Vertically coupled TFSAW resonator

Abstract

Aspects of the present disclosure relate to devices, wireless communication devices, methods, and circuitry implementing filters with electro-acoustic vertical coupling. One aspect is a filter that includes a piezoelectric substrate having a first piezoelectric surface and a second piezoelectric surface opposite the first piezoelectric surface. The filter further includes: a first electro-acoustic resonator including a first interdigital transducer (IDT) disposed on or above the first piezoelectric surface of the piezoelectric substrate; and a second electro-acoustic resonator including a second IDT disposed on or above a second piezoelectric surface of the piezoelectric substrate. The second electroacoustic resonator is electrically coupled to the first electroacoustic resonator in series or in parallel.

Description

Technical Field

[0001] Generally speaking, the present disclosure relates to electronic communications and thin film surface acoustic wave (TFSAW) circuits.For example, aspects of the present disclosure relate to surface acoustic wave (SAW) filter circuits in a stacked package with vertical coupling across a piezoelectric substrate. Background Art

[0002] Electronic devices include traditional computing devices such as desktop computers, notebook computers, tablet computers, smart phones, wearable devices such as smart watches, Internet servers, etc. These various electronic devices provide information, entertainment, social interaction, security, safety, productivity, transportation, manufacturing and other services to human users. These various electronic devices rely on wireless communications to perform many of their functions. Wireless communication systems and devices are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcasting, etc. These systems may be able to support communication with multiple users by sharing available system resources (e.g., time, frequency and power). Various aspects of such systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems and orthogonal frequency division multiple access (OFDMA) systems (e.g., long term evolution (LTE) systems or new radio (NR) systems).

[0003] The wireless communication transceivers used in these electronic devices typically include multiple radio frequency (RF) filters for filtering signals for specific frequencies or frequency ranges. In many applications, electroacoustic devices (e.g., "acoustic filters" or "acoustic wave (AW) filters") are used to filter signals. Using piezoelectric materials as the vibration medium, acoustic resonators operate by converting electrical signal waves propagating along an electrical conductor into acoustic waves propagating through the piezoelectric material. Acoustic waves propagate at a speed that is significantly smaller than the propagation speed of electromagnetic waves. Generally, the propagation speed of a wave is proportional to the wavelength of the wave. Therefore, after converting the electrical signal into an acoustic signal, the wavelength of the acoustic signal wave is significantly smaller than the wavelength of the electrical signal wave. The smaller wavelength of the resulting acoustic signal enables the use of smaller filter devices to perform filtering. Smaller filter devices allow acoustic resonators to be used in electronic devices with size constraints, such as the electronic devices listed above (for example, specifically including portable electronic devices such as cellular phones). However, such AW filters are likely to continue to improve as efforts are made to reduce device size and improve device performance. Summary of the Invention

[0004] Disclosed are systems, devices, methods, and computer-readable media for electronic communications, and more particularly, wireless communication devices and circuitry implementing acoustic wave (AW) resonator packages having resonators fabricated for vertical coupling. Aspects may include electroacoustic structures (e.g., electroacoustic resonators using interdigital transducers) configured such that resonators on opposite sides of a piezoelectric substrate (e.g., vertically stacked resonators) can be part of the same filter and can optionally have properties affected by coupling across the piezoelectric substrate.

[0005] According to at least one example, an acoustic wave (AW) filter is provided. The AW filter includes a piezoelectric substrate, comprising: a first piezoelectric layer having a first piezoelectric surface and a second piezoelectric surface opposite to the first piezoelectric surface; a second piezoelectric layer having a third piezoelectric surface and a fourth piezoelectric surface opposite to the third piezoelectric surface; and a spacer layer between the first piezoelectric layer and the second piezoelectric layer, wherein the second piezoelectric surface is opposite to the third piezoelectric surface across the spacer layer; a first interdigital transducer (IDT) formed on the first piezoelectric surface of the first piezoelectric layer; a second IDT formed on the second piezoelectric surface of the first piezoelectric layer; a third IDT formed on the third piezoelectric surface of the second piezoelectric layer; and a fourth IDT formed on the fourth piezoelectric surface of the second piezoelectric layer.

[0006] According to another example, a method for manufacturing an AW filter package is provided. The method includes: creating one or more vias through a piezoelectric substrate, wherein the piezoelectric substrate has a first piezoelectric surface and a second piezoelectric surface opposite the first surface; using the one or more vias to manufacture one or more conductive vias from the first piezoelectric surface to the second piezoelectric surface; manufacturing a first acoustic layer on the first piezoelectric surface of the piezoelectric substrate, wherein the first acoustic layer includes one or more first interdigital transducers (IDTs) and one or more connections from the one or more first IDTs to the one or more conductive vias; using a resist layer to deposit one or more spacers on the first piezoelectric surface of the piezoelectric substrate, to protect the one or more first IDTs; bonding the one or more spacers to a silicon substrate to mount the piezoelectric substrate on the silicon substrate using the one or more spacers; thinning the piezoelectric substrate to a selected thickness by removing material from the second piezoelectric surface of the piezoelectric substrate; and fabricating a second acoustic layer on the second piezoelectric surface of the piezoelectric substrate, wherein the second acoustic layer includes one or more second IDTs connected to the one or more first IDTs via the one or more conductive vias, and wherein the one or more first IDTs and the one or more second IDTs are provided as part of a radio frequency filter circuit.

[0007] According to at least one example, a radio frequency (RF) filter is provided. The RF filter includes: a piezoelectric substrate having a first piezoelectric surface and a second piezoelectric surface opposite the first piezoelectric surface; a first electroacoustic resonator including a first interdigital transducer (IDT) formed on the first piezoelectric surface of the piezoelectric substrate; and a second electroacoustic resonator including a second IDT formed on the second piezoelectric surface of the piezoelectric substrate; wherein the second electroacoustic resonator is electrically coupled to the first electroacoustic resonator in series or in parallel.

[0008] In some aspects, the RF filter operates wherein the thickness of the piezoelectric substrate is less than 20 times the minimum of the pitch of the first IDT and the pitch of the second IDT. In some such aspects, the RF filter operates wherein the thickness of the piezoelectric substrate is greater than 0.1 times the minimum of the pitch of the first IDT and the pitch of the second IDT.

[0009] In some aspects, the RF filter operates wherein the piezoelectric substrate includes a first piezoelectric layer, the first piezoelectric layer including the first surface. In some such aspects, the RF filter operates wherein the first piezoelectric layer also includes the second surface; and wherein the thickness of the first piezoelectric layer is between 0.4 times the minimum of the pitch of the first IDT and the pitch of the second IDT and 2 times the minimum of the pitch of the first IDT and the pitch of the second IDT. In some such aspects, the RF filter operates wherein the piezoelectric substrate also includes: a second piezoelectric layer including the second surface; and a spacer layer located between the first piezoelectric layer and the second piezoelectric layer and in contact with the first piezoelectric layer and the second piezoelectric layer. In some such aspects, the RF filter operates wherein the thickness of the piezoelectric substrate is less than 20 times the minimum of the pitch of the first IDT and the pitch of the second IDT. In some such aspects, the RF filter also operates wherein the third electroacoustic resonator includes a third IDT formed within the spacer layer on a surface of the first piezoelectric layer opposite the first surface. In some such aspects, the RF filter further includes a fourth electroacoustic resonator comprising a fourth IDT formed within the spacer layer on a surface of the second piezoelectric layer opposite the second surface.

[0010] In some such aspects, the RF filter operates wherein the thickness of the first piezoelectric layer is between 0.4 times the minimum of the pitch of the first IDT and the pitch of the third IDT and 2 times the minimum of the pitch of the first IDT and the pitch of the third IDT.

[0011] In some such aspects, the RF filter operates wherein the thickness of the second piezoelectric layer is between 0.4 times the minimum of the pitch of the second IDT and the pitch of the fourth IDT and 2 times the minimum of the pitch of the second IDT and the pitch of the fourth IDT.

[0012] In some such aspects, the RF filter operates wherein the thickness of the spacer layer is less than 10 times the minimum of the pitch of the first IDT and the pitch of the second IDT. In some such aspects, the RF filter operates wherein the thickness of the spacer layer is greater than 10 times the maximum of the pitch of the first IDT and the pitch of the second IDT. In some such aspects, the RF filter operates wherein the thickness of the spacer layer is less than 1.2 times the minimum of the pitch of the first IDT and the pitch of the second IDT. In some such aspects, the RF filter operates wherein the spacer layer comprises a dielectric material. In some such aspects, the RF filter operates wherein the first piezoelectric layer and the second piezoelectric layer are made of the same piezoelectric material.

[0013] In some such aspects, the RF filter includes a silicon substrate, wherein the silicon substrate has a cavity formed in a portion of a surface of the silicon substrate, and wherein the second piezoelectric surface of the piezoelectric substrate shares a boundary with the surface of the silicon substrate, the boundary being aligned such that the second IDT fits within the cavity without contacting the substrate.

[0014] In some aspects, the RF filter further comprises: a plurality of spacers positioned on the first piezoelectric surface of the piezoelectric substrate; and a cap mounted on the plurality of spacers such that the first IDT is positioned in a gap between the first piezoelectric surface of the piezoelectric substrate and the cap.

[0015] In some aspects, the RF filter operates wherein the first and second electroacoustic resonators are part of a ladder filter. In some aspects, the RF filter operates wherein the RF filter is integrated into the RF front-end circuitry of a transceiver. In some aspects, the RF filter operates wherein the filter characteristics of the RF filter are based on electroacoustic coupling between the first and second electroacoustic resonators through the piezoelectric substrate. In some aspects, the RF filter operates wherein the first and second IDTs vertically overlap such that a region on the first piezoelectric surface including the first IDT, across a vertical projection of the piezoelectric substrate, overlaps with a region on the second piezoelectric surface including the second IDT. In some aspects, the RF filter operates wherein the first and second IDTs partially overlap vertically such that at least a threshold portion (e.g., 25%, 50%, etc.) of the first IDT across a vertical projection of the piezoelectric substrate overlaps with a region on the second piezoelectric surface not including the second IDT.

[0016] In some aspects, the RF filter further comprises: an antenna; and processing circuitry, wherein the antenna and the processing circuitry are communicatively coupled via the RF filter, and wherein the RF filter is configured to filter RF signals traveling between the antenna and the processing circuitry.

[0017] In some aspects, the AW filter device or the RF filter is integrated into a device selected from the group consisting of: a set-top box; an entertainment unit; a navigation device; a communication device; a fixed location data unit; a mobile location data unit; a global positioning system (GPS) device; a mobile phone; a cellular phone; a smart phone; a Session Initiation Protocol (SIP) phone; a tablet device; a tablet phone; a server; a computer; a portable computer; a mobile computing device; a wearable computing device; a smart watch; smart glasses; augmented reality (AR) glasses; a desktop computer; a personal digital assistant (PDA); a monitor; a computer monitor; a television; a tuner; a radio unit; a satellite radio unit; a music player; a digital music player; a portable music player; a digital video player; a video player; a digital video disc (DVD) player; a portable digital video player; an automobile; a vehicle component; a vehicle head unit; an avionics system; a drone; and a multirotor helicopter.

[0018] This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used alone to determine the scope of the claimed subject matter. The subject matter should be understood by reference to appropriate portions of the entire specification of this patent, any or all of the drawings, and each claim.

[0019] The foregoing, together with other features and embodiments, will become more apparent after reference to the following description, claims, and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1A is a schematic diagram of a perspective view of an example of an electroacoustic device;

[0021] Figure 1B yes Figure 1A A schematic diagram of a side view of an electroacoustic device;

[0022] Figure 1C is a schematic diagram of a top view of an example of an electrode structure of an example electroacoustic device;

[0023] Figure 2Ais an illustration of a side view of a cross section through ground pins or signal pins of some elements of a stacked AW filter package that may be used with vertically coupled resonators according to aspects described herein;

[0024] Figure 2B is a perspective view of a portion of an AW filter package that can be used with vertically coupled resonators according to various aspects described herein;

[0025] Figure 3 is a cross-sectional side view of some elements of an AW filter package according to various aspects described herein, illustrating vertical waves that can occur using resonators in the AW filter package;

[0026] Figure 4A is a schematic representation of a filter that may be implemented using vertically coupled resonators in accordance with various aspects described herein;

[0027] Figure 4B is a hybrid representation of an electroacoustic resonator that can be vertically coupled and used in filters according to aspects described herein;

[0028] Figure 5A is a cross-sectional side view of a piezoelectric substrate having vertically coupled resonators according to aspects described herein;

[0029] Figure 5B is a top-down view of a piezoelectric substrate with vertically coupled resonators according to various aspects described herein;

[0030] Figure 6A is a cross-sectional side view of a piezoelectric substrate having vertically coupled resonators according to aspects described herein;

[0031] Figure 6B is a top-down view of a piezoelectric substrate with vertically coupled resonators according to various aspects described herein;

[0032] Figure 7 is a cross-sectional side view of a piezoelectric substrate having a plurality of piezoelectric layers and spacer layers, the piezoelectric substrate having vertically coupled resonators according to aspects described herein;

[0033] Figure 8 is a cross-sectional side view of a piezoelectric substrate having multiple piezoelectric layers and spacer layers with additional resonators in the spacer layers and having vertically coupled resonators according to aspects described herein;

[0034] Figure 9 is a cross-sectional side view of an AW filter package including a piezoelectric substrate with vertically coupled resonators according to aspects described herein;

[0035] Figure 10 is a cross-sectional side view of an AW filter package including a piezoelectric substrate with vertically coupled resonators according to aspects described herein;

[0036] Figure 11 is a cross-sectional side view of an AW filter package including a piezoelectric substrate showing details of vertically coupled resonators according to various aspects described herein;

[0037] Figure 12 is a cross-sectional side view of an AW filter package including two piezoelectric layers with vertically coupled resonators according to aspects described herein;

[0038] Figure 13 is a cross-sectional side view of aspects of a piezoelectric substrate that may be used in an AW package according to aspects described herein;

[0039] Figure 14 is a cross-sectional side view of aspects of a piezoelectric substrate that may be used in an AW package according to aspects described herein;

[0040] Figure 15 is a flow chart illustrating a method of producing a vertically coupled filter according to examples described herein;

[0041] Figure 16A is a flow chart illustrating a method of producing a vertically coupled filter according to examples described herein;

[0042] Figure 16B is a flow chart illustrating a method of producing a vertically coupled filter according to examples described herein;

[0043] Figure 17 is a schematic diagram of an environment including an electronic device including a filter that can be implemented using vertically coupled filters according to examples described herein;

[0044] Figure 18 is a block diagram of a wireless communication device including a radio frequency integrated circuit (RFIC) including a vertically coupled filter according to various aspects described herein. DETAILED DESCRIPTION

[0045] The specific embodiments described below in conjunction with the accompanying drawings are intended to be descriptions of exemplary implementations and are not intended to represent the only implementations in which the present invention may be put into practice. The various aspects specifically described herein are provided as examples and should not necessarily be interpreted as being preferred or advantageous over other implementations, including the specifically described implementations and any other implementations apparent from the specific aspects described herein. For the purpose of providing a thorough understanding of the exemplary implementations, the specific embodiments include specific details. In some instances, some devices are shown in block diagram form.

[0046] Electroacoustic devices (also referred to herein as acoustic wave (AW) resonators) are devices that have high-Q performance characteristics at frequencies above several megahertz (MHz) and provide valuable performance in many wireless communication devices. Such resonators in a configuration with an acoustic wave propagating along an interdigital transducer (IDT) on a piezoelectric layer are called surface acoustic wave (SAW) resonators. Various aspects described herein include devices, manufacturing methods, and other aspects associated with SAW devices having IDTs on the top and bottom surfaces of a piezoelectric substrate. The piezoelectric substrate in this disclosure refers to a layer stack comprising at least one piezoelectric layer (and optionally, one or more additional layers), as described in further detail below. At least one piezoelectric layer is arranged in a layer stack so that the top and bottom surfaces of the piezoelectric substrate are the surfaces of the piezoelectric layer. In other words, the top and bottom layers of the multilayer stack of the piezoelectric substrate are piezoelectric layers of the same or different piezoelectric materials. The above positioning can reduce the space used by filters using resonators. Additionally, in some aspects, coupling between resonators on opposing surfaces of a piezoelectric substrate can be used to create complex filters and reduce the thickness, mass, and weight associated with piezoelectric substrates designed to eliminate or minimize vertical coupling between AW resonators.

[0047] Some aspects can be used as described herein to provide additional parameter space for shaping filter functionality when designing devices using AW filters. In some aspects, different polarization modes of vertically coupled IDT pairs can be designed to form passbands, which can allow for tailoring mode characteristics to combine the advantages of both modes. In some aspects, taking coupling into account can allow for reduced filter size while designing a vertical multi-tier packaging that is "almost decoupled" or designed to a size where coupling occurs but is sized to benefit from or provide minimal impact on filter performance.

[0048] Details regarding various aspects of the disclosure are described in more detail below with respect to the accompanying drawings.

[0049] Figure 1ASchematic diagram of a perspective view of an example of an electroacoustic device. The electroacoustic device can be configured as a surface acoustic wave (SAW) resonator or a part of a SAW resonator. In some descriptions herein, the electroacoustic device 100 may be referred to as a SAW resonator, which can be incorporated into an AW filter (e.g., an AW filter with vertical coupling, as further described below). Although the examples described below specifically relate to SAW resonators, the various aspects described herein may be applicable to other types of AW resonators, where coupling may be part of the device design. In addition to the SAW devices described below, in some implementations, the AW filter may use a combination of bulk acoustic waves (BAW) and SAW resonators. Implementations with BAW and SAW resonators may use vertically coupled SAW resonators in combination with additional BAW and / or SAW resonators to complete filters according to the various aspects described herein.

[0050] The electroacoustic device 100 includes an electrode structure 104 on a surface of a piezoelectric layer 102, which may be referred to as an interdigital transducer (IDT). The electrode structure 104 typically includes a first electrode structure and a second electrode structure (e.g., conductive, typically metallic, tapered, etc.), wherein the electrode fingers of the IDT 105 extend from two busbars toward each other, thereby being arranged in an interlocking manner. An electrical signal excited in the electrode structure 104 (e.g., by applying an AC voltage) is converted into an acoustic wave 106, which propagates in a particular direction through the piezoelectric layer 102. The acoustic wave 106 is converted back into an electrical signal and provided as an output. In many applications, the piezoelectric material of each layer (e.g., the piezoelectric layer 102) has a particular crystal orientation such that when the electrode structure 104 is arranged relative to the crystal orientation of the piezoelectric layer 102, the acoustic wave propagates primarily in a direction perpendicular to the direction of the fingers (e.g., parallel to the busbars).

[0051] Figure 1B yes Figure 1ASchematic diagram of an electroacoustic device along a side view of a cross section. The electroacoustic device is shown as having a simplified layer stack including a piezoelectric layer 102, wherein an electrode structure 104 is disposed on or above (the surface of) the piezoelectric layer 102. In some aspects, the electrode structure is disposed above the piezoelectric layer, wherein an intermediate material is disposed between the electrode layer and the piezoelectric layer for power, durability, and / or coupling modification (e.g., Al2O3). In other aspects, other stacks or material layers can be used as part of the device, wherein a piezoelectric substrate (e.g., including one or more piezoelectric layers) is combined with an electrode structure disposed on or above the piezoelectric substrate using optional additional layers. In some aspects, the electrode structure 104 is conductive and can be formed from a metallic material. The piezoelectric layer can be formed from a variety of piezoelectric materials, such as quartz, lithium tantalate (LiTaO3), lithium niobate (LiNbO3), doped variants of these materials, or other piezoelectric materials. It should be understood that more complex layer stacks (e.g., two or more layers, etc.) including layers of various materials (e.g., different piezoelectric materials) are possible within the stack. For example, optionally, a temperature compensation layer 108 (represented by a dashed line) can be disposed above (e.g., covering or located above) the electrode structure 104. As another example, the piezoelectric layer 102 can be part of a multilayer substrate that can include another base substrate, such as a silicon substrate (e.g., for a thin film SAW device, the piezoelectric layer can be formed on a temperature compensation layer, a charge trapping layer, a high resistivity layer (e.g., silicon), or other such layer stack). The piezoelectric layer 102 can be extended to have multiple interconnected electrode structures disposed thereon to form a multi-resonator filter or provide multiple filters. Although in Figure 1B 104, but when provided as an integrated circuit component, a cap layer (e.g., such as Figure 10 Block 1090, Figure 11 The capping layer is applied so that a cavity is formed between the electrode structure 104 and the lower surface of the capping layer. Electrical vias or bumps that allow the AW component to be electrically connected to connections on the substrate (e.g., via flip chip or other technology) may also be included.

[0052] Figure 1C is a schematic diagram of a top view of an example of an electroacoustic device including an electrode structure 104 and an end reflector. Figure 1CGenerally, a dual-port configuration of an electroacoustic (e.g., AW) device is shown. The electrode structure 104 has an IDT that includes a first busbar 122 (e.g., a first conductive segment or rail) electrically connected to a first terminal 120 and a second busbar 124 (e.g., a second conductive segment or rail) spaced apart from the first busbar 122 and connected to a second terminal 130. A plurality of conductive fingers 126 are connected to the first busbar 122 or the second busbar 124 in a cross-shaped manner. The fingers 126 connected to the first busbar 122 extend toward the second busbar 124 but are not connected to the second busbar 124, such that a small gap exists between the ends of the fingers 126 and the second busbar 124. Similarly, the fingers 126 connected to the second busbar 124 extend toward the first busbar 122 but are not connected to the first busbar 122, such that a small gap exists between the ends of the fingers 126 and the first busbar 122.

[0053] Along busbars 122 and 124, there is an overlap region including a central region where a portion of one finger overlaps a portion of an adjacent finger (as shown by central region 125). Central region 125 including the overlap can be referred to as an aperture, track, or active region, where an electric field is generated between fingers 126 to cause acoustic waves to propagate in piezoelectric layer 102. The periodicity of fingers 126 is referred to as the pitch of the IDT. Pitch can be indicated in various ways. For example, in some aspects, pitch can correspond to the size of the distance between fingers in central region 125. This distance can be defined, for example, as the distance between the center points of each of the fingers (and when the fingers have uniform thickness, this distance can typically be measured between the right (or left) edge of one finger and the corresponding right (or left) edge of the adjacent finger). As described herein, a "higher" pitch refers to a region of the IDT where electrode fingers have a larger distance between adjacent electrode fingers, while a "lower" pitch refers to a region of the IDT where electrode fingers have a lower distance between adjacent electrode fingers. In some aspects, the average of the distances between adjacent fingers can be used for the pitch. Having a given pitch characteristic for a section of the IDT having electrode fingers that differs from the pitch characteristics of other sections of the IDT allows for selection or control of signals (e.g., waves) propagating through the IDT. The frequency at which the piezoelectric material vibrates is the self-resonance (also referred to as the "primary resonance") frequency of the electrode structure 104. This frequency is determined, at least in part, by the pitch of the IDT 105 and other characteristics of the electroacoustic device 100.

[0054] In some examples, the pitch characteristics of a segment of an IDT can be a constant pitch, where the pitch does not vary significantly across the IDT segment (e.g., the variation is within manufacturing tolerances and is designed for a constant average pitch). In other examples, the pitch characteristics of an IDT segment can include a "chirped" pitch, where the pitch varies in a predefined manner across the IDT segment. For example, a chirped pitch can include an IDT segment where the pitch is designed to vary linearly across the IDT segment, such that the pitch at one end of the IDT segment is at a first value, the pitch at the opposite end of the IDT segment is at a second, different value, and the pitch (e.g., the distance between the electrode fingers) varies linearly between the two ends of the IDT segment. In other examples, a nonlinear variation of the pitch value across the IDT segment can be used. By combining IDT sections with different pitch characteristics (e.g., a constant pitch at a first value and a constant pitch at a second value, or a constant pitch at a first value in one IDT section and a chirped pitch across a second IDT section), the resonator characteristics can be tailored for a given performance in a circuit, where multiple AW resonators can be combined together to form a filter, as shown in the following example. Figure 10 Described in .

[0055] The IDT 105 is arranged between two reflectors 128, which reflect the acoustic waves back to the IDT 105 for conversion to electrical signals via the IDT 105 in the illustrated configuration and to prevent losses (e.g., confinement and prevention of escaping acoustic waves). Each reflector 128 has a grating structure of two busbars and conductive fingers, with each conductive finger connected to the two busbars. The pitch of the reflectors can be similar or identical to the pitch of the IDT 105 (at the respective ends of the IDT) to reflect acoustic waves in the resonant frequency range, and many configurations are possible.

[0056] When converted back into an electrical signal, the admittance or reactance measured between the two terminals (eg, first terminal 120 and second terminal 130 ) serves as a signal for the electroacoustic device 100 and allows the electroacoustic device 100 to function as part of a communication device in a signal path.

[0057] Additionally, while standard IDT arrangements isolate different IDTs to prevent acoustic waves from outside a single IDT from having a significant effect on the operation of a given resonator, the various aspects described herein include configurations in which waves can reflect and interact not only within a single IDT (e.g., IDT 105) of a SAW resonator, but also with one or more additional IDTs on the opposite side of the piezoelectric substrate. This electroacoustic interaction between IDTs can be configured as part of the filter characteristics of a filter that includes vertically coupled IDTs on both sides of a piezoelectric substrate. This coupling across the piezoelectric substrate can allow for complex filter characteristics while reducing the size of the AW structure (e.g., due to less area usage and a thinner substrate).

[0058] Figure 2A is a diagram of a cross-sectional side view of a stacked AW filter package 200 that includes a first AW resonator circuit 202 (e.g., a SAW resonator circuit as described above) on a first substrate 204 and a second AW resonator circuit 206 on a second substrate 208 to provide electro-acoustic resonators that can be coupled together to form a filter circuit. The AW resonator circuits 202 and 206 may include vertically coupled resonators as described herein and may be implemented using similar manufacturing and packaging structures as the stacked AW filter package 200. In some implementations, as will be described below, such AW resonator circuits 202 and 206 may be connected via a redistribution layer and a shared substrate, rather than as described above. Figure 2A Each of the first substrate 204 and the second substrate 208 may have a structure similar to Figure 1A-1C The additional electro-acoustic devices of the electro-acoustic device 100 (eg, in addition to the AW resonator circuits 202 and 206 ) are used as part of the AW filter circuit. Figure 2A is a side view of a cross section through the ground pad 242 of the stacked AW filter package 200 . Figure 2B is a perspective view of a cross section through signal pad 246 of stacked AW filter package 200. In some aspects, ground pad 242 can be a signal pad, and signal pad 246 can be a ground pad. In further aspects, all combinations of signal / ground pads are possible, and Figure 2A and Figure 2B The specific implementation of is an illustrative example of one possible cross section.

[0059] In some implementations, substrates 204 and 208 may include a piezoelectric layer as part of the described substrate. In other implementations, the AW resonator circuits 202 and 206 may include a piezoelectric layer that may or may not be integrated with the respective substrates 204 and 208. In some implementations, the first AW resonator circuit 202 and the second AW resonator circuit 206 may each refer to an electrode structure of a resonator circuit, where each electrode structure is positioned relative to the piezoelectric layer. The piezoelectric layer may serve as a surface for the electrode structure of the AW resonator circuits 202 and 206, and in various aspects, the piezoelectric layer may be part of the AW resonator circuit 202 or 206 or part of the respective substrates 204, 208.

[0060] like Figure 2A As shown, the AW filter package 200 includes a first AW resonator circuit 202 on a first substrate 204 and a second AW resonator circuit 206 on a second substrate 208. The first AW resonator circuit 202 is stacked on the second AW resonator circuit 206 in a vertical direction (e.g., z-axis direction). The first AW resonator circuit 202 and the second AW resonator circuit 206 are collectively referred to herein as "resonator circuits 202, 206". The first AW resonator circuit 202 and the second AW resonator circuit 206 may each correspond to Figure 1A-1C AW circuit in , but may also be any other type or configuration of AW filter circuit (e.g., separate or shared filter structures, such as in Figure 10 ). Therefore, in Figure 2A or Figure 2B Details of the first AW resonator circuit 202 and the second AW resonator circuit 206 (e.g., the specific AW resonator coupling used to form a given filter) are not shown. The resonator circuits 202, 206 include a first metal interconnect (as described above in Figure 1A-1C discussed in Figures 9-14 ), which is used to receive an input RF signal from an external circuit (e.g., an antenna) and provide a filtered RF signal as an output to the external circuit along a signal path that includes filtering provided by the connection of the AW resonator and other circuit elements.

[0061] exist Figure 2AIn the AW filter package 200 in FIG. 1 , the first AW resonator circuit 202 is disposed on a first surface 212 of a first substrate 204. For example, the first substrate 204 may be formed of a semiconductor material (e.g., silicon) formed in a wafer to take advantage of advances and low costs in semiconductor processing technology, wherein the resonator is placed on a piezoelectric layer. As mentioned above, the piezoelectric layer may be provided on or as part of at least a portion of the first substrate 204 (e.g., provided on or above the semiconductor material). The second surface 214 is opposite the first surface 212. Figure 2A In the orientation of the AW filter package 200 shown in FIG, the first surface 212 may also be referred to as the top surface 212, and the second surface 214 may also be referred to as the bottom surface 214 of the first substrate 204, because the top surface 212 is disposed above the bottom surface 214 in the vertical direction (z-axis direction).

[0062] The second AW resonator circuit 206 is disposed on a third surface 216 of the second substrate 208. In the AW filter package 200, the first substrate 204 is stacked above the second substrate 208 to reduce the area occupied by the AW filter circuits on the first and second substrates 204, 208. The second substrate 208 (e.g., when serving as a carrier material) may also be formed from a semiconductor material (e.g., silicon) formed in a wafer, for example, to leverage advances in semiconductor processing technology and lower costs, with the AW resonator being positioned on the piezoelectric layer as described above. In this regard, the first substrate 204 may be stacked above the second substrate 208 (e.g., in a vertical z-axis direction), or the second substrate 208 may be stacked below the first substrate 204 (e.g., in a vertical z-axis direction). A frame 218 is disposed between the second surface 214 of the first substrate 204 and the surface 216 of the second substrate 208. The frame 218 can be a polymer support structure configured around the edges of the substrates 204 and 208, wherein the frame creates a cavity 220 in which the AW resonator and other circuitry are located. The polymer element is configured to prevent the AW resonator circuit or other components (e.g., AW resonator circuit 206) in the cavity from contacting the substrate at the top of the corresponding cavity. The frame 218 can provide both mechanical support for the relative positioning of the first substrate 204 and the second substrate 208 and structural protection for the components (e.g., AW resonator) within the cavity 220. The second AW resonator circuit 206 is disposed in the cavity 220 between the bottom surface 214 of the first substrate 204 and the top surface 216 of the second substrate 208. The cavity 220 can also contain air or a gas.

[0063] Figure 2AThe AW filter package 200 in the embodiment of the present invention further includes a capping substrate 222 disposed on the first surface 212 of the first substrate 204. The capping substrate 222 is separated from the first surface 212 by a frame 224 to form a cavity 226 in which the first AW resonator circuit 202 is disposed. The capping substrate 222 provides a cap to the cavity 226 in the same manner as the first substrate 204 provides a cap to the cavity 220. The cavity 226 also includes air or another gas surrounding the first AW resonator circuit 202. For example, the capping substrate 222 can be glass or another non-conductive substrate material. The stacked AW filter package 200 further includes contacts 228A, 228B (e.g., at Figure 2B 2 (shown in FIG), which is disposed on metal interconnects 230A, 230B on a contact surface 232 of the cap substrate 222 for connecting the second AW resonator circuit 206 to external circuitry. Contacts 228A, 228B are coupled to the second AW resonator circuit 206 via metal interconnects 230A, 230B formed in a metallization (redistribution) layer 236. The metallization layer 236 extends from the contact surface 232 onto a side surface 238 of the cap substrate 222 and onto a side surface 240 of the first substrate 204. The side surface 240 extends between the first surface 212 and the second surface 214 of the first substrate 204. Additional contacts (not shown) may be disposed on the contact surface 232 for connecting the first AW resonator circuit 202 to external circuitry (e.g., processing circuitry, an antenna, etc.).

[0064] exist Figure 2A In the stacked AW filter package 200 in FIG, the first AW resonator circuit 202 can filter a first RF signal, while the second AW resonator circuit 206 filters another RF signal. In other aspects, the first AW resonator circuit 202 and the second AW resonator circuit 206 can filter the same signal (e.g., using resonators in the same ladder network). In addition, as described above, each AW resonator circuit 202, 206 can include one or more resonators connected in one or more filter circuits, depending on the device configuration used to filter the RF signal in the communication device. In some examples, the resonator circuits 202, 206 are not electrically associated with each other in operation, but in other examples, both the resonator circuits 202, 206 can be coupled to the same antenna (not shown) that is coupled to the AW filter package 200. Thus, the resonator circuits 202, 206 can provide different filters for the same RF signal, or can filter different RF signals. In various implementations, Figure 2A 、 Figure 2B and Figure 3 A resonator circuit can be implemented using a piezoelectric substrate with vertically coupled resonators as described below.

[0065] Figure 2B is Figure 2A A perspective view of the AW filter package 200 is shown in FIG. Figure 2B To more clearly illustrate certain aspects of the AW filter package 200, in particular, conductive (e.g., metal) interconnects 230A, 230B are shown on the side surface 240 of the first substrate 204. As shown in this non-limiting example, the metal interconnect 230A extends from the contact 228A and is disposed on the side surface 238 of the cap substrate 222, on the frame 224, on the first surface 212 of the first substrate 204, and can be coupled to a portion 244 of a signal path for generating a filter having an AW resonator (e.g., resonator circuits 202, 206). The metal interconnect 230A couples a portion of a ground or signal path to a corresponding element of the circuit (e.g., coupling the second AW resonator circuit 206 to the contact 228A). For example, the contact 228A can receive a ground voltage V from an external circuit in the mobile device. SS A metal interconnect 230B extends from the contact 228B and is disposed on the side surface 238 of the cap substrate 222, the frame 224, the insulating layer 248, the frame 218, and the signal pad 246. The metal interconnect 230B couples the signal pad 246 of the AW resonator circuit 206 to the contact 228B, which can be coupled to at least one of the first AW resonator circuit 202 and an external circuit.

[0066] Figure 3 is a cross-sectional side view of some elements of the stacked AW filter package 300 illustrating vertical waves (eg, wave components 362 and 364 ) that may occur as part of SAW resonator operation. Figure 3 The cross section of FIG. 3 shows an edge portion of the stacked AW filter package 300 on the left, and a center portion on the right, which may continue to have additional AW resonator circuits and walls. Although the upper cavity 370 is shown as having only a single AW resonator circuit 350, and the lower cavity 380 is shown as having two AW resonator circuits 352 and 354, the complete layer stack, not shown, may have additional AW resonator circuits at different locations not shown (e.g., at different depth slices, or further along the slice to the right in the not shown section of the stacked AW filter package 300). As noted above, the AW resonator circuits 350, 352, and 354 include, for example, Figure 1A 、 Figure 1B and Figure 1CIn various implementations, the AW resonator circuits 350, 352, and 354 may include a piezoelectric layer on which the corresponding electrode structures are located, or the electrode structures may be located on a piezoelectric layer that is part of a corresponding substrate (e.g., substrates 320 and 330) for each AW resonator circuit 350, 352, 354.

[0067] The stacked AW filter package may also include contacts 302, a protective cap 310, and spacers 340, 342, 344, 346, and 348, which may provide mechanical support for the substrate and suppress vertical waves from exceeding the resonator circuit.

[0068] The structure shown for implementing a surface acoustic wave (SAW) filter includes wave modes concentrated at the surface of a piezoelectric substrate, as described above with respect to Figure 1A-1C As described. Such a resonator also includes vertical wave propagation outside the surface area of ​​the piezoelectric substrate. Such waves can propagate into the body of the piezoelectric material and the substrate supporting the illustrated resonator elements (e.g., acoustic signals entering the substrate from resonator elements such as IDTs, etc.). Propagation into the substrate can be a parasitic effect that deteriorates overall filter performance (e.g., due to increased losses in the carrier aggregation counter band, higher signal leakage, etc.). If the AW resonator circuits 350, 352, and 354 include an IDT only on the top surface, with the bottom surface directly coupled to the substrate (e.g., a silicon substrate, such as the first substrate 320 or the second substrate 330), the vertical wave components 362 and 364 can be emitted into the silicon substrate. However, the aspects described herein may include AW resonator circuits 350, 352, and 354 configured to have IDTs and associated resonators on both sides (e.g., top and bottom) of each AW resonator circuit. Instead of the vertical waves becoming noise as possible body radiation waves reflected from the surface of the silicon substrate, vertical waves can be part of the vertical coupling characteristics designed between resonators in filters designed to integrate resonators into AW resonator circuits. Any leakage of such waves can be addressed using damping materials or other aspects of AW filter design.

[0069] Figure 4A 400A is a schematic representation of a filter that can employ the disclosed vertically coupled resonators according to examples described herein. Specifically, the filter includes a ladder-type arrangement of acoustic SAW resonators Rs, Rp (where Rs is a series resonator and Rp is a parallel resonator). The disclosed stacked SAW filter can couple SAW resonators (e.g., 410, 420, etc.) to implement the filter while including the described elements for vertical coupling across the piezoelectric substrate used to implement the filter.

[0070] The ladder-type structure of the filter includes multiple basic sections BS. Each basic section BS includes at least one series resonator Rs and at least one parallel resonator Rp. Basic sections BS can be connected in series, as many as necessary to achieve the desired selectivity. Series resonators Rs belonging to adjacent basic sections BS can be combined into a common series resonator Rs, while parallel resonators Rp can also be combined if they are directly adjacent and belong to different basic sections BS. One basic section BS provides the basic filter. More basic sections BS are added to provide sufficient selectivity. Figure 4A The filter includes at least one basic section shown, which includes a series resonator 410 and a parallel resonator 420. As described herein, the series resonator 410 and the parallel resonator 420 can be implemented as vertically coupled resonators on opposite sides of a shared piezoelectric substrate.

[0071] Figure 4B 4 is a hybrid representation 400B of electroacoustic resonators that can be vertically coupled and used in filters according to various aspects described herein. As shown in hybrid representation 400B of the filter, each elementary segment includes an IDT comprised of electrode fingers as described above. In previous systems, each such IDT for a SAW resonator is configured on the top surface of a piezoelectric layer and / or positioned to maintain acoustic wave interaction between such IDTs at a level where coupling between the IDTs does not affect the performance of the filter. For example, resonator 410 and resonator 420 (e.g., each resonator including an IDT comprised of electrode fingers formed on the surface of a piezoelectric layer) would previously be positioned to limit coupling between resonator 410 and resonator 420. In various aspects described herein, resonator 410 and resonator 420 can be located on opposite sides of a piezoelectric substrate and electrically coupled as part of a single filter. In some implementations, the elementary segments of the ladder filter can be positioned for coupling between different resonators. In other implementations, coupling can be configured between resonators in different segments, or composite coupling between more than two resonators can be configured to achieve the desired response characteristics for a given filter.

[0072] Figure 5A5 is a cross-sectional side view 500A of a device having vertically coupled resonators according to various aspects described herein. The device includes a piezoelectric substrate 530 (e.g., a single piezoelectric layer), a resonator 410 (formed by an IDT and a corresponding piezoelectric substrate 530), and a resonator 420 (e.g., a cross-sectional cutaway view of electrode fingers for the IDTs of resonators 410 and 420 is shown). The piezoelectric substrate 530 has a top surface 531, with the IDT of resonator 410 formed on or above the top surface 531 of the piezoelectric substrate 530. Similarly, the piezoelectric substrate 530 also has a bottom surface 532, with the IDT of resonator 420 formed on or above the bottom surface 532 (e.g., relative to the center of the piezoelectric substrate). As described herein, an IDT can be referred to as being disposed or formed above a piezoelectric surface relative to a central portion of a piezoelectric layer or substrate, such that both the IDT of resonator 410 and the IDT of resonator 420 can be referred to as being disposed or formed above the respective piezoelectric surfaces relative to the center of the piezoelectric substrate 530. Similar IDT and piezoelectric positioning can be referred to as the IDT relative to the piezoelectric layer having a body or core with a piezoelectric surface formed on, above, or on the piezoelectric surface. According to any aspect described herein, such positioning can include arranging the IDT with an intermediate layer between the IDT and the piezoelectric surface.

[0073] Figure 5B 5 is a top-down view 500B of a device with vertically coupled resonators according to various aspects described herein. Top-down view 500B shows top surface 531 of substrate 530 and resonator 410. Resonator 420 is on the bottom side of the device and is not visible from top-down view 500B.

[0074] Figure 5A The signal 562 shown is the surface signal of the resonator 410, which is the main signal path of the excitation wave in the SAW resonator. The signal 563 shown is the surface signal of the resonator 420. In the case of surface-bound acoustic waves, these waves decay exponentially into the substrate, so that in the case of a thick piezoelectric substrate 530 (for example, a thickness 533 of about 10λ or more), the resonator 420 cannot detect a significant portion of the signal 562. However, for a thin piezoelectric substrate 530 or for leaked acoustic waves, a portion of the signal 562 can be detected by the resonator 420 and an electrical output signal is generated at the resonator 420. Therefore, the resonator 420 is coupled to the resonator 410 via the acoustic wave linked to the surface signal 562. Similarly, if the piezoelectric substrate is thin enough, the surface signal 563 can contribute to the coupling between the resonator 410 and the resonator 420.

[0075] Furthermore, coupling between resonators 410 and 420 can be generated by acoustic waves propagating in a perpendicular or diagonal direction along signal path 564. Such waves can be excited by resonator 410 and detected by resonator 420, such that an electrical input signal at resonator 410 results in an electrical output signal at resonator 420, and vice versa. The amount of coupling between resonators 410 and 420 depends on the thickness of the piezoelectric substrate, the polarization of the acoustic waves linked to surface signals 562 and 563, the design of resonators 410 and 420, the horizontal offset between the resonators, and other geometric parameters.

[0076] When the electroacoustic coupling between resonators 410 and 420 is included as a design consideration for a filter including resonators 410 and 420, a composite filter response can be generated while reducing the size of the filter. In some implementations, the efficiency of the device can be improved because the energy in signal path 564 is used and directed as part of the filter output rather than being dissipated.

[0077] In some systems, resonators are fabricated under the assumption that the wave fields excited by the inputs of the resonators are decoupled. In various aspects described herein, such an assumption is not valid because the interaction between the excited wave fields (e.g., coupling between resonators) can be sufficient to affect performance. In a model of two IDTs (e.g., the IDTs of resonators 410 and 420), the frequency-dependent wave excitation fields can be described as Ψ( x , f) IDT 1 and Ψ( x , f) IDT 2 , where x represents the position vector and f represents the frequency. For a decoupled system, since Ψ( x , f) IDT 1 And Ψ( x , f) IDT 2 is assumed to be 0 or close to 0 (when the other is not close to zero), so the total wave excitation field around the resonator can be approximated as: (1)Ψ tot =Ψ IDT 1 +Ψ IDT 2 However, for coupled systems this assumption is no longer valid, but the total wave excitation field becomes a combination that is not a simple superposition of wave fields (due to nonlinear effects) and can be described as: (2)Ψ tot =Ψ IDT 1+IDT2 This combined wave field for coupled IDTs (e.g., in vertically coupled resonators), while having a more complex filter function, can provide filtering for some applications while allowing design flexibility with reduced space usage and compact interconnects between resonators. Additionally, while Equation 2 above describes the case of two coupled IDTs, the same composite combination can be applied to more than two IDTs and more than two resonators positioned in vertical or other composite couplings, as described below.

[0078] In some aspects described herein, Ψ( x , f) IDT 2 is generated by an electrical input signal connected to a first IDT (eg, the IDT of the resonator 410), and Ψ( x , f) IDT 2 is generated by an electrical input signal connected to a second IDT (eg, the IDT of resonator 420). The non-vanishing field Ψ( x , f) IDT 1 The output signal at the first IDT is caused by the non-vanishing field Ψ( x , f) IDT 2 An output signal is caused at the second IDT.

[0079] In the case of uncoupled IDTs (e.g., the IDTs of resonators 410 and 420), the field Ψ ( x , f) IDT 1 The output signal of the second IDT is zero or close to zero near the second IDT, so that any input signal fed into the first IDT does not cause a significant output signal at the second IDT. Therefore, the output signal of the second IDT is independent of the input at the first IDT, and vice versa. Furthermore, the output signal of the second IDT does not depend on the geometry, electrode structure, excitation state, or even the existence of the first IDT at all.

[0080] However, for the coupled IDT, the two fields Ψ( x , f) IDT 1 and Ψ( x , f) IDT 2 Covering both IDTs. Therefore, any input signal at the first IDT causes an output at the second IDT, and vice versa. Therefore, the output of the second IDT depends on both the input signal at the second IDT and the input signal at the first IDT.

[0081] In such a coupled system, we can define the coupling factor as the field Ψ( x , f) IDT1 The amplitude at the location of the second IDT is compared to the field Ψ( x , f) IDT 1The magnitude at the location of the first IDT. Similarly, the coupling factor can be defined as the field Ψ( x , f) IDT 2 The amplitude at the location of the first IDT is compared to the field Ψ( x , f) IDT 2 Alternatively, for a given input signal at either the first or second IDT, we can define the coupling factor as the ratio of the output signal at the second IDT to the output signal at the first IDT.

[0082] Spatial superposition of electroacoustic wave fields for coupled IDTs (e.g., in vertically coupled resonators) can provide more complex transmission functions and filtering for some applications while allowing design flexibility with reduced space usage and compact interconnections between resonators. Additionally, while the previous paragraphs describe a case with two coupled IDTs, the same complex combination can be applied to more than two IDTs and more than two resonators positioned in vertical or other complex couplings, as described below.

[0083] Figure 6A is a cross-sectional side view 600A of a device having vertically coupled resonators according to various aspects described herein. Figure 6B FIG. 600B is a top-down view of the device. Figure 5A and Figure 5B The device in Figure 6A and Figure 6B The device in FIG. 6 includes a piezoelectric substrate 630 having a top surface 631 and a bottom surface 632. In the illustrated implementation of the device, although the resonator 410 is provided on the top surface 631 and the resonator 420 is provided on (below) the bottom surface 632, Figure 6A and Figure 6B In the device shown in FIG. 5 , the position of the resonator 410 on the top surface 631 is offset (in the direction of signal propagation) from the position of the resonator 420 on the bottom surface 632. Figure 5B In top-down view 500B of the device in FIG, resonator 420 would be directly below resonator 410 on the corresponding opposing surface of piezoelectric substrate 530. In contrast, in top-down view 600B, there is additional surface area because there is no vertical overlap between resonator 410 and resonator 420.

[0084] In addition to illustrating the piezoelectric substrate 630, the cross-sectional side view 600A also illustrates the thickness 633 of the piezoelectric substrate 630 and the offset (e.g., in the labeled x-direction) between the resonators 410 and 420. Figure 5A and Figure 5BIn the device in FIG. 5 , resonator 410 and resonator 420 have associated signal paths. Resonator 410 is associated with signal 662, and resonator 420 is associated with signal 663. Figure 5A and Figure 5B As with the devices in FIG. 6 , signals 662 and 663 are based on the coupling between resonators 410 and 420 within the filter structure, which can include not only the resonator response to the signals for the respective IDTs, but also the effects of electroacoustic coupling across the piezoelectric substrate 630 (e.g., shown as signal path 664). In other configurations with substrate layers and thicknesses, and in other aspects with different placement and overlap of the resonator IDT structures, other signals may exist. Vertical (e.g., labeled z-direction) coupling between resonators 410 and 420 additionally results in signal path 664. Due to the lack of vertical overlap, the coupling between resonators 410 and 420 is lower, and the strength of the signal in signal path 664 will be less than the strength of the signal in signal path 564. Therefore, in addition to configuring the coupling of the resonators based on the thickness of the piezoelectric substrate (e.g., thickness 633 or thickness 533), the amount of coupling between the resonators can also be adjusted in a design configuration based on the amount of vertical overlap between the resonator IDTs on opposite sides of the piezoelectric substrate. Shifting resonator 420 to the left along second surface 632 (e.g., in the negative x-direction) will result in increased coupling between resonators 410 and 420, while shifting the resonators away from each other (e.g., shifting resonator 410 to the left or resonator 420 to the right in cross-sectional side view 600A) will result in lower coupling and, during operation of the device, weaken the signal in signal path 664. Such a configuration as described herein can be used to change the combined interaction between the fields of the coupled resonators (e.g., the value of Equation 2), adjust the filter response characteristics, and set the performance characteristics of the filter using not only the resonant characteristics of the individual resonators but also the coupling between the resonators.

[0085] The coupling between resonators on opposite sides of the piezoelectric substrate is not based solely on a simple property of thickness, but will also vary with the pitch of the electrode fingers in the IDT of the resonator. As mentioned above, the frequency present in a SAW resonator is based on the pitch of the electrode fingers, and similarly, the coupling between resonators on opposite sides of the piezoelectric substrate will depend on the pitch of these fingers. In operation, the wavelength for the resonator can be considered to be twice the spacing between the electrode fingers (e.g., 2*pitch, where pitch is the spacing between the fingers). In a piezoelectric substrate with a single layer (e.g., as Figure 5AIn some aspects (shown in FIG), when the thickness of the piezoelectric substrate (e.g., thickness 533 or 633) is between 0.2 and 1 times the resonant wavelength (e.g., between 0.4 and 2 times the distance between the electrode fingers of the IDT), the coupling between the resonators can provide beneficial performance characteristics with efficient coupling. In other aspects that can operate with vertical coupling that may involve additional distortion of the signal, the thickness of the piezoelectric substrate is between 0.05 and 10 times the value of the wavelength (e.g., between 0.1 and 20 times the distance between the electrode fingers of the IDT).

[0086] and Figure 6A 、 Figure 6B compared to, Figure 5A 、 Figure 5B Different designed offsets between the IDTs on the top and bottom piezoelectric surfaces of a single piezoelectric layer are described. For example, Figure 6A and Figure 6B , a device is described in which the projection of resonator 410 from the first piezoelectric surface onto the second piezoelectric surface in the vertical direction does not overlap with resonator 420. Such an offset can limit or reduce the electroacoustic resonance across the piezoelectric layer between the IDT on the top surface and the IDT on the bottom surface.

[0087] In contrast, Figure 5A and Figure 5B A structure is described in which the resonator 410 and the resonator 420 overlap in a vertical direction such that an area on a first piezoelectric surface including the first resonator 410 (e.g., a top IDT) overlaps an area on a second piezoelectric surface including the resonator 420 (e.g., a second IDT) across a vertical projection of the piezoelectric substrate.

[0088] In addition to these structures, intermediate overlapping structures can be used to tune the electroacoustic coupling across the piezoelectric layer. For example, instead of using Figure 5A and Figure 5B completely overlapped as in Figure 6A and Figure 6B . A structure can be created in which resonator 410 and resonator 420 partially overlap in the vertical direction, such that at least a threshold portion of the vertical projection of resonator 410 (e.g., the first IDT) across the piezoelectric substrate overlaps an area on the second piezoelectric surface that does not include resonator 420 (e.g., the second IDT). Any level of overlap can be used in different aspects, such as having a threshold amount of overlap of the IDTs in the vertical direction (e.g., 25%, 50%, 75%, or any other threshold overlap, or overlap targeted to achieve a given electroacoustic coupling characteristic for filter performance characteristics).

[0089] Figure 7 is a cross-sectional side view 700 of a piezoelectric substrate 730 having two piezoelectric layers 741 and 742 and a spacer layer 740 with vertically coupled resonators 710 and 720 according to various aspects described herein. Figure 5A 、 Figure 5B 、 Figure 6A and Figure 6B While the device includes a simple piezoelectric substrate having a single layer of piezoelectric material, some aspects may include a more complex piezoelectric substrate. As shown, piezoelectric substrate 730 includes a first piezoelectric layer 741 and a second piezoelectric layer 742, where the first piezoelectric layer 741 comprises the top surface 731 of the piezoelectric substrate and the second piezoelectric layer 742 comprises the bottom surface 732 of the piezoelectric substrate. The first piezoelectric layer 741 and the second piezoelectric layer 742 are separated by a spacer layer 740. In some implementations, the spacer layer 740 can be a dielectric material. In some implementations, the spacer layer 740 can facilitate manufacturing by allowing the resonators 710 and 720 to be independently fabricated on the separate piezoelectric layers 741 and 742, where the layers can then be bonded together using the spacer layer 740. In some aspects, Ta2O5, HfO2, Al2O3, WO3, Nb2O5, SiOx, polymers, PSN, and other oxides and nitrides (e.g., AlN) can be used. In some implementations, piezoelectric layers 741 and 742 are made of the same piezoelectric material. In other implementations, piezoelectric layers 741 and 742 are made of different piezoelectric materials. Using piezoelectric layers 741 and 742 made of different piezoelectric materials provides further flexibility when designing the characteristics of the two (coupled) resonators 710 and 720. In various aspects, a variety of crystal orientations (e.g., LN128, etc.) can be used in which the main mode is more concentrated at the top of the piezoelectric layer. In some aspects, a cut or piezoelectric material orientation can be used that will provide stronger radiation toward the body already used for the main mode (such as LT42 with lithium tantalate). In some aspects, a mixture of LT (e.g., LT42 and LT36) and different cuts of LT and LN, LT and doped LT, etc. can be used. In some aspects, doping can be used to improve coupling, temperature behavior, etc., while maintaining the polarization of the acoustic mode. In some aspects, different LT layers can be mixed with different doping or without doping.

[0090] Furthermore, the spacer layer 740 can modify the coupling beyond that determined by the thickness of the piezoelectric substrate 730. As discussed above, the thickness of the piezoelectric substrate 730, as associated with the vertical distance between the resonators 710 and 720, affects the coupling between the resonators 710 and 720. The presence of a spacer layer 740 of a material different from the piezoelectric material in the piezoelectric layers 741 and 742 can further affect the coupling. Specifically, in some implementations, when different coupling characteristics are desired, the thickness of the spacer layer 740 can be increased while the thickness of the piezoelectric layers 741 and 742 can be decreased to modify the coupling between the resonators on different portions of the device while maintaining a uniform piezoelectric substrate thickness. This coupling adjustment from the thickness of the spacer layer 740 is in addition to the adjustments that can be made to the coupling based on the positioning offset as discussed above.

[0091] Furthermore, in some implementations, depending on the material and geometry of the spacer layer, the spacer layer 740 can act as a waveguide to further generate complex coupling of wave modes between the resonators. Some such structures can result in plate modes that allow the resonators to exchange energy, thereby creating a passband with increased bandwidth for a given spatial usage. In some aspects, various aspects of such a configuration can be used to control the wave modes and details of the coupling interaction between the resonators to provide an improved filter response curve. In some aspects, the thickness of the spacer layer 740 is between 0.05 and 5 times the resonant wavelength of the resonators 710 and 720 (e.g., assuming equal pitch and piezoelectric material). In some aspects, the thickness of the spacer layer 740 is between 0.1 and 0.6 times the resonant wavelength to allow the formation of plate modes. In some aspects, the total thickness of the piezoelectric substrate (e.g., including at least one piezoelectric layer and optional dielectric or spacer layer) can be between 0.05 and 10 times. In some aspects, the total thickness of the piezoelectric substrate can be between 0.2 and 1 times the resonant wavelength, as described above with respect to Figure 6A and Figure 6B The thickness of the spacer layer may be selected to be greater than 5 times the resonant wavelength to decouple the first resonator 710 and the second resonator 720 .

[0092] Figure 8 is a cross-sectional side view 800 of a piezoelectric substrate having two piezoelectric layers and a spacer layer with additional resonators in the spacer layer and having vertically coupled resonators according to various aspects described herein. The cross-sectional side view 800 shows a piezoelectric substrate similar to that in FIG. Figure 7 A device similar to the device shown in , but with the additional resonator located in the spacer layer 840. As in Figure 7 middle, Figure 8A piezoelectric substrate 830 is shown, which includes a first piezoelectric layer 841, a second piezoelectric layer 842, and a spacer layer 840 between the two piezoelectric layers 841, 842. Figure 8 In the embodiment, a first resonator 810 is provided on a first surface 831 (eg, top surface) of a first piezoelectric layer 841, and a second resonator 820 is provided on a second surface 832 (eg, bottom surface) of a second piezoelectric layer 842. Figure 8 , the spacer layer 840 has a boundary (or contact surface) 833 with the first piezoelectric layer 841 and a boundary (or contact surface) 834 with the second piezoelectric layer 842. The third resonator 850 is formed on or above the boundary of the first piezoelectric layer 841 (e.g., on the bottom surface), and the fourth resonator 860 is formed on or above the boundary of the second piezoelectric layer 842 (e.g., on the top surface) and inside the spacer layer 840. In one aspect, the first IDT of the first resonator 810 is disposed above the top surface of the first piezoelectric layer 841, and the third IDT of the third resonator 850 is disposed above the bottom surface of the first piezoelectric layer 841, while the second IDT of the second resonator 820 is disposed above the bottom surface of the second piezoelectric layer 842, and the fourth IDT of the fourth resonator 860 is disposed above the top surface of the second piezoelectric layer 842. In one aspect, the third IDT of the third resonator 850 and the fourth IDT of the fourth resonator 860 are embedded in the spacer layer 840 (eg, they are embedded in a dielectric layer).

[0093] The placement of the third resonator 850 and the fourth resonator 860 allows for further density and reduced size of AW resonator packaging and may allow for further sophistication in the coupling of the resonators.

[0094] Despite Figure 7 and Figure 8 Two piezoelectric layers are shown in the exemplary implementation of , but the present disclosure is not limited thereto. For example, further piezoelectric layers may be added by stacking further spacer layers below the second resonator 820 and repeating the layer stack consisting of the fourth resonator 860, the second piezoelectric layer 842, and the second resonator 820, thereby expanding the Figure 8 By repetition, three, four or more piezoelectric layers can be provided in the piezoelectric substrate 830. Similarly, Figure 7The two layer stacks shown in can be combined with a further spacer layer in between as a piezoelectric substrate. In all implementations presented herein, the spacer layer 740, 840 can comprise more than one layer, for example two or more layers, wherein at least two layers are made of different dielectric materials. Different dielectric materials can be provided to decouple the first resonator and the second resonator. Alternatively or in addition, the spacer layer can comprise one or more temperature compensation layers, for example in Figure 8 A temperature compensation layer is provided above each of the third resonator 850 and the fourth resonator 860 in the first piezoelectric layer 841. A dielectric layer can be provided between the two temperature compensation layers. In some implementations, the spacer layer 840 can be replaced by one or more cavities (e.g., filled with air or an inert gas), wherein the corresponding resonators are provided within the one or more cavities. For example, the one or more cavities can be formed using a frame and / or spacer, which is provided as part of the spacer layer 840 between the bottom surface 833 of the first piezoelectric layer 841 and the top surface 834 of the second piezoelectric layer 842.

[0095] Figure 9 is a cross-sectional side view of an AW package 900 including a piezoelectric substrate 910 having vertically coupled resonators according to various aspects described herein. The AW package 900 illustrates how a package can be used to form a packaged device having vertically coupled resonators as described above. In the AW package 900, the piezoelectric substrate 910 has a top surface 911 and a bottom surface 912, with three resonators shown on each of the top surface 911 and the bottom surface 912. However, the present disclosure is not limited to the implementation shown, but may include fewer or more resonators, for example, including at least one resonator on each surface. The resonators on the top surface are formed using the electrode fingers of the IDTs 931, 932, and 933 shown. The resonators on the bottom surface are formed using the electrode fingers of the IDTs 941, 942, and 943 shown.

[0096] Electrical connections between the resonators are shown as vias 951, 952, and 953. Connections (not shown) may also be provided between the IDTs (e.g., on top surface 911). Contacts 958 and 959 may provide input and output connections for signals processed by the filter formed by the resonators including IDTs 931, 932, 933, 941, 942, and 943. IDTs 932, 932, and 933 formed on surface 911 are protected by cap 990. IDTs 941, 942, and 943 formed on surface 912 of piezoelectric substrate 910 are located within a cavity 902 formed in the top surface of substrate 901 (e.g., silicon), which supports piezoelectric substrate 910, for example, by being bonded to it. The piezoelectric substrate 910 is supported along a surface 912 at a boundary 903 where the substrate 901 contacts the surface 912 where no cavity 902 is present in the substrate 901. The cavity 902 and the cap 990 create a protective space around the IDT that allows the IDT to operate without interference from the material that would prevent the electroacoustic resonance described above as part of the operation of the SAW.

[0097] In one implementation, the AW package 900 may be a filter device having a three-stage filter, where each top and bottom pair of resonators forms a stage of the filter, as described above in Figure 4A and Figure 4B As mentioned above, fewer or more stages may be provided, for example, at least one stage. The resonant characteristics of the vertically coupled pairs of resonators and IDTs (including: a first pair including IDT 931 and IDT 941, a second pair including IDT 932 and IDT 942, and a third pair including IDT 933 and IDT 943) (which include not only the pitch and electrode finger details for each IDT, but also the vertical coupling) may be designed to produce a compact filter according to various aspects described herein.

[0098] In some aspects, the AW package 900 can be formed using a series of process steps as described below. The AW package 900 can start with a bulk wafer of piezoelectric material for a piezoelectric substrate 910. One or more vias are created through the piezoelectric substrate 910 from surface 911 to surface 912, and conductive vias 951, 952, 953 are formed from the first surface 911 to the second surface 912 using the one or more vias. A first acoustic layer (e.g., a resonator layer) including IDTs 931, 932, and 933 is fabricated on the first surface 911 of the piezoelectric substrate 910, as well as connections to and between the IDTs 931, 932, and 933, depending on the filter configuration of the AW package. The bulk wafer is then flipped, and a second acoustic layer including IDTs 941, 942, and 943 and any connections to the vias 951, 952, 953 are fabricated, depending on the filter configuration.

[0099] Silicon substrate 901 is etched to form cavity 902, and piezoelectric substrate 910 is bonded to silicon substrate 901 at boundary 903 such that IDTs 941, 942, and 943 are aligned with cavity 902 (e.g., such that they are provided within cavity 902). Contacts 958 and 959 and cap 990 can then be formed on top surface 911. In various implementations, the individual packages can be separated from the bulk wafer at any point in the process, depending on the particular manufacturing implementation.

[0100] exist Figure 9 In the embodiment of the present invention, the cap 990 can be a sealant material or a rigid cap configured to protect the top IDTs 931, 932, and 933. In some aspects, the cap is made of a polymer or a material deposited by plasma enhanced chemical vapor deposition (PECVD), such as silicon nitride. Other implementations can use other protective structures as described below.

[0101] Figure 10 is a cross-sectional side view of an AW package 1000 including a piezoelectric substrate 1010 with vertically coupled resonators according to various aspects described herein. The AW package 1000 is similar to Figure 9AW package 900 is shown, wherein the AW package includes a substrate 1001 (e.g., silicon or other suitable material) having a cavity 1002 and a boundary 1003, wherein a piezoelectric substrate 1010 is supported by substrate 1001. The piezoelectric substrate has IDTs 1031, 1032, and 1033 on surface 1011, and IDTs 1041, 1042, and 1043 on surface 1012 of the piezoelectric substrate (e.g., on the surface of the piezoelectric substrate 1010 opposite surface 1012). Compared to AW package 900, cap 1090 of AW package 1000 is a glass cap 1090 having vias 1051, some of which are formed through glass cap 1090, and some of which are formed through both glass cap 1090 and piezoelectric substrate 1010. In some cases, cap 1090 can be formed of another material, such as the same material as piezoelectric substrate 1010. Contacts 1059 are provided on top of the cap 1090 (e.g., on top of the vias 1051). Spacers 1092 separate the cap 1090 from the surface 1011 of the piezoelectric substrate 1010. This structure with a glass cap 1090 can facilitate more complex IDT arrangements on the surface 1011, and using the spacers 1092 as a mechanical support structure to create space between the cap 1090 and the surface 1011 for the operation of the IDTs 1031, 1032, 1033 can improve the mechanical stability of the AW package 1000.

[0102] Figure 11 is a cross-sectional side view of an AW package 1100 including two piezoelectric layers in a stacked package similar to AW package 300 , showing details of vertically coupled resonators according to various aspects described herein.

[0103] As shown, the AW package 1100 includes two piezoelectric layers 1111 and 1110. The piezoelectric layer 1111 does not have a vertically coupled IDT, but includes an IDT 1151 on one side of the piezoelectric layer 1111, wherein the substrate 1102 (e.g., a silicon substrate) provides support for the piezoelectric layer 1111. The second piezoelectric layer 1110 includes vertically coupled resonators formed by 1131 and 1141 on the top and bottom surfaces of the piezoelectric layer 1110 as described above, wherein the supporting substrate 1101 (e.g., a silicon substrate) serves as the base substrate for the multi-level package. The cap 1190 provides a cap for the top IDT 1151. The spacer 1192 provides structural support for the various layers and the cap, and forms an electrical connection via the via 1191 and the contact 1159. The cap 1190 and the spacer 1192 can be formed of various materials.

[0104] Figure 12FIG2 is a cross-sectional side view of an AW package 1200 including two piezoelectric substrates with vertically coupled resonators according to various aspects described herein. AW package 1200 includes a first piezoelectric substrate 1211 and a second piezoelectric substrate 1210. Piezoelectric substrate 1211 has vertically coupled IDTs 1251 and 1252 on opposite sides. Piezoelectric substrate 1211 is separated from cap 1290 using spacers 1292, with vias 1291 providing electrical coupling from each IDT 1231, 1241, 1251, 1252 to contacts 1259 on top of cap 1290. The second piezoelectric substrate is mounted on a support substrate 1201 (e.g., a silicon substrate) with a cavity in substrate 1201 to provide an area for the lower piezoelectric surface of piezoelectric substrate 1210 and the lower piezoelectric surface of IDT 1241 between substrate 1201. Spacer 1292 separates spacer layer 1295 from the top piezoelectric surface of the piezoelectric substrate having IDT 1231. Spacer layer 1295 acts as a substrate for piezoelectric substrate 1211 (e.g., similar to substrate 1201), with lower IDT 1252 located in a cavity of spacer layer 1295, such that spacer layer 1295 acts as a protective layer for lower IDT 1252 of the first piezoelectric substrate.

[0105] Regions 1270 and 1280 illustrate different regions where electroacoustic coupling across the piezoelectric layers of piezoelectric substrates 1211 and 1210 can occur. As shown and described herein, the IDTs on the top and bottom surfaces can be positioned with different amounts of vertical overlap to adjust or select filter characteristics associated with vertical electroacoustic coupling across the corresponding piezoelectric layers. For example, region 1270 illustrates a partial overlap between IDT 1251 on the top piezoelectric surface of the piezoelectric substrate and IDT 1252 on the lower piezoelectric surface of the piezoelectric substrate 1211 within region 1270. In region 1280, the upper IDT 1231 in region 1280 does not overlap with the IDT 1241 in region 1280.

[0106] Figure 13 is a cross-sectional side view 1300 of aspects of a piezoelectric substrate that may be used in an AW package according to aspects described herein. Figure 13The device includes a piezoelectric substrate 1310 having a top IDT 1331 on the top piezoelectric surface and a bottom IDT 1341 on the bottom piezoelectric surface. A protective layer 1309 protects the bottom IDT 1341 and is used to mount (e.g., via bonding) the piezoelectric substrate 1310 to a supporting substrate 1301 (e.g., a silicon substrate). Vias 1351 connect the bottom IDT 1341 to the top IDT 1331, and contacts 1359 allow the IDT to be electrically coupled to other parts of the device (e.g., other parts of the RF filter). Vertical signal paths 1364 within the piezoelectric substrate 1310 allow vertical coupling between the top IDT 1331 and the bottom IDT 1341.

[0107] Figure 14 is a cross-sectional side view 1400 of aspects of a piezoelectric substrate that may be used in an AW package according to aspects described herein. Figure 14 A piezoelectric substrate 1430 is shown having an upper piezoelectric layer 1432, a lower piezoelectric layer 1433, and a dielectric spacer layer 1434. A top IDT 1431 is disposed above the upper piezoelectric surface, and a lower IDT 1441 is disposed above the lower piezoelectric surface. As used herein, the IDT layer "being disposed "above" the piezoelectric surface uses "above" relative to the center portion of the substrate, such that the IDT layer disposed above the upper layer can be located in the opposite direction to the IDT layer disposed above the lower layer, as the above position is relative to the center portion of the piezoelectric substrate having an upper surface and a lower surface. Vias 1451 provide electrical connections between the IDTs 1431 and 1441, with contacts 1459 used for electrical connections to other elements (e.g., other components of an RF filter). A protective layer 1409 is used to protect the lower IDT 1441 and to mount the piezoelectric substrate 1430 to a supporting substrate 1401 (e.g., a silicon substrate).

[0108] In various implementations, the cross-sectional side view 1300 or the cross-sectional side view 1400 may be used as Figure 12 As described herein, the vertical alignment can be varied between different implementations to achieve different electroacoustic couplings across the piezoelectric substrate or piezoelectric layer for IDTs on different piezoelectric surfaces, where the electroacoustic coupling across the layer determines the filter characteristics of the device. Figure 5A 、 Figure 5B 、 Figure 6A and Figure 6B As described in , some implementations may use a piezoelectric substrate with a single piezoelectric layer. Figure 7As described in , other piezoelectric substrates may include multiple piezoelectric layers separated by spacer layers. Multi-level AW packages such as AW package 1200 may use a single layer piezoelectric substrate or a multi-layer piezoelectric substrate, such as by Figure 13 and Figure 14 shown.

[0109] exist Figure 13 , the vertically coupled resonator including IDTs 1331 and 1341 generates not only surface waves when excited, but also a vertical signal path 1364 based on the vertical coupling between IDTs 1331 and 1341. The combination of the surface wave and the vertical signal path 1364 can generate a composite filter response based on the electrical signal input at the input contact of the filter, the electrical signal output at the output contact of the filter, and the electrical signal transmitted between the contacts and the resonator through the vias of the filter (e.g., contact 1359 and via 1351). Similarly, in Figure 14 In cross-sectional view 1400 of FIG, in addition to the surface wave path, IDT 1431 and IDT 1441 can also generate a vertical signal path 1464. As described above, the design of the coupling that generates the vertical signal path 1364 or 1464 can be based on the pitch of the electrode fingers of the vertically coupled IDTs 1331 and 1341 or 1431 and 1441, the thickness of the piezoelectric substrate separating the vertically coupled IDT pairs (including the spacer layer 1434 (if provided)), the material forming the corresponding piezoelectric substrate, and any offset between the electrode fingers of the vertically coupled IDT pairs (e.g., non-overlapping areas in the vertical direction). Such a configuration can be used as described herein to provide additional parameter space for shaping the filter function when designing devices using AW filters according to various aspects described herein. In some aspects, different polarization modes of the vertically coupled IDT pairs can be designed to form passbands, which can allow the mode characteristics to be customized to combine the advantages of both modes. In some aspects, taking coupling into account can allow for reduced filter size while designing a "nearly decoupled" or vertical multi-level package that is sized for coupling to occur but sized to benefit from or provide minimal impact on filter performance.

[0110] Figure 15 is a flow chart illustrating a method 1500 (or process) for manufacturing one aspect of a device including vertically coupled resonators. The method 1500 is described in terms of a set of blocks specifying operations that may be performed. However, the operations are not necessarily limited to Figure 151702, which configures the resonator circuit. In some implementations, the method 1500 may be implemented as instructions stored in a non-transitory computer-readable storage medium that, when executed by one or more processors of a device (e.g., a manufacturing system), causes the device to perform the operations of the method 1500.

[0111] At block 1502 , method 1500 includes creating one or more vias through a piezoelectric substrate, wherein the piezoelectric substrate has a first piezoelectric surface and a second piezoelectric surface opposite the first surface.

[0112] At block 1504 , method 1500 includes fabricating one or more conductive vias from the first piezoelectric surface to the second piezoelectric surface using the one or more vias.

[0113] At block 1506 , method 1500 includes fabricating a first acoustic layer over a first piezoelectric surface of a piezoelectric substrate, wherein the first acoustic layer includes one or more first interdigital transducers (IDTs) and one or more connections from the one or more first IDTs to one or more conductive vias.

[0114] At block 1508 , the method 1500 includes depositing one or more spacers on the first piezoelectric surface of the piezoelectric substrate using the resist layer to protect the one or more first IDTs.

[0115] At block 1510 , the method 1500 includes: bonding one or more spacers to a silicon substrate to mount a piezoelectric substrate on the silicon substrate using the one or more spacers;

[0116] At block 1512 , method 1500 includes thinning the piezoelectric substrate to a selected thickness by removing material from a second piezoelectric surface of the piezoelectric substrate.

[0117] At box 1514, method 1500 includes: manufacturing a second acoustic layer over the second piezoelectric surface of the piezoelectric substrate, wherein the second acoustic layer includes one or more second IDTs connected to the one or more first IDTs via one or more conductive vias, and wherein the one or more first IDTs and the one or more second IDTs are provided as part of a radio frequency filter circuit.

[0118] The operations of the above blocks may be combined with repeated operations or intermediate operations to fabricate any configuration of devices having multiple layers, multiple devices, or vertically integrated IDTs according to aspects described herein.

[0119] In some aspects, IDTs (such as one or more first IDTs and one or more second IDTs) can be fabricated in positions relative to each other in different piezoelectric surfaces and layers to produce IDTs with filter characteristics based on relative position across the piezoelectric layer, wherein electroacoustic coupling between the IDTs is based on relative position and serves as the filter characteristic of the device. For example, in some aspects, the IDTs can be positioned directly relative to each other across the piezoelectric layer, wherein the electroacoustic coupling across the piezoelectric layer is based on the piezoelectric layer thickness and the resonance of the fingers of the IDTs. In other aspects, the IDTs can be offset from each other to modify the electroacoustic coupling across the piezoelectric layer. For example, in some aspects, the filter characteristics of the AW filter package filter are based on electroacoustic coupling between the one or more first IDTs and the one or more second IDTs through the piezoelectric substrate, wherein the electroacoustic coupling through the piezoelectric substrate is based in part on the overlap between the one or more first IDTs and the one or more second IDTs in a vertical direction across the piezoelectric substrate. In other aspects, a projection of the one or more first IDTs from the first piezoelectric surface onto the second piezoelectric surface in a vertical direction does not overlap with the one or more second IDTs to reduce electroacoustic coupling across the piezoelectric layer.

[0120] Figure 16A is another flow chart illustrating a method 1600 (or process) for manufacturing one aspect of an apparatus including vertically coupled resonators. The method 1600 is described in terms of a set of blocks specifying operations that may be performed. However, the operations are not necessarily limited to Figure 16A 1600 or the order shown in or described herein, as these operations can be implemented in an alternative order or in a completely or partially overlapping manner. In addition, more, fewer, and / or different operations can be implemented to perform method 1600 or an alternative method. In some implementations, method 1600 can be implemented by control or processing circuitry of a system for manufacturing a wireless device (e.g., electronic device 1702) that configures the manufacture of the resonator circuit. In some implementations, method 1600 can be implemented as instructions stored in a non-transitory computer-readable storage medium that, when executed by one or more processors of a device (e.g., a manufacturing system), causes the device to perform the operations of method 1600.

[0121] At block 1602, method 1600 includes generating a first piezoelectric layer. The first piezoelectric layer may be a piezoelectric layer according to any of the descriptions provided herein. The first piezoelectric layer may be, for example, a bulk wafer of any of the piezoelectric materials described herein.

[0122] At block 1604, method 1600 includes fabricating a lower acoustic layer (e.g., an IDT) above a lower piezoelectric surface of the first piezoelectric layer. The lower acoustic layer can be fabricated, for example, using a photolithographic process. As described above, such fabrication can include placing the acoustic layer directly on the piezoelectric surface, or can involve an intermediate layer, wherein the lower acoustic layer is disposed above the lower piezoelectric surface (e.g., where the above position is relative to the center of the first piezoelectric layer).

[0123] At block 1606, method 1600 includes fabricating a protective layer for the lower acoustic layer. The protective layer may be, for example, a silicon oxide (eg, SiO2) layer fabricated using a sputtering deposition process in areas selected to protect the acoustically active region.

[0124] At block 1608, method 1600 includes attaching the first piezoelectric layer to a substrate. The substrate may be, for example, a silicon substrate bonded to the piezoelectric layer or bonded to the protective layer.

[0125] At block 1610, method 1600 includes thinning the first piezoelectric layer. The thinning operation can be performed to produce a selected thickness for the piezoelectric layer based on desired electroacoustic properties, including electroacoustic coupling between the upper and lower acoustic layers and between the IDTs in the upper and lower acoustic layers. In some aspects, the piezoelectric layer can be thinned to approximately 400 nanometers (nm). In other aspects, other thicknesses can be used (e.g., between 50 nm and 1000 nm, or a given multiple of the IDT finger period as described herein).

[0126] At block 1612, method 1600 includes fabricating an upper (e.g., second) acoustic layer over the upper piezoelectric surface (e.g., using a photolithography process, which may be the same process as block 1604). As above, such fabrication may include disposing the upper acoustic layer over the piezoelectric surface, or may include fabricating an intermediate layer, wherein the upper piezoelectric surface is disposed over the piezoelectric layer, wherein the intermediate layer is between the upper acoustic layer and the upper piezoelectric surface (e.g., wherein the upper position is relative to the center of the piezoelectric layer).

[0127] Figure 16B is another flow chart illustrating a method 1650 (or process) for manufacturing one aspect of a device including vertically coupled resonators. As with methods 1500 and 1600 above, method 1650 is described in terms of a set of blocks specifying operations that may be performed. However, the operations are not necessarily limited to Figure 16B1650. In some implementations, the method 1650 may be implemented by control or processing circuitry of a system for manufacturing a wireless device (e.g., electronic device 1702) that configures the manufacture of the resonator circuit. In some implementations, the method 1650 may be implemented as instructions stored in a non-transitory computer-readable storage medium that, when executed by one or more processors of a device (e.g., a manufacturing system), causes the device to perform the operations of the method 1650.

[0128] Method 1650 includes blocks 1602 through 1608 described above. However, after block 1608, method 1650 then proceeds to block 1652, which involves creating a second piezoelectric layer. The second piezoelectric layer can be a second bulk wafer similar to the bulk wafer of the first piezoelectric material or any other such piezoelectric layer.

[0129] At block 1654, method 1650 includes adding a dielectric layer to the lower piezoelectric surface of the second piezoelectric layer. The dielectric layer can be the same material manufactured by the same process as the protective layer, but uniform, rather than being positioned around the acoustically active area as described above. The dielectric layer can be a silicon oxide (e.g., SiO2) layer sputter-deposited to a thickness of 400 nm in combination with the first and second layers thinned to 100 nm. In other aspects, other combinations of piezoelectric layer thicknesses and dielectric layer thicknesses can be used.

[0130] At block 1656, method 1650 includes bonding the second piezoelectric layer to the first piezoelectric layer with the dielectric layer between the first and second piezoelectric layers. This bonding creates a piezoelectric substrate in which the top and bottom piezoelectric layers are separated by the dielectric layer, wherein a protective layer separates the lower piezoelectric layer from the silicon substrate, wherein the protective layer creates a protective gap for a lower acoustic (e.g., IDT) layer.

[0131] At block 1658 , method 1650 includes thinning the second piezoelectric layer (eg, to match the first or upper piezoelectric layer and produce target filter characteristics).

[0132] Method 1650 then includes the operation of block 1612: fabricating an upper acoustic layer over the upper piezoelectric surface. Compared to block 1612 of method 1650, the upper piezoelectric surface is the surface of the second piezoelectric layer in method 1650, rather than the surface of the first piezoelectric layer in method 1650. Thus, while method 1600 results in a Figure 5A 、 Figure 5B 、 Figure 6A or Figure 6B (e.g., depending on the offset of the fabricated IDT), but method 1650 results in a device similar to Figure 7 The vertically coupled resonators 710 and 720 are in an acoustic layer fabricated on the piezoelectric surfaces of the piezoelectric layers 741 and 742.

[0133] Additionally, it will be apparent that, using the described blocks, similar combinations of operations are possible to produce any structure described herein (including Figure 8 structure with four acoustic layers) and additional manufacturing operations for adding vias and electrical connections between the acoustic layers.

[0134] Figure 17 is a schematic diagram of an environment 1700 including an electronic device 1702 including a wireless transceiver 1796 (such as in Figure 18 ). Further, as shown, wireless transceiver 1796 may include filter 1797. Filter 1797 may be implemented as a vertically coupled filter as described herein. Additionally, while electronic device 1702 is shown with wireless transceiver 1796 including filter 1797, base station 1704 may include similar wireless transceiver circuitry implemented using stacked AW filters as described herein.

[0135] In some aspects, the electronic device 1702 includes a display screen 1799 that can be used to display information associated with data sent via a wireless link 1706 and processed using the components of the electronic device 1702 described below. Other aspects of the electronic device using a low phase delay filter for multi-band communication according to the various aspects described herein can be configured without a display screen. In environment 1700, the electronic device 1702 communicates with the base station 1704 via a wireless link 1706. As shown, the electronic device 1702 is depicted as a smart phone. However, the electronic device 1702 can be implemented as any suitable computing or other electronic device, such as a cellular base station, a broadband router, an access point, a cellular or mobile phone, a gaming device, a navigation device, a media device, a laptop computer, a desktop computer, a tablet computer, a server computer, a network attached storage (NAS) device, a smart appliance, a smart watch, smart glasses, augmented reality (AR) glasses, a car including a vehicle-based communication system, a vehicle head unit, an Internet of Things (IoT) device, a sensor or security device, an asset tracker, etc.

[0136] Base station 1704 communicates with electronic device 1702 via wireless link 1706, which can be implemented as any suitable type of wireless link. Although base station 1704 is depicted as a base station tower of a cellular radio network, base station 1704 can represent or be implemented as another device, such as a satellite, a terrestrial broadcast tower, an access point, a peer device, a mesh network node, a fiber optic line, another electronic device generally as described above, etc. Thus, electronic device 1702 can communicate with base station 1704 or another device via a wired connection, a wireless connection, or a combination thereof. Wireless link 1706 can include a downlink for data or control information transmitted from base station 1704 to electronic device 1702, and an uplink for other data or control information transmitted from electronic device 1702 to base station 1704. Wireless link 1706 can be a wireless communication protocol using any suitable communication protocol or standard, such as Third Generation Partnership Project Long Term Evolution (3GPP LTE, 3GPP NR5G), IEEE 802.11, IEEE 802.16, Bluetooth 5.0, or similar. TM etc.) to achieve this.

[0137] The electronic device 1702 includes a processor 1780 and a memory 1782. The memory 1782 may be or form part of a computer-readable storage medium. The processor 1780 may include any type of processor, such as an application processor or a multi-core processor, which is configured to execute processor-executable instructions (e.g., code) stored by the memory 1782. The memory 1782 may include any suitable type of data storage medium, such as volatile memory (e.g., random access memory (RAM)), non-volatile memory (e.g., flash memory), optical media, magnetic media (e.g., disk or tape), etc. In the context of the present disclosure, the memory 1782 is implemented to store instructions 1784, data 1786, and other information for the electronic device 1702, and therefore, when configured as or as part of a computer-readable storage medium, the memory 1782 does not include a transient propagating signal or carrier wave.

[0138] The electronic device 1702 may also include input / output (I / O) ports 1790. The I / O ports 1790 enable data exchange or interaction with other devices, networks, or users, or between components of the device.

[0139] The electronic device 1702 may also include a signal processor (SP) 1792 (eg, such as a digital signal processor (DSP)). The signal processor 1792 may function similarly to a processor and, in conjunction with the memory 1782, may execute instructions and / or process information.

[0140] For communication purposes, the electronic device 1702 also includes a modem 1794, a wireless transceiver 1796, and an antenna (not shown). The wireless transceiver 1796 uses radio frequency (RF) wireless signals to provide connectivity to a corresponding network and other electronic devices connected thereto, and may include Figure 18 The wireless transceiver 1796 may facilitate communication over any suitable type of wireless network, such as a wireless local area network (LAN) (WLAN), a peer-to-peer (P2P) network, a mesh network, a cellular network, a wireless wide area network (WWAN), a navigation network (e.g., the Global Positioning System (GPS) or another Global Navigation Satellite System (GNSS) for North America), and / or a wireless personal area network (WPAN).

[0141] Figure 18 A wireless communication device 1800 is shown that includes RF components formed from one or more ICs 1802 and that may include vertically coupled resonators as part of a filter (e.g., filter 1797) of a wireless transceiver 1796. As an example, the wireless communication device 1800 may include or be provided in any of the devices described above. Figure 18 As shown, wireless communication device 1800 includes a transceiver 1804 and a data processor 1806 (e.g., processing circuitry). Data processor 1806 may include memory for storing data and program codes. Transceiver 1804 includes a transmitter 1808 and a receiver 1810 that support bidirectional communication. In general, wireless communication device 1800 may include any number of transmitters 1808 and / or receivers 1810 for any number of communication systems and frequency bands. All or a portion of transceiver 1804 may be implemented on one or more analog ICs, RFICs, mixed-signal ICs, etc.

[0142] The transmitter 1808 or the receiver 1810 may be implemented using a super-heterodyne architecture or a direct conversion architecture. In a super-heterodyne architecture, the signal is frequency converted between RF and baseband in multiple stages, for example, from RF to an intermediate frequency (IF) in one stage, and then from IF to baseband in another stage. In a direct conversion architecture, the signal is frequency converted between RF and baseband in one stage. Super-heterodyne and direct conversion architectures may use different circuit blocks and / or have different requirements. Figure 18 In the wireless communication device 1800 in FIG. 1 , the transmitter 1808 and the receiver 1810 are implemented using a direct conversion architecture.

[0143] In the transmit path, the data processor 1806 processes the data to be transmitted and provides I and Q analog output signals to the transmitter 1808. In the wireless communication device 1800, the data processor 1806 includes digital-to-analog converters (DACs) 1812(1), 1812(2) for converting the digital signals generated by the data processor 1806 into I and Q analog output signals (e.g., I and Q output currents) for further processing.

[0144] Within transmitter 1808, low-pass filters 1814(1), 1814(2) filter the I and Q analog output signals, respectively, to remove undesired signals caused by the previous digital-to-analog conversion. Amplifiers (AMPs) 1816(1), 1816(2) amplify the signals from low-pass filters 1814(1), 1814(2), respectively, and provide I and Q baseband signals. An upconverter 1818 upconverts the I and Q baseband signals with I and Q TX local oscillator (LO) signals from a transmit (TX) local oscillator (LO) signal generator 1822 via mixers 1820(1), 1820(2) to provide an upconverted signal 1824. A filter 1826 filters the upconverted signal 1824 to remove undesired signals caused by the upconversion and noise in the receive band. A power amplifier (PA) 1828 amplifies the upconverted signal 1824 from the filter 1826 to obtain a desired output power level and provides a transmit RF signal. The transmit RF signal is routed through a multiplexer or switch 1830 and transmitted via an antenna 1832 (e.g., where the multiplexer may be a duplexer or any other such multiplexing circuitry).

[0145] In the receive path, antenna 1832 receives the signal transmitted by the base station and provides a received RF signal, which is routed through a multiplexer or switch 1830 and provided to a low noise amplifier (LNA) 1834. Multiplexer or switch 1830 is designed to operate with a specific receive (RX) to TX multiplexer frequency separation so that the RX signal is isolated from the TX signal. The received RF signal is amplified by LNA 1834 and filtered by filter 1836 to obtain the desired RF input signal. Down-conversion mixers 1838 (1), 1838 (2) mix the output of filter 1836 with the I and Q RX LO signals (e.g., LO_I and LO_Q) from RX LO signal generator 1840 to generate I and Q baseband signals. The I and Q baseband signals are amplified by AMPs 1842(1), 1842(2) and further filtered by low-pass filters 1844(1), 1844(2) to obtain I and Q analog input signals that are provided to data processor 1806. In this example, data processor 1806 includes analog-to-digital converters (ADCs) 1846(1), 1846(2) for converting the analog input signals into digital signals for further processing by data processor 1806.

[0146] exist Figure 18 In wireless communication device 1800, TX LO signal generator 1822 generates I and Q TX LO signals for upconversion, while RX LO signal generator 1840 generates I and Q RX LO signals for downconversion. Each LO signal is a periodic signal with a specific fundamental frequency. TX phase-locked loop (PLL) circuit 1848 receives timing information from data processor 1806 and generates control signals for adjusting the frequency and / or phase of the TX LO signal from TX LO signal generator 1822. Similarly, RX PLL circuit 1850 receives timing information from data processor 1806 and generates control signals for adjusting the frequency and / or phase of the RX LO signal from RX LO signal generator 1840.

[0147] In some implementations, filters 1826 and 1836 may also include vertically coupled components as described herein. Figure 18As can be seen in the figure, filters 1826 and 1836 can be located on the other side of the PA or LNA (e.g., along the signal path). Examples include, but are not limited to, set-top boxes, entertainment units, navigation devices, communication devices, fixed location data units, mobile location data units, global positioning system (GPS) devices, mobile phones, cellular phones, smart phones, Session Initiation Protocol (SIP) phones, tablet devices, phablets, servers, computers, portable computers, mobile computing devices, wearable computing devices (e.g., smart watches, health or fitness trackers, glasses, smart glasses, augmented reality (AR) glasses, etc.), desktop computers, personal digital assistants (PDAs), monitors, computer monitors, televisions, tuners, radio units, satellite radio units, music players, digital music players, portable music players, digital video players, video players, digital video disc (DVD) players, portable digital video players, automobiles, vehicle components (such as vehicle head units), avionics systems, drones, and multirotor helicopters.

[0148] The various operations of the methods described above may be performed by any suitable unit capable of performing the corresponding functions. The unit may include various hardware and / or software components and / or modules, including but not limited to circuits, application specific integrated circuits (ASICs) or processors.

[0149] By way of aspect, any combination of elements described herein or any part of elements or elements can be implemented as a "processing system" including one or more processors. Aspects of processor include microprocessors, microcontrollers, graphics processing units (GPUs), central processing units (CPUs), application processors, digital signal processors (DSPs), reduced instruction set computing (RISC) processors, system on chip (SoCs), baseband processors, field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gating logic, discrete hardware circuits, and other suitable hardware configured to perform the various functions described throughout this disclosure. One or more processors in a processing system can execute software. Software should be broadly interpreted as meaning instructions, instruction sets, codes, code segments, program codes, programs, subroutines, software components, applications, software applications, software packages, routines, subroutines, objects, executable programs, threads in execution, processes (procedures), functions, etc., regardless of whether they are referred to as software, firmware, middleware, microcodes, hardware description languages, or other names.

[0150] Therefore, in one or more aspect embodiments, the functions or circuit system blocks described can be implemented with hardware, software, or any combination thereof. If implemented with software, the functions can be stored on a computer-readable medium or encoded as one or more instructions or codes on a computer-readable medium. Computer-readable media include computer storage media. The storage medium can be any available medium that can be accessed by a computer. By way of aspect and not limitation, such computer-readable media may include random access memory (RAM), read-only memory (ROM), electrically erasable programmable ROM (EEPROM), optical disk storage, magnetic disk storage, other magnetic storage devices, a combination of computer-readable media of the aforementioned types, or any other medium that can be used to store computer-executable code that can be accessed by a computer in the form of instructions or data structures. In some aspects, the components described using the circuit system can be implemented by hardware, software, or any combination thereof.

[0151] Illustrative aspects of the disclosure include:

[0152] Aspect 1A. A radio frequency (RF) filter comprising: a piezoelectric substrate having a first piezoelectric surface and a second piezoelectric surface opposite to the first piezoelectric surface; a first electroacoustic resonator comprising a first interdigital transducer (IDT) disposed above the first piezoelectric surface of the piezoelectric substrate; and a second electroacoustic resonator comprising a second IDT disposed above the second piezoelectric surface of the piezoelectric substrate; wherein the second electroacoustic resonator is electrically coupled to the first electroacoustic resonator in series or in parallel.

[0153] Aspect 1B. A radio frequency (RF) filter comprising: a piezoelectric substrate having a first piezoelectric surface and a second piezoelectric surface opposite to the first piezoelectric surface; a first electroacoustic resonator comprising a first interdigital transducer (IDT) formed on or above the first piezoelectric surface of the piezoelectric substrate; and a second electroacoustic resonator comprising a second IDT formed on or above the second piezoelectric surface of the piezoelectric substrate; wherein the second electroacoustic resonator is electrically coupled to the first electroacoustic resonator in series or in parallel.

[0154] Aspect 2. The RF filter according to aspect 1, wherein a thickness of the piezoelectric substrate is less than 20 times a minimum value of a pitch of the first IDT and a pitch of the second IDT.

[0155] Aspect 3. The RF filter according to aspect 2, wherein a thickness of the piezoelectric substrate is greater than 0.1 times the minimum value of the pitch of the first IDT and the pitch of the second IDT.

[0156] Aspect 4. The RF filter according to any one of aspects 1 to 3, wherein the piezoelectric substrate includes a first piezoelectric layer, and the first piezoelectric layer includes the first surface.

[0157] Aspect 5. An RF filter according to any one of Aspects 1 to 4, wherein the first piezoelectric layer further includes the second surface; and wherein the thickness of the first piezoelectric layer is between 0.4 times the minimum value of the pitch of the first IDT and the pitch of the second IDT and 2 times the minimum value of the pitch of the first IDT and the pitch of the second IDT.

[0158] Aspect 6. An RF filter according to any one of Aspects 1 to 5, wherein the piezoelectric substrate further comprises: a second piezoelectric layer including the second surface; and a spacer layer located between the first piezoelectric layer and the second piezoelectric layer and in contact with the first piezoelectric layer and the second piezoelectric layer.

[0159] Aspect 7. The RF filter according to any one of aspects 1 to 6, wherein a thickness of the piezoelectric substrate is less than 20 times a minimum value of a pitch of the first IDT and a pitch of the second IDT.

[0160] Aspect 8. The RF filter according to any one of aspects 6 to 7, wherein a thickness of the spacer layer is less than 10 times a minimum value of a pitch of the first IDT and a pitch of the second IDT.

[0161] Aspect 9. The RF filter according to any one of aspects 1 to 8, wherein the first piezoelectric layer and the second piezoelectric layer are made of the same piezoelectric material.

[0162] Aspect 10. The RF filter according to any one of aspects 6 to 9, wherein a thickness of the spacer layer is greater than 10 times a maximum of a pitch of the first IDT and a pitch of the second IDT.

[0163] Aspect 11. The RF filter according to aspect 10, wherein a thickness of the spacer layer is less than 1.2 times the minimum value of the pitch of the first IDT and the pitch of the second IDT.

[0164] Aspect 12. The RF filter according to any one of aspects 1 to 11, further comprising a third electroacoustic resonator comprising a third IDT formed in the spacer layer over a surface of the first piezoelectric layer opposite to the first surface.

[0165] Aspect 13. The RF filter according to aspect 12, further comprising a fourth electroacoustic resonator comprising a fourth IDT formed in the spacer layer over a surface of the second piezoelectric layer opposite to the second surface.

[0166] Aspect 14. An RF filter according to Aspect 13, wherein the thickness of the second piezoelectric layer is between 0.4 times the minimum value of the pitch of the second IDT and the pitch of the fourth IDT and 2 times the minimum value of the pitch of the second IDT and the pitch of the fourth IDT.

[0167] Aspect 15. An RF filter according to any one of Aspects 1 to 14, wherein the thickness of the first piezoelectric layer is between 0.4 times the minimum value of the pitch of the first IDT and the pitch of the third IDT and 2 times the minimum value of the pitch of the first IDT and the pitch of the third IDT.

[0168] Aspect 16. The RF filter according to any one of aspects 1 to 15, wherein the spacer layer comprises a dielectric material.

[0169] Aspect 17. The RF filter according to any one of Aspects 1 to 16 further includes a silicon substrate, wherein the silicon substrate has a cavity formed in a portion of the surface of the silicon substrate, and wherein the second piezoelectric surface of the piezoelectric substrate shares a boundary with the surface of the silicon substrate, and the boundary is aligned so that the second IDT fits within the cavity without contacting the substrate.

[0170] Aspect 18. The RF filter according to any one of Aspects 1 to 17 further includes: a plurality of spacers located on the first piezoelectric surface of the piezoelectric substrate; and a cap mounted on the plurality of spacers so that the first IDT is located in the gap between the first piezoelectric surface of the piezoelectric substrate and the cap.

[0171] Aspect 19. The RF filter according to any one of aspects 1 to 18, wherein the first electroacoustic resonator and the second electroacoustic resonator are part of a ladder filter.

[0172] Aspect 20. The RF filter according to aspect 19, wherein the RF filter is integrated into an RF front-end circuit of a transceiver.

[0173] Aspect 21. The RF filter according to any one of aspects 1 to 20, wherein a filter characteristic of the RF filter is based on electroacoustic coupling between the first electroacoustic resonator and the second electroacoustic resonator through the piezoelectric substrate.

[0174] Aspect 22. An RF filter according to any one of Aspects 1 to 21, wherein the first IDT and the second IDT overlap in a vertical direction so that the area including the first IDT on the first piezoelectric surface overlaps with the area including the second IDT on the second piezoelectric surface across the vertical projection of the piezoelectric substrate.

[0175] Aspect 23. An RF filter according to any one of Aspects 1 to 21, wherein the first IDT and the second IDT do not overlap in the vertical direction, so that a vertical projection of the first IDT across the piezoelectric substrate does not overlap with an area on the second piezoelectric surface including the second IDT.

[0176] Aspect 24. The RF filter according to any one of Aspects 1 to 23 further includes: an antenna; and a processing circuit system, wherein the antenna and the processing circuit system are communicatively coupled via the RF filter, and wherein the RF filter is configured to filter RF signals traveling between the antenna and the processing circuit system.

[0177] Aspect 25. The RF filter according to any one of aspects 1 to 24, wherein a first resonance value for the first electroacoustic resonator and a second resonance value for the second electroacoustic resonator depend on a coupling factor between the first resonator and the second resonator.

[0178] Aspect 26. The RF filter according to aspect 25, wherein the coupling factor has a value according to any aspect described herein.

[0179] Aspect 27. The RF filter according to aspect 25, wherein the coupling factor is based at least in part on a distance between the first surface and the second surface of the piezoelectric substrate, a pitch of the first IDT, and a pitch of the second IDT.

[0180] Aspect 28. An RF filter according to any one of Aspects 25 to 27, wherein the distance between the first surface and the second surface of the piezoelectric substrate is the thickness of the piezoelectric substrate, and wherein the thickness of the piezoelectric substrate is between 0.4 times the pitch of the first IDT and 2 times the pitch of the first IDT.

[0181] Aspect 29. The RF filter according to any one of aspects 25 to 28, wherein a thickness of the piezoelectric substrate is between 0.1 times and 20 times the pitch of the first IDT.

[0182] Aspect 30. An RF filter according to any one of Aspects 25 to 29, wherein the piezoelectric substrate includes: a first piezoelectric layer including the first surface; a second piezoelectric layer including the second surface; and a spacer layer located between the first piezoelectric layer and the second piezoelectric layer, wherein the spacer layer shares a first boundary with the first piezoelectric layer at a first inner surface, and wherein the spacer layer shares a second boundary with the second piezoelectric layer at a second inner surface.

[0183] Aspect 31. An RF filter according to any one of Aspects 25 to 30, wherein the thickness of the piezoelectric substrate is the sum of the thickness of the first piezoelectric layer, the thickness of the second piezoelectric layer, and the thickness of the spacer layer, and wherein the thickness of the piezoelectric substrate is between 0.1 times the pitch of the second IDT and 20 times the pitch of the second IDT.

[0184] Aspect 32. The RF filter according to any one of aspects 26 to 31, further comprising a third electroacoustic resonator comprising a third IDT formed within the spacer layer at the first boundary.

[0185] Aspect 33. The RF filter according to any one of aspects 26 to 32, further comprising a fourth electroacoustic resonator comprising a fourth IDT formed within the spacer layer at the second boundary.

[0186] Aspect 34. The RF filter according to any one of aspects 26 to 33, wherein the thickness of the first piezoelectric layer is between 0.1 times and 20 times the pitch of the first IDT.

[0187] Aspect 35. The RF filter according to any one of aspects 26 to 34, wherein the thickness of the second piezoelectric layer is between 0.1 times and 20 times the pitch of the second IDT.

[0188] Aspect 36. The RF filter according to any one of aspects 26 to 35, wherein a thickness of the spacer layer is greater than 10 times a pitch of the first IDT or 10 times a pitch of the second IDT.

[0189] Aspect 37. The RF filter according to any one of aspects 26 to 36, wherein the thickness of the spacer layer is between 0.1 times the pitch of the first IDT and 10 times the pitch of the first IDT.

[0190] Aspect 38. An RF filter according to any one of Aspects 26 to 37, wherein the first resonance value for the first electroacoustic resonator and the third resonance value for the third electroacoustic resonator depend on a first coupling factor between the first resonator and the third resonator; wherein the second resonance value for the second electroacoustic resonator and the fourth resonance value for the fourth electroacoustic resonator depend on a second coupling factor between the second resonator and the fourth resonator.

[0191] Aspect 39. An RF filter according to any one of Aspects 26 to 38, wherein the thickness of the first piezoelectric layer is between 0.4 times the pitch of the first IDT and 2 times the pitch of the first IDT; wherein the thickness of the second piezoelectric layer is between 0.4 times the pitch of the second IDT and 2 times the pitch of the second IDT; and wherein the thickness of the spacer layer is between 0.2 times the pitch of the first IDT and 1.2 times the pitch of the first IDT.

[0192] Aspect 40. An RF filter according to any one of Aspects 26 to 39, wherein a corresponding resonance value for each of the first electro-acoustic resonator, the second electro-acoustic resonator, the third electro-acoustic resonator, and the fourth electro-acoustic resonator depends on a corresponding coupling value for each other of the first electro-acoustic resonator, the second electro-acoustic resonator, the third electro-acoustic resonator, and the fourth electro-acoustic resonator.

[0193] Aspect 41. The RF filter of any one of aspects 1 to 40, wherein the spacer layer comprises a dielectric material.

[0194] Aspect 42. The RF filter according to any one of Aspects 1 to 41 further includes a silicon substrate having a first surface, wherein the silicon substrate includes a cavity formed in a portion of the first surface of the silicon substrate, and wherein the second surface of the piezoelectric substrate shares a boundary with the first surface, and the boundary is aligned so that the second IDT fits within the cavity without contacting the silicon substrate.

[0195] Aspect 43. The RF filter according to any one of Aspects 1 to 42 further includes: a plurality of spacers located on the first surface of the piezoelectric substrate; and a glass cap mounted on the plurality of spacers so that the first IDT is located in the gap between the first surface of the piezoelectric substrate and the glass cap.

[0196] Aspect 44. The RF filter according to any one of aspects 1 to 43, wherein the first electroacoustic resonator and the second electroacoustic resonator are part of a radio frequency (RF) ladder filter.

[0197] Aspect 45: An RF front-end circuit, comprising the RF filter according to any one of aspects 1 to 44, wherein the RF filter is integrated into the RF front-end circuit of a transceiver.

[0198] Aspect 46. An RF filter according to any one of clauses 1 to 45, wherein the RF filter is integrated into a device selected from the group consisting of: a set-top box; an entertainment unit; a navigation device; a communication device; a fixed location data unit; a mobile location data unit; a global positioning system (GPS) device; a mobile phone; a cellular phone; a smartphone; a Session Initiation Protocol (SIP) phone; a tablet device; a tablet phone; a server; a computer; a portable computer; a mobile computing device; a wearable computing device; a desktop computer; a personal digital assistant (PDA); a monitor; a computer monitor; a television; a tuner; a radio unit; a satellite radio unit; a music player; a digital music player; a portable music player; a digital video player; a video player; a digital video disc (DVD) player; a portable digital video player; an automobile; a vehicle component; an avionics system; an unmanned aerial vehicle (UAV); and a multirotor helicopter.

[0199] Aspect 47. An acoustic wave (AW) filter, comprising: a piezoelectric substrate, comprising: a first piezoelectric layer having a first piezoelectric surface and a second piezoelectric surface opposite to the first piezoelectric surface; a second piezoelectric layer having a third piezoelectric surface and a fourth piezoelectric surface opposite to the third piezoelectric surface; and a spacer layer between the first piezoelectric layer and the second piezoelectric layer, wherein the second piezoelectric surface is opposite to the third piezoelectric surface across the spacer layer; a first interdigital transducer (IDT) formed above the first piezoelectric surface of the first piezoelectric layer; and a second IDT formed above the second piezoelectric surface of the first piezoelectric layer; a third IDT formed above the third piezoelectric surface of the second piezoelectric layer; and a fourth IDT formed above the fourth piezoelectric surface of the second piezoelectric layer.

[0200] Aspect 48. The AW filter of aspect 47, wherein the spacer layer comprises a dielectric support structure for the air gap.

[0201] Aspect 49. An AW filter according to any one of Aspects 47 to 48, wherein the first filter characteristic of the AW filter is based on the electroacoustic coupling between the first IDT and the second IDT across the first piezoelectric layer, and wherein the second filter characteristic of the AW filter is based on the electroacoustic coupling between the third IDT and the fourth IDT across the second piezoelectric layer.

[0202] Aspect 50: An AW filter according to any of aspects 47 to 49 according to any vertically coupled IDT structure described herein.

[0203] Aspect 51. A method for manufacturing an acoustic wave (AW) filter package, the method comprising: creating one or more vias through a piezoelectric substrate, wherein the piezoelectric substrate has a first piezoelectric surface and a second piezoelectric surface opposite the first surface; using the one or more vias to manufacture one or more conductive vias from the first piezoelectric surface to the second piezoelectric surface; manufacturing a first acoustic layer above the first piezoelectric surface of the piezoelectric substrate, wherein the first acoustic layer includes one or more first interdigital transducers (IDTs) and one or more connections from the one or more first IDTs to the one or more conductive vias; using a resist layer to manufacture one or more conductive vias on the first piezoelectric surface of the piezoelectric substrate depositing one or more spacers above the piezoelectric substrate to protect the one or more first IDTs; bonding the one or more spacers to a silicon substrate to mount the piezoelectric substrate above the silicon substrate using the one or more spacers; thinning the piezoelectric substrate to a selected thickness by removing material from the second piezoelectric surface of the piezoelectric substrate; and fabricating a second acoustic layer above the second piezoelectric surface of the piezoelectric substrate, wherein the second acoustic layer includes one or more second IDTs connected to the one or more first IDTs via the one or more conductive vias, and wherein the one or more first IDTs and the one or more second IDTs are provided as part of a radio frequency filter circuit.

[0204] Aspect 52. The method according to aspect 51, wherein a projection of the one or more first IDTs from the first piezoelectric surface onto the second piezoelectric surface in a vertical direction does not overlap with the one or more second IDTs.

[0205] Aspect 53. A method according to any one of Aspects 51 to 52, wherein the filter characteristics of the AW filter package filter are based on electroacoustic coupling between the one or more first IDTs and the one or more second IDTs through the piezoelectric substrate; and wherein the electroacoustic coupling through the piezoelectric substrate is based on overlap between the one or more first IDTs and the one or more second IDTs in a vertical direction across the piezoelectric substrate.

[0206] Aspect 54. The method of aspect 51, performed in conjunction with fabrication of any of the vertically coupled IDT structures described herein.

[0207] Aspect 55. A storage medium comprising instructions that, when executed by processing circuitry of a device, cause the device to perform operations according to any of the above aspects.

[0208] Aspect 56. A method for filtering a signal when using an RF or AW filter according to any aspect described.

[0209] Aspect 57. An apparatus comprising means for filtering a signal according to any of the above aspects.

[0210] The phrase "coupled to" and the term "coupled" refer to any component that is directly or indirectly physically connected to another component and / or any component that is in direct or indirect communication with another component (e.g., connected to another component via a wired or wireless connection and / or other suitable communication interface). Generally, where there are operations illustrated in the figures, those operations may have corresponding counterpart functional unit components with similar numbering.

[0211] As used herein, the term "determine" encompasses a wide variety of actions. For example, "determine" may include calculating, computing, processing, deriving, investigating, searching (e.g., searching in a table, database, or another data structure), ascertaining, and the like. Furthermore, "determine" may include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory), and the like. Furthermore, "determine" may include resolving, selecting, choosing, establishing, and the like.

[0212] It is to be understood that the claims are not limited to the precise configuration and components shown above. Various modifications, changes and variations may be made in the arrangement, operation and details of the methods and apparatus described above without departing from the scope of the claims.

Claims

1. A radio frequency (RF) filter comprising: a piezoelectric substrate having a first piezoelectric surface and a second piezoelectric surface opposite to the first piezoelectric surface; a first electroacoustic resonator comprising a first interdigital transducer (IDT) disposed over the first piezoelectric surface of the piezoelectric substrate; as well as a second electroacoustic resonator including a second IDT disposed over the second piezoelectric surface of the piezoelectric substrate; The second electroacoustic resonator is electrically coupled to the first electroacoustic resonator in series or in parallel.

2. The RF filter according to claim 1, wherein The thickness of the piezoelectric substrate is less than 20 times a minimum value of a pitch of the first IDT and a pitch of the second IDT.

3. The RF filter according to claim 2, wherein The thickness of the piezoelectric substrate is greater than 0.1 times the minimum value of the pitch of the first IDT and the pitch of the second IDT.

4. The RF filter according to claim 1, wherein The piezoelectric substrate includes a first piezoelectric layer including the first surface.

5. The RF filter according to claim 4, wherein The first piezoelectric layer further includes the second surface; and The thickness of the first piezoelectric layer is between 0.4 times the minimum value of the pitch of the first IDT and the pitch of the second IDT and 2 times the minimum value of the pitch of the first IDT and the pitch of the second IDT.

6. The RF filter according to claim 4, wherein The piezoelectric substrate further includes: a second piezoelectric layer comprising the second surface; and A spacer layer is located between the first piezoelectric layer and the second piezoelectric layer and contacts the first piezoelectric layer and the second piezoelectric layer.

7. The RF filter according to claim 6, wherein The thickness of the piezoelectric substrate is less than 20 times a minimum value of a pitch of the first IDT and a pitch of the second IDT. 8 . The RF filter according to claim 6 , further comprising a third electroacoustic resonator including a third IDT formed within the spacer layer on a surface of the first piezoelectric layer opposite to the first surface. 9 . The RF filter according to claim 8 , further comprising a fourth electroacoustic resonator including a fourth IDT formed within the spacer layer on a surface of the second piezoelectric layer opposite to the second surface.

10. The RF filter according to claim 8, wherein The thickness of the first piezoelectric layer is between 0.4 times a minimum value of the pitch of the first IDT and the pitch of the third IDT and 2 times the minimum value of the pitch of the first IDT and the pitch of the third IDT.

11. The RF filter according to claim 9, wherein The thickness of the second piezoelectric layer is between 0.4 times a minimum value of the pitch of the second IDT and the pitch of the fourth IDT and 2 times the minimum value of the pitch of the second IDT and the pitch of the fourth IDT.

12. The RF filter according to claim 7, wherein The thickness of the spacer layer is less than 10 times the minimum value of the pitch of the first IDT and the pitch of the second IDT.

13. The RF filter according to claim 7, wherein The thickness of the spacer layer is greater than 10 times a maximum value of a pitch of the first IDT and a pitch of the second IDT.

14. The RF filter according to claim 7, in, The thickness of the spacer layer is less than 1.2 times the minimum value of the pitch of the first IDT and the pitch of the second IDT.

15. The RF filter according to claim 6, wherein The spacer layer includes a dielectric material.

16. The RF filter according to claim 12, wherein The first piezoelectric layer and the second piezoelectric layer are made of the same piezoelectric material.

17. The RF filter according to claim 1, further comprising a silicon substrate, wherein The silicon substrate has a cavity formed in a portion of a surface of the silicon substrate, and wherein the second piezoelectric surface of the piezoelectric substrate shares a boundary with the surface of the silicon substrate, the boundary being aligned such that the second IDT fits within the cavity without contacting the substrate.

18. The RF filter according to claim 17, further comprising: a plurality of spacers located on the first piezoelectric surface of the piezoelectric substrate; as well as A cap is mounted on the plurality of spacers such that the first IDT is located in a gap between the first piezoelectric surface of the piezoelectric substrate and the cap.

19. The RF filter according to claim 1, wherein The first electroacoustic resonator and the second electroacoustic resonator are part of a ladder filter.

20. The RF filter according to claim 1, wherein The RF filter is integrated into the RF front-end circuit of the transceiver.

21. The RF filter according to claim 1, wherein The filter characteristics of the RF filter are based on electroacoustic coupling between the first electroacoustic resonator and the second electroacoustic resonator through the piezoelectric substrate.

22. The RF filter according to claim 21, wherein The first IDT and the second IDT overlap in a vertical direction such that a region including the first IDT on the first piezoelectric surface overlaps a region including the second IDT on the second piezoelectric surface across a vertical projection of the piezoelectric substrate.

23. The RF filter according to claim 21, wherein The first IDT and the second IDT do not overlap in a vertical direction, such that a vertical projection of the first IDT across the piezoelectric substrate does not overlap with a region including the second IDT on the second piezoelectric surface.

24. The RF filter of claim 1 , further comprising: antenna; as well as processing circuitry, wherein the antenna and the processing circuitry are communicatively coupled via the RF filter, and wherein the RF filter is configured to filter RF signals traveling between the antenna and the processing circuitry.

25. An acoustic wave (AW) filter comprising: A piezoelectric substrate comprising: a first piezoelectric layer having a first piezoelectric surface and a second piezoelectric surface opposite to the first piezoelectric surface; a second piezoelectric layer having a third piezoelectric surface and a fourth piezoelectric surface opposite to the third piezoelectric surface; and a spacer layer between the first piezoelectric layer and the second piezoelectric layer, wherein the second piezoelectric surface is opposite the third piezoelectric surface across the spacer layer; a first interdigital transducer (IDT) disposed over the first piezoelectric surface of the first piezoelectric layer; and a second IDT disposed over the second piezoelectric surface of the first piezoelectric layer; a third IDT disposed over the third piezoelectric surface of the second piezoelectric layer; and A fourth IDT is provided above the fourth piezoelectric surface of the second piezoelectric layer.

26. The AW filter according to claim 25, wherein The spacer layer includes a dielectric material.

27. The AW filter according to claim 25, wherein A first filter characteristic of the AW filter is based on electroacoustic coupling between the first and second IDTs across the first piezoelectric layer, and wherein a second filter characteristic of the AW filter is based on electroacoustic coupling between the third and fourth IDTs across the second piezoelectric layer.

28. A method of manufacturing an acoustic wave (AW) filter package, the method comprising: creating one or more vias through a piezoelectric substrate, wherein the piezoelectric substrate has a first piezoelectric surface and a second piezoelectric surface opposite the first surface; using the one or more vias to create one or more conductive vias from the first piezoelectric surface to the second piezoelectric surface; fabricating a first acoustic layer over the first piezoelectric surface of the piezoelectric substrate, wherein the first acoustic layer includes one or more first interdigital transducers (IDTs) and one or more connections from the one or more first IDTs to the one or more conductive vias; depositing one or more spacers on the first piezoelectric surface of the piezoelectric substrate using a resist layer to protect the one or more first IDTs; bonding the one or more spacers to a silicon substrate to mount the piezoelectric substrate on the silicon substrate using the one or more spacers; thinning the piezoelectric substrate to a selected thickness by removing material from the second piezoelectric surface of the piezoelectric substrate; and A second acoustic layer is fabricated over the second piezoelectric surface of the piezoelectric substrate, wherein the second acoustic layer includes one or more second IDTs connected to the one or more first IDTs via the one or more conductive vias, and wherein the one or more first IDTs and the one or more second IDTs are provided as part of a radio frequency filter circuit.

29. The method according to claim 28, wherein A projection of the one or more first IDTs from the first piezoelectric surface onto the second piezoelectric surface in a vertical direction does not overlap with the one or more second IDTs.

30. The method according to claim 29, wherein The filter characteristics of the AW filter package filter are based on electroacoustic coupling between the one or more first IDTs and the one or more second IDTs through the piezoelectric substrate; and The electroacoustic coupling through the piezoelectric substrate is based on an overlap between the one or more first IDTs and the one or more second IDTs in a vertical direction across the piezoelectric substrate.

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