may in some cases cause the excitation of Rayleigh-type pseudo-acoustic modes to be minimized. Another common choice of the piezoelectric material may be lithium niobate, where the orientation is typically between Y-20° and Y+60° and propagates along the x-axis of the crystal. Orientations close to 10° Y-XLN and 20° YXLN may be implemented, but are not limiting. Large coupling coefficients may be obtained. In these piezoelectric layers, the device primarily excites waves with shear horizontal displacement, and the invention disclosed herein is not limited to optimization with respect to this wave type.

[0048] The electrodes 222A and 222B are positioned on top of the piezoelectric film 230 and excite the piezoelectric film 230. The transducers 222A and 222B are transducers within a series of alternating and / or interleaved fingers (see, e.g., Figure 1 In operation, one of the transducers 222A or 222B may be connected to a positive potential, while the other may be connected to a negative potential, causing acoustic waves to be generated in the piezoelectric film 230. The transducers 222A and 222B each include a plurality of layers, such as Figure 2 As shown in .

[0049] In some embodiments, the electrode 222A may include a layer 224A, a layer 226A, and a layer 228A. However, in addition to or in lieu of reference Figure 2 In addition to the layers shown and described, the electrode 222A and any other electrodes (e.g., electrode 222B or any other electrode) may alternatively include any suitable number or type of layers. Similar to the electrode 222A, the electrode 222B may include a layer 224B, a layer 226B, and a layer 228B. For the purposes of this disclosure, the layers 228A and 228B will be described together with reference to the layer 228. Similarly, the layers 226A and 226B and the layers 224A and 224B will be explained in conjunction.

[0050] In some aspects, the layer 228 can promote adhesion to the wafer, to avoid migration of atoms (into the substrate and along the surface) and to result in suitable crystallinity of the layer above. The layer 228 can be a heavy metal. In this regard, the layer 228 can be referred to as a heavy metal layer. In some aspects, an electrode comprising at least one heavy metal layer can be referred to as a heavy metal electrode. The layer 228 can be composed of any suitable heavy metal. For example, the layer 228 can be composed of osmium, iridium, platinum, rhenium, gold, tungsten, tantalum, hafnium, rhodium, ruthenium, thallium, lead, silver, molybdenum, palladium, and alloys containing one or more of the mentioned materials.

[0051] Although not shown in Figure 2 2, but in some aspects, each electrode 222 may include an additional layer positioned below the heavy metal layer 228. For example, this additional layer may be a thin layer that may provide adhesion or appropriate crystallinity for any of the other layers. This thin layer provided below the heavy metal layer 228 may be composed of a titanium layer or any other suitable material.

[0052] In some aspects, because the layer 228 is composed of heavy metal, the speed of the acoustic waves generated by the SAW resonator 200 can be reduced. In addition, the reflectivity of the SAW resonator 200 can be increased. These effects can be modified by changing the thickness of the layer 228. In some aspects, as the thickness of the layer 228 increases, the quality factor of the SAW resonator 200 can begin to decrease, introducing insertion losses. This can be a result of the increased overlap of the acoustic wave mode with the intrinsic lossy metal material.

[0053] As described in more detail below, by increasing the depth of the piezoelectric trench (PZT) 270 positioned between the electrodes 222, the velocity of the acoustic waves of the SAW resonator 200 can be reduced and the reflectivity of the SAW resonator 200 can alternatively be increased. As with the heavy metal layer 228, increasing the depth of the PZT 270 can reduce wave velocity and increase reflectivity. However, as the depth increases to a certain extent, the quality factor of the resonator 200 may begin to decrease. In this regard, when the thickness of the heavy metal layer is increased while still maintaining a sufficient quality factor, the PZT 270 can be introduced and / or deepened to further reduce the wave velocity and increase reflectivity without negatively affecting the quality factor of the resonator 200. This advantageously increases resonator performance. In this regard, while the introduction of piezoelectric grooves may by themselves reduce the wave velocity and increase the reflectivity of the resonator, and while the inclusion of a heavy metal layer may also independently reduce the wave velocity and increase the reflectivity, for a number of reasons, the current state of the art does not include both of these features (i.e., PZT and heavy metal layers) in the same resonator.

[0054] First, because the depth of the piezoelectric groove is specified during the design of the SAW resonator, those skilled in the art have traditionally assumed that once the quality factor of the resonator begins to decrease with increasing depth of the piezoelectric groove, any design changes that further reduce the wave velocity will have the same effect as increasing the depth of the piezoelectric groove (i.e., reducing the quality factor) and are not implemented. Similarly, because the thickness of the heavy metal layer is specified during the design of the SAW resonator, those skilled in the art have traditionally assumed that once the quality factor of the resonator begins to decrease with increasing thickness of the heavy metal layer, any design changes that further reduce the wave velocity will have the same effect as increasing the thickness of the heavy metal layer (i.e., reducing the quality factor) and are not implemented. Therefore, those of ordinary skill in the art are generally discouraged from implementing both PZT and heavy metal layers in the electrodes of a SAW resonator device.

[0055] Furthermore, to the extent that one skilled in the art considers combining PZT and heavy metal layers in an electrode of a SAW resonator device, the combined effect is unexpected, as will be explained in more detail below.

[0056] The layer 226 may be made of a conductor such as copper or aluminum. The layer 226 may ensure low resistance and low electrical losses in the IDT fingers. In some aspects, the layer 224 may provide adhesion for additional metal layers such as under bump metal for routing and may help prevent oxidation and degradation of underlying layers. In some aspects, the electrode 222 may include additional barrier layers or layer stacks for similar purposes, including to reduce sheet resistance, to reduce mechanical damping, or to increase robustness to withstand environmental conditions such as moisture or excitation at high power.

[0057] The layer 224 can be composed of any suitable material. In some aspects, the layer 224 can be a sacrificial layer that can be partially or completely removed during trimming without passivation ("PAS-free trimming") processes.

[0058] The SAW resonator 200 also shows a piezoelectric groove (PZT) 270. In some aspects, the PZT 270 can be formed with a PAS-free trimming process after the SAW resonator 200 is assembled. In some aspects, the PZT 270 can be formed in any other way. In some aspects, the PAS-free trimming process includes removing material from the SAW resonator 200 using an ion beam. The ion beam can be a beam of charged particles (e.g., a plurality of ions) that are accelerated and focused on a region of the resonator using photolithography. The ion beam can scan across the surface of the resonator to selectively remove material. By changing the angle of the ion beam, the shape of the resonator can be changed. In addition, the PAS-free trimming process can also be applied to the reflectors 18A and 18B of the SAW resonator 200. The reflectors 18A and 18B can also be referred to as gratings.

[0059] According to one manufacturing process of the SAW resonator 200 - 2 , the resonator can first be designed to have a fundamental resonant frequency that is higher than a desired fundamental resonant frequency. In some aspects, a PAS-free trimming process can be performed on the SAW resonator 200 . Figure 2 The geometry of the SAW resonator 200 shown in FIG. 1 may be the resulting cross-sectional shape of the SAW resonator 200. Through this process, the fundamental resonant frequency may be shifted downward to a desired fundamental resonant frequency. By adjusting the properties and scanning parameters of the ion beam during the PAS-free trimming procedure, the fundamental resonant frequency may be precisely controlled to achieve a desired frequency.

[0060] like Figure 2 As shown, the PZT 270 may be configured according to any suitable geometry. Figure 2 In the example shown, the PZT 270 may include a tapered edge or shoulder. Specifically, the PZT 270 includes a lower PZT width 274 and an upper PZT width 276. In the example shown, the upper PZT width 276 may be greater than the lower PZT width 274. Thus, shoulders are formed on either side of the PZT 270. These shoulders may be inclined regions extending from the top surface of the piezoelectric film 230 to the lower surface of the PZT 270. In some aspects, the shoulders of the PZT 270 may be inclined according to an angle 278. In some aspects, the inclined shoulders may be symmetrical about the central axis of the PZT 270. In other aspects, the PZT 270 may be asymmetrical. For example, one side of the PZT 270 may be more steeply inclined than the other side, or vice versa. Any suitable geometry of the PZT 270 may be used.

[0061] like Figure 2As shown, the PZT 270 may have a depth 272, and the total thickness of the piezoelectric film 230 may be a thickness 260. In some aspects, the performance of the SAW resonator 200 may depend at least in part on the relationship between the depth 272 of the PZT 270 and the thickness 260 of the piezoelectric film 230. In some aspects, this relationship may be quantified as a percentage of the depth 272 of the thickness 260 or a ratio between the two.

[0062] Also like Figure 2 As shown, the electrode 222 may have a thickness 250. The width of the electrode 222 may be a width 232, and the electrodes 222 may be spaced apart according to a spacing 242. Although not shown to avoid obscuring the drawing, additional layers are disposed within the PZT or on top of the electrodes over all or a portion of the piezoelectric surface. This may include a dielectric layer, which may serve for temperature compensation, passivation, frequency shaping, or other purposes.

[0063] As explained below, the performance of the SAW resonator 200 is greatly improved over standard SAW resonators that do not include electrodes having heavy metal layers (ie, heavy metal electrodes) or PZT.

[0064] In some aspects, the electrode 222 of the SAW resonator 200 may include multiple heavy metal layers. Figure 2 The electrode 222A shown in 2000 comprises a single heavy metal layer 228A, but the electrode 222A may alternatively comprise multiple heavy metal layers. For example, multiple heavy metal layers may be separated within the stack by conductive layers similar to the layer 226A. In this regard, each heavy metal layer may individually contribute to the slowing down of the wave, while the heavy metal layer closest to the piezoelectric surface will contribute more to ensuring the high quality factor of the resonator (due to the less damping, higher material Q of the layer) and to reliability, making it less susceptible to acoustic migration, while other heavy metal layers higher in the stack may achieve other additional purposes, such as contributing in part to improved conductivity.

[0065] Figure 3A is a graphical representation of the absolute value of the admittance of a SAW resonator with and without a piezoelectric trench and a heavy metal electrode according to aspects of the present disclosure. Figure 3A Graph 300A is included. Graph 300A may include an x-axis 310A corresponding to frequency and a y-axis 320A corresponding to admittance. As shown in graph 300A, data set 330-1 represents the admittance of a SAW resonator that does not include heavy metal electrodes or PZT. Data set 330-2 represents a SAW resonator that does include both heavy metal electrodes and PZT (e.g., SAW resonator 200( Figure 2)) frequency response. Both data sets present a resonant frequency 331 and an anti-resonant frequency 332. The resonant frequency 331 represents the frequency at which the SAW resonator has a maximum admittance, while the anti-resonant frequency 332 represents the frequency at which the SAW resonator has a minimum admittance.

[0066] The resonant frequency 331 - 2 and the anti-resonant frequency 332 - 2 (both corresponding to a SAW resonator having both heavy metal electrodes and PZT) are significantly shifted down along the frequency spectrum compared to the resonant frequency 331 - 1 and the anti-resonant frequency 332 - 1 .

[0067] Figure 3A In addition, pseudo content 333-1 and 333-2 are shown. It should be noted that the response of the resonator with heavy metal electrodes and PZT and the response of the resonator without heavy metal electrodes or PZT present similar patterns. The resonance and anti-resonance frequencies of data set 330-2 are shifted down by similar amounts compared to the resonance and anti-resonance frequencies of data set 330-1. The frequency shift may depend on factors such as the type of ion beam used without the PAS trimming procedure, the angle of incidence, the duration of the trimming, the type of heavy metal of the heavy metal electrode, and the thickness of the heavy metal layer. Although the resonance 331-2 and the anti-resonance 332-2 are shifted downward in frequency relative to the resonance 331-1 and the anti-resonance 331-2, the pseudo content 333-2 is actually shifted upward in frequency relative to the pseudo content 333-1. This advantageously provides a wider available frequency band. This change in the frequency response of both the resonance and anti-resonance and the pseudo content can be used to optimize the SAW resonator design and improve its performance. The frequency shift can be used to adjust the resonant frequency of the SAW resonator to a desired value. This is particularly useful in applications such as filters, where a precise frequency response is required.

[0068] Figure 3B is a graphical representation of the conductance of a SAW resonator with and without a piezoelectric trench and a heavy metal electrode according to aspects of the present disclosure. Figure 3B Graph 300B is included. Graph 300B may include an x-axis 310B corresponding to frequency and a y-axis 320B corresponding to conductance. As shown in graph 300B, data set 340-1 represents the conductance of a SAW resonator that does not include heavy metal electrodes or PZT, while data set 340-2 represents a SAW resonator that does include both heavy metal electrodes and PZT (e.g., the SAW resonator 200 ( Figure 2 )) of the conductance. Both data sets show the resonant frequency 341 and the pseudo content 342. The resonant frequency 341 in the two data sets may correspond to the reference Figure 3A The corresponding resonant frequency 331 is described.

[0069] Similar to reference Figure 3AAs described above, the resonant frequency 341-2 is shifted below the resonant frequency 341-1. However, the pseudo content 342-2 may be shifted along the spectrum above the pseudo content 342-1. As shown, this lowered shift in the fundamental resonant frequency and the raised shift of the pseudo content may result in a wider frequency band between the two features. This may advantageously allow the resonator to interfere less with the passband of a filter (e.g., a ladder filter or any other suitable circuit containing such a resonator) and interfere less with the performance of the filter at the common port.

[0070] Figure 3C is a graphical representation of the quality factor of a SAW resonator with and without a piezoelectric trench and a heavy metal electrode according to aspects of the present disclosure. Figure 3C Graph 300C is included. Graph 300C includes data set 350-1 and data set 350-2. In some aspects, data set 350-1 may be a data set corresponding to the frequency response of a SAW resonator that does not include heavy metal electrodes or PZT. Data set 1750-2 may be a data set corresponding to the SAW resonator that does include both heavy metal electrodes and PZT (e.g., SAW resonator 200 ( Figure 2 )) dataset.

[0071] like Figure 3C As shown, the quality factor of the data set 350-2 of the SAW resonator is greater than the quality factor of the data set 350-1. In some aspects, an increase in the quality factor of the SAW resonator can correspond to a reduced loss of the SAW resonator. In some aspects, this reduced loss can be attributed to the acoustic energy being localized farther away from the metal electrode. In this regard, the more the trench depth is increased and / or the thicker the heavy metal layer of the one or more heavy metal electrodes, the greater the improvement in the quality factor.

[0072] Figure 3D is a graphical representation of the consumed power of a SAW resonator with and without a piezoelectric trench and a heavy metal electrode according to aspects of the present disclosure. The consumed power may also be referred to as absorbed power. Figure 3D Graph 300D is included. Graph 300D includes data set 360-1 and data set 360-2. In some aspects, data set 360-1 may be a data set corresponding to the frequency response of a SAW resonator that does not include heavy metal electrodes or PZT. Data set 360-2 may be a data set corresponding to a SAW resonator that does include both heavy metal electrodes and PZT (e.g., SAW resonator 200 ( Figure 2 )) dataset.

[0073] In some aspects, data set 360-1 includes peak 361-1 and peak 362-1. Data set 360-2 includes peak 361-2 and peak 362-2.

[0074] like Figure 3DAs shown, as the depth of the PZT increases and / or as the thickness of the heavy metal layer of the heavy metal electrode increases, the peak corresponding to the upper stop band edge (eg, peak 362 - 2 ) may move higher along the frequency spectrum.

[0075] Figure 4A is a graphical representation of the absolute value of admittance normalized to a common resonant frequency for SAW resonators with and without piezoelectric trenches and heavy metal electrodes according to aspects of the present disclosure.

[0076] As previously described, including PZT and including heavy metal layers within the electrodes of a SAW resonator can result in a reduction in the fundamental resonant frequency. To compensate for the shift in fundamental resonant frequency, the SAW resonator can be selected so that the final resonant frequency corresponds to the desired target resonant frequency after any necessary PAS-free trimming procedures. Alternatively, in other aspects, the SAW resonator can be designed to include PZT and heavy metal layers, as explained, and designed to the desired resonant frequency. To illustrate the effect of PZT and heavy metal layers for SAW resonators of the same fundamental frequency, Figures 4A to 4D It can be normalized about the fundamental resonant frequency.

[0077] In this regard, Figure 4A Graph 400A is included. Graph 400A includes data set 430-1 and data set 430-2. In some aspects, data set 430-1 may be a data set corresponding to the frequency response of a SAW resonator that does not include heavy metal electrodes or PZT. Data set 430-2 may be a data set corresponding to a SAW resonator that includes both heavy metal electrodes and PZT (e.g., SAW resonator 200 ( Figure 2 ))’s frequency response dataset.

[0078] like Figure 4A As shown, each of the data sets 430-1 and 430-2 includes a peak 431 aligned around the normalized fundamental frequency. Each of the data sets 430-1 and 430-2 also includes an anti-resonance frequency. As shown, the anti-resonance frequencies may not be aligned with each other, but may be similar. This may result in a slight reduction in the effective coupling coefficient of the SAW resonator.

[0079] Figure 4A It also shows how the overall amplitude of data sets 430-1 and 430-2 decreases as the PZT depth increases and / or as the heavy metal layer thickness increases. This may indicate a decrease in the capacitance of the SAW resonator.

[0080] Figure 4B is a graphical representation of the conductance normalized to a common resonant frequency of a SAW resonator having a piezoelectric trench and heavy metal electrodes according to aspects of the present disclosure. Figure 4BGraph 400B is included. Graph 400B includes data set 440-1 and data set 440-2. In some aspects, data set 440-1 may be a data set corresponding to the frequency response of a SAW resonator that does not include heavy metal electrodes or PZT. Data set 440-2 may be a data set corresponding to a SAW resonator that does include both heavy metal electrodes and PZT (e.g., the SAW resonator 200 ( Figure 2 )) dataset.

[0081] Similar to graph 400A, the data set of graph 400B is normalized with respect to the resonant frequency for comparison. Thus, the peak 441 of each of the data sets 440-1 and 440-2 is aligned around the center normalized frequency. Figure 4B A peak 442-1 corresponding to the upper stopband edge of the SAW resonator is shown, which corresponds to the data set 440-1. The peak 442-1 will be described in more detail, especially with reference to the following Figure 5B However, it should be noted that the amplitude of the conductance of the data set 440-2 above the peak 441 is smaller than the amplitude of the conductance of the data set 440-1 above the peak 441, which may contribute to the improved performance of the SAW resonator with PZT and heavy metal layers.

[0082] Figure 4C is a graphical representation of the quality factor normalized to a common resonant frequency for a SAW resonator having a piezoelectric trench and a heavy metal electrode according to aspects of the present disclosure. Figure 4C Graph 400C is included. Graph 400C includes data set 450-1 and data set 450-2. In some aspects, data set 450-1 may be a data set corresponding to the frequency response of a SAW resonator that does not include heavy metal electrodes or PZT. Data set 450-2 may be a data set corresponding to a SAW resonator that does include both heavy metal electrodes and PZT (e.g., the SAW resonator 200 ( Figure 2 )) dataset.

[0083] Similar to graph 400A, the data set for graph 400C is normalized with respect to resonant frequency for comparison. Figure 4C As shown, the quality factor of the SAW resonator of data set 450-2 is greater than the quality factor of data set 450-1. In some aspects, the increase in the quality factor of the SAW resonator can correspond to reduced losses of the SAW resonator. In some aspects, this reduced loss can be attributed to the acoustic energy being localized farther away from the metal electrode. In this regard, the more the trench depth is increased and / or the thicker the heavy metal layer of the one or more heavy metal electrodes, the greater the improvement in the quality factor.

[0084] Figure 4Dis a graphical representation of power dissipation normalized to a common resonant frequency for SAW resonators with and without piezoelectric trenches and heavy metal electrodes according to aspects of the present disclosure. The power dissipation may also be referred to as the absorbed power. Figure 4D Graph 400D is included. Graph 400D includes data set 460-1 and data set 460-2. In some aspects, data set 460-1 may be a data set corresponding to the frequency response of a SAW resonator that does not include heavy metal electrodes or PZT. Data set 460-2 may be a data set corresponding to a SAW resonator that does include both heavy metal electrodes and PZT (e.g., the SAW resonator 200 ( Figure 2 )) dataset.

[0085] Similar to graph 400A, the data set for graph 400D is normalized with respect to resonant frequency for comparison. Figure 4D As shown in , the power consumption of the data set 460 - 2 is significantly improved over the power consumption of the data set 460 - 1 .

[0086] Figure 5A is a graphical representation of the absolute values ​​of the admittance of SAW resonators with and without piezoelectric trenches and heavy metal electrodes normalized to a common resonant frequency and showing an extended high frequency range according to aspects of the present disclosure. Figure 5A Graph 500A is included. Graph 500A may be substantially similar to Figure 4A For example, graph 500A may include higher frequency content of the same data. In this regard, graph 500A may additionally illustrate pseudo content 432-2. As shown, the frequency of pseudo content 432-2 may be significantly shifted higher than pseudo content 432-1 due to the PZT and heavy metal layers of the SAW resonator corresponding to data set 430-2.

[0087] Figure 5B is a graphical representation of the conductance of a SAW resonator having a piezoelectric trench and heavy metal electrodes normalized to a common resonant frequency and showing an extended high frequency range according to aspects of the present disclosure. Figure 5B Graph 500B is included. Graph 500B may be substantially similar to Figure 4B For example, graph 500B may contain higher frequency content of the same data.

[0088] In some aspects, data set 440-1 includes peak 442-1, as shown in FIG. Figure 4A However, as shown in the extended range of graph 500B, data set 440-2 includes peak 442-2. In some aspects, as the depth of the PZT increases and / or as the thickness of the heavy metal layer increases, the peak corresponding to the upper stopband edge may shift higher along the spectrum. When the fundamental frequency has been normalized, Figure 5B Graph 500B of FIG. 5 shows more clearly the extent to which this shift in the upper stopband edge occurs. As shown, the frequency of peak 442-2 corresponding to the SAW resonator having PZT and heavy metal layers is significantly higher than peak 442-1. This shift in the upper stopband edge can move spurious content out of the passband of that frequency, as well as out of the passband of other filters, resulting in a significant increase in the signal quality and performance of the multiplexer circuit.

[0089] Figure 5C is a graphical representation of the quality factor of a SAW resonator having a piezoelectric trench and heavy metal electrodes normalized to a common resonant frequency and showing an extended high frequency range according to aspects of the present disclosure. Figure 5C Graph 500C is included. Graph 500C may be substantially similar to Figure 4C For example, graph 500C may contain higher frequency content of the same data. Figure 5C As shown, the quality factor of the data set 450 - 2 of the SAW resonator is greater than the quality factor of the data set 450 - 1 .

[0090] Figure 5D is a graphical representation of the power consumption of a SAW resonator having a piezoelectric trench and heavy metal electrodes normalized to a common resonant frequency and showing an extended high frequency range according to aspects of the present disclosure. Figure 5D Graph 500D is included. Graph 500D includes data set 560-1 corresponding to a SAW resonator that does not include heavy metal electrodes or PZT. Graph 500D also includes data set 560-1 corresponding to a SAW resonator that does include both heavy metal electrodes and PZT (e.g., SAW resonator 200 ( Figure 2 ))’s data set 560-2.

[0091] Data set 560-1 includes peak 561-1 and peak 562-1. Data set 560-2 includes peak 561-2 and peak 562-2. Figure 5D As shown, as the depth of the PZT increases and / or as the thickness of the heavy metal layer increases, the peak corresponding to the upper stop band edge (eg, peak 562 - 2 ) may move higher along the spectrum.

[0092] Figure 6 is a graph comparing the performance of SAW ladder filters including series and parallel resonators based on resonators with and without piezoelectric trenches and heavy metal electrodes according to aspects of the present disclosure. Figure 6Graph 600A is included. In some aspects, graph 600A corresponds to a comparison of the frequency response of a filter including a SAW resonator without PZT or heavy metal layers to the frequency response of a filter including a SAW resonator including PZT and heavy metal layers for improved performance. The graph includes data 6100-1 corresponding to aspects of a filter including a SAW resonator without PZT or heavy metal layers and data 6100-2 corresponding to aspects of a filter including a SAW resonator including PZT and heavy metal layers.

[0093] Figure 6 Each of the graphs of also highlights multiple frequency bands for mobile communications. For example, bands 6110 and 6111 are shown as corresponding to the passbands of the filter, and in some aspects, may correspond to the B28+B20 Rx passbands. The other highlighted bands may correspond to other frequency regions corresponding to the filter passbands within the multiplexer circuit or any other suitable circuit. These other bands include band 6109 corresponding to the B28 Tx band, band 6112 corresponding to the B20 Tx band, band 6113 corresponding to the B8 Tx band, and band 6114 corresponding to the B8 Rx band.

[0094] As shown in graph 600A, the frequency response of the transmission coefficient corresponding to the filter without PZT or heavy metal layer includes lower band edge 6140-1 and upper band edge 6141-1. The frequency response corresponding to the filter with PZT and heavy metal layer includes lower band edge 6140-2 and upper band edge 6141-2.

[0095] Graph 600B also shows a comparison of the reflection coefficient at a port of a filter without PZT or heavy metal layer and the reflection coefficient at the same port of a filter with PZT and heavy metal layer. Lower band edge 6142-1 may be aligned in frequency with lower band edge 6140-1, for example. Similarly, lower band edge 6142-2 may be aligned in frequency with lower band edge 6140-2. Upper band edge 6143-1 may be aligned with upper band edge 6141-1, and upper band edge 6143-2 may be aligned with upper edge 6141-2. The reflection coefficient of the filter without PZT or heavy metal layer (6100-1) shows a dip and is further away from the zero dB level region than the filter with PZT and heavy metal layer (6100-2), which indicates losses and spurious responses that may affect other filters when multiplexed on the same node. The low absolute value of the reflection coefficient of the filter (6100-2) with PZT and heavy metal layers, close to zero dB, and the clean response with no dips in the reflection coefficient show the benefit of multiplexing this filter with other filters, such as those for bands 6112, 6113, and 6114.

[0096] Graph 600C shows the maximum available gain (GMAX) for the filter transmission. This is an indication of the filter loss level. The higher quality factor of the resonator with PZT and heavy metal layer results in a lower loss filter. It can be seen that GMAX is closer to zero dB for the filter with PZT and with heavy metal layer (6100-2) than for the filter without PZT or heavy metal layer (6100-2).

[0097] Graph 600D also shows the power consumption of a filter without PZT or a heavy metal layer compared to the power consumption of a filter with PZT and a heavy metal layer.

[0098] As shown in graph 600D, the level of power consumption of data set 6100-2 (corresponding to the filter with PZT and heavy metal layer) is less than that of data set 6100-1 (corresponding to the filter without PZT and heavy metal layer). The difference in magnitude between data set 6100-2 and data set 6100-1 is shown by highlighted area 6199. This shows that the filter with PZT and heavy metal layer (6100-2) has less loss than the filter without PZT or heavy metal layer (6100-2).

[0099] Graph 600E shows the conductance of the series resonator in the ladder filter. Figure 6 As shown in , peak 6148-1 may be aligned with the center of the passband of the filter shown in graph 600A without PZT or heavy metal layer. Similarly, peak 6148-2 may be aligned with the center of the passband of the filter with PZT and heavy metal layer shown in graph 600A. As shown in graph 600D, data 600-1 includes peak 6149-1 corresponding to the upper stopband edge between passband 6111 and passband 6112. Peak 6149-1 of graph 600E causes peak 6198 in consumed power (graph 600D) and dip 6197 in reflection coefficient (graph 600B), resulting in undesirable losses and excitation of specific pseudo-acoustic modes.

[0100] Graph 600F shows the conductance of the parallel resonators within the ladder filter. Data 600-1 includes a peak 6150-1 that aligns with the notch in transmission at the lower end of the passband edge 6140-1 of graph 600A. Data 600-2 includes a peak 6150-2 that aligns with the notch in transmission at the lower end of the passband edge 6140-2 of graph 600A. As shown in graph 600F, data 600-1 also includes a peak 6151-1. Peak 6151-1 may correspond to the upper stopband edge of the resonator without a PZT or heavy metal layer. In some cases, this peak 6151-1 may negatively impact the signal quality of the filter, especially when falling into the passband of the filter, such as near the upper band edge. This may not only degrade the small signal performance, but may also cause failure when higher power is applied to the filter. However, as Figure 6 As shown in , the filter with a SAW resonator including PZT and heavy metal shifts this peak significantly higher, as shown in Figure 7 Discussed in more detail.

[0101] Graph 600G shows the absolute value of the conductance of the series resonator in the ladder filter. Figure 6 , peak 6152 may be aligned with the center of the passband of filter 600-1 without PZT or heavy metal layers and the center of the passband of filter 600-2 with PZT and heavy metal layers. Peak 6152 may be a resonance of both data sets 600-1 and 600-2. Data set 600-1 may include anti-resonance 6153-1 that is aligned with the notch in transmission at the upper end of passband edge 6141-1 of graph 600A. Data set 600-2 may include anti-resonance 6153-2 that is aligned with the notch in transmission at the upper end of passband edge 6141-2 of graph 600A.

[0102] Graph 600H shows the absolute value of the conductance of the parallel resonator within the ladder filter. The resonant frequencies or peaks 6155-1 and 6155-2 correspond to the notches in transmission at the lower ends of the passband edges 6140-1 and 6140-2, respectively, of graph 600A. Both data sets 600-1 and 600-2 may include an anti-resonance 6156 aligned with the passband center of graph 600A.

[0103] Figure 7 is a comparative graph of the performance of a SAW ladder filter including series and parallel resonators based on resonators with and without piezoelectric trenches and heavy metal electrodes showing an extended high frequency range according to aspects of the present disclosure.

[0104] Graph 700A shows the frequency response of the transmission coefficient of the filter of graph 600A with an extended high frequency range. This extended range discloses pseudo content 7140-1 corresponding to data set 600-1 for a filter having a resonator that does not include PZT or heavy metal layers. Data set 600-2 contains similar pseudo content, however, as shown in graph 700A, its frequency offset is much higher, which is not captured within the range shown. This advantageously enhances the performance of resonators having PZT and heavy metal layers, including by expanding the types of multiplexed filters to which the resonators can be applied.

[0105] Graph 700B shows the reflection coefficient of the filter of graph 600B with an extended high frequency range. This extended range discloses pseudo content 7142-1 corresponding to data set 600-1 for a filter having a resonator that does not include PZT or heavy metal layers. Data set 600-2 contains similar pseudo content, however, as shown in graph 700B, its frequency offset is much higher, which is not captured within the range shown. As previously explained, this advantageously enhances the performance of resonators having PZT and heavy metal layers, including by expanding the types of multiplexed filters to which the resonators can be applied.

[0106] Graph 700C shows the maximum available gain (GMAX) for transmitting a filter having an extended high frequency range.

[0107] Graph 700D shows the power consumed by the filter of graph 600D with an extended high frequency range. This extended range discloses pseudo content 7146-1 corresponding to data set 600-1 for a filter having a resonator that does not include a PZT or heavy metal layer. Data set 600-2 contains similar pseudo content, however, as shown in graph 700B, its frequency offset is much higher and is not captured within the range shown. Figure 7 As shown in , pseudo contents 7146-1, 7142-1 and 7140-1 can be aligned.

[0108] Graph 700E shows the conductance of the series resonator described with reference to graph 600E having an extended high frequency range. Figure 7 As shown in , data set 600-1 includes a peak 6149-1 between passband 6112 and passband 6113. This peak 6149-1 may correspond to the spurious content of the series resonator, i.e., the upper stopband edge. Accordingly, when designing a filter, the series resonator must be configured so that the peak 6149-1 may be between the passbands as shown in order to limit the amount of multiplexing losses that may limit the application of the resonator.

[0109] In contrast, data set 600-2 includes a corresponding peak 6149-2. As shown, this peak 6149-2 is well above all passbands shown in frequency, which ensures that the series resonator can be used in the widest variety of filters and enables easy multiplexing of various frequency bands at the same node. In addition, as shown, the overall amplitude of the out-of-band content of data set 600-2, including peak 6149-2, is greatly reduced compared to data set 600-1. This also helps reduce losses and increase filter performance.

[0110] Graph 700F shows the conductance of the parallel resonator described with reference to graph 600F having an extended high frequency range. Figure 7 As shown in , data set 600-1 contains a peak 6151-1 between passband 6111 and passband 6112. This peak 6151-1 may correspond to the spurious content of the series resonator, namely the upper stopband edge. Therefore, when designing the filter, the series resonator must be configured so that the peak 6151-1 may be between the passbands as shown, which may limit the application of the resonator. The upper stopband edge is so close to the upper band edge of the passband of the filter of the combined frequency band 6110+6111 that it is challenging to design a filter in which the upper stopband edge does not affect the filter performance at the upper band edge.

[0111] In contrast, data set 600-2 includes a corresponding peak 6151-2. As shown, this peak 6151-2 is well above all passbands shown in frequency, which ensures that the series resonator can be used in the widest variety of filters. In addition, as shown, the total amplitude of the out-of-band content of data set 600-2, including peak 6151-2, is greatly reduced compared to data set 600-1. This also helps to reduce losses and increase the performance of the filter. Graph 700G shows the absolute value of the conductance of the series resonator described with reference to graph 600G with an extended high frequency range. This extended range discloses pseudo content 6154-1 corresponding to data set 600-1 for a filter having a resonator that does not include PZT or heavy metal layers. Data set 600-2 includes similar pseudo content, however, as shown in graph 700G, its frequency offset is much higher, which is not captured within the range shown. This advantageously enhances the performance of resonators with PZT and heavy metal layers, including the type of multiplexing situations between different sets of filters that can be applied by extending the resonator.

[0112] Graph 700H shows the absolute value of the conductance of the parallel resonator described with reference to graph 600H having an extended high frequency range. This extended range discloses pseudo content 6157-1 corresponding to data set 600-1 for a filter having a resonator that does not include PZT or heavy metal layers. Data set 600-2 contains similar pseudo content, however, as shown in graph 700H, its frequency offset is much higher, which is not captured within the range shown. This advantageously enhances the performance of resonators having PZT and heavy metal layers, including the type of multiplexing situations between different sets of filters that can be applied by extending the resonators.

[0113] Fig. 8A is a graph showing the relationship between the thickness of the heavy metal layer, the depth of the piezoelectric trench, and the normalized stopband width of a SAW resonator according to aspects of the present disclosure.

[0114] Fig. 8A Includes a graph 800a. Graph 800a includes an x-axis 810a corresponding to the relative thickness of the heavy metal layer of the electrode within the SAW resonator, a y-axis 820a corresponding to the relative depth of the PZT, and a scale 830a corresponding to the stopband width. In some aspects, the thickness of the heavy metal layer and the depth of the piezoelectric groove can be quantified nominally (i.e., in units of actual thickness or depth) or can be quantified relatively (i.e., relative to the thickness of the piezoelectric layer). In this regard, when the terms "thickness" and "depth" are used herein, they can refer to nominal or relative thickness or depth. In some aspects, the stopband width of the SAW resonator can be ideally maximized. In some aspects, the piezoelectric groove depth can be quantified as a relative thickness to the piezoelectric layer 260 ( Figure 2 ) of the thickness of the piezoelectric layer. For example, a value of 0% corresponds to no groove, and a value of 100% may correspond to a fully etched groove such that the depth of the groove is equal to the thickness of the piezoelectric layer 260 ( Figure 2 ). The heavy metal layer thickness can also be quantified as a percentage. For example, the thickness of the heavy metal layer can be expressed as a percentage of the thickness of the heavy metal layer to the thickness 260 of the piezoelectric layer (which can be 500 nm by way of non-limiting example).

[0115] As shown in graph 800a, as the groove depth increases, and as the heavy metal layer thickness increases, the stopband width also increases. The direction of this increase in stopband width is shown by arrow 840a and the marked curve. Dashed line 845a can identify the minimum ideal stopband width of the resonator. For example, a SAW resonator can be ideally designed by selecting the heavy metal layer thickness and the piezoelectric groove depth so that the resulting coordinate is located on one side of the line 845a indicated by arrow 840a.

[0116] Figure 8B is a graph showing the relationship between the thickness of the heavy metal layer, the depth of the piezoelectric trench, and the coupling of a SAW resonator according to aspects of the present disclosure.

[0117] Figure 8B Graph 800b is included. Graph 800b includes an x-axis 810b corresponding to the thickness of the heavy metal layer of the electrode in the SAW resonator, a y-axis 820b corresponding to the depth of the PZT, and a scale 830b corresponding to the coupling. In some aspects, the coupling of the SAW resonator can be ideally maximized. As shown in graph 800b, as the trench depth increases and as the heavy metal layer thickness increases, the coupling decreases. Figure 8B The arrow 840b and the marked curve shown in FIG. 845b show the increasing direction of coupling. The dashed line 845b can identify the minimum ideal coupling of the resonator. For example, the SAW resonator can be ideally designed by selecting the heavy metal layer thickness and the piezoelectric groove depth so that the resulting coordinate is located on one side of the line 845b indicated by the arrow 840b.

[0118] Figure 8C is a graph showing the relationship between the thickness of the heavy metal layer, the depth of the piezoelectric trench, and the quality factor of a SAW resonator according to aspects of the present disclosure.

[0119] Figure 8C Graph 800c is included. Graph 800c includes an x-axis 810c corresponding to the thickness of the heavy metal layer of the electrode in the SAW resonator, a y-axis 820c corresponding to the depth of the PZT, and a scale 830c corresponding to the quality factor. In some aspects, the quality factor of the SAW resonator can be ideally maximized. As shown in graph 800c, the quality factor of the resonator increases toward the maximum point identified by the graph line corresponding to the quality factor 4320. Dashed line 845c can distinguish the lowest ideal quality of the resonator. For example, the SAW resonator can be ideally designed by selecting the heavy metal layer thickness and the piezoelectric groove depth so that the resulting coordinate is located on one side of the line 845c indicated by the arrow 840c.

[0120] As mentioned previously, the combination of piezoelectric grooves and heavy metal layers provides an unexpected increase in the quality factor of SAW resonators, such as Figure 8C For example, as the trench depth increases (shown on the y-axis 820c), the quality factor increases to approximately point 821, after which the quality factor begins to decrease. One of ordinary skill in the art would not currently expect that introducing a heavy metal layer to the electrode after implementing PZT and increasing the depth of the PZT to point 821 would have any positive effect on the quality factor, but rather would cause the quality factor to decrease. However, contrary to current expectations, as Figure 8C As shown, due to the inclusion of a heavy metal layer within the SAW resonator electrode (shown on the x-axis 810c), the quality factor can be additionally increased to point 811, significantly increasing the quality factor of the SAW resonator beyond what was previously believed (i.e., the BodeQ at fp increases from a maximum of approximately 3100 to above 4320).

[0121] Fig.8D FIG. 4 is a graph showing the relationship between the thickness of the heavy metal layer, the depth of the piezoelectric groove, and the capacitance per unit area of ​​a SAW resonator according to aspects of the present disclosure.

[0122] Fig.8D Graph 800d is included. Graph 800d includes an x-axis 810d corresponding to the thickness of the heavy metal layer of the electrode in the SAW resonator, a y-axis 820d corresponding to the depth of the PZT, and a scale 830d corresponding to the unit area capacitance of the resonator at the same resonant frequency fs. In some aspects, the unit area capacitance of the SAW resonator can be ideally maximized. By means of a higher unit area capacitance, a resonator with a specific capacitance target can be realized in a smaller area, which can be beneficial to shrinking the acoustic filter. As shown in graph 800d, as the groove depth increases, the unit area capacitance decreases. Relatively, as the heavy metal layer thickness increases, the unit area capacitance increases. This offset direction of capacitance is shown by arrow 840d and a marked curve. Dashed line 845d can identify the lowest ideal unit area capacitance of the resonator. For example, the SAW resonator can be ideally designed by selecting the heavy metal layer thickness and the piezoelectric groove depth so that the resulting coordinates are located on one side of the line 845d indicated by arrow 840d.

[0123] Fig. 9 is a graph showing ideal piezoelectric trench depth and heavy metal layer thickness according to aspects of the present disclosure. In this regard, selecting the piezoelectric trench depth and heavy metal layer thickness may include a trade-off between the ideal parameters. Fig. 9 As shown, graph 900 may include line 845a, which shows the minimum ideal stopband width, line 845b, which shows the minimum ideal coupling, line 845c, which shows the minimum ideal quality factor, and line 845d, which shows the minimum capacitance per unit area. Graph 900 shows region 950, which is highlighted to identify the region of the graph where all four parameters of graphs 800a-d are optimized. In this regard, the piezoelectric trench depth and heavy metal layer thickness of the SAW resonator can be ideally selected so that the resulting coordinates fall within region 950 of graph 900.

[0124] Fig.10 is a cross-sectional side view of a SAW resonator 1000 having piezoelectric trenches and heavy metal electrodes, wherein the thickness of the heavy metal layer varies between the electrodes, according to aspects of the present disclosure.

[0125] As previously shown, SAW resonators can contain spurious content above and below the fundamental resonant frequency. This results in spurious content outside the passband of the filter, which can interfere with the passband of other filters. Fig.10As shown, adjusting the thickness of the heavy metal layer of different electrodes in the SAW resonator can advantageously reduce the amplitude of the pseudo content. In some aspects, the amplitude of the pseudo content can be additionally reduced by changing or adjusting the spacing between the electrodes (i.e., the distance between the electrodes) and by adjusting the depth of the piezoelectric groove. In this regard, by adjusting any of these parameters (heavy metal layer thickness, spacing, and piezoelectric groove depth), some electrodes can provide advantages at the expense of other performances, while other electrodes provide different advantages. For example, some electrodes in the SAW resonator can be designed to achieve a medium stopband width and provide ideal coupling at the same time, while other electrodes in the same SAW resonator can be designed to achieve an ideal stopband width with medium coupling. This type of change of electrodes can be implemented between different filters on the same die, between different groups of resonators in the same filter (e.g., series resonators or parallel resonators, also known as shunt resonators), or between different electrodes in the same resonator.

[0126] In the example shown, the SAW resonator 1000 includes a carrier substrate 1045, a dielectric layer 1040, a dielectric layer 1035, and a piezoelectric film 1030. The SAW resonator includes electrodes 1026a, 1026b, 1026c, 1026d, and 1026e. Each of these electrodes includes a heavy metal layer of different thickness. For example, the electrode 1026a includes a heavy metal layer of thickness 1028a. The electrode 1026b includes a heavy metal layer of thickness 1028b greater than 1028a. The electrode 1026c includes a heavy metal layer of thickness 1028c greater than 1028a. The electrode 1026d includes a heavy metal layer of thickness 1028d greater than 1028a.

[0127] Fig.11 is a cross-sectional side view of a SAW resonator having a piezoelectric trench and heavy metal electrodes according to aspects of the present disclosure, wherein the depth of the piezoelectric trench is adjusted. In some aspects, the depth of the piezoelectric trench between electrodes can be varied by providing a continuously angled top surface of the piezoelectric trench formed in the piezoelectric layer 1130.

[0128] For example, the SAW resonator 1100 includes a carrier substrate 1145, a dielectric layer 1140, a dielectric layer 1135, and a piezoelectric film 1130. The SAW resonator includes electrodes 1126a, 1126b, 1126c, 1126d, and 1126e. A piezoelectric groove is positioned between each of the electrodes 1126a. For example, a piezoelectric groove 1170a is shown between the electrodes 1126a and 1126b. A piezoelectric groove 1170b is shown between the electrodes 1126b and 1126c. A piezoelectric groove 1170c is shown between the electrodes 1126c and 1126d. A piezoelectric groove 1170d is shown between the electrodes 1126d and 1126e.

[0129] As shown, the depth of the piezoelectric groove 1170 can be varied or adjusted. This variation in the depth of the piezoelectric groove can be achieved because the top surface of the piezoelectric layer 1135 is angled, for example, at an angle 1190. In some aspects, this piezoelectric groove depth adjustment can provide a number of advantages. For example, a smaller thickness of PZT can correspond to an area of ​​higher capacitance per unit area of ​​the resonator, while a larger thickness of PZT corresponds to an area of ​​greater reflectivity. Thus, a PZT with both a larger and smaller depth can provide both advantages within the same resonator. In addition, this groove depth adjustment can provide more continuity from unit cell to unit cell, resulting in less scattering.

[0130] Those skilled in the art will recognize that the above-described apparatus, systems, and methods may be modified in various ways. Accordingly, those of ordinary skill in the art will appreciate that the embodiments covered by the present disclosure are not limited to the specific exemplary embodiments described above. In that regard, although illustrative embodiments have been shown and described, a wide range of modifications, changes, and substitutions are fully contemplated and disclosed in the foregoing. It should be understood that such changes may be made to the foregoing without departing from the scope of the present disclosure. Accordingly, the appended claims should be interpreted in a broad and consistent manner with the present disclosure.

Claims

1. A surface acoustic wave (SAW) resonator device, comprising: a first electrode positioned on an upper surface of the piezoelectric film, the first electrode comprising a plurality of layers, wherein one layer of the plurality of layers is a first heavy metal layer; and A first piezoelectric trench (PZT) is positioned adjacent to the first electrode, the first PZT comprising a recess in the piezoelectric film. 2 . The SAW resonator device according to claim 1 , wherein the heavy metal layer of the first electrode is made of platinum. 3 . The SAW resonator device according to claim 1 , wherein the heavy metal layer of the first electrode is made of tungsten. 4 . The SAW resonator device according to claim 1 , wherein the heavy metal layer of the first electrode is made of gold. 5 . The SAW resonator device of claim 1 , wherein the first electrode further comprises a second heavy metal layer.

6. The SAW resonator device of claim 1, wherein the first heavy metal layer and the second heavy metal layer are separated by a conductive layer.

7. The SAW resonator device of claim 1, wherein the first PZT is positioned between the first electrode and a second electrode, the second electrode being positioned on the upper surface of the piezoelectric film.

8. The SAW resonator device of claim 1, further comprising a second electrode, the second electrode comprising a second heavy metal layer.

9. The SAW resonator device of claim 8, wherein the second electrode comprises a third heavy metal layer. 10 . The SAW resonator device according to claim 1 , wherein the first PZT is an upper PZT formed in the upper surface of the piezoelectric film.

11. The SAW resonator device according to claim 1, wherein the first PZT is a lower PZT formed in a lower surface of the piezoelectric film. 12 . The SAW resonator device according to claim 1 , wherein a first groove depth of the first PZT is equal to or smaller than a thickness of the piezoelectric film.

13. The SAW resonator device of claim 12, wherein a trench depth equal to the thickness of the piezoelectric film corresponds to a fully etched PZT.

14. The SAW resonator device of claim 1, further comprising a second PZT positioned on a side of the first electrode relative to the first PZT within the piezoelectric film.

15. A surface acoustic wave (SAW) resonator device comprising: a plurality of electrodes positioned on an upper surface of the piezoelectric film of a first thickness, each of the plurality of electrodes comprising at least one heavy metal layer; and A plurality of piezoelectric trenches (PZT) are formed in the piezoelectric film between the plurality of electrodes, wherein the plurality of PZTs correspond to regions of the piezoelectric film having a second thickness smaller than the first thickness. 16 . The SAW resonator device of claim 15 , wherein the plurality of electrodes are spaced apart from each other by a first interval, and the plurality of PZTs are spaced apart from each other by a second interval.

17. The SAW resonator device of claim 16, wherein the first pitch is different from the second pitch.

18. The SAW resonator device of claim 15, wherein the plurality of electrodes are spaced apart from each other by an adjusted spacing such that two or more electrodes of a first subset are spaced apart from each other by a first spacing and two or more IDTs of a second subset are spaced apart from each other by a second spacing.

19. A method comprising: A receiving surface acoustic wave (SAW) resonator device, the device comprising: Piezoelectric film; an interdigital transducer comprising a plurality of interposed electrodes positioned on the piezoelectric film, each electrode of the plurality of interposed electrodes comprising a heavy metal layer; and a sacrificial layer positioned on the plurality of interposed electrodes; and An ion beam is applied to the upper surface of the SAW resonator device so that the sacrificial layer is removed and a piezoelectric trench (PZT) is formed between the plurality of interposed electrodes.

20. The method of claim 19, further comprising: patterning the plurality of interposed electrodes on the piezoelectric film; and The sacrificial layer is patterned onto the plurality of interposed electrodes.

21. The method of claim 19, wherein the interposed electrodes and sacrificial material are patterned by sputtering, photolithography, and dry etching.

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