Acoustic resonator having piston mode-like clutch zones generating acoustic transforments through

Abstract

An acoustic resonator with a piston mode patch is disclosed. In one aspect, an interdigital acoustic resonator (300) having a plurality of fingers (308 (1)-308 (N)) or fingers includes a modified piston mode track. In particular, a single piston mode patch (320 (1)-320 (N); 322 (1)-322 (N)), which may be consistent or varied in size, to replace the piston mode track. Selection of patch size allows for suppression of dummy modes to have a smoothing filter passband with low overall insertion loss and minimum ripple. Furthermore, the patch may be manufactured by a monolithic process, which reduces overall production costs, complexity, and cycle duration.

Description

[0001] Priority claim

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 365,218, filed on May 24, 2022, and entitled “ACOUSTIC RESONATOR WITH PISTON MODE PATCHES,” the contents of which are incorporated herein by reference in their entirety. background I. Technical field

[0004] The technology of the present disclosure generally relates to acoustic resonators that can be used, for example, in filters for high frequency signals. II. Background Technology

[0005] In modern society, computing devices are ubiquitous, and more specifically, mobile communication devices are becoming more and more common. The popularity of these mobile communication devices is driven in part by the many functions currently enabled on such devices. The increase in processing power in such devices means that mobile communication devices have evolved from pure communication tools to complex mobile entertainment centers, thereby enhancing the user experience. With the emergence of countless functions available for such devices, the demand for bandwidth for wireless communication is increasing. This demand has caused the evolving cellular standards to steadily increase the baseband of wireless communication operations. Technologies that work for relatively low frequencies may not be suitable for higher frequency applications. Even if certain technologies may be useful at higher frequencies, these technologies may also be complicated by the steady reduction in the size of electronic circuit systems.

[0006] One area where frequency and size challenges have been encountered is in the field of acoustic filters such as surface acoustic wave (SAW) and bulk acoustic wave (BAW) filters that rely on acoustic resonators. Therefore, there is room for innovation in this area. Summary of the invention

[0007] Aspects disclosed in the specific embodiments include an acoustic resonator with a piston mode patch. In an exemplary aspect, an interdigital acoustic resonator having a plurality of fingers or fingers includes a modified piston mode track. In particular, the piston mode track is replaced with a separate piston mode patch, the size of which can be consistent or varied. The choice of patch size allows for suppression of spurious modes to have a smooth filter passband with low overall insertion loss and minimal ripple of the acoustic filter. In addition, the patch can be manufactured by a monolithic process, which reduces overall production cost, complexity, and cycle time.

[0008] In this regard, in one aspect, an acoustic resonator is disclosed. The acoustic resonator includes a piezoelectric substrate. The acoustic resonator also includes a first electrode, the first electrode including a first plurality of fingers. The acoustic resonator also includes a second electrode, the second electrode including a second plurality of fingers interlaced with the first plurality of fingers. The acoustic resonator also includes a plurality of piston mode patches associated with the first plurality of fingers. The plurality of piston mode patches have a duty cycle of less than 100%.

[0009] In another aspect, an acoustic resonator is disclosed. The acoustic resonator includes a piezoelectric substrate. The acoustic resonator also includes a first electrode, the first electrode including a first plurality of fingers. The acoustic resonator also includes a second electrode, the second electrode including a second plurality of fingers interlaced with the first plurality of fingers. The acoustic resonator also includes a first plurality of piston mode patches associated with the first plurality of fingers. The first plurality of piston mode patches have different duty cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1A is a top plan view of a conventional interdigital acoustic resonator having a piston mode track;

[0011] Figure 1B is along Figure 1A The line 1B-1B is intercepted Figure 1A A side elevation cross-sectional view of an acoustic resonator;

[0012] Figure 2 Provides information on various frequencies Figure 1A A series of graphs of transverse mode suppression of an acoustic resonator versus piston mode track thickness and duty cycle;

[0013] Figure 3A is a top plan view of an interdigital acoustic resonator with a pistonic mode patch according to an exemplary aspect of the present disclosure;

[0014] Figure 3B is along Figure 3A The line 3B-3B is intercepted Figure 2 A side elevation cross-sectional view of the acoustic resonator of A; and

[0015] Figure 4 is a top plan view of an interdigital acoustic resonator with pistonic mode patches of different sizes according to an exemplary aspect of the present disclosure. DETAILED DESCRIPTION

[0016] The embodiments set forth below represent information necessary to enable those skilled in the art to practice the embodiments and to illustrate the best mode for practicing the embodiments. Upon reading the following description in light of the accompanying drawings, those skilled in the art will understand the concepts of the present disclosure and will recognize the applications of these concepts not specifically described herein. It should be understood that these concepts and applications fall within the scope of the present disclosure and the appended claims.

[0017] It should be understood that although the terms first, second, etc. can be used to describe various elements in this article, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, without departing from the scope of the present disclosure, the first element can be referred to as the second element, and similarly, the second element can be referred to as the first element. As used herein, the term "and / or" includes any and all combinations of one or more items in the associated listed items.

[0018] It should be understood that when an element such as a layer, region or substrate is referred to as "on another element" or "extending onto another element", it can be directly on another element or directly extended onto another element, or there can also be an intermediate element. On the contrary, when an element is referred to as "directly on another element" or "directly extending onto another element", there is no intermediate element. Similarly, it should be understood that when an element such as a layer, region or substrate is referred to as "above another element" or "extending above another element", it can be directly above another element or directly extend above another element, or there can also be an intermediate element. On the contrary, when an element is referred to as "directly above another element" or "extending directly above another element", there is no intermediate element. It will also be understood that when an element is referred to as "connected" or "coupled" to another element, it can be directly connected or coupled to another element, or there can be an intermediate element. On the contrary, when an element is referred to as "directly connected" or "directly coupled" to another element, there is no intermediate element.

[0019] Relative terms such as "below" or "above" or "up" or "lower" or "horizontal" or "vertical" may be used herein to describe one element, layer or region's relationship to another element, layer or region as illustrated in the figures. It will be understood that these terms and those discussed above are intended to encompass different orientations of the device in addition to the orientation depicted in the figures.

[0020] The terms used herein are only used for the purpose of describing specific embodiments and are not intended to limit the present disclosure. As used herein, unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" are also intended to include the plural forms. It should also be understood that when used herein, the terms "comprises", "comprising", "includes", and / or "including" specify the presence of the features, integers, steps, operations, elements, and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts, and / or groups thereof.

[0021] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present disclosure belongs. It will be further understood that, unless expressly defined herein, the terms used herein should be interpreted as having a meaning consistent with their meaning in the context of this specification and the relevant art, and will not be interpreted in an idealized or overly formal sense.

[0022] Aspects disclosed in the specific embodiments include an acoustic resonator with a piston mode patch. In an exemplary aspect, an interdigital acoustic resonator having a plurality of fingers or fingers includes a modified piston mode track. In particular, the piston mode track is replaced with a separate piston mode patch, the size of which can be consistent or varied. The choice of patch size allows for suppression of spurious modes to have a smooth filter passband with low overall insertion loss and minimal ripple of the acoustic filter. In addition, the patch can be manufactured by a monolithic process, which reduces overall production cost, complexity, and cycle time.

[0023] Before presenting exemplary aspects of the present disclosure, Figure 1A-2 A brief overview of conventional interdigital acoustic resonators with pistonic mode tracks and some of their challenges are discussed. Figure 3A A discussion of exemplary aspects of the disclosure begins.

[0024] Traditionally, acoustic resonators such as surface acoustic wave (SAW) resonators may rely on two interdigital transducers on a piezoelectric material. The transducers are designed with a specific finger width and finger spacing to control the desired frequency of the main mode between the two transducers. In addition to the main mode, there are various pseudo modes that affect the performance of filters using such resonators. One such type of pseudo mode is a transverse mode excited in the lateral direction. In order to limit the acoustic energy in the SAW resonator, a transverse acoustic waveguide is implemented by creating a velocity barrier outside the lateral ends of the fingers to minimize acoustic leakage in the lateral direction. While effectively limiting the acoustic energy, such velocity barriers can produce standing waves, which in turn can appear as peaks within the resonator stopband, resulting in passband ripples in the associated filter.

[0025] One way to reduce these standing waves is the so-called piston mode. The piston mode can be generated by modifying the transverse velocity profile (TVP) and introducing a slow region at the two transverse ends of the finger. This slow region can be specifically formed between the main region and the fast region. A common way to form this slow region is through a piston mode track, such as Figure 1A and 1B Better seen in.

[0026] in this regard, Figure 1A is a top plan view of the SAW resonator 100, and Figure 1B 1B-1B. The SAW resonator 100 may include a piezoelectric substrate 102. The piezoelectric substrate 102 may be bulk or layered and may be formed of materials such as quartz, lithium niobate, lithium tantalate, lanthanum gallium silicate, etc. In addition, in a layered substrate, additional materials including non-piezoelectric materials such as silicon, silicon carbide, silicon dioxide, etc. may be added to the substrate layer stack. The interdigitated structure 104 is positioned on the piezoelectric substrate 102. The SAW resonator 100 may have a longitudinal axis along the x-axis and a lateral transverse axis along the y-axis. The first metal electrode 106 may extend along the longitudinal axis and have fingers 108(1)-108(N) extending along the lateral axis. The second metal electrode 110 may also extend along the longitudinal axis and have fingers 112(1)-112(M) interlaced with the fingers 108(1)-108(N). The signal of interest travels as a surface wave on the piezoelectric substrate 102 along the x-axis between the fingers 108 ( 1 )- 108 (N) and the fingers 112 ( 1 )- 112 (M).

[0027] Most of the signal travels in the main region 114, which is bounded by fast regions 116, 118 close to the electrodes 106, 110. The fast regions 116, 118 minimize acoustic leakage in the lateral direction (i.e., along the y-axis), but can generate lateral standing waves. Overall, the main region 114 and the fast regions 116, 118 form the TVP of the SAW resonator 100.

[0028] The piston mode tracks 120, 122 generate slow regions 124, 126, respectively, to help mitigate lateral standing waves. The generation of such slow regions 124, 126 effectively modifies the TVP of the SAW resonator 100. The piston mode tracks 120, 122 can be positioned above the fingers 108(1)-108(N), 112(1)-112(M) and separated from the fingers by a temperature compensation (TC) dielectric coating 128 (e.g., silicon dioxide (SiO2)). There can also be a passivation layer (not shown) formed of a material such as silicon nitride (Si3N4) on top of the TC dielectric coating 128. The TC dielectric coating 128 can extend above the top surface (z-axis) of the piston mode tracks 120, 122. The piston mode tracks 120, 122 have a height or thickness (along the z-axis, represented as PMR) of 124, 126. h ) and width (along the y-axis), and although they can be different from each other, they are identical to each other in at least some cases. Another variable is the vertical (z-axis) position of the piston mode tracks 120, 122 relative to the fingers 108(1)-108(N), 112(1)-112(M). Similarly, the depth of the piston mode tracks 120, 122 relative to the top surface 130 or the thickness of the TC dielectric coating 128 can vary between different devices, but in a given resonator 100, the depth of the piston mode track 120 will be the same as the depth of the piston mode track 122.

[0029] By optimizing the variables of the piston mode tracks 120, 122, the TVP can be optimized to suppress the transverse modes of the main region. However, even if the transverse modes are suppressed, other pseudo modes may still exist, such as pseudo modes with different wave polarizations (SMPs), because these pseudo modes may require suppression of different TVPs. In addition, the specific TVP selected can induce a hyperbolic mode that is localized and guided in the slow regions 124, 126. This hyperbolic mode can manifest as a peak in the resonator conductance and a decrease in the resonator reflection, which degrades the passband of the filter using the SAW resonator. This degradation may violate the insertion loss design criteria and the passband ripple criteria. The local nature of the hyperbolic mode can also have an impact on the increase in self-heating, the reduction in power handling, and the risk of device failure.

[0030] pass Figure 2This difference in optimization can be better seen in the graphs 200A-200C of FIG, where for a given pitch (x-axis 202A-202C) and duty cycle (y-axis 204A-204C) of the fingers, the optimal points 206A-206C for different PMR thicknesses move around. This moving optimal point makes implementation of a universal optimal PMR challenging because the pitch between resonators and the duty cycle within the filter can vary. While it is possible to vary the PMR thickness, this approach requires multiple different process steps during manufacturing, adds cost and complexity, and is generally undesirable.

[0031] Exemplary aspects of the present disclosure allow for optimization across multiple devices while maintaining a monolithic manufacturing process. This improvement is achieved by introducing a duty cycle to the piston mode track to vary its longitudinal metallization rate. In effect, this separates the piston mode track into discrete piston mode patches that can have variable duty cycle (along the x-axis, but note that the spacing can also be varied). Variations in duty cycle between different electrodes (and corresponding fingers) within a device (e.g., a resonator, filter, multiplexer, etc.) can change the speed characteristics of the slow region and thereby reduce pseudo modes. Optionally, if needed or desired, the width (along the y-axis) can be varied (see Figure 4 ).

[0032] By varying these parameters, the TVP can be modified to optimize for multiple finger pitches and fill factor while keeping the thickness of the patch constant, which allows for monolithic processing. Additionally, the TVP can be varied between different devices (e.g., resonators within a filter) based on pitch / fill factor combinations while always keeping the thickness constant.

[0033] in this regard, Figure 3A and 3B 3 shows a top view and a side view of the resonator 300. Specifically, Figure 3A is a top plan view of the SAW resonator 300, and Figure 3B3B-3B is a cross-sectional view taken along line 3B-3B. SAW resonator 300 may include piezoelectric substrate 302. Piezoelectric substrate 302 may be bulk or layered and may be formed of materials such as quartz, lithium niobate, lithium tantalate, lanthanum gallium silicate, etc. In addition, in a layered substrate, additional materials including non-piezoelectric materials such as silicon, silicon carbide, silicon dioxide, etc. may be added to the substrate layer stack. Interdigitated structure 304 is positioned on piezoelectric substrate 302. SAW resonator 300 may have a longitudinal axis along the x-axis and a lateral transverse axis along the y-axis. First metal electrode 306 may extend along the longitudinal axis and have fingers 308(1)-308(N) extending along the lateral transverse axis. Second metal electrode 310 may also extend along the longitudinal axis and have fingers 312(1)-312(M) interlaced with fingers 308(1)-308(N). The signal of interest travels as a surface wave on the piezoelectric substrate 302 along the x-axis between the fingers 308 ( 1 )- 308 (N) and the fingers 312 ( 1 )- 312 (M).

[0034] Most of the signal travels in the main region 314, which is bounded by fast regions 316, 318 close to the electrodes 306, 310. The fast regions 316, 318 minimize acoustic leakage in the lateral direction (i.e., along the y-axis), but can generate standing waves. Overall, the main region 314 and the fast regions 316, 318 form the TVP of the SAW resonator 300.

[0035] Instead of piston pattern tracks, slow regions 324, 326 are generated by piston pattern patches 320(1)-320(N+M) and 322(1)-322(N+M). That is, piston pattern patches 320(1)-320(N+M) can be on the proximal ends of fingers 312(1)-312(M) and the distal ends of fingers 308(1)-308(N), while piston pattern patches 322(1)-322(N+M) can be on the proximal ends of fingers 308(1)-308(N) and the distal ends of fingers 312(1)-312(M).

[0036] As with the piston mode rails 120, 122, the piston mode patches 320(1)-320(N+M), 322(1)-322(N+M) can be positioned above the fingers 308(1)-308(N), 312(1)-312(M) and separated from the fingers by a TC dielectric coating 328. The TC dielectric coating 328 can extend above the top surface (z-axis) of the piston mode patches 320(1)-320(N+M), 322(1)-322(N+M). As shown, the piston mode patches 320(1)-320(N+M) are uniformly sized relative to each other, have a uniform pitch and fill factor, and include equal spacing between the patches. Likewise, the piston pattern patches 322(1)-322(N+M) are consistently sized relative to one another, have consistent spacing and duty cycle, and include equal spacing between patches. Additionally, the piston pattern patches 320(1)-320(N+M) may be identical to the piston pattern patches 322(1)-322(N+M). Alternatively, the piston pattern patches 320(1)-320(N+M) may differ from the piston pattern patches 322(1)-322(N+M) in some parameters. However, the thickness (along the z-axis) of the piston pattern patches 320(1)-320(N+M) and 322(1)-322(N+M) is consistent, such that the piston pattern patches 320(1)-320(N+M) and 322(1)-322(N+M) may be produced using a monolithic process. Similarly, the vertical positions (along the z-axis) of the piston mode patches 320(1)-320(N+M) and 322(1)-322(N+M) relative to the fingers 310(1)-310(N) and 312(1)-312(M) will be consistent, and the depths of the piston mode patches 320(1)-320(N+M) and 322(1)-322(N+M) relative to the top surface 330 of the TC dielectric coating 328 will also be constant.

[0037] Furthermore, the dimensions along the y-axis are uniform. The piston pattern patches 320(1)-320(N+M) and 322(1)-322(N+M) may be metal or dielectric materials.

[0038] To reiterate, the relevant geometric parameters that can be varied are the duty cycle (in the longitudinal or x-axis direction) of the piston mode patches 320(1)-320(N+M) and 322(1)-322(N+M); the width (in the lateral or y-axis) of the piston mode patches 320(1)-320(N+M) and 322(1)-322(N+M); the vertical position (z-axis, PMP_p) in the TC dielectric coating 328; and the z-height / thickness (PMP_h) of the piston mode patches 320(1)-320(N+M) and 322(1)-322(N+M) (i.e., when the thickness is consistent between the piston mode patches 320(1)-320(N+M) and 322(1)-322(N+M), the actual thickness used can be selected based on design criteria). Changing these parameters effects speed changes in the slow speed regions 324, 326 to achieve the speed reduction required for piston mode operation.

[0039] It will be appreciated that the duty cycle may vary between approximately 1% and 99% (where 100% would be Figure 1A and 1B ), where values ​​between about 30-75% can effectively reduce or suppress some hyperbolic pseudo modes. It should also be noted that in devices with multiple resonators on a single die (i.e., filters, duplexers, N-in-1 multiplexers), each resonator can be parameterized individually to achieve the overall desired result.

[0040] In addition to varying parameters between different resonators in a single device, it is also possible to vary parameters such as Figure 4 Parameters within a single resonator of a SAW resonator 400 shown in FIG. SAW resonator 400 may include a piezoelectric substrate 402. Piezoelectric substrate 402 may be bulk or layered and may be formed of materials such as quartz, lithium niobate, lithium tantalate, lanthanum gallium silicate, and the like. Furthermore, in a layered substrate, additional materials including non-piezoelectric materials such as silicon, silicon carbide, silicon dioxide, and the like may be added to the substrate layer stack. An interdigitated structure 404 is positioned on piezoelectric substrate 402. SAW resonator 400 may have a longitudinal axis along an x-axis and a lateral axis along a y-axis. A first metal electrode 406 may extend along the longitudinal axis and have fingers 408(1)-408(N) extending along the lateral axis. A second metal electrode 410 may also extend along the longitudinal axis and have fingers 412(1)-412(M) interlaced with fingers 408(1)-408(N).

[0041] Instead of piston pattern tracks, slow regions 424, 426 are generated by piston pattern patches 420(1)-420(N+M) and 422(1)-422(N+M). That is, piston pattern patches 420(1)-420(N+M) can be on the proximal ends of fingers 412(1)-412(M) and the distal ends of fingers 408(1)-408(N), while piston pattern patches 422(1)-422(N+M) can be on the proximal ends of fingers 408(1)-408(N) and the distal ends of fingers 412(1)-412(M).

[0042] While the thickness of piston mode patches 420(1)-420(N+M) and 422(1)-422(N+M) is constant, the duty cycle, height (y-axis), and width (x-axis) may be varied or otherwise different to achieve a desired TVP with desired mode suppression.

[0043] It should also be noted that the operation steps described in any of the exemplary aspects herein are described in order to provide examples and discussions. The described operations can be performed in a large number of different orders other than the order shown. In addition, the operations described in a single operation step can actually be performed in many different steps. In addition, one or more operation steps discussed in the exemplary aspects can be combined. It should be understood that it will be readily apparent to those skilled in the art that the operation steps illustrated in the flow chart can be subject to a variety of different modifications. Those skilled in the art will also understand that any of a variety of different technologies and techniques can be used to represent information and signals. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description can be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, light fields or light particles, or any combination thereof.

[0044] The previous description of the disclosure is provided so that any person skilled in the art can make or use the disclosure. Various modifications to the disclosure will be apparent to those skilled in the art, and the general principles defined herein may be applied to other variations. Therefore, the disclosure is not intended to be limited to the examples and designs described herein, but should be given the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An acoustic resonator, comprising: Piezoelectric substrate; a first electrode comprising a first plurality of fingers; a second electrode comprising a second plurality of fingers interlaced with the first plurality of fingers; as well as A plurality of piston mode patches associated with the first plurality of fingers, the plurality of piston mode patches having a duty cycle of less than 100%. 2 . The acoustic resonator of claim 1 , wherein each of the plurality of piston mode patches is positioned over a respective proximal end of the first plurality of fingers.

3. The acoustic resonator of claim 1, wherein each of the plurality of piston mode patches is positioned over a respective distal end of the first plurality of fingers. 4 . The acoustic resonator of claim 1 , wherein each of the plurality of pistonic mode patches comprises a uniform thickness.

5. The acoustic resonator of claim 1, wherein the plurality of pistonic mode patches are configured to create a slow velocity region in the acoustic resonator and contribute to a transverse velocity profile (TVP) to suppress transverse modes.

6. The acoustic resonator of claim 1, wherein the plurality of pistonic mode patches are further configured to suppress spurious modes in the acoustic resonator.

7. The acoustic resonator according to claim 1, further comprising: a temperature compensating (TC) dielectric coating positioned over the first electrode and encapsulating the plurality of piston mode patches; as well as A passivation layer on top of the TC dielectric cladding layer.

8. The acoustic resonator of claim 1, further comprising a second plurality of piston mode patches associated with the second plurality of fingers, the second plurality of piston mode patches having a second duty cycle less than 100%.

9. The acoustic resonator of claim 8, wherein the second duty cycle is the same as the first duty cycle.

10. The acoustic resonator of claim 8, wherein each piston mode patch of the second plurality of piston mode patches is positioned over a respective proximal end of the second plurality of fingers.

11. The acoustic resonator of claim 8, wherein each piston mode patch of the second plurality of piston mode patches is positioned over a respective distal end of the second plurality of fingers.

12. The acoustic resonator according to claim 1, wherein the piezoelectric substrate is a bulk substrate or a layered substrate.

13. The acoustic resonator of claim 1, wherein the plurality of pistonic mode patches comprise metal patches.

14. An acoustic resonator, comprising: Piezoelectric substrate; a first electrode comprising a first plurality of fingers; a second electrode comprising a second plurality of fingers interlaced with the first plurality of fingers; as well as A first plurality of piston mode patches are associated with the first plurality of fingers, the first plurality of piston mode patches having different duty cycles.

15. The acoustic resonator of claim 14, further comprising a second plurality of piston mode patches associated with the second plurality of fingers, the second plurality of piston mode patches having a different duty cycle.

16. The acoustic resonator of claim 14, further comprising: a temperature compensating (TC) dielectric coating positioned over the first electrode and encapsulating the first plurality of piston mode patches; as well as A passivation layer on top of the TC dielectric cladding layer.

17. The acoustic resonator of claim 14, wherein the first plurality of pistonic mode patches comprises a plurality of different heights.

18. The acoustic resonator of claim 14, wherein the first plurality of pistonic mode patches comprises a plurality of different widths.

19. The acoustic resonator of claim 14, wherein the first plurality of pistonic mode patches comprises a uniform thickness.

20. The acoustic resonator of claim 14, wherein the piezoelectric substrate is a bulk substrate or a layered substrate.

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